NL2030254B1 - Chrysanthemum harvesting assembly - Google Patents

Abstract

The present invention relates to a harvesting assembly for harvesting plants, for example chrysanthemum, lisianthus or gerbera plants, growing on a bedding and through meshes in a 5 wire mesh grid in a greenhouse, comprising a cutting device, configured to cut stems of the plants underneath the wire mesh grid upon movement across the bedding, the cutting device comprising a drive motor, configured to move the cutting device across the bedding in a displacement direction, and one or more cutting elements, each configured to cut the plant stems in a respective row of plants parallel to the displacement direction. 10 The harvesting assembly further comprises an alignment device, which is arranged on the cutting device and which comprises one or more sets of guiding elements, each set of guiding elements defining a guiding passage. Each set of guiding elements projects, seen in a transverse horizontal direction, perpendicular to the displacement direction, above a respective cutting element and each of the guiding 15 passages is configured to receive plant stems from a respective row of plants and to horizontally align the plant stems in the transverse horizontal direction, i.e. to align the plant stems centrally in the meshes.

Description

P35367NLOO/TRE

Title: Chrysanthemum harvesting assembly

Field of the invention

The present invention relates to a harvesting assembly for harvesting plants, for example chrysanthemum, lisianthus or gerbera plants, growing on a bedding and through meshes in a wire mesh grid in a greenhouse.

The present invention further relates to an alignment device of such a harvesting assembly, to a handling device of such a harvesting assembly and to a method of harvesting plants.

State of the art

The present invention is aimed at harvesting crops that grow in a bedding in greenhouses, like for example chrysanthemum, lisianthus and gerbera plants. In the greenhouse, wire mesh grids are supported above the bedding, so that each plant can grow into a respective mesh of the wire mesh grid for support during growth. The wire mesh grid is used to support the plants and to prevent the plants from falling over.

During harvesting, a mobile cutting device is used underneath the wire mesh grid for cutting the stems of the plants. The cutting device is supported on the bedding and has its own propulsion means to move underneath the wire mesh grid. A human worker then typically grabs one or more of the cut plants from above the wire mesh grid, to pull the plants upwards through the wire mesh grid and to lay the plants on a conveyor belt for further processing at a centralized facility in the greenhouse. This upward pulling needs to be done as much vertical as possible, to avoid that the plant stems scrape along wires of the wire mesh grid and that leaves of the plants are ripped-off. This could otherwise reduce the weight of the plant stem and, in accordance, the selling price.

Examples of mobile cutting devices are disclosed in prior art publications NL 1005719

C1 and NL 1034385 C2, which both comprise a set of driven wheels at a rear end, configured to move the cutting device across the bed. At an opposed end, i.e. at a frontal end, the cutting devices comprise cutting elements for cutting the stems of the plants. In between the cutting elements and the wheels, the cutting devices comprise a number of buffer spaces, corresponding to a number of rows of plant stems that can be cut. The buffer spaces are configured to store a plurality of cut stems, for example between two clamping belts.

Furthermore, the cutting devices comprise guidance elements at the front end, configured to project in between rows of plants and to guide the cutting device passively upon movement across the bedding, upon interaction between the guidance elements and the plant stems.

These known cutting devices are only usable in combination with human workers to pull the plants up through the wire mesh grid. However, they have the drawback that they cannot be combined with robotic handling devices to autonomously remove the plants.

In the past, several attempts were made to harvest these plants automatically, for example in EP 1 621 061 A1 and NL 2022411 B1. However, these systems had the drawback that the plant stems were difficult to grip with the handling device, since their position inside the wire mesh grid was defined too inaccurate. This could for example result from an uneven bedding or a deformed wire mesh grid, so that the position of the plant stems differed somewhat for each of the meshes.

As a result, the handling device often failed to grip a plant stem, erroneously gripped two or more plant stems simultaneously and/or erroneously gripped plants stems in a different mesh.

Object of the invention

It is therefore an object of the invention to provide a harvesting assembly that enables automated handling of plant stems after cutting, or at least to provide an alternative handling device.

Detailed description

The present invention provides a harvesting assembly for harvesting plants, for example chrysanthemum, lisianthus or gerbera plants, growing on a bedding and through meshes in a wire mesh grid in a greenhouse, comprising a cutting device, configured to cut stems of the plants underneath the wire mesh grid upon movement across the bedding, the cutting device comprising a drive motor, configured to move the cutting device across the bedding in a displacement direction, and one or more cutting elements, each configured to cut the plant stems in a respective row of plants parallel to the displacement direction, characterized in that, the harvesting assembly further comprises an alignment device, which is arranged on the cutting device and which comprises one or more sets of guiding elements, each set of guiding elements defining a guiding passage, wherein each set of guiding elements is arranged vertically higher than the cutting elements, and wherein each of the guiding passages is configured to receive plant stems from a respective row of plants and to horizontally align the plant stems in a transverse horizontal direction, perpendicular to the displacement direction, i.e. to align the plant stems centrally in the meshes.

The present invention relies on the concept that the plant stems do not come to lean against the wire mesh grid, i.e. before, during and after cutting thereof with the cutting device.

Instead, the alignment device is configured to sidewardly support the plant stems, i.e. before and after cutting thereof, by means of the guiding elements. With the harvesting assembly according to the present invention, the position of the plant stems in the wire mesh grid can be defined more accurately after cutting, thereby allowing for automated handling of the plant stems.

According to the present invention, a harvesting assembly is provided that is at least configured to cut stems of plants that grow in a bedding. Such a bedding may consist of soil and may be located in a greenhouse, or in other indoor farming complexes. Typical crops that grow in such a manner are chrysanthemum, lisianthus or gerbera plants, which may be harvested beneficially by means of the present harvesting assembly, although the harvesting assembly may also be configured to harvest crops of other types.

Alternatively, the present harvesting assembly may be configured to cut stems of plants that grow in a different manner, for example in individual plant pots and/or plants that grown on trays.

These plants grow though individual meshes of a wire mesh grid and are thereby aligned in rows, extending over the bedding in a direction parallel to the displacement direction. This grid is supported above the bedding, for example from a ceiling of the greenhouse, and may be configured to be raised during growth of the plants, preferably in accordance with the changing height of the plants during growth.

The cutting device of the harvesting assembly is adapted to be moved across the bedding and for example comprises two wheels, driven by the drive motor, to roll across the bedding. The cutting device may be configured to roll in the displacement direction by passively following rows of the plants with guidance elements that are configured to project in between rows. Additionally, the cutting device may comprise a differential in between the drive motor and the wheels, facilitating steering of the cutting device under influence of the guidance elements.

The cutting device may have a width in the transverse horizontal direction, i.e. perpendicular to the displacement direction of the cutting device, to span across one or more rows of plants. Preferably, the cutting device may span across half of the width of the bedding, so that plants in a single bedding can be cut with two cutting devices operating side- to-side. Alternatively, the invention may also envisage a cutting device that spans over the entire width of the bedding. The cutting device may comprise a number of cutting elements corresponding to the number of plant rows it spans across over its width, so that each cutting element is configured to cut plant stems in a respective row of plants.

Different from existing cutting devices, is the present harvesting assembly provided with the alignment device, which is configured to prevent plant stems from leaning against wires of the wire mesh grid, i.e. after cutting of the stems. The alignment device is arranged on the cutting device, for example mounted on top of it, so that it is arranged at least partially above the cutting elements thereof. As such, the alignment device may be configured to support the plant stems at a point located higher than where the plants stems are cut with the cutting device, but lower than where the plants would otherwise lean against the wire mesh grid.

The alignment device comprises the guiding elements, which may be provided as a pair, to form a set. The alignment device comprises a number of sets of guiding elements that corresponds to the number of cutting elements in the cutting device, i.e. to the number of rows of plants that are spanned by the cutting device. In between the guiding elements of each of the sets, a respective guiding passage is defined, so that the number of guiding passages corresponds to the number of cutting elements as well.

The guiding passages are located vertically higher than the cutting elements and each of the guiding passages projects over a respective cutting element, which implies that a distinct guiding passage is provided above each of the cutting elements. Upon movement of the cutting device in the displacement direction, the cutting elements thus repeatedly encounter plant stems that are to be cut, whereas these plants stems also come to project in the guiding passages.

The opposed guiding elements forming the respective guiding passages sidewardly confine the plant stems, seen in the transverse horizontal direction, so that the plant stems come to lean against the guiding elements, i.e. after cutting, instead of against the wires of the wire mesh grid.

For example, the guiding elements may be embodied as smooth tubes or rods, which extend in a direction having at least a component in the displacement direction. The smooth surface of such elements may be beneficial in reducing damaging of the plant stems, since the plant stems may smoothly slide along them when they are pulled upward through the wire mesh grid.

As a result, the harvesting device according to the present invention may hold the plant stems centrally in the meshes of the wire mesh grid after cutting. The term aligned centrally not necessarily implies that the plant stems are held exactly in the middle of the meshes, although such alignment may be beneficial. Instead, it is preferably to be interpreted broadly, in that the plant stems are spaced at a distance from the wires of the wire mesh grid and that they become aligned such, not to come leaning against wires of the wire mesh grid.

As such, the scraping of the plant stems along the wires of the wire mesh grid and the ripping of leaves can be minimized, due to the preferred lack of contact between the wires and the plant stems, resulting in less damage to the plants.

In an embodiment of the harvesting assembly, each of the guiding passages further projects horizontally in front of the respective cutting elements, seen in the displacement direction.

As such, the plants are allowed to lean against the guiding elements in the guiding passages even before they are cut by the cutting elements. The cutting device, upon moving in the displacement direction, thus first moves the guiding elements around the plant stems, i.e. before reaching these plant stems with its cutting elements.

This embodiment provides the benefit that the sideward position of the plant stems inside the meshes of the wire mesh grid can be assured before the plant stems are cut and that, in accordance, the plant stems can be gripped before they are cut, so that gripping of the plants can be carried out more reliably.

Additionally or alternatively, the guiding elements may extend behind the cutting elements, seen in the displacement direction. This may contribute in holding the stems centrally in the meshes of the wire mesh grid also after cutting.

In an embodiment of the harvesting assembly, the guiding elements of each set of guiding elements are spaced from each other at a passage width, each two adjacent sets of guiding elements are spaced at a horizontal spacing from each other, for example corresponding to a mesh width of the wire mesh grid, and the passage width is less than 60%, for example less than 50%, preferably less than 40% smaller than the horizontal spacing.

According to this embodiment, the plant stems are guided centrally by the guiding elements in the transverse direction. In particular, they are sidewardly confined from a position defined by the mesh width to a position defined by the passage width. The passage width is smaller than the mesh width, i.e. amounting to no more than 60% of the mesh width, which implies that the position of the plant stem become define more accurately. Preferably, however, the passage width is no larger than 50% of the mesh width, to further increase the confining of the plant stems by the alignment device.

The sets of guiding elements are spaced at the horizontal spacing, which is equal to the spacing between adjacent guiding passages. This spacing preferably corresponds to the mesh width, so that all guiding passages overlap with respective meshes in the wire mesh grid and the respective rows of plants.

In an embodiment, the mesh width may for example be 125 mm and the horizontal spacing between sets of guiding elements is 125 mm as well. In this embodiment, the passage width may be in the range between 50 mm and 75 mm.

In an embodiment of the harvesting assembly, the guiding passages taper to further horizontally align the plant stems in the transverse horizontal direction upon movement of the cutting device.

According to this embodiment, the guiding passages are relative wide at an entrance where the plants stems enter during movement of the cutting device. Upon further movement of the cutting device, the passages taper inwardly further, i.e. the guiding elements of each set becomes located closer to each other, so that the plant stems become confined to a larger extent.

For example, the guiding elements may taper from a width corresponding to the mesh width to the eventual passage width described above. The taper of the passages may thus be more than 40%, for example more than 50%, preferably more than 60%. As such, the plant stems can be smoothly guided in the transverse direction from a position anywhere inside the meshes of the wire mesh grid to a more confined position in the guiding passages, i.e. in between the guiding elements.

In an embodiment of the harvesting assembly, the alignment device comprises at least one friction element, such as a brush, in each of the guiding passages, configured to exert a friction force on the plant stems during movement of the cutting device.

Each of the passages may be provided with a respective friction element, for example provided at the entrances of the guiding passages. The friction elements are configured to exert frictional forces on the plant stems during movement of the cutting device in the displacement direction, so that the plant stems are forced in the displacement direction by the friction elements.

The friction elements, in particular when provided at the entrance of the guiding passages, are configured to press the plant stems against the wire mesh grid in the displacement direction, until the reactive force of the wire mesh grid against the plant stems is sufficient to overcome the frictional forces.

The friction elements are thereby configured to push away a next line of plant stems in the displacement direction, after a first line of plant stems is already received in the respective guiding passages. This implies that the first line of plant stems is aligned centrally in their meshes and that the plant stems in the next line are pushed away from the plant stems in the first line.

Accordingly, the first line of plant stems can be gripped, whereas the next line is pushed away, in order not to hinder the gripping of the plants in the first line. The plant stems in the next line are thus pushed away and configured to be released by the friction elements after the plants in the first line are removed after cutting. The friction elements can thereby be designed to be able to exert a limited maximum friction force on the plant stems, to avoid unnecessary damage to the plant stems.

Preferably, the frictional elements are located in front of the cutting elements, seen in the displacement direction, so that the plant stems are pushed away by the friction elements first and that the plant stems are cut afterwards.

The friction elements may be embodied as brushes, which may be attached to each of the guiding elements of each set and which may face into the respective guiding passage from the opposed guiding elements. Brushes may be beneficial, as they are able to reduce damaging of the plant stems.

In an embodiment, the harvesting assembly further comprises: - an actuator device, connected to the guiding elements and configured to horizontally move the guiding elements at least partly in the transverse horizontal direction relative to the cutting device, - a sensor device, associated with the guiding elements and configured to emit a position sensor signal representative for a position of the guiding elements relative to the wire mesh grid, - a control unit, associated with the actuator device and the sensor device, configured to control the actuator device on the basis of the position sensor signal, to align the plant stems centrally in their respective meshes.

The guiding elements are thus configured to be moved sidewardly at least partially. For example, a rear end of the guiding elements may be moved in the transverse direction by the actuator device, whereas a front end of the guiding elements may remain stationary.

The guiding elements may each be hingedly connected to the cutting device at the front ends, so that the guiding elements can be rotated relative to the cutting device about a vertical axis or an axis at least having a vertical component. At the front end, the guiding elements of each set may be located relatively far away from each other.

The rear ends of the guiding elements may be hingedly connected to a common transverse rod, which extends in the transverse direction. At the rear end, the guiding elements of each set may be spaced at the passage width. The transverse rod may be connected to the actuator device, so that a movement of the transverse rod in the transverse direction is translated into sideward movement of the rear ends of all guiding elements.

The sensor device may be associated with the guiding elements, which may imply that the sensor is device attached to the guiding elements and configured to move along with the movable guiding elements. However, the association may also imply that the sensor device is not directly attached to the guiding elements, for example being located remotely, but nonetheless configured to detect the guiding elements relative to the wire mesh grid, in order to determine their relative position.

The actuator device and the sensor device may form part of the alignment device and may thereto be arranged on the cutting device, in order to travel along in the displacement direction. As such, the sensor device may be configured to move along with the rear ends of the guiding elements, in order to track a relative position between the guiding elements and the wire mesh grid. The sensor device may for example be attached to the transverse rod, so that the relative position between the sensor device and the wire mesh grid corresponds to the relative position between the guiding elements, in particular the guiding passages in between them, and the wire mesh grid.

Alternatively, the sensor device may for example be separate from the cutting device, for example part of a handling device above the wire mesh grid. In such an embodiment, the sensor device may be configured to track a position of the guiding elements from a distance above the wire mesh grid.

The control unit is operatively connected to the sensor device and the actuator device, and is configured to control the actuator device in response to the position sensor signal obtained from the sensor device. The control unit is configured to control the actuator device in a manner, such that the guiding passages remain aligned with the meshes of the wire mesh grid, preferably irrespective of sideward movements of the cutting device underneath the wire mesh grid. The movable guiding elements are thus configured to compensate for sideward deviations between the cutting device and the wire mesh grid.

In this way, the sideward position of the plant stems in the guiding passages, i.e. at the rear ends of the guiding elements, can be controlled so that the plant stems are moved sidewardly by means of the moved guiding elements and that the plant stems are moved to become aligned centrally in the meshes of the wire mesh grid.

Preferably, the actuator device is configured to move the guiding elements, i.e. the rear ends of the guiding elements, for example by means of the transverse rod, over a distance of at least 50% of the passage width, for example over a distance of more than 100% of the passage width. For example, the actuator device is configured to move the guiding elements over a maximum distance of 75 mm, so that even a large deviation between the cutting device and the wire mesh grid can be compensated by the movable guiding elements.

The actuator device may be configured to move each of the guiding elements, i.e. the rear ends of the guiding elements, individually and relative to each other. The actuator device may thereto be configured to move the two respective guiding elements of each of the guiding passages away from each other before a plant stem is received in the guiding passages. The guiding passages are thereby relatively wide when the plant stem is received. Accordingly, the actuator device may be configured to move the two respective guiding elements of each of the guiding passages towards each other after a plant stem is received in the guiding passages, in order to make the guiding passages more narrow and to sidewardly confine the plant stems.

Furthermore, the actuator device may be configured to move the two respective guiding elements of each of the guiding passages away from each other again after the plant stems are gripped. The guiding elements can thereby be located away from the plant stems when the plants are removed upwardly out of the wire mesh grid. As such, damaging of the plant stems by the guiding elements may be avoided substantially.

In a further embodiment of the harvesting assembly, the control unit is further associated with the drive motor of the cutting device and further configured to control the drive motor on the basis of the position sensor signal.

According to this embodiment, the control unit is further configured to control the movements of the cutting device in the displacement direction on the basis of its position relative to the wire mesh grid. For example, the control unit may be configured to control the drive motor for moving the cutting device until a wire of the wire mesh grid is detected by the sensor device. At this point, movements of the cutting device may be inhibited until the control unit is configured to re-activate the drive motor again. For example, this re-activation may comprise a signal that a certain lines of plant stems has been cut and pulled out of the wire mesh grid, so that the cutting device can be moved again to cut a subsequent line of plant stems.

In a further or alternative embodiment of the harvesting assembly, the sensor device is configured to project towards the wire mesh grid, and the sensor device is configured to detect: - longitudinal wires of the wire mesh grid, which extend parallel to the displacement direction, and/or - transverse wires of the wire mesh grid, which extend parallel to the transverse horizontal direction.

The position sensor signal obtained by the sensor device according to this embodiment may comprise information about the position of the sensor device relative to the longitudinal wires of the wire mesh grid and to the transverse wires of the wire mesh grid.

The longitudinal wires of the wire mesh grid extend parallel to the displacement direction. Accordingly, a position sensor signal based on an interaction of the sensor device with a longitudinal wire of the wire mesh grid may be representative of a relative position between the sensor device, and thus of the guiding elements, and the wire mesh grid in the transverse direction.

The transverse wires of the wire mesh grid extend parallel to the transverse horizontal direction, so that a position sensor signal based on an interaction of the sensor device with a transverse wire of the wire mesh grid may be representative of a relative position between the cutting device and the wire mesh grid in the displacement direction.

The sensor device may comprise one or more sensors that are configured to detect both longitudinal wires and transverse wires of the wire mesh grid. Preferably, the sensor device comprises two sensors that are offset relative to each other in the displacement direction and/or in the transverse direction. In this way, the offset may contribute in detecting an accurate position of the sensor device relative to the wire mesh grid.

For example, the sensors may be spaced in the transverse direction over a distance larger than the mesh width, so that both sensors are each configured to detect an opposed longitudinal wire of a single mesh. Accordingly, the sensors of the sensor device may both detect deviations to the right, i.e. by a left one of the sensors, and to the left, i.e. by a right one of the sensors, between the sensor device and the mesh.

Similarly, the sensors may be spaced in the displacement direction over a distance equal to the mesh width, so that both sensors are configured to detect both opposed transverse wires of a single mesh. Hence, a frontal one of the sensors may be configured to detect a front one of the transverse wires of the mesh and a rear one of the sensors may be configured to detect a rear one of the transverse wires of the mesh.

A first one of the sensors may be located at the front, seen in the displacement direction, and to the right, seen in the transverse direction. A second one of the sensors may be located at the rear, seen in the displacement direction, and to the left, seen in the transverse direction. If a wire is detected by the first sensor only, the detected wire may concern the right longitudinal wire and the control unit may control the actuator device to move the guiding elements to the right until the right longitudinal wire is not detected anymore. Similarly, if a wire is detected by the second sensor only, the detected wire may concern the left longitudinal wire and the control unit may control the actuator device to move the guiding elements to the left until the left longitudinal wire is not detected anymore. If no wires are detected, the control unit may be configured to activate the drive unit to move the cutting device in the displacement direction. If, however, wires are detected by both sensors, these wires must be the transverse wires and the control unit may be configured to de- activate the drive unit to stop movements of the cutting device in the displacement direction and to allow the cut plant stems to be moved out of the wire mesh grid.

In a further embodiment of the harvesting assembly, the alignment device further comprises a spring-loaded skid system, which is configured to be biased in the upward direction from the cutting device, and the sensor device is attached to the skid system and configured to be pressed upwardly against the wire mesh grid by the skid system.

The skid system may be attached to the guiding elements, for example to the transverse rod underneath the guiding elements, with a bottom part. The sensor device may be attached to a top part of the skid system, thereby facing towards the wire mesh grid. The skid system comprises a spring device, configured to upwardly move the top part of the skid system away from the bottom part, so that the sensor device is upwardly pressed against the wire mesh grid.

The spring-loaded pressing of the sensor device against the wire mesh grid may safeguard that the sensor device is able to accurately follow the contours of the wire mesh grid, for example also if the wire mesh grid has been damaged or deformed.

The top part of the skid system with the sensor device may be configured to slide along a bottom surface of the wire mesh grid and may comprise at least one ramp, facing to the front, seen in the displacement direction. The ramp may be configured to overcome downward disturbances in the flat bottom surface of the wire mesh grid, for example to slide underneath transverse frame elements that support the wire mesh grid.

In a further embodiment, the alignment device may comprise two spring-loaded skid systems, which are configured to bias at least one sensor against the wire mesh grid independent of each other. The provision of more than a single skid system may allow for more accurate detection of wires of the wire mesh grid with the sensors, because the sensor can be pressed against the wire mesh grid independent of each other.

In an embodiment of the harvesting assembly, the sensor device comprises one or more, for example two or more sensors, preferably two or more capacitive sensors.

The capacitive sensors may be efficient to detect the wires of the wire mesh grid, since those wires are typically made of metallic materials.

However, the sensor device may comprise other types of sensors, like vision systems, for example camera’s. Vision sensors may, for example, be beneficial in case the sensor device is located above the wire mesh grid, for example when it is attached to the handling device. Then, the positions of the guiding elements are determined from above the wire mesh grid, being imaged by the vision sensors, after which a signal is transmitted to the cutting device to control the actuator device.

The benefit of having two sensors is described above, namely to be able to detect both deviations between the sensor device and the wire mesh grid in the transverse direction and to detect transverse wires of the wire mesh grid.

Alternatively, the sensor device comprises four sensors, in particular four capacitive sensors. Two of the sensors may be attached to a first spring-loaded skid system and two other ones of the sensors may be attached to a second spring-loaded skid system.

Compared to a sensor device with two sensors, the two further sensors according to this embodiment provide the benefit of having redundancy and an improved reliability in detecting wires of the wire mesh grid. The redundancy allows reliable operation even if one or more of the wires were to be damaged or missing, so that even in the absence of a wire in front of one of the sensors, another wire may be present in front of another one of the sensors.

In an embodiment, the harvesting assembly further comprises a handling device, for example a robotic arm, configured to grip the plant stems, to upwardly pull the plants out of the meshes and to discharge the plants for further processing.

The handling device is preferably located above the wire mesh grid, so that the plants can be pulled out of the meshes in the wire mesh grid in the upward direction and that the plants can be discharged on a conveyor belt system for further processing. The conveyor belt systems may be the same as the ones used in existing greenhouses, which are configured to bring harvested plants, for example bundles thereof, to a central location in the greenhouse for sorting, cutting and packing. Alternatively, a dedicated conveyor belt system may be envisaged for use with automated handling devices.

In an embodiment, the harvesting assembly may comprise a paddle conveyor, on which the handling device is configured to discharge the plants that are pulled out of the wire mesh grid. As such, each of the plant stems may end up in a separate cavity of the paddle conveyor, so that bundles of plants may be made by discharging plants from multiple cavities on top of each other on a subsequent conveyor belt.

The handling device may be a collaborative robot, i.e. a cobot, to facilitate implementation in an existing harvesting system and to prevent hindrance for human workers in the proximity of the handling device.

The harvesting assembly may comprise a single handling device and multiple, for example two, cutting devices underneath it. The single handling device is thereby configured to discharge all plants cut by both cutting devices. For example, the handling device may have a capacity of two times the capacity of a single cutting device, or the handling device may alternately discharge plants cut by a first one of the cutting devices and a second one of the cutting devices.

Alternatively, the present harvesting assembly may comprise a single handling device and a single cutting device, which is preferably configured to cut plant stems over the entire width of the bedding.

Furthermore, the harvesting assembly may comprise multiple handling devices and multiple cutting devices, preferably the same number of handling devices and cutting devices.

The multiple handling devices may share a single conveyor belt system for discharging harvested plants from all of the handling devices. Preferably, the handling devices are adjusted to each other, to alternatingly discharge harvested plants on the conveyor belt system.

The handling device may be configured to be suspended above the plants and the wire mesh grid, for example from a ceiling of the greenhouse, such as from heating tubes suspended at the ceiling of the greenhouse. In this way, the handling device does not need to be supported on the bedding or on the wire mesh grid, thus avoiding disturbances, i.e. deformations, of the wire mesh grid that could otherwise follow from heavy loads acting thereon.

In a further embodiment of the harvesting assembly, the handling device is configured to be moved in the displacement direction, preferably in conjunction with the cutting device.

The movement of the handling device may be effected along the greenhouse ceiling, for example along the heating tubes. The handling device is thereby configured to be moved towards a next line if the plants in a certain line have been pulled out of the wire mesh grid.

Preferably, this movement is carried out in conjunction with movement of the cutting device, so that the handling device is moved after the cutting device has been moved in the displacement direction towards a subsequent line of plants.

Preferably, the handling device is configured to transmit a signal towards the cutting device after it has gripped the plant stems and/or when it has removed a line of plants from the wire mesh grid. This signal may be received by the control unit of the cutting device and the control unit may control the drive motor to move the cutting device underneath the wire mesh grid.

When the signal is sent after the plant stems have been gripped by the handling device, the cutting device may be controlled to drive in the displacement direction to cut these plants stems. Here, the cutting of the plant stems thus only takes place after the plants are gripped by the handling device.

If, alternatively, the signal is sent after the plants have been removed, a next line of plants can be cut by the cutting device. Only after cutting, this line is gripped by the handling device. The cut plant stems are then still held centrally in the meshes by the guiding elements, so that the cut plant stems can be gripped by the handling device reliably.

The movements of the handling device during a certain handling cycle may be controlled on the basis of its movements during a previous handling cycle. For example,

position coordinates of the handling device during the handling cycle may be based on earlier position coordinates that are super positioned with the displacement of the entire handling device, i.e. upon displacement in the displacement direction. As such, the controlling of the handling device may be reliable, whilst still at relatively low computing requirements, thus reducing hardware requirements and costs. Furthermore, such controlling of the handling device may reduce the solution space, thereby offering an improved reliability.

Optionally, the handling device may comprise a feedback device, configured to contribute in controlling the positioning of the handling device. However, the degree of controlling by the feedback device may be relatively low, following from the superimposed primary controlling on the basis of previous coordinates. The low degree of feedback controlling improves the speed at which the handling device can be controlled, thus increasing productivity of the harvesting assembly.

In a further or alternative embodiment of the harvesting assembly, the handling device comprises a gripper unit, with which the handling device is configured to grip the plant stems, and the gripper unit comprises one or more clamping elements, for example corresponding to the number of cutting elements of the cutting device, for clamping the plant stems.

The clamping elements of the gripper unit are each configured to be moved between an opened configuration, each allowing entry of a plant stem, for example in between two opposed jaws of the clamping elements, and a closed position, in which the jaws are moved towards each other to clamp the plant stems in between them.

In the opened configuration, the clamping elements, e.g. the jaws thereof, may be spaced at a distance corresponding to the passage width that is defined between the guiding elements of the alignment device, to ensure that the confined plant stems in the guiding passages can be reliably gripped by the clamping elements. The spacing of the clamping elements may be approximately equal to 50% of the mesh width.

The number of clamping elements may correspond to the number of cutting elements of the cutting device, so that the handling device can remove all plant stems cut by the cutting device in a single handling cycle. Alternatively, the gripper unit may comprise more clamping elements that the number of cutting elements, for example two times the number of cutting elements, so that the handling device can remove plant stems cut by two cutting devices in a single handling cycle.

The handling device, and in particular the gripper unit may be force-controlled, which implies that the clamping elements are able to exert a clamping force that cannot exceed a certain predetermined threshold clamping force. As such, it may be prevented that the plant stems are damaged by excessive clamping forces. The gripper unit may thereto comprise pneumatic clamping elements, which rely on air pressure during operation and which have a predetermined threshold clamping force that is determined by a maximum air pressure acting on the clamping elements. In addition, the clamping elements may comprise a padding, for example a soft and deformable padding, at the inside of the clamping elements facing the plant stems, to further reduce damaging of the plant stems.

In a further embodiment of the harvesting assembly, the clamping elements each have a tapered shape, to further horizontally align the plant stems in the transverse horizontal direction upon gripping by the gripper unit.

According to this embodiment, the clamping elements, i.e. the opposed jaws thereof, are relative wide at an entrance where the plants stems enter during gipping by the gripping unit. Upon further movement of the gripping unit, the clamping elements taper inwardly, i.e. the jaws of clamping element, become located closer to each other in their opened position, so that the plant stems become confined.

In an embodiment, the handling device is further configured to be controlled on the basis of a height signal, representative for a height of the handling device, for example relative to the cutting device or the wire mesh grid. Disturbances in height of the handling device could, for example, result from bending of the heating tubes from which the handling device is suspended and could reduce the accuracy of the handling device. On the basis of the height signal, these disturbances can be compensated and the handling device is able to operate more reliably.

Especially where the handling device is force-controlled, the height signal may only need to represent a rough estimate of the height of the handling device. A fine adjustment of the height of the handling device, i.e. of the gripper unit, may be done on the basis of force control, offering a more robust control of the handling device.

Alternatively or additionally, the gripper unit of the handling device may comprise a heating tube fork, having a shape corresponding to heating tubes that extend over the wire mesh grid. During gripping of plant stems, the gripper unit may be positioned such, that the fork is positioned over the heating tube, so that a vertical position of the gripper unit on the wire mesh grid is safeguarded. After positioning the gripper unit on the heating tube of the wire mesh grid, the gripper unit may be slid forward over the heating tubes in the displacement direction to let the plant stems enter the clamping elements of the gripper unit.

The positioning of the gripper unit on the heating tubes, i.e. with the fork, may be controlled on the basis of its positioning during a previous handling cycle as well.

Furthermore, the gripper unit may comprise a force sensor in the heating tube fork to detect a force at which the gripper unit is pressed onto the heating tube. The force sensor is configured to emit a force sensor signal, representing the force value at which the gripper unit is pressed onto the heating tube. The control unit may be configured to control the handling device on the basis of the force sensor signal.

According to a second aspect, the present invention provides an alignment device of the harvesting assembly disclosed herein, preferably recited in the claims. The alignment device according to the second aspect of the present invention may comprise one or more of the features and/or one or more of the benefits disclosed in relation to the harvesting assembly according to the present invention.

According to a third aspect, the present invention provides a handling device of the harvesting assembly disclosed herein, preferably recited in the claims. The handling device according to the third aspect of the present invention may comprise one or more of the features and/or one or more of the benefits disclosed in relation to the harvesting assembly according to the present invention.

The present invention further provides a method of harvesting plants, for example chrysanthemum, lisianthus or gerbera plants, growing on a bedding and through meshes in a wire mesh grid in a greenhouse, the method comprising the steps of: - aligning stems of the plants centrally in the meshes, - cutting the plant stems underneath the wire mesh grid, - gripping the plant stems, and - removing the plant stems out of the meshes.

The method according to the present invention may be carried out by means of the harvesting assembly according to the present invention. The method according to the present invention may further comprise one or more of the features and/or one or more of the benefits disclosed in relation to the harvesting assembly according to the present invention

The present method relies on the concept that the plant stems do not come to lean against the wire mesh grid after cutting thereof. Instead, the alignment of the plant stems is able to act as a sideward support for the plant stems, i.e. before and after cutting thereof. As a result, the plant stems may be held centrally in the meshes of the wire mesh grid after cutting.

The term aligned centrally not necessarily implies that the plant stems are held exactly in the middle of the meshes, although such alignment may be beneficial. Instead, it is preferably to be interpreted broadly, in that the plant stems are spaced at a distance from the wires of the wire mesh grid and that they become aligned such, not to come leaning against wires of the wire mesh grid.

During the removing of the plant stems out of the wire mesh grid, i.e. upon pulling the plants upward through the meshes, the scraping of the plant stems along the wires of the wire mesh grid and the ripping of leaves can be minimized, due to the preferred lack of contact between the wires and the plant stems, resulting in less damage to the plants.

The gripping of the plant stems may be carried out autonomously, for example by means of a handling device, like a robotic arm. Alternatively, however, the gripping may be carried out manually by a human worker. It was found by the inventors that even when the plant stems are gripped and removed manually, the aligning would still offer a beneficial effect in reducing damaging of the plant stems, i.e. in avoiding scraping of the plant stems against the wires of the wire mesh grid.

In an embodiment of the method, the gripping of the plant stems takes place prior to the cutting of the plant stems.

According to this embodiment of the method, the plant stems are gripped before they are cut. During gripping, the plant stems are thus connected to the ground and aligned centrally in the meshes. In particular, the plants may be allowed to lean against guiding elements of an alignment device when they are gripped.

This embodiment of the method provides the benefit that the sideward position of the plant stems inside the meshes of the wire mesh grid can be assured before the plant stems are cut and that, in accordance, the plant stems can be gripped before they are cut, so that gripping of the plants can be carried out more reliably.

Brief description of drawings

Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

Figure 1 schematically depicts a perspective view on an embodiment of the harvesting assembly according to the present invention,

Figure 2 schematically depicts a top view on the cutting device of the harvesting apparatus and a wire mesh grid,

Figure 3 depicts a side view on the cutting device of figure 2,

Figure 4 depicts a top view on the cutting device of figure 2, without the wire mesh grid,

Figures 5a and 5b schematically depict movements of the guiding elements of a cutting device,

Figures 6a and 6b schematically depict mutual relative movements between the guiding elements of another embodiment of a cutting device,

Figure 7 depicts a close-up top view on the sensor device of the cutting device, and

Figures 8a and 8b depict detailed views on the gripper unit of the handling device.

Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

Detailed description of embodiments

Figure 1 schematically depicts an embodiment of the harvesting assembly according to the present invention, to which is referred with reference numeral 1. The harvesting assembly 1 is configured to harvest plants 100, for example chrysanthemum, lisianthus or gerbera plants, that grow on a bedding 200 and through meshes 202 in a wire mesh grid 201 in a greenhouse. The plants 100 typically have a plant stem 101, which protrudes through a mesh 202 of the wire mesh grid 201, and a flower 102 at a top end of the plant stem 101. The plants 100 are aligned in rows and the wire mesh grid 201 is supported above the bedding 200, for example from a ceiling of the greenhouse. The wire mesh grid 201 is configured to be raised during growth of the plants 100, in particular in accordance with the changing height of the plants 100 during growth.

The harvesting assembly 1 comprises a cutting device 10, which is configured to be moved by a drive motor across the bedding 200 in a displacement direction D. The cutting device 10 is configured to cut the plant stems 101 in a respective row of plants 100 parallel to the displacement direction D by means of a plurality of cutting elements 12. The cutting device 10 comprises two wheels 13, which are driven by the drive motor, to roll across the bedding 200. The cutting device 10 is configured to roll in the displacement direction D by passively following rows of the plants with guidance elements 11 that are configured to project in between the rows and to steer the cutting device 10 upon interaction with the plants 100.

The harvesting assembly 1 further comprises a handling device 50, which is presently embodied as a cobot, i.e. a robotic arm 50, configured to grip the plant stems 101, to upwardly pull the plants 100 out of the meshes 202 and to discharge the plants 100 for further processing. The handling device 50 is located above the wire mesh grid 201, so that the plants 100 can be pulled out of the meshes 202 in the wire mesh grid 201 in an upward direction and that the plants 100 can be discharged on a conveyor belt system for further processing.

The handling device 50 is suspended above the plants 100 and the wire mesh grid 201, in particular from heating tubes suspended at the ceiling of the greenhouse. In this way, the handling device 50 does not need to be supported on the bedding 200 or on the wire mesh grid 201, thus avoiding deformations of the wire mesh grid 201 that could otherwise follow from heavy loads acting thereon.

According to the present embodiment, the harvesting assembly 1 comprises a single handling device 50 and two cutting devices 10 underneath it. The single handling device 50 is thereby configured to discharge all plants 100 cut by both cutting devices 10. The handling device 50 thereby has a capacity of two times the capacity of a single cutting device 10. The cutting device 10 has a width in a transverse horizontal direction T, perpendicular to the displacement direction D of the cutting device 10, to span across half of the width of the bedding 200 and multiple rows of plants 100.

The present harvesting assembly 1 is provided with an alignment device 20, which is configured to prevent plant stems 101 from leaning against wires 205, 206 of the wire mesh grid 201. The alignment device 20 is mounted on top of the cutting device 10, so that it is arranged at least partially above the cutting elements 12. The alignment device 20 is configured to sidewardly support the plant stems 101 at a point located higher than where the plants stems 101 are cut with the cutting device 12, but lower than where the plants 100 would otherwise lean against the wire mesh grid 201.

The alignment device 20 comprises guiding elements 21, which are provided as a pair, to form a set. The alignment device 20 comprises a number of sets of guiding elements 21 that corresponds to the number of cutting elements 12 in the cutting device 10 and to the number of rows of plants 100 that are spanned by the cutting device 10. In between the guiding elements 21 of each of the sets, a respective guiding passage 22 is defined, so that the number of guiding passages 22 corresponds to the number of cutting elements 12 as well.

The guiding passages 22 are located vertically higher than the cutting elements 12 and each of the guiding passages 22 projects over a respective cutting element 12, as is best shown in figure 4. This implies that a distinct guiding passage 22 is provided above each of the cutting elements 12. Upon movement of the cutting device 10 in the displacement direction D, the cutting elements 12 thus repeatedly encounter plant stems 101 that are to be cut, whereas these plants stems 101 also come to project in the guiding passages 22.

Each of the guiding passages 22 further projects horizontally in front of the respective cutting elements 12, seen in the displacement direction D. As such, the plants 100 are allowed to lean against the guiding elements 21 in the guiding passages 22 even before they are cut by the cutting elements 12. The cutting device 10, upon moving in the displacement direction D, thus first moves the guiding elements 21 around the plant stems 101, before reaching these plant stems 101 with its cutting elements 21.

The opposed guiding elements 21 forming the respective guiding passages 22 sidewardly confine the plant stems 101, seen in the transverse horizontal direction T, so that the plant stems 101 come to lean against the guiding elements 21 after cutting, instead of against the wires 205, 206 of the wire mesh grid 201.

The guiding elements 21 are embodied as smooth tubes, which extend in a direction having at least a component in the displacement direction D. The smooth surface of such guiding elements 21 is beneficial in reducing damaging of the plant stems 101, since the plant stems 101 can smoothly slide along them when they are pulled upward through the wire mesh grid 201.

The guiding elements 21 of each set of guiding elements 21 are spaced from each other at a passage width PW and each two adjacent sets of guiding elements 21 are spaced at a horizontal spacing HS from each other. The horizontal spacing HS corresponds to a mesh width MW of the wire mesh grid 201 and the passage width PW is smaller than the mesh width MW. In the embodiment shown in figures 1 — 4, the passage width PW amounts approximately 50% of the mesh width MW, to increase the confining of the plant stems 101 by the alignment device 20. With the horizontal spacing HS corresponding to the mesh width

MW, all guiding passages 22 overlap with respective meshes 202 in the wire mesh grid 201 and the respective rows of plants 100.

Furthermore, the guiding passages 22 taper to further horizontally align the plant stems 101 in the transverse horizontal direction T upon movement of the cutting device 10. The guiding passages 22 are relative wide at an entrance where the plants stems 101 enter during movement of the cutting device 10 and, upon further movement of the cutting device 10, the passages 22 taper inwardly further. The guiding elements 21 of each set become located closer to each other, so that the plant stems 101 become confined to a larger extent during movement of the cutting device 10.

The guiding elements 21 taper from a width corresponding to the mesh width MW to the eventual passage width PW described above, of approximately 50% of the mesh width MW. It is furthermore best shown in figures 3 and 4 that the guiding elements 21 upwardly slope in a vertical direction V and that rear ends of the guiding elements 21 do not taper, but are rather aligned parallel to each other at a rear end of the alignment device 20, spaced at the passage width PW.

The guiding elements 21 from neighbouring sets of guiding elements 21, i.e. a right guiding element 21 of a left set and a left guiding element 21 of a right set, coincide at the front of the cutting device 10, i.e. seen along the displacement direction D. Both guiding elements 21 are jointly connected to a pivot joint 23, which pivotally connects the guiding elements 21 to the guidance elements 11 of the cutting device 10.

The guiding elements 21 are configured to be moved sidewardly, in the transverse direction T, at least partially. The guiding elements 21 are hingedly connected to the guidance elements 11 of the cutting device 10 at the front end thereof, so that the guiding elements 21 can be rotated relative to the cutting device 10 about a vertical axis V. According to the present embodiment, the rear ends of the guiding elements 21 may be moved in the transverse direction T, whereas a front end of the guiding elements 21 remains stationary.

The rear ends of the guiding elements 21 are hingedly connected to a common transverse rod 24, which extends in the transverse direction T. At the rear end, the guiding elements 21 of each set are spaced at the passage width PW.

The harvesting assembly 1 comprises an actuator device 40, which is connected to the transverse rod 24 and which is thus indirectly connected to the guiding elements 21. The actuator device 40 is configured to horizontally move the transverse rod 24 and the rear ends of the guiding elements 21 in the transverse horizontal direction T relative to the cutting device 10. A movement of the transverse rod 24 in the transverse direction T is thereby translated into sideward movement of the rear ends of all guiding elements 21.

The harvesting assembly 1 further comprises a sensor device 30, which is associated with the guiding elements 21 and configured to emit a position sensor signal representative for a position of the guiding elements 21 relative to the wire mesh grid 201. In the present embodiment, the sensor device 30 is attached to the guiding elements 21 via the transverse rod 30 and thereby configured to move along with the movable guiding elements 21.

The harvesting assembly 1 further comprises two spring-loaded skid systems 31, which are each configured to be biased in an upward vertical direction V from the cutting device 10.

The sensor device 30 is attached to the skid systems 31 and configured to be pressed upwardly against the wire mesh grid 201 by the skid system 31.

Each of the skid systems 31 comprises a respective spring-loaded arm 31’, 31”, which are pivotally attached to the transverse rod 24 with respective bottom ends thereof. The skid systems 31 further each comprise a skid 32’, 32” at an upper end of the spring-loaded arms 31, 317.

The sensor device 30 comprises sensors, which are received in the skids 32’, 32” and which thereby face towards the wire mesh grid 201. The spring-loaded arms 31’, 31” are configured to upwardly move the skids 32’, 32” away from the cutting device 10, so that the sensor device 30 is upwardly pressed against the wire mesh grid 201. The top parts of the skids 32’, 32” with the sensor device 30 are configured to slide along a bottom surface of the wire mesh grid 201 and each comprise a ramp 33’, 33”, facing to the front, seen in the displacement direction D. The ramps 33’, 33” are configured to overcome downward disturbances in the flat bottom surface of the wire mesh grid 201, enabling the skids 32’, 32” to slide underneath transverse frame elements 204 that support the wire mesh grid 201.

Alternatively, however, the sensor device may not be directly attached to the guiding elements, but for example being located remotely. Nonetheless, the sensor device is always configured to detect the guiding elements relative to the wire mesh grid, in order to determine their relative position.

The actuator device 40 and the sensor device 30 form part of the alignment device 20 and are thereto be arranged on the cutting device 10, in order to travel along in the displacement direction D. As such, the sensor device 30 is configured to move along with the rear ends of the guiding elements 21, in order to track a relative position between the guiding elements 21 and the wire mesh grid 201, in particular to track a relative position between the guiding passages 22 and the wire mesh grid 201.

The harvesting assembly 1 comprises a control unit 45, which is associated with the actuator device 40 and the sensor device 30 and which is configured to control the actuator device 40 on the basis of the position sensor signal, to align the plant stems 101 centrally in their respective meshes 202. The control unit 45 is configured to control the actuator device 40 in a manner, such that the guiding passages 22 remain aligned with the meshes 202 of the wire mesh grid 201, irrespective of sideward movements of the cutting device 10 underneath the wire mesh grid 201. The movable guiding elements 21 are thereby configured to compensate for sideward deviations between the cutting device 10 and the wire mesh grid 201.

The actuator device 40 is configured to move the transverse rod 24 with the rear ends of the guiding elements 21 over a distance of at least 50% of the passage width PW. This movement is shown in figures 5a and 5b.

In figure 5a, the transverse rod 24 is arranged in a central position, so that the guiding elements 21 within each set of guiding elements 21 are substantial mirror images with respect to each other. Accordingly, the guiding passages 22 project underneath the respective meshes 202, so that the plant stems 101 are aligned centrally the meshes 202.

In figure Sb, the transverse rod 24 is moved towards the left, as is indicated by means of the arrows. The transverse rod 24 has been moved by the actuator device 40, since the cutting device 10 is offset to the right, relative to the wire mesh grid 201, compared to figure 5a. The movement of the guiding elements 21 towards the left ensures that the plant stems 101 still become aligned centrally in the meshes 202.

Figures 6a and 6b depict another embodiment of a cutting device 60, in which the actuator device is configured to move the rear ends of each of the guiding elements 71 individually and relative to each other. The actuator device is thereto configured to move the two respective guiding elements 71 of each of the guiding passages 72 away from each other before a plant 100 is received in the guiding passages 72, in particular received at the rear ends thereof.

The guiding passages 72 are thereby relatively wide when the plant stem 101 is received, as is shown in figure 6a. Accordingly, the actuator device is configured to move the two respective guiding elements 71 of each of the guiding passages 72 towards each other after a plant stem 101 is received in the guiding passages 72. This situation is shown in figure

6b and allows the guiding passages 72 to be made more narrow and to sidewardly confine the plant stems 101.

The actuator device is further configured to move the two respective guiding elements 71 of each of the guiding passages 72 away from each other again, i.e. into the situation shown in figure Ga, after the plant stems 101 are gripped and removed by the handling device. The guiding elements 71 can thereby be located away from the plant stems 101 when the plants 100 are removed upwardly out of the wire mesh grid 201.

It is further visible in figure 5 and 6 that the cutting device 10, 60 comprises two friction elements 25, 75, each embodied as a brush 25, 75, in each of the guiding passages 22, 72.

The brushes 25, 75 of each of the guiding passages 22, 72 face each other, to form a pair, and are together configured to exert a friction force on the plant stems 101 during movement of the cutting device 10, 60.

The brushes 25, 75 are provided at the entrances of the guiding passages 22, 72 and are configured to the force the plant stems 101 in the displacement direction D under influence of the frictional forces. The brushes 25, 75 are configured to press the plant stems 101 against the wire mesh grid 102 in the displacement direction D, until the reactive force of the wire mesh grid 201 against the plant stems 101 is sufficient to overcome the frictional forces.

Figure 7 depicts a close-up top view on the sensor device 30 of the cutting device 10 shown in figures 1 — 4, arranged underneath the wire mesh grid 201. The present embodiment of the sensor device 30 comprises four capacitive sensors 34, 35, 36, 37, which are configured to detect the wires of the wire mesh grid 201, i.e. since those wires are made of metallic materials. A first one of the sensors 34 and a second one of the sensors 35 is attached to the first spring-loaded skid system 31, i.e. to the first skid 32’, and a third one of the sensors 35 and a fourth one of the sensors 36 is attached to the second spring-loaded skid system 31, i.e. to the second skid 32”.

The multiple sensors 34, 35, 36, 37 allow for detection of deviations between the sensor device 30 and the wire mesh grid 201 both in the transverse direction T and to detect transverse wires of the wire mesh grid 201. Furthermore, the multiple sensors 34, 35, 36, 37 provide offer redundancy and an improved reliability in detecting wires of the wire mesh grid 201. The redundancy allows reliable operation even if one or more of the wires were to be damaged or missing, so that even in the absence of a wire in front of one of the sensors 34, 35, 36, 37, another wire may be present in front of another one of the sensors 34, 35, 36, 37.

In other embodiments, the sensor device may comprise other types of sensors, like vision systems, for example camera's. Vision sensors may, for example, be beneficial in case the sensor device is located above the wire mesh grid 201, for example when it is attached to the handling device 50. Then, the positions of the guiding elements are determined from above the wire mesh grid 201, being imaged by the vision sensors, after which a signal is transmitted to the cutting device to control the actuator device.

It is shown in figure 7 that he sensor device 30, in particular the sensors 34, 35, 36, 37 thereof, project towards the wire mesh grid 201. With the sensors 34, 35, 36, 37, the sensor device 30 is configured to detect longitudinal wires 205 of the wire mesh grid 201, which extend parallel to the displacement direction D. The sensors 34, 35, 36, 37 are further configured to detect transverse wires 206 of the wire mesh grid 201, which extend parallel to the transverse horizontal direction T.

The position sensor signal obtained by the sensor device 30 according to this embodiment comprises information about the position of the sensor device 30 relative to the longitudinal wires 205 of the wire mesh grid 201 and to the transverse wires 206 of the wire mesh grid 201. Hence, a position sensor signal based on an interaction of the sensor device 30 with a longitudinal wire 205 of the wire mesh grid 201 is representative of a relative position between the sensor device 30, and thus of the guiding elements 21, and the wire mesh grid 201 in the transverse direction T. Furthermore, a position sensor signal based on an interaction of the sensor device 30 with a transverse wire 206 of the wire mesh grid 201 is representative of a relative position between the cutting device 10 and the wire mesh grid 201 in the displacement direction D.

The sensors 34, 35, 36, 37 are spaced in the transverse direction T over a distance larger than the mesh width MW, so that two of the sensors 35,37 are configured to detect a first longitudinal wire 205 of a single mesh 202 and that two other ones of the sensors 34, 36 are configured to detect a second longitudinal wire 205 of that specific mesh 202.

Accordingly, the sensors 34, 35, 38, 37 of the sensor device 30 are configured to detect deviations to the right, i.e. by a left one of the sensors 35, 37, and to the left, i.e. by a right one of the sensors 34, 36, between the sensor device 30 and the mesh 202.

Similarly, the sensors 34, 35, 36, 37 are spaced in the displacement direction D over a distance equal to the mesh width MW, so that the sensors 34, 35, 36, 37 are configured to detect two opposed transverse wires 206 of a single mesh 202. Hence, a frontal one of the sensors 34, 35, 36, 37 is configured to detect a front one of the transverse wires 206 of the mesh 202 and a rear one of the sensors 34, 35, 36, 37 is configured to detect a rear one of the transverse wires 208 of the mesh 202.

The first sensor 34 is located at the front of the first skid 32’, seen in the displacement direction D, and to the right, seen in the transverse direction T. The second sensor 35 is located at the rear of the first skid 32°, seen in the displacement direction D, and to the left, seen in the transverse direction T. For redundancy purposes, the third sensor 36 is provided at the right front of the second skid 32” and the fourth sensor 37 is provided at the left rear of the second skid 32”.

If a wire is detected by the first sensor 34 and/or the third sensor 36 only, the detected wire may concern the right longitudinal wire 205 of a mesh 202 and the control unit 45 may control the actuator device 40 to move the guiding elements 21 to the right until the right longitudinal wire 205 is not detected anymore. The presence of both the first sensor 34 and the third sensor 36 adds redundancy to the sensor device 30, since only one of these sensors 34, 36 needs to detect a wire, so that the sensor device 30 still works properly if one of the longitudinal wires 205 is damaged or missing.

Similarly, if a wire is detected by the second sensor 35 and/or the fourth sensor 36 only, the detected wire may concern the left longitudinal wire 205 of that mesh 202 and the control unit 45 may control the actuator device 40 to move the guiding elements 21 to the left until the left longitudinal wire 205 is not detected anymore. Similarly, the presence of both the second sensor 35 and the fourth sensor 37 adds redundancy to the sensor device 30, since only one of these sensors 35, 37 needs to detect a wire, so that the sensor device 30 still works properly if one of the longitudinal wires 205 is damaged or missing.

If no wires are detected, the control unit 45 may be configured to activate the drive unit to move the cutting device 10 in the displacement direction D. If, however, wires are detected by both the first sensor 34 and the fourth sensor 37 or by both the second sensor 35 and the third sensor 36, these wires must be the transverse wires 206 and the control unit 45 may be configured to de-activate the drive unit to stop movements of the cutting device 10 in the displacement direction D and to allow the cut plant stems 101 to be moved out of the wire mesh grid 201.

The handling device 50 comprises a gripper unit 51, which is shown in figure 8a, as a top view, and in figure 8b, as front view. The handling device 50 is configured to grip the plant stems 101 with the gripper unit 51. The gripper unit 51 thereto comprises a plurality of clamping elements 52, eight in the present embodiment, corresponding to the number of cutting elements 12 of the cutting device 10. The gripper unit 51 further comprises a triangular bracket 53, with which the gripper unit 51 is attachable to the robotic arm.

The clamping elements 52 of the gripper unit 51 are each configured to be moved between an opened configuration, each allowing entry of a plant stem 10 in between two opposed jaws of the clamping elements 52, and a closed position in which the jaws are moved towards each other to clamp the plant stems 101 in between them. The clamping elements 52 each have a tapered shape, to further horizontally align the plant stems 101 in the transverse horizontal direction T upon gripping by the gripper unit 50. The opposed jaws of the clamping elements 52 are relative wide at an entrance E where the plants stems 101 enter during gipping by the gripping unit 51. Upon further movement of the gripping unit 51 in the displacement direction D, the jaws of the clamping elements 52 taper inwardly so that the plant stems 101 become confined.

In the opened configuration of the clamping elements 52, as shown in figure 8a, a spacing is defined which corresponds to the passage width PW that is defined between the guiding elements 21 of the alignment device 20, to ensure that the confined plant stems 101 in the guiding passages 22 can be reliably gripped by the clamping elements 52. The spacing of the clamping elements 52 thereby is approximately equal to 50% of the mesh width MW.

The handling device 50 is configured to be controlled on the basis of a height signal, representative for a height of the handling device 50, relative to the cutting device 10 and the wire mesh grid 201. The height signal therefore only needs to represent a rough estimate of the height of the handling device 50 and a fine adjustment of the height of the handling device 50 is done on the basis of force control.

The gripper unit 51 comprises a heating tube fork 54 that has a concave rounded shape that corresponds to the circular shape of heating tubes 207 that extend over the wire mesh grid 201. During gripping of plant stems 101, the gripper unit 51 is positioned such, that the fork 54 is positioned over the heating tube 207, so that a vertical position of the gripper unit 51 onthe wire mesh grid 201 is safeguarded. After positioning the gripper unit 51 on the heating tube 207 of the wire mesh grid 201, the gripper unit 51 may be slid forward over the heating tubes 207 in the displacement direction D to let the plant stems 101 enter the clamping elements 52 of the gripper unit 51.

The positioning of the gripper unit 51 on the heating tubes 207 with the fork 54,is controlled on the basis of its positioning during a previous handling cycle as well.

Furthermore, the gripper unit 51 comprises a force sensor 55 in the heating tube fork 54 to detect a force at which the gripper unit 51 is pressed onto the heating tube 207. The force sensor 55 is configured to emit a force sensor signal, representing the force value at which the gripper unit 51 is pressed onto the heating tube 207. The control unit 45 is configured to control the handling device 50 on the basis of the force sensor signal.

Claims (1)

CONCLUSIONS CLAIMS 1. Harvesting assembly for harvesting plants, for example chrysanthemum, lisianthus or gerbera plants, growing on a bed and through meshes in a mesh grid in a greenhouse, comprising: - a cutting device arranged to cut off plant stems below the mesh grid when moving over the bed, comprising the cutting device: . a drive motor adapted to move the cutting device across the bed in a direction of travel, and 10 . one or more cutting elements, each adapted to cut off the plant stems in a respective row of plants parallel to the direction of movement, characterized in that the harvesting assembly further comprises: - an aligning device, which is arranged on the cutting device and which contains one or more sets of guide elements wherein each set of guide elements defines a guide passage, each set of guide elements, viewed in a horizontal transverse direction, perpendicular to the direction of movement, protrudes above a respective cutting element, and each of the guide passages is adapted to receive plant stems from a respective row of plants and to align the plant stems harizontally in the horizontal transverse direction, i.e. to align the plant stems centrally in the meshes. 2. Harvesting assembly according to claim 1, wherein each of the guide passages further projects horizontally in front of the respective cutting elements, viewed in the direction of movement. 3. Harvesting assembly according to one of the preceding claims, wherein the guide elements of each set of guide elements are spaced apart by a passage width, each two adjacent sets of guide elements being spaced apart horizontally, e.g. corresponding to a mesh size of the mesh grille, and wherein the passage width is less than 60%, for example less than 50%, preferably less than 40% less than the horizontal distance. A harvesting assembly according to any one of the preceding claims, wherein the guide passages taper to further align the plant stems horizontally in the horizontal transverse direction upon movement of the cutting device. 5. Harvesting assembly according to one of the preceding claims, wherein the aligning device in each of the guide channels comprises at least one friction element, such as a brush, adapted to exert a frictional force on the plant stems during movement of the cutting device. 6. Harvesting assembly according to one of the preceding claims, further comprising: - a drive device, connected to the guide elements and adapted to move the guide elements at least partially in the horizontal transverse direction relative to the cutting device, - a sensor device, coupled to the guide elements, and arranged to transmit a position sensor signal representative of a position of the guide elements relative to the mesh grid, and - a control unit, coupled to the actuator and the sensor device, arranged to control the actuator on the basis of the position sensor signal, to control the plant stems centered in their respective meshes. 7. Harvesting assembly according to claim 6, wherein the control unit is further coupled to the drive motor of the cutting device and is further adapted to control the drive motor on the basis of the position sensor signal. 8. Harvesting assembly according to claim 6 or 7, wherein the sensor device is arranged to face the mesh grid, and wherein the sensor device is arranged to detect: - longitudinal wires of the mesh grid, which extend parallel to the direction of movement, and/or - transverse wires of the mesh grid, which extend parallel to the horizontal transverse direction. The harvesting assembly of claim 8, wherein the aligning device further comprises a spring-loaded carriage system configured to be biased upwardly from the cutting device, and wherein the sensor device is attached to the carriage system and arranged to be raised by the carriage system. pressed against the mesh grille. 10. Harvesting assembly according to one of claims 6 - 9, wherein the sensor device comprises one or more, for instance two or more sensors, preferably two or more capacitive sensors. 11. Harvesting assembly according to one of the preceding claims, further comprising: - a handling device, for instance a robot arm, adapted to grip the plant stems, to pull the plants upwards from the meshes and to discharge the plants for further processing. 12. Harvesting assembly according to claim 11, wherein the handling device is adapted to be moved in the direction of displacement, preferably together with the cutting device. 13. Harvesting assembly according to claim 11 or 12, wherein the handling device comprises a gripper unit, with which the handling device is adapted to grip the plant stems, and wherein the gripper unit comprises one or more clamping elements, for instance corresponding to the number of cutting elements of the cutting device, for clamping the plant stems. 14. Harvesting assembly according to claim 13, wherein the clamping elements each have a tapering shape, in order to further align the plant stems horizontally in the horizontal transverse direction when engaged by the gripper unit. 15. Alignment device of the harvesting assembly according to one of the preceding claims. 16. Handling device of the harvesting assembly according to any one of claims 11-14. 17. A method of harvesting plants, for example chrysanthemums, lisianthus or gerbera plants, growing on a bed and through meshes in a mesh grid in a greenhouse, the method comprising the steps of: - aligning the plant stems centrally within the meshes, - cutting off the plant stems under the gauze grid, - gripping the plant stems, and - removing the plant stems from the meshes. A method according to claim 17, wherein the plant stems are gripped prior to cutting the plant stems.