JP7722914B2 - Work management system and work management method - Google Patents

Description

The present invention relates to a work management system and a work management method.

Work machines that automatically perform planned work require a work management system to ensure that the work is carried out accurately. For example, Patent Document 1 discloses an automated driving system that causes a work vehicle to follow a planned work route in a field, comprising "a position information acquisition unit that acquires position information of the work vehicle using a satellite positioning system, a route generation unit that generates a target driving route for the work vehicle to automatically travel in the work area, and an automated driving control unit that automatically drives the work vehicle along the target driving route based on the work vehicle's position information acquired by the position information acquisition unit (abstract excerpt)."

In addition, in positioning systems that measure the position of moving objects, there is a positioning method known as RTK-GNSS (Real Time Kinematic-GNSS), which achieves high-precision positioning by correcting the position of the object using radio waves received from satellites by a reference station (fixed station) located in a known position. It is known that with RTK-GNSS, the accuracy of the object decreases as the baseline length, which is the distance between the object and the reference station, increases.

For example, Patent Document 2 discloses a positioning system that changes reference stations when the baseline length increases and the positioning accuracy using RTK-GNSS decreases. The system includes: "a server used for measuring the position of a moving object to be positioned, the server including a reference station communication unit that receives observation data generated by a plurality of reference stations located at a plurality of different known position coordinates, the reference stations receiving radio waves from artificial satellites; a correction information creation unit that creates, for each of the plurality of reference stations, positioning correction information to be used in measuring the position of the object to be positioned based on the observation data received from the reference station; an information storage unit that stores the positioning correction information for each of the plurality of reference stations; a reference station selection unit that periodically acquires approximate position information of the object to be positioned and selects one or more reference stations located near the object to be positioned based on the approximate position information of the object to be positioned; a positioning object communication unit that receives from the object observation data generated by the object to be positioned based on reception of radio waves from the artificial satellites; and a position information calculation unit (abstract excerpt) that calculates the position information of the object to be positioned based on the positioning correction information of the selected one or more reference stations and the observation data of the object to be positioned." The process of changing the reference station is generally called a handover.

In addition, in contrast to positioning methods that directly calculate position, such as RTK-GNSS, there is a method known as dead reckoning that sequentially updates position from related motion parameters such as speed, attitude, acceleration, and angular velocity (see, for example, Patent Document 3). Generally, when results cannot be obtained using RTK-GNSS, the work machine follows the target based on the position estimation results obtained using dead reckoning.

Japanese Patent Application Laid-Open No. 2021-22209 Japanese Patent Application Laid-Open No. 2021-47054 JP 2019-179421 A (Patent 06900341)

Patent Documents 1, 2, and 3 describe a work management system that allows a work machine to follow a planned work route, and if the baseline length increases and the positioning accuracy using RTK-GNSS decreases, a handover is performed while the work machine continues to follow the route based on the dead reckoning positioning results.

However, a decrease in positioning accuracy using RTK-GNSS does not necessarily mean that a handover should be performed. Positioning results using sensors such as dead reckoning have significantly lower positioning accuracy than RTK-GNSS.

In addition, because it is difficult to estimate the time required to perform a handover, if the handover takes a long time, it is expected that the work machine's following travel using dead reckoning will deviate significantly from its travel route, resulting in the need to redo work and reduced productivity.

The object of this invention is to prevent a decrease in productivity due to the need to redo work in a work management system.

One aspect of the present invention is a work management system that receives satellite signals transmitted from positioning satellites and correction information transmitted from a reference station and automatically navigates a work machine performing work at a work site along a travel route. The work management system includes: a positioning unit that performs positioning of the work machine based on the satellite signals and the correction information; a work plan storage unit that stores a work plan that describes the travel route at the work site; a threshold determination unit that determines an allowable error between the travel route and the position of the work machine; an accuracy reduction position detection unit that detects an accuracy reduction position where the positioning accuracy of the work machine has decreased based on the positioning results of the positioning unit; an accuracy recovery position prediction unit that predicts an accuracy recovery position where the positioning accuracy of the work machine will return based on the travel route and the accuracy reduction position; and a reference station change unit that calculates the predicted error that occurs on the travel route between the accuracy reduction position and the accuracy recovery position, and changes the reference station that receives the correction signal if the predicted error exceeds the allowable error.

According to one aspect of the present invention, a work management system can prevent a decrease in productivity due to work being redone.

FIG. 2 is a diagram illustrating a hardware configuration of a work management system. FIG. 2 is a block diagram showing the configuration of a load roller. FIG. 10 is a block diagram showing DR error data. FIG. 2 is a block diagram showing the configuration of a work management device. FIG. 2 is a diagram showing an example of a work plan for a work site stored in a work plan storage unit. FIG. 10 is a diagram showing variables for determining a movement route stored in a work plan storage unit. 10 is a diagram showing an example of an accuracy return position predicted by an accuracy return position prediction unit; FIG. 10 is a flowchart showing the processing of a reference station change unit. FIG. 10 is a diagram showing reference points generated on a movement path from an accuracy-decreasing position to an accuracy-recovering position. FIG. 10 is a diagram illustrating the definition of a route deviation amount. 10 is a flowchart showing the processing of the work management system. 10 is a flowchart showing a process of the work management device.

Embodiments of a work management system according to the present invention will be described below with reference to the drawings. In the description of the drawings, identical elements will be assigned the same reference numerals, and duplicate explanations will be omitted. Furthermore, the present invention is not limited to these drawings, and some components may not be used, and the components of each embodiment described below can be combined as appropriate.

The work management system 1 according to this embodiment is a system that is mounted on, for example, a work machine and moves the work machine along a planned route in an unmanned operating state (in other words, automatic operation). Here, a road roller will be used as the work machine for explanation, and therefore the work management system 1 according to this embodiment includes a road roller 2. Note that the work machine is not limited to construction machinery such as the road roller 2, and may be a work machine that moves along a planned route, such as an agricultural machine like a tractor or a transport machine like a forklift.

Figure 1 shows the hardware configuration of the work management system 1. The work management system 1 is composed of a road roller 2, a positioning satellite 4, a reference station 5, and a distribution server 9.

[Positioning satellite]
The positioning satellites 4 are artificial satellites located above the Earth, and establish a Global Navigation Satellite System (GNSS) by transmitting satellite signals 516 (in other words, radio waves) to the Earth. The GNSS is a global navigation satellite system that receives the satellite signals 516 from the positioning satellites 4 and enables a satellite to acquire its own position on the Earth. The positioning satellites 4 are artificial satellites located in plural numbers above the Earth.

[Reference station]
The reference station 5 is installed on the Earth and receives satellite signals 516 transmitted by the positioning satellites 4. The reference station 5 transmits the satellite signals 516 received from the multiple positioning satellites 4 to the distribution server 9. A plurality of reference stations 5 are installed on the Earth, and all of the reference stations 5 transmit the satellite signals 516 received from the positioning satellites 4 to the distribution server 9. The positions of all of the reference stations 5 on the Earth have been measured with high accuracy in advance, and the position information is stored in the distribution server 9.

[Distribution Server]
The distribution server 9 generates a correction signal 52 by receiving the satellite signal 516 from the reference station 5. The correction signal 52 is generated for each of the reference stations 5 that have transmitted the satellite signal 516 to the distribution server 9. The correction signal 52 includes at least the satellite signal 516 received by the reference station 5 and the position of the reference station 5 on the Earth.

The distribution server 9 is configured to be able to communicate with the road roller 2. When the distribution server 9 receives reference station selection position data 513 (described below) from the road roller 2, it transmits to the road roller 2 a correction signal 52 generated by the reference station 5 located closest to the position described in the reference station selection position data 513. In this embodiment, the reference station 5 receiving the correction signal 52 from the distribution server 9 may be referred to as the "connected reference station 5." By receiving satellite signals 516 from all reference stations 5 and distributing correction signals 52 according to the reference station selection position data 513, the distribution server 9 omits the process of determining the reference station 5 to connect to on the road roller 2 side and simplifies the function of the satellite positioning device 25.

[Road Roller]
The road roller 2 to which the work management system 1 according to this embodiment is applied is a known device that travels on its own to compact the ground, and is configured to include rollers 21, 22 that are rotatably arranged at the front and rear of a vehicle body 20. This road roller 2 is designed so that the front and rear rollers 21, 22 are driven and steered by a travel mechanism (not shown) such as a hydraulic circuit or an electric circuit built into the vehicle body 20, causing these rollers 21, 22 to rotate and the road roller 2 to move forward and backward.

Two GNSS antennas 23a and 23b are arranged on top of the vehicle body 20 to measure the position and orientation of the vehicle body 20. The GNSS antennas 23a and 23b receive satellite signals 516 from multiple positioning satellites 4 positioned above the Earth and output the received satellite signals 516 to a satellite positioning device 25 (described below). The satellite positioning device 25 calculates the road roller 2's own position on the Earth (e.g., latitude, longitude, altitude) based on the signals from the GNSS antennas 23a and 23b.

While there are various methods of satellite positioning using GNSS, this embodiment uses RTK-GNSS (Real Time Kinematic-GNSS), which can acquire its own position with high accuracy. Details regarding RTK-GNSS will be described later. The road roller 2 is equipped with a correction signal receiver 24, which receives a correction signal 52 from the distribution server 9, thereby acquiring its own position using RTK-GNSS.

In addition, the road roller 2 uses the correction signal receiver 24 to transmit reference station selection position data 513 to the distribution server 9, thereby acquiring its own position using RTK-GNSS.

Furthermore, if the positions of the GNSS antennas 23a and 23b on the vehicle body 20 are known in advance, the position of the vehicle body 20 on Earth can be determined by working backwards from the positions of the GNSS antennas 23a and 23b. Furthermore, because both GNSS antennas 23a and 23b are mounted on the vehicle body 20, the orientation of the vehicle body 20 can also be obtained. Note that in the following description, the GNSS antennas 23a and 23b may be collectively referred to as the "GNSS antenna 23."

FIG. 2 is a block diagram showing the configuration of the load roller 2.
2 , the road roller 2 is equipped with a correction signal receiver 24, a satellite positioning device 25, a dead reckoning device 26, an operation command device 27, a vehicle control device 28, a communication device 29, a dead reckoning error estimation device 35, and a work management device 3. In addition, the road roller 2 is equipped with a speed sensor 30, an attitude sensor 31, an acceleration sensor 32, an angle sensor 33, and a steering angle sensor 34 (hereinafter referred to as various sensors 36). The work management device 3 may be independent from the road roller 2 and may be located as a server in a management center, for example. In this case, the work management device 3 is configured to be able to communicate with the road roller 2.

[Satellite positioning device]
The satellite positioning device 25 calculates the position of the road roller 2 on the earth based on the GNSS antenna 23 and a communication device 29 (described later). The satellite positioning device 25 calculates an approximate position on the earth (hereinafter, approximate position data 50) and a precise position (hereinafter, precise position data 51).

The satellite positioning device 25 calculates approximate position data 50 and precise position data 51 based on the satellite signal 516 from the positioning satellite 4 received from the GNSS antenna 23 and the correction signal 52 transmitted by the distribution server 9 and received from the communication device 29 via the correction signal receiver 24.

The approximate position data 50 is the approximate position of the road roller 2 calculated by the satellite positioning device 25 using point-based positioning. The precise position data 51 is the precise position of the road roller 2 calculated by the satellite positioning device 25 using RTK-GNSS. The precise position data 51 is a highly accurate positioning result that is closer to the actual position of the road roller 2 than the approximate position data 50.

In standalone positioning, the carrier wave phase between at least four or more positioning satellites 4 and the road roller 2 is determined, the pseudo-distance between the positioning satellites 4 and the road roller 2 is calculated, and approximate position data 50 is calculated using the principle of triangulation. The carrier wave phase is determined by observing the phase of the carrier wave when the positioning satellite 4 transmits a signal. The above carrier wave phase contains errors due to the orbit of each positioning satellite 4, the accuracy of the clocks used in the positioning device 25 and positioning satellite 4, delays in the carrier wave that occur when passing through the ionosphere and troposphere, biases contained in the carrier wave phase, etc.

With RTK-GNSS, the carrier wave phase between at least four or more positioning satellites 4 and the road roller 2, and the carrier wave phase between at least four or more positioning satellites 4 and the reference station 5 are determined. Then, the carrier wave phase difference, which is the difference between the carrier wave phase between the positioning satellite 4 and the road roller 2 and the carrier wave phase between the positioning satellite 4 and the reference station 5, is calculated. With RTK-GNSS, when the GNSS antenna 23 receives the satellite signal 516, the decimal part of the wave number, which part of the continuous wave it is, is known, but the integer part of the wave number excluding the decimal part is unknown. With RTK-GNSS, once this integer part of the wave number is determined, the baseline length between the reference station 5 and the road roller 2 can be accurately determined.

Because the reference station 5 measures its position on Earth with high precision, RTK-GNSS can predict the position of the road roller 2 from the position of the reference station 5 and the baseline length between the road roller 2. With RTK-GNSS, the satellite positioning device 25 calculates precise position data 51 by correcting the stand-alone positioning results using the position of the road roller 2 predicted from the position of the reference station 5 and the baseline length between the road roller 2.

With RTK-GNSS, when the baseline length between the reference station 5 and the road roller 2 is short, it is possible to calculate the baseline length between the position of the reference station 5 and the road roller 2 by canceling out errors caused by delays in the carrier wave that occur when passing through the ionosphere or troposphere, and biases contained in the carrier wave phase, etc. Therefore, the satellite positioning device 25 can determine the wave number integer part of the carrier wave phase difference and calculate precise position data 51.

On the other hand, with RTK-GNSS, if the baseline length between the reference station 5 and the road roller 2 is long, the satellite positioning device 25 cannot determine the wave number integer part of the carrier wave phase difference because it cannot cancel out errors caused by delays in the carrier wave that occur when passing through the ionosphere and troposphere, and biases contained in the carrier wave phase, and therefore cannot calculate the precise position data 51.

In the work management system 1, if the baseline length between the reference station 5 and the load roller 2 becomes longer due to movement of the load roller 2, the satellite positioning device 25 may not be able to calculate the precise position data 51. In the work management system 1, if the satellite positioning device 25 cannot determine the wave number integer part of the carrier wave phase difference, it determines that it cannot calculate the precise position data 51.

In the work management system 1, if the baseline length between the reference station 5 and the load roller 2 becomes long and the positioning device 25 is unable to calculate precise position data 51, a handover process is performed in which the satellite positioning device 25 receives a new correction signal 52 from a reference station 5 with a shorter baseline length rather than the connected reference station 5, enabling the satellite positioning device 25 to calculate precise position data 51.

If the satellite positioning device 25 is able to determine the wave number integer portion using RTK-GNSS, it outputs precise position data 51 to the operation command device 27, communication device 29, work management device 3, and dead reckoning error estimation device. If the satellite positioning device 25 is unable to determine the wave number integer portion using RTK-GNSS, it outputs approximate position data 50 to the communication device 29 and the dead reckoning device.

[Communication Device]
The communication device 29 transmits the position information received from the work management device 3 and the satellite positioning device 25 to the distribution server 9 via the correction signal receiver 24. When the communication device 29 receives the approximate position data 50 or the precise position data 51 as position information from the satellite positioning device 25, it transmits the data to the distribution server 9 as the reference station selection position data 513.

When the communication device 29 receives reference station selection position data 513 from the work management device 3, it transmits the data to the distribution server 9. The distribution server 9 transmits a correction signal 52 in accordance with the reference station selection position data 513 received from the communication device 29. The communication device 29 transmits the correction signal 52 received from the distribution server 9 to the satellite positioning device 25. If the communication device 29 is unable to receive the correction signal 52 transmitted from the distribution server 9, it transmits a correction signal reception error 517 to the work management device 3 via the satellite positioning device 25.

[Dead Reckoning Device]
The dead reckoning device 26 (hereinafter referred to as the DR device) uses sensors that measure parameters indicating the momentum and attitude of the road roller 2 as input to calculate DR relative position data 53, which represents the relative position and azimuth displacement of the road roller 2, for each time step. The DR device 26 calculates the DR relative position data 53 based on the various sensors 36 possessed by the road roller 2. Specifically, the DR device 26 may calculate the DR relative position data 53, which represents the relative position and azimuth displacement of the road roller 2, for each time step by using a Kalman filter or the like on the values of the various sensors 36. When the DR device 26 receives approximate position data 50 from the satellite positioning device 25, it also uses the approximate position data 50 to calculate more accurate DR relative position data 53. The DR device 26 outputs the calculated DR relative position data 53 to the dead reckoning error estimation device 35, the work management device 3, and the operation command device 27.

[Dead reckoning error estimation device]
The dead reckoning error estimation device 35 (hereinafter referred to as the DR error estimation device) estimates DR error data 58, which is the probability distribution of the DR occurrence error 514, based on the satellite positioning device 25 and the DR device 26. The DR error estimation device 35 estimates the current position of the road roller 2 from the sum of the precise position data 51 acquired step t seconds ago and the DR relative position data 53 from step t seconds ago to the present.

The DR error estimation device 35 uses the latest precise position data 51 received from the satellite positioning device 25 as the true value and calculates the error that has occurred in the current position of the load roller 2 estimated from the DR relative position data 53 as the DR occurring error 514. The DR error estimation device 35 calculates and records the DR occurring error 514 to estimate DR error data 58, which is a probability distribution of the DR occurring error 514. The frequency at which the DR occurring error 514 is calculated may be the same as the control period, or may be a specific value such as 5 seconds or 10 seconds. In this way, by making the vertical axis represent the occurrence probability and the horizontal axis represent the DR occurring error 514, a graph such as that shown in Figure 3 can be generated, representing the DR error data 58.

Referring to Figure 3, it is possible to estimate the probability of the DR occurrence error 514 occurring. The step t at which the DR error estimation device 35 records the DR relative position data 53 to calculate the DR occurrence error 514 may be the same value as the control period, or may be a specific value such as 5 seconds or 10 seconds. The DR error estimation device 35 outputs the calculated DR error data 58 to the work management device 3.

[Operation command device]
The operation command device 27 issues operation commands to the vehicle body control device 28 based on the satellite positioning device 25, the DR device 26, and the work management device 3. The operation command device 27 has modes such as normal driving mode, DR driving mode, and handover mode, and the selection of each mode is performed by the work management device 3. The operation command device 27 issues operation commands to the vehicle body control device 28 according to the mode selected by the work management device 3. The normal driving mode, DR driving mode, and handover mode will be described below.

[Normal driving mode]
In the normal travel mode, the road roller 2 follows a travel route 56 described in a work plan (described later) based on precise position data 51 acquired from the satellite positioning device 25. The road roller 2 follows the travel route 56 at the travel speed described in the work plan. The operation command device 27 determines the rotational speed and steering angle of the rollers 21, 22 of the road roller 2 based on the work plan acquired from the work management device 3 and the precise position data 51 acquired from the satellite positioning device 25.

The operation command device 27 determines the rotational speed and steering angle so that the road roller 2 moves along the movement path 56. The operation command device 27 outputs the determined rotational speed and steering angle to the vehicle control device 28 as control data 510.

[DR driving mode]
In the DR travel mode, the road roller 2 follows the travel path 56 described in the work plan based on the DR relative position data 53 acquired from the DR device 26. The road roller 2 follows the travel path 56 at the travel speed described in the work plan. The operation command device 27 determines the rotational speed and steering angle of the rollers 21, 22 of the road roller 2 based on the travel path 56 described in the work plan acquired from the work management device 3, the precise position data 51 last acquired from the satellite positioning device 25, and the DR relative position data 53 acquired from the DR device 26.

The operation command device 27 estimates the current position of the road roller 2 from the precise position data 51 and DR relative position data 53 most recently received from the satellite positioning device 25. The operation command device 27 determines the rotational speed and steering angle so that the road roller 2 moves along the movement path 56. The operation command device 27 outputs the determined rotational speed and steering angle to the vehicle control device 28 as control data 510.

[Handover Mode]
In the handover mode, the road roller 2 stops operating until the satellite positioning device 25 is able to calculate the precise position data 51. The operation command device 27 stops calculating the rotational speed and steering angle, and commands the vehicle body control device 28 to stop operating.

[Vehicle control device]
The vehicle body control device 28 controls the rollers 21, 22 based on the operation command device 27. The vehicle body control device 28 controls the rotational speed and steering angle of the roller 21 based on control data 510 acquired from the operation command device 27. The vehicle body control device 28 controls the rollers 21, 22 based on the control data 510 to operate the road roller 2. When the vehicle body control device 28 is instructed to stop operation by the operation command device 27, it stops the operation of the road roller 2.

[Work management device]
FIG. 4 is a block diagram showing the configuration of the work management device 3.
The work management device 3 manages the operations of the operation command device 27 and the communication device 29 in response to inputs from the satellite positioning device 25, the DR device 26, and the DR error estimation device 35. The work management device 3 is composed of a work plan storage unit 40, an accuracy-deterioration position detection unit 41, an accuracy-recovery position prediction unit 42, a reference station change unit 43, a work command unit 44, and a threshold determination unit 45.

[Work plan storage unit]
The work plan storage unit 40 stores a work plan including the work content, work sequence, and movement speed to be performed by at least one road roller 2. Because the road roller 2 is a self-propelled work machine that compacts the ground, the work content of the road roller 2 in this embodiment is movement along a specified movement path 56. The movement path 56 defines a movement direction, which is the direction in which the road roller 2 moves. The movement path 56 and movement direction of the road roller 2 are stored in the work plan storage unit 40 as the work sequence.

FIG. 5 shows an example of a work plan for the work site 6 stored in the work plan storage unit 40.
The position of the road roller 2 at the work site 6 is defined in a site coordinate system (X, Y, Z). The horizontal direction at the work site 6 is represented by the X-axis and Y-axis. The vertical direction at the work site 6 is represented by the Z-axis. Figure 5 is a top view seen from the Z-axis direction in the site coordinate system. At the work site 6, the area to be compacted by the road roller 2 is defined as a passing area 8. The work plan for the work site 6 describes a movement path 56, movement direction, and movement speed for compacting the passing area 8 by the rollers 21 and 22 of the road roller 2. At the work site 6, the area passed by the rollers 21 and 22 as the road roller 2 moves along the movement path 56 is referred to as a passed area 7. The road roller 2 moves so that the center of the vehicle body overlaps with the movement path 56 when viewed from the Z-axis direction in Figure 5, thereby filling the passing area 8 with the passed area 7.

In this embodiment, the work plan recorded in the work plan memory unit 40 describes the movement path 56 and movement direction of the load roller 2 so that the passing area 8 is filled with the passed area 7 by the load roller 2 moving back and forth in the Y-axis direction in the passing area 8, as shown in Figure 5.

FIG. 6 shows variables that determine the movement path 56 stored in the work plan storage unit 40.
As shown in FIG. 6 , the movement path 56 of the work plan stored in the work plan storage unit 40 is determined by the vehicle width ω of the road roller 2, the gap width L of the movement path 56 in the X-axis direction of the work site 6, and the overlap amount α. The overlap amount α is the X-axis component of the error allowable in the positional relationship between the road roller 2 and the movement path 56. The overlap amount α is expressed by the following (Equation 1) using the gap width L of the movement path 56 and the vehicle width ω. The overlap amount α is the area that the road roller 2 will compact again in the passed area 7 when the road roller 2 moves along the movement path 56 without generating a positioning error, and is the maximum positioning error in the X-axis direction allowable for the road roller 2.

The work plan storage unit 40 pre-stores the vehicle width ω of the road roller 2 and the gap width L of the travel path 56. There are no limitations on the means by which ω and L are stored in the work plan storage unit 40; any means can be used as long as it is possible to edit the work plan in the work plan storage unit 40.

[Accuracy degradation position detection unit]
The degraded accuracy position detection unit 41 detects a degraded accuracy position 54, which is a position on the work site 6 where the positioning accuracy of the road roller 2 has decreased, in accordance with input from the satellite positioning device 25. The degraded accuracy position detection unit 41 acquires precise position data 51 from the satellite positioning device 25. If the degraded accuracy position detection unit 41 is unable to acquire precise position data 51 from the satellite positioning device 25, it determines that the positioning accuracy has decreased, and detects the position of the precise position data 51 received immediately before as the degraded accuracy position 54. The degraded accuracy position detection unit 41 outputs the detected degraded accuracy position 54 to the accuracy recovery position prediction unit 42 and the reference station change unit 43.

[Accuracy return position prediction unit]
The accuracy restoration position prediction unit 42 predicts the accuracy restoration position 55, which is the position on the work site 6 where the positioning accuracy of the road roller 2 will return to a good state, based on the work plan memory unit 40, the accuracy reduction position detection unit 41, and the satellite positioning device 25.

Figure 7 shows an example of an accuracy recovery position 55 predicted by the accuracy recovery position prediction unit 42. Figure 7 is a top view seen from the Z-axis direction in the on-site coordinate system. The accuracy recovery position prediction unit 42 acquires the accuracy loss position 54 from the accuracy loss position detection unit 41. Next, the accuracy recovery position prediction unit 42 acquires the position of the reference station 5 described in the correction signal 52 from the satellite positioning device 25, and calculates the distance LL from the accuracy loss position 54 to the reference station 5.

The accuracy recovery position prediction unit 42 assumes that the range LL around the reference station 5 is the observation range 57 within which the positioning device 25 can calculate precise position data 51. The accuracy recovery position prediction unit 42 then obtains the movement path 56 of the dump truck 2 from the work plan memory unit 40, and calculates the position closest to the accuracy-decreased position 54 on the movement path 56 where the distance to the reference station 5 is again LL and is again within the observation range 57 of the reference station 5, and sets this position as the accuracy recovery position 55.

[Threshold determination unit]
The threshold determination unit 45 determines an error threshold 511, which is the positioning error allowable for the road roller 2 and which is used by the reference station change unit 43 (described later) to determine whether to change the reference station, based on the work plan memory 40 and the accuracy return position prediction unit 42. The threshold determination unit 45 determines the allowable positioning error of the road roller 2 at the accuracy return position 55 predicted by the accuracy return position prediction unit 42 as the error threshold 511. The threshold determination unit 45 calculates the overlap amount α using Equation 1 from the vehicle width ω of the road roller 2 and the gap width L of the movement path 56 recorded in the work plan memory unit 40. The threshold determination unit 45 sets the calculated overlap amount α as the error threshold 511.

[Reference Station Change Department]
The reference station change unit 43 determines whether to change the reference station 5 that receives the correction signal 52, based on the work plan storage unit 40, the accuracy recovery position prediction unit 42, and the DR error estimation device 35. The reference station change unit 43 estimates the DR prediction error ε[I] between the road roller 2 and the movement path 56 that occurs when the road roller 2 travels along the movement path 56 from the accuracy reduction position 54 to the accuracy recovery position 55 in DR travel mode, based on the DR error data 58 estimated by the DR error estimation device 35, and determines whether to change the connected reference station 5.

The processing of the reference station change unit 43 will be explained below with reference to Figures 8, 9, and 10.

FIG. 8 is a flowchart showing the processing of the reference station change unit 43.
In step S101, the movement path 56 of the load roller 2 is obtained from the work plan recorded in the work plan storage unit 40. In step S102, the accuracy-degraded position 54 detected by the accuracy-degraded position detection unit 41 is obtained.

In step S103, the precision return position 55 predicted by the precision return position predicting unit 42 is acquired.
In step S104, a reference point 59 is generated on the movement path 56 from the precision-decreased position 41 to the precision-recovered position 42.

Figure 9 shows a reference point 59 generated on the movement path 56 from the accuracy-reduced position 41 to the accuracy-restored position 42. Figure 9 is a top view seen from the Z-axis direction in the on-site coordinate system.

The reference points 59 are positions at which the DR prediction error ε[I] is calculated in the next step S105. The reference points 59 may be generated based on the control period of the load roller 2, assuming that the load roller 2 moves along the movement path 56 at the movement speed specified in the work plan based on the work plan storage unit 40. The reference points 59 may also be generated on the movement path 56 at the stored generation intervals by storing the generation intervals on the movement path 56 in advance in the reference station change unit 43. The number of generated reference points 59 is defined as N.

The first reference point 59 is the precision-reduced position 54, and the Nth reference point 59 is the precision-recovered position 55. The value of the DR prediction error ε(1) at the precision-reduced position 54 is 0. The reference points 59 are numbered from 2 to N-1 on the movement path 56, starting from the position closest to the precision-reduced position 54.

In step S105, a second reference point 59 is selected. In step S106, the DR prediction error ε[I] at the selected reference point 59 is calculated based on the DR error data 58 acquired from the DR error estimation device 35. The number of the selected reference point 59 is set to I. The reference station change unit 43 predicts the path deviation amount 515 when the road roller 2 moves from the position of the I-1th reference point 59 to the Ith reference point 59.

Figure 10 shows the definition of the path deviation amount 515. Figure 10 is a top view seen from the Z-axis direction in the site coordinate system.

The candidate movement points shown in Figure 10 are positions that the load roller 2 may reach when it moves to the next reference point, and there are an infinite number of candidate movement points. As shown in Figure 10, the path deviation amount 515 is defined as the orthogonal component distance from the movement path 59 at the candidate movement point. It is assumed that the path deviation amount 515 occurs probabilistically based on the probability distribution of the DR error data 58.

The reference station change unit 43 predicts the route deviation amount 515 from the error variance based on the DR error data 58. The reference station change unit 43 calculates the DR prediction error ε[I] from the maximum DR occurrence error 514 in the probability distribution of the DR error data 58. The DR prediction error ε[I] may also be calculated using values in the 1σ, 2σ, and 3σ intervals of the probability distribution of the DR error data 58.

In step S107, it is determined whether all reference points 59 from 2 to N have been selected. If not, the next reference point 59 is selected and the process returns to step S106. If all have been selected, the process proceeds to step S108.

In step S108, the DR prediction error ε[I] is summed over the entire section from the second to the Nth reference points 59 to calculate the DR total prediction error 512 predicted at the precision return position 55.

In step S109, the error threshold 511 allowed at the precision return position 55 obtained from the threshold determination unit 45 is obtained. In step S110, the DR total prediction error 512 is compared with the error threshold 511 obtained in step S109. If the DR total prediction error 512 is equal to or greater than the error threshold 511, proceed to step S111. If the DR total prediction error 512 is less than the error threshold 511, proceed to step S112.

In step S111, the precise position data 51 last received from the satellite positioning device 25 is transmitted to the work command unit 44 as the reference station selection position data 513. Then, the work command unit 44 is instructed to enter handover mode, and processing ends. In step S112, the position of the connected reference station 5 is transmitted to the work command unit 44 as the reference station selection position data 513. Then, the work command unit 44 is instructed to enter DR driving mode, and processing ends.

[Work command department]
The work command unit 44 selects the mode of the operation command device 27 based on the work plan storage unit 40, the reference station changing unit 43, the satellite positioning device 25, and the DR device 26. The work command unit 44 sets the operation command device 27 to the normal driving mode when the accuracy-degraded position detection unit 41 does not detect a accuracy-degraded position 54.

The work command unit 44 changes the operation command device 27 to DR driving mode or handover mode based on the decision of the reference station change unit 43. The work command unit 44 transmits the reference station selection position data 513 received from the reference station change unit 43 to the communication device 29. When the work command unit 44 selects DR driving mode, it predicts the route deviation amount 515 shown in FIG. 10 using the precise position data 51 and DR relative position data 53 last received from the satellite positioning device 25.

If the route deviation amount 515 exceeds the error threshold 511 determined by the threshold determination unit 45, the work command unit changes the operation command device 27 to handover mode. If the work command unit 44 receives a correction signal reception error 517 from the communication device 29 via the satellite positioning device 25, it changes the operation command device 27 to DR driving mode. If the work command unit 44 receives precise position data 51 from the positioning device 25, it changes the operation command device 27 from DR driving mode to normal driving mode. If the positioning device 25 acquires a correction signal 52 from the communication device 29, the work command unit 44 changes the operation command device 27 from handover mode to normal driving mode.

The processing of the work management system 1 will be explained below with reference to Figures 11 and 12. Figure 11 is a flowchart showing the processing of the work management system 1. Figure 12 is a flowchart showing the processing of the work management device 3.

In step S201, the operation command device 25 is set to handover mode. In step S202, the satellite positioning device 25 receives a satellite signal 516 from the positioning satellite 4 via the GNSS antenna 23.

In step S203, it is determined whether the communication device 29 is connected to the distribution server 9. If it is connected, proceed to step S206. If it is not connected, proceed to step S204.

In step S204, the satellite positioning device 25 performs standalone positioning and calculates approximate position data 50. In step S205, the communication device 29 receives the approximate position data 50 from the satellite positioning device 25 and determines it as reference station selection position data 513. In step S206, the communication device 29 transmits the reference station selection position data 513 to the distribution server 9.

In step S207, the communication device 29 determines whether it has received a correction signal 52 from the distribution server 9. If it has, proceed to step S208. If it has not, proceed to step S210. In step S208, the communication device 29 outputs the correction signal 52 received from the distribution server 9 to the satellite positioning device 25.

In step S209, the satellite positioning device 25 calculates precise position data 51 using RTK-GNSS using the satellite signal 516 and correction signal 52. In step S210, it is determined whether the operation command device 25 is in handover mode. If it is in handover mode, the process returns to step S206. If it is not in handover mode, the process proceeds to step S211.

In step S211, the communication device 29 sends a correction signal reception error 517 to the work command unit 44. In step S212, the work command unit 44 determines whether the road roller 2 has finished traveling along the movement path described in the work plan. If it has finished traveling, the process ends. If it has not finished, the process proceeds to step S213.

In step S213, the work command unit 44 determines whether precise position data 51 has been received from the satellite positioning device 25. If precise position data 51 has been received, the process proceeds to step S214. If precise position data 51 has not been received, the process proceeds to step S216. In step S214, the work command unit 44 switches the operation command device 27 to normal driving mode.

In step S215, the work command unit 44 outputs a work plan to the operation command device 27 based on the work plan memory unit 40. In step S216, the accuracy-degraded position detection unit 41 detects the accuracy-degraded position 54. In step S217, the threshold determination unit 45 determines the error threshold 511 based on the work plan memory unit 40.

In step S218, the accuracy recovery position prediction unit 42 calculates the accuracy recovery position 55 based on the accuracy degradation position detection unit 41, the work plan memory unit 40, and the satellite positioning device 25. In step S219, the reference station change unit 43 determines whether to change the connected reference station 5 based on the accuracy degradation position detection unit 41, the accuracy recovery position prediction unit 42, the DR error estimation device 35, and the threshold determination unit 45. If the connected reference station 5 is to be changed, proceed to step S222. If the connected reference station 5 is not to be changed, proceed to step S220.

In step S220, the reference station change unit 43 sets the position of the connected reference station 5 as the reference station selection position data 513 and transmits it to the communication device 29. In step S221, the work command unit 44 changes the operation command device 27 to DR driving mode. In step S222, the reference station change unit 43 sets the precise position data 51 last received from the satellite positioning device 25 as the reference station selection position data 513 and transmits it to the communication device 29.

In step S223, the work command unit 44 changes the operation command device 27 to handover mode. In step S224, the DR device 26 calculates the DR relative position data 53. In step S225, it is determined whether the satellite positioning device 25 successfully calculated the precise position data 51. If successful, proceed to step S226. If not successful, proceed to step S227. In step S226, the DR error estimation device 35 calculates the DR error data 58 based on the satellite positioning device 25 and the DR device 26.

In step S227, the operation command device 27 determines the control data 510 based on the selected mode. In step S228, the vehicle control device 28 controls the road roller 2 based on the control data 510. In step S229, the communication device 29 determines whether the reference station selection position data 513 received is identical to the position of the connected reference station 5. If they are identical, proceed to step S230. If they are not identical, return to step S202.

In step S230, the work command unit 44 changes the operation command device 27 to DR driving mode. In step S231, the work command unit 44 calculates the route deviation amount 515 using the precise position data 51 and DR relative position data 53 last received from the satellite positioning device 25. In step S232, the work command unit 44 determines whether a correction signal reception error 517 has been received from the communication device 29. If received, proceed to step S234. If not received, proceed to step S233.

In step S233, the work command unit 44 determines whether the load roller 2 has reached the accuracy return position 55. If it has reached it, the process returns to step S214. If it has not reached it, the process proceeds to step S234. In step S234, the work command unit 44 determines whether the path deviation amount 515 exceeds the error threshold value 511. If it does, the process returns to step S222. If it does not, the process returns to step S215.

In this embodiment, when the work management device 3 detects the accuracy-return position 54, it predicts the accuracy-return position 55. The work management device 3 then calculates the DR total predicted error 512 that occurs at the accuracy-return position 55 when the load roller 2 travels the movement path 6 from the accuracy-return position 54 to the accuracy-return position 55 in DR travel mode. Finally, the work management device 3 determines whether to change the connected reference station 5 based on the DR total predicted error 512 and the error threshold 511.

In this way, even if the satellite positioning device 25 at the work site 6 is unable to calculate precise position data 51, it can confirm that the road roller 2 can reach the precision return position 55, allowing the reference station change unit 43 to determine whether to perform a handover and instruct the work machine, which has switched to dead reckoning, to follow the vehicle. This allows the road roller 2 to continue operating automatically, preventing a decline in productivity.

In this embodiment, when a decrease in positioning accuracy is detected, the point where positioning accuracy will recover is predicted and the system switches to dead reckoning. If the work machine can reach that point, it continues to operate without performing a handover. If the work machine cannot reach that point, it stops at the location where positioning accuracy has decreased and performs a handover.

In other words, when a decline in positioning accuracy is detected in a work machine following along a travel route, the system predicts the point where positioning accuracy is expected to recover, and determines whether the work machine can reach that point based on the predicted error when the work machine follows the target by switching to dead reckoning. If the work machine is able to travel to the point where positioning accuracy is expected to recover, the system instructs the work machine to switch to dead reckoning and follow the target to that point. This prevents a decrease in productivity due to work being redone.

1 Work management system 2 Road roller 3 Work management device 25 Satellite positioning device 26 Dead reckoning device 27 Operation command device 28 Vehicle control device 29 Communication device 40 Work plan memory unit 41 Accuracy reduction position detection unit 42 Accuracy recovery position prediction unit 43 Reference station change unit 44 Work command unit 45 Threshold value determination unit 54 Accuracy reduction position 55 Accuracy recovery position 513 Reference station selection position data

Claims (10)

A work management system that receives satellite signals transmitted from positioning satellites and correction information transmitted from a reference station and automatically drives a work machine that performs work on a work site along a travel route,
a positioning unit that performs positioning of the work machine based on the satellite signal and the correction information;
a work plan storage unit that stores a work plan in which the movement route on the work site is described;
a threshold determination unit that determines an allowable error between the travel path and the position of the work machine;
an accuracy reduction position detection unit that detects an accuracy reduction position, which is a position where the positioning accuracy of the work machine has decreased, based on the positioning result of the positioning unit;
an accuracy recovery position prediction unit that predicts an accuracy recovery position, which is a position at which the positioning accuracy of the work machine will recover, based on the movement path and the accuracy-deteriorated position;
a reference station change unit that calculates a predicted error that occurs on the movement path between the accuracy-decreased position and the accuracy-recovered position, and changes the reference station that receives the correction information when the predicted error exceeds the allowable error;
A work management system comprising: a control command unit that commands control of the work machine based on the positioning result of the positioning unit and the work plan;
a vehicle body control unit that operates the work machine based on the command from the control command unit,
The reference station changing unit
determining a change in the reference station connected to the work machine based on the predicted error and the allowable error;
The control command unit
The work management system according to claim 1, characterized in that, between the accuracy-decreasing position and the accuracy -restoring position, the work machine is instructed to be controlled so as to switch the driving mode of the work machine depending on the judgment result of the reference station changing unit. The reference station changing unit
calculating the predicted error that will occur at the accuracy restoration position when the work machine travels along the movement path from the accuracy reduction position to the accuracy restoration position;
determining whether the work machine can reach the precision return position based on the predicted error;
The control command unit
If the result of the determination by the reference station changing unit is that the work machine can reach the accuracy return position, the reference station changing unit instructs the work machine to travel to the accuracy return position, and allows the work machine to continue operating without executing a handover of the base station;
The work management system according to claim 2, characterized in that, if the result of the judgment by the reference station change unit is that the work machine cannot reach the accuracy restoration position, the work machine is stopped at the accuracy reduction position and the handover of the base station is performed. The work plan storage unit
a no-entry area for the work machine is stored as part of the movement route on the work site;
The threshold value determination unit
2. The work management system according to claim 1, wherein the allowable error is determined based on the work plan within a range in which the work machine does not enter the no-entry area for the work machine. The accuracy return position prediction unit
2. The work management system according to claim 1, wherein the distance between the reference station and the position of reduced accuracy is calculated, and the position on the movement path on the work site where the distance becomes equal to the calculated distance again is predicted as the position of restored accuracy. The positioning unit
2. The work management system according to claim 1, wherein the correction information is received from the reference station that is closest to the position information of the work machine obtained from a communication device. The reference station changing unit
7. A work management system according to claim 6, wherein when the reference station that receives the correction information is changed, the position information of the work machine is input to the positioning unit. The reference station changing unit
7. The work management system according to claim 6, wherein, when the reference station that receives the correction information is not changed, position information different from the position information of the work machine is input to the positioning unit. The reference station changing unit
The work management system according to claim 8, characterized in that, when the reference station that receives the correction information is not changed, the position information of the reference station is input to the positioning unit as the position information different from that of the work machine. A work management method for automatically traveling a work machine that performs work at a work site along a travel route by receiving satellite signals transmitted from a positioning satellite and correction information transmitted from a reference station, comprising:
a positioning step of performing positioning of the work machine based on the satellite signal and the correction information;
a work plan storage step of storing a work plan in which the movement route on the work site is described;
a threshold determination step for determining an acceptable error in the travel path and the position of the work machine;
an accuracy reduction position detection step of detecting an accuracy reduction position, which is a position where the positioning accuracy of the work machine has decreased, based on the positioning result of the positioning step;
an accuracy recovery position prediction step of predicting an accuracy recovery position, which is a position at which the positioning accuracy of the work machine will recover from the movement path, based on the movement path and the accuracy-deteriorated position;
a reference station changing step of calculating a predicted error that occurs on the movement path between the accuracy-decreased position and the accuracy-recovered position, and changing the reference station that receives the correction information when the predicted error exceeds the allowable error;
A work management method comprising: