CN113567030B - Plane series non-coupling six-dimensional wrist force sensor - Google Patents

Abstract

The invention discloses a planar serial non-coupling six-dimensional wrist force sensor, which includes an integrally formed elastic structure and a strain gauge group pasted thereon; the elastic structure includes a fixed platform, an internal and external connecting body, a central loading platform and a T connecting the three T-shaped elastic branch chains and elastic main beams, T-shaped elastic branch chains and elastic main beams each constitute a cross structure and are staggered at 45° and evenly arranged. The beam forms an overall series connection structure; the present invention separates the force and moment outside the measurement plane and the inside of the measurement plane, realizes separate decoupling measurements, realizes the decoupling of force and moment from the structure, and effectively solves the problem of coupling crosstalk between force and moment signals. It has the characteristics of compact structure, low height, and adjustable stiffness. It is suitable for rapid perception and measurement of multi-dimensional forces and moments by the wrists of industrial and collaborative robots in industrial scenarios such as polishing, grinding, and assembly when performing operations.

Description

Planar serial uncoupled six-dimensional wrist force sensor

technical field

The invention relates to the technical field of sensors, in particular to a planar serial non-coupling six-dimensional wrist force sensor.

Background technique

In recent years, with the rapid development of industrial and collaborative robot technology, the force perception of the external operating environment of industrial robots has Detection and perception capabilities put forward higher requirements. Industrial robots with force perception can respond to unknown operating environments correctly, quickly and reliably, and dynamically adjust the position and posture of industrial robots in a timely manner to achieve flexible operation and environmental adaptability of industrial robots. The six-dimensional force and torque sensor is an important carrier to realize spatial full force and torque information perception. Its real-time and fast detection and processing of force and torque information determines the response time of industrial robots to make pose adjustments, which in turn affects the operation of industrial robots. precision and operational reliability. Six-dimensional force and torque detection technology is an important part of robot sensing technology. Whether the signals of six-dimensional force and torque sensors are coupled between each dimension has influence on response time, signal solution complexity, data detection and processing circuit design, etc. Obviously, it will affect the force control accuracy of the robot's end effector.

After searching the literature of the prior art, it is found that the Chinese patent CN102095534B provides a six-dimensional force and moment sensor with an upper and lower double-layer cross-beam structure, and an "I"-shaped through hole is set through the cross-beam and the outer end of the cross-beam structure is connected to the main frame of the sensor The sliding pair design can eliminate the inter-dimensional crosstalk caused by the floating beam in the traditional cross beam structure, which is beneficial to improve the measurement accuracy of the sensor. However, due to the use of threaded assembly, there is a gap in the structure, which will cause wear and looseness during use, and zero point drift. Problems such as poor positioning and need for repeated calibration.

Chinese patent CN103940544B provides a double-cross beam combined finger joint six-dimensional force sensor design, which satisfies multi-dimensional measurement and realizes the miniaturization of the sensor structure. The elastic body structure will increase the sensor assembly process, overall height, weight and load on the installation site, which is not conducive to the dexterous operation of the end effector.

Chinese patent CN201811372150 provides a six-dimensional force sensor design with a "T" shape structure. By opening transverse through holes on the radial beam and the floating beam, both the stiffness of the sensor and the measurement resolution are considered, but the vertical The placement increases the height of the sensor, which increases the deformation of the sensor due to the overall force, thereby reducing the operation accuracy of the end effector.

Chinese patent CN201911306482 provides a six-dimensional force and moment sensor design with a double "worker" cross-beam structure. The main beam of the classic cross-beam structure is used to measure the in-plane and out-of-plane force and moment parts respectively, forming an orthogonal " The "I"-shaped main beam structure improves the sensitivity of the sensor measurement and reduces the inter-dimensional coupling, but the double "I"-shaped cross-beam structure design reduces the sensor range and cannot reduce the coupling of the bending moment to the lateral force output signal.

Although the above-mentioned patents have innovatively improved the design of the six-dimensional force sensor structure, the current design of the six-dimensional force sensor still has complex structures, large heights, load-bearing and To overcome the problems of weak overload capacity, complex assembly, and large inter-dimensional coupling, a new type of six-dimensional force sensor is designed and developed to make it easy to process and manufacture and significantly reduce or eliminate a series of problems caused by inter-dimensional coupling. Low and easy design detection of external measurement circuits will be of great significance.

Contents of the invention

In order to solve the above problems, the present invention provides a planar serial uncoupled six-dimensional wrist force sensor.

The technical solution of the present invention: a planar series uncoupled six-dimensional wrist force sensor, the sensor includes an elastic structure and a strain gauge group; The connecting body and the central loading platform, 4 T-shaped elastic branch chains connected between the fixed platform and the inner and outer connecting bodies, and 4 elastic main beams connected between the inner and outer connecting bodies and the central loading platform; 4 T-shaped elastic The branch chain and the four elastic main beams are all arranged in a positive cross around the axis of the central loading platform, and at the same time, they are arranged staggered at 45°; the fixed platform is an octagonal frame, and the inner and outer sides of the fixed platform are rounded. transition;

The T-shaped elastic branch chain includes an elastic beam and a floating beam, the outer end of the elastic beam is connected to the middle part of the floating beam, the inner end of the elastic beam is fixedly connected to the outside of the inner and outer connectors, and the floating beam is arranged on one of the frames of the fixed table to form a frame with the frame. In one body, 4 floating beams are distributed on the 4 frames of the fixed table at intervals of 90°;

The internal and external connecting body is a symmetrical frame with four corners and four sides, and the four corners are convex and respectively point to the middle of the frame of the fixed platform without T-shaped elastic branch chains, and a gap is left for lateral overload protection. The middle part of the frame of the inner and outer connecting body is an inner concave part for sticking strain gauges, and the inner end of the elastic beam is connected to the outer surface of the inner concave part;

The central loading platform is located at the center of the elastic structure, and the four cuboid elastic main beams are distributed in a cross shape around the axis of the central loading platform at intervals of 90°, and the inner ends of the elastic main beams are fixedly connected to the outer side of the central loading platform; The outer ends of the elastic main beam respectively extend to the inner surfaces of the four corners of the inner and outer connectors and are fixedly connected;

The strain gauge group is formed on the elastic main beam and the elastic beam.

There are fixed through holes on the frame of the fixed platform where no T-shaped elastic branch chain is arranged; the central loading platform is provided with installation through holes uniformly distributed along the circumference around its axis and penetrating the upper and lower surfaces.

The elastic beam is provided with dumbbell-shaped double communication holes, and the double communication holes are composed of two circular through holes and a rectangular through hole; the floating beam is symmetrically provided with two rectangular through holes on the center line of the elastic beam. Through hole, one side of the rectangular through hole coincides with the side of the elastic beam. The rectangular through hole divides the floating beam into an inner floating beam and an outer floating beam. The width of the outer floating beam is d1, and the width of the inner floating beam is d2, and d1 and d2 can be different equal.

The inner surface of the concave part in the internal and external connecting body is close to the central loading platform, and there is a certain gap; the inner sides of the four corners of the internal and external connecting body are rectangular relief gaps matching the shapes of the four elastic main beams, and the inner surface is close to the elastic There is a certain gap on the side of the main beam.

The fixed platform, the internal and external connectors, the central loading platform and the elastic main beam, as well as the elastic beam and the floating beam of the T-shaped elastic branch chain are all integrally formed structures, and they are arranged on the center plane in the thickness direction; the fixed platform, the internal and external connections The body and the central loading platform are integrally connected in series through T-shaped elastic branch chains and elastic main beams.

The thickness of the elastic beam and the floating beam of the fixed platform, the internal and external connectors and the T-shaped elastic branch chain are equal, both are D, the thickness of the elastic main beam is d, the thickness of the central loading platform is L, and d<D< L.

Compared with the prior art, the beneficial technical effect of the present invention is:

1. The present invention adopts the fixed platform, the internal and external connectors and the central loading platform to form an overall series connection structure through the T-shaped elastic branch chain and the elastic main beam in sequence, and separates the force and moment outside the measurement surface and the measurement surface inside to realize decoupling measurement respectively , realize the decoupling of force and torque from the structure, and effectively solve the problem of coupling crosstalk between force and torque signals;

2. The T-shaped elastic branch chain and the elastic main beam each constitute a cross structure and are arranged staggered at 45°. The space gap of the traditional cross beam structure is effectively used, and the structure is more compact, and the planar series structure design makes the overall height of the sensor reduce. Low, can significantly reduce the operation error caused by the deformation of the sensor to the end effector;

3. The design of the inner and outer floating beams realizes the adjustable stiffness of the T-shaped structure and the connecting end of the inner connecting body, thereby improving the overall stiffness of the sensor and the measurement sensitivity of the force and moment in the measurement surface;

4. Low processing cost, one-piece manufacturing can be realized, which can significantly reduce or eliminate problems such as low measurement accuracy and repeated calibration caused by assembly gaps and errors;

5. Reasonable gap setting between the inner connecting body and the fixed platform, so that the sensor has the ability to protect the sensor from lateral force overload;

6. The elimination of the coupling between the measurement bridges and road dimensions of the sensor will significantly reduce the complexity of the external circuit and measurement decoupling algorithm, and improve the response time of the sensor. It is especially suitable for industrial scenarios such as polishing, grinding, assembly, etc. where industrial and collaborative robots are used. Rapid perception and measurement of multidimensional forces and moments at the wrist when performing manipulation tasks.

Description of drawings

Fig. 1 is a perspective view of an elastic structure;

Fig. 2 is the left side view of elastic structure;

Fig. 3 is the front view of elastic structure;

Fig. 4 is A-A sectional view among Fig. 3;

Fig. 5 is a perspective view of the present invention;

Fig. 6 is the front view of the present invention;

Fig. 7 is the measurement schematic diagram of embodiment two;

In the figure: 1. Fixed platform, 11. Fixed through hole, 2. Internal and external connecting body, 3. Center loading platform, 31. Installation through hole, 4. T-shaped elastic branch chain, 41. Floating beam, 411. Inner floating beam , 412. Outer floating beam, 42. Elastic beam, 43. Double communicating hole, 44. Rectangular through hole, 5. Elastic main beam, 6. Strain gauge.

Detailed ways

Embodiment 1: Referring to Figures 1-4, the planar series uncoupled six-dimensional wrist force sensor in the figure is characterized in that: the sensor includes an elastic structure and a set of strain gauges; the elastic structure includes a fixed platform located on the outer ring , the internal and external connectors arranged coaxially with the fixed platform and the central loading platform, 4 T-shaped elastic branch chains connected between the fixed platform and the internal and external connectors, and 4 T-shaped elastic branch chains connected between the internal and external connectors and the central loading platform The four elastic main beams, the four T-shaped elastic branch chains and the four elastic main beams are all arranged in a positive cross around the axis of the central loading table, and at the same time, they are arranged staggered at 45°; the fixed table is octagonal Shaped frame, the inner and outer sides of the fixed platform are transitioned through rounded corners.

The T-shaped elastic branch chain includes an elastic beam and a floating beam, the outer end of the elastic beam is connected to the middle part of the floating beam, the inner end of the elastic beam is fixedly connected to the outside of the inner and outer connectors, and the floating beam is arranged on one of the frames of the fixed table to form a frame with the frame. In one body, 4 floating beams are distributed on the 4 frames of the fixed table at intervals of 90°;

The four corners and four sides of the internal and external connectors are symmetrical frames, and the four corners are convex and point to the middle of the frame of the fixed platform without T-shaped elastic branch chains respectively, and there are gaps for lateral overload protection. The middle part of the frame of the connecting body is an inner concave part to facilitate pasting the strain gauge, and the inner end of the elastic beam is connected to the outer surface of the inner concave part;

The central loading platform is located at the center of the elastic structure, and the four cuboid elastic main beams are distributed in a cross shape around the axis of the central loading platform at intervals of 90°, and the inner ends of the elastic main beams are fixedly connected to the outer side of the central loading platform; The outer ends of the elastic main beam respectively extend to the inner surfaces of the four corners of the inner and outer connectors and are fixedly connected;

The strain gauge group is formed on the elastic main beam and the elastic beam.

The two cross-beam plane series structures of the sensor are integrated and compactly arranged in the same plane. Compared with the patent documents mentioned in the background technology, the elastic body is a plane structure, and the thickness direction occupies The space is smaller, thereby reducing the operating error caused by the deformation of the sensor to the actuator. In addition, it is arranged in an integrated symmetrical structure, which avoids the problem of the stacked installation and combination scheme in the comparison patent, and there is no difficulty in assembly and loosening after assembly. Maintenance After loading, the stress and strain distribution of the load on the elastic structure is relatively uniform, and there will be no problem of load concentration of the assembly structure at the installation site.

The present invention isolates the force and moment outside the measurement surface and the inside of the measurement surface, realizes separate decoupling measurement, realizes the decoupling of force and moment from the structure, effectively solves the problem of coupling crosstalk between force and moment signals, and has the advantages of compact structure, low height, Features such as adjustable stiffness.

The frame of the fixed platform without T-shaped elastic branch chains is provided with fixed through holes; the central loading platform is provided with installation through holes that are uniformly distributed along the circumference around its axis and run through the upper and lower surfaces. The holes are used for the sensor to be bridged between the wrist of the industrial or collaborative robot arm and the end effector, and the evenly distributed installation through holes facilitate the transmission of external loads to the elastic structure.

The elastic beam is provided with dumbbell-shaped double communication holes, and the double communication holes are composed of two circular through holes and a rectangular through hole; the floating beam is symmetrically provided with two rectangular through holes on the center line of the elastic beam. Through hole, one side of the rectangular through hole coincides with the side of the elastic beam. The rectangular through hole divides the floating beam into an inner floating beam and an outer floating beam. The width of the outer floating beam is d1, and the width of the inner floating beam is d2, and d1 and d2 can be different equal.

The inner surface of the recessed part of the internal and external connecting body is close to the central loading platform, and a certain gap is provided; the inner sides of the four corners of the internal and external connecting body are rectangular relief gaps matching the shapes of the four elastic main beams. The side is close to the side of the elastic main beam with a certain gap. The shape and structure of the inner and outer connectors reserve enough space for the elastic main beam without increasing the overall size of the elastic structure, so as to ensure a smaller and more compact sensor structure.

The fixed platform, the internal and external connectors, the central loading platform and the elastic main beam, as well as the elastic beam and the floating beam of the T-shaped elastic branch chain are all integrally formed structures, and they are arranged on the center plane in the thickness direction; the fixed platform, the internal and external connections The body and the central loading table are connected in series from the outside to the inside through the T-shaped elastic branch chain and the elastic main beam.

The thickness of the elastic beam and the floating beam of the fixed platform, the internal and external connectors and the T-shaped elastic branch chain are equal, both are D, the thickness of the elastic main beam is d, the thickness of the central loading platform is L, and d<D< L.

Embodiment 2: Referring to Figures 5-7, on the basis of Embodiment 1, the strain gauge group is pasted on the elastic beam and the elastic main body by several resistive or foil strain gauges according to the actual force and moment to be measured. Composed on the beam, 12 strain gauges are pasted on the upper and lower surfaces of the elastic main beam to form three strain gauge groups, which are responsible for detecting the normal force and lateral bending moment acting on the upper and lower symmetrical planes of the central loading platform; A total of 12 strain gauges are pasted on both sides of the elastic beam of the connecting hole, forming three strain gauge groups, which are responsible for detecting the lateral force and normal torque acting on the upper and lower symmetrical planes of the central loading platform.

In Figure 7, two coordinate systems OX ₀ Y ₀ Z and OX _I Y _I Z are specified with the center of the central loading table as the coordinate origin, OX ₀ Y ₀ is coplanar with the OX _I Y _I plane and is located above and below the elastic structure On the symmetry plane, the OX _I axis is collinear with the longitudinal symmetry line of the elastic beam on a T-shaped elastic branch chain, and the Z direction is collinear with the normal symmetry center of the central loading table. OX ₀ Y ₀ Z can be OX _I Y _I Z to be OZ Rotate counterclockwise by 45° to obtain; two elastic main beams on the X ₀ axis, each elastic main beam has two strain gauges pasted on the upper and lower surfaces of each surface, and two elastic main beams on the Y ₀ axis, each elastic main beam One strain gauge is pasted on each surface of the upper and lower surfaces of the beam, and the ones in brackets represent the strain gauges corresponding to the position of the lower surface and the upper surface; two elastic beams on the X _{and I} axes, and two on each side of each elastic beam Strain gauges, two elastic beams on the Y _I axis, and one strain gauge is pasted on each side of each elastic beam.

Among them, the strain gauges R1-R4 form a Wheatstone full-bridge circuit 1 for measuring the in-plane lateral force Fx _I ; the strain gauges R5-R8 form a Wheatstone full-bridge circuit 2 for measuring the in-plane lateral force Fy _I ; Strain gauges R9-R12 form a Wheatstone full-bridge circuit 3 for measuring out-of-plane torque Mz; strain gauges R13-R16 form a Wheatstone full-bridge circuit 4 for measuring out-of-plane normal force Fz ₀ ; strain gauge R17 ~R20 constitutes a Wheatstone full-bridge circuit 5 for measuring out-of-plane lateral bending moment Mx ₀ ; strain gauges R21-R24 form a Wheatstone full-bridge circuit 6 for measuring out-of-plane lateral bending moment My ₀ ; In the drawings and drawings, only one kind of strain gauge pasting position, quantity and method for decoupling is listed, and the position, quantity and method of strain gauge pasting can be selected according to the actual needs of decoupling, and all belong to the protection scope of this patent.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand; Modifications to the technical solutions recorded, or equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, which are based on the spirit of the present invention. Any modification or replacement should be included in the scope of protection required by the present invention.

Claims (6)

1. The six-dimensional wrist force sensor is characterized in that: the sensor comprises an elastic structure body and a strain gauge group; the elastic structure body comprises a fixed table positioned on the outer ring, an inner and outer connecting body and a central loading table which are coaxially arranged with the fixed table, 4T-shaped elastic branched chains connected between the fixed table and the inner and outer connecting body, and 4 elastic main beams connected between the inner and outer connecting body and the central loading table; the 4T-shaped elastic branched chains and the 4 elastic main beams are all arranged in a regular cross shape along the circumference by taking the axis of the central loading platform as the center, and are uniformly arranged in a staggered manner at an angle of 45 degrees; the fixing table is an octagonal frame, and the inner side surface and the outer side surface of the fixing table are in transition through round corners;

the T-shaped elastic branched chain comprises an elastic beam and floating beams, the outer end of the elastic beam is connected to the middle part of the floating beam, the inner end of the elastic beam is fixedly connected to the outer side of the inner and outer connecting bodies, the floating beams are arranged on one frame of the fixed table and integrated with the frame, and 4 floating beams are distributed on 4 frames of the fixed table at intervals of 90 degrees;

the inner and outer connecting bodies are frame bodies with four corners and four sides symmetrical, the four corners are in a convex shape and point to the middle part of a frame of the fixed station without the T-shaped elastic branched chain respectively, a gap is reserved to play a role in transverse overload protection, the middle part of the frame of the inner and outer connecting bodies is an inner concave part so as to be convenient for pasting a strain gauge, and the inner end of the elastic beam is connected to the outer side surface of the inner concave part;

the central loading platform is positioned at the center of the elastic structure body, four rectangular elastic main beams are distributed in a cross shape around the axis of the central loading platform at intervals of 90 degrees, and the inner ends of the elastic main beams are fixedly connected with the outer side surface of the central loading platform; the outer ends of the four elastic main beams respectively extend to the inner side surfaces of the four corners of the inner and outer connectors and are fixedly connected;

the strain gauge group is arranged on the elastic main beam and the elastic beam to form.

2. The planar series-connection uncoupled six-dimensional wrist force sensor according to claim 1, wherein: the frame of the fixed table without the T-shaped elastic branched chain is provided with a fixed through hole; the central loading platform is provided with mounting through holes which are uniformly distributed along the circumference by taking the axis of the central loading platform as the center and penetrate through the upper surface and the lower surface.

3. The planar series-coupled six-dimensional wrist force sensor according to claim 1, wherein: the elastic beam is provided with a dumbbell-shaped double-connection through hole which is formed by combining two circular through holes and a rectangular through hole; the floating beam is symmetrically provided with two rectangular through holes by using the central line of the elastic beam, one side of each rectangular through hole is superposed with the side surface of the elastic beam, the floating beam is divided into an inner floating beam and an outer floating beam by the rectangular through holes, the width of the outer floating beam is d1, the width of the inner floating beam is d2, and the d1 and the d2 can be unequal.

4. The planar series-connection uncoupled six-dimensional wrist force sensor according to claim 1, wherein: the inner side surface of the concave part in the inner and outer connecting bodies is close to the central loading platform and is provided with a certain gap; the inner sides of the four corners of the inner and outer connectors are rectangular abdicating notches matched with the four elastic main beams in shape, and the inner side faces of the inner and outer connectors are provided with certain gaps close to the side faces of the elastic main beams.

5. The planar series-coupled six-dimensional wrist force sensor according to claim 1, wherein: the fixing table, the inner and outer connecting bodies, the central loading table, the elastic main beam, the elastic beam of the T-shaped elastic branched chain and the floating beam are all integrally formed structures and are arranged on the same central plane in the thickness direction; the fixed platform, the internal and external connectors and the central loading platform are integrally connected in series with the elastic main beam through the T-shaped elastic branched chain.

6. The planar series-coupled six-dimensional wrist force sensor according to claim 1, wherein: the thicknesses of the fixed platform, the inner and outer connecting bodies, the elastic beams of the T-shaped elastic branched chains and the floating beams are equal and are D, the thickness of the elastic main beam is D, the thickness of the central loading platform is L, and D is less than D and less than L.

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