CN111152201A - Variable stiffness and six-dimensional force sensing passive compliant device for automated assembly - Google Patents
Variable stiffness and six-dimensional force sensing passive compliant device for automated assembly Download PDFInfo
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- CN111152201A CN111152201A CN202010051990.7A CN202010051990A CN111152201A CN 111152201 A CN111152201 A CN 111152201A CN 202010051990 A CN202010051990 A CN 202010051990A CN 111152201 A CN111152201 A CN 111152201A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/10—Programme-controlled manipulators characterised by positioning means for manipulator elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
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Abstract
The invention discloses a passive compliant device with variable rigidity and six-dimensional force sensing for automatic assembly, which comprises a static platform, four beam assemblies with variable rigidity and a movable platform, wherein the four beam assemblies with variable rigidity are arranged on the static platform; the static platform is fixedly connected with the tail end of the robot; the movable platform is arranged in the middle of the inside of the static platform and is fixedly connected with clamps such as a manipulator and the like; one ends of the four variable stiffness beam assemblies are fixedly connected with the static platform, and the other ends of the four variable stiffness beam assemblies are fixedly connected with the movable platform; the four variable stiffness beam assemblies are arranged around the movable platform, form a square shape in an end-to-end circulating mode and can elastically deform in a direction perpendicular to the respective axial direction; two strain gauges are attached to the mutually vertical surfaces of each variable stiffness beam assembly and used for measuring the force and moment of the movable platform in different directions; the device can achieve a certain passive compliance effect under the action of six-dimensional force and torque, the compliance characteristic is adjustable, the six-dimensional force sensing is achieved, the overall structure is simple and compact, the space utilization rate is high, and the compliance performance in a small range is good.
Description
Technical Field
The invention belongs to the field of automatic assembly of robots, and particularly relates to a rigidity-variable passive compliant device with six-dimensional force sensing for automatic assembly or butt joint of robots.
Background
In the automatic assembly or butt joint process of the robot, the positioning error of the robot is 1-2 orders of magnitude higher than the matching error between the assembled objects due to various errors of the robot. If the assembly is forced by neglecting such error relationship in the assembly process, the assembly cannot be performed, and even the surface of the part to be assembled, the assembly actuator and the robot may be damaged. The improvement of the positioning precision of the robot and the improvement of the motion precision of the assembly process by adopting an advanced control technology are difficult to achieve from the structural aspect, so a compliant device needs to be arranged between the tail end of the robot and a clamp such as a manipulator. At present, the robot flexible assembly method has active flexibility and passive flexibility, wherein: the active compliance mainly focuses on the interaction between force and the environment, the contact environment is sensed by the force sensor, and the assembly is completed by combining a corresponding control method, but the method has high requirement on the precision of the sensor and has a complex control algorithm; the passive compliance mainly utilizes a specific structure to make passive pose adjustment on contact collision force in the assembly process, so that a certain compliance is generated to finish the assembly process, but the mode completely depends on the structure of the passive compliance, lacks of active adaptability to a complex environment and has certain limitation.
Patent CN1045515192A provides a towards passive gentle and agreeable device of automatic assembly or butt joint, when the activity body in the device received the power and the rotation moment of horizontal plane, the power that will receive the activity body through the knock pin with the help of placing in the inside spring of body with the moment offset to reach the passive gentle and agreeable effect of the little position error of horizontal plane direction, though the device also possesses certain gentle and agreeable characteristic and adjusts and install a dimensional force sensor, its passive gentle and agreeable effect is limited, only can be used for the plane gentle and agreeable, can not be applied to the assembly task that has the pivot angle deviation. Patent 108908395a proposes a multi-directional passive compliance device for robot force control, which is mainly used in the occasions of robot grinding and polishing, when the central shaft of the device is subjected to normal force and tangential force, the central shaft is slightly deflected and axially displaced by means of an elastic element, thereby completing the grinding task, the rigidity characteristic of the device is not adjustable, and the compliance range is large, which is not suitable for complex assembly task.
Disclosure of Invention
The invention aims to provide a rigidity-variable and six-dimensional force-sensing passive compliance device for automatic assembly or butt joint of a robot, so as to realize passive compliance of tiny pose errors of parts to be assembled in the automatic assembly process of the robot.
The technical solution for realizing the purpose of the invention is as follows:
a passive compliant device with variable rigidity and six-dimensional force sensing for automatic assembly or butt joint of a robot comprises a static platform, a first variable rigidity beam assembly, a second variable rigidity beam assembly, a third variable rigidity beam assembly, a fourth variable rigidity beam assembly and a movable platform;
the movable platform is arranged in the middle of the inside of the static platform; one ends of the four variable stiffness beam assemblies are fixedly connected with the static platform, and the other ends of the four variable stiffness beam assemblies are fixedly connected with the movable platform; the four variable stiffness beam assemblies are arranged on the periphery of the static platform and form a square shape in an end-to-end circulating manner; the axial directions of the four variable stiffness beam assemblies are parallel to the corresponding side lines of the movable platform, and the variable stiffness beam assemblies can elastically bend and deform along the directions perpendicular to the respective axial directions and are used for passively smoothing the pose of the movable platform; the first variable stiffness beam assembly and the third variable stiffness beam assembly form a set of variable stiffness beam assemblies which are parallel to each other, and two strain gauges on the set of variable stiffness beam assemblies are attached by adopting a method comprising the following steps: the included angles between the axial directions of the two strain gauges and the axial direction of the variable stiffness beam assembly are both 45 degrees, and the deviation is opposite; the second variable stiffness beam assembly and the fourth variable stiffness beam assembly form another set of parallel variable stiffness beam assemblies, and two strain gauges on the set of variable stiffness beam assemblies are attached by one method: the two strain gauges are axially parallel, and the axial included angles of the two strain gauges and the axial included angle of the variable stiffness beam assembly are 45 degrees and have the same deviation.
Compared with the prior art, the invention has the following remarkable advantages:
(1) the micro pose of the movable platform can be adjusted by elastic deformation of the variable-stiffness beam assembly, so that the device is ensured to have good small-range compliance performance;
(2) through the arrangement of the strain gauge, the magnitude of force and moment applied to the movable platform can be collected, and real-time force and moment information is provided for the active compliance control system;
(3) the beam in the variable-rigidity beam assembly is matched with the screw rod, so that the rigidity characteristic of the whole device can be adjusted to meet the requirements of assembly elements and relative positioning precision change;
(4) the whole device has compact structure and can realize the miniaturization of the device.
Drawings
Fig. 1 is an isometric view of the overall structure of the device of the present invention.
FIG. 2 is a schematic diagram of an embodiment of the overall structure of the apparatus of the present invention.
Figure 3 is a cross-sectional view of the screw in engagement with the beam.
Fig. 4 is an isometric view of a beam.
Fig. 5 is a front view of the beam.
Fig. 6 is a cross-sectional view at a thicker internally threaded tube on a beam.
Fig. 7 is a cross-sectional view at a thinner internally threaded tube on a beam.
Fig. 8 is an isometric view of an intermediate connector.
Fig. 9 is an isometric view of a one-way unloading link.
FIG. 10 is a plan view schematic of a one-way unloader link;
FIG. 11 is an equivalent schematic of a one-way unloader link;
fig. 12 is a schematic top view of the device in different directions of force and moment.
Fig. 13 is a side view of the device in different directions for force and moment.
Detailed Description
The invention is further described with reference to the following figures and embodiments.
With reference to fig. 1 to 11, the variable-stiffness and six-dimensional force sensing passive compliant device for automatic robot assembly or docking of the present invention includes a static platform 1, a first variable-stiffness beam assembly 2, a second variable-stiffness beam assembly 3, a third variable-stiffness beam assembly 4, a fourth variable-stiffness beam assembly 5, and a moving platform 6;
the movable platform 6 is arranged in the middle of the inside of the static platform 1; and the bottom surface and the side surface of the movable platform 6 are not contacted with the inner side surface and the inner bottom surface of the static platform, so that a certain gap is kept for the movable platform 6 to perform micro pose adjustment. The static platform 1 is used for being fixedly connected with the tail end of the assembling robot; one ends of the four variable stiffness beam assemblies are fixedly connected with the static platform 1 through screws, and the other ends of the four variable stiffness beam assemblies are fixedly connected with the movable platform 6 through screws; the movable platform 6 is used for being fixedly connected with a clamping device such as a manipulator. The four variable stiffness beam assemblies are arranged around the movable platform 6 and form a square shape in an end-to-end circulating manner; the axial directions of the four variable stiffness beam assemblies are parallel to corresponding side lines of the movable platform 6, and the four variable stiffness beam assemblies can elastically bend and deform along the axial direction perpendicular to the variable stiffness beam assemblies and are used for compensating pose errors of the movable platform 6; wherein the first variable stiffness beam assembly 2 is axially parallel to the third variable stiffness beam assembly 4; the second variable stiffness beam assembly 3 is axially parallel to the fourth variable stiffness beam assembly 5; two strain gauges are arranged on each variable stiffness beam assembly 2 and attached to two mutually perpendicular faces of the variable stiffness beam assembly 2.
The first variable stiffness beam assembly 2 and the third variable stiffness beam assembly 4 form a group of variable stiffness beam assemblies which are parallel to each other, and two strain gauges on the group of variable stiffness beam assemblies are attached by one method. The second variable stiffness beam assembly 3 and the fourth variable stiffness beam assembly 5 form another set of parallel variable stiffness beam assemblies, and two strain gauges on the set of variable stiffness beam assemblies are attached by another method:
the first group of pasting methods: the axial directions of the two strain gauges are 90 degrees, the axial included angles of the two strain gauges and the axial direction of the variable stiffness beam assembly 2 are 45 degrees, and the deviation is opposite: that is, the axial included angle between one strain gauge and the axial direction of the variable stiffness beam assembly 2 deviates to the left, and the axial included angle between the other strain gauge and the axial direction of the variable stiffness beam assembly 2 deviates to the right;
the second group of pasting methods: the two strain gauges are axially parallel, and the axial included angles of the two strain gauges and the axial included angle of the variable stiffness beam assembly 3 are 45 degrees and are deviated to the same angle.
On the first variable stiffness beam assembly 2 and the third variable stiffness beam assembly 4, one strain gauge parallel to the upper surface of the movable platform 6 is taken to form a group of strain gauges respectively, and the strain gauges are used for measuring force perpendicular to the axial direction of the variable stiffness beam assembly 2; on the second variable stiffness beam assembly 3 and the fourth variable stiffness beam assembly 5, one strain gauge parallel to the upper surface of the movable platform 6 is taken to form a group of strain gauges respectively, and the strain gauges are used for measuring the force vertical to the axial direction of the variable stiffness beam assembly 3; on the four variable stiffness beam assemblies, one strain gauge vertical to the upper surface of the movable platform 6 is taken to form a group of strain gauges for measuring the force vertical to the direction of the upper surface of the movable platform 6; on the second variable stiffness beam assembly 3 and the fourth variable stiffness beam assembly 5, one strain gauge vertical to the upper surface of the movable platform 6 is taken to form a group of strain gauges for measuring the rotation moment around the direction vertical to the axial direction of the variable stiffness beam 2; on the first variable stiffness beam assembly 2 and the third variable stiffness beam assembly 4, one strain gauge vertical to the upper surface of the movable platform 6 is taken to form a group of strain gauges for measuring the rotation moment around the direction vertical to the axial direction of the variable stiffness beam 3; and on the four variable stiffness beam assemblies, a strain foil parallel to the upper surface of the movable platform 6 is taken to form a group of strain foils for measuring the rotation moment around the direction vertical to the upper surface of the movable platform 6.
Further, the four variable-rigidity beam assemblies are identical in structure and comprise a screw rod 2-1, a beam 2-2, an intermediate connecting piece 2-3 and a one-way unloading connecting piece 2-4; one end of the beam 2-2 is fixedly connected with the static platform 1 through a screw, and the other end of the beam is fixedly connected with the middle connecting piece 2-3 through a screw; one end of the one-way unloading connecting piece 2-4 is fixedly connected with the middle connecting piece 2-3 through a bolt and a nut, and the other end of the one-way unloading connecting piece is fixedly connected with the movable platform 6 through a screw; the external thread of the screw 2-1 is matched with the internal thread of the beam 2-2, and the extending length of the screw 2-1 can be adjusted to change the rigidity characteristic of the whole beam 2-2; when the movable platform 6 is subjected to a force parallel to the axial direction of the variable stiffness beam assembly 2 on the corresponding side, the one-way unloading connecting piece 2-4 of the variable stiffness beam assembly 2 on the side is subjected to a slight displacement parallel to the axial direction of the variable stiffness beam assembly 2 on the side, so that the variable stiffness beam assembly 2 on the side is not stressed.
Further, the beam 2-2 is integrally processed and comprises a fixed block 2-2-1, a round pipe 2-2-2 and a wing plate 2-2-4; a threaded hole is processed in the fixed block 2-2-1 and used for fixedly connecting the beam 2-2 with the static platform 1 through a screw; one end of the round tube 2-2-2 is connected with the fixed block 2-2-1. Four wing plates 2-2-4 are arranged around the round pipe 2-2-2, and the four wing plates 2-2-4 are distributed in a cross shape and used for adhering strain gauges; one end of the wing plate 2-2-4 is connected with the fixed block 2-2-1, and the other end is provided with a mounting hole for connecting with the middle connecting piece 2-3. The outer wall of the side, close to the connecting piece 2-3, of the circular tube 2-2-2 is provided with the groove 2-2-3, so that the wall of the side circular tube 2-2-2 is thin and has low rigidity, the beam 2-2 has good elastic deformation capability under stress, and the wall of the side circular tube close to the fixed block 2-2-1 is thick and has high rigidity, and the beam 2-2 has certain load bearing capability.
Furthermore, a through hole is formed in the center of the screw rod 2-1, and the length of the screw rod 2-1 is larger than that of the internal thread round pipe structure on the beam 2-2. The external thread of the screw rod 2-1 is always matched with the internal thread of the circular tube 2-2-2 on the beam 2-2 close to the fixed block 2-2-1 side, and the rigidity characteristic of the beam 2-2 is basically unchanged. Only when the screw 2-1 is close to the groove 2-2-3 in the beam 2-2 does the stiffness properties of the entire beam 2-2 start to change. Along with the increase of the screwing length of the screw 2-1, the wall thickness of an internal thread circular pipe at the groove 2-2-3 on the beam 2-2 is increased in a phase-changing manner, so that the rigidity of the whole beam 2-2 is increased, the elastic deformation of the beam 2-2 is reduced under the action of the same load, and the pose compensation range of the ground moving platform 6 is correspondingly reduced. Thus, the stiffness characteristics of the beam 2-2 can be adjusted according to the pose compensation range requirements of a particular automated assembly task.
Further, the unidirectional unloading link 2-4 can perfectly cancel the load force parallel to the axial direction (Y direction in fig. 2) of the variable stiffness beam assembly 2 and perfectly transmit the load force perpendicular to the axial direction (X direction in fig. 2) of the variable stiffness beam assembly 2 and perpendicular to the upper surface direction (Z direction) of the movable platform 6 by referring to the principle design of the circular arc flexible hinge and the parallel hinge four-bar mechanism;
the unidirectional unloading connecting piece 2-4 is provided with connecting blocks 2-40, and the connecting blocks 2-40 are used for fixing the movable platform 6; four first round holes 2-41 are arranged on the one-way unloading connecting piece 2-4, the four first round holes 2-41 form a rectangular distribution, and the long side direction of the rectangle is vertical to the axial direction of the variable stiffness beam component 2 at the side; the first round holes 2-41 parallel to the long side direction of the rectangle are connected through first through grooves 2-42, the two first round holes 2-41 close to the connecting blocks 2-40 are connected through second through grooves 2-43, and the two first round holes 2-41 far away from the connecting blocks 2-40 are not connected. The outer wall of the one-way unloading connecting piece 2-4 is provided with four first semicircular holes 2-44 near the first circular holes 2-41; the four first semicircular holes 2-44 and the four first circular holes 2-41 form a primary flexible quadrilateral hinge 2-4-1. Two second semicircular holes 2-45 are formed in the first through grooves 2-42 close to the connecting blocks 2-40, and the second semicircular holes 2-45 are concave to the inner sides of the rectangles; the inner sides of the four first round holes 2-41 are provided with four second round holes 2-46, the four second round holes 2-46 form a rectangular distribution, the second round holes 2-46 parallel to the long side direction of the rectangle are connected through third through grooves 2-47, two second round holes far away from the fixed block 2-40 are connected through fourth grooves 2-48, and two second round holes close to the fixed block 2-40 are not connected; two second round holes 2-46 far away from the connecting blocks 2-40 are close to the first round holes 2-41 on the corresponding sides; two second round holes 2-46 close to the connecting blocks 2-40 are close to second semicircular holes 2-45 on the corresponding sides; two-stage flexible quadrilateral hinges 2-4-2 are formed between the first round holes 2-41 and the second round holes 2-46 and between the second semicircular holes 2-45 and the second round holes 2-46. A two-stage flexible quadrilateral hinge structure is formed, which aims to improve the unloading capacity of the one-way unloading connecting piece 2-4 and enable the structure to be compact. The center of the unidirectional unloading connecting piece 2-4 is provided with two mounting holes for fixedly connecting with the middle connecting piece 2-3. When the movable platform 6 is subjected to a force F (Y direction in fig. 11) perpendicular to the axial direction of the first variable stiffness beam assembly 2, the flexible hinges at the primary flexible quadrilateral hinge 2-4-1 and the secondary flexible quadrilateral hinge 2-4-2 generate tiny angular displacement by elastic torsional deformation around the axes thereof, so that the middle part of the one-way unloading connecting piece 2-4 generates tiny displacement along the direction of the force F, and finally the force F is not transmitted to the beam 2-2 on the first variable stiffness beam assembly 2; when the unidirectional unloading joint part 2-4 is acted by forces in two other directions (X or Z directions in figure 11) which are perpendicular to the above directions, the unidirectional unloading joint part has certain rigidity in the two directions and is not easy to deform, so that the load forces obtained in the two directions can be well transmitted.
Further, a resistance strain gauge R21 and a resistance strain gauge R22 are attached to the side face of the perpendicular wing plate on the beam 2-2 of the first variable stiffness beam assembly 2, the strain gauge R21 is attached to the right side of the first variable stiffness beam assembly 2 in the axial direction, and the strain gauge R22 is attached to the left side of the first variable stiffness beam assembly 2 in the axial direction by 45 °; a resistance strain gauge R31 and a resistance strain gauge R32 are attached to the side face of a wing plate, perpendicular to each other, of the beam 2-2 of the second variable stiffness beam assembly 3, and the strain gauge R31 and the strain gauge R32 are attached to the left of the axis of the second variable stiffness beam assembly 3 by 45 degrees; a resistance strain gauge R41 and a resistance strain gauge R42 are attached to the side face, perpendicular to each other, of a wing plate on the beam 2-2 of the third variable stiffness beam assembly 4, the strain gauge R41 is attached to the right side of the third variable stiffness beam assembly 4 in the axial direction by 45 degrees, and the strain gauge R42 is attached to the left side of the third variable stiffness beam assembly 4 in the axial direction by 45 degrees; the resistance strain gauge R51 and the resistance strain gauge R52 are attached to the mutually perpendicular wing plate sides of the beams 2-2 of the fourth variable stiffness beam assembly 5, and both the strain gauge R51 and the strain gauge R52 are attached to the fourth variable stiffness beam assembly 5 at an angle of 45 ° to the left.
The process of the device of the present invention for realizing passive compliance and six-dimensional force sensing under the action of forces and moments in different directions is described with reference to fig. 12 and 13. Firstly, a space coordinate system (shown in fig. 12 and 13) is constructed by taking a plane where the axial direction of the first variable stiffness beam assembly 2 and the axial direction of the fourth variable stiffness beam assembly 5 are located as an XOY plane of the coordinate system, locating a coordinate origin O at the geometric center of the plane, taking the direction parallel to the axial direction of the fourth variable stiffness beam assembly 5 as the positive direction of an X axis, taking the direction parallel to the axial direction of the first variable stiffness beam assembly 2 as the positive direction of a Y axis, and taking the normal direction of the XOY plane as the positive direction of a Z axis;
when the movable platform 6 is subjected to a force Fx along the X direction, the beams 2-2 on the first variable stiffness beam assembly 2 and the third variable stiffness beam assembly 4 are subjected to slight elastic deformation, the beams 2-2 on the second variable stiffness beam assembly 3 and the fourth variable stiffness beam assembly 5 are not subjected to force deformation due to the action of the one-way unloading connecting piece, and then the movable platform 6 is subjected to slight displacement along the X direction, so that the flexible effect of the stress of the device in the X direction is achieved; at this time, the resistance value of the strain gauge R21 is decreased, the resistance value of the strain gauge R41 is increased, and the resistance values of the strain gauge R31 and the strain gauge R51 are substantially unchanged, so that the difference between the increase in the resistance value of the strain gauge R41 and the decrease in the resistance value of the strain gauge R21 is used as a criterion for evaluating the magnitude of the force Fx along the X direction, and a corresponding voltage change is measured by a bridge circuit.
Further, when the movable platform 6 is subjected to a force Fy along the Y direction, the beams 2-2 on the second variable stiffness beam assembly 3 and the fourth variable stiffness beam assembly 5 are subjected to slight elastic deformation, the beams 2-2 on the first variable stiffness beam assembly 2 and the third variable stiffness beam assembly 4 are not subjected to force deformation due to the action of the one-way unloading connecting piece, and then the movable platform 6 is subjected to slight displacement along the Y direction, so that the compliant effect of the stress of the device in the Y direction is achieved; at this time, the resistance value of the strain gauge R31 is decreased, the resistance value of the strain gauge R51 is increased, and the resistance values of the strain gauge R31 and the strain gauge R51 are substantially unchanged, so that the difference between the increase in the resistance value of the strain gauge R31 and the decrease in the resistance value of the strain gauge R51 is used as a criterion for evaluating the magnitude of the force Fy along the Y direction, and a corresponding voltage change is measured by a bridge circuit.
Furthermore, when the movable platform 6 is subjected to a force Fz along the Z direction, the beams 2-2 on the four variable stiffness beam assemblies are subjected to slight elastic deformation, and then the movable platform 6 is subjected to slight displacement along the Z direction, so that the flexible effect of the stress of the device in the Z direction is achieved; at this time, the resistance values of the strain gauge R22 and the strain gauge R52 are reduced, and the resistance values of the strain gauge R32 and the strain gauge R42 are increased, so that the difference between the total resistance value increase of the strain gauge R32 and the strain gauge R42 and the total resistance value decrease of the strain gauge R22 and the strain gauge R52 is used as a criterion for evaluating the magnitude of the force Fz in the Z direction, and the corresponding voltage change is measured by a bridge circuit.
Further, when the movable platform 6 is subjected to a moment Mx along the X direction, the beams 2-2 on the first variable stiffness beam assembly 2 and the third variable stiffness beam assembly 4 are subjected to slight elastic deformation, and then the movable platform 6 slightly rotates around the X direction, so that the flexible effect of the device on the moment along the X direction is achieved; at this time, the resistance value of the strain gauge R22 increases, and the resistance value of the strain gauge R42 increases, so that the sum of the increase in the resistance value of the strain gauge R22 and the increase in the resistance value of the strain gauge R42 is used as a criterion for evaluating the magnitude of the moment Mx in the X direction, and a corresponding voltage change is obtained by means of measurement of a bridge circuit.
Further, when the movable platform 6 is subjected to a moment My along the Y direction, the beams 2-2 on the second variable stiffness beam assembly 3 and the fourth variable stiffness beam assembly 5 are subjected to slight elastic deformation, and then the movable platform 6 slightly rotates around the Y direction, so that the flexible effect that the device is subjected to the moment in the Y direction is achieved; at this time, the resistance value of the strain gauge R32 is reduced, and the resistance value of the strain gauge R52 is reduced, so that the sum of the reduction of the resistance value of the strain gauge R32 and the reduction of the resistance value of the strain gauge R52 is used as a criterion for evaluating the magnitude of the moment My in the Y direction, and the corresponding voltage change is obtained by means of the measurement of the bridge circuit.
Furthermore, when the movable platform 6 is subjected to a moment Mz along the Z direction, the beams 2-2 on the four variable-rigidity beam assemblies are subjected to slight elastic deformation, and then the movable platform 6 slightly rotates around the Z direction, so that the flexible effect of the device on the Z direction under the moment is achieved; at this time, the resistance values of the strain gauge R21 and the strain gauge R41 are increased, and the resistance values of the strain gauge R31 and the strain gauge R51 are decreased, so that the difference between the total resistance value increase of the strain gauge R21 and the strain gauge R41 and the total resistance value decrease of the strain gauge R31 and the strain gauge R51 is used as a criterion for judging the magnitude of the moment Mz along the Z direction, and the corresponding voltage change is measured by a bridge circuit.
And finally, the voltage variation information of the 8 resistance strain gauges is collected in groups to obtain the force and moment applied to the movable platform 6, and then the force and moment information is provided for an active control system of the robot for automatic assembly, so that the robot can conveniently carry out an active compliant assembly process.
The device of the invention realizes a certain range of passive compliance effect under the action of forces and moments in different directions on the movable platform. In the automatic assembly process of the robot, due to the existence of various errors of the robot, micro deviation occurs between positions and postures of parts to be assembled, the mechanical arm and other clamping devices can be subjected to assembly resistance, the resistance can enable the movable platform 6 to be subjected to the action of force and moment, the movable platform 6 can be allowed to slightly displace or rotate by virtue of elastic deformation of the variable stiffness beam assembly in the device, and the positions and postures of the parts to be assembled can be passively adjusted to complete the assembly task. Therefore, the device can realize the passive compliance function in a small range of multiple directions. In addition, the resistance strain gauge attached to the device can accurately obtain the magnitude information of the force and the moment received in the assembly process, and the information can be used for the active flexible assembly process of the robot.
Claims (5)
1. A passive compliant device with variable rigidity and six-dimensional force sensing for automatic assembly or butt joint of a robot is characterized by comprising a static platform (1), a first variable rigidity beam assembly (2), a second variable rigidity beam assembly (3), a third variable rigidity beam assembly (4), a fourth variable rigidity beam assembly (5) and a movable platform (6);
the movable platform (6) is arranged in the middle of the inside of the static platform (1); one ends of the four variable stiffness beam assemblies are fixedly connected with the static platform (1), and the other ends of the four variable stiffness beam assemblies are fixedly connected with the movable platform (6); the four variable stiffness beam assemblies are arranged around the movable platform (6) and form a square shape in an end-to-end circulating manner; the axial directions of the four variable stiffness beam assemblies are parallel to corresponding side lines of the movable platform (6), and the variable stiffness beam assemblies can elastically bend and deform along the directions perpendicular to the respective axial directions and are used for compensating pose errors of the movable platform (6); the first variable stiffness beam assembly (2) and the third variable stiffness beam assembly (4) form a group of variable stiffness beam assemblies which are parallel to each other, and two strain gauges on the group of variable stiffness beam assemblies adopt an attaching method: the included angles between the axial directions of the two strain gauges and the axial direction of the variable stiffness beam assembly (2) are 45 degrees and are opposite in deviation; the second variable stiffness beam assembly (3) and the fourth variable stiffness beam assembly (5) form another set of parallel variable stiffness beam assemblies, and two strain gauges on the set of variable stiffness beam assemblies adopt a pasting method: the two strain gauges are axially parallel, and the axial included angles of the two strain gauges and the axial included angle of the variable stiffness beam assembly (3) are 45 degrees and have the same deviation.
2. The passive compliant device of claim 1 wherein the four variable stiffness beam assemblies are identical in structure and each comprises a screw (2-1), a beam (2-2), an intermediate connection (2-3), and a one-way dump link (2-4); one end of the beam (2-2) is fixedly connected with the static platform (1), and the other end of the beam is fixedly connected with the middle connecting piece (2-3); one end of the one-way unloading connecting piece (2-4) is fixedly connected with the middle connecting piece (2-3), and the other end of the one-way unloading connecting piece is fixedly connected with the movable platform (6); the external thread of the screw (2-1) is matched with the internal thread of the beam (2-2); when the movable platform (6) is subjected to a force parallel to the axial direction of the variable-stiffness beam assembly (2) on the corresponding side, the one-way unloading connecting piece (2-4) of the variable-stiffness beam assembly (2) on the side is subjected to a slight displacement parallel to the axial direction of the variable-stiffness beam assembly (2) on the side, so that the variable-stiffness beam assembly (2) on the side is not stressed.
3. The passive compliance device according to claim 1, wherein the beam (2-2) comprises a fixed block (2-2-1), a round tube (2-2-2), a wing plate (2-2-4); one end of the round pipe (2-2-2) is connected with the fixed block (2-2-1); four wing plates (2-2-4) are arranged around the circular tube (2-2-2), and the four wing plates (2-2-4) are distributed in a cross shape; the outer wall of the round pipe (2-2-2) close to the connecting piece (2-3) is provided with a groove (2-2-3).
4. The passive compliant device according to claim 1, wherein the screw (2-1) is centrally provided with a through hole.
5. The passive compliant device according to claim 1, wherein the unidirectional unloading connecting piece (2-4) is provided with a connecting block (2-40), the unidirectional unloading connecting piece (2-4) is provided with four first round holes (2-41), the four first round holes (2-41) form a rectangular distribution, and the long side direction of the rectangle is perpendicular to the axial direction of the variable stiffness beam assembly (2) at the side; the first round holes (2-41) parallel to the long side direction of the rectangle are connected through first through grooves (2-42), the two first round holes (2-41) close to the connecting blocks (2-40) are connected through second through grooves (2-43), and the two first round holes (2-41) far away from the connecting blocks (2-40) are not connected; four first semicircular holes (2-44) are arranged on the outer wall of the one-way unloading connecting piece (2-4) near the first circular holes (2-41); a primary flexible quadrilateral hinge (2-4-1) is formed between the four first semicircular holes (2-44) and the four first circular holes (2-41); two second semicircular holes (2-45) are formed in the first through grooves (2-42) and close to the connecting blocks (2-40), and the second semicircular holes (2-45) are concave to the inner sides of the rectangles; the inner sides of the four first round holes (2-41) are provided with four second round holes (2-46), the four second round holes (2-46) are distributed in a rectangular shape, the second round holes (2-46) parallel to the long side direction of the rectangular shape are connected through third through grooves (2-47), two second round holes far away from the fixed block (2-40) are connected through fourth grooves (2-48), and two second round holes close to the fixed block (2-40) are not connected; two second round holes (2-46) far away from the connecting blocks (2-40) are close to the first round holes (2-41) on the corresponding sides; two second round holes (2-46) close to the connecting blocks (2-40) are close to second semicircular holes (2-45) on the corresponding sides; two-level flexible quadrilateral hinges (2-4-2) are formed between the first round holes (2-41) and the second round holes (2-46) and between the second semicircular holes (2-45) and the second round holes (2-46).
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| CN113967924A (en) * | 2021-10-28 | 2022-01-25 | 郑州轻工业大学 | Self-adaptive compliant feature test analysis platform for thin-wall fragile part operation manipulator |
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