Three-dimensional force sense calibration platform and calibration method designed for intelligent tail end clamp

Abstract

The invention provides a three-dimensional force sense calibration platform and calibration method applied to an intelligent tail end clamp, the platform comprises a platform support column, a cross beam, a laser calibration mechanism, a clamp fixing base, a standard force sensor, a base, a pulley and a weight, the platform support column is fixed on the base through a bolt, the cross beam is fastened on the platform support column through a bolt, and the laser calibration mechanism is fixed on the platform support column through a bolt. Each cross beam is provided with a pulley, and the weight loading steel wire leads bypass the pulleys, so that simultaneous loading in three dimensions is realized. The calibration method comprises the steps of calibration platform debugging and three-dimensional force sensing clamp calibration. The coordinate axis of the force bearing point of the clamp is fixed in the calibration process, micro-size, small-range, high-resolution and high-precision three-dimensional force sense calibration detection can be achieved, simultaneous loading of three-dimensional force systems can be achieved, and cross samples in a three-dimensional space can be accurately obtained.

Description

Technical Field

[0001] The present invention belongs to the field of sensor measurement, and in particular relates to a three-dimensional force calibration platform and a calibration method applied to an intelligent end fixture. Background Art

[0002] Micro-operation and micro-assembly technology is one of the key technologies in the field of intelligent manufacturing. The force measurement of the actuator end fixture is one of the core difficulties in achieving precision operation in the microscopic field. In order to ensure the accuracy of force detection, it is necessary to conduct in-depth research on the force calibration detection system of the microstructure actuator end fixture. The directional and anti-interference sensing capabilities of the actuator end fixture come from the decoupling characteristics of its anisotropic microstructure. Since the elastic structure of the fixture not only has to withstand axial deformation, it must also maintain a certain stiffness in the radial direction. Therefore, the range and resolution of radial force sensing of the force measurement of the actuator end fixture will be much higher than that of axial force sensing. At present, there are few studies on the three-dimensional force calibration detection system of the microstructure actuator end fixture at home and abroad, and most of them are calibrated for general three-dimensional force sensors.

[0003] The calibration and testing of domestic three-dimensional force sensors mainly use hydraulic or electric one-dimensional loading equipment. The sensor direction and the position of the loading point are adjusted by tooling to achieve the application of loads in three directions, that is, calibration is achieved through independent discrete loading in three directions. This calibration method has poor calibration accuracy and the inability to load the three dimensions at the same time leads to large crosstalk. The immature calibration and testing technology has seriously lagged behind the development of domestic three-dimensional force sensors.

[0004] The Chinese patent application number 202111333167.6 discloses a load-adjustable three-dimensional force sensor calibration device, which uses a rotating table combination with two rotating axes perpendicular to each other to record force through a thrust gauge. During the calibration process, the coordinate axis of the force sensor force point on the rotating table is constantly changing. Since the three-dimensional force sensor has no channel to detect torque, it can only be subjected to force at a fixed point. That is, if the force point of the three-dimensional force sensor changes, the output voltage error generated by the torque will be superimposed on the measured force of each axis, resulting in inaccurate measurement values ​​of the three axes. This calibration method has a large error, and the calibration accuracy will be limited by the transmission accuracy of the thrust gauge, and the force value is difficult to trace. It is more suitable for the calibration of large-range and low-precision force sensors. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned existing three-dimensional force sensor calibration system. In combination with the structural characteristics of the microstructure actuator end fixture, a calibration platform and calibration method for the end actuator with three-dimensional force sensing function are proposed, and a calibration process is formulated.

[0006] The present invention provides a three-dimensional force calibration platform applied to an intelligent end fixture, wherein the platform comprises: a platform pillar, a crossbeam, a laser calibration mechanism, a fixture fixing base, a standard force sensor, a base, a pulley, and a weight, wherein the platform pillar is fixed to the base by bolts, the crossbeam is fastened to the platform pillar by bolts, a pulley is installed on each crossbeam, and the weight loading wire lead is passed around the pulley, thereby realizing simultaneous loading in three dimensions.

[0007] The fixture fixing base serves to connect the calibration platform base and the fixture. During calibration, the fixture is placed in the base groove, and two threaded positioning pins are passed through the base threaded holes and the fixture, and then tightened against the fixture to fix it in place. The fixture fixing base is fixed to the slider by bolts, and the slide rail that matches the slider is connected to the adjustable column, which can slide back and forth and adjust the height up and down, thereby realizing the centering calibration of the loading force in three directions.

[0008] The pulley is installed on the beam through the slider and the rail. The position of the pulley can be fine-tuned to align the clamp calibration direction. The pulley uses a V-groove bearing wheel, which has the advantages of low friction and strong load-bearing capacity.

[0009] The calibration platform uses a laser calibration mechanism to check the direction of the three-dimensional force calibration so that the weight wire rope coincides with the sensor calibration axis. The laser calibration mechanism includes a laser generator and a laser connector. The laser generator is installed on an adjustable column base through a laser connector. The selected laser generator has high concentricity, and its concentricity error is 0.1 milliradian. After being calibrated by the laser calibration mechanism, the inter-dimensional coupling error of the calibration system is less than 0.3%.

[0010] The present invention also provides a calibration method for a calibration platform of an end-effector fixture with a three-dimensional force sensing function, including calibration platform debugging and three-dimensional force sensing fixture calibration, evaluating the performance of force sensing to optimize its structure and ensure its measurement accuracy.

[0011] The beneficial effects of the present invention are as follows:

[0012] 1. The coordinate axis of the force bearing point of the fixture of the present invention remains unchanged during the calibration process;

[0013] 2. The present invention can realize micro-size, small range, high resolution and high precision three-dimensional force calibration detection;

[0014] 3. The three-dimensional load provided in the calibration process of the present invention is stable and the force value traceability path is clear;

[0015] 4. The present invention can realize simultaneous loading of a three-dimensional force system and can accurately obtain cross samples in a three-dimensional space;

[0016] 5. The present invention is aimed at the anisotropic three-dimensional force sensing end fixture, which has the calibration range and resolution adjustability under complex conditions;

[0017] 6. The present invention has a simple structure and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention:

[0019] Figure 1 is a structural diagram of a calibration platform according to an embodiment of the present invention;

[0020] Figure 2 This is a structural diagram of a fixture fixing base according to an embodiment of the present invention;

[0021] Figure 3 This is a structural diagram of an adjustment column of a fixture fixing base according to an embodiment of the present invention;

[0022] Figure 4 is a structural outline diagram of a pulley block according to an embodiment of the present invention;

[0023] Figure 5 It is a structural appearance diagram of the laser calibration mechanism according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] This embodiment provides a three-dimensional force calibration platform for an intelligent end fixture, the platform comprising: a platform pillar, a crossbeam, a laser calibration mechanism, a fixture fixing base, a standard force sensor, a base, a pulley, and a weight, wherein the platform pillar is fixed to the base by bolts, the crossbeam is fastened to the platform pillar by bolts, a pulley is installed on each crossbeam, and the weight loading wire leads pass around the pulley, thereby achieving simultaneous loading in three dimensions, such as Figure 1 As shown, the red box indicates the load in the X-axis direction, the purple box indicates the load in the Y-axis direction, and the blue box indicates the load in the Z-axis direction.

[0026] The fixture fixing base serves to connect the calibration platform base and the fixture, such as Figure 2As shown, it includes a through hole 1, a sensor 2, a threaded hole 3, a positioning pin 4, and a base 5. During calibration, the sensor fixture 6 is placed in the base groove, and two threaded positioning pins are passed through the base threaded hole and the fixture, and then tightened against the fixture to fix it in place. The fixture fixing base is fixed to the slider 7 by bolts, and the slide rail 8 matched with the slider is connected to the adjustable column 9, which can slide back and forth and adjust the height up and down, so as to realize the centering calibration of the loading force in three directions, as shown in FIG. Figure 3 shown.

[0027] The pulley 10 is mounted on the beam through the slider 11 and the slide rail 8. The position of the pulley can be fine-tuned to align the clamp calibration direction. The pulley is a V-grooved bearing wheel, which has the advantages of low friction and strong load-bearing capacity. Figure 4 As shown, the slide rail and the slide block are fixed by locking screws 12.

[0028] The calibration platform uses a laser calibration mechanism to check the direction of the three-dimensional force calibration so that the weight wire rope coincides with the sensor calibration axis. The laser calibration mechanism includes a laser generator 13 and a laser connector 14. The laser generator is installed on the base of an adjustable column 15 through a laser connector. The adjustable column 15 is fixed by a locking nut 16. The selected laser generator has high concentricity, and its concentricity error is 0.1 milliradian. After being calibrated by the laser calibration mechanism, the inter-dimensional coupling error of the calibration system is less than 0.3%. Figure 5 shown.

[0029] The present invention also provides a calibration method for a calibration platform of an end-effector fixture with a three-dimensional force sensing function, including calibration platform debugging and three-dimensional force sensing fixture calibration, evaluating the performance of force sensing to optimize its structure and ensure its measurement accuracy.

[0030] 1. Calibration platform debugging

[0031] Before conducting the calibration experiment, the calibration platform should be debugged to the best state. First, place the level ruler on the beams connected to the platform columns, adjust the fastening bolts, and level the beams to make the pulley block installation plane horizontal; then place the level ruler on the adjustment support of the fixture fixed base, and calibrate the platform level again. After two levelings, the level of the calibration platform should not exceed 10'.

[0032] Then adjust the XYZ load loading direction, use the laser to align each pulley block with the calibration direction of each dimension of the fixture, where the verticality error of the center line of the X-axis force axis to the fixture installation reference plane is less than 10', the parallelism error of the center line of the Y and Z-axis force axes to the fixture reference plane is less than 0.1mm, the height equality error of the center line of the Y and Z-axis force axes to the fixture reference plane is less than 0.04mm, the verticality error of the three axes of XYZ is less than 10', and the intersection error of the three axes of XYZ is less than 0.1mm.

[0033] During the calibration experiment, the standard weights used should be of M1 grade or above. When loading and unloading the weights, the wire rope will shake, causing errors. After the weights stabilize, the shaking angle shall not exceed 1 degree.

[0034] When calibrating the FX direction, install the standard force sensor on the fixture fixed base, connect the wire rope to the standard force sensor through the pulley in the positive direction of FX, and hang a 500g weight on the other end. After the weight is stable, record the output of the standard force sensor. Measure 10 times in a row, and the average output of the standard force sensor is 4.877N. Taking the gravity acceleration as 9.8N / s2, the relative error of the output load is 0.469%.

[0035] When static calibration is performed on the FYFZ direction, the remaining calibration steps are exactly the same as those for the FX direction. The relative error of the FY output load is 0.489%, and the relative error of the FZ output load is 0.581%.

[0036] The standard force sensor used is the Sparto SBT301-40A three-dimensional force sensor. Figure 5 shown.

[0037] 2. Calibration of 3D force sensing fixture

[0038] In order to enable the fixture to occupy an accurate spatial coordinate position on the calibration platform and keep it stable during the calibration process, the fixture must be accurately positioned and clamped.

[0039] The calibration steps of the three-dimensional force sensing fixture are as follows:

[0040] (1) Determine the direction of the fixture calibration force and the range of the fixture in each direction (0 to 5N);

[0041] (2) The one-dimensional Fx direction of the fixture calibration is divided into 1N equal intervals according to the range;

[0042] (3) Apply force to the calibration points of the fixture in order from small to large, and record the resistance value corresponding to each calibration point of the fixture;

[0043] (4) Unload the force at the calibration points of the fixture in order from large to small, and record the resistance value corresponding to each calibration point of the fixture;

[0044] (5) Steps (3) and (4) are repeated three times, and the average value is taken to obtain the linear fitting relationship between Rx and Fx at one-dimensional sample points;

[0045] (6) The two-dimensional Fx and Fz directions of the fixture calibration are divided into 1N equal intervals according to the range;

[0046] (7) Apply force to the calibration points of the fixture in order from small to large, and record the resistance value corresponding to each calibration point of the fixture;

[0047] (8) Unload the force at the calibration points of the fixture in descending order and record the resistance value corresponding to each calibration point of the fixture;

[0048] (9) Steps (8) and (9) are repeated three times, and the average value is taken to obtain the two-dimensional sample surface fitting relationship between Rz, Rx and Fz, Fx;

[0049] (10) The three-dimensional Fx, Fy, and Fz directions of the fixture calibration are divided into 1N equal intervals according to the range;

[0050] (11) Apply force to the calibration points of the fixture in order from small to large, and record the resistance value corresponding to each calibration point of the fixture;

[0051] (12) Unload the force at the calibration points of the fixture from large to small, and record the resistance value corresponding to each calibration point of the fixture;

[0052] (13) Steps (11) and (12) are repeated three times to obtain the three-dimensional sample point surface fitting relationship between Rz, Ry, Rx and Fx, Fy, Fz.

[0053] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-dimensional force calibration platform for intelligent end fixture design, characterized in that: The platform includes: platform pillars, crossbeams, laser calibration mechanism, fixture fixing base, standard force sensor, base, pulleys, and weights, wherein the platform pillars are fixed to the base by bolts, the crossbeams are fastened to the platform pillars by bolts, a pulley is installed on each crossbeam, and the weight loading wire lead is passed around the pulley, thereby achieving simultaneous loading in three dimensions.

2. According to claim 1, a three-dimensional force calibration platform for intelligent end fixture design is characterized in that: The fixture fixing base will play the role of connecting the calibration platform base and the fixture.

3. A three-dimensional force calibration platform for intelligent end fixture design according to claim 2, characterized in that: The fixture fixing base is fixed to the slider by bolts, and the slide rail matched with the slider is connected to the adjustable column, which can slide back and forth and adjust the height up and down, so as to realize the centering calibration of the loading force in three directions.

4. The three-dimensional force calibration platform for intelligent end fixture design according to claim 3 is characterized in that: The pulley is installed on the beam through a slider and a slide rail, and the position of the pulley can be fine-tuned to align with the calibration direction of the fixture.

5. The three-dimensional force calibration platform for intelligent end fixture design according to claim 1 is characterized in that: The laser calibration mechanism comprises a laser generator and a laser connecting piece.

6. A calibration method for a three-dimensional force calibration platform for intelligent end fixture design according to any one of claims 1 to 5, characterized in that: It includes calibration platform debugging steps and three-dimensional force sensing fixture calibration steps.

7. The calibration method of a three-dimensional force calibration platform for intelligent end fixture design according to claim 6 is characterized in that: The calibration platform debugging steps include: First, place the level ruler on the beams connected to the platform columns, adjust the fastening bolts to level the beams, and make the pulley assembly installation plane level; then place the level ruler on the adjustment support of the fixture fixed base, and calibrate the platform level again. After two levelings, the calibration platform level should not exceed 10'; Then adjust the XYZ load loading direction and use the laser to align each pulley block with the calibration direction of each dimension of the fixture; Calibration F X When the force sensor is in the positive direction, install the standard force sensor on the fixture fixed base, connect the wire rope to the standard force sensor through the pulley in the positive direction of FX, and hang a 500g weight on the other end. After the weight is stable, record the output of the standard force sensor and measure 10 times continuously. F Y F Z When static calibration is performed in the direction, the remaining calibration steps are the same as those in F X The direction is exactly the same.

8. The calibration method of a three-dimensional force calibration platform for intelligent end fixture design according to claim 6 is characterized in that: The three-dimensional force sensing fixture calibration steps are as follows: (1) Determine the direction of the fixture’s calibration force and the range of the fixture in each direction; (2) Divide the one-dimensional Fx direction of the fixture calibration into 1N equal intervals according to the range to determine the fixture calibration points; (3) Apply force to the calibration points of the fixture in order from small to large, and record the resistance value corresponding to each calibration point of the fixture; (4) Unload the force at the calibration points of the fixture in order from large to small, and record the resistance value corresponding to each calibration point of the fixture; (5) Steps (3) and (4) are repeated three times, and the average value is taken to obtain the linear fitting relationship between Rx and Fx at one-dimensional sample points; (6) Divide the two-dimensional Fx and Fz directions of the fixture calibration into 1N equal intervals according to the range to determine the fixture calibration points; (7) Apply force to the calibration points of the fixture in order from small to large, and record the resistance value corresponding to each calibration point of the fixture; (8) Unload the force at the calibration points of the fixture in descending order and record the resistance value corresponding to each calibration point of the fixture; (9) Steps (8) and (9) are repeated three times, and the average value is taken to obtain the two-dimensional sample surface fitting relationship between Rz, Rx and Fz, Fx; (10) The three-dimensional Fx, Fy, and Fz directions of the fixture calibration are divided into 1N equal intervals according to the measuring range to determine the fixture calibration points.

9. The calibration method of a three-dimensional force calibration platform for intelligent end fixture design according to claim 7 is characterized in that: During the calibration experiment, the standard weights used should be of grade M1 or above.

10. The calibration method of a three-dimensional force calibration platform for intelligent end fixture design according to claim 7, characterized in that: The standard force sensor is a Sparto SBT301-40A three-dimensional force sensor.

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