A method for automatic calibration of a net weight multi-dimensional force sensor

Abstract

The present application relates to the field of sensor calibration machine, provide a kind of net weight formula multi-dimensional force sensor automatic calibration method, comprising: step S1, automatic calibration machine timing self-calibration;Step S2, install the multi-dimensional force sensor to be measured;Step S3, select the dimension to be measured and control the rotation of corresponding rotary loading module Set load angle;Step S4, the sensor output to be measured is zeroed;Step S5, each load point is recorded in turn, and the output value of the sensor to be measured is recorded;Step S6, after repeating step S5 several times, switch to the next dimension to be measured;Step S7, after completion, decouple data, obtain calibration matrix.The present application method can be self-calibrated regularly, avoid loading force error;At the same time, the standard force value is loaded by using series weight module, to avoid a series of problems such as zero drift existing in standard sensor used by superimposed calibration machine.The present application calibration method can be adapted to different types, different dimension force sensor calibration test, high degree of automation, can achieve higher calibration accuracy.

Description

Technical Field

[0001] This invention relates to the field of sensor calibration technology, specifically to an automatic calibration method for a net weight-based multidimensional force sensor. Background Technology

[0002] A net-weight force standard machine uses the weight of a weight as the standard force value. Through an appropriate mechanical system, it automatically and smoothly applies the standard force value to the force measuring instrument (or force sensor) being tested or calibrated in a predetermined sequence. The net-weight force standard machine is the most accurate type of force standard machine, superior to superimposed, lever, and hydraulic force standard machines.

[0003] A multidimensional force sensor is a force sensor capable of simultaneously measuring force and torque components in two or more directions. The most complete form of a multidimensional force sensor is the six-dimensional force sensor, which can simultaneously measure three force components (Fx, Fy, Fz) and three torque components (Mx, My, Mz). Because six-dimensional force sensors can sense forces in all dimensions, they are widely used in the era of the booming development of humanoid robots, often in robotic arm end effectors and humanoid robot joints.

[0004] Automated calibration of multidimensional force sensors (especially six-dimensional force sensors) is quite difficult. The calibration process may require applying force in a single dimension, or simultaneously applying force in multiple dimensions, with each dimension having positive or negative values. This places high demands on the calibration equipment. Existing calibration methods have some shortcomings:

[0005] First, considering factors such as machining errors and creep of the loading rope, the control parameters for applying the loading force are not fixed. The existing method of directly using design parameters to control the loading force is prone to large calibration errors.

[0006] Secondly, existing calibration methods are basically based on superimposed force standard machines, using series-connected standard sensors to calibrate the sensor under test. However, regardless of the type of high-precision standard sensor used, there are a series of problems such as zero drift, temperature drift, and creep, making it difficult to achieve high-precision and high-reliability calibration.

[0007] Third, calibrating a multidimensional force sensor requires continuous changes in the applied force. Existing control methods have low automation and are inaccurate. Moreover, the calculation of the multidimensional force value of the sensor is relatively complex and not intuitive, making it impossible to achieve high calibration accuracy. Summary of the Invention

[0008] In view of the above problems, the purpose of this invention is to provide an automatic calibration method for a net weight-based multidimensional force sensor, which aims to solve the technical problems of existing calibration methods being unable to self-calibrate, having a low degree of automation, and having low calibration accuracy.

[0009] This invention provides the following technical solution:

[0010] The automatic calibration method for the net weight multidimensional force sensor is applied to an automatic calibration machine for the net weight multidimensional force sensor. The automatic calibration machine includes a frame, and a clamping module for clamping the multidimensional force sensor is provided on the top of the frame. Each of the four force-bearing positions of the clamping module has a loading rotating ring. A rotary loading module is provided on the outer periphery of the clamping module and on the top of the frame, which is coaxially arranged with the loading rotating ring. The frame also contains four sets of series weight modules and a linear motion module. The linear motion module acts on the series weight modules to change the loading force of the weights. The loading rotating ring has a loading rope leading out, and the loading rope passes through the rotary loading module on the same side and is connected to the corresponding series weight module.

[0011] The automatic calibration method includes the following steps:

[0012] Step S1: The automatic calibration machine performs self-calibration at regular intervals;

[0013] Step S2: Install the multi-dimensional force sensor to be tested into the clamping module;

[0014] Step S3: According to the selected dimension to be measured, control the rotation of the rotation bracket of the corresponding rotary loading module to set the loading angle. The rotary loading module that is not loaded remains in a vertical upward state, and the loading force of the loading rope is zero.

[0015] Step S4: Control the output end of the linear motion module to move to the preset point. At this time, the loading rope applies the rated loading force to the multi-dimensional force sensor under test through the loading rotating ring. After maintaining this for a period of time, the output end of the linear motion module moves to the highest point. At this time, the loading force is unloaded to zero. Repeat this loading process several times. Finally, the output of the sensor under test is cleared to zero.

[0016] Step S5: Control the output end of the linear motion module to move to the first loading point and hold it for a period of time, then continue to move to the next loading point until the last loading point. For each loading point, hold it for a period of time and record the output value of the multi-dimensional force sensor under test. Then, start from the last loading point and move upward to the previous loading point until it moves to the first loading point. Similarly, at each loading point, hold it for a period of time and record the output value of the multi-dimensional force sensor under test.

[0017] Step S6: After repeating step S5 several times, switch to the next dimension to be tested and return to step S3.

[0018] Step S7: After all dimensions are loaded, all loaded force data and sensor output values ​​are integrated and decoupled to calculate the calibration matrix of the multi-dimensional force sensor. At the same time, various parameters of the multi-dimensional force sensor under test are calculated.

[0019] Furthermore, the output end of the linear motion module has a top plate, and a support plate is mounted on the top plate via a pressure sensor. In step S1, all four loading forces of the automatic calibration machine need to be self-calibrated, and the self-calibration method is the same. The specific process of self-calibration for each channel is as follows:

[0020] S11. The current rotary loading module remains vertically upward, and the output end of the linear motion module moves downward until the tray separates from the series weight module. This is recorded as the initial position. After standing still for a period of time, the pressure sensor reading is cleared to zero.

[0021] S12. Control the output of the linear motion module to slowly move to the highest point. During the movement, continuously collect the displacement of the linear motion module relative to the initial position and the pressure sensor reading.

[0022] S13. Control the output of the linear motion module to slowly move from the highest point to the initial position. During the movement, continuously collect the displacement of the linear motion module relative to the initial position and the pressure sensor reading.

[0023] S14. Repeat steps S12 and S13 until the set number of times is reached;

[0024] S15. Calculate a table comparing the displacement of the linear motion module with the applied force value based on the measured displacement and the pressure sensor readings, for subsequent accurate control of the applied force.

[0025] Furthermore, the clamping module consists of a clamping base, a lower transition plate, an upper transition plate, and a loading frame, arranged from bottom to top. The multi-dimensional force sensor to be tested is located between the upper and lower transition plates. The four loading rotating rings are located on the four force-bearing sides of the loading frame, and the four loading rotating rings are arranged in a cross shape. After the current multi-dimensional force sensor to be tested is calibrated, the installation process for replacing the next sensor to be tested is as follows:

[0026] S21. Control the output of the linear motion module to move to the highest point;

[0027] S22. Remove the bolts between the loading frame and the upper transition plate;

[0028] S23. Control the output end of the linear motion module to move to the lowest position. At this time, the loading frame is pulled to the highest position under the force of the loading rope.

[0029] S24. Remove the upper transition plate and the current multi-dimensional force sensor to be tested in sequence, and then install the next sensor to be tested and the upper transition plate in sequence.

[0030] S25. Control the linear motion module output to move to the highest point. At this time, the loading frame descends to be close to the upper transition plate. Fix the loading frame and the upper transition plate with bolts.

[0031] Furthermore, the rotary loading module includes a mounting base, on which a rotary bracket and a rotary crankshaft are rotatably mounted, one in the front and one in the back. A rotary motor is also mounted on the mounting base. The drive shaft of the rotary motor is fixed to one end of the rotary crankshaft, and the other end of the rotary crankshaft is fixed to one end of the rotary bracket. A through hole is provided at the axis connecting the rotary crankshaft and the rotary bracket. A first reversing wheel and a second reversing wheel are rotatably mounted on the rotary bracket. A third reversing wheel is located on the mounting base below the rotary crankshaft. The loading rope passes sequentially around the first, second, and third reversing wheels and then vertically downwards to the series weight module.

[0032] Furthermore, the mounting base includes a base plate and three vertical plates located on the base plate: front, middle, and rear. The rotary support is located between the front and middle vertical plates and is shaped like a "7". The side of the front vertical plate has a clearance groove to avoid the first reversing wheel. The crankshaft is located between the middle and rear vertical plates. The rotary motor is located outside the rear vertical plate. The position of the second reversing wheel is lower than that of the first reversing wheel. A wheel seat is also fixed between the middle and rear vertical plates. The third reversing wheel is mounted on the wheel seat. The loading rope led out from the third reversing wheel passes through the wheel seat and the base plate and is connected to the series weight module.

[0033] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0034] I. In the calibration method of this invention, a pressure sensor is connected in series at the output end of the linear motion module. All four loading forces can be self-calibrated at regular intervals to avoid errors in loading forces caused by machining errors or creep of the loading rope length. After regular self-calibration, the accuracy of the loading force can be guaranteed, thereby ensuring the calibration accuracy. Moreover, the pressure sensor can indirectly monitor the loading force in real time during the calibration process, achieving an overall closed loop.

[0035] Second, in the calibration method of this invention, a series of weight modules are used to apply standard force values, which avoids a series of problems such as zero drift, temperature drift, and creep that exist in standard sensors. It can not only utilize the stable and accurate characteristics of the weight loading force, but also realize automated calibration and improve calibration efficiency.

[0036] Third, the calibration method of the present invention can control the rotation of the rotation bracket of the corresponding rotation loading module to set the loading angle according to the selected dimension to be measured. The rotation loading module that does not participate in the loading remains in a vertical upward state. It can adapt to the calibration test of different types and dimensions of force sensors, such as single-dimensional, three-dimensional, and six-dimensional sensors, and has a wide range of applications.

[0037] Fourth, this calibration method has a high degree of automation. The magnitude of the loading force applied by the series weight module can be changed directly by changing the displacement distance at the output end of the linear motion module, and the loading force reversal can be accurately realized. In addition, the four-way orthogonal layout makes the calculation of multi-dimensional force values ​​of the sensor simple and intuitive, and can achieve high calibration accuracy. Attached Figure Description

[0038] Figure 1 This is a perspective view of the automatic calibration machine of the present invention.

[0039] Figure 2 This is a schematic diagram of the dynamic calibration machine of the present invention in the state of replacing the sensor to be tested;

[0040] Figure 3 This is a schematic diagram showing the loading state of part of the weight pan in this invention;

[0041] Figure 4 This is a flowchart of the automatic calibration method for the net weight type multidimensional force sensor of the present invention;

[0042] Figure 5 This is a flowchart illustrating the self-calibration process of the automatic calibration machine of the present invention;

[0043] Figure 6 This is a flowchart illustrating the process of replacing the sensor under test in this invention.

[0044] Figure 7 This is a perspective view of the upper part of the automatic calibration machine of the present invention;

[0045] Figure 8 This is a schematic diagram of the force analysis of the sensor under test in this invention;

[0046] Figure 9 This is a structural diagram of the rotary loading module of the present invention;

[0047] Figure 10 This is a structural diagram of the series weight module of the present invention.

[0048] In the picture:

[0049] 10. Frame; 20. Lower support plate; 30. Upper support plate;

[0050] 40. Linear motion module; 41. Linear module body; 42. Top plate; 43. Pressure sensor; 44. Support plate;

[0051] 50. Series weight module; 51. Weight pan; 52. Series shaft; 53. Settling groove; 54. Stepped hole; 55. Bearing groove; 56. Mating hole; 57. Bearing pin;

[0052] 60. Rotary loading module; 61. Mounting base; 611. Base plate; 612. Vertical plate; 613. Clearance groove; 62. Rotary bracket; 63. Rotating crankshaft; 64. Rotary motor; 65. First reversing wheel; 66. Second reversing wheel; 67. Third reversing wheel; 68. Wheel seat;

[0053] 70. Clamping module; 71. Clamping base; 72. Lower transition plate; 73. Multi-dimensional force sensor to be tested; 74. Upper transition plate; 75. Loading frame; 76. Loading rotating ring;

[0054] 80. Load the rope. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] This invention provides an automatic calibration method for a net weight-based multidimensional force sensor. This method is applied to an automatic calibration machine for net weight-based multidimensional force sensors. Figure 1 The diagram shows the structure of the automatic calibration machine. The automatic calibration machine includes a frame 10 with universal support wheels at the bottom. The frame 10 is the main load-bearing body of the calibration machine; the specific structure is not limited in this embodiment. The frame 10 has a lower support plate 20 and an upper support plate 30. A clamping module 70 for mounting multi-dimensional force sensors is located on the top of the frame 10, i.e., the upper support plate 30. Each of the four force-bearing positions of the clamping module 70 has a loading rotating ring 76. Around the periphery of the clamping module 70 and located at the top of the frame, there is a rotary loading module 60 coaxially arranged corresponding to each loading rotating ring 76. The frame 10 also contains four sets of series weight modules 50 and a linear motion module 40. The linear motion module 40 acts on the series weight modules 50 to change the loading force of the weights. Loading ropes 80 extend from the loading rotating rings 76, and the loading ropes 80 pass through the rotary loading modules 60 on the same side before connecting to the corresponding series weight modules 50.

[0057] Figure 1 As shown, the multi-dimensional force sensor 73 to be tested is mounted on the clamping module 70. Specifically, the clamping module 70 consists of a clamping base 71, a lower transition plate 72, an upper transition plate 74, and a loading frame 75, arranged from bottom to top. The multi-dimensional force sensor 73 to be tested is located between the upper and lower transition plates. Four loading rotating rings 76 are located on the four force-bearing sides of the loading frame 75, and the four loading rotating rings 76 are arranged in a cross shape. Of course, the loading frame can also be of other shapes, as long as the loading rotating rings 76 are arranged in an orthogonal cross shape. In this device, the loading rotating rings 76 are mounted on the loading frame 75 of the clamping module 70 through bearings and can rotate freely around their own axis. The loading rope 80 is connected (e.g., by snap-fit, threaded terminal connection, etc.) to the loading rotating ring 76.

[0058] In this device, the function of the rotary loading module 60 is to change the winding direction of the loading rope 80 so that the series weight module can smoothly apply the loading force, and at the same time change the loading force angle of the loading rope 80 on the loading rotating ring 76, and the part of the loading rope 80 leading out from the loading rotating ring 76 always remains perpendicular to the axis of the loading rotating ring 76.

[0059] The series weight module 50 consists of a weight pan 51 and a weight series shaft 52 connected in series. The bottom of the series weight module 50 rests on the output end of the linear motion module 40. When the output end moves upward and lifts the series weight module 50, the higher it is lifted, the more weight the weight pan 51 carries on the linear motion module 40, and the smaller the tension of the series weight module 50 on the loading rope 80. Conversely, when the output end descends, the weight of the weight pan 51 acting on the loading rope 80 gradually increases. Therefore, the force acting on the loading rope can be automatically controlled by the action of the output end of the linear motion module 40. That is, the linear motion module 40 can control the loading force in the loading rope 80, from zero to the full weight of the weights. Therefore, by driving the series weight module 50 to move in different positions by the linear motion module 40, the weight of the weight pan acting on the loading rope can be changed.

[0060] As shown in Figures 2 and 3, a specific structure of the linear motion module 40 includes a linear module body 41 with a top plate 42 at its output end. The linear module body 41 can drive the top plate 42 to perform vertical linear motion. A support plate 44 is mounted on the top plate 42 via a pressure sensor 43. The pressure sensor 43 can measure the weight of the series weight module 50 carried by the linear motion module 40.

[0061] Based on the aforementioned automatic calibration machine for net weight-based multidimensional force sensors, this embodiment provides an automatic calibration method for net weight-based multidimensional force sensors, such as... Figure 4 As shown, it includes the following steps:

[0062] Step S1: The automatic calibration machine performs self-calibration at regular intervals.

[0063] Considering factors such as machining errors and the creep of the loading rope, existing calibration methods directly control the loading force through fixed design parameters. However, in reality, due to machining errors and loading rope creep, after prolonged use, fixed design parameters may lead to inaccurate loading force control, resulting in errors or even erroneous results. Therefore, this step does not directly use fixed design parameters. To accurately obtain this correspondence, this step designs a self-calibration scheme that performs self-calibration periodically to ensure the equipment can accurately apply the loading force. The automatic calibration machine has four loading force channels, each capable of self-calibration using the same method, such as... Figure 5 As shown, the specific process is as follows:

[0064] S11. The current rotary loading module remains vertically upward, and the output end of the linear motion module moves downward until the tray separates from the series weight module. This is recorded as the initial position. After standing still for a period of time, the pressure sensor reading is cleared to zero.

[0065] Before self-calibration, a sensor simulation block is installed in the sensor clamping module. This sensor simulation block can withstand extremely high loads, and the output end of the linear motion module is at its highest point. During self-calibration, the rotary loading module remains vertically upward, meaning the portion of the loading rope extending from the loading rotating ring remains vertical. Then, the support plate at the output end of the linear motion module descends until it separates from the series weight module; this position is recorded as the initial position. After waiting 30 seconds, the pressure sensor reading is zeroed.

[0066] S12. Control the output of the linear motion module to slowly move to the highest point. During the movement, continuously collect the displacement of the linear motion module relative to the initial position and the pressure sensor reading.

[0067] During movement, the linear motion module outputs the displacement value, and the pressure sensor also outputs a corresponding value. The linear motion module output gradually moves upwards from a low position, acquiring a series of displacement values ​​and pressure sensor readings at different points during the movement.

[0068] S13. Control the output of the linear motion module to slowly move from the highest point to the initial position. During the movement, continuously collect the displacement of the linear motion module relative to the initial position and the pressure sensor reading.

[0069] Then, by slowly moving from the highest point back to the initial position, a series of displacements and pressure sensor readings can be obtained at different points.

[0070] S14. Repeat steps S12 and S13 until the set number of times is reached.

[0071] To ensure accuracy, steps S12 and S13 can be repeated three times.

[0072] S15. Calculate a table comparing the displacement of the linear motion module with the applied force value based on the measured displacement and the pressure sensor readings, for subsequent accurate control of the applied force.

[0073] Finally, based on the aforementioned series of displacement values ​​and pressure sensor readings, a table comparing the displacement of the linear motion module with the applied force can be calculated.

[0074] For example, a specific comparison table is shown below:

[0075] Displacement / mm 9.41 14.46 19.52 24.58 29.64 34.70 39.76 44.82 49.88 54.94 60.02 Loading force / N 980 882 784 686 588 490 392 294 196 98 0

[0076] Furthermore, it should be noted that the accuracy of the applied force here does not depend on the measurement accuracy of the pressure sensor 43. The pressure sensor 43 plays an auxiliary role in the calibration process, used to accurately determine the reasonable displacement value of the linear motion module 40. The accuracy of the applied force of the automatic calibration machine is determined by the accuracy of the weight's gravity. Specifically, the applied force value is obtained by referring to the table obtained through self-calibration and then based on the displacement of the controlled linear motion module.

[0077] Step S2: Install the multi-dimensional force sensor to be tested into the clamping module.

[0078] After self-calibration, subsequent sensor calibration can be performed. Before calibration, the multi-dimensional force sensor to be tested needs to be installed in the clamping module. If there is already a calibrated sensor in the current clamping module, when replacing the next sensor, such as... Figure 6 As shown, the installation process is as follows:

[0079] S21. Control the output terminal of linear motion module 40 to move to the highest point;

[0080] S22. Remove the bolts between the loading frame 75 and the upper transition plate 74;

[0081] S23. Control the linear motion module 40 to move to the lowest position. At this time, the loading frame 75 is pulled to the highest position under the force of the loading rope 80.

[0082] S24. Remove the upper transition plate 74 and the current multi-dimensional force sensor 73 in sequence, and then install the next sensor to be tested and the upper transition plate 74 in sequence.

[0083] S25. Control the linear motion module 40 output terminal to move to the highest point. At this time, the loading frame 75 descends to be close to the upper transition plate 74, and the loading frame 75 and the upper transition plate 74 are fixed by bolts.

[0084] If there is no sensor under test in the current clamping module, the sensor under test is directly installed on the lower transition plate 73, and then the loading frame 75 and the upper transition plate 74 are fixed in accordance with the installation step S25.

[0085] Step S3: According to the selected dimension to be measured, control the rotation of the rotation bracket of the corresponding rotary loading module to set the loading angle. The rotary loading module that is not loaded remains in a vertical upward state, and the loading force of the loading rope is zero.

[0086] This automatic calibration machine is suitable for calibrating various types of sensors and has four force output channels. When all channels are used, it can be used for six-dimensional force sensor calibration. If one or more dimensions are selectively used, this automatic calibration machine can be used for calibrating single-dimensional force sensors, torque sensors, three-dimensional force sensors, and other force sensors. Therefore, for the type of sensor to be calibrated, select the corresponding test dimension, and then control the rotation bracket of the corresponding rotary loading module to rotate by a certain loading angle. The rotary loading module that is not involved in loading remains vertically upward, the output end of the linear motion module is at its highest position, and the tension in the loading rope is zero.

[0087] Step S4: Control the output end of the linear motion module to move to the preset point. At this time, the loading rope applies the rated loading force to the multi-dimensional force sensor under test through the loading rotating ring. After maintaining this for a period of time, the output end of the linear motion module moves to the highest point. At this time, the loading force is unloaded to zero. Repeat this loading process several times, and finally the output of the sensor under test is cleared to zero.

[0088] The preset point is a fixed point. The loading rope applies a rated load force in a certain direction to the sensor, holds it for 30 seconds, then the output end of the linear motion module moves upward until the load force is unloaded to zero. After another 30 seconds, the rated load force is applied again, and this process is repeated three times. After the load force is unloaded to zero on the last attempt, wait one minute, then zero the sensor and adjust its zero point. The purpose of this step is to make the sensor test more stable by applying and unloading the rated load force multiple times in advance.

[0089] Step S5: Control the output end of the linear motion module to move to the first loading point and hold it for a period of time, then continue to move to the next loading point until the last loading point. For each loading point, hold it for a period of time and record the output value of the multi-dimensional force sensor under test. Then, start from the last loading point and move upward to the previous loading point until it moves to the first loading point. Similarly, at each loading point, hold it for a period of time and record the output value of the multi-dimensional force sensor under test.

[0090] This step involves a specific loading process in one dimension. Since different magnitudes of loading force need to be applied to the sensor under test, different displacements at the output of the linear motion module need to be controlled. Because a table of displacement and loading force values ​​was provided earlier, different loading force values ​​can be set according to the actual calibration requirements. Then, the corresponding displacement value is found by looking up the table. Each displacement value corresponds to a loading point, resulting in a series of loading points. For ease of description, these can be referred to as the first loading point to the last loading point.

[0091] The linear motion module output starts from the first loading point, holds for 30 seconds, and then continues to move to the next loading point until the last loading point. Each loading point is held for 30 seconds before the sensor output value is recorded. Then, it moves in reverse from the last loading point back to the first loading point, again holding each loading point for 30 seconds before recording the sensor output value. This completes one loading cycle.

[0092] Step S6: After repeating step S5 several times, switch to the next dimension to be tested and return to step S3.

[0093] In step S3, a dimension to be tested is selected, and loading is controlled and repeated several times, such as 3 times. After the dimension is loaded, the process switches to loading the next dimension and returns to step S3. Once all dimensions are loaded, the process proceeds to the next step.

[0094] Step S7: After all dimensions are loaded, all loaded force data and sensor output values ​​are integrated and decoupled to calculate the calibration matrix of the multi-dimensional force sensor. At the same time, various parameters of the multi-dimensional force sensor under test are calculated.

[0095] The specific decoupling algorithm and calibration matrix calculation process are not the focus of this embodiment and will not be elaborated here. Simultaneously, the repeatability, linearity, hysteresis characteristics, crosstalk, and other parameters of the sensor under test are calculated according to test standards (such as the formulas in the national standard GB / T33010).

[0096] As can be seen from step S5 above, at each loading point, the loading rope maintains tension on the loading rotating ring. Simultaneously, the rotating support of the rotary loading module rotates, causing the loading rotating ring to rotate, thereby changing the loading force angle of the loading rope. Therefore, at each loading point, the loading rope applies a loading force of corresponding angle and magnitude to the sensor under test. Thus, the loading force magnitude and angle of the loading rope can be set according to actual requirements to achieve testing of multi-dimensional force sensors. If the loading force of one of the loading ropes is 0, testing is not performed in that direction, adapting to the testing needs of different dimensional force sensors.

[0097] At each loading point, such as Figure 7 , 8 As shown, let the tensions of the loading ropes at the loading points be F1, F2, F3, and F4, and the angles with the horizontal direction be θ1, θ2, θ3, and θ4, respectively. L is the length of the lever arm of the loading force. These tensions and angles are data obtained during loading in each dimension and are known data. The six-dimensional force can be calculated at each loading point using a set of tension and angle data. The formula for calculating the six-dimensional force on the sensor under test is as follows:

[0098] ;

[0099] ;

[0100] ;

[0101] ;

[0102] ;

[0103] .

[0104] Therefore, the six-dimensional force can be calculated using the above formula, with numerical output at each loading point. All data are fitted and decoupled to obtain the final calibration matrix. The calibration matrix can then be used to calibrate the output of the sensor under test.

[0105] It should be noted that the focus of this embodiment is not on decoupling or calibration matrix calculation, but rather on the ability to more intuitively calculate six-dimensional forces through structural design. From the above calculation formula, it can be seen that the multi-dimensional force value calculation of this device's sensor is simple and intuitive. This calibration machine can achieve simultaneous loading in all six dimensions, and can also achieve individual loading of forces in each dimension. For example:

[0106] when At that time, only The force values ​​in all other dimensions are 0.

[0107] when At that time, only The force values ​​in all other dimensions are 0.

[0108] In addition, this embodiment also provides a specific structure of the rotary loading module 60, such as... Figure 9 As shown, the rotary loading module 60 includes a mounting base 61. A rotary bracket 62 and a rotary crankshaft 63 are rotatably mounted on the mounting base 61, one in the front and one in the back. A rotary motor 64 is also mounted on the mounting base 61. The drive shaft of the rotary motor 64 is fixed to one end of the rotary crankshaft 63, and the other end of the rotary crankshaft 63 is fixed to one end of the rotary bracket 62. A through hole is located at the axis connecting the rotary crankshaft 63 and the rotary bracket 62. A first reversing wheel 65 and a second reversing wheel 66 are rotatably mounted on the rotary bracket 62. A third reversing wheel 67 is located on the mounting base 61 below the rotary crankshaft 63. The loading rope 80 passes sequentially around the first, second, and third reversing wheels and then vertically downwards to the series weight module. As one installation method, the bottom ends of the rotary bracket 62 are mounted on the mounting base 61 via bearings and can rotate around the bearing axis. The first and second reversing wheels are also mounted on the rotary bracket 62 via bearings. One end of the rotating crankshaft 63 is fixedly connected to the rotating shaft of the rotating bracket 62 by bolts, and the other end is fixedly connected to the output shaft of the rotating motor 64 by bolts.

[0109] In the figure, the mounting base 61 includes a base plate 611 and three vertical plates 612 located on the base plate 611: front, middle and rear. The rotary support 62 is located between the front and middle vertical plates and is shaped like the number 7. The side of the front vertical plate has a clearance groove 613 to avoid the first reversing wheel 65. The rotating crankshaft 63 is located between the middle and rear vertical plates. The rotary motor 64 is located outside the rear vertical plate. The position of the second reversing wheel 66 is lower than that of the first reversing wheel 65. A wheel seat 68 is also fixed between the middle and rear vertical plates. The third reversing wheel 67 is mounted on the wheel seat 68. The loading rope 80 led out from the third reversing wheel 67 passes through the wheel seat 68 and the base plate 611 and is connected to the series weight module.

[0110] The structural feature of this rotary loading module 60 is that the rotary bracket 62 is subjected to force at both ends. Since the loading rope 80 exerts a loading force on the first reversing wheel 65 and the rotary bracket 62, compared to a cantilever structure with force at one end, the double-end force ensures the rotational stability of the rotary bracket 62, reduces bearing wear, and provides better performance. Furthermore, because the first reversing wheel 65 on the rotary bracket extends beyond the mounting base 61, the loading rope 80 can act linearly on the loading rotating ring, causing interference between the first reversing wheel 65 and the front vertical plate. In this embodiment, a clearance groove 613 is provided on the side of the front vertical plate to avoid the first reversing wheel 65. Since the rotation angle of the rotary bracket 62 is limited by the front vertical plate, it cannot rotate completely 360 degrees. The third reversing wheel 67 also interferes with the rotating crankshaft 63, so the rotating crankshaft 63 cannot rotate 360 ​​degrees either. Adjusting the relative installation angle between the rotating crankshaft 63 and the rotary bracket 62 is sufficient; they do not need to be on the same plane. In this embodiment, the rotation range of the rotating bracket 62 exceeds 270°, for example, it can stop at positions such as 0°, 90°, 180°, and 270° in the orthogonal coordinate system to ensure that all unidimensional forces can be applied.

[0111] For the series weight module 50, this embodiment does not limit the specific structure, but mainly includes a multi-layer weight pan 51 and a weight series shaft 52. When the output end of the linear motion module 40 moves to the highest position, all weight pans are stacked together, and adjacent layers are in contact, so the loading rope is not under force. When the output end of the linear motion module 40 descends, it gradually detaches from the next layer of weight pan, starting from the upper layer. However, through the action of the weight series shaft, the series connection is still maintained. The weight of the weight pan that is pulled up and detached is loaded onto the loading rope, such as... Figure 3 As shown, there are 9 weight pans loaded on the loading rope.

[0112] like Figure 10The illustrated structure shows a series weight module 50 comprising multiple weight pans 51 connected vertically and a weight connecting shaft 52 serving as a connecting element. The connecting shaft 52 has a groove 53 at its bottom center, and a stepped hole 54 at the center of the weight pan body. The lower part of the connecting shaft 52 is located within the stepped hole 54. In the illustration, the connecting shaft 52 has upper and lower parts; when connected in series, the upper part of the lower connecting shaft is located within the groove 53 of the upper connecting shaft. Both sides of the connecting shaft 52 have several vertically oriented oval-shaped bearing grooves 55. The weight pan body has several mating holes 56 at the same position on its side wall, extending to the stepped hole. A mating bearing pin 57 is inserted into each of the mating holes 56. The inner end of the bearing pin 57 is located within the bearing groove of the upper part of the lower connecting shaft. When the weight of the lower weight pan acts on the bearing pin 57 of the upper weight pan, a vertical gap remains between the lower connecting shaft and the groove of the upper connecting shaft. In this embodiment, the series shaft is interference-fitted with the lower part of the stepped hole, and the upper part of the series shaft is slightly smaller than the size of the countersink to ensure that the upper and lower weight pans do not interfere with each other when connected in series. In this structure, the bearing pin and the mating hole of the weight pan have a mechanical transition fit, and cylindrical adhesive can be used to secure the connection. The bearing pin also has a threaded hole for removing the bearing pin when the weight pan needs to be disassembled.

[0113] In summary, the calibration method of this invention, by connecting a pressure sensor in series with the linear motion module, enables timed self-calibration, avoiding errors in the applied force caused by machining errors or creep of the loading rope length. Timed self-calibration ensures the accuracy of the applied force, thereby guaranteeing calibration accuracy. Furthermore, the pressure sensor can indirectly monitor the applied force during the calibration process in real time. Simultaneously, the calibration method uses a series weight module for standard force loading, avoiding issues such as zero drift, temperature drift, and creep present in standard sensors. Moreover, the rotation of the corresponding rotary loading module's support can be controlled to set the loading angle according to the selected dimension to be measured, while the rotary loading module not involved in loading remains vertically upward, adapting to the calibration tests of different types and dimensions of force sensors. Finally, this calibration method has a high degree of automation; the magnitude of the applied force by the series weight module can be changed directly by altering the displacement distance at the output end of the linear motion module, and the direction of the applied force can be accurately reversed. The four-way orthogonal layout makes the calculation of multi-dimensional force values ​​of the sensor simple and intuitive, achieving high calibration accuracy.

[0114] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0115] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An automatic calibration method for a net weight-based multidimensional force sensor, the method being applied to an automatic calibration machine for a net weight-based multidimensional force sensor, characterized in that: The automatic calibration machine includes a frame, and a clamping module for clamping multi-dimensional force sensors is provided on the top of the frame. Each of the four force-bearing positions of the clamping module has a loading rotating ring. On the outer periphery of the clamping module and located on the top of the frame, there is a rotary loading module that is coaxially arranged with the loading rotating rings one by one. The frame also contains four sets of series weight modules and a linear motion module. The linear motion module acts on the series weight modules to change the loading force of the weights. The loading rotating ring has a loading rope leading out, and the loading rope passes through the rotary loading module on the same side and is connected to the corresponding series weight module. The automatic calibration method includes the following steps: Step S1: The automatic calibration machine performs self-calibration at regular intervals; Step S2: Install the multi-dimensional force sensor to be tested into the clamping module; Step S3: According to the selected dimension to be measured, control the rotation of the rotation bracket of the corresponding rotary loading module to set the loading angle. The rotary loading module that is not loaded remains in a vertical upward state, and the loading force of the loading rope is zero. Step S4: Control the output end of the linear motion module to move to the preset point. At this time, the loading rope applies the rated loading force to the multi-dimensional force sensor under test through the loading rotating ring. After maintaining this for a period of time, the output end of the linear motion module moves to the highest point. At this time, the loading force is unloaded to zero. Repeat this loading process several times. Finally, the output of the sensor under test is cleared to zero. Step S5: Control the output end of the linear motion module to move to the first loading point and hold it for a period of time, then continue to move to the next loading point until the last loading point. For each loading point, hold it for a period of time and record the output value of the multi-dimensional force sensor under test. Then, start from the last loading point and move upward to the previous loading point until it moves to the first loading point. Similarly, at each loading point, hold it for a period of time and record the output value of the multi-dimensional force sensor under test. Step S6: After repeating step S5 several times, switch to the next dimension to be tested and return to step S3. Step S7: After all dimensions are loaded, all loaded force data and sensor output values ​​are integrated and decoupled to calculate the calibration matrix of the multi-dimensional force sensor. At the same time, various parameters of the multi-dimensional force sensor under test are calculated.

2. The automatic calibration method for a net weight-based multidimensional force sensor as described in claim 1, characterized in that, The output end of the linear motion module has a top plate, and a support plate is installed on the top plate via a pressure sensor. In step S1, all four loading forces of the automatic calibration machine need to be self-calibrated. The self-calibration method is the same, and the specific process of self-calibration for each channel is as follows: S11. The current rotary loading module remains vertically upward, and the output end of the linear motion module moves downward until the tray separates from the series weight module. This is recorded as the initial position. After standing still for a period of time, the pressure sensor reading is cleared to zero. S12. Control the output of the linear motion module to slowly move to the highest point. During the movement, continuously collect the displacement of the linear motion module relative to the initial position and the pressure sensor reading. S13. Control the output of the linear motion module to slowly move from the highest point to the initial position. During the movement, continuously collect the displacement of the linear motion module relative to the initial position and the pressure sensor reading. S14. Repeat steps S12 and S13 until the set number of times is reached; S15. Calculate a table comparing the displacement of the linear motion module with the applied force value based on the measured displacement and the pressure sensor readings, for subsequent accurate control of the applied force.

3. The automatic calibration method for a net weight-based multidimensional force sensor as described in claim 2, characterized in that, The clamping module consists of, from bottom to top, a clamping base, a lower transition plate, an upper transition plate, and a loading frame. The multi-dimensional force sensor to be tested is located between the upper and lower transition plates. The four loading rotating rings are located on the four force-bearing sides of the loading frame, and the four loading rotating rings are arranged in a cross shape. After the current multi-dimensional force sensor to be tested is calibrated, the installation process for replacing the next sensor to be tested is as follows: S21. Control the output of the linear motion module to move to the highest point; S22. Remove the bolts between the loading frame and the upper transition plate; S23. Control the output end of the linear motion module to move to the lowest position. At this time, the loading frame is pulled to the highest position under the force of the loading rope. S24. Remove the upper transition plate and the current multi-dimensional force sensor to be tested in sequence, and then install the next sensor to be tested and the upper transition plate in sequence. S25. Control the linear motion module output to move to the highest point. At this time, the loading frame descends to be close to the upper transition plate. Fix the loading frame and the upper transition plate with bolts.

4. The automatic calibration method for a net weight-based multidimensional force sensor as described in claim 2, characterized in that, The rotary loading module includes a mounting base, on which a rotary bracket and a rotary crankshaft are rotatably mounted. A rotary motor is also mounted on the mounting base. The drive shaft of the rotary motor is fixed to one end of the rotary crankshaft, and the other end of the rotary crankshaft is fixed to one end of the rotary bracket. A through hole is provided at the axis connecting the rotary crankshaft and the rotary bracket. A first reversing wheel and a second reversing wheel are rotatably mounted on the rotary bracket. A third reversing wheel is located on the mounting base below the rotary crankshaft. The loading rope passes sequentially around the first, second, and third reversing wheels and is then vertically connected downwards to the series weight module.

5. The automatic calibration method for a net weight-type multidimensional force sensor as described in claim 4, characterized in that, The mounting base includes a base plate and three vertical plates (front, middle, and rear) located on the base plate. The rotary support is located between the front and middle vertical plates and is shaped like a "7". The side of the front vertical plate has a clearance groove to avoid the first reversing wheel. The crankshaft is located between the middle and rear vertical plates. The rotary motor is located on the outside of the rear vertical plate. The position of the second reversing wheel is lower than that of the first reversing wheel. A wheel seat is also fixed between the middle and rear vertical plates. The third reversing wheel is mounted on the wheel seat. The loading rope led out from the third reversing wheel passes through the wheel seat and the base plate and is connected to the series weight module.

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