CN115839796B - Calibration equipment, calibration test system and calibration method of three-dimensional force sensor - Google Patents

Abstract

The invention discloses a calibration equipment for a three-dimensional force sensor, which includes a test platform and a force application structure arranged on a test platform; a three-dimensional force sensor to be calibrated is installed on the test platform, and a three-dimensional force sensor to be calibrated is installed on the test platform. Test terminal; the test platform includes a single rocker arm structure, a turntable installed on the single rocker arm structure, and a fixed base. The turntable is rotationally installed on the single rocker arm structure. The single rocker arm structure changes through rotation. The turntable changes the tangential angle through rotation; the force-applying structure includes a transverse sliding mechanism, a longitudinal sliding mechanism, a single-dimensional force sensor, a push rod body and a push rod head. The calibration equipment has a simpler structure and uses linear fitting to obtain the curve of the calibration data to achieve automatic calibration, data writing and factory testing of the three-dimensional force sensor.

Description

Calibration equipment, calibration test system and calibration method of three-dimensional force sensor

Technical field

The present invention relates to the technical field of three-dimensional force sensor calibration, and specifically relates to a calibration equipment, a calibration test system and a calibration method of a three-dimensional force sensor.

Background technique

The three-dimensional force sensor is designed to detect torque or torque in three directions in three-dimensional space. It can accurately measure information on three axes, convert the component forces of the three axes into voltage signals, and output them through the RS485 bus after collection. Therefore, it is widely used in Robot joint correction, motor vibration detection and non-standard automation and other fields. On the one hand, due to factors such as numerical errors in circuit components, uneven measurement structures, and inconsistent screw pre-tightening forces during the overall installation of the sensor during the production process of the three-dimensional force sensor, there is a certain zero point error in the sensor; on the other hand, the three-dimensional force sensor has a certain zero point error. The tangential force transfer coefficient and normal force transfer coefficient of the sensor need to be accurately calibrated, so an appropriate calibration method needs to be developed based on its measurement principle. In addition, the errors and uncertainties caused by manual calibration will amplify the sensor errors. Therefore, it is necessary to design a set of automatic calibration equipment to simplify manual operations and reduce human errors during the calibration process.

Application No. 2021113331676 discloses a load-adjustable three-dimensional force sensor calibration device. The calibration equipment uses a combination of two rotating worktables with rotation axes perpendicular to each other, and records the force through a thrust meter. The structure is relatively complex, the force recorded by the thrust meter has a large error, the calibrated angle range is small, and the calibration efficiency is low. Moreover, the calibration equipment can only realize the function of calibration loading and cannot complete the factory testing and re-calibration of the sensor.

Contents of the invention

The object of the present invention is to provide a calibration equipment, a calibration test system and a calibration method for a three-dimensional force sensor. The calibration equipment has a simpler structure and can calibrate a wide range of angles. It uses linear fitting to obtain the curve of the calibration data to realize the calibration of the three-dimensional force sensor. Automatic calibration, data writing and factory testing.

The technical solution to achieve the purpose of the present invention is:

A calibration equipment for a three-dimensional force sensor, including a test platform and a force application structure arranged on a test platform; a three-dimensional force sensor to be calibrated is installed on the test platform, and a test terminal is installed on the three-dimensional force sensor to be calibrated;

The test platform includes a single rocker arm structure, a turntable mounted on the single rocker arm structure, and a fixed base. The single rocker arm structure is rotatably mounted on the upper end of the first bracket, and the turntable is rotatably mounted on the single rocker arm structure. Arm structure, the single rocker arm structure changes the normal angle through rotation, the turntable changes the tangential angle through rotation, and the fixed base is fixed on the turntable and rotates with the turntable;

The force-applying structure includes a transverse sliding mechanism, a longitudinal sliding mechanism, a single-dimensional force sensor, a push rod body and a push rod head. One end of the single-dimensional force sensor is fixed on the push rod head, and the other end is fixed on the push rod body. , the push rod body is installed on a transverse sliding mechanism, which is used to move the push rod head horizontally to apply force to the test terminal. The force is measured by the single-dimensional force sensor and fed back to Host computer.

In a preferred technical solution, the test terminal includes a spherical structure for loading force and a connecting post connecting the spherical structure. The connecting post is provided with a screw hole, and the sensor to be calibrated is pre-tightened by a screw.

In a preferred technical solution, the putter head is a cylinder and the front end is a concave spherical structure.

In a preferred technical solution, the concave spherical structure completely surrounds the spherical structure of the test terminal.

In the preferred technical solution, the sensor to be calibrated is installed on the fixed base of the test platform, and its interior is composed of three 120° distributed strain gauge circuits and a measurement circuit. The measurement circuit communicates with the host computer.

The invention also discloses a calibration and testing system for a three-dimensional force sensor, which includes the above-mentioned calibration equipment of the three-dimensional force sensor and a host computer. The host computer is provided with a calibration process, and controls the calibration device to perform automatic operation according to the built-in calibration process. Calibration, data writing and factory testing, while using linear fitting to get the curve of the calibration data.

The invention also discloses a calibration method of a three-dimensional force sensor, which adopts the above-mentioned three-dimensional force sensor testing system. The calibration method includes the following steps:

S01: By moving the push rod body, the push rod head exerts horizontal force on the test terminal on the normal plane, and at the same time, the turntable is controlled to rotate so that the force exerting direction of the push rod head faces the test terminal. Strain gauge circuit to be tested;

S02: Apply a set of forces F _j of different sizes on the force-bearing terminals, and calculate the output voltage change value ΔV _1j of the strain gauge circuit;

S03: Calculate the tangential coefficient d _vi through linear fitting and complete the calibration of the tangential coefficient;

S04: Make the test platform and the plane of the calibration equipment form an angle of 90°, apply a set of vertically downward forces F _j of different sizes on the force-bearing terminals, and similarly measure the strain gauge circuit voltages at the three different angles. Change values ΔV _1j , ΔV _2j , ΔV _3j ;

S05: Finally, calculate the tangential coefficient d _vi through linear fitting.

In a preferred technical solution, the method of applying force in steps S02 and S04 includes: advancing the push rod head at a constant speed when it contacts the test terminal, that is, applying a force with a constant rate of change to the test terminal. The main body of the push rod stops when the force reaches the upper limit; during this process, the host computer continuously collects data from the three strain gauge circuits of the single-dimensional force sensor and the three-dimensional force sensor to be calibrated.

The invention also discloses a computer storage medium on which a computer program is stored. When the computer program is executed, the above-mentioned calibration method of the three-dimensional force sensor is implemented.

Compared with the prior art, the significant advantages of the present invention are:

(1) The structure of the calibration equipment of the present invention is simpler, the range of calibration angles is large, and the calibration process is closer to the actual application environment. At the same time, linear fitting is used to obtain the curve of the calibration data, which reduces possible errors and can control three-dimensional forces in It is displayed in the host computer, and through the control of the host computer, the automatic calibration, data writing and factory testing of the three-dimensional force sensor are realized.

(2) Based on the force measurement structure of the three-dimensional force sensor and its force measurement principle, the present invention designs a simple and accurate calibration method. This calibration method simplifies the entire calibration process, realizes the automation of calibration, and improves the efficiency of calibration. efficiency.

Description of the drawings

Figure 1 is a front view of the three-dimensional force sensor calibration equipment of this embodiment;

Figure 2 is a schematic structural diagram of the test platform of the three-dimensional force sensor calibration equipment in this embodiment;

Figure 3 is a schematic diagram of the force application structure of the three-dimensional force sensor calibration equipment of this embodiment;

Figure 4 is a schematic diagram of the tangential coefficient calibration of the three-dimensional force sensor in this embodiment;

Figure 5 is a schematic diagram of the calibration of the normal coefficient of the three-dimensional force sensor in this embodiment;

Figure 6 is a straight line graph fitting the tangential and normal data in this embodiment.

In the figure: three-dimensional force sensor 1; test platform 2; force application structure 3; test platform 4; first bracket 20; second bracket 30; single rocker arm structure 201; test terminal 202; spherical structure 2021; connecting column 2022; M4 connection hole 203; M5 connection hole 204; servo motor 205; turntable structure 206; fixed base 207; industrial control screen 301; fixing bolt 302; push rod head 303; single-dimensional force sensor 304; servo motor 305; push rod body 306; Longitudinal screw slide rail 307; transverse screw slide rail 308.

Detailed ways

The principle of the present invention is: the structure of the calibration equipment of the present invention is simpler, and the calibration process is closer to the actual application environment. At the same time, linear fitting is used to obtain the curve of the calibration data, which reduces possible errors and can control three-dimensional forces in the host computer. It is displayed, and through the control of the host computer, automatic calibration, data writing and factory testing of the three-dimensional force sensor are realized.

Example 1:

As shown in Figure 1-3, a calibration equipment for a three-dimensional force sensor includes a test platform 2 and a force application structure 3 installed on a test platform 4; a three-dimensional force sensor 1 to be calibrated is installed on the test platform 2. A test terminal 202 is installed on the force sensor 1;

The test platform 2 includes a single rocker arm structure 201, a turntable 206 installed on the single rocker arm structure 201, and a fixed base 207. The single rocker arm structure 201 is rotatably installed on the upper end of the first bracket 20, and the turntable 206 is rotatably installed on the single rocker arm structure. 201. The single rocker arm structure 201 changes the normal angle through rotation, the turntable 206 changes the tangential angle through rotation, and the fixed base 207 is fixed on the turntable 206 and rotates with the turntable 206;

The force-applying structure 3 includes a transverse sliding mechanism, a longitudinal sliding mechanism, a single-dimensional force sensor 304, a push rod body 306 and a push rod head 303. The transverse sliding mechanism and the longitudinal sliding mechanism are installed on the second bracket 30, and the single-dimensional force sensor 304 is fixed at one end. On the push rod head 303, the other end is fixed on the push rod body 306. The push rod main body 306 is installed on a transverse sliding mechanism. The transverse sliding mechanism is used to move the push rod head 303 horizontally to apply force to the test terminal 202. Through a single-dimensional The force sensor 304 measures the force and feeds it back to the host computer 301 .

Specifically, the three-dimensional force sensor 1 is installed on the turntable 206 of the test platform 2 through M5 hexagon socket screws and M5 connection holes 204 . The test terminal 202 passes through the M3 connection hole 203 through M4 screws and is fixed on the three-dimensional force sensor 1.

The single rocker arm structure 201 and the turntable 206 are provided with rotational power by the servo motor 205.

In one embodiment, as shown in Figure 2, the test terminal 202 includes a spherical structure 2021 for loading force and a connecting column 2022 connecting the spherical structure 2021. The connecting column 2022 has a screw hole, and the sensor to be calibrated is pre-tightened by the screw. 1. The spherical surface of the spherical structure 2021 can ensure that the load always acts equivalently on the same spherical center.

In one embodiment, the putter head 303 is a cylinder, and the front end is a concave spherical structure. It can improve the stability of force application.

In one embodiment, the concave spherical structure completely wraps the spherical structure 2021 of the test terminal 202 . Further improve the stability of force application.

In one embodiment, the sensor 1 to be calibrated is installed on the fixed base 207 of the test platform 2. The sensor 1 is internally composed of three 120° distributed strain gauge circuits and a measurement circuit. The measurement circuit communicates with the host computer. Specifically, the RS-485 interface is used to communicate with the host computer.

Specifically, as shown in FIG. 3 , the front end of the single-dimensional force sensor 304 uses bolts 302 to fix the push rod head 303 , and the rear end also uses bolts 302 to fix the push rod body 306 . The push rod body 306 is installed on the longitudinal screw slide rail 307, and the longitudinal screw slide rail 307 is installed on the transverse screw slide rail 308. The longitudinal screw slide rail 307 and the transverse screw slide rail 308 are powered by a servo motor 305.

Specifically, the force measurement principle formula of the three-dimensional force sensor to be calibrated is as follows:

In the formula, F is the force magnitude of the three-dimensional force sensor, θ is the tangential angle of the force, is the normal angle of the force, V _Pi (i=1,2,3) is the voltage value measured by the three strain gauge circuits in the three-dimensional force sensor, d _vi (i=1,2,3) is the voltage value of the three-dimensional force sensor. The proportional coefficient between the tangential component of the force and the voltage measured by the three strain gauge circuits is referred to as the tangential coefficient. d _hi (i=1,2,3) is the normal component of the three-dimensional force sensor and the three strain gauges. The proportional coefficient of the circuit output voltage, referred to as the normal coefficient, ch _i (i=1,2,3) is the voltage output of the three strain gauge circuits in the initial state, referred to as the zero point.

In another embodiment, a three-dimensional force sensor calibration test system includes the above-mentioned three-dimensional force sensor calibration equipment and a host computer. A calibration process is provided in the host computer, and the calibration device is controlled to perform automatic calibration according to the built-in calibration process. , data writing and factory testing, while using linear fitting to get the curve of the calibration data.

In another embodiment, a calibration method of a three-dimensional force sensor adopts the above-mentioned three-dimensional force sensor testing system. The calibration method includes the following steps:

S01: By moving the push rod body, the push rod head exerts horizontal force on the test terminal on the normal plane, and at the same time, the turntable is controlled to rotate so that the force exerting direction of the push rod head faces the test terminal. Strain gauge circuit to be tested;

S02: Apply a set of forces F _j of different sizes on the force-bearing terminals, and calculate the output voltage change value ΔV _1j of the strain gauge circuit;

S03: Calculate the tangential coefficient d _vi through linear fitting and complete the calibration of the tangential coefficient;

S04: Make the test platform and the plane of the calibration equipment form an angle of 90°, apply a set of vertically downward forces F _j of different sizes on the force-bearing terminals, and similarly measure the strain gauge circuit voltages at the three different angles. Change values ΔV _1j , ΔV _2j , ΔV _3j ;

S05: Finally, calculate the tangential coefficient d _vi through linear fitting.

A better implementation includes the following steps:

1) Fix the three-dimensional force sensor on the fixed base of the test platform;

2) Install the test terminal on the three-dimensional force sensor;

3) For the calibration of the tangential coefficient, as shown in Figure 4, by moving the push rod body, the push rod head applies horizontal force to the test terminal on the normal plane, and at the same time, the turntable is controlled to rotate so that the push rod head exerts force in the positive direction. For the strain gauge circuit to be tested;

4) Taking the 0° corresponding strain gauge circuit as an example, apply a set of forces F _j (j=1,2,...,N) of different sizes, and calculate the output voltage change value ΔV _1j (j=1,2 of the strain gauge circuit) ,...,N);

5) According to the force measurement principle formula, there is a linear relationship d _v1 between F _j and ΔV _1i . Therefore, the tangential coefficient d _v1 can be calculated through linear fitting. The other two tangential coefficients are the same;

6) For the calibration of the normal coefficient, as shown in Figure 5, the calibration method is similar to the tangential coefficient. Make the test platform and the plane of the calibration equipment at 90°, and apply a set of different sizes vertically downward on the force-bearing terminal. The force F _j (j=1,2,…,N), similarly, the voltage change values ΔV _1j , ΔV _2j , ΔV _3j (j=1,2,…,N) of the strain gauge circuit at three different angles were measured ;

7) Finally, calculate the tangential coefficient d _vi (i=1,2,3) through linear fitting.

8) The whole process adopts dynamic calibration method. The above process of applying force can be described as: the push rod head advances at a constant speed when it contacts the test terminal, that is, a force with a constant rate of change is applied to the test terminal, and the push rod body stops when it reaches the upper limit of the force measurement. During this process, the host computer continuously collects data from the three strain gauge circuits of the single-dimensional force sensor and the three-dimensional force sensor to be calibrated.

9) After removing the nonlinear part of the measured data, fit its linear characteristics through the least squares method. As shown in Figure 6 below, the output voltage of the three strain gauge circuits collected has an obvious linear relationship with the force value.

In yet another embodiment, a computer storage medium has a computer program stored thereon. When the computer program is executed, the above-mentioned calibration method of the three-dimensional force sensor is implemented.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications may be made without departing from the spirit and principles of the present invention. , should be equivalent replacement methods, and are included in the protection scope of the present invention.

Claims (9)

1. The calibration equipment of the three-dimensional force sensor is characterized by comprising a test cradle head and a force application structure, wherein the test cradle head and the force application structure are arranged on a test platform; the test cradle head is provided with a three-dimensional force sensor to be calibrated, and the three-dimensional force sensor to be calibrated is provided with a test terminal;

the testing cradle head comprises a single rocker arm structure, a rotary table and a fixed base, wherein the rotary table and the fixed base are arranged on the single rocker arm structure, the single rocker arm structure is rotatably arranged at the upper end of the first bracket, the rotary table is rotatably arranged on the single rocker arm structure, the single rocker arm structure changes a normal angle through rotation, the rotary table changes a tangential angle through rotation, and the fixed base is fixed on the rotary table and rotates along with the rotary table;

the force application structure comprises a transverse sliding mechanism, a longitudinal sliding mechanism, a single-dimensional force sensor, a push rod main body and a push rod head, wherein one end of the single-dimensional force sensor is fixed on the push rod head, the other end of the single-dimensional force sensor is fixed on the push rod main body, the push rod main body is arranged on the transverse sliding mechanism, the transverse sliding mechanism is used for horizontally moving the push rod head so as to apply force to the test terminal, and the force is measured through the single-dimensional force sensor and fed back to the upper computer.

2. The calibration device of a three-dimensional force sensor according to claim 1, wherein the test terminal comprises a spherical structure for loading force and a connecting column connected with the spherical structure, the connecting column is provided with a screw hole, and the sensor to be calibrated is connected with the connecting column in a pre-tightening mode through a screw.

3. The apparatus for calibrating a three-dimensional force sensor according to claim 2, wherein the pusher head is a cylinder with a concave spherical structure at a front end.

4. A calibration device for a three-dimensional force sensor according to claim 3, wherein the concave spherical structure fully encloses the spherical structure of the test terminal.

5. The calibration device of a three-dimensional force sensor according to claim 1, wherein the sensor to be calibrated is mounted on a fixed base of the test cradle head, and the inside of the sensor to be calibrated is composed of three 120-degree distributed strain gauge circuits and a measuring circuit, and the measuring circuit is communicated with an upper computer.

6. A calibration test system for a three-dimensional force sensor, which is characterized by comprising the calibration equipment for the three-dimensional force sensor and an upper computer, wherein the calibration flow is arranged in the upper computer, the calibration equipment is controlled to perform automatic calibration, data writing and factory testing according to the built-in calibration flow, and meanwhile, a curve of calibration data is fitted by utilizing linearity.

7. A method for calibrating a three-dimensional force sensor, characterized in that the three-dimensional force sensor testing system according to claim 6 is used, the calibrating method comprising the following steps:

s01: through moving the push rod main body, the push rod head horizontally applies force to the test terminal on a normal plane, and simultaneously the turntable is controlled to rotate, so that the force application direction of the push rod head is opposite to the to-be-tested strain gauge circuit;

s02: applying a set of forces F of different magnitudes to the force terminals _j Calculating the change value delta V of the output voltage of the strain gauge circuit _1j ；

S03: by means of linear fitting, the tangential coefficient d is calculated _vi The calibration of the tangential coefficient is completed;

s04: the test cradle head forms 90 degrees with the plane of the calibration equipment, and a group of forces F with different magnitudes are exerted on the stress terminal vertically downwards _j Similarly, three different angles of the voltage change value DeltaV of the strain foil circuit are measured _1j ，ΔV _2j ，ΔV _3j ；

S05: finally, calculating tangential coefficient d by means of linear fitting _vi 。

8. The method for calibrating a three-dimensional force sensor according to claim 7, wherein the method for applying force in steps S02 and S04 comprises: the push rod head advances at a constant speed when contacting the test terminal, namely, a constant-rate-of-change force is applied to the test terminal, and the push rod main body stops when the upper limit of force measurement is reached; in the process, the upper computer continuously collects data of the three strain gauge circuits of the single-dimensional force sensor and the three-dimensional force sensor to be calibrated.

9. A computer storage medium having a computer program stored thereon, wherein the computer program, when executed, implements the method of calibrating a three-dimensional force sensor according to claim 7.