A method for compensating temperature drift of joint force sensors of space station manipulators

Abstract

This invention discloses a method for compensating for temperature drift of joint force sensors in a space station robotic arm. First, the test values ​​of the force sensors at different joint angles under various gradient distributions are recorded under no-load conditions. Then, based on the test values ​​at different joint angles, the coefficients in the temperature drift compensation function for each test temperature are determined, resulting in the temperature drift compensation function for each test temperature. Finally, the current temperature compensation value is obtained by interpolation using the temperature drift compensation functions for each test temperature. This invention enables rapid and accurate compensation for temperature drift of joint force sensors, solving the problem that commonly used compensation methods cannot couple with joint angle states, and is suitable for on-orbit missions of space station robotic arms.

Description

Technical Field

[0001] The present invention belongs to the field of space manipulator / robot technology and relates to a method for compensating temperature drift of a joint force sensor of a space station manipulator, which is used to compensate for the temperature drift phenomenon of the joint force sensor caused by the influence of high and low temperature environment in space. Background Art

[0002] One-dimensional force sensors are designed and integrated in the joints of the space station's robotic arms to complete the closed-loop control of the joint torque in the robotic arm force control mode. Affected by the high and low temperature environment in space, the joint structure has periodic strain, which will cause the joint force sensor to drift. If the temperature drift of the force sensor is not compensated, the actual state of the joint torque will deviate greatly from the expected state, affecting the perception of the robotic arm's joint torque state and the implementation of on-orbit missions.

[0003] After searching the relevant literature, many studies have used the table lookup method to complete the compensation of the temperature drift of the force sensor, that is, using the temperature sensor to obtain the current temperature state, and then looking up the table to obtain the force sensor zero point compensation coefficient to complete the temperature drift compensation. However, due to the influence of special factors such as the space environment and the design state of the robotic arm joints, as the joints move, the joint structure strains at different joint angles are significantly different, so the force sensor temperature drift should be compensated for different states, that is, the temperature drift compensation coefficient is related to both temperature and joint angle, and the existing methods in the literature are not suitable. Therefore, a fast and accurate joint force sensor temperature drift compensation method is needed, which is crucial for the implementation of the on-orbit mission of the space station robotic arm. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects and provide a method for compensating the temperature drift of the joint force sensor of a space station manipulator arm, which solves the problem that the commonly used compensation methods cannot couple the joint angle state, and can realize fast and accurate compensation for the temperature drift of the joint force sensor. At the same time, it has high calculation efficiency and high compensation accuracy, and is suitable for the implementation of on-orbit missions of the space station manipulator arm.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] Firstly, record the force sensor test values ​​at different joint angles under each gradient distribution test temperature in the no-load state; determine the coefficients in the temperature drift compensation function at each test temperature according to the force sensor test values ​​at different joint angles, and obtain the temperature drift compensation function at each test temperature; interpolate the temperature drift compensation function at each test temperature to obtain the current temperature compensation value.

[0007] Specifically, a method for compensating temperature drift of a space station manipulator joint force sensor includes:

[0008] In the working temperature range of the robot arm, select m test temperatures T1, T2, ...T with gradient changes.m ;

[0009] When the robot arm is unloaded, at each test temperature, record the force sensor test values ​​at different joint angles;

[0010] Establish a temperature drift compensation function for the joint angle, determine the coefficient of the temperature drift compensation function at each test temperature according to the test value of the force sensor at different joint angles, and obtain the temperature drift compensation function at each test temperature;

[0011] During the actual operation of the robot arm, the current temperature is T and the current joint angle is θ now , when T∈[T q ,T q+1 ], according to the test temperature T q Temperature drift compensation function and test temperature T q+1 The temperature drift compensation function under the temperature T q , joint angle θ now Temperature compensation value at and temperature T q+1 , joint angle θ now Temperature compensation value at 1≤q<m;

[0012] according to and Interpolate to get the current temperature compensation value

[0013] Using the current temperature compensation value Compensate the actual measured value of the current force sensor.

[0014] Furthermore, the temperature drift compensation function is a fitting function based on a sine function.

[0015] Furthermore, the temperature drift compensation function is a fitting function using a superimposed sine function:

[0016]

[0017] in, Indicates temperature T q Bottom: Fitting value of the force sensor when the joint angle is θ, n represents the number of groups of sine functions, n>1; A i , B i , C i is the coefficient in the temperature drift compensation function, where A i represents the amplitude of the sine function, B i represents the joint angle coefficient, C i Represents the translation of the sine function, 1≤i≤n;

[0018] Furthermore, n=2~6.

[0019] Furthermore, the coefficients in the temperature drift compensation function at each test temperature are determined according to the test values ​​of the force sensor at different joint angles. The specific method for obtaining the temperature drift compensation function at each test temperature is:

[0020]

[0021] Among them, δ j is the temperature T q Next, the joint angle is θ j The force sensor fitting value at With temperature T q Next, the joint angle is θ j Force sensor test value at The residual between 1≤j≤N, N is the temperature T q The total number of different joint angles.

[0022] Further, at each test temperature, the force sensor test values ​​recorded at different joint angles include: the force sensor test values ​​τ at different joint angles during the joint forward motion process 正向 And the force sensor test value τ at different joint angles during joint reverse motion 反向 ;

[0023] The temperature drift compensation function at each test temperature includes a forward temperature drift compensation function and a reverse temperature drift compensation function; wherein the coefficient in the forward temperature drift compensation function is calculated according to τ 正向 Determine that the reverse temperature drift compensation function is based on τ 反向 Sure;

[0024] During the actual operation of the robot arm, the current joint angle θ is first determined now is the joint angle during the joint forward motion or the joint reverse motion, and the temperature T is obtained according to the corresponding forward temperature drift compensation function or reverse temperature drift compensation function. q , joint angle θ now Temperature compensation value at and temperature T q+1 , joint angle θ now Temperature compensation value at

[0025] Further, the joint is moved forward from -180° to 180° to obtain a set of force sensor test values ​​at different joint angles; this step is repeated ≥ 3 times to obtain multiple sets of force sensor test values ​​at different joint angles, and the multiple sets of force sensor test values ​​at different joint angles are averaged to obtain the force sensor test values ​​τ at different joint angles during the joint forward motion process. 正向 ;

[0026] Make the joint move in the opposite direction from 180° to -180°, and obtain a set of force sensor test values ​​at different joint angles; repeat this step ≥ 3 times to obtain multiple sets of force sensor test values ​​at different joint angles, and average the multiple sets of force sensor test values ​​at different joint angles to obtain the force sensor test values ​​τ at different joint angles during the joint reverse movement process 反向 .

[0027] Further, according to and Interpolate to get the current temperature compensation value The specific method is:

[0028]

[0029] Furthermore, using the current temperature compensation value The specific method for compensating the actual measured value of the current force sensor is to subtract the actual measured value of the current force sensor from

[0030] Furthermore, m test temperatures T1, T2, ...T m The temperature difference between two adjacent tests is 20 to 40°C.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention creatively uses the test value of the force sensor in the no-load state to establish a temperature drift compensation function for the joint angle, thereby solving the problem that the commonly used compensation method cannot couple the joint angle state. At the same time, the compensation function is simple, the calculation efficiency is high, and the compensation accuracy is high, which is suitable for the on-orbit mission implementation of the space station manipulator arm;

[0033] (2) The present invention sets the temperature drift compensation function as a fitting function of the superimposed sine function at each test temperature, and completes the superimposed sine function coefficient fitting through the least squares fitting algorithm, which simplifies the compensation method and greatly improves the compensation accuracy;

[0034] (3) The present invention adopts an interpolation method and uses the temperature drift compensation function at each test temperature to obtain the temperature drift compensation value of any temperature and any angle within each test temperature range. On the basis of ensuring high compensation accuracy, it has universal applicability;

[0035] (4) The present invention takes into account the forward and reverse motions of the joints, making the compensation results closer to the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Force sensor test results for joint motion at the same joint angle and different test temperatures;

[0037] Figure 2 The force sensor test results of the present invention at the same temperature and at different joint angles during the forward and reverse motion of the joint;

[0038] Figure 3 It is a comparison curve between the temperature drift compensation value obtained by the present invention and the theoretical temperature drift compensation value when the joint moves in the forward angle;

[0039] Figure 4 The figure is a comparison curve between the temperature drift compensation value obtained by the present invention and the theoretical temperature drift compensation value when the joint moves at a reverse angle. DETAILED DESCRIPTION

[0040] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0041] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0042] Since temperature drift compensation is related to the joint temperature environment and the joint rotation angle state, the present invention first completes the force sensor test of the joint movement at different temperature values ​​(distributed according to the gradient) under the no-load state; according to the joint design state, a temperature drift compensation function for the joint angle is established; the temperature drift compensation function coefficient fitting is completed to determine the temperature drift compensation function based on the joint angle; in actual application, the joint collects the current temperature and angle, and obtains the temperature drift compensation value according to the upper and lower limits of the temperature interval to which the current temperature belongs, and after interpolation of the temperature interval, it is used as the temperature drift compensation value of the current temperature.

[0043] Specifically, a method for compensating temperature drift of a space station manipulator joint force sensor of the present invention includes:

[0044] First, complete the force sensor test of joint movement in different temperature ranges under no-load state. Take a series of temperatures with gradient changes within the working temperature range as the test temperature. When the ambient temperature is stable, record the force sensor test value at each test temperature and different joint angles during joint movement. Since the theoretical value of the force sensor under no-load state should be 0, the force sensor test value recorded in the above process is actually the error value generated under the combined influence of temperature and joint angle, that is, the theoretical temperature drift compensation value.

[0045] Preferably, at each test temperature, the joint can be moved forward from -180° to 180° and the test is repeated three times, and the joint can be moved backward from 180° to -180° and the test is repeated three times, and the force sensor test value τ at different joint angles during the joint forward movement is recorded. 正向And the force sensor test value τ at different joint angles during joint reverse motion 反向 .

[0046] According to the joint design status, the force sensor test value in the motion state shows a sinusoidal change trend with the joint angle value. Therefore, it is preferred to use the superimposed sine function as the fitting function, that is, the temperature drift compensation function:

[0047]

[0048] in Indicates temperature T q Bottom: Fitting value of the force sensor when the joint angle is θ, n represents the number of groups of sine functions; A i , B i , C i Three types of coefficients representing the sine function: A i represents the amplitude of the sine function, B i represents the joint angle coefficient, C i Represents the translation of the sine function.

[0049] Considering the limited computing resources of the space station manipulator and the high accuracy requirement of the fitting results, 2 to 6 groups of sine function superposition forms are preferred, and more preferably, 4 groups of sine function superposition forms are used, that is, n=4 in the above formula, and the following formula is obtained:

[0050]

[0051] In order to make the fitted approximate curve reflect the data change trend as much as possible, the residual δ at each data point (same temperature, different joint angles) is required to be j They are all relatively small.

[0052]

[0053] where δ j is the residual of the current data point, The force sensor test value of the current data point.

[0054] In order to achieve this goal, the least squares fitting algorithm is used to minimize the sum of squares of the above residuals, that is,

[0055]

[0056] Where j represents the jth data point at the same temperature and different joint angles; is the temperature T q The joint angle is θ j The force sensor fitting value at ; is the temperature T q The joint angle is θ jThe actual measured value of the force sensor at the time; N represents the total number of test data points at the same temperature and different joint angles. According to the above formula, the sine function coefficient value A can be obtained. i , B i and C i (i=1,2,3,4), that is, applicable to temperature T q The coefficients of the fitting function under the condition. For the force sensor test value τ at different joint angles during the joint forward motion 正向 And the force sensor test value τ at different joint angles during joint reverse motion 反向 , perform the above steps respectively to obtain the forward temperature drift compensation function and the reverse temperature drift compensation function at each test temperature.

[0057] The temperature drift compensation functions of the calculated temperatures T1 and T2 are recorded as and Assume that the current joint angle θ = θ now , the current temperature T∈[T1,T2], then the current temperature drift compensation value is:

[0058]

[0059] During the actual operation of the robotic arm, the motion speed value (including positive and negative signs) obtained by the rotation of the joint speed is used to determine whether the current joint angle is in the forward motion process or the reverse motion process, and the forward temperature drift compensation function or the reverse temperature drift compensation function is selected to obtain the current temperature drift compensation value.

[0060] The following is combined with Figures 1 to 4 The method of the present invention is further described.

[0061] First, we conducted force sensor tests on joint motion at the same joint angle and different test temperatures under no-load conditions. Figure 1 (a) is the change curve of different test temperatures. Figure 1 (b) for Figure 1 (a) The torque values ​​measured by the force sensor at different test temperatures are shown in Table 1. Figure 1 It can be found that the joint force sensors have temperature drift at the same joint angle and different temperatures, and it is a complex nonlinear relationship. It can be seen that the temperature drift (i.e. compensation value) of the force sensor at different temperatures is different and the difference is large. It must be compensated in practical applications, otherwise the force sensor cannot be used.

[0062] At the same temperature, the force sensor test value τ at different joint angles during joint forward motion 正向 And the force sensor test value τ at different joint angles during joint reverse motion 反向 like Figure 2 As shown, from Figure 2It can be seen that at the same temperature and different joint angles, the temperature drift curve of the joint force sensor roughly presents a sinusoidal function relationship. Therefore, the superimposed sine function is determined as the temperature drift fitting function, and its compensation function is simple and has high calculation efficiency.

[0063] The temperature drift compensation value at a certain temperature and different joint angles obtained by the calculation method of the present invention has a high approximation to the theoretical temperature drift compensation value at the temperature. The theoretical temperature drift compensation value at the temperature is the actual test value of the force sensor at different joint angles at the temperature in a no-load state. Figure 3 is the comparison curve of the joint forward angle movement, Figure 4 It is a comparison curve of joint reverse angle movement. It can be seen from the figure that the temperature drift compensation value of the superimposed sine fitting function is in good agreement with the measured data, and the maximum deviation does not exceed 10%, indicating that the compensation accuracy of the present invention is high and suitable for engineering applications.

[0064] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0065] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for compensating temperature drift of a space station manipulator joint force sensor, characterized in that: include: In the working temperature range of the robot arm, select m test temperatures T1, T2, ...T with gradient changes. m ; When the robot arm is unloaded, at each test temperature, record the force sensor test values ​​at different joint angles; Establish a temperature drift compensation function for the joint angle, determine the coefficient of the temperature drift compensation function at each test temperature according to the test value of the force sensor at different joint angles, and obtain the temperature drift compensation function at each test temperature; During the actual operation of the robot arm, the current temperature is T and the current joint angle is θ now , when T∈[T q ,T q+1 ], according to the test temperature T q Temperature drift compensation function and test temperature T q+1 The temperature drift compensation function under the temperature T q , joint angle θ now Temperature compensation value at and temperature T q+1 , joint angle θ now Temperature compensation value at 1≤q<m; according to and Interpolate to get the current temperature compensation value Using the current temperature compensation value Compensate the actual measured value of the current force sensor; The temperature drift compensation function is a fitting function using a superimposed sine function: in, Indicates temperature T q Bottom: Fitting value of the force sensor when the joint angle is θ, n represents the number of groups of sine functions, n>1; A i , B i , C i is the coefficient in the temperature drift compensation function, where A i represents the amplitude of the sine function, B i represents the joint angle coefficient, C i Represents the translation of the sine function, 1≤i≤n.

2. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 1, characterized in that: n＝2～6。 3. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 1, characterized in that: Determine the coefficients in the temperature drift compensation function at each test temperature based on the force sensor test values ​​at different joint angles. The specific method for obtaining the temperature drift compensation function at each test temperature is as follows: Among them, δ j is the temperature T q Next, the joint angle is θ j The force sensor fitting value at With temperature T q Next, the joint angle is θ j Force sensor test value at The residual between 1≤j≤N, N is the temperature T q The total number of different joint angles.

4. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 1, characterized in that: At each test temperature, the force sensor test values ​​recorded at different joint angles include: force sensor test values ​​τ at different joint angles during joint forward motion 正向 And the force sensor test value τ at different joint angles during joint reverse motion 反向 ; The temperature drift compensation function at each test temperature includes a forward temperature drift compensation function and a reverse temperature drift compensation function; wherein the coefficient in the forward temperature drift compensation function is calculated according to τ 正向 Determine that the reverse temperature drift compensation function is based on τ 反向 Sure; During the actual operation of the robot arm, the current joint angle θ is first determined now is the joint angle during the joint forward motion or the joint reverse motion, and the temperature T is obtained according to the corresponding forward temperature drift compensation function or reverse temperature drift compensation function. q , joint angle θ now Temperature compensation value at and temperature T q+1 , joint angle θ now Temperature compensation value at 5. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 4, characterized in that: Make the joint move forward from -180° to 180°, and obtain a set of force sensor test values ​​at different joint angles; Repeat this step ≥ 3 times to obtain multiple groups of force sensor test values ​​at different joint angles. Average the multiple groups of force sensor test values ​​at different joint angles to obtain the force sensor test value τ at different joint angles during the joint forward motion process. 正向 ; Make the joint move in the opposite direction from 180° to -180°, and obtain a set of force sensor test values ​​at different joint angles; Repeat this step ≥ 3 times to obtain multiple groups of force sensor test values ​​at different joint angles. Average the multiple groups of force sensor test values ​​at different joint angles to obtain the force sensor test value τ at different joint angles during the joint reverse motion process. 反向 .

6. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 1, characterized in that: according to and Interpolate to get the current temperature compensation value The specific method is:

7. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 1, characterized in that: Using the current temperature compensation value The specific method for compensating the actual measured value of the current force sensor is to subtract the actual measured value of the current force sensor from 8. A method for compensating temperature drift of a space station manipulator joint force sensor according to claim 1, characterized in that: m test temperatures T1, T2, ...T with gradient change m The temperature difference between two adjacent tests is 20 to 40°C.

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