Double-encoder high-precision calibration positioning technology based on motor and harmonic reducer

Abstract

The invention discloses a double-encoder high-precision calibration positioning technology based on a motor and a harmonic reducer. A positioning method comprises the following steps that a grating encoder and an absolute value magnetic encoder which are applied to a joint of a cooperative mechanical arm are included; wherein the grating encoder is installed at the shaft end of the motor, the absolute value magnetic encoder is installed at the shaft end of the speed reducer, when the motor runs, data of the grating encoder of the motor shaft and data of the absolute value magnetic encoder of the speed reducer shaft are recorded, the reduction ratio and the difference value between the concentricity of the speed reducer and the gear clearance are removed from the value of the grating encoder, and the difference value changes in a sinusoidal mode. The amplitude values of the maximum value and the minimum value of the difference value and the magnetic position value of the maximum value of the difference value are recorded, and the value of the absolute value magnetic encoder is compensated by the value of the grating encoder through fitting sine function calculation, so that the difference value between the absolute value magnetic encoder and the grating encoder is reduced. According to the double-encoder high-precision calibration positioning technology based on the motor and the harmonic reducer, the absolute positioning precision of the joint can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical arms, and in particular to a high-precision calibration and positioning technology of dual encoders based on a motor and a harmonic reducer. Background Art

[0002] In recent years, collaborative robotic arms have been widely used, including welding, palletizing, and various unmanned collaborative scenarios. As their applications become more and more extensive, the requirements for robot positioning accuracy are also getting higher and higher. In order to ensure the high precision of robot positioning, the collaborative robotic arm joints manufactured by Jicui use high-precision grating encoders on the motor shaft end and absolute magnetic encoders on the reducer shaft end to ensure the positioning accuracy of the joints.

[0003] However, the existing robotic arms have the following problems in the process of adjusting and positioning: Since the absolute positioning accuracy and repeat positioning accuracy of the joints depend on the accuracy of the grating encoder and the absolute value magnetic encoder, and are also related to the concentricity of the reducer shaft and the motor shaft, the gear clearance of the reducer, etc., the positioning of the joints is only based on the traditional reducer shaft magnetic encoder method, and the positioning accuracy will be poor. Therefore, it is necessary to design corresponding technical solutions to solve the existing technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide a high-precision calibration and positioning technology based on a dual encoder of a motor and a harmonic reducer, which solves the problem that the absolute positioning accuracy and repeated positioning accuracy of the joint depend on the accuracy of the grating encoder and the absolute value magnetic encoder, and are also related to the concentricity of the reducer shaft and the motor shaft, the gear clearance of the reducer, etc. Therefore, the positioning of the joint only relies on the traditional magnetic encoder method of the reducer shaft, and the positioning accuracy will be poor. This technical problem is solved by using a dual encoder method and an optical encoder of the motor shaft to compensate for the positioning deviation problem caused by the magnetic encoder of the reducer shaft due to the influence of the reducer.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: Based on the high-precision calibration positioning technology of dual encoders of motors and harmonic reducers, the positioning method is as follows:

[0006] Including grating encoders and absolute magnetic encoders used in collaborative robot arm joints;

[0007] Wherein, the grating encoder is installed on the motor shaft end, and the absolute value magnetic encoder is installed on the reducer shaft end;

[0008] When the motor is running, the data of the grating encoder of the motor shaft and the absolute magnetic encoder of the reducer shaft are recorded. The value of the grating encoder is divided by the reduction ratio to calculate the difference with the reducer magnetic encoder. The difference changes sinusoidally. The maximum and minimum amplitudes of the difference and the magnetic encoder position value of the maximum difference are recorded. The sine function is fitted and calculated. The value of the absolute magnetic encoder is compensated by the fitted difference, thereby reducing the difference between the two.

[0009] As a preferred embodiment of the present invention, during the calibration operation, the motor is rotated to a certain speed, and the data of the magnetic encoder and the error value data of the optical encoder and the magnetic encoder are output. When the magnetic encoder rotates one circle, the error value is one cycle of a sine wave, and the data value of the magnetic encoder and the error value of the optical encoder and the magnetic encoder are displayed through MATLAB.

[0010] As a preferred embodiment of the present invention, the current magnetic encoding value is compensated according to the sine fitting function of the weight 2 to eliminate the error. The error function is:

[0011] The amplitude of the sine function is a*sin((x+phase b of the sine function (pulse value)) / half-turn data of the magnetic encoder*3.1415);

[0012] Where a=(Y wave peak value-Y wave valley value) / 2, b=X wave peak value, so the compensated magnetic encoding value=current magnetic encoding value+error function value.

[0013] As a preferred embodiment of the present invention, after compensating the value of the magnetic encoding according to weight 3, the difference between the optical encoding value and the compensated magnetic encoding value is output again to obtain the compensated difference, which is greatly reduced, thereby reducing the difference between the optical encoding and the magnetic encoding and weakening the influence of the reducer concentricity and gear clearance.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. When the motor is running, the present invention records the data of the optical encoder of the motor shaft and the magnetic encoder of the reducer shaft, and divides the reduction ratio by the value of the optical encoder. The data obtained should theoretically be the same as the value of the magnetic encoder. However, due to the influence of the reducer concentricity, gear clearance and the like, there is a difference between the two, and the difference often changes sinusoidally. This scheme records the amplitude of the maximum and minimum values ​​of the difference, as well as the magnetic encoder position value of the maximum value of the difference, and calculates through fitting a sinusoidal function, and uses the value of the optical encoder to compensate for the value of the magnetic encoder, thereby reducing the difference between the two.

[0016] 2. The dual encoder high-precision calibration and positioning technology based on the motor and harmonic reducer designed in the present invention can effectively improve the absolute positioning accuracy of the joint, and is easy to implement in engineering, weakens the influence of the concentricity error of the reducer assembly on the accuracy and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a difference data diagram of magnetic encoding and optical encoding of the present invention;

[0018] Figure 2 It is a schematic diagram of the magnetic encoding data value (Y axis) and the optical encoding error value (X axis) of the present invention;

[0019] Figure 3 It is a schematic diagram of the difference between the compensated optical encoding and magnetic encoding of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] See also Figure 1-3 The present invention provides a technical solution: a high-precision calibration positioning technology of dual encoders based on motors and harmonic reducers, and the positioning method is as follows:

[0022] Including grating encoders and absolute magnetic encoders used in collaborative robot arm joints;

[0023] Wherein, the grating encoder is installed on the motor shaft end, and the absolute value magnetic encoder is installed on the reducer shaft end;

[0024] When the motor is running, the data of the grating encoder of the motor shaft and the absolute magnetic encoder of the reducer shaft are recorded. The value of the grating encoder is divided by the reduction ratio to calculate the difference with the reducer magnetic encoder. The difference changes sinusoidally. The maximum and minimum amplitudes of the difference and the magnetic encoder position value of the maximum difference are recorded. The sine function is fitted and calculated. The value of the absolute magnetic encoder is compensated by the fitted difference, thereby reducing the difference between the two.

[0025] During the calibration operation, the motor is turned to a certain speed, and the data of the magnetic encoder and the error value data of the optical encoder and the magnetic encoder are output. When the magnetic encoder rotates one circle, the error value is one cycle of a sine wave, and the data value of the magnetic encoder and the error value of the optical encoder and the magnetic encoder are displayed through MATLAB.

[0026] According to the sine fitting function from weight 2, the current magnetic encoding value is compensated to eliminate the error. The error function is:

[0027] The amplitude of the sine function is a*sin((x+phase b of the sine function (pulse value)) / half-turn data of the magnetic encoder*3.1415);

[0028] Where a=(Y wave peak value-Y wave valley value) / 2, b=X wave peak value, so the compensated magnetic encoding value=current magnetic encoding value+error function value.

[0029] Specifically, according to weight 3, after compensating the value of the magnetic encoding, the difference between the optical encoding value and the compensated magnetic encoding value is output again to obtain the difference after compensation. The difference is greatly reduced, thereby reducing the difference between the optical encoding and the magnetic encoding, and weakening the influence of the reducer concentricity and gear clearance.

[0030] When in use: When the motor is running, record the data of the optical encoder of the motor shaft and the magnetic encoder of the reducer shaft, and remove the reduction ratio from the optical encoder value. Theoretically, the data obtained should be the same as the magnetic encoder value, but due to the influence of the reducer concentricity, gear clearance, etc., there is a difference between the two, and the difference often changes sinusoidally. By recording the amplitude of the maximum and minimum values ​​of the difference, as well as the magnetic encoder position value of the maximum value of the difference, the optical encoder value is used to compensate the magnetic encoder value through the fitting sine function calculation, thereby reducing the difference between the two. Turn the motor to a certain speed, output the magnetic encoder data, and the error value data of the optical encoder and the magnetic encoder are displayed graphically, such as Figure 1 The difference between the magnetic code and the optical code. When the magnetic code rotates one circle, the error value is one cycle of a sine wave. Figure 2 The data value of the magnetic encoder (Y axis) and the error value of the optical encoder and magnetic encoder (X axis) displayed by MATLAB are used to compensate the current magnetic encoder value and eliminate the error through the sinusoidal fitting function. The error function is: the amplitude of the sinusoidal function a*sin((x+phase b of the sinusoidal function (pulse value)) / half-turn data of the magnetic encoder*3.1415), where a=(Y wave peak value-Y wave valley value) / 2, b=X wave peak value, so the compensated magnetic encoder value=current magnetic encoder value+error function value. After compensating the magnetic encoder value, the difference between the optical encoder value and the compensated magnetic encoder value is output again, as follows Figure 3 It can be seen that the difference between the two is reduced from 522 to 65, which greatly eliminates the difference between optical encoding and magnetic encoding, weakens the influence of reducer concentricity and gear clearance. After compensating the value of magnetic encoding, the test found that the joint's repeatability and absolute positioning accuracy are significantly improved.

[0031] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0032] In addition, the terms "first", "second", "third" and "fourth" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", "third" and "fourth" may explicitly or implicitly include at least one of such features.

[0033] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0034] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Dual encoder high-precision calibration positioning technology based on motor and harmonic reducer, characterized by: The positioning method is as follows: Including grating encoders and absolute magnetic encoders used in collaborative robot arm joints; Wherein, the grating encoder is installed on the motor shaft end, and the absolute value magnetic encoder is installed on the reducer shaft end; When the motor is running, the data of the grating encoder of the motor shaft and the absolute magnetic encoder of the reducer shaft are recorded. The value of the grating encoder is divided by the reduction ratio to calculate the difference with the reducer magnetic encoder. The difference changes sinusoidally. The maximum and minimum amplitudes of the difference and the magnetic encoder position value of the maximum difference are recorded. The sine function is fitted and calculated. The value of the absolute magnetic encoder is compensated by the fitted difference, thereby reducing the difference between the two.

2. The high-precision calibration positioning technology of dual encoders based on motors and harmonic reducers according to claim 1 is characterized in that: During the calibration operation, the motor is turned to a certain speed, and the data of the magnetic encoder and the error value data of the optical encoder and the magnetic encoder are output. When the magnetic encoder rotates one circle, the error value is one cycle of a sine wave, and the data value of the magnetic encoder and the error value of the optical encoder and the magnetic encoder are displayed through MATLAB.

3. The high-precision calibration positioning technology of dual encoders based on motors and harmonic reducers according to claim 1 is characterized in that: According to the sine fitting function from weight 2, the current magnetic encoding value is compensated to eliminate the error. The error function is: The amplitude of the sine function is a*sin((x+phase b of the sine function (pulse value)) / half-turn data of the magnetic encoder*3.1415); Where a=(Y wave peak value-Y wave valley value) / 2, b=X wave peak value, so the compensated magnetic encoding value=current magnetic encoding value+error function value.

4. The high-precision calibration and positioning technology of dual encoders based on motors and harmonic reducers according to claim 1 is characterized in that: According to weight 3, after compensating the value of the magnetic encoder, the difference between the optical encoder value and the compensated magnetic encoder value is output again to obtain the compensated difference, which is greatly reduced, thereby reducing the difference between the optical encoder and the magnetic encoder and weakening the influence of the reducer concentricity and gear clearance.

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