A load force test calibration method for a stepper motor

Abstract

The present application aims to provide a kind of stepper motor load force test calibration method with high test precision and wide application range.The present application includes test device, the test device includes mounting frame, load assembly and product clamp, the mounting frame is provided with loading slot matched with the product clamp, the product clamp is provided with nut slider and screw rod assembly, the motor to be measured is matched and connected on the product clamp and drives the nut slider to move linearly through the screw rod assembly, the side of the loading slot is provided with distance measuring sensor matched with the nut slider, and the force output end of the load assembly is limit matched with the nut slider;The present application further includes the following specific steps in turn: the product to be measured is assembled;Product is turned on and reset;Calculate correction parameter;Verify the error interval of the product after correction.The present application is applied to the technical field of motor test.

Description

Technical Field

[0001] This invention relates to the technical field of motor testing, and in particular to a method for calibrating the load force of a stepper motor. Background Technology

[0002] In controlling motors such as stepper motors, post-production testing is necessary to ensure the correctness of motor parameters. Load force testing, in particular, primarily assesses the motor's displacement accuracy under load. This metric is a key indicator of the motor's stability and reliability, directly impacting product quality assessment. Currently, most industry testing solutions for similar motors use disposable fixtures, which are incompatible between different products. Data acquisition is achieved indirectly by measuring the motor's output displacement using a linear encoder, which cannot directly reflect the actual displacement and lacks the required accuracy for testing.

[0003] Therefore, a stepper motor load force testing and calibration method that can improve testing accuracy and has a wide range of applications is needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a stepper motor load force testing and calibration method with high testing accuracy and wide applicability.

[0005] The technical solution adopted in this invention is as follows: This invention includes a testing device, which comprises a mounting frame, a load assembly, and a product fixture. The mounting frame is provided with a loading groove adapted to the product fixture. The product fixture is provided with a nut slider and a lead screw assembly. The motor under test is connected to the product fixture and drives the nut slider to move linearly through the lead screw assembly. A distance sensor that cooperates with the nut slider is provided on one side of the loading groove. The force output end of the load assembly is limited to the nut slider. This invention also includes the following specific steps: Step S1: After connecting the motor to be tested to the product fixture, load the product fixture into the loading slot and fix it. Step S2: Turn on the motor under test and control the motor under test to drive the nut slider to reset; Step S3: After the nut slider is reset, connect the load component to the nut slider to achieve a limiting fit, and at the same time activate and initialize the ranging sensor; Step S4: Set several different test load parameters according to the parameters and requirements of the motor under test, and apply the corresponding load to the nut slider through the load component; after each load adjustment is completed, start the motor under test to drive the nut slider to make linear displacement, and record the resistance data of the motor under test, as well as the displacement data of the nut slider by the distance sensor. Step S5: Calculate the calibration parameters based on the data collected in step S4; Step S6: Generate a calibration compensation file based on the obtained calibration parameters and substitute it into the control parameters of the motor under test. Drive the motor under test with the calibrated control parameters and collect data again to calculate the position error. Step S7: Perform repeated verification. Once verification is complete, the process ends.

[0006] As can be seen from the above scheme, the product fixture is limited by the loading slot on the mounting bracket. When the product under test is connected to the product fixture, it is simultaneously connected to the lead screw assembly, thereby driving the nut slider, which is slidably mounted on the product fixture, to make a linear displacement. The distance sensor detects the distance to the nut slider, and the displacement distance of the nut slider is obtained based on the distance change. The high-precision distance measurement of the distance sensor directly obtains the displacement, ensuring that the measurement accuracy meets the requirements. The load component is used to apply force to the nut slider during measurement, thereby simulating the application of load when driving the motor under test, meeting the testing requirements of the motor under test. In addition, the product fixture is used for clamping and displacement conversion of the motor under test. When adapting to different products, the product fixture can be replaced. The load component, mounting bracket, distance sensor, and conductive structure can all be reused, effectively reducing the changeover cost and effectively improving the applicability of the testing device. The above specific steps are used to record the displacement data of the motor under test under load, and to obtain stable and accurate deviation data through repeated tests under different load conditions. The control parameters of the motor under test are then calculated by linear regression to generate calibration parameters, thereby achieving the calibration of the motor under test.

[0007] A preferred embodiment is that, in step S4, after the load adjustment is completed, at least three displacement actions of the motor under test are performed with the current load value, and the average value of the second displacement action and subsequent displacement action data is taken as the test data of the current load value.

[0008] A further preferred embodiment is that, in step S4, the difference between the data recorded for each action and the average value of the displacement data under the lowest load condition is calculated and denoted as the abs value, which is the displacement deviation between the current load and the low load condition; the difference between the data recorded for each action and the average value of the displacement data under the current load parameter is calculated and denoted as the rel value, which is the displacement deviation between the current action and the average value under the same load. Detailed Implementation

[0009] In this embodiment, the present invention includes a testing device comprising a mounting frame, a load assembly, and a product fixture. The mounting frame has a loading slot adapted to the product fixture. The product fixture has a nut slider and a lead screw assembly. The motor under test is connected to the product fixture and drives the nut slider to move linearly via the lead screw assembly. A distance sensor cooperating with the nut slider is provided on one side of the loading slot. The force output end of the load assembly is engaged with the nut slider for limiting. During testing, the motor under test is first loaded into the product fixture, ensuring a transmission connection between the motor and the lead screw assembly. Then, the product fixture is loaded into the loading slot for limiting, completing loading, conduction, and initialization. Finally, the force output end of the load assembly is connected to the nut slider. After starting the test, the load assembly applies a load force to the nut slider according to a set direction and magnitude. The distance sensor is a Keyence_CL-P030N laser coaxial displacement meter, ensuring the accuracy of the displacement measurement of the nut slider. The load assembly includes a voice coil motor. The movable end of the voice coil motor is connected to a connecting block via a metal spring. The connecting block is detachably engaged with the nut slider. During testing, the connecting block is fastened onto the nut slider, and the voice coil motor accurately outputs the load force, which is then transmitted to the nut slider sequentially through the metal spring and the connecting block.

[0010] The present invention also includes the following specific steps: Step S1: Connect the motor to be tested to the product fixture and make it drively connected to the lead screw assembly. Then load the product fixture into the loading slot and fix it. Step S2: Control the conductive structure to make contact with several pins of the motor under test; after the connection is completed, control the motor under test to run so that it drives the nut slider to move to the end of the stroke to stall, thereby completing the reset; Step S3: After the nut slider is reset, the push block is connected to the nut slider to achieve a limiting fit, ensuring the stability of the load output during subsequent testing. At the same time, the ranging sensor is activated and initialized, and the position data of the reset nut slider is zeroed. Step S4: Set six load parameters: 140gF, 100gF, 30gF, -30gF, -100gF, and -140gF. Under each load condition, control the motor under test to drive the nut slider to perform reciprocating linear displacement. Record the resistance data each time the action starts, and collect the displacement data of the nut slider through the distance sensor throughout the entire action. The resistance data is used to record the working state of the motor under test, and the displacement data is used to record the displacement output effect of the motor under test. For each load parameter, the action is repeated five times. The displacement data of the first time after resetting the load parameter is discarded, and the average value of the displacement data from the second to the fifth time is taken. Calculate the difference between the data recorded for each action and the average displacement data under a 30gF load condition, and record it as the abs value, which is the displacement deviation between the current load condition and the low load condition. Calculate the difference between the data recorded for each action and the average displacement data under the current load parameters, and record it as the rel value, which is the displacement deviation between the current action and the average value under the same load. Step S5: Calculate the position characteristic quantities, including the average value, standard deviation, difference (load rising and falling phases) of the displacement data under each load parameter, and the degree of difference from the data under the 30gF load condition. Linear error calculation is performed by conducting linear regression analysis on the data to be processed to obtain the linear error evaluation parameters: coefficient of determination R², slope a, and intercept b. Specifically, the linear error calculation constructs a linear regression model y=ax+b using independent and dependent variables; the least squares method is used to fit the data to be processed to obtain the slope a and intercept b; the total sum of squares, regression sum of squares, and residual sum of squares are calculated, and the coefficient of determination R² is calculated based on the relationship between the three.

[0011] Linear coefficients are calculated, linear regression parameters are calculated based on adjacent data, and calibration parameters are obtained. The calibration parameters are used to correct the drive signal output by the drive circuit during operation and generate a calibration compensation file. Step S6: Generate a calibration compensation file based on the obtained calibration parameters and substitute it into the control parameters of the motor under test. Use a stepped stroke point to calculate the error between the actual value of the displacement data and the fitted theoretical value. Specifically, six load parameters are set as in step S4. Several specific stroke points are selected within the reciprocating stroke range of the nut slider. Under each load condition, the motor under test is controlled to drive the nut slider to move sequentially to the set specific stroke points. The action is repeated five times under each load parameter. Record the resistance data at any point in the travel range, including the initial travel point, the final travel point, and any other travel points; collect displacement data throughout the entire motion. Calculate the abs and rel values ​​of the current displacement data in the same manner as in step S4; Perform position error calculation, calculate the error between the displacement data abs value and rel value in step S6, and calculate the compensated error between the displacement data abs value and rel value after substituting the calibration parameters. Calculate the average, variance, maximum and minimum values ​​of the error data and record them in the error data document for verification during inspection. Step S7: Perform repeated verification. Set the same six load parameters as in step S4. Take several specific stroke points within the reciprocating stroke range of the nut slider. The specific stroke points are selected according to the requirements or randomly selected. Repeat the action twice under each load parameter. Record the resistance data at any point in the travel range, including the initial travel point, the final travel point, and any other travel points; collect displacement data throughout the entire motion. Calculate the average, maximum, and difference between maximum and minimum displacement data for the two actions; the first data is divided into two groups: the load increase phase and the load decrease phase. Finally, the verification is completed and the error data document is provided.

[0012] The correction parameters are calculated in steps S4 and S5, and the output of the motor under test is then corrected. The error after correction is collected in steps S6 and S7 to verify the error range of the corrected motor.

[0013] Although the embodiments of the present invention are described with reference to actual solutions, they do not constitute a limitation on the meaning of the present invention. Modifications to the embodiments and combinations with other solutions based on this specification will be obvious to those skilled in the art.

Claims

1. A method for testing and calibrating the load force of a stepper motor, characterized in that, It includes a testing device, which comprises a mounting frame, a load assembly, and a product fixture. The mounting frame has a loading slot adapted to the product fixture. The product fixture has a nut slider and a lead screw assembly. The motor under test is connected to the product fixture and drives the nut slider to move linearly through the lead screw assembly. A distance sensor that cooperates with the nut slider is provided on one side of the loading slot. The force output end of the load assembly is limited to the nut slider. The stepper motor load force testing and calibration method further includes the following specific steps: Step S1: After connecting the motor to be tested to the product fixture, load the product fixture into the loading slot and fix it. Step S2: Turn on the motor under test and control the motor under test to drive the nut slider to reset; Step S3: After the nut slider is reset, connect the load component to the nut slider to achieve a limiting fit, and at the same time activate and initialize the ranging sensor; Step S4: Set several different test load parameters according to the parameters and requirements of the motor under test, and apply the corresponding load to the nut slider through the load component; after each load adjustment is completed, start the motor under test to drive the nut slider to make linear displacement, and record the resistance data of the motor under test, as well as the displacement data of the nut slider by the distance sensor. Step S5: Calculate the calibration parameters based on the data collected in step S4; Step S6: Generate a calibration compensation file based on the obtained calibration parameters and substitute it into the control parameters of the motor under test. Drive the motor under test with the calibrated control parameters and collect data again to calculate the position error. Step S7: Perform repeated verification. Once verification is complete, the process ends.

2. The stepper motor load force testing and calibration method according to claim 1, characterized in that: In step S4, after the load adjustment is completed, at least three displacement actions of the motor under test are performed with the current load value, and the average value of the second displacement action and subsequent displacement action data is taken as the test data of the current load value.

3. The stepper motor load force testing and calibration method according to claim 2, characterized in that: In step S4, the difference between the data recorded for each action and the average value of the displacement data under the lowest load condition is calculated and denoted as the abs value, which is the displacement deviation between the current load and the low load condition. Calculate the difference between the data recorded for each action and the average displacement data under the current load parameters, and denot it as the rel value, which is the displacement deviation between the current action and the average value under the same load.