A method and system for obtaining the rolling friction coefficient of AGV polyurethane wheels

Abstract

The present invention relates to a method and system for obtaining the rolling friction coefficient of an AGV polyurethane wheel in the field of measurement and analysis technology. The method and system comprise the following steps: obtaining a disturbance factor of the polyurethane wheel vibration at different speeds and different loads; obtaining a pure rolling factor of the polyurethane wheel at different motor speeds; calculating the rolling friction coefficient based on the pure rolling factor, and calculating an error value based on the disturbance factor, thereby solving the problem of accurately measuring the rolling friction coefficient of the polyurethane wheel.

Description

Technical Field

[0001] The present invention relates to the field of measurement and analysis technology, and in particular to a method and system for obtaining the rolling friction coefficient of an AGV polyurethane wheel. Background Art

[0002] Due to the inherent properties of the material, existing polyurethane wheels produce large differences in strain under load conditions, resulting in different contact areas between the polyurethane wheels and the ground, which in turn increases the difficulty of measuring the rolling friction coefficient between the polyurethane wheels and the ground. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention provides a method and system for obtaining the rolling friction coefficient of an AGV polyurethane wheel, thereby solving the problem of accurately measuring the rolling friction coefficient of the polyurethane wheel.

[0004] In order to solve the above technical problems, the present invention is solved by the following technical solutions:

[0005] A method for obtaining the rolling friction coefficient of an AGV polyurethane wheel comprises the following steps:

[0006] Obtain the disturbance factor of the polyurethane wheel vibration under different speeds and loads;

[0007] Obtain the pure rolling factor of the polyurethane wheel at different motor speeds;

[0008] A rolling friction coefficient is calculated based on the pure rolling factor, and an error value is calculated based on the disturbance factor.

[0009] Optionally, obtaining a disturbance factor of the polyurethane wheel vibration at different speeds and different loads includes the following steps:

[0010] Measuring the normal pressure and longitudinal friction of the polyurethane wheel at different speeds and loads multiple times until the normal pressure and longitudinal friction of the polyurethane wheel converge;

[0011] Calculating multiple sets of longitudinal friction coefficients based on the normal pressure and longitudinal friction force measured multiple times, and obtaining extreme values and average values of fluctuations;

[0012] Based on the extreme value and the mean value of the fluctuation, a disturbance factor is calculated.

[0013] Optionally, the judgment of the convergence of the normal pressure and longitudinal friction of the polyurethane wheel comprises the following steps:

[0014] Setting a convergence threshold, calculating the difference between the average value of the longitudinal friction coefficient in a stationary state and the average value of the longitudinal friction coefficient in a uniform speed condition, and determining whether the difference is less than the convergence threshold;

[0015] If so, the convergence state is reached; otherwise, it is not converged and the measurement continues.

[0016] Optionally, obtaining the pure rolling factor of the polyurethane wheel at different motor speeds includes the following steps:

[0017] The motor angular velocity and the polyurethane wheel angular velocity are acquired, and a pure rolling factor is calculated based on the motor angular velocity and the polyurethane wheel angular velocity.

[0018] Optionally, calculating the error value includes the following steps:

[0019] Take the positive and negative values of the disturbance factor, calculate the product of the rolling friction coefficient and the positive and negative values, and obtain an error value with an upper limit and a lower limit.

[0020] A system for obtaining the rolling friction coefficient of an AGV polyurethane wheel, the system using any of the above-mentioned methods for obtaining the rolling friction coefficient of an AGV polyurethane wheel, comprising a disturbance factor obtaining unit, a pure rolling factor obtaining unit, and a friction coefficient unit;

[0021] The disturbance factor acquisition unit is used to obtain the disturbance factor of the polyurethane wheel vibration at different speeds and different loads;

[0022] The pure rolling factor acquisition unit is used to acquire the pure rolling factor of the polyurethane wheel at different motor speeds;

[0023] The friction coefficient unit is used to calculate a rolling friction coefficient based on the pure rolling factor and to calculate an error value based on the disturbance factor.

[0024] Optionally, the disturbance factor acquisition unit includes a measuring unit and a first calculating unit;

[0025] The measuring unit is used to measure the normal pressure and longitudinal friction of the polyurethane wheel at different speeds and different loads multiple times until the normal pressure and longitudinal friction of the polyurethane wheel converge;

[0026] The first calculation unit is used to calculate multiple sets of longitudinal friction coefficients based on the normal pressure and longitudinal friction force measured multiple times, and obtain fluctuation extreme values and average values;

[0027] The first calculation unit is further configured to calculate a disturbance factor based on the extreme value and the mean value of the fluctuation.

[0028] Optionally, the first calculation unit includes a convergence judgment unit;

[0029] The convergence judgment unit is used to set a convergence threshold, calculate the difference between the average value of the longitudinal friction coefficient in a stationary state and the average value of the longitudinal friction coefficient in a uniform speed condition, and judge whether the difference is less than the convergence threshold;

[0030] If so, the convergence state is reached; otherwise, it is not converged and the measurement continues.

[0031] Optionally, the pure rolling factor obtaining unit includes a second calculation unit;

[0032] The second calculation unit is used to obtain the motor angular velocity and the polyurethane wheel angular velocity, and calculate the pure rolling factor based on the motor angular velocity and the polyurethane wheel angular velocity.

[0033] Optionally, the friction coefficient unit includes a third calculation unit;

[0034] The third calculation unit is used to take the positive and negative values of the disturbance factor, calculate the product of the rolling friction coefficient and the positive and negative values, and obtain an error value with an upper limit and a lower limit.

[0035] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0036] By obtaining the disturbance factor of the polyurethane wheel vibration at different speeds and loads, the influence of the polyurethane wheel eccentric load on the rolling friction coefficient was considered. By measuring the pure rolling factor at different motor speeds, the problems of large polyurethane strain and mismatch between motor speed and wheel speed were solved, thereby greatly improving the accuracy of the measurement of the rolling friction coefficient between the polyurethane wheel and the ground. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0038] Example 1

[0039] A method for obtaining the rolling friction coefficient of an AGV polyurethane wheel comprises the following steps: obtaining a disturbance factor of the polyurethane wheel vibration under different speeds and different loads, specifically comprising the following steps: repeatedly measuring the normal pressure and longitudinal friction of the polyurethane wheel under different speeds and different loads until the normal pressure and longitudinal friction of the polyurethane wheel converge; calculating multiple sets of longitudinal friction coefficients based on the multiple measured normal pressures and longitudinal frictions, and obtaining fluctuation extreme values and mean values; and calculating the disturbance factor based on the fluctuation extreme values and mean values.

[0040] Due to the different applied positive pressures and running speeds, the longitudinal friction between the polyurethane wheel and the ground will also be different. Therefore, in order to obtain the influence of the vibration caused by different speeds and different loads on the fluctuation amplitude of the positive pressure and longitudinal friction of the polyurethane wheel, it is necessary to compare the average value of multiple measurements under uniform speed conditions with the positive pressure and longitudinal friction measured under static conditions, and then continuously increase the number of measurements until the measured data converges. Then, the longitudinal friction coefficient f is calculated for each set of positive pressure and longitudinal friction.c , the calculation formula is: c = Longitudinal friction / normal pressure.

[0041] Since the longitudinal friction coefficient of the polyurethane wheel fluctuates, it is necessary to take out the maximum and minimum values of the calculated longitudinal friction coefficient as the fluctuation extremes, and then calculate the fluctuation difference, where the fluctuation difference is the absolute value of the difference between the maximum / minimum value and the mean value of the longitudinal friction coefficient. After calculating the fluctuation difference, the disturbance factor can be calculated, where the disturbance factor = fluctuation difference / mean.

[0042] On the other hand, the judgment of the convergence of the positive pressure and longitudinal friction force of the polyurethane wheel includes the following steps: setting a convergence threshold, calculating the difference between the average value of the longitudinal friction coefficient in the static state and the average value of the longitudinal friction coefficient under the uniform speed condition, and judging whether the difference is less than the convergence threshold; if so, the convergence state is reached, otherwise, it has not converged and the measurement continues.

[0043] Obtaining the pure rolling factor of the polyurethane wheel at different motor speeds specifically includes the following steps: obtaining the motor angular velocity and the polyurethane wheel angular velocity, and calculating the pure rolling factor based on the motor angular velocity and the polyurethane wheel angular velocity.

[0044] Specifically, due to insufficient adhesion to the ground, when the motor rotates and drives the polyurethane wheel to rotate, there is sliding friction and rolling friction, and the faster the motor speed, the more likely it is to slip. Therefore, in order to understand the influence of sliding friction, it is necessary to first obtain the angular velocity ω of the motor rotation. w , and then measure the angular velocity ω of the polyurethane wheel m , the pure rolling factor α can be calculated, where

[0045] The rolling friction coefficient is calculated based on the pure rolling factor, and the error value is calculated based on the disturbance factor. The error value calculation includes the following steps: taking the positive and negative values of the disturbance factor, calculating the product of the rolling friction coefficient and the positive and negative values, and obtaining an error value with an upper limit and a lower limit.

[0046] Specifically, the sliding friction coefficient f is obtained by measuring s , then calculate the rolling friction coefficient f r , where the calculation formula for the rolling friction coefficient is: Then the product of the rolling friction coefficient and the positive and negative values of the disturbance factor is used as the upper and lower limits of the error respectively. If it is within the error, the rolling friction coefficient is accurate.

[0047] Example 2

[0048] A rolling friction coefficient acquisition system for an AGV polyurethane wheel, the system using the rolling friction coefficient acquisition method for an AGV polyurethane wheel as described in any one of the first embodiments, including a disturbance factor acquisition unit, a pure rolling factor acquisition unit, and a friction coefficient unit; the disturbance factor acquisition unit is used to obtain the disturbance factor of the polyurethane wheel vibration under different speeds and different loads; the disturbance factor acquisition unit includes a measuring unit and a first calculation unit; the measuring unit is used to repeatedly measure the normal pressure and longitudinal friction of the polyurethane wheel under different speeds and different loads until the normal pressure and longitudinal friction of the polyurethane wheel converge; the first calculation unit is used to calculate multiple groups of longitudinal friction coefficients based on the multiple measured normal pressures and longitudinal frictions, and obtain the fluctuation extreme value and mean value; the first calculation unit is also used to calculate the disturbance factor based on the fluctuation extreme value and mean value.

[0049] Due to the different applied positive pressures and running speeds, the longitudinal friction between the polyurethane wheel and the ground will also be different. Therefore, in order to obtain the influence of the vibration caused by different speeds and different loads on the fluctuation amplitude of the positive pressure and longitudinal friction of the polyurethane wheel, it is necessary to compare the average value of multiple measurements under uniform speed conditions with the positive pressure and longitudinal friction measured under static conditions, and then continuously increase the number of measurements until the measured data converges. Then, the longitudinal friction coefficient f is calculated for each set of positive pressure and longitudinal friction. c , the calculation formula is: c = Longitudinal friction / normal pressure.

[0050] Since the longitudinal friction coefficient of the polyurethane wheel fluctuates, it is necessary to take out the maximum and minimum values of the calculated longitudinal friction coefficient as the fluctuation extremes, and then calculate the fluctuation difference, where the fluctuation difference is the absolute value of the difference between the maximum / minimum value and the mean value of the longitudinal friction coefficient. After calculating the fluctuation difference, the disturbance factor can be calculated, where the disturbance factor = fluctuation difference / mean.

[0051] On the other hand, the first calculation unit includes a convergence judgment unit; the convergence judgment unit is used to set a convergence threshold, calculate the difference between the average value of the longitudinal friction coefficient in a stationary state and the average value of the longitudinal friction coefficient in a uniform speed condition, and judge whether the difference is less than the convergence threshold; if so, the convergence state is reached, otherwise, it has not converged and the measurement continues.

[0052] The pure rolling factor acquisition unit is used to obtain the pure rolling factor of the polyurethane wheel at different motor speeds. The pure rolling factor acquisition unit includes a second calculation unit; the second calculation unit is used to obtain the motor angular velocity and the polyurethane wheel angular velocity, and calculate the pure rolling factor based on the motor angular velocity and the polyurethane wheel angular velocity.

[0053] Specifically, due to insufficient adhesion to the ground, when the motor rotates and drives the polyurethane wheel to rotate, there is sliding friction and rolling friction, and the faster the motor speed, the more likely it is to slip. Therefore, in order to understand the influence of sliding friction, it is necessary to first obtain the angular velocity ω of the motor rotation. w , and then measure the angular velocity ω of the polyurethane wheel m , the pure rolling factor α can be calculated, where

[0054] The friction coefficient unit is used to calculate the rolling friction coefficient based on the pure rolling factor and calculate the error value based on the disturbance factor. The friction coefficient unit includes a third calculation unit; the third calculation unit is used to take the positive and negative values of the disturbance factor, calculate the product of the rolling friction coefficient and the positive and negative values, and obtain an error value with an upper limit and a lower limit.

[0055] Specifically, the sliding friction coefficient f is obtained by measuring s , then calculate the rolling friction coefficient f r , where the calculation formula for the rolling friction coefficient is: Then the product of the rolling friction coefficient and the positive and negative values of the disturbance factor is used as the upper and lower limits of the error respectively. If it is within the error, the rolling friction coefficient is accurate.

[0056] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for obtaining the rolling friction coefficient of an AGV polyurethane wheel, characterized in that: The following steps are involved: Obtaining a disturbance factor of the polyurethane wheel vibration at different speeds and different loads includes the following steps: repeatedly measuring the normal pressure and longitudinal friction of the polyurethane wheel at different speeds and different loads until the normal pressure and longitudinal friction of the polyurethane wheel converge; calculating multiple sets of longitudinal friction coefficients based on the multiple measured normal pressures and longitudinal frictions, and obtaining fluctuation extreme values and mean values; the fluctuation extreme value is the maximum or minimum value of the longitudinal friction coefficient, and the fluctuation difference is the absolute value of the difference between the fluctuation extreme value and the mean value; after calculating the fluctuation difference, the disturbance factor can be calculated, where the disturbance factor = fluctuation difference / mean value; The judgment of the convergence of the normal pressure and longitudinal friction of the polyurethane wheel includes the following steps: setting a convergence threshold, calculating the difference between the average value of the longitudinal friction coefficient in a stationary state and the average value of the longitudinal friction coefficient in a uniform speed condition, and judging whether the difference is less than the convergence threshold; if so, the convergence state is reached; otherwise, the convergence is not achieved and the measurement is continued; Obtaining the pure rolling factor of the polyurethane wheel at different motor speeds includes the following steps: obtaining the motor angular velocity and the polyurethane wheel angular velocity, and based on the motor angular velocity ω w and the polyurethane wheel angular velocity ω m Calculate the pure rolling factor α, ; Calculate the rolling friction coefficient f based on the pure rolling factor r , , where f c Indicates the longitudinal friction coefficient, and the sliding friction coefficient f is obtained by measurement s ; An error value is calculated based on the disturbance factor, wherein the error value calculation includes the following steps: taking the product of the rolling friction coefficient and the positive and negative values of the disturbance factor as the upper and lower limits of the error respectively.

2. A rolling friction coefficient acquisition system for AGV polyurethane wheels, characterized in that: The system uses the rolling friction coefficient acquisition method of the AGV polyurethane wheel as claimed in claim 1, comprising a disturbance factor acquisition unit, a pure rolling factor acquisition unit and a friction coefficient unit; The disturbance factor acquisition unit is used to obtain the disturbance factor of the polyurethane wheel vibration at different speeds and different loads; The pure rolling factor acquisition unit is used to acquire the pure rolling factor of the polyurethane wheel at different motor speeds; The friction coefficient unit is used to calculate a rolling friction coefficient based on the pure rolling factor and to calculate an error value based on the disturbance factor.

3. The rolling friction coefficient acquisition system of an AGV polyurethane wheel according to claim 2, characterized in that: The disturbance factor acquisition unit includes a measuring unit and a first calculating unit; The measuring unit is used to measure the normal pressure and longitudinal friction of the polyurethane wheel at different speeds and different loads multiple times until the normal pressure and longitudinal friction of the polyurethane wheel converge; The first calculation unit is used to calculate multiple sets of longitudinal friction coefficients based on the normal pressure and longitudinal friction force measured multiple times, and obtain fluctuation extreme values and average values; The first calculation unit is further configured to calculate a disturbance factor based on the extreme value and the mean value of the fluctuation.

4. The rolling friction coefficient acquisition system for AGV polyurethane wheels according to claim 3, characterized in that: The first calculation unit includes a convergence judgment unit; The convergence judgment unit is used to set a convergence threshold, calculate the difference between the average value of the longitudinal friction coefficient in a stationary state and the average value of the longitudinal friction coefficient in a uniform speed condition, and judge whether the difference is less than the convergence threshold; If so, the convergence state is reached; otherwise, it is not converged and the measurement continues.

5. The rolling friction coefficient acquisition system for AGV polyurethane wheels according to claim 2, characterized in that: The pure rolling factor obtaining unit includes a second calculation unit; The second calculation unit is used to obtain the motor angular velocity and the polyurethane wheel angular velocity, and calculate the pure rolling factor based on the motor angular velocity and the polyurethane wheel angular velocity.

6. The rolling friction coefficient acquisition system for AGV polyurethane wheels according to claim 2, characterized in that: The friction coefficient unit includes a third calculation unit; The third calculation unit is used to take the positive and negative values of the disturbance factor, calculate the product of the rolling friction coefficient and the positive and negative values, and obtain an error value with an upper limit and a lower limit.

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