A micro-torque testing system and method for motor

Abstract

The present invention discloses a micro-torque testing system and method for electric motors, belonging to the field of testing technology. The micro-torque testing system for electric motors includes a test bench, a signal conditioning circuit, and a torque output control circuit, both of which are purely analog circuits. This system is used to detect micro-torques ranging from 0mN·m to 10mN·m and can display the dynamic torque value of the motor being tested in real time.

Description

Technical Field

[0001] The present invention belongs to the technical field of testing, and in particular relates to a micro-torque testing system and method for a motor. Background Art

[0002] Currently, commonly used motor torque testers typically use a torque sensor. The motor shaft under test is fixedly connected to the torque sensor. The motor under test pulls the torque sensor to detect torque. The torque sensor converts the torque signal into a current signal, which is then collected on a circuit board. The data is then processed and displayed within the CPU using A / D conversion. This torque measurement method has certain limitations in terms of resolution and accuracy. First, the motor shaft under test and the torque sensor's test head must be fixedly connected via a coupling. Consequently, the motor torque under test must first overcome the frictional resistance of the bearings. As a result, the minimum measurable torque of the system depends on the magnitude of the bearing frictional resistance, making it unsuitable for measuring microtorques. Existing torque tester systems generally have a maximum resolution of 1 mN·m, making them unable to measure microtorques less than 1 mN·m. Second, existing torque detection technology uses digital circuits to collect signals into the CPU and then convert them into torque signals. Therefore, data processing and command execution within the CPU require a certain execution time, resulting in a delay in the sampled torque signal, making it unsuitable for collecting microtorques under dynamic conditions. Summary of the Invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, the present invention provides a micro-torque testing system and method for a motor, which is used to detect micro-torques of 0mN·m to 10mN·m and can display the dynamic torque value of the tested motor in real time.

[0004] The technical solution of the present invention is:

[0005] A micro-torque test system for a motor is used to measure the micro-torque of a motor in the torque range of 0mN·m to 10mN·m. The system includes a test bench, a signal conditioning circuit, and a torque output control circuit; wherein the signal conditioning circuit and the torque output control circuit are both purely analog circuits;

[0006] The test bench includes a test fixture, an air bearing, an angle sensor, and a torquer. The motor under test is fixed to the test fixture. The torque generated by the motor under test drives the air bearing to rotate. The angle sensor connected to the air bearing senses the bearing rotation angle and converts the angle information into an electrical signal for output.

[0007] The signal conditioning circuit is used to process the electrical signal output by the angle sensor, calculate the current torque value of the measured motor, and output a binary width-modulated pulse signal;

[0008] The torque output control circuit receives the binary width modulated pulse signal output by the signal conditioning circuit and generates a current signal to control the torquer;

[0009] The torquer receives the current signal from the torque output control circuit and generates a force equal to and opposite to the current torque value of the motor under test, pulling the test fixture connected to the torquer back to zero position.

[0010] Preferably, the angle sensor adopts a multi-pole rotary transformer, which can sense the change of micro torque and has a minimum resolution of at least 0.005 mN·m.

[0011] Preferably, the signal conditioning circuit includes a signal pre-conditioning circuit, a phase-sensitive demodulation circuit, a low-pass filter circuit, a correction network and a pulse width modulation circuit connected in series, and the angle information is transmitted in the above circuit through the voltage amplitude; wherein,

[0012] The signal pre-conditioning circuit receives the electrical signal output by the angle sensor, performs signal amplification and filtering, and then outputs it to the phase-sensitive demodulation circuit;

[0013] After the phase-sensitive demodulation circuit performs signal amplification and phase-shift demodulation, the output demodulated electrical signal enters the low-pass filter circuit;

[0014] The low-pass filter circuit filters the electrical signal and outputs a DC signal that removes high-frequency interference signals. The amplitude of the DC signal is multiplied by the proportional coefficient to obtain the actual torque of the motor under test. The proportional coefficient is obtained through calibration.

[0015] The correction network receives the DC signal, performs correction, and outputs the corrected signal;

[0016] The pulse width modulation circuit receives the electrical signal output by the correction network and outputs a binary width modulated pulse signal.

[0017] Preferably, the signal amplification operation in the signal pre-conditioning circuit adopts an AD521 precision instrument amplifier to amplify the electrical signal output by the test bench angle sensor by 0.1 to 1000 times as needed.

[0018] Preferably, the phase-shift operation of the phase-sensitive demodulation circuit adopts a wide-range phase-shift circuit of an analog operational amplifier to achieve wide-range control of 0° to 180°.

[0019] Preferably, the cut-off frequency of the low-pass filter circuit is more than 10 octaves lower than the bandwidth of the test system.

[0020] Preferably, the pulse width modulation circuit is composed of two cascaded parts. The front stage is a sawtooth wave generating circuit built by an integrated operational amplifier to generate a sawtooth wave signal; the rear stage is a voltage comparator composed of an integrated operational amplifier, which compares the generated sawtooth wave signal with the signal output by the correction network to obtain a binary width modulated pulse signal, which is output to the torque output control circuit.

[0021] Preferably, the torque output control circuit includes a drive signal amplification circuit and a torque adding circuit connected in series; wherein, the drive signal amplification circuit receives a binary width modulated pulse signal, amplifies the signal, and increases the driving capability; the torque adding circuit is composed of an analog switching circuit and a transistor driving circuit, the output signal of the drive signal amplification circuit controls the on and off of the analog switching circuit, the output of the template switching circuit controls the transistor driving circuit, and the transistor driving circuit outputs a current signal to control the torquer.

[0022] Preferably, the test bench also includes a gear selection circuit, which divides the measurable torque range into several gears to achieve accurate measurement of multiple torque levels; when different gears are selected, the gear selection circuit performs different signal amplification gains and current size controls on the phase-sensitive demodulation circuit and the drive signal amplification circuit.

[0023] A method for continuous micro-torque testing of a motor, comprising:

[0024] 1) Fix the motor to be tested on the test fixture, connect the air source to make the air bearing work stably; start the motor and repeat the following steps continuously:

[0025] 2) The angle sensor senses the current rotation angle of the air bearing and converts the angle information into an electrical signal output;

[0026] 3) After amplifying the electrical signal, perform bandpass filtering and output the electrical signal to be demodulated;

[0027] 4) After demodulating the electrical signal to be demodulated, low-pass filtering is performed to output a DC signal, and the current torque value is calculated;

[0028] 5) After correcting and pulse-width modulating the DC signal, a binary width-modulated pulse signal is output;

[0029] 6) After amplifying the binary width modulated pulse signal, the analog switch is controlled to be on and off and the transistor is turned on, generating a current signal acting on the torquer;

[0030] 7) The torquer outputs torque to return the test fixture to zero.

[0031] The advantages of the present invention compared with the prior art are:

[0032] 1) The micro-torque test system for motors proposed in the present invention adopts a pure analog circuit. The entire torque sampling and processing process only requires the time for electrical signal transmission, and there is no software program processing delay, thus ensuring the real-time performance of torque detection.

[0033] 2) The micro-torque test system for motors proposed in the present invention is a closed-loop system. By feeding back the value of the measured torque to the torque meter, the torque meter outputs the corresponding torque to return the test fixture to zero in real time, thereby achieving continuity in torque detection and accurately and quickly obtaining the relationship curve between the torque and time of the measured motor.

[0034] 3) The proposed micro-torque test system for electric motors uses precision air bearings, which have much less friction torque than ordinary bearings. It also employs a multi-pole rotary transformer to measure minute torques. The system achieves a minimum resolution of 0.005 mN·m. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural block diagram of a micro-torque testing system for a motor according to the present invention. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, a micro-torque test system for a motor includes a test bench, a signal conditioning circuit, and a torque output control circuit. The motor generates torque, which drives the test bench's air bearing. An angle sensor connected to the air bearing senses the bearing's rotation angle and converts this angle information into an electrical signal that is fed into the signal conditioning circuit and torque output control circuit. This allows the angle sensor signal to be resolved and the test fixture on the test bench to return to zero.

[0038] The test bench serves as the system's foundational platform, used to measure motor microtorques in the torque range of 0mN·m to 10mN·m, and to generate torque to return the test fixture to zero. The test bench includes a test fixture, an air bearing, an angle sensor, a torque meter, and a gear selection circuit. The motor under test is fixed to the test fixture. The air bearing is the transmission component of the microtorque tester. The angle sensor senses the rotation angle of the air bearing and outputs a sinusoidal electrical signal. This angle information is converted into a voltage amplitude for loading. To improve resolution, the angle sensor uses a multi-pole resolver with a 2" precision. The gear selection circuit divides the microtorque tester's measurable torque range into five gears. Each gear represents the maximum measurable torque. The five gear values ​​can be configured based on the actual measurement range, and different gears correspond to different signal amplification gains and torque currents in the control circuit. Based on the estimated maximum torque value of the motor under test, the corresponding gear is selected. The corresponding analog switch automatically closes, connecting the corresponding series resistor to the drive signal amplifier circuit. Changing the selected gear changes the series resistor connected to the drive signal amplifier circuit, thereby varying the drive current. This method enables precise measurement of various torque levels, with a measurement accuracy of 0.5% of the selected gear value.

[0039] The signal conditioning circuit includes a pre-conditioning circuit, a phase-sensitive demodulation circuit, a low-pass filtering circuit, a correction network, and a pulse width modulation circuit, and is used to process the output signal of the angle sensor.

[0040] The signal preconditioning circuit includes a signal preamplifier circuit and a bandpass filter circuit. The electrical signal output by the angle sensor is input into the signal preamplifier circuit. Because the measured torque is microtorque, the angle sensor output voltage is in the millivolt range. To address this, the signal preamplifier circuit uses the AD521 precision instrumentation amplifier. The gain can be selected between 0.1 and 1000 as required. It features noise as low as 0.5μVp-p, drift as low as 2μV / °C, and a common-mode rejection ratio as high as 110dB, ensuring accurate and stable signal processing. After amplification by the signal preamplifier circuit, the electrical signal is output to the bandpass filter circuit for filtering.

[0041] The center frequency of the bandpass filter circuit is designed to be the fundamental frequency of the angle sensor's output signal, suppressing interference signals in other frequency bands and improving the signal-to-noise ratio. After filtering by the bandpass filter circuit, interference signals of other frequencies are filtered out, retaining only the center frequency signal. This processed signal is then output to the phase-sensitive demodulation circuit for demodulation.

[0042] The phase-sensitive demodulation circuit includes a signal amplification circuit, a phase shift circuit, and a demodulation circuit.

[0043] The signal amplifier circuit precisely amplifies the signal output by the bandpass filter circuit. The amplification factor is determined by the selected torque level. The smaller the torque level, the greater the corresponding signal amplification factor. The purpose is to ensure that the amplitude of the amplified signal is basically consistent. The signal after the signal amplifier circuit is input into the demodulation circuit for demodulation.

[0044] The phase-shift circuit described above is a wide-range phase-shift circuit based on an analog operational amplifier, capable of a wide range of control from 0° to 180°. During initial use, the potentiometer is adjusted to achieve a zero phase difference between the phase shifter and the demodulated signal. The signal output by the phase-shift circuit is also input into the demodulation circuit as a reference signal.

[0045] The demodulation circuit uses the high-precision AD630 balanced modulator, which features a 2MHz bandwidth, a slew rate of up to 45V / µs, an offset voltage as low as 100µV, and programmable gain. It can recover signals from 100dB of noise. The output signal of the signal amplification circuit and a reference signal are input into the demodulation circuit, resulting in a demodulated DC signal.

[0046] The demodulated DC signal enters the low-pass filter circuit, which further filters out high-frequency interference and improves the signal-to-noise ratio. To avoid the effects of phase lag, its cutoff frequency is at least 10 octaves below the test system bandwidth. The amplitude of the demodulated angle signal multiplied by the corresponding proportionality factor is the actual torque of the motor under test. The proportionality factor is obtained through torque calibration.

[0047] To achieve dynamic torque measurement, this system adopts closed-loop control. The test fixture of the test bench needs to be kept at zero position at all times. Therefore, the control circuit needs to quickly output a force equal to the measured torque and in the opposite direction to pull the test fixture back to zero position to ensure the continuity and real-time performance of the torque test results.

[0048] Therefore, the demodulated and filtered DC signal needs to be input into a correction network to adjust the bandwidth and improve the response. This correction network consists of two integrated operational amplifiers connected in series: a proportional control circuit in the front stage and an integral lead control circuit in the back stage. It features low input bias current and high open-loop gain.

[0049] The corrected DC signal is input into the pulse-width modulation circuit, which consists of two parts. The front-end uses a high-precision integrated operational amplifier to create a sawtooth wave generator circuit. This circuit utilizes an integrated precision shunt regulator connected in parallel with a potentiometer. The amplitude of the sawtooth wave is adjusted by adjusting the resistance of the potentiometer connected to the circuit. The back-end, a voltage comparator composed of an integrated operational amplifier, compares the generated sawtooth wave with the corrected signal to generate a binary pulse width modulated signal. The angle information is transmitted through the duty cycle of the binary pulse width modulated signal.

[0050] The torque output control circuit includes a drive signal amplifying circuit and a torque adding circuit, which are used to generate a torquer control current, control the torquer output torque of the test bench, and return the test fixture to zero.

[0051] The drive signal amplification circuit consists of two parts. First, an operational amplifier amplifies the output signal from the gear selection circuit, which then passes through a first-stage Darlington transistor to increase the drive capability. The binary width-modulated pulse signal is amplified by the drive signal amplifier circuit and then used to control the analog switch of the torque-adding circuit.

[0052] The torque-adding circuit consists of an analog switch circuit and a transistor drive circuit. The binary width-modulated pulse signal after amplification is used as the control end of the analog switch. The on and off of the analog switch is controlled by the duty cycle. After the analog switch is closed, the corresponding transistor is turned on, and the torquer of the test bench is loaded through the output end of the transistor. The torquer outputs torque to return the test fixture to zero position.

[0053] The test method of micro torque tester for motor includes:

[0054] 1) Fix the motor to be tested on the test fixture, select the gear, and connect the air source to make the air bearing work stably; start the motor and repeat the following steps continuously:

[0055] 2) The torque generated by the motor drives the air bearing to deflect a certain angle. The angle sensor senses the rotation angle of the air bearing and converts the angle signal into an electrical signal for output;

[0056] 3) After amplifying the angle electrical signal, perform bandpass filtering and output the electrical signal to be demodulated;

[0057] 4) After demodulating the electrical signal to be demodulated, perform low-pass filtering processing, output a DC signal, and calculate the current measured torque value;

[0058] 5) After correcting and pulse-width modulating the DC signal, a binary width-modulated pulse signal is output;

[0059] 6) After amplifying the binary width modulated pulse signal, the analog switch is controlled to be on and off and the transistor is turned on. The transistor outputs a current signal that acts on the torque converter.

[0060] 7) The torquer outputs a force equal in magnitude and opposite in direction to the measured torque, returning the test fixture to zero.

[0061] The test system proposed by the present invention can automatically output the current torque value of the tested motor every 40 to 60 μs, thereby achieving continuity and real-time testing.

[0062] The above description is only the best specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

[0063] The contents not described in detail in the specification of the present invention belong to the common knowledge of professionals in this field.

Claims

1. A micro-torque test system for a motor, used to measure the micro-torque of a motor in the torque range of 0mN·m to 10mN·m, characterized in that: The system includes a test bench, a signal conditioning circuit, and a torque output control circuit; wherein the signal conditioning circuit and the torque output control circuit are both pure analog circuits; The test bench includes a test fixture, an air bearing, an angle sensor, and a torquer. The motor under test is fixed to the test fixture. The torque generated by the motor under test drives the air bearing to rotate. The angle sensor connected to the air bearing senses the bearing rotation angle and converts the angle information into an electrical signal for output. The signal conditioning circuit is used to process the electrical signal output by the angle sensor, calculate the current torque value of the measured motor, and output a binary width-modulated pulse signal; The torque output control circuit receives the binary width modulated pulse signal output by the signal conditioning circuit and generates a current signal to control the torquer; The torquer receives the current signal from the torque output control circuit and generates a force equal to and opposite to the current torque value of the motor under test, pulling the test fixture connected to the torquer back to zero position.

2. The micro-torque testing system according to claim 1, characterized in that: The angle sensor adopts a multi-pole rotary transformer, which can sense the change of micro torque, and the minimum resolution reaches at least 0.005mN·m.

3. The micro-torque testing system according to claim 1, wherein: The signal conditioning circuit includes a signal pre-conditioning circuit, a phase-sensitive demodulation circuit, a low-pass filter circuit, a correction network and a pulse width modulation circuit connected in series; wherein, The signal pre-conditioning circuit receives the electrical signal output by the angle sensor, performs signal amplification and filtering, and then outputs it to the phase-sensitive demodulation circuit; After the phase-sensitive demodulation circuit performs signal amplification and phase-shift demodulation, the output demodulated DC signal enters the low-pass filter circuit; The low-pass filter circuit filters the electrical signal and outputs a DC signal that removes high-frequency interference signals. The amplitude of the DC signal is multiplied by the proportional coefficient to obtain the actual torque of the motor under test. The proportional coefficient is obtained through calibration. The correction network receives the DC signal, performs correction, and outputs the corrected control signal; The pulse width modulation circuit receives the control signal output by the correction network and outputs a binary width modulated pulse signal.

4. The micro-torque testing system according to claim 3, characterized in that: The signal amplification operation in the signal pre-conditioning circuit adopts AD521 precision instrument amplifier to amplify the electrical signal output by the test bench angle sensor by 0.1 to 1000 times as needed.

5. The micro-torque testing system according to claim 3, wherein: The phase-shift operation of the phase-sensitive demodulation circuit adopts a wide-range phase-shift circuit of an analog operational amplifier to achieve wide-range regulation of 0° to 180°.

6. The micro-torque testing system according to claim 3, characterized in that: The cut-off frequency of the low-pass filter circuit is more than 10 times lower than the bandwidth of the test system.

7. The micro-torque testing system according to claim 3, wherein: The pulse width modulation circuit is composed of two cascaded parts. The front stage uses an integrated operational amplifier to build a sawtooth wave generating circuit to generate a sawtooth wave signal; the back stage is a voltage comparator composed of an integrated operational amplifier. By comparing the generated sawtooth wave signal with the signal output by the correction network, a binary width modulated pulse signal is obtained and output to the torque output control circuit.

8. The micro-torque testing system according to claim 1 or 3, characterized in that: The torque output control circuit includes a drive signal amplifying circuit and a torque adding circuit connected in series; wherein, The driving signal amplifying circuit receives the binary width modulated pulse signal, amplifies the signal, and increases the driving capability; The torque adding circuit is composed of an analog switch circuit and a transistor drive circuit. The output signal of the drive signal amplifier circuit controls the on and off of the analog switch circuit. The output of the template switch circuit controls the transistor drive circuit. The transistor drive circuit outputs a current signal to control the torquer.

9. The micro-torque testing system according to claim 8, characterized in that: The test bench also includes a gear selection circuit that divides the measurable torque range into several gears to achieve accurate measurement of multiple torque levels; when different gears are selected, the gear selection circuit performs different signal amplification gains on the phase-sensitive demodulation circuit and the drive signal amplification circuit.

10. A method for continuous micro-torque testing of a motor, characterized in that: include: 1) Fix the motor under test on the test fixture, connect the air source, and make the air bearing work stably; Start the motor and repeat the following steps continuously: 2) The angle sensor senses the current rotation angle of the air bearing and converts the angle information into an electrical signal output; 3) After amplifying the electrical signal, perform bandpass filtering and output the electrical signal to be demodulated with the interference signal removed; 4) After demodulating the electrical signal to be demodulated, low-pass filtering is performed to output a DC signal, and the current torque value is calculated; 5) After correcting and pulse-width modulating the DC signal, a binary width-modulated pulse signal is output; 6) After amplifying the binary width modulated pulse signal, the analog switch is controlled to be on and off and the transistor is turned on, generating a current signal acting on the torquer; 7) The torquer outputs torque to return the test fixture to zero.

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