A cogging torque detection device and method

Abstract

The application provides a cogging torque detection device and method, and relates to the technical field of cogging torque measurement. The device comprises a driving motor, a flywheel and a measured motor which are installed on a positioning platform through a support. The driving motor drives the flywheel and the measured motor to rotate synchronously through a shaft coupling. A rotating speed sensor installed at the tail of the driving motor and a pressure sensor at the end of the measured motor collect data information of the driving motor and the measured motor when rotating at a constant speed. The collected data is processed subsequently, and the cogging torque is calculated. The device and the method applied to the device have the advantages of accurate detection result, wide application range, simple detection process and excellent cost performance.

Description

Technical Field

[0001] This invention relates to the field of tooth cogging torque measurement technology, and in particular to a tooth cogging torque detection device and method. Background Technology

[0002] The cogging effect in permanent magnet motors is caused by their physical structure. Because permanent magnet motors use a cogging structure, teeth guide magnetic lines of force, and slots are used to hold the windings. The different magnetic permeabilities of the teeth and slots cause different magnetic forces on the rotor at different positions. When the magnetic poles align with the teeth, the ferromagnets attract each other, thus hindering the motor's rotation. This phenomenon is called the cogging effect in permanent magnet motors. Furthermore, the cogging effect is independent of whether the stator is energized; it exists even when the motor is not powered. In variable speed drives, when the torque frequency is close to the motor's mechanical frequency, resonance occurs, causing vibration and noise. Therefore, the cogging effect has a serious negative impact on the motor's low-speed performance and high-precision control. Thus, accurate measurement of cogging torque is essential for compensation or reduction of cogging torque during motor control, or for performance evaluation.

[0003] Currently, cogging torque measurement methods are mainly divided into three categories based on their measurement principles: simplified measurement methods, torque sensor measurement methods (i.e., direct measurement methods), and current-voltage measurement methods (i.e., indirect measurement methods). Simplified measurement methods are characterized by their simplicity, ease of operation, and lack of need for excessive mechanical devices, resulting in lower testing costs and less demanding requirements on the testing personnel. However, this measurement scheme is overly simplistic, and the accuracy of the test results can be affected by issues related to tension gauges, electronic scales, and force balance. Furthermore, this method is only suitable for testing motors with large cogging torques.

[0004] In torque sensor measurement, the torque sensor plays an important role as the main measurement tool in both static and dynamic detection methods. However, conventional torque sensors have insufficient response performance, making it difficult to balance range and accuracy. Furthermore, the detection equipment is expensive and the methods are complex.

[0005] The current-voltage measurement method indirectly measures the relationship between motor current, voltage, and cogging torque by collecting and analyzing signals such as motor current and voltage. This method involves fusing and comparing the collected current-voltage and cogging torque signals to obtain information about the motor's cogging torque effect. However, this method neglects current harmonics caused by the control system, leading to inaccurate detection results. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a tooth cogging torque detection device and method that offers accurate detection results, wide applicability, simple detection process, and excellent cost performance.

[0007] To achieve the above objectives, the present invention provides a device for detecting tooth cogging torque, including a motor under test, a flywheel, a drive motor, a positioning platform, a support for the motor under test, a support for the drive motor, a fixing clamp, a pressure sensor, a coupling, a speed acquisition device, a flywheel bearing, and a flywheel bearing housing.

[0008] Specifically, the drive motor is mounted on the drive motor bracket; the fixed clamp holds the motor under test and is connected to the motor under test bracket through two horizontally symmetrical connecting parts, each of which is fixed with a pressure sensor; the drive motor bracket and the motor under test bracket are mounted on the positioning platform; a speed acquisition device is installed at the tail of the drive motor; the flywheel bearing is mounted on the flywheel bearing housing, and the two ends of the flywheel bearing are connected to the drive motor and the motor under test respectively through couplings; the flywheel bearing housing is fixedly connected to the positioning platform.

[0009] Preferably, the toothed torque detection device further includes a sliding guide rail; the sliding guide rail is set on the positioning platform and is parallel to the coupling axis; the motor bracket under test and the drive motor are connected to the sliding guide rail and can be fixed, slid or removed along the coupling axis.

[0010] Furthermore, there are two sliding guides, which are symmetrical about the vertical projection of the coupling axis onto the positioning platform.

[0011] Preferably, the toothed torque detection device further includes a motor controller: the motor controller is connected to the drive motor and is used to control the rotor rotation of the drive motor.

[0012] Preferably, the speed acquisition device in the toothed torque detection device is a photoelectric encoder, and the code disk of the photoelectric encoder is coaxial with the motor under test.

[0013] Furthermore, based on the above-mentioned cogging torque detection device, the present invention also provides a cogging torque detection method, comprising:

[0014] The drive motor drives the flywheel and the tested motor to rotate synchronously and uniformly at a speed n. Simultaneously, pressure sensor readings F1(α) and F2(α) are acquired. The resultant force F of the cogging torque and frictional resistance acting on the housing of the tested motor is then calculated. C (α),

[0015] F C (α)=F1(α)-F2(α) (1)

[0016] In the formula, α is the rotation angle of the rotor of the drive motor relative to the reference point on the stator, obtained by the speed acquisition device;

[0017] Furthermore, the resultant torque T of the cogging torque and resistance torque of the tested motor is calculated. C (α),

[0018] T C(α)=F C (α)L (2)

[0019] In the formula, L is the distance from the center of the contact surface between the fixed clamp and the pressure sensor to the rotation center of the rotor of the motor being tested;

[0020] During the rotation of the tested motor, the driving torque T of the tested motor is:

[0021] T = T e -T c (4)

[0022] T e T represents the electromagnetic torque of the motor under test. c The static resistance torque of the motor under test;

[0023] When the tested motor rotates at a constant speed n, the corresponding steady-state speed motion equation is:

[0024] T e =2πnB+T c (5)

[0025] In the formula, B is the resistance coefficient of the motor being tested;

[0026] Substitute n into equation (5) to obtain the value of B;

[0027] When the tested motor rotates at a constant speed n, the electromagnetic torque T of the tested motor is... e With resistance torque T L equal,

[0028] T L =2πnB+T c (6)

[0029] Furthermore,

[0030] T cog (α)=T C (α)-T L (7)

[0031] In the formula, T cog (α) represents the cogging torque of the motor being tested.

[0032] In this technical solution, apart from the drive circuit and the motor under test, all other components used are conventional electrical or mechanical parts, which are inexpensive and offer excellent cost-effectiveness. The flywheel ensures smoother and more stable rotation speed of the drive motor when driving the flywheel and the rotor of the motor under test, thereby improving the accuracy of the test results. The encoder installed at the tail of the drive motor can collect the rotation data of the drive motor in real time with high precision to ensure the accuracy of the test results. During the testing process, technicians only need to install the motor under test and start the drive motor and photoelectric sensor to obtain basic test data and calculate the test results. As can be seen, the entire testing process is simple and easy to operate. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the assembly of a device according to an embodiment of the present invention.

[0034] Figure 2 This is a front view of a device according to an embodiment of the present invention.

[0035] Figure 3 This is a side view of a device according to an embodiment of the present invention.

[0036] Figure 4 This is a side view of the test motor end device according to an embodiment of the present invention.

[0037] Figure 5 This is a side view of the drive motor end device according to an embodiment of the present invention.

[0038] Figure 6 This is a schematic flowchart of a detection method according to an embodiment of the present invention.

[0039] Figure 7 This is a schematic flowchart of controlling the drive motor according to an embodiment of the present invention.

[0040] Figure 8 This is a graph showing the detection results of one embodiment of the present invention.

[0041] The labels in the diagram represent: photoelectric encoder-1, motor mounting clamp-2, drive motor-3, flywheel-4, flywheel bearing and flywheel bearing housing-5, coupling-6, motor under test-7, pressure sensor-8, positioning platform-9, motor under test bracket-10, motor bracket fixing bolt-11, flywheel bearing housing-12, flywheel bearing housing fixing bolt-13, drive motor bracket-14, and motor mounting clamp fixing bolt-15. Detailed Implementation

[0042] In traditional methods for detecting cogging torque, the simplified measurement method is too simple in mechanical structure, making it difficult to guarantee the accuracy of the test results, and it is only suitable for testing motors with large cogging torque. In the direct measurement method, the response performance of conventional torque sensors is insufficient, and the detection equipment used is expensive and the detection method is complex. The indirect measurement method ignores the current harmonics caused by the control system, which also leads to inaccurate test results.

[0043] It is evident that each detection method has its drawbacks, and these drawbacks vary. To address these technical problems, this invention provides a device and method for detecting tooth cogging torque, specifically including a tooth cogging torque detection device comprising:

[0044] The components under test include the motor, flywheel, drive motor, positioning platform, motor under test bracket, drive motor bracket, fixing clamp, pressure sensor, coupling, speed acquisition device, flywheel bearing, and flywheel bearing housing.

[0045] The drive motor is mounted on the drive motor bracket; the fixed clamp holds the motor under test and is connected to the motor under test bracket through two horizontally symmetrical connecting parts, each of which is fixed with a pressure sensor; the drive motor bracket and the motor under test bracket are mounted on the positioning platform; a speed acquisition device is installed at the tail of the drive motor; the flywheel bearing is mounted on the flywheel bearing seat, and the two ends of the flywheel bearing are connected to the drive motor and the motor under test respectively through couplings; the flywheel bearing seat is fixedly connected to the positioning platform.

[0046] In some embodiments, the connection relationship between the components of the device involved in the present invention can be determined: the drive motor and the motor under test are both clamped by the motor fixing clamp and fixed to their respective motor brackets by the motor fixing clamp fixing bolts, and the motor brackets are fixedly connected to the positioning platform by the motor bracket fixing bolts; the flywheel bearing is fixed in an embedded manner on the flywheel bearing seat, and the flywheel bearing seat is fixed to the positioning platform by the flywheel bearing seat fixing bolts.

[0047] Optionally, the motor under test can also be fixed to the motor under test bracket by welding the housing; there are also multiple options for the connection between the flywheel bearing housing and the positioning platform. For example, when the positioning platform is made of metal, the flywheel bearing housing can also be fixed to the positioning platform by welding or riveting. In fact, except for the motor under test end, which requires two horizontally symmetrically arranged pressure sensors to achieve the measurement function and needs to be connected in a specific way, the connection methods between the other components do not affect the detection results of this invention. Therefore, multiple methods can be selected for connection. In other words, changing the connection method has no substantial impact on this invention.

[0048] Preferably, the toothed torque detection device further includes a sliding guide rail; the sliding guide rail is set on the positioning platform and is parallel to the coupling axis; the motor bracket under test and the drive motor are connected to the sliding guide rail and can be fixed, slid or removed along the coupling axis.

[0049] Furthermore, there are two sliding guides, which are symmetrical about the vertical projection of the coupling axis onto the positioning platform.

[0050] In the above preferred embodiment, the drive motor and the motor under test are interchangeable, and their positions can be adjusted by adjusting the positions of the drive motor bracket and the motor under test bracket on the sliding guide rail to meet the requirements for testing the cogging torque of different motor models. This sliding guide rail not only makes motor installation and removal more convenient and labor-saving, but also serves a positioning function, preventing errors in the results caused by installation position errors. Furthermore, the two parallel guide rails further enhance the stability of the guide rail, thereby ensuring the accuracy of the monitored data.

[0051] Preferably, the toothed torque detection device further includes a motor controller: the motor controller is connected to the drive motor and is used to control the movement of the drive motor.

[0052] In the above preferred embodiment, the DC power supply is connected to the motor controller via wires, and the motor controller is connected to the drive motor via wires. The motor controller changes the pulse width and pulse frequency by switching transistors on and off, thereby changing the average voltage applied to the motor armature and thus changing the motor speed. The motor controller can provide a more stable current to the drive motor, ensuring the accuracy and precision of the detection results.

[0053] Preferably, the encoder in the toothed torque detection device is a speed acquisition device, which is a photoelectric encoder, and the code disk of the photoelectric encoder is coaxial with the motor under test.

[0054] In the above preferred embodiment, a photoelectric encoder is installed at the tail of the drive motor. The code disk of the photoelectric encoder rotates synchronously with the drive motor on the same axis, which can acquire information about the speed of the drive motor and the relative position of the stator and rotor of the drive motor. Since the drive motor drives the measured motor to rotate synchronously, the relative position of the stator and rotor of the measured motor can also be acquired. The main working principle of the photoelectric encoder is photoelectric conversion, which is a sensor that converts the mechanical geometric displacement of the output shaft into pulse or digital quantities through photoelectric conversion. The photoelectric encoder mainly consists of a grating disk and a photoelectric detection device. In the servo system, the grating disk is coaxial with the motor, causing the rotation of the motor to drive the rotation of the grating disk. Then, the photoelectric detection device outputs several pulse signals. The current speed of the motor can be calculated based on the number of pulses per second of this signal. The code disk of the photoelectric encoder outputs three sets of square wave pulses A, B and Z phases. The A and B pulses are 90 degrees out of phase. The rotation direction of the motor can be determined by the change in the state of the dual-channel output optical code, while the Z phase is one pulse per revolution and is used for reference point positioning to determine the relative position of the stator and rotor.

[0055] Optionally, in addition to an optical encoder, the speed acquisition unit in this cogging torque detection device can also be a speed sensor. The speed sensor is a magnetoelectric type. By making a missing tooth on the gear or gear disk connected to the sensor, the position of the rotor in the drive motor can be determined while acquiring the speed.

[0056] Alternatively, the rotation speed acquisition device can also be a Hall effect sensor. The same effect can be achieved by placing magnets evenly distributed around the circumference of the disk to which it is connected for data acquisition, leaving one magnet empty. However, this method has limited accuracy in both rotation speed acquisition and position determination.

[0057] The applicant will describe a method for detecting cogging torque provided by the present invention through an embodiment, as follows:

[0058] The drive motor drives the flywheel and the motor under test to rotate synchronously and uniformly at a speed n. Simultaneously, a data acquisition card collects signals from both the pressure sensor and the photoelectric encoder. The pressure sensor is connected to the pressure signal port of the data acquisition card, and the photoelectric encoder is connected to the speed signal port. Finally, the signals are converted by the processing circuit in the data acquisition card and output to the host computer. During signal acquisition, the pressure and speed signals are acquired simultaneously. Since the photoelectric encoder outputs one Z-phase pulse per revolution, two Z-phase pulses represent the angular position relationship between the stator and rotor of the drive motor in one revolution (360°). Therefore, the curve in the host computer uses the position angle as the horizontal axis and the tension / compression values ​​as the vertical axis.

[0059] Through the above steps, pressure sensor readings F1(α) and F2(α) are obtained, since two pressure sensors are respectively arranged at both ends of the motor under test. Depending on the rotation direction of the drive motor, when one sensor obtains a pressure signal reading, the other obtains a tension signal reading. Therefore, the two readings are equal in magnitude and opposite in direction, that is, F1(α) and F2(α) have simultaneity, same value, and opposite direction.

[0060] The resultant force F of the cogging torque and frictional resistance acting on the casing of the tested motor is obtained from F1(α) and F2(α). C (α),

[0061] F C (α)=F1(α)-F2(α)(1)

[0062] In the formula, α is the rotation angle of the rotor in the drive motor relative to the reference point on the stator, obtained by the photoelectric encoder;

[0063] Furthermore, the resultant torque T of the cogging torque and resistance torque of the tested motor is calculated using the torque calculation formula T = FL. C (α),

[0064] T C (α)=F C (α)L(2)

[0065] In the formula, L is the distance from the center of the contact surface between the fixed clamp and the pressure sensor to the rotation center of the rotor of the motor being tested;

[0066] Drive the flywheel and the tested motor to rotate synchronously and uniformly at a speed m (30-50 rpm). Repeat the above steps to obtain the pressure sensor readings F3(α) and F4(α), and calculate the resultant force F. 34 (α), further calculate the resultant torque T of the cogging torque and resistance torque of the tested motor. 34 (α).

[0067] During the rotation of the tested motor, the driving torque T of the tested motor can be expressed by the dynamic balance equation of the tested motor as follows:

[0068]

[0069] Where B is the resistance coefficient of the motor under test, ω is the angular velocity of the motor under test, J is the moment of inertia of the rotor and flywheel load of the motor under test, dω / dt is the angular acceleration of the motor under test, and T is the driving torque of the motor under test.

[0070] T = T e -T c (4)

[0071] In the formula, T eT represents the electromagnetic torque of the motor under test. c The static resistance torque of the motor under test;

[0072] Since the relationship between angular velocity and rotational speed is ω=2πn, when the tested motor rotates at a constant speed n, the corresponding stable speed motion equation is:

[0073] T e =2πnB+T c (5)

[0074] In the formula, B is the resistance coefficient of the motor being tested;

[0075] Substitute n into equation (5) to obtain the value of B;

[0076] When the tested motor rotates at a constant speed, the electromagnetic torque T of the tested motor is... e With resistance torque T L They are equal when the rotational speed is n.

[0077] T L =2πnB+T c (6)

[0078] Furthermore,

[0079] T cog (α)=T C (α)-T L (7)

[0080] In the formula, T cog (α) represents the cogging torque of the motor being tested.

[0081] Similarly, when the rotation angle of the rotor relative to the reference point on the stator in the motor is still α, substituting m into equation (5) can yield the resistance coefficient B1 and resistance torque T of the motor under test at a speed of m. L34 ,

[0082] T L34 =2πnB1+T 34 (8)

[0083] Furthermore, the cogging torque T of the tested motor at a rotational speed of m is calculated. cog34 (α),

[0084] T cog34 (α)=T 34 (α)-T L34 (9)

[0085] Using the above methods, the cogging torque of the motor under test can be determined by different rotational speeds.

[0086] In the above process, the data collected by the photoelectric encoder and pressure sensor are processed by the signal acquisition system, and the corresponding relationship between different rotation angles of the rotor relative to the reference point on the stator and the measured resultant torque is output as a curve, as shown in the figure. Figure 8 As shown, F5 and F6 correspond to the resultant torques at rotational speeds N1 and N2, respectively.

[0087] As can be seen, compared with traditional tooth cogging detection methods, the tooth cogging torque detection device and method provided by this invention have the advantages of accurate detection results, wide applicability, simple detection process, and excellent cost performance. Among various preferred solutions, the presence of the sliding guide rail makes the installation and unloading of the device simpler and more convenient, and the positioning more accurate; the motor controller can provide a stable power supply to the drive motor, which can ensure the accuracy and precision of the detection results; the photoelectric encoder has a higher sampling frequency than other speed samplers, which can ensure the accuracy of the detection results and is more suitable for this invention.

[0088] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting cogging torque, characterized in that, The method includes: The drive motor drives the flywheel and the motor under test to rotate synchronously and uniformly at a speed n, while simultaneously acquiring the pressure sensor readings. and The resultant force of the cogging torque and frictional resistance acting on the housing of the motor under test is obtained. , （1）； In the formula, The rotation angle of the rotor in the drive motor relative to a reference point on the stator is obtained by the speed acquisition device. Furthermore, the resultant torque of the cogging torque and resistance torque of the tested motor is calculated. , （2）； In the formula, The distance from the center of the contact surface between the fixing clamp and the pressure sensor to the rotation center of the rotor of the motor being tested; During the rotation of the motor under test, the driving torque of the motor under test for, （4）； The electromagnetic torque of the motor under test; The static resistance torque of the motor under test; When the tested motor rotates at a constant speed n, the corresponding steady-state speed motion equation is: （5）； In the formula, The resistance coefficient of the motor under test; Substituting n into equation (5), we obtain The value; When the motor under test rotates at a constant speed n, the electromagnetic torque of the motor under test... With resistance torque equal, （6）； Furthermore, （7）； In the formula, The value is the cogging torque of the motor being tested.

2. A cogging torque detection device suitable for the cogging torque detection method as described in claim 1, characterized in that, include: The drive motor is mounted on the drive motor bracket; The fixed clamp holds the motor under test and is connected to the motor under test bracket through two horizontally symmetrical connecting parts, each of which is fixed with a pressure sensor; the drive motor bracket and the motor under test bracket are installed on the positioning platform; a speed acquisition device is installed at the tail of the drive motor; the flywheel bearing is installed on the flywheel bearing seat, and the two ends of the flywheel bearing are connected to the drive motor and the motor under test respectively through couplings; the flywheel bearing seat is fixedly connected to the positioning platform.

3. The detection device according to claim 2, characterized in that, It also includes sliding rails; The sliding guide rail is set on the positioning platform and is parallel to the axis of the coupling. The test motor bracket and drive motor bracket are connected to the sliding guide rail and can be fixed, slidable, or removed along the axis of the coupling.

4. The detection device according to claim 3, characterized in that, There are two sliding guide rails, and they are symmetrical about the vertical projection of the coupling axis onto the positioning platform.

5. The detection device according to claim 2, characterized in that, It also includes a motor controller; the motor controller is connected to the drive motor and is used to control the rotation of the drive motor's rotor.

6. The detection device according to claim 2, characterized in that, The speed acquisition device is a photoelectric encoder, and the code disk of the photoelectric encoder is coaxial with the motor under test.

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