Resonance detection and processing method for stepping motor system

Abstract

The invention belongs to the technical field of motor control, and more specifically relates to a stepping motor system resonance detection and processing method. The stepping motor system comprises a stepping motor connected with a stepping motor controller, a first gyroscope, a second gyroscope and a bearing, the first gyroscope is fixedly arranged on the portion, on one side of a non-output shaft of the stepping motor, of a body shell, and a non-rotating platform is built on an output shaft, connected with a load, of the stepping motor system. The platform is connected with an output shaft of the stepping motor through a bearing, the platform is connected with the fixing body through a universal joint, a second gyroscope is installed on the platform, and the first gyroscope and the second gyroscope transmit data to a stepping motor controller through wireless transmission; whether vibration detected by the first gyroscope and vibration detected by the second gyroscope are consistent or not is judged, if not, the stepping motor system does not resonate, otherwise, the stepping motor system resonates, and the PWM frequency and the torque pulse frequency of the stepping motor are shifted out of the inherent frequency range of the stepping motor.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and more specifically, relates to a resonance detection and processing method for a stepping motor system. Background Art

[0002] Stepper motor systems offer precise speed and angle control, along with various levels of torque, and are widely used in measurement and control, engineering machinery, CNC equipment, robotics, and other fields. However, the presence of inherent frequency vibrations, electromagnetic torque pulses, PWM high-frequency pulses, and load swing-induced vibrations in stepper motor systems, particularly when these frequencies overlap, can lead to significant resonance in stepper motor systems.

[0003] Traditional methods for determining resonance in stepper motor systems typically rely on observation (visual and auditory), system status alarms, and fault alarms. These judgments rely on human experience and observation, lacking accuracy, scientificity, and predictive power. By the time resonance is detected, the system is often out of control, significantly impacting engineering applications and operational safety. Even in some applications where vibration detection is performed using sensors, these sensors are often single-sensor, measuring only the vibration signal at the stepper motor, lacking comprehensive consideration of vibrations caused by the load and environment. Distributed measurement can fully measure and compare vibration signals at different points in the system, providing greater accuracy for determining resonance in rigidly connected systems. Traditional approaches to addressing vibration and resonance in stepper motor systems generally involve two methods: The first involves increasing the subdivision of the PWM pulses output by the stepper motor controller to slow the current variation in the stepper motor rotor. This approach, by reducing the change in input current per unit time, reduces the torque jump caused by the current change, thereby minimizing vibration and resonance in the stepper motor system. Another approach to addressing vibration and resonance in stepper motor systems involves increasing damping, increasing torque loads, or adding a reduction mechanism. Increasing shock absorption damping is a physical shock absorption method, such as adding rubber gaskets to the system, implementing a rigid connection between the output shaft and the load, etc., which physically transmits the vibration of the stepper motor system to the outside of the system, thereby reducing the vibration and resonance of the system. Therefore, this is a measure that cannot fundamentally reduce or eliminate the vibration and resonance of the system.

[0004] To accurately detect stepper motor system resonance and eliminate vibration interference caused by load and environment, distributed measurement and judgment is undoubtedly a more reasonable approach. Another innovation is the construction of a stepper motor resonance measurement platform using advanced sensors, appropriate mechanical components, and data transmission technology. While accurately determining stepper motor system resonance, frequency shifting and subdivision techniques are employed to address resonance issues. Summary of the Invention

[0005] To this end, a method for detecting and addressing resonance in stepper motor systems is needed. By building a distributed vibration detection platform for stepper motor systems, the problem of resonance detection in stepper motor systems can be solved. Distributed detection, comparison, and judgment can be used to improve the accuracy of resonance detection and identification. By adjusting (raising) the PWM frequency to between the stepper motor's natural frequency and its multiple and increasing the number of subdivisions in the stepper motor, the resonance problem caused by frequency overlap can be resolved.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for detecting and processing resonance of a stepper motor system, characterized in that the stepper motor system includes a stepper motor connected to a stepper motor controller, a first gyroscope, a second gyroscope, and a bearing, the first gyroscope being fixedly arranged on a main body housing on a non-output shaft side of the stepper motor, a non-rotating platform being constructed on an output shaft of the stepper motor system connected to a load, the non-rotating platform being connected to the output shaft of the stepper motor by a bearing, the non-rotating platform being connected to a fixed body by a universal joint, the second gyroscope being mounted on the non-rotating platform, the first gyroscope and the second gyroscope transmitting data to the stepper motor controller via wireless transmission; determining whether vibrations detected by the first gyroscope and the second gyroscope are consistent; if not, the stepper motor system does not resonate; otherwise, the stepper motor system resonates, and the PWM frequency and the stepper motor torque pulse frequency are moved out of the stepper motor's natural frequency range.

[0008] The present technical solution is further optimized. The method for determining whether the vibrations of the first gyroscope and the second gyroscope are consistent is as follows: after the stepping motor controller receives the vibration time series value, the frequency value is obtained by discrete Fourier transform, as shown in formula (1). By finding the maximum value of the frequency point, the significant vibration frequency at the first gyroscope and the second gyroscope is obtained, where DFT[] is the discrete Fourier transform operator, x(i) is the i-th value of the vibration signal time series, and n is the length of the time series.

[0009] f(k)=DFT[x(i)],k=0,1,...n; i=0,1,...n (1)

[0010] f z =max{f(k)},k=0,1,...n (2)

[0011] Assume that the significant vibration frequency of the first gyroscope is f z_1 , the significant vibration frequency of the second gyroscope is f z_2 , then the conditions for judging the resonance of the stepper motor system are:

[0012] |f z_1 -f z_2 |<Δf z

[0013] Set threshold Δf z , when |f z_1 -f z_2 |<Δf z When , it is considered that the stepper motor system resonates.

[0014] The technical solution is further optimized by moving the PWM frequency and the stepper motor torque pulse frequency out of the natural frequency range of the stepper motor as follows:

[0015] a) Adjust (increase) the PWM frequency to between the natural frequency of the stepper motor and its multiple. Assume that the PWM frequency is f P , the natural frequency of the stepper motor system is f G , then the natural frequency and its multiples are:

[0016] k·f G , k=1,2,... (4)

[0017] The adjusted PWM frequency is

[0018] k1·f G <f P <k2·f G , k2>k1≥1 (5)

[0019] b) Increase the subdivision number of the stepper motor. Increasing the subdivision number of the stepper motor can reduce the current pulse of the internal winding of the stepper motor, thereby reducing the torque pulse and the vibration of the stepper motor. Assume that the original subdivision number set by the stepper motor controller is M O , the new number of subdivisions is

[0020] M N =2 k ·M O , k=1,2,... (6).

[0021] This technical solution is further optimized in that the first gyroscope and the second gyroscope are three-axis gyroscopes.

[0022] This technical solution is further optimized, and the wireless transmission method is Bluetooth or WIFI.

[0023] Different from the existing technology, the above technical solution has the following beneficial effects:

[0024] 1. Build a vibration detection and processing system for the stepper motor system using dual-channel gyroscopes, wireless transmission, universal joints, and bearings. Perform dynamic resonance detection on the stepper motor system through distributed gyroscopes, improving detection accuracy. Reduce system structural complexity and wiring difficulty through wireless transmission, improving data transmission quality. Build a vibration measurement platform for the stepper motor output shaft using universal joints and bearings to practice the separation of shaft torque output and vibration measurement.

[0025] 2. The vibration signals of the motor side and output shaft (near the load) of the stepper motor system are measured by dual gyroscopes and compared and judged, which improves the accuracy of resonance judgment and provides an accurate basis for resonance processing.

[0026] 3. By adjusting (increasing) the PWM frequency to between the natural frequency of the stepper motor and its multiples and increasing the number of subdivisions of the stepper motor, the risk of resonance caused by spectrum overlap, current and torque shock can be effectively avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the stepper motor system resonance detection and processing system;

[0028] Figure 2 A schematic cross-sectional view of the platform.

[0029] 1. Stepper motor controller, 2. Stepper motor, 3. First gyroscope, 4. Second gyroscope, 5. Bearing, 6. Universal joint, 7. Fixed body, 8. Load. DETAILED DESCRIPTION

[0030] In order to explain the technical content, structural features, achieved objectives and effects of the technical solution in detail, the following is a detailed description in conjunction with specific embodiments and accompanying drawings.

[0031] See also Figure 1 The figure shows a schematic diagram of a resonance detection and processing system for a stepper motor system. In this embodiment, a three-axis gyroscope, namely a first gyroscope 3, is installed on the main body housing of the stepper motor 2 on the side (tail) of the non-output shaft. At the same time, a non-rotating platform is built on the output shaft (near the load) of the stepper motor system. The platform is connected to the output shaft by a bearing 5, and the platform is connected to a fixed body 7 (such as a wall) by a universal joint 6. This stabilizes the platform without suppressing the transmission of platform vibration. Another three-axis gyroscope, namely a second gyroscope 4, is installed on this platform, and the data transmission between the two gyroscopes and the stepper motor controller 1 is wireless, such as WiFi. Since the platform is connected to the output shaft by a bearing 5, it can be regarded as a rigid connection. The vibration on the output shaft will be transmitted to the platform and detected by the gyroscope.

[0032] See Figure 2The platform is fixedly connected to the outer ring surface of the bearing 5, and the bottom of the bearing 5 is connected to the wall / ground through a universal joint 6 and a rotating shaft (the one close to the wall), provided by the wall.

[0033] The main functions of this universal joint + shaft structure are:

[0034] a) Prevent the outer ring of the bearing from rotating with the output shaft of the stepper motor.

[0035] b) Provide a relatively stable gyro mounting platform.

[0036] c) When the stepper motor output shaft vibrates or rotates laterally (non-axially), the universal joint + shaft structure can ensure that the vibration of the stepper motor output shaft can be normally transmitted to the gyro platform.

[0037] 2. Resonance detection

[0038] To determine whether the stepper motor system is resonant, it is necessary to determine whether the vibrations detected by the two gyroscopes are consistent. Since the platform is connected to the rotating shaft through the bearing 5, the second gyroscope 4 on the platform can detect the vibration generated by the rotating shaft. The first gyroscope 3 installed at the tail of the stepper motor can detect the vibration of the stepper motor 2 body, and is not easily affected by the output load end. When the stepper motor system resonates, the vibration signal is relatively strong and can be transmitted to the end near the load 8 through the output shaft. Only when the resonant frequencies detected by the two gyroscopes are consistent can the disturbance introduced by the operation of the load 8 be eliminated, thereby confirming the occurrence of resonance in the stepper motor system. The two gyroscopes transmit the angular velocity (vibration) signal to the stepper motor controller 1 via WiFi. After receiving the vibration time series value, the stepper motor controller 1 obtains the value of each frequency point through discrete Fourier transform, as shown in formula (1). By finding the maximum value of the frequency point, the significant vibration frequency at the gyroscope is obtained, where DFT[] is the discrete Fourier transform operator, x(i) is the i-th value of the vibration signal time series, and n is the length of the time series.

[0039] f(k)=DFT[x(i)], k=0, 1,...n; i=0, 1,...n (1)

[0040] f z =max{f(k)},k=0,1,...n (2)

[0041] Assume that the significant vibration frequency of the first gyroscope 3 is f z_1 , the significant vibration frequency of the second gyroscope 4 is f z_2 , then the conditions for judging the resonance of the stepper motor system are:

[0042] f z_1 =f z_2(3)

[0043] In engineering applications, it is often impossible to achieve z_1 With f z_2 In order to make an approximate judgment, the threshold Δf is set. z , when |f z_1 -f z_2 |<Δf z When , it is considered that the stepper motor system resonates. Threshold Δf z The setting of is specifically defined according to the characteristics of the stepper motor model, system, and load, and is not limited in the present invention.

[0044] 3. Resonance processing

[0045] When a stepper motor system resonates, the PWM frequency and stepper motor torque pulse frequency issued by stepper motor controller 1 may overlap with the natural frequency of stepper motor 2, causing vibration and resonance. Since the natural frequency of stepper motor 2 remains unchanged, it is necessary to move the PWM frequency and stepper motor torque pulse frequency out of the natural frequency range of the stepper motor. There are two specific methods:

[0046] a) Adjust (increase) the PWM frequency to between the natural frequency of stepper motor 2 and its multiple.

[0047] Assume that the PWM frequency is f P , the natural frequency of the stepper motor system is f G , then the natural frequency and its multiples are:

[0048] k·f G , k=1,2,... (4)

[0049] The adjusted PWM frequency is

[0050] k1·f G <f P <k2·f G , k2>k1≥1 (5)

[0051] b) Increase the subdivision number of the stepper motor.

[0052] Increasing the subdivision number of the stepper motor can reduce the current pulse of the winding inside the stepper motor, thereby reducing the torque pulse and the vibration of the stepper motor. Assume that the original subdivision number set by the stepper motor controller is M O , the new number of subdivisions is

[0053] M N =2 k ·M O , k=1,2,...(6).

[0054] The innovation of the present invention is:

[0055] 1. Build a vibration detection and processing system for the stepper motor system using dual-channel gyroscopes, wireless transmission, universal joints, and bearings. Perform dynamic resonance detection on the stepper motor system through distributed gyroscopes, improving detection accuracy. Reduce system structural complexity and wiring difficulty through wireless transmission, improving data transmission quality. Build a vibration measurement platform for the stepper motor output shaft using universal joints and bearings to practice the separation of shaft torque output and vibration measurement.

[0056] 2. The vibration signals of the motor side and output shaft (near the load) of the stepper motor system are measured by dual gyroscopes and compared and judged, which improves the accuracy of resonance judgment and provides an accurate basis for resonance processing.

[0057] 3. By adjusting (increasing) the PWM frequency to between the natural frequency of the stepper motor and its multiples and increasing the number of subdivisions of the stepper motor, the risk of resonance caused by spectrum overlap, current and torque shock can be effectively avoided.

[0058] It should be noted that, in this document, relational terms such as first and second, etc., are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or terminal device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or terminal device. Without further limitation, elements defined by the phrase "include..." or "comprising..." do not exclude the presence of additional elements in the process, method, article, or terminal device comprising the elements. Furthermore, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the number itself; "above," "below," "within," etc., are understood to include the number itself.

[0059] Although the above embodiments have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the above descriptions are merely embodiments of the present invention and do not limit the scope of patent protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present invention.

Claims

1. A stepper motor system resonance detection and processing method, characterized in that: The stepper motor system includes a stepper motor connected to a stepper motor controller, a first gyroscope, a second gyroscope, and a bearing. The first gyroscope is fixedly arranged on a main body casing on a non-output shaft side of the stepper motor. A non-rotating platform is built on the output shaft of the stepper motor system connected to a load. The platform is connected to the output shaft of the stepper motor by a bearing, and the platform is connected to a fixed body by a universal joint. The second gyroscope is installed on the platform. The first gyroscope and the second gyroscope transmit data to the stepper motor controller by wireless transmission. It is judged whether the vibrations detected by the first gyroscope and the second gyroscope are consistent. If they are inconsistent, the stepper motor system does not resonate. Otherwise, the stepper motor system resonates, and the PWM frequency and the stepper motor torque pulse frequency are moved out of the natural frequency range of the stepper motor.

2. The stepper motor system resonance detection and processing method according to claim 1, characterized in that: The method for determining whether the vibrations of the first gyroscope and the second gyroscope are consistent is as follows: after the stepper motor controller receives the vibration time series value, the value of each frequency point is obtained by discrete Fourier transform, as shown in formula (1), and the significant vibration frequency at the first gyroscope and the second gyroscope is obtained by obtaining the maximum value of the frequency point, where DFT[] is a discrete Fourier transform operator, x(i) is the i-th value of the vibration signal time series, n is the length of the time series, f(k)=DFT[x(i)],k=0,1,...n; i=0,1,...n (1) f z =max{f(k)},k=0,1,...n (2) Assume that the significant vibration frequency of the first gyroscope is f z_1 , the significant vibration frequency of the second gyroscope is f z_2 , then the condition for judging the resonance of the stepper motor system is: |f z_1 -f z_2 |<Δf z Set the threshold Δf z , when |f z_1 -f z_2 |<Δf z When , it is considered that the stepper motor system resonates.

3. The stepper motor system resonance detection and processing method according to claim 1, characterized in that: The method for moving the PWM frequency and the stepper motor torque pulse frequency out of the stepper motor natural frequency range is as follows: a) Adjust (increase) the PWM frequency to between the natural frequency of the stepper motor and its multiple Assume the PWM frequency is f P , the natural frequency of the stepper motor system is f G , then the natural frequency and its multiples are: k·f G ,k=1,2,... (4) The adjusted PWM frequency is k1·f G <f P <k2·f G , k2>k1≥1 (5) b) Increase the number of subdivisions of the stepper motor Increasing the subdivision number of the stepper motor can reduce the current pulse of the internal winding of the stepper motor, thereby reducing the torque pulse and the vibration of the stepper motor. Assume that the original subdivision number set by the stepper motor controller is M O , then the new number of subdivisions is M N =2 k ·M O , k=1,2,... (6)。 4. The stepper motor system resonance detection and processing method according to claim 1, characterized in that: The first gyroscope and the second gyroscope are three-axis gyroscopes.

5. The stepper motor system resonance detection and processing method according to claim 1, characterized in that: The wireless transmission method is Bluetooth or WIFI.

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