Linear motor is a transmission device that directly converts electrical energy into mechanical energy of linear motion, and its main output is thrust. The thrust of linear motor will be output to the outside during operation. The instability and fluctuation of thrust is called thrust fluctuation. This fluctuation phenomenon can be caused by many factors. Thrust fluctuation can reflect whether the operation of the motor is stable.
1.Causes
1.1.Magnetic field inhomogeneity
The inhomogeneity of magnetic field distribution will cause thrust fluctuation. This may be caused by quality problems of magnet materials, improper installation of magnets, or failure of magnetic field regulating devices.
1.2.Current instability
The thrust of linear motor is directly related to the current size. If the current is unstable, it will cause thrust fluctuation. Current instability may be caused by power quality problems, poor contact of power supply lines, or failure of current regulating devices.
1.3.Mechanical structure problems
The thrust of linear motor is also related to the stability and accuracy of mechanical structure. If there are problems with the mechanical structure, it will cause thrust fluctuation. Such as wear, looseness or inaccurate assembly of parts.
1.4.Control system problems
The stability and accuracy of the control system also have a significant impact on the thrust of linear motors. If there is a problem with the control system, it will cause thrust fluctuations. Such as unreasonable control algorithm, sensor failure or signal interference.
2.Impact of Thrust Fluctuation of The Linear Motor on Motor Performance
2.1. Vibration and noise
Thrust fluctuation is the main cause of vibration and noise in the motor. Especially when running at low speed, this vibration and noise may be more significant. This affects the use environment of the motor and the user experience.
Vibration and noise not only affect the running stability of the motor, but may also cause resonance of surrounding equipment or structures. This will further lead to performance degradation.
2.2. Positioning accuracy and speed control
Thrust fluctuation has an adverse effect on positioning accuracy and speed control system. Especially in applications with high position accuracy requirements, such as robot control. Thrust fluctuation may cause positioning error to increase and affect the overall performance of the system.
In variable speed transmission, once the inherent mechanical frequency of the mover or stator is close to the frequency of thrust fluctuation, the vibration and noise generated by thrust fluctuation will be amplified. This will further deteriorate the servo operation characteristics of the motor.
2.3. Power density and thrust density
Thrust fluctuation may also affect the power density and thrust density of the motor. When using a conventional magnet structure, due to the influence of thrust fluctuation, it may not be possible to get an ideal sinusoidal air gap flux distribution. This may reduce the power density and thrust density of the motor.
2.4. System stability
Thrust fluctuations may also affect the stability of the entire system. Thrust fluctuations can cause vibrations and noise. This can cause performance degradation in other parts of the system and even cause system failure.
3.How to Reduce The Impact of Thrust Fluctuation of The Linear Motor on Motor Performance
Regularly check and maintain magnet materials, power lines, and current regulators. Ensure their quality and stability.
Optimize the mechanical structure of the motor, reduce wear and looseness of parts, and improve assembly accuracy.
Adopt advanced control algorithms and sensor technology to improve the stability and accuracy of the control system.
Use new test methods to improve the accuracy and reliability of thrust fluctuation tests. For example, use a test method in which two linear motors of the same model are mutually loaded.
4.How to Test Thrust Fluctuation of Linear Motor
4.1 Test Preparation
- Select the test equipment: Make sure to use a high-precision thrust sensor to measure the thrust value generated by the linear motor. Such as a pressure sensor or a force sensor.
- Install sensor: Install the thrust sensor on the linear motor. Make sure the installation position is stable and will not change due to motor movement.
- Set test environment: Fix the linear motor on the test bench. Make sure the fixation between the motor and the test bench is firm and reliable to reduce the impact of external vibration on the test results.
- Set test conditions: Set appropriate operating voltage and frequency. Make sure that the linear motor is tested in a stable working state.
4.2 Test process
- Measure thrust value: Start the linear motor and record the thrust value data measured by the sensor. Ensure that the linear motor runs according to the predetermined trajectory and speed during the test.
- Data acquisition: Continuously collect thrust value data to ensure the continuity and integrity of the data. During the test, pay attention to recording any abnormal conditions or changes.
- Repeat test: To get more accurate test results, many repeated tests can be performed. By comparing the results of different tests, the stability and reliability of the test can be evaluated.
4.3 Data processing and analysis
- Data filtering: Filter the collected thrust value data to cut errors and interference in the measurement. This helps to improve the accuracy and reliability of the test results.
- Calculate thrust fluctuation: By calculating the mean and standard deviation of the thrust value, the degree of thrust fluctuation can be evaluated. Thrust fluctuation can be expressed by the root mean square value. That is, the standard deviation of the thrust value is divided by the mean and multiplied by 100%.
- Analyze the test results: Analyze the thrust fluctuation of the linear motor based on the processed data. Compare the results under different conditions to find out the key factors affecting the thrust fluctuation.
4.4 Test method optimization
- Adopt a new test method: A test method in which two linear motors of the same model are mutually loaded can be adopted. This method can avoid the torque fluctuation introduced when the rotating motor is running and improve the accuracy of the test.
- Optimize the test equipment: According to the test results and needs, optimize the selection and configuration of the test equipment. For example, you can choose a higher-precision sensor, a more stable test bench, etc.
- Improve data processing methods: Improve data processing methods for problems and anomalies in the test. For example, use more advanced filtering algorithms, optimize data analysis processes, etc.
Conclusion
In summary, thrust fluctuation of linear motors is an important performance indicator, and its causes are varied. Comprehensive testing, evaluation and control methods are needed to ensure its stability and performance. When designing and using linear motors, the impact of thrust fluctuations needs to be fully considered. Appropriate measures need to be taken to reduce its impact on motor performance.