Method to reduce resonance of servo motor (take Panasonic servo as an example)

---

Hey! I’m [Xiao Huang], let’s meet again! ! ! After all, technology can only be improved by communication! This blog is a little record and summary of your own learning. If you are interested in automatic control, you can pay attention to my dynamics. Let's learn together! We are still young, and we have endless possibilities. YES!

---

After we debug the servo parameters, the robot will move to a certain position and it will produce vibration or abnormal noise. What we have to do is to eliminate this abnormal noise and maintain the accuracy of the servo.

1. Preparation:

1. Notebook computer with Panasonic servo debugging software.
2. A debugging cable (miniusb-trapezoidal port data cable)

1.1.1 How to estimate the resonance point:

1. Open Panasonic PANATERM
2. Click on the main screen tool bar [ Others ]-[ Frequency Characteristics ]
3. 【Frequency Characteristics】Window
4. Click Measure -open the measurement window
   

[Filter]: The degree of filtering.

[Pointer]: Perform conversion whether the pointer indicates or not.

[Cutoff Frequency]: The corresponding frequency when the gain is -3dB.

[Measurement Mode]: Measurement mode.

Speed ​​closed-loop characteristics Speed ​​command ~ frequency response of motor speed.

Torque speed (normal) Frequency response from torque command to motor speed.

Torque speed (vertical) Frequency response of torque command to motor speed. It is used when the vertical axis applies partial weight to the motor.


( MINAS-A6 series, measurable position loop characteristic level. )

② Slider for vertical axis

Change the [Position] and [Magnification] of the vertical axis of the Baud curve (④).

③ Slider for horizontal axis

Change the [Position] and [Magnification] of the horizontal axis of the Baud curve (④).

④ Bode curve

Show the measured frequency characteristic data through a graph.

5. [Amplitude]: A simple understanding is the amount of movement you want the motor to run

When the measurement mode is [Speed ​​Closed Loop Characteristics], the sum of amplitude and deviation is limited to the range of 5000r/min. When the measurement mode is [Torque-Speed], it is limited to 100%.

※Increase the amplitude to improve the accuracy of measurement. When the amplitude is excessively increased, the torque reaches saturation, but the accuracy of the measurement decreases. Therefore, in actual measurement, please start with a smaller value,--while observing the measurement result--slowly increase the amplitude value.

6. [Offset]: My understanding is to increase the range of forward and reverse

When the sum of amplitude and deviation is limited within the range of 5000r/min, the measurement mode cannot be set to [Torque-Speed] mode.

※ The offset set in the measurement will act as an average speed command. The polarity is + represents the positive direction, and the polarity is-represents the negative direction. If the bias is above the set value of amplitude, generally better measurement results can be obtained when the motor rotates in one direction. However, when the movable range is small, it may exceed the limit of movement. Please be careful. The rotation amount of the motor during the measurement operation can be roughly obtained by the following equation. Please confirm before starting the measurement--be sure not to exceed the moving limit.

Target value of revolution [r] = offset [r/min] X 0.017 X (sampling rate +1)

7. [Sampling rate]: can be set to any value from 0 to 7

※ The sampling rate becomes larger, the measurement accuracy of the low frequency band is improved, and the measurement time becomes longer. On the contrary, the sampling rate becomes smaller, and the measurement accuracy of the high frequency band improves. First, the sampling rate starts from 0, and the sampling rate is adjusted while observing the measurement results.

※ When the sampling rate is 1 or higher, there may be superimposed noise foldback! ! !

8. Click [ Execute ]: Check the current motion state of the motor (preferably the middle position of the stroke )

1.1.2 Measurement practice:

1. Enter the amplitude value-click to perform measurement
   
2. Get the measurement image
   
3. Point on the pointer-can display the corresponding [frequency], [gain] and [phase] corresponding to the current point
   
4. It is sufficient to input the result of measuring the bump into the first notch. (As long as it is not higher than OdB, it is generally not resonance)
   

1.1.3 Summary:

1. Trigger conditions No trigger can monitor the resonance frequency. See the resonance period to calculate the resonance frequency.
2. Frequency characteristic curve-monitor that the resonance frequency does not exceed 0, or if there is no resonance, both positive and negative run tests (10, 20). Check the frequency of the highest point and the tip and enter the first notch frequency (width and depth are empirical values, and depth is the image span The larger the setting, the smaller the depth, the greater the stability, and the better the stability) After the instruction is smoothed, no adjustment is required.
3. Stiffness can also be understood as stiffness responsiveness. It is also possible to produce abnormal motion noise, not silent motion.
4. Torque command vibration cannot exceed 10%. After exceeding 10%, the response (rigidity) will be reduced
5. The first torque filter suppresses resonance.
6. The servo motor keeps loudly sounding. It may be that the rigidity adjustment is too high, not necessarily because of resonance.

2. The next preview:

I am Xiao Huang, a silly wage earner.


The [Three Lian] of the audience masters is the great motivation for Xiao Huang's creation . See you in the next issue! YSE!!!!


Note : If there are any errors or suggestions in this blog, you are welcome to leave a message, come to Kangkang!