IMC102t Initial jerk problem

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ES1
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I am using 6pole BLDC motor with sensor less method when I try to run the motor to sense the initial angle motor goes back  and rotating forward this process is creating a huge jerk in our application is it any way to eliminate this issue and i have tried initial angle sensing it is creating some annoying noise how can I resolve this issue.

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Krupashankar
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Hi @ES1,

Can you please share  the following:

  • MCE Wizard Configuration file (.mc2)
  • Power board and control board current sensing section schematic

Please make sure the initial speed ramp is smooth with lower acceleration to avoid any jerk and sudden movement.

 

Thanks,

Krupashankar

 

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Krupashankar
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Hi @ES1,

Initial angle sensing works well if the Ld-Lq ratio is less than 95%.

For a better start of the motor please ensure the following:

  • Proper current sensing and configuration.
  • Proper motor parameter measurement and configuration.
  • Please make sure the inverter board can supply enough power for a smooth start.

Can you please share the following:

  • Motor datasheet 
  • Configuration file 
  • Let us know if any fault is triggered?
  • Control/Power board schematic

This will help us to understand the issue better.

 

Thanks,

Krupashankar

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Hey hi thanks for your fast reply i have attached the motor specs and parameter file please check

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Viswa
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Hi @ES1 

 

What is the shaft load?

If the initial load is high for the shaft to rotate then please try the method outlined in the attached document

Driving high inertia loads with iMOTION™ 2.0

If the initial load is higher for the motor to rotate,

initially when the motor tries to rotate the torque applied will be lower, and the load on the shaft will rotate it in the opposite direction. To reverse this phenomenon we need to give higher torque during start.

The document provided will help in this regards.

Best Regards

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ES1
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hey hi viswa I am trying in run the motor in no load condition but still jerk happens because to know the rotor position i want to know how to reduce this jerk.

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Krupashankar
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500 replies posted 50 likes received 25 likes received

Hi @ES1,

Can you please share  the following:

  • MCE Wizard Configuration file (.mc2)
  • Power board and control board current sensing section schematic

Please make sure the initial speed ramp is smooth with lower acceleration to avoid any jerk and sudden movement.

 

Thanks,

Krupashankar

 

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Hi @Krupashankar  

I have implemented initial angle sensing so the speed from 0 to max vibration/Jerk is resolved 

but while ramp down still vibration is present.

can you suggest any parameter change will resolve this problem

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Krupashankar
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Hi @ES1,

Glad that vibration during startup is reduced.

For the ramp down please make sure the speed is gradually reduced and please make sure regeneration is disabled by making Ques 53 to zero.

For further clarification please share the details as mentioned in previous post and How the speed is commanded?

 

Thanks,

Krupashankar

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Hi @Krupashankar

Happy that you had replied !

I have attached the current section and MCE Wizard document in this chat please check,

Regarding  Speed Command I am using Arm cortex M4 with UART communication.

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Krupashankar
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Hi @ES1,

Can you please modify the below parameters and share the test result:

  • Make sure regeneration is disabled by making Ques 53 to zero.
  • Ques 60- Flux Estimator Time Constant to 3msec
  • Ques 85- Motor 1 Current Input to ADC offset Voltage - 595 mV
  • Ques 83 - Current Input Scaling 24.5mV
  • Ques 97 hall angle offset is measured and configured correctly

Please make sure the deceleration ramp is smooth and not very rapid, to reduce vibration. 

What is the exact RPM at which the vibration is observed?

 

Thanks,

Krupashankar

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Hi @Krupashankar 

Initial RPM is 200, After it gone to 0RPM  some vibration is coming in the motor assembled body.

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Krupashankar
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Hi @ES1,

Can you please check if the motor is making any noise when it is detached from the load setup or body?

Please make sure the noise is not due to any mechanical vibration.

 

Thanks,

Krupashankar

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Hi @Krupashankar 

With motor alone it creating creating some vibration while its ramping down to zero RPM.

please check the below video.

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Krupashankar
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Hi @ES1,

We can see there is a small jerk in the motor at the stop which can be due to below reasons:

  • The rotor inertia can be high and this can lead to minor movement. This can be avoided by fixing the motor to a frame. 
  • As we can see the motor angle sensing is through the hall sensor, at 0 zero speed the rotor will tend to lock and this can make small vibration. To avoid this can you try giving a stop command instead of zero speed command?

Please let us know if any further details are required.

 

Thanks,

Krupashankar

 

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ES1
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hi @Krupashankar 

Even when i use stop command small jerk is happening at the motor

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Viswa
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Hi 

The small jerk could be due to the system inertia.

please kindly mount the motor onto a frame and observe the system behavior.

 

Best Regards

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ES1
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Hi @Viswa 

I have attached the motor in a rigid frame even this jerk occurs after mounting also,

Is there any way I can reduce this jerk .

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Krupashankar
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Hi @ES1,

Once the STOP command is given to the iMOTION controller the PWM signals are off. Then the vibration caused is only due to Motor inertia. Please make sure the load is evenly balanced.

 

Thanks,

Krupashankar

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