How to model a translational shift of two axes of motors with Matlab Simscape?

I have modelled a grinding process using two PMSM motors. Since it is still a simple idealized process. I am trying to add some real characteristics of the process:

https://de.mathworks.com/help/releases/R2024b/sps/ref/pmsm.html

I added to the PMSM Motors and their FOC blocks some mechanical Blocks like the inertia and the velocity/motion sensor.

I am now looking for a way how to model a translational shift of the axis of the motors. Since the grinding process of the involved round surfaces (Grinder and the grinding object) looks like the following:

I have found out that I can use a Springer-Damper-System to model the rotation of the motors with a translational shift od the axis.

Or the Block translational Hard Stop, but the Problem is that I could not connect the block with the mechanical (green circuits of the model):

https://www.mathworks.com/help/simscape/ref/translationalhardstop.html

Does anyone here have an idea how to model such translational/mechanical shift using simscape blocks?

I appreciate any Information or help from you guys!

Greetings and thanks a lot.

Answer 1

[Aabha]

Hi @Ramo,

There are a few ways in which the translational shift of the motor axes can be modelled in Simscape.

1. Convert the rotational motion of the motor shaft to translational motion using the “Wheel and Axle” block in Simscape. The wheel and the axle, in this mechanism, have the same axis, and it is assumed to be rigidly connected to the frame. The mechanism has two connections: a mechanical rotational port "A", which corresponds to the axle, and a mechanical translational port "P", which corresponds to the wheel periphery. Please refer to the following documentation for more details: https://www.mathworks.com/help/sdl/ref/rackpinion.html
2. Convert the rotational motion of the motor shaft to translational motion using the “Rack & Pinion” block in Simscape Driveline. This block represents the rack and pinion gear that constrains the pinion "P" and rack "R" to rotate and translate together in a fixed ratio, respectively. This ratio can be adjusted as per requirements. Please refer to the following documentation for more details: https://www.mathworks.com/help/sdl/ref/rackpinion.html

Both of these blocks can be connected to the “Translational Hard Stop” block, to constraint the motion.

I hope this is helpful.

[Ramo]

Hi @Aabha

Thanks a lot for your help and detailed answer.

Since I have modelled the two mechanical parts using a PMSM Motor: See the example:

https://de.mathworks.com/help/releases/R2024b/sps/ug/three-phase-pmsm-drive.html

I am not sure how to use these 2 Blocks to shift the axis of the PMSM motor.

I thought of using a PI/PID-Controller to change the Position of the motor. But the Position that I get using the motion sensor is the rotational position.

and since I am using a FOC for the control of the motor speed. I am not sure how to do a linear shift of the motor axis using the wheel axle or Rack & pinion..

Do you have any suggestions, especially without impacting the control of the motor speed?

[Yifeng Tang]

Adding to @Aabha's answer. The wheel and axle block sounds like a good option. A friction block can be used to mimic the tangential force/torque during the grinder. If the two wheels are of difference size, the shaft torque need to respond differently then.

If you have access to the Driveline, there is a "Loaded-Contact Translational Friction" block can model the friction as a function of input normal force. That can be useful too.