How to keep a solid stationary even when a force is acting upon it?

Question

Samuel Hayward 2019-8-12

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https://ww2.mathworks.cn/matlabcentral/answers/475836-how-to-keep-a-solid-stationary-even-when-a-force-is-acting-upon-it

回答： Steve Miller 2021-10-25

time_now_fixed_with_models_v4.slx

Hello,

I am trying to have a solid cube (10 10 10 cm) remain stationary when a force acts upon it.

The cube is connected to a prismatic joint and the force comes from a Generic Linear Actuator using a translation 3D-to-1D interface (Simscape Mulibody Multiphysics Library). The joint is also connected to another solid, a rotary arm, I want the rotary arm to move as normal.

I have tried connecting the solid to the world frame, however, this causes an error to occur (model not assembled error). I have also applied the appropriate setting to allow for forces to act on rigid bodies and not produce an error message.

I have inserted the Simulink/Simscape file in question, the area of concern is subsystem 2.

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SYED IMTIAZ ALI SHAH 2019-8-14

Dear Samuel Hayward, You have attached Linear Acutator between Red Block and Solid 5 (Arm). It proudces actuation in Z direction. (Rigid Transform3). The motion that you see (revolute) is due to the reaction force of Red Block on the Arm.

Now

Do you want you Red Block firmly attached to Arm?

Do you also want rotation?

if you want the above why not fix (remove prismatic joint) the Red block to Arm and use DC Motor for revolute joint?

Dont you think a simple DC Motion will make life easy?

Samuel Hayward 2019-8-14

I do not want the red block attached to the arm, I want to have it remain stationary in space. I am trying to learn how to keep objects stationary even when a force i acting on them, this is so I can apply this knowledge later on in future iterations of this simulation model.

I do not want rotation, the force acting on the arm is to be linear, the Generic Linear Actuator is currently acting as a stand-in until I can simulate a double-sided permanent magnet lineat synchronous actuator (there are only rotational PMSMs premade in Simscape at the moment).

Thank you for your time and interest in my query.

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Answer 1

Steve Miller 2021-10-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/475836-how-to-keep-a-solid-stationary-even-when-a-force-is-acting-upon-it#answer_815638

time_now_fixed_with_models_v4_sm.slx

Hi Samuel,

I adjusted your model so that the red brick is rigidly attached to ground using a Rigid Transform, and the motor is applying its force directly to the red brick. The red brick does not move.

When you attach an item to ground between two different paths (via the arm and via the Rigid Transform to hold it in place), you have to make sure those paths are consistent. I used a Transform Sensor to measure the distance to the World Frame and used those values to set the offset in the Rigid Transform block.

--Steve