Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

Differential equation to define transfer function for Sisos control in motionView

Hi, I’m currently modelling the operation of car hood in motionview, and I use sisos control to control the velocity of the gas spring during open or close process of car hood.

First, I modeled the gas spring in motion view by stiffness coefficient k, damper coefficient c, preload and free length.

after that, i set up the siso control with the idea is described in the image below:

Input is the error between reference velocity and real velocity of gas spring

Output is force

Then, I try to applied the second law of Newton to find out the differential equation to define transfer function for property field of siso control.

According to provided information , I first try with the equation Fcompession = Fgas + Ffriction. But I supposed that this way is not true because I’ve already modeled the gas spring by k, c, preload and free length parameters

So that, I try to write another different differential equation based on the parameters that I set up for gas spring in motionview

But it came out that the equation presents the relationship between the force (F) and the displacement (x). But I think what I need for sisos control is that the transfer function that addresses the link between force and velocity of gas spring.

So, I hope that I could find help in determining the transfer function for sisos control field from anyone of the Altair community.

Thanks in advance!!!

Find more posts tagged with

MotionView/MotionSolve

Accepted answers

GTT Adam

Hi @hoantuan123_12,

To better understand the implementation of the SISO controller, you can first refer to the following tutorial example:

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/simulating_siso_intro_t.htm

In addition, here is a tutorial on implementing differential equations:

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/modeling_diff_equations_intro_t.htm

Please review the following examples in case you haven't already.

I will also work on a more applicable example for your system, which I will post shortly.

Hope this helps!

Adam Reid

GTT Adam

Hi @hoantuan123_12,

Here is an example of a lid opening simulation I created to help demonstrate the implementation of a SISO controller.

mvms_siso_hood_open_2025_1_rev00_archive.zip

The model originally contains a plate, constrained on one end to ground via a revolute joint. There is also an actuator with a spring and damper attached to lift the plate upwards. I have given the spring and damper arbitrary values such that it will open the lid nearly to the intended angle.

Here, the plate will lift with a certain speed and to a certain final angle. With the addition of a SISO controller, however, we can influence the opening speed and also the final angle.

To achieve this, 3 solver variables, 1 SISO controller, and 1 force are created:

The solver variables track the current angle, the target angle, and angle error.
- The target angle is given by a STEP function, but can be any intended curve.
The SISO controller accepts the angle error signal and produces a response based on the coefficients defined within
- I have designed this as a PI controller, so only 2 numerator and denominator coefficients are defined.

The force scales the output of the SISO controller and applies it to the actuator

After the modifications, we can now see the change in the opening profile and final angle:

The target opening profile (blue, top) is nearly matched by the measured opening profile (yellow, top). Some additional tuning could be accomplished, but this is a product of the spring settings and the geometry as well. The error (green, top) is relatively low due to the response of the PI controller.

Hope this helps!

Adam Reid

All comments

GTT Adam

Hi @hoantuan123_12,

Do you need to actually solve the differential equation, or do you just want to define a SISO controller to achieve the ideal velocity profile of the hood opening?

Hope this helps!

Adam Reid

hoantuan123_12

Hi @GTT Adam
I just want to define a SISO controller to achieve the ideal velocity profile. And I'm struggling to define what exactly the numerators and denominators of the controller are.
Thanks!

GTT Adam

Hi @hoantuan123_12,

To better understand the implementation of the SISO controller, you can first refer to the following tutorial example:

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/simulating_siso_intro_t.htm

In addition, here is a tutorial on implementing differential equations:

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/modeling_diff_equations_intro_t.htm

Please review the following examples in case you haven't already.

I will also work on a more applicable example for your system, which I will post shortly.

Hope this helps!

Adam Reid

hoantuan123_12

Thank you very much!

GTT Adam

Hi @hoantuan123_12,

Here is an example of a lid opening simulation I created to help demonstrate the implementation of a SISO controller.

mvms_siso_hood_open_2025_1_rev00_archive.zip

Here, the plate will lift with a certain speed and to a certain final angle. With the addition of a SISO controller, however, we can influence the opening speed and also the final angle.

To achieve this, 3 solver variables, 1 SISO controller, and 1 force are created:

The solver variables track the current angle, the target angle, and angle error.
- The target angle is given by a STEP function, but can be any intended curve.
The SISO controller accepts the angle error signal and produces a response based on the coefficients defined within
- I have designed this as a PI controller, so only 2 numerator and denominator coefficients are defined.

The force scales the output of the SISO controller and applies it to the actuator

After the modifications, we can now see the change in the opening profile and final angle:

Hope this helps!

Adam Reid

hoantuan123_12

Thank you, there’s another thing that I want to ask for helping. Honestly, I have to define the transfer function theoretically to compare the results from simulation with theory. But I find it pretty hard to define with my model. Here is the example that I found, so do you have any ideas about this?
Thanks!!!