How to get oscillatory motion for a solid in simscape?

I was quite fascinated with simscape and I am trying to learn it. I am considering a basic parallel mechanism or five bar mechanism as shown in figure. As of now I have

made two set of links in simscape (L2 = light blue or black; L3 = Green) (L5 = purple or red; L4 = Dark blue). I am trying to give motion to L2 and L5 and check the trajectory of point "D". In the attached excel sheet I have computed few set of angles for L2 and L5 such that the point "D" will move in a semicircle trajectory (pink color).

The angles mentioned in the excel sheet will make oscillatory motion but in the simscape model which I made, the links are rotating completly for 360 degrees. Could anyone kindly figure out how to give input to the mechanism such that the mechanism at point "D" will make a semicircle according to the angles mentioned in the excel sheet.

Answer 1

[Juan Sagarduy]

Hello there,

In order to do the work, I'd recommend to use Simscape Multibody to build the five-bar linkage mechanism. In Multibody, you can prescribe the motion in the joints (kinematic mode) so that they fulfill a given duty cycle. This gives info on the actuation torque needed. So what you need to do once the model is created is to apply the motion patterns you have obtained in Excel. We have training for Simscape Multibody you may find rewarding. Modeling Multibody Mechanical Systems with Simscape | MATLAB and Simulink Training (mathworks.com)

Best of Luck / Juan

[Man R]

Hello Juan,

I have made the five bar mechanism in Simscape Multibody. This is a two degree of freedom system, that is, I am providing motion to two revolute joints.

I m giving oscillatory motion to the revolute joint but the link is rotating completely.

Just to make you understand what I m facing, I have created a simple one link pendulum in Simscape Multibody, I sincerely request you to download the 'trial.slx' file and 'Angles.xlsx' excel file and run the simulation. The excel data has time and angles in degrees. Please load the data from the excel sheet in a variable "data_for_sim" in matlab command window and run the .slx file. The angles mentioned in the excel should make the link oscillate instead the link does a complete rotation and it keeps going, it doesn't stop.

I want the link to oscillate, how do I achieve that?

Thanx in advance.

[Juan Sagarduy]

Hi there,

It was down to a detail that is easy to overlook when starting with Simscape. The angle you want to prescribe is in deg, but the Simulink-PS Converter unit is set to 1 >> Multibody believes it is radian instead. So if you set the unit to deg, the rotation is exactly as you want. Attaching the model as well (just load kinematic_cycle.mat first).

Cheers Juan

[Man R]

This works. Brilliant!

I express my deep sense of gratitude for helping me out.

There were other alternates avilable on the internet but I wanted to realise what is the mistake I m doing.

Thank you once again.

Cheers

MR