Thread Subject: Modelling of Environmental Contact

Hi!

I have modelled a robot using SimMechanics in the simulink. I can easily simulate the motions of this robot in free space. However, now I would like to add some objects in the environment and would like to see the behaviour of the manipulator when it comes in contact with these objects.

These objects are hard stiff metal blocks completely attached to the ground, so the robot does not cause any motion to these objects but rather changes its behaviour by measuring the contact forces.

Can someone explain how should I add these objects in Simulink? In addition, I would like to know if I can add some sort of force sensor to measure these contact forces.

Thanks,

"Ali" <muhammad.ali@tut.fi> wrote in message <h93dbq$5kv$1@fred.mathworks.com>...
> Hi!
>
> I have modelled a robot using SimMechanics in the simulink. I can easily simulate the motions of this robot in free space. However, now I would like to add some objects in the environment and would like to see the behaviour of the manipulator when it comes in contact with these objects.
>
> These objects are hard stiff metal blocks completely attached to the ground, so the robot does not cause any motion to these objects but rather changes its behaviour by measuring the contact forces.
>
> Can someone explain how should I add these objects in Simulink? In addition, I would like to know if I can add some sort of force sensor to measure these contact forces.
>
> Thanks,

You need to define a point on your body and put a joint such as 6DOF between that point and the relevant ground point. Then using a joint sensor, you can measure the relative distance between that point and the ground, and when it becomes negative or less than a certain value, you can apply a restoring force to that joint using a joint actuator.

See for example the bouncing ball demo mech_bouncing_ball.mdl in SimMechanics. Here, it just measures the global coordinates of the CG and when the height is less than the radius of the ball, it applies a restoring force using a body actuator.

HTH,

Arnaud