IK mode when base is not dynamic

[johnrowlay]

Hello,

I am using the 6-DOF Kinova MICO arm, and want to control it in IK mode, by dragging a target dummy around with my mouse. If I just import the model as it is, set all joints to IK mode (hybrid), create the tip-target arrangement, and then set up the IK calculation module, this works fine.

However, what I want to do is to raise the robot arm upwards, so that the base of the arm is "hovering" above the table. This is because in the real world, my robot is mounted on a mechanism which raises the robot upwards.

So, to achieve this in V-Rep, I turned off "Body is dynamic" for the base link of the robot, and then set the position of this base link to be at the required height. This prevents the base link from falling downwards under gravity, and raises the entire robot upwards.

But now when I move the mouse around and try to get the tip to follow the target, it does not work as before. Instead, the entire robot disconnects at the joint between the base link and the second link, and falls to the floor.

Therefore, it seems that dynamics needs to be enabled for the entire robot if I want to use the IK calculation module. Is this correct? Are there any ways I can solve this? The obvious solution is to create my support mechanism in V-Rep, but this seems like overkill when the effect is simply raising the robot upwards a little...

Thanks.

[coppelia]

Hello,

you need to post your scene for me to understand what you really want to do, I am a little bit confused. But you have to be careful: your robot model should either be dynamically enabled, or dynamically not enabled (i.e. purely kinematic). Do not mix both things, since you will end-up with very strange situations/behaviours.

Cheers

[johnrowlay]

Hi,

Thanks for your reply.

An image of my scene is here:



So, I want the base of the robot to be "hovering" above the floor, and to do this I have turned off dynamics from the base link, and then set its position to be offset from the floor. All the other links are then dynamic, and all joints are in hybrid IK mode.

If you are saying that my robot should be either all dynamically enabled, or all dynamically disabled, then how would you suggest I achieve what I want? As it stands, I have a mixture of both.

Thanks!

[coppelia]

Ok, of course, you can have the base of your robot static, and the rest dynamic. But you can't have a static respondable shape mounted on top of a dynamic part.

In any case, I still can't see what your problem is. Maybe posting your scene instead of a picture is better.

Cheers