Need some help on Alter( )

[wantrg]

Hi everyone,

Currently I'm working on Staubli TX60 robot with CS8C robot controller. I'm using ALTER function to do real time modification based on force/torque sensor and I set the ALTER function to work in world coordinate. I've a force/torque sensor on the robot end-effector and I want the robot to move proportional to applied force. For example, if 2N is sensed in x-axis, so robot will move about 2mm in x-axis. This would work for translational part (x,y,z), but it totally goes wrong during orientation (Rx,Ry,Rz). For example, at beginning the robot rotates about 30degrees in y-axis and then I want to move the robot 10mm in x-axis. The final position is totally different from the position that I want the robot to move. I think the problem is caused by ALTER function that is always refer to the start position. Even the orientation change the robot still refer to the start position. Or maybe I'm wrong. Is anyone know how to solve the problem?

Hope someone can help me.

Thank you.

Wan

 

[Spielkind]

Hi Wan,

first of all I think you are wrong saying that alter always referenced to the start position.
As far as I know, the alter is always applied on the actual position.
For me it is not clear, what you want and what the robot is doing.
You know, that alter can work on a fixed frame and also on a specific tool?
I suppose, you mixed the orientation change of the tool and the orientation change of a frame?
Keep also in mind, that the order of calculation is important:
Doing first an orientation change and then a move along x is different from first moving along x and then apply an orientation change.

Hope it helps

Spielkind