Co-located control

Colocated vs. noncolotated = actuator and sensor at the same location vs. actuator and sensor at different locations.

Typical situation: standard DC motor and encoder either on the motor shaft or attached to the load. Flexible shaft can then make the difference in how easy or diffucult it is to control the position of the load.

Z.H.

Another example is a flexible manipulator/robot. Picture a very flimsy piece of aluminum attached to a motor shaft representing a single link robot (this could be used for a pick and place task). If the robot arm is very thin then as the motor provides a torqe moves the link, it will flex and bend. If we wanted to control the tip position and velocity (tip rate) of this one link robot then we would have a non- collocated input output mapping. The input is the joint torque supplied by the motor, and the output is the tip position/rate and the input (torque) is not applied at the same poisition as the output we want to control, the tip. If we assume that the robot arm is now very very stiff, and we take the input to be the motor torque, but the output to be the angular position of the arm (theta and theta_dot) then this is a collocated input-output map. The input is applied at the same position as the output we want to control.

Hope that helps,

JRF