An Adaptive Admittance or Force Control for Robotic Manipulators

In this paper an adaptive compliant motion control is presented for either constant admittance or constant force mode of operation. From a desired trajectory of the admittance and virtual position in the task space, a virtual trajectory is generated to follow the desired admittance. We are talking about admittance because at the interaction port of the end effector the force is measured and a generated virtual trajectory will be followed. Using a suitable Liapunov function the controller guarantees a stable control law by continually estimating the manipulator parameters and using these to effectively follow the virtual trajectory. After contact is established with the environment there is the facility of implementing adaptive constant force control. The method is illustrated by a simulation study to control a two-link manipulator, whose end effector can move in a horizontal plane, but constrained by a wall. Experimental results are also presented from laboratory tests using a Bosch Turbo Scara robot.