Task-space tracking control without velocity measurements

Focuses on the problem of tracking a desired end-effector position and orientation for a robot manipulator. A nonminimal parameterization of the orientation-the unit quaternion-is used to design the control law. Tracking control typically requires full-state measurements, i.e., end-effector position and orientation as well as linear and angular velocities. However, while position and orientation measurements are available, often velocities have to be estimated. In the paper, an observer-controller scheme is proposed which ensures tracking in the task space without using velocity measurements. The performance of the proposed scheme is evaluated both in simulation and through experimental tests on an industrial robot.