An Application of LQ Control to a Two Link SCARA Manipulator

A Linear Quadratic (LQ) controller is a logical improvement beyond a classical Proportional-plus-derivative (PD) controller. In this paper, an LQ tracking controller using gain scheduling is designed for a task on an idealized two degree of freedom SCARA Manipulator. The LQ performance is evaluated alogside that of a PD tracker operating on the same idealized manipulator model performaing the same task. Following this, a more complete model of the manipulator hardware is used to evaluate the robustness of the controllers in performing the task. The effects of friction and load parameter variations are investigated, as are the effects of unmodelled dynamics in the drive motors.