A comparison between optimal LQR control and LQR predictive control of a planar robot of 2DOF

This work employs a LQR (Linear Quadratic Regulator) predictive control as well as a LQR controller to control the angular servomotor positions of a planar robot of 2DOF (2 Degrees of Freedom). The goal of such a pantograph type robot is to manipulate the X-Y positions of a 4-bar linkage end effector using two rotary servo base units connected to two revolute joints. Three unactuated revolute joints complete the five links of the robot. Experimental results demonstrate that the LQR predictive controller performs better than the LQR controller, because the former controller is able to diminish the steady-state error between the Cartesian coordinates with respect to the desired coordinates.