Modification of constrained LQR for control of walking in-pipe robots

In this paper, a new control method for walking in-pipe robots is discussed. The method is based on a combination of a linear quadratic regulator for systems with explicit mechanical constraints and a proportional-derivative controller formulated in terms of end effector coordinates (Cartesian coordinates of the robot's foot that takes the step). The performance of the proposed method is measured using a quality criteria discussed in the paper. A nine-link walking in-pipe robot is used as an example in simulations. The simulation show that the proposed method improves the performance of the control system. Also, simulations demonstrated that the control system using the proposed controller is not sensitive to torque saturation and the changes in the initial conditions.