Delay-Adaptive Control of a 7-DOF Robot Manipulator: Design and Experiments

Abstract

We present an analytical design and experimental verification of trajectory-tracking control of a 7-DOF robot manipulator with an unknown long actuator delay. To compensate for this unknown delay, we formulate a delay-adaptive prediction-based control strategy to simultaneously estimate the unknown delay while driving the robot manipulator toward the desired trajectory. To the best of the authors’ knowledge, this article is the first to present a delay-adaptive approach for a nonlinear system with multiple inputs. Through Lyapunov analysis, we first establish local input-to-state stability with respect to temporal derivatives of the reference trajectory, along with regulation of the tracking errors when the reference trajectory approaches a stationary configuration. Then, through both simulation and experiment, we demonstrate that the proposed controller is capable of tracking the desired trajectory with desirable performance despite a large initial delay mismatch, which would cause nonadaptive prediction-based controllers to become unstable.