Adaptive Time Delay Control of Robotic System Subject to Payload

For accurate position tracking of robotic system subject to payload presence and payload variation, an adaptive time delay controller is proposed. First, the conventional time delay control (TDC) which is simple in structure and does not depend on the model of the system is employed to offset all the nonlinear terms in the dynamic model of the robotic system. Next, using a sliding variable, a payload adaptive law is designed to adapt to the payload presence and payload variation in the robotic system. Furthermore, a time delay estimation (TDE) error adaptive law is designed to suppress the TDE error caused by the conventional TDC. Finally, since two control gains in the conventional TDC need to be chosen, a control gain adaptive law is designed to adjust one control gain automatically. The stability of the closed-loop system is proved via Lyapunov stability synthesis and simulations are conducted on a 2-DOF robot. With the proposed adaptive time delay controller, position tracking performance of the robotic system can be achieved even there exits payload presence and payload variation. Meanwhile, it can effectively suppress the TDE error and it only needs to adjust one control gain.