Tracking Control With Adjustable Trajectory Envelope for Cable-Driven Robots

In industrial applications, insufficient motor torque and overload issues can limit the control force in cable-driven robots (CDRs), affecting the stability and robustness of trajectory tracking control. This work presents a specialized tracking controller to achieve stable trajectory tracking under constrained control forces. The controller incorporates a trajectory envelope system that actively adjusts the permissible range of the actual trajectory. When control forces approach their upper limits, the envelope automatically expands and reduces the precision requirement for trajectory tracking. The controller then ensures that the actual trajectory remains within the designated permissible boundaries, thereby maintaining controllable trajectory tracking. The stability of the control system is validated using the Lyapunov method. Experimental validations on CDRs with one, two, and four cables are conducted. Both simulations and experiments confirm the effectiveness of the proposed tracking controller under conditions of constrained motor output torque.