Saturated Output Feedback Control for Flexible-joint Robot Manipulators

Considering the limitation of the joint driving torque and the unavailability of partial state measurements, a saturated output feedback control method with flexibility compensation is proposed for flexible-joint robot manipulators. Firstly, using the singular perturbation theory, the dynamics model of flexible-joint robot manipulator is decoupled into fast and slow subsystems. The saturation function is subsequently involved to design the bounded control law of each subsystem and the flexibility compensation term, so as to ensure the boundedness of the system control inputs. Then, considering the unmeasurements of speed on both the link side and the joint motor side in the system, a high-gain observer is designed to achieve the output feedback control that only needs position measurements. At the same time, combining with strict system stability analysis and control law boundedness discussion, the physical domain of control gains of each subsystem is obtained, and online self-tuning of control gains is realized by fuzzy logic. Finally, the effectiveness and superiority of the proposed control method is verified by simulation illustration.