An Integrated Joint for Cooperative Robots This paper proposes a highpower density integrated joint for the novel cooperative robots. The design trends to be a more compact mechatronical integrated joint with high reliability and accuracy. To achieve this, the main components inside the joint are a harmonic drive, a permanent magnet torque motor, an incremental encoder, a single turn absolute encoder, a brake and a servo drive. This combination of components inside the joints leads to lower weight and smaller outer envelope size. The entirety of the motor shaft and harmonic drive cam can reduce the axial length of the joint. The wires arranged inside the hollow shafts is the critical way to achieve the mechatronical joints. Double encoders configuration inside the joint (incremental encoder feedbacks the motor position and single turn absolute encoder feedbacks the joint position) will achieve the absolute position accuracy less than 0.05mm. Finally, a simulation result is shown to verify the reliability of the designed joint.

Impedance Control Strategy and Experimental Analysis of Collaborative Robots Based on Torque Feedback In this paper, through the modeling and analysis of flexible joints, an impedance controller based on torque feedback is proposed, which is used to realize the active compliance of collaborative robots. The controller includes two parts: torque controller and impedance controller. The torque controller is used to compensate the robot dynamics, and the impedance controller is used to adjust the joint stiffness and damping. The theoretical analysis of the control strategy shows that the significance of torque feedback is that it can reshape the inertia of the motor, reduce friction torque and suppress unknown disturbances. In order to ensure tracking accuracy, a task errorbased disturbance observer is designed. Experiments with a 7DOF collaborative robot show that the proposed controller in this paper can realize the body compliance and obtain better compliance performance than the traditional compliance control method.