Development Rotating Workspace Observer based on Novel Kinematics for Two-link Manipulator with Biarticular Actuator Coordination and its Application for Translational Motion

This paper proposes totally novel kinematics, statics and dynamics of a two-link manipulator and develops a control algorithm based on them which enables two-link manipulators behave more like human or animals. There are two main points: introduction of biarticular muscle/actuator coordination and utilization of the rotating reference frame instead of the fixed frame. These two points are also related to the biomechanics and natural dynamics; humans and animals have the biarticular muscles playing important roles in their motions, and the motion of humans’ extremities are usually modeled using the rotating reference frame. The paper reveals that these two points are also important in analysis and control of a two link manipulator, particularly when the two link manipulator needs to behave like a human’s extremity. The motions of a two-link manipulator are re-described based on these points, which provides simple and straightforward understanding of the motions of an endeffector. Based on this understanding, a rotating workspace observer is designed and found to be theoretically robust to the singular point since it does not have any function of the joint angles in the denominators of the observer design. Using the rotating workspace observer, Two-degree-of-freedom control is proposed in the proposed reference frame. Comparative simulations verifies the effectiveness of the proposed controller and the proposed reference frame.