On Perpendicular Curve-Based Model-Less Control Considering Incomplete Orientation Constraint

With the emerging trend of soft and reconfigurable robots, model-less control methods become more and more popular. However, the incomplete orientation constraint (IOC) remains a challenge for the existing model-less control methods, due to the nonlinear structure of the rotation group. To address the IOC problems, in this article, we develop a novel perpendicular curve-based approach, which provides a closed-form expression of the shortest path from current orientation to the target geodesic in SO(3). Based on our approach, we propose a new model-less robot motion control framework considering the IOC. Compared with the existing methods, the proposed method can easily accommodate any robots with four or more actuators regardless if they are functionally redundant or not. The proposed method has been conducted on a four-DOF reconfigurable manipulator with an unknown kinematic model, which is the most challenging case since the dimension of the configurational space is smaller than the dimension of the task space. The simulation and physical experiment results demonstrate the effectiveness and advantages of the proposed method.