Dvnamic.anal Vsis and Control of Lightweight Arms with a Parallel Mechanism

A parallelogram drive enables lightweight arms to have a higher rigidity and to reduce the actuator weight moved. Analysis of the flexible closed kinematic chain dynamics and design of the control are described in this paper. The system dynamics is derived by the Lagrangian formula via the assumed mode method. Holonomic constraints due to the geometry of the parallelogram mechanism must be imposed on the dynamics. An orthonormal basis has been. computed from the singular value decomposition of the constraint Jacobian matrix in order to eliminate the constraint force in the equations of motion. The comparatively large workspace and fast motion make motion control with flexibility in each link computationally demanding. The general rigid control (GRC) is implemented to overcome these problems. The solution algorithm checks the constraint violations. Numerical simulation illustrates the results under feedback control.