An Analytical Stiffness Method for Spring-Articulated Planar Serial or Quasi-Serial Manipulators Under Gravity and An Arbitrary Load
A novel analytical method based on a virtual joint approach is proposed to characterize the stiffness of the spring-articulated planar serial or quasi-serial manipulators under an arbitrary load while considering the weight of the manipulator and the actuator stiffness. Particular attention is focused on investigating the joint and Cartesian positioning errors of the manipulators, following which the torque or force transmission efficiency through the structural compliance is interpreted. The Compliant Uniformity Index is defined by conducting the mapping between the torque and positioning error spaces for evaluating the structural compliance and the uniformity of positioning errors. Several one and two degree-of-freedom spring-articulated planar serial or quasi-serial manipulators are employed to illustrate the proposed method and index.