Kinematic-free position control for a deformable manipulator

A novel deformable manipulator with intrinsic safety for the home service robot, which is composed of rigid joints and deformable links, is studied in this paper. As the deformable links can be bent according to different tasks, the deformable manipulator obtains relatively dexterous end-effector and extended workspace to deal with multiple tasks. However frequent changes in the links' shapes bring difficulties to the kinematic model and control of the deformable manipulator. Thus a practical kinematic-free controller with no prior kinematic information is proposed in this paper. It is based on the hypothesis that the Jacobian matrix of the manipulator is almost constant in a local region. It can be estimated by actuating each joint independently an incremental amount and observing their effects on the robot's end-effector, instead of identifying the kinematic parameters. The controller is implemented to control a 4-DOF deformable manipulator in simulation. It is able to control the robot's end-effector to reach a desired position, as well as to track continuously a desired path. Besides, it can cope with the drastic changes in kinematic parameters, which is very difficult for the conventional model-based controller.