Development of a six DOF haptic master for teleoperation of a mobile manipulator

An intuitive controller is needed for easier teleoperation of a slave robot. The mobile manipulation task requires three DOFs for planar mobility and six DOFs for 3-D manipulation. Since existing six DOF haptic devices have not been adequately developed for mobile manipulation, they are inefficient for planar three DOF motion. In this paper, a design for a six DOF haptic master suitable for tasks involving mobile manipulation is presented. The proposed device adopts a separable structure composed of lower and upper mechanisms. The lower parallel mechanism offers three DOFs for planar motion, and the upper parallel mechanism mounted on the lower mechanism provides the remaining three DOFs for a total of six DOFs; thus, the workspace can be extended into a full six DOF representation. This separable feature provided efficient actuation and reduced computational burden since only three actuators were involved in the planar task. Moving bodies should have low inertia to improve the back-drivability and transparency; therefore, all actuators were placed at the base, and torques were delivered via wire-driven transmission. A kinematic analysis was performed, and design parameters were determined through workspace analysis. Various experiments demonstrated that the proposed mechanism was efficient for a planar task, and also adequate for a full 3-D task.