Dual-User Haptic Teleoperation Of Complementary Motions Of A Redundant Wheeled Mobile Manipulator Considering Task Priority

With the increasing applications of wheeled mobile manipulators (WMMs) in diverse fields, new challenges have arisen in achieving multiple sub-tasks, including obstacle avoidance in a constrained environment without intervening in the end-effector operation. Dual-user/two-handed teleoperation of WMM can help accomplish these requirements with human intelligence involved. Combining a mobile platform (MP) and a robotic manipulator usually makes a WMM a redundant system that can achieve multiple tasks using the null-space control. The existing control approaches for WMMs are executed mostly at the kinematic level, without considering the nonlinear rigid-body dynamics of the WMMs. In this paper, a task priority-based trilateral teleoperation framework with two local robots and one WMM is implemented. It can simultaneously manipulate the MP and the end-effector (EE) (obstacle avoidance is achieved by MP control in the WMM system’s null space). The residual redundancy can be further employed for other tasks as singularity avoidance. The control target is achieved in three stages: 1) a stability-guaranteed joint-level adaptive motion/force controller is designed for each system, 2) a task-priority based redundancy resolution is adopted to avoid interference between the tasks, and 3) Cartesian-space reference velocity vector is designed to achieve position tracking and force feedback between the local/master and the remote/slave subsystems. Experiments with a dual-user teleoperation system, consisting of two local robots and an omnidirectional WMM, are conducted to verify the proposed approach’s feasibility and effectiveness.