Trilateral Shared Control of a Dual-User Haptic Tele-Training System for a Hexapod Robot With Adaptive Authority Adjustment

Considering the increasingly widespread use of multilegged robots in various fields, the design of their bilateral or multilateral teleoperation system is facing new challenges, such as foot slippage, tele-driving skills, and operators experience, which can induce activity of its teleoperation and poor maneuverability. With the assistance of an experienced trainer and the development of a multi-user cooperative teleoperation system, it is more conducive to tele-driving the multilegged robot in real field environment. Accordingly, in this study, a novel trilateral shared control architecture based on the velocity and force coordination of a dual-user haptic tele-training system for a hexapod robot subjected to soft terrain is proposed. Its methodology simultaneously considers the online transfer strategy of the task authority adjustment between dual users and the dynamic compensation approach for the active exogenous disturbance. In our system, the dominance factor adjusts the control authority of dual users according to the velocity and force command-tracking performance of the trilateral system. The closed-loop stability of the system is established by its passivity, and the force applied by the environment termination is determined to be approximately equal to the sum of the forces felt by two operators. The experiments of the proposed dual-user haptic training system for the hexapod robot demonstrate that it results in a stable trilateral teleoperation with a satisfactory tracking performance.
Note to Practitioners
—Multi-legged mobile robots have been widely used in daily and scientific scenarios, including industrial manufacturing, field exploration, and domestic service. However, as tasks and requirements become larger and more complex, the difficulty of development increases. To overcome these issues, this paper proposes a trilateral tele-training architecture for teleoperating the movement of a hexapod robot on deformable terrain, with complications such as foot slippage. The shared control method incorporates primarily two novel technical contributions, which refer to an adaptive authority adjustment method to allocate control between trainer and trainee operators, and a passivity controller (an adaptive damper) informed by observed loss in the remote robot’s velocity (both of which can be executed simultaneously). The former is implemented with a varied dominance term. Two different shared control methods are proposed, one which essentially relies on the errors in provided position inputs between the two leaders and the follower (position-error-based, PEB), and one that examines torques applied to the operators compared with environmental interaction force (direct force reflection, DFR). In addition, the practitioners who research in fields where efficient control of cooperative teleoperation for multi-legged robots subject to outdoor environment can benefit from these proposed methods. In future research, we will further address the dynamic teleoperation of hexapod robot and time delays.