Teleoperating a formation of car-like rovers under time delays

This paper addresses bilateral teleoperation of a formation of car-like planetary rovers under communication delays. The mobile robots form a team using the leader-follower approach, with the leader being teleoperated by human operator via a haptic device. Communication delays present in the teleoperation channel, and as well between the leader and the followers. The haptic joystick provides the human operator with a force-feedback mechanism describing the environmental conditions, based on the relative distances and speeds between the rover and the obstacles. The teleoperation is implemented with an impedance controller based on the sliding-mode method, which accomplishes speed coordination. Formation control is developed based on the input-output linearization method. The follower robots keep constant distances and relative bearing angles with respect to the leader. An improved PD-type formation controller is proposed to compensate the delay effect, which is proved to be stable and effective in tracking. Hardware experiments support the implementation of both the teleoperation and the formation controllers, which also showed capability of dealing with variable time delays in the communication channels.