Mobile manipulators provide larger working spaces and more flexibility than standard manipulators by introducing mobility. Through teleoperation, they can be applied to a variety of areas such as hazardous material handling, outer space exploration, searching and rescue, etc.Inspired by application requirements, there are four major challenges in the teleoperation of mobile manipulators including the modeling and control of mobile manipulators, teleoperation of multiple mobile manipulators, modeling the human teleoperator in teleoperation system and communications between the human teleoperator and mobile manipulators. Therefore, this study aims to address these challenges.For the modeling and control of mobile manipulators, the motion accuracy of the end-effector is a problem for the existing methods due to the system performance differences. To address this issue, we introduce a new control method with online motion distribution and coordination to improve the accuracy. In addition, a sensor-based redundancy resolution scheme is proposed to further improve the teleoperation efficiency.For the teleoperation of multiple mobile manipulators, the system stability under random communication delays and unexpected events is a major problem for the existing methods. To address this issue, we propose a non-time based teleoperation and coordination method. A non-time perceptive reference is designed as the new reference to replace the time in the system modeling and control. Through this design, the system stability under random communication delays and unexpected events could be ensured.For modeling the human teleoperator in teleoperation system, there are no existing models and the teleoperation efficiency and safety are always subject to the operation status of the teleoperator. To address this issue, we propose a concept named quality of teleoperator (QoT) to represent the teleoperator and incorporate it into the modeling and control of the teleoperation system. Through this design, the teleoperation efficiency and safety could be improved under various operation status of the teleoperator.For the communications between the human teleoperator and mobile manipulators, the existing methods of using joysticks are neither efficient nor intuitive. Therefore, we introduce the natural language as a new communication manner. However, the existing natural language control methods could not online handle unexpected events in the environment and robotic system. To address this issue, a new systematic natural language modeling and control method is designed to online handle such unexpected events.Finally, the proposed methods are all implemented on our developed mobile manipulators and the experimental results illustrate their effectiveness and advantages.
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