Event-Based Collaborative Planning and Control with Loosely-Coupled Transportation Model for Dual Mobile Manipulators

Dual mobile manipulators (DMMs) possess the advantages of high redundancy and extensive working space, enabling robot systems to undertake more complex tasks, such as the collaborative transportation of objects with stereoscopic shapes. Some existing works have addressed the collaborative transportation tasks under the tightly-coupled transportation model. Nevertheless, there have been few studies on the transportation issues in the loosely-coupled transportation model, where the problems such as the difficulty of maintaining formation configuration and high requirements for internal force stability exist. To this end, this paper presents a new event-based planning and control approach. First, the motion forms during the transportation process are classified for the collaborative transportation scenarios of objects with stereoscopic shapes, and an event-based motion planning strategy is provided. Then, by combining admittance control and nonlinear feedback control, a force-position hybrid control method is designed to control the force and position errors during the transportation process. Experimental results indicate that compared to the time-based method, the proposed event-based method can better guarantee the collaborative performance of the DMMs system during the transportation process. To the best of our knowledge, this may be the first attempt to solve the collaborative transportation problem of DMMs with loosely-coupled model by the event-based method.