Mobile robots with autonomous mobility have been obtaining more and more attention from a large number of people, which have found their applications in logistics, warehousing, service and so on. With rapid development of computer vision, 5G, artificial intelligence and other technologies, the working scenes of mobile robots show features of diversity, complexity and uncertainty. Individual operation shows weakness in efficiency. Therefore, people gradually cast light on the cooperative control of multiple mobile robots.
As one of fundament of multi-robots cooperative control, both trajectory tracking and collision avoidance play an important part. With the increasing number of mobile robots in the urban environment, plus that many uncertain factors and interference, such as pedestrians, buildings, other robots, etc, so that imposing a challenge on safety control of multiple mobile robots. Especially when a group of robots work a shared workspace, high safety risk occurs due to limited workspace.
Motivated by this, Robotic team, Institute of Intelligent Manufacturing, GDAS, investigates the problem of simultaneous obstacle-avoidance and trajectory tracking for multiple wheeled mobile robots (MWMRs) working in the shared environment from the perspective of optimization. A multi-objective control scheme is constructed for MWMRs, which incorporates trajectory tracking、physical constraints compliance and obstacle avoidance simultaneously. Among the proposed control scheme, the trajectory tracking is chosen as the secondary task, and obstacle avoidance is the primary task so that safety can be guaranteed in advance. A Lagrangian-based dynamic controller is constructed for coordinating velocity of every WMR. To reduce complexity of the designed controller, bound constraints on optimization variables are included in the piecewise-linear projection function. Experimental results show that if obstacles do not threaten the safety of the WMR, the top priority in the control task is the target track task. All robots move along the desired trajectory. Once the collision criterion is satisfied, the collision-avoidance mechanism is activated and prominent in the controller. The proposed control scheme can be viewed as a distributed framework owing to robots do not need communicate each other, avoids the defect that the centralized control requires too much communication performance.