Distributed Cascade Force Control of Soft-Tactile-Based Multi-robot System for Object Transportation

In this paper, we present a distributed cascade force control system (DCFC) for multiple robots with the aim of pushing a rigid object towards a desired moving target without their inter-robot communication. These mobile robots are equipped with 360-degree vision-based soft tactile sensors utilized to determine contact location and resultant impact force. By investigating the dynamics of moving rigid objects on the flat, we proposed a distributed cascade control. The inner loop control incorporates contact force and positioning, ensuring the robots' pushing contact and applying the desired force to the object. The outer loop control coordinates the robots to push the object in a desired direction without inter-robot communication, regardless of unknown object mass and friction uncertainty. The stability and convergence of the control system are verified using the Lyapunov stability theory. We also conducted simulation and real-world experiments to validate the performance of the proposed control method, and the experimental results showcase the successful coordination of multiple robots in pushing an object towards a moving desired direction.