Global Consensus-Based Formation Control of Nonholonomic Mobile Robots With Time-Varying Delays and Without Velocity Measurements

In this article, we propose a solution to the full-consensus-based formation problem for torque-controlled nonholonomic mobile robots under time-varying communication delays and without velocity measurements. Under the assumptions of static and undirected communication topologies, and smooth and bounded delays, we propose a distributed smooth, time-varying control law which achieves the goal of acquiring a global formation pattern in a common consensus point for both position and orientation. The controller is a combination of a simple proportional-plus-damping (PD) scheme and a simple globally exponentially convergent velocity observer. Consensus is reached independently of all initial conditions. Realistic simulations in the Gazebo-robot operating system environment illustrate the effectiveness of the proposed algorithm and the robustness with respect to measurement noise, nonsmooth delays, and uncertain dynamics.