Global Trajectory Generation for Nonholonomic Robots in Dynamic Environments

We consider the problem of generating global feasible trajectories for nonholonomic mobile robots in the presence of moving obstacles. The global trajectory is composed of regional path segments, which are parametric polynomials incorporating collision avoidance criteria. Collision avoidance with moving obstacles is achieved by changing parameters of the regional trajectories, and the collision avoidance parameters are solutions to a second-order inequality and are obtainable analytically. To have a smooth global trajectory, we also develop a smooth irregular curve method to generate continuous boundary conditions to connecting regional trajectories. Steering control laws are constructed by means of differential flatness. The proposed technique works in dynamic environments where a set of global way-points are available, and the velocities of the obstacles are obtainable real time. Simulation results show the effectiveness of the methods.