Davide Buccieri

Velocity-Scheduling Control for a Unicycle Mobile Robot: Theory and Experiments

Improvement over classical dynamic feedback linearization for a unicycle mobile robots is proposed. Compared to classical extension, the technique uses a higher-dimensional state extension, which allows rejecting a constant disturbance on the robot rotational axis. The proposed dynamic extension acts as a velocity scheduler that specifies, at each time instant, the ideal translational velocity that the robot should have. By using a higher-order extension, both the magnitude and the orientation of the velocity vector can be generated, which introduces robustness in the control scheme. Stability for both asymptotic convergence to a point and trajectory tracking is proven. The theoretical results are illustrated first in simulation, and then experimentally on the autonomous mobile robot Fouzy III.

Brief paper: A numerical sufficiency test for the asymptotic stability of linear time-varying systems

A numerical sufficiency test for the asymptotic stability of linear time-varying Hurwitz systems is proposed. The algorithmic procedure constructs a bounding tube in which the state is guaranteed to stay. The continuous-time system is evaluated at discrete time instants, for which successive quadratic Lyapunov functions are generated. The tube is constructed based on: (i) a conservative estimate of the state evolution, from a discrete time instant to the next, obtained from the corresponding Lyapunov function, and (ii) re-evaluation of the tube diameter at each discrete time instant to account for variations in the plant matrix. The numerical test is illustrated in simulation via both a stable and an unstable system.

Interactive 3D Simulation of Flat Systems: The SpiderCrane as a Case Study

In order to display the main characteristics of a well-known flat system, an interactive 3D simulation of SpiderCrane has been developed using Ejs(Easy Java Simulations) and Matlab/Simulink. The application allows users to set up different trajectories and introduce disturbances in a very visual and attractive way.

Velocity Scheduling Controller for a Nonholonomic Mobile Robot

An improvement over classical dynamic feedback linearization for the control of a nonholonomic mobile robot is proposed. The use of a state extension of higher dimension than in the case of dynamic feedback linearization helps reject constant disturbances on the rotational axis of the robot. The proposed dynamic extension acts as a velocity scheduler for the robot. It specifies at each time instant the ideal translational velocity that the robot should have. By having a two-dimensional state extension, both the magnitude and the orientation of the velocity vector can be generated, which accounts for improved robustness.

A Two-Time-Scale Control Scheme for Fast Unconstrained Systems

Model predictive control (MPC) is a very effective approach to control nonlinear systems, especially when the systems are high dimensional and/or constrained. MPC formulates the problem of input trajectory generation as an optimization problem. However, due to model mismatch and disturbances, frequent re-calculation of the trajectories is typically called for. This paper proposes a two-time-scale control scheme that uses less frequent repeated trajectory generation in a slow loop and time-varying linear feedback in a faster loop. Since the fast loop reduces considerably the effect of uncertainty, trajectory generation can be done much less frequently. The problem of trajectory generation can be treated using either optimization-based MPC or flatness-based system inversion. As proposed, the method cannot handle hard constraints. Both MPC and the two-time-scale control scheme are tested via the simulation of a flying robotic structure. It is seen that the MPC scheme is too slow to be considered for real-time implementation on a fast system. In contrast, the two-time-scale control scheme is fast, effective and robust.

Experimental Results for a Nonholonomic Mobile Robot Controller Enforcing Linear Equivalence Asymptotically

A novel control methodology for a nonholonomic mobile robot is proposed. The methodology uses a two-dimensional state extension and enforces linear equivalence asymptotically. The originality lies in the treatment of singularity. Real-time experiments carried on an autonomous mobile robot called Fouzy III illustrates and justifies the approach