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Path Following Control System for car-like Unmanned Ground Systems

The path-following control system for unmanned visually guided car-like vehicles was developed. This control system is working in one of our prototypes, a Citroën C3 Pluriel, but it could be work in our other prototypes, an Iveco Eurocargo ML150E18 or other car-like vehicle.

Fig. 1: Citroen C3 Platform Fig. 2: Iveco ML150E18 Platform

The control system generates a steering wheel signal reference (the following of the reference of the steering wheel is controlled thanks to an external low-level controller) to achieve the path-following. The inputs of this control system are the measured speed of the vehicle, measured by the speedometer of the car; the measured steering wheel angle, measured by an encoder attached in the steering wheel; the measurements given by the computer vision system that are the measured distance to the circuit, the measured angle between the tangent of circuit and the symmetry axis of the vehicle and some punctual codes read that gives some information about the position of the circuit. The last input of the control system is the circuit and vehicle information available.

Fig. 3: Platform Scheme: Two inputs and five outputs

The control system is composed by two main blocks, an state estimator in charge of the analysis the inputs of the control system and calculate the better estimation of the vehicle state (see State estimation for the path-following of visual unmanned ground systems) and a controller to close the loop using the estimation of the vehicle state (see Controller for the path-following of visual unmanned ground systems and Adaptive controller for the path-following problem of a car-like mobile robot based on its kinematics model using linear control theory).

Fig. 4: General Control System Loop

The performance of the control system was demonstrated, getting speeds up to 50 km/h in an egg-shape test circuit which longest straight stretch is about 42 m. The circuit was never lost in a 50 minutes test.