Autonomous vehicles have been studied at least since the 1950s. During the last decade, interest towards this field of study has grown imposingly. Path-following control is one of the main subjects among autonomous vehicles. The focus in path-following control is in controlling of the pose of the vehicle to match with the desired pose, which is provided by a specified path or trajectory. Usually the pose is represented in a two-dimensional world frame by the means of x and y coordinates and angle of heading.
The methods used in this thesis are modelling and simulation (M&S). M&S of physical systems is a well-recognized field of expertise among engineering sciences. Rapid system prototyping, control designing, or studying an existing system by the means of M&S provide possibilities for observing, developing, and testing under risk-free environment. In this thesis, using the M&S methods provides possibilities for fast and economical evaluation of the designed algorithms before considering prototype testing with actual systems under real environments.
Objectives of the thesis are to implement dynamic robot models of two vehicles, design high-level controller structures for their actuators, implement a path-following controller, and study the behaviour of the robots during various autonomous path-following scenarios. The vehicles to be modelled are Ponsse Caribou S10 and Haulotte 16RTJ PRO. The exact study vehicles are owned by Tampere University of Technology.
Results from closed loop path-following control of the modelled robots denoted accurate path-following under well-behaved path curvatures, generally with a mean absolute lateral position error less than 0.1 m. In the best simulation results, mean position errors were under of 0.05 m. The implemented controllers proved to be effective at the whole velocity range of the forwarder Ponsse Caribou S10. The implemented high-level inverse kinematic controllers succeeded in synchronous commanding of the robots’ actuators. Due to the forming of the inverse kinematics, the path-following controller was able to output identical control signals independent of the steering structure of the vehicle, thus permitting a possibility for future development among more advanced path-following control
