Mobile Robots Current Trends Part 4

Tham khảo tài liệu 'mobile robots current trends part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Gaining Control Knowledge Through an Applied Mobile Robotics Course 79 minimize the distance to the path by performing a turning action. Otherwise the desired point distance should be minimized Pacheco and Luo 2006 . Orientation and desired point distances can be considered as important data for achieving proper path-tracking. Their deviation errors are used in the control law as necessary information for going forward or turning. Students have to compute Cartesian distances between the robot and the trajectory to be followed. Fig. 9 depicts these concepts for two cases. Fig. 9. a Straight line trajectory from Px1 Py1 to Px2 Py2 . b Straight line trajectory from Px2 Py2 to Px1 Py1 . The proposed control law is based on sending the same speed to both wheels when the robot distance to the trajectory is less than a heuristic threshold and different speed to each wheel in order to perform a turning action when such distance is greater. As can be observed in Fig. 9 the turning action must be different as a consequence of the robot position up or down the trajectory or the trajectory sense. Fig. 10 shows a trajectory following experience with two straight lines that have a 90 angle. X cm Fig. 10. Example of trajectory following experiences using discontinuous control laws and PID speed controllers. 80 Mobile Robots - Current Trends Trajectory following using MPC techniques In this subsection the LMPC local model predictive control techniques based on the dynamics models obtained in the previous subsection are presented. LMPC strategies are simulated in the laboratory by using the methods and software developed by those of our teaching staff participating in the course Pacheco and Luo 2011 . The LMPC formulation The main objective of highly precise motion tracking consists in minimizing the error between the robot and the desired path. Global path-planning becomes unfeasible since the sensorial system of some robots is just local. In this way LMPC is proposed in