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Time optimal trajectory planning for formation driving of Mars rovers
2008 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Currently the research on Mars exploration rovers is under much investigation. The motivation of this thesis work stems from the blind formation driving of future MER missions. The Mars rover prototype in our laboratory is the indoor MERLIN car-like robot. The main goal of this thesis is time optimal trajectory planning for the leader robot in formation group. Several planning methods have been investigated and the proposed trajectory planning method has been verified with simulative and experimental tests on real hardware. Firstly, one standard path planning method, Visibility Graph Method, and one newly developed method, Ferguson Cubic Splines Method are employed for distance optimal path planning under kinematic constraints of car-like robot. User interfaces are built and both methods are simulated in Matlab. The comparison between them shows the advantage of Cubic Splines Method. Secondly, the time optimal trajectory planning with cubic splines is studied, in which both kinematic constraints and dynamic constraints are considered. The velocity profile under these constraints is established in light of path curvature and the distance from the path to the nearest obstacle. The key of trajectory planning is how to obtain the feasible velocity profile that satisfies acceleration limit. An efficient algorithm is developed to solve this problem and is verified with simulation. The main advantage of the planned trajectory is the continuous velocity profile and steering angle profile, which satisfy both kinematic and dynamic constraints. Finally, the proposed trajectory planning algorithm is verified through driving experiments with the indoor MERLIN robot. A PID controller on speed is designed for stable outputs. The steering angle is calibrated and a real-time measuring method for steering angle is tested. Example trajectories with time-variant curvature and velocity profile are implemented.

Place, publisher, year, edition, pages
Keyword [en]
Technology, path planning, trajectory planning, time optimal trajectory, car-like robots, kinematic constraints, dynamic constraints, formation driving
Keyword [sv]
URN: urn:nbn:se:ltu:diva-45555ISRN: LTU-PB-EX--08/005--SELocal ID: 33c50398-1b95-474c-8351-03f87702d6edOAI: diva2:1018849
Subject / course
Student thesis, at least 30 credits
Educational program
Space Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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