Design And Implementation Of A Trajectory Generator For An Indoor Mobile Robot

Abstract

The objective of this paper is to describe a method for computing the trajectory motion for an indoor mobile robot so that the path transcribed by the robot from a start point past some intermediate points and to the goal point is continuous and predictable. The route that the platform is to take is defined by a series straight line paths between sequential points in space, connected by circular paths at the junction of two lines. Whenever possible, the radius of the circular transition path is that which allows the platform to keep the same desired linear speed defined for the straight line portions of the trajectory. The method described uses three points to calculate the platform's trajectory. They are, the present platform's position, the intermediate point and the end point. The straight line path, defined by the present and the intermediate point, is connected by a clothoid spiral to the circular arc in between the two straight lines. The clothoid curve is the platform's path at the time it is accelerating towards a constant angular speed, which is characterized by a circular arc curve. Similarly another clothoid curve connects the end of the arc to the straight line path defined by the intermediate point and the end point. This paper concentrates on the computation of the transitional path (clothoid) between the straight line path and the circular arc that occurs because the platform has a finite angular acceleration. This paper also outlines how this routine has been integrated within a hierarchical control system for a mobile platform. 'Ihc tnijcclory generator and thc mobile plat fonii coiilrollcr nrn under Harmony', a real-time multiprocessing operating system designed for robot control.