Articles | Volume 6, issue 2
https://doi.org/10.5194/ms-6-245-2015
https://doi.org/10.5194/ms-6-245-2015
Research article
 | 
26 Oct 2015
Research article |  | 26 Oct 2015

Successive dynamic programming and subsequent spline optimization for smooth time optimal robot path tracking

M. Oberherber, H. Gattringer, and A. Müller

Abstract. The time optimal path tracking for industrial robots regards the problem of generating trajectories that follow predefined end-effector (EE) paths in shortest time possible taking into account kinematic and dynamic constraints. The complicated tasks used in industrial applications lead to very long EE paths. At the same time smooth trajectories are mandatory in order to increase the service life.

The consideration of jerk and torque rate restrictions, necessary to achieve smooth trajectories, causes enormous numerical effort, and increases computation times. This is in particular due to the high number of optimization variables required for long geometric paths. In this paper we propose an approach where the path is split into segments. For each individual segment a smooth time optimal trajectory is determined and represented by a spline. The overall trajectory is then found by assembling these splines to the solution for the whole path. Further we will show that by using splines, the jerks are automatically bounded so that the jerk constraints do not have to be imposed in the optimization, which reduces the computational complexity. We present experimental results for a six-axis industrial robot. The proposed approach provides smooth time optimal trajectories for arbitrary long geometric paths in an efficient way.

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Short summary
The time optimal path following problem for industrial robots regards the problem of generating trajectories that follow predefined end-effector paths in shortest time possible, taking into account kinematic and dynamic constraints. This paper proposes an approach to deal with arbitrary long geometric paths. Further a method is presented to achieve suitable smooth trajectories for an implementation on a real robot, in an easy way.