Performance Analysis of Elastic Band Based Time Optimal Control Formulations for Industrial Robots

Abstract: Industrial robots are becoming an integral part of the production industry. Efficientoperation with respect to fast movements is critical to increase the economicbenefits of automating the production line. Facilitating near optimalitywith regards to time has high computational demands however and multipleframeworks have been suggested to remedy this. In this thesis we consider oneof these frameworks, namely the elastic band framework. We investigate howthe elastic band time optimal control framework performs regarding computationaltime for point-to-point movements on a SCARA type robot with threerevolute and one prismatic joint. We compare an unconstrained elastic bandformulation with a constrained formulation in the open loop, along with simulatingperformance in the closed-loop. We show that a constrained formulationwhich considers the sparseness of underlying matrices in the optimizationproblem has the lowest computational time. Additionally, we show that the unconstrainedformulation benefits from early stopping. Finally, we show that acontroller implementing this formulation can be used in a model predictivecontroller, although the computational time is still too high for commercialuse on the hardware used in testing.