Efficient Cable Path Optimization Based on Critical Robot Poses for Industrial Robot Arms

Abstract

Although industrial robotic arms are equipped with external cables to supply electricity, gases or other materials, cable path design is a difficult and demanding task. Herein, an efficient optimization method is proposed for automating cable path design under the assumption that the robot motion path is known. The contribution of this study was to reduce the considerable computation time required for the optimization, which was a concern in our previous work. The previous method represented candidates for cable paths as a set of parameter vectors (PVs) that included cable length and guide configurations, and then selected the optimal PV that satisfies stress constraints and provided the shortest cable path. The proposed method extracted critical poses, i.e., several static robot poses that are prone to applying stress to the cable, from the joint angle time series of the motion path, and then performed attachment and motion tests. The cable geometry for the static critical poses was simulated in the attachment test, while the geometry for dynamic robot motion was simulated in the motion test in an ascending order of the cable length among the PV candidates. Experimental results showed that the computation time for cable path optimization could be significantly reduced.

Cable path optimization by fixing multiple guides on one link for industrial robot arms

“…In this study, we propose a cable path optimization method for a complex motion as an extension of the previous methods [15,16]. As described in Section 1, the previous method [16] performs static cable geometry simulation for critical poses 1) in the attachment test to reduce the number of PV candidates and then applies dynamic cable geometry simulation for robot motions in the motion test to find the ECPV with the shortest cable length that satisfies the stress and robustness constraints. Note that the previous method, which assumes only simple motion, fixed up to one guide to one link so that the attachment test dealt with only the inter-link segments.…”

“…As in the previous works [15,16], the objective of this study is to design a cable path with the shortest cable length that satisfies three stress constraints for a given robot motion.…”

“…However, this tracking was considerably burdensome. Therefore, Iwamura et al [16] defined several static robot poses that are prone to cable stress during motion as critical poses. The cable stresses for these critical poses were quantified with the significantly reduced burden.…”

“…As the number of guides increases, the computational burden increases due to the expansion of the solution search space. As a result of profiling the computational burden of each process in the previous method [16], the computation of connected geometry turned out to have a relatively heavy burden. The connected geometry is the geometry of the cable segment that connects the guides at both ends and is used as an initial geometry in the physical simulation considering gravity to determine the convergent geometry of the cable segment.…”

“…Fig. 1 shows the iterative deformation of the cable segment in the previous method [16]. The simulation of the cable segment geometry starts with the linear geometry, which connects one end to one guide (Fig.…”