Image-Based Wire Position Detection for a Flexible Twisting Process of Hairpin Stators

As the mobility sector shifts its focus towards electric vehicles, the demand for electric traction motors continues to rise. The hairpin process chain has recently emerged as the industry standard. In contrast to continuous windings with round cross-section wire, hairpin technology is based on discontinuous bending, insertion, twisting, and welding of individual hairpins coils, resulting in inflexible production equipment and complex tooling. The sequential twisting process represents a robot-based alternative to the tool-based twisting process, contributing to the economical production of hairpin stators in small quantities and in prototype manufacturing. It is of particular importance that the wire ends are in their target position after twisting for the downstream welding process. However, the actual final position of the wires can deviate due to various influences, such as the springback of the wire or collisions between neighboring wires. Furthermore, reliable threading of the wire ends is also essential for the robustness of the sequential twisting process. To address these issues, an image-based method for the in-line detection and control of the wire positions is proposed in this paper. To achieve this, a robot cell is equipped with a high-resolution camera. A methodology is developed for the detection and matching of wire ends, with the objective of extracting their position. The resulting wire position data can then be used for further examinations of the twisting process and for a closed-loop wire forming control.