Synchronization and efficiency analysis of a direct-drive multi-motor application

This paper presents the results of a technical feasibility study concerning the direct-drive conversion of an existing four-axis wire processing machine. The objective is to obtain a considerable efficiency improvement, while maintaining equal speed and angle synchronization properties as the substituted gearbox mechanics. A control algorithm based on the method of `electronic line shafting´ is implemented and verified with simulations and experiments on a test setup. The controller emulates the inter-shaft state feedback of a physical gearbox resulting in comparable synchronization performance during load disturbances, acceleration and emergency stop conditions. The efficiency improvement potential is verified with measured efficiency maps of all drivetrain components. In the nominal operating point, the direct-drive machine outperforms the conventional machine with 14% due to the avoidance of gearbox losses and the application of highly efficient permanent magnet synchronous motor technology.