Drive Control Development of Switched Reluctance Motor for Compact Electric Vehicles 2019-01-0460
Today, many automakers are actively pursuing the advancement of electric vehicles (EVs). Induction motors and interior permanent magnet motors (IPMs) are most commonly used as traction motors for EVs. In this project, we focused on the development of switched reluctance motors (SRMs) as an alternative motor for compact EVs, leveraging the following benefits of SRMs: 1) SRMs, which require no permanent magnets, have no drag torque, enabling clutchless motor applications, and 2) SRMs demonstrate high efficiency in the high speed rotation range. In SRM applications to EVs, however, two challenges need to be resolved: The first challenge is that SRMs have greater torque ripples due to the principle of torque generation. This may result in a start-up failure of a vehicle on an uphill, depending on the rotor position. The second challenge is that cruise control is necessary to realize autonomous driving, but there are very few EVs equipped with SRMs capable of cruise control.
In this project, torque ripple is reduced by 40% with the developed control technology by changing command currents for phase current conduction in a linear fashion, which is verified by motor characteristics testing. Furthermore, the optimization of switchover timing between power running control and regenerative control has enabled cruise control of compact EVs, maintaining a constant speed, as proven by the driving test results of a vehicle with the developed SPM. These successful outcomes indicate the developed system offers an innovative solution to the torque and cruise control challenges in SRM applications to compact EVs.