Automobile EPS temperature observation method based on extended state observer

Abstract The swing temperature usually leads to the parameter drift and even failure in Electric power steering (EPS), which is a potential threat for safe driving of automobiles. Power Metal-Oxide-Semiconductor Field Effect Transistors (MOSFET) are a primary heat source in EPS and, therefore, can directly represent the temperature fluctuation of EPS. Existing technologies that observe the temperatures of MOSFETs are restricted by operating conditions, cost and implementation difficulty for application in automotive EPS systems. To address this issue, a novel real-time junction temperature observation method is proposed by combining a Foster network with an Extended State Observer (ESO) technique. Transfer paths of thermal resistance in EPS converters are analyzed, and the thermal state space model is established by the Foster network. The temperature ESO of the EPS controller is then developed based on this thermal model to estimate the temperature and perturbation. Confirmation tests that introduce a simulated driving steering method measure the MOSFET temperature and verify the validity of the temperature ESO. The test results demonstrate that the proposed temperature ESO can be used to monitor junction temperatures of MOSFETs in EPS.