Active Thermal Management of EMB Motors Considering Winding Heat Imbalance

The electro-mechanical brake (EMB) system represents a novel dry brake-by-wire technology renowned for their superior control performance and compact structure, effectively meeting the demands of intelligent electric vehicles. However, its performance can be compromised under extreme ambient temperatures and non-uniform heat generation across the coils. This study addresses the critical challenge of single-phase overheating in the EMB motor actuator during low-speed high-torque operations by proposing a novel Maximum Duration Per Torque (MDPT) control strategy. The core of this method is to optimize the allocation of dq-axis currents. It aims to extend the safe operating duration of the EMB while respecting its thermal constraints and maintaining full braking performance. Firstly, based on the operational characteristics of the EMB, we establish a lumped parameter thermal network (LPTN) model. This model accurately captures the uneven thermal distribution among the three-phase windings and enables real-time prediction of the remaining safe operating time under various current distributions per phase. Using a sequential quadratic programming (SQP) algorithm, we efficiently compute the optimal d- and q-axis current references that maximize this duration. A triple-loop controller based on the MDPT algorithm is designed and validated through simulations and experiments. Results show that the proposed method significantly extends the safe operating time compared to conventional Maximum Torque Per Ampere (MTPA)-based strategies. This study shows that effective thermal management of electromechanical brake systems, implemented through the design of control algorithms, which ensures the durability of the system and the reliability of driver safety, is achievable.