Direct Torque Control with Ripple Reduction Strategy for EPAS Brushless DC Motor over FOC

Field Oriented Control (FOC) has been widely used for controlling Brushless DC motors (BLDC) used in Electric Power Assisted Steering (EPAS) systems. This is majorly because FOC provides better performance at lower speed, compared to other algorithms available in market. But the design complexities and cost of EPAS ECUs are much higher due to transformations and the rotor position sensor involved. This paper suggests the use of Direct Torque Control (DTC) over FOC, due to its quicker dynamic response, lower complexity and better response at higher speed. A simple Ripple Reduction Strategy (RRS) with data smoothening and filtering is introduced to improve the performance at lower speed. The DTC with RRS is modeled in MATLAB /Simulink. The Simulation results are compared with that of FOC, to prove the effectiveness of DTC. This algorithm for BLDC motor control ensures simpler hardware, lower cost, better performance and less development time, leading to cost and design optimized EPAS power-pack modules. DTC with RRS can be used as an alternative for FOC, especially in lower-end vehicles, where cost of production plays an important role.