Browse Publications Technical Papers 2023-01-0452
2023-04-11

Sensorless Control of a Brushless Motor for the ESC Unit 2023-01-0452

In general, automatic braking uses an electric stability control (ESC) hydraulic unit that can automatically increase the hydraulic pressure in the wheel cylinder (hereinafter called wheel pressure), independent of the driver’s braking operation. The hydraulic unit should have sufficient pressure response to apply autonomous emergency braking (AEB). It was necessary for the hydraulic unit to have a high flow rate for the pressure response.
To satisfy the performance requirements of the AEB, a brushless motor, which has a high maximum rotational speed and good response, is adopted for the hydraulic unit. Furthermore, sensorless control, which does not require a rotation angle sensor, has been developed so that the motor size can be small and common to conventional units.
The developed sensorless control can switch the driving methods in three states: pre-rotation, low speed, and high speed. In the pre-rotational state, the magnetic poles are judged to quickly determine the initial position of the motor rotor. The rotational speed in the low-speed range was estimated based on the disturbance superimposition method. Subsequently, the rotational speed in the high-speed range was estimated based on the extended guidance method. The sensorless control can drive the brushless motor with the same performance as that of a system equipped with a rotation angle sensor over a wide range of rotational speeds.
A sensorless control system that has the same performance as a system equipped with a rotation angle sensor was developed, which allows the miniaturization of the motor.

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