Brushless Motor Control for EV Battery Cooling After Ignition Off
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Solution Overview
Problem
Conventional motor control systems for cooling blowers in hybrid and electric vehicles face challenges in maintaining appropriate cooling of the battery after the ignition switch is turned off, leading to excessive power consumption and requiring additional components like relays, which can fail due to high power consumption and complexity.
Innovation Solution
A motor control system that includes a host controller and a motor control device using PWM command signals to control the rotating speed and operation time of a brushless motor, allowing for efficient cooling of the power supply unit even after the ignition switch is off, with a simple configuration and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electronic control unit continues to operate after the ignition switch is turned off to control the cooling blower, then the cooling control function is maintained, but the power consumption becomes excessive
Solution Approach 1:
The control function is segmented between the host controller (which operates only during driving) and the motor control device (which has autonomous control capability). The host controller transmits a single command signal before shutdown, and the motor control device executes the cooling control independently using its internal timer and PWM signal generation, eliminating the need for the host controller to remain powered.
Solution Approach 2:
The host controller transmits the cooling command and parameters to the motor control device before the ignition switch is turned off. The motor control device stores this information and executes the cooling control autonomously after shutdown, performing the useful action in advance of when the host controller would otherwise need to remain operational.
2Reliability
If additional relays and interconnections are added to transmit cooling commands after engine halt, then the cooling control is achieved, but the device complexity increases
Solution Approach 1:
The cooling control function is merged into the motor control device that already exists for controlling the cooling blower motor during normal operation. The device integrates the autonomous control capability, timer function, and PWM signal generation within the existing motor control architecture, eliminating the need for separate relays and interconnection circuits.
Solution Approach 2:
The motor control device performs self-service by autonomously executing the cooling control function based on the command received from the host controller. The device uses its own internal timer and control logic to manage the motor operation after shutdown, without requiring external control signals or additional control components.
3Measurement precision
If the electronic control unit is used to control the cooling blower, then the control precision is maintained, but the power consumption becomes excessive due to the large amount of power the control unit consumes
Solution Approach 1:
The control system is segmented into a high-power host controller that operates only during driving and a low-power motor control device that handles autonomous control after shutdown. The motor control device maintains precise PWM-based control of the cooling blower using minimal power, separating the high-power computation functions from the low-power execution functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides effective cooling of the battery with reduced power consumption and eliminates the need for additional relays, enhancing the reliability and efficiency of the cooling process.
Implementation Method 1
The host controller modulates a duty ratio of pulses of the PWM command signal by a target rotating speed of the motor, modulates a period of the pulses of the PWM command signal by a continuous operation time of the motor
Implementation Method 2
The motor control device demodulates the received PWM command signal to reconstruct both the target rotating speed and the continuous operation time
Implementation Method 3
controls a rotating speed of the motor based on the target rotating speed
Implementation Method 4
controls a motor of a cooling blower for cooling a power supply unit which supplies electric power to the wheel driving unit
Data Source
AI summary
A motor control system includes a host ECU and a motor control device. The host ECU controls a wheel driving unit. A power supply to the ECU is halted when an IG switch is turned OFF. The motor control device receives a PWM command signal from the host ECU and controls a motor of a cooling blower. The host ECU modulates a duty ratio of pulses of the PWM command signal by a target rotating speed of the motor, modulates a period of the pulses of the PWM command signal by a continuous operation time of the motor, and transmits the result to the motor control device. The motor control device reconstructs both the target rotating speed and the continuous operation time, and controls rotating speed of the motor from the received PWM command signal. Moreover, the motor control device halts rotation of the motor when a signal-unreceiving time period of the PWM command signal becomes larger than the continuous operation time.