Motor Control Device with Segmented Calculation for Low Current
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Solution Overview
Problem
Existing motor control devices for electric power steering systems face challenges in continuously detecting the motor rotation angle at low current consumption while ensuring reliability, especially when the ignition switch is off, and lack effective methods to reduce current consumption and ensure safety and reliability of calculation means.
Innovation Solution
A motor control device with two operation states, where one state calculates and controls the motor rotation angle based on the motor rotation angle signal, and the other state only calculates the angle, using a resolver and a monolithic IC with separate power supplies and monitoring means to reduce current consumption and maintain reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor control device continuously calculates the motor rotation angle using the motor rotation angle detection means during the period when the IG switch is off, then the absolute position of the steering angle can be detected without error, but the current consumption increases and drains the battery
Solution Approach 1:
The patent divides the calculation function into two separate calculation means: a first calculation means that operates when the IG switch is on to perform both motor control and rotation angle calculation, and a second calculation means that operates when the IG switch is off to perform only rotation angle calculation. This segmentation allows the system to maintain accurate absolute position detection while reducing current consumption during the off period, as the second calculation means consumes less power than the first calculation means.
2Use of energy by moving object
If the motor control device stops calculation during the period when the IG switch is off to reduce current consumption, then battery drainage is prevented, but the motor rotation angle detection becomes erroneous when the motor is rotated by external force
Solution Approach 1:
The patent segments the operational modes into two distinct calculation means with different functional scopes. The first calculation means handles comprehensive motor control tasks when powered, while the second calculation means maintains minimal rotation angle tracking when powered down. This segmentation enables the system to balance between energy conservation and detection accuracy by activating appropriate calculation modes based on ignition state.
Solution Approach 2:
The second calculation means performs preliminary rotation angle calculation in advance during the off period, maintaining basic angle tracking without full motor control functions. This preliminary action ensures that when the IG switch is turned on, the system has already captured the motor rotation angle information, allowing seamless continuation of accurate absolute position detection without requiring continuous high-power operation.
3Measurement precision
If two MR sensors are used to detect the absolute angle of a plurality of rotations of the steering angle, then the absolute position can be detected, but the cost increases and the detecting range is mechanically limited
Solution Approach 1:
The patent makes the motor rotation angle detection means serve multiple functions: it detects both the motor rotation angle for brushless motor control and the steering angle for absolute position detection. By utilizing the existing motor angle sensor (such as a resolver or encoder) already present in the motor control system, the patent eliminates the need for separate steering angle sensors, thereby reducing cost and device complexity while maintaining absolute position detection capability across multiple rotations.
Solution Approach 2:
The system uses its own internal motor rotation angle detection means to simultaneously provide motor control feedback and steering angle information. This self-service approach allows the motor control device to generate steering angle data from its own operational parameters, eliminating the need for external steering angle sensors and their associated alignment requirements, thus simplifying the overall system.
Data Source
AI summary
Provided is a motor control device including a main calculation unit (101), which takes a first operation state for controlling a brushless motor (5), and a second operation state for stopping the motor control, and a sub calculation unit (102) for monitoring the main calculation unit (101) by means of a first monitoring unit (106) in the first state, for calculating a motor rotation angle in the second state, thereby enabling continuous calculation of the motor rotation angle even when the motor control is stopped, for carrying out monitoring the sub calculation unit (102) by means of second monitoring unit (201), thereby securing reliability, and for calculating the motor rotation angle in a second calculation cycle in the second operation state, the second calculation cycle being longer than a first calculation cycle in the first operation state, thereby reducing a current consumption.