Rotational Angle Sensor Power Management for EPS
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Solution Overview
Problem
Conventional electric power steering systems with intermittent power supply to angle sensors face erroneous counting of motor rotations and increased power consumption, especially when trying to avoid erroneous counting by increasing the frequency of power supply.
Innovation Solution
A rotational angle detecting device that continues operation using battery power when the ignition switch is off, with a sensor and calculators that differentiate between necessary and unnecessary calculations, reducing power consumption by stopping unnecessary calculations and maintaining necessary ones even when the switch is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If electric power is intermittently supplied to the angle sensor from the battery, then electric consumption is reduced, but erroneous counting of the number of rotations of the electric motor may occur
Solution Approach 1:
The patent segments the calculation functions into two distinct calculators: a first calculator that operates only when the ignition switch is on, and a second calculator that operates continuously regardless of the ignition switch state. This segmentation allows the system to maintain reliable rotation counting through the second calculator while reducing overall power consumption by limiting the first calculator's operation to only when necessary.
Solution Approach 2:
The patent implements dynamic power management by allowing the angle sensor to transition between different operational states based on the ignition switch state. When the ignition switch is off, the sensor continues essential functions (second calculator) with reduced power consumption, and when the ignition switch is on, full functionality is restored. This dynamic adaptation resolves the contradiction between power savings and measurement reliability.
2Reliability
If a frequency of the intermittent power supply is increased to avoid the erroneous counting, then the accuracy of rotation counting is improved, but the electric consumption would be rather increased
Solution Approach 1:
The patent extracts the essential rotation counting function from the full angle sensor operation and places it in the second calculator, which operates continuously with minimal power consumption. The first calculator handles additional computational tasks only when the ignition switch is on. This extraction allows the system to maintain accurate rotation counting without requiring frequent high-power intermittent supply.
3Reliability
If electric power is continuously supplied to the angle sensor, then the accuracy of rotation counting is maintained, but electric consumption is increased
Solution Approach 1:
The patent applies local quality by giving different operational characteristics to different parts of the angle sensor. The second calculator maintains continuous operation with high reliability for essential rotation counting, while the first calculator operates intermittently with lower power consumption for additional calculations. This differentiated approach allows the system to maintain necessary accuracy while reducing overall power consumption compared to continuous full-operation supply.
Data Source
AI summary
A rotational angle detecting device continues a portion of operation by electric power from a battery when an electric switch is off. The rotational angle detecting device includes a sensor, a first calculator, a second calculator and a communication portion. The sensor detects a detection value that is variable according to a rotation of a detection object. The first calculator starts calculating first rotational information associated with the rotation of the detection object based on the detection value when the electric switch is turned on. The first calculator stops calculating the first rotational information when the electric switch is turned off. The second calculator calculates second rotational information associated with the rotation of the detection object regardless of an on/off state of the electric switch, based on the detection value. The communication portion outputs the first rotational information and the second rotational information to a controller.