DC Motor Rotation Estimation Using Induced Current Integration
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Solution Overview
Problem
Conventional methods for estimating the rotation amount of a brushed DC motor are inaccurate, especially at low speeds and during motor startup, due to difficulties in measuring back electromotive force and pulse cycle detection.
Innovation Solution
The proposed solution involves estimating the rotation amount by integrating an induced current flowing through the DC motor based on a convergence characteristic curve of the motor current, rather than relying on back electromotive force, to improve estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If back electromotive force measurement is used for rotation amount estimation, then estimation can be performed during motor operation, but measurement accuracy deteriorates at low speeds and during startup
Solution Approach 1:
The patent changes the measurement parameter from back electromotive force to motor current. By measuring motor current instead of back electromotive force, the system achieves accurate rotation amount estimation across all speed ranges including low speeds and startup conditions where back electromotive force measurement fails.
2Reliability
If pulse cycle detection is used for rotation amount estimation, then rotation speed can be measured, but detection reliability deteriorates at low speeds
Solution Approach 1:
The patent replaces the mechanical pulse cycle detection system with an electrical measurement system based on motor current. This substitution eliminates the speed-dependent limitations of pulse detection, providing reliable rotation amount estimation from zero speed onwards.
3Measurement precision
If conventional rotation detection methods are used, then system complexity remains low, but measurement precision deteriorates during motor startup
Solution Approach 1:
The patent makes the motor current measurement serve multiple functions: it is used for both motor control and rotation amount estimation. This multi-functionality improves measurement precision during startup without requiring additional detection hardware or increasing system complexity.
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
This method enables precise estimation of the rotation amount of the DC motor, even at low speeds and during startup, leading to improved control of the motor and preventing errors in anti-pinch control systems.
Implementation Method 1
difficulties in measuring back electromotive force
Implementation Method 2
calculate an integral value obtained by integrating an induced current flowing through the DC motor corresponding to rotation of the DC motor
Data Source
AI summary
A rotation amount estimation device estimates, based on a motor current, a convergence characteristic curve in a period from when a DC voltage applied to the DC motor changes to when a rotation speed of the DC motor is regarded as having reached a corresponding speed corresponding to the changed DC voltage, calculates an integral value of an induced current in the DC motor corresponding to rotation of the DC motor over the period based on the convergence characteristic curve, and estimates a rotation amount of the DC motor in the period based on the integral value.