Motor Rotation Angle Detection Using Ripple and Back-EMF Correction
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Solution Overview
Problem
Existing motor rotation angle detection methods, such as those using ripple components, face challenges in accuracy when the motor is rotating by inertia or when noise leads to erroneous pulse signal generation, resulting in unreliable rotation amount calculations.
Innovation Solution
A motor module with a rotation angle detector that includes a commutator and a signal generator system, which corrects rotation angle calculations based on both ripple component signals and inter-terminal voltage, ignoring subsequent ripple component signals within a predetermined angle range to prevent errors and ensure accurate rotation angle detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse signals are generated based on ripple component frequency, then rotation amount can be obtained with certain accuracy at constant rotational angular velocity, but accuracy deteriorates when the motor is rotating by inertia and the ripple component becomes small
Solution Approach 1:
The patent introduces an intermediary correction mechanism that uses counter electromotive voltage integration as a mediator to correct the pulse signal count. When the ripple component becomes small during inertial rotation, the correction unit uses the integral of counter electromotive voltage to calculate the actual rotation amount, thereby maintaining detection accuracy without being affected by the weakened ripple signal.
Solution Approach 2:
The patent implements a feedback mechanism where the detection result is continuously corrected based on the comparison between actual integral values and average integral values. The correction unit receives feedback about detection accuracy and adjusts the pulse signal count accordingly, ensuring reliable rotation amount detection even when the original detection method becomes less accurate during inertial rotation.
2Measurement precision
If the apparatus corrects pulse signal count based on integral comparison, then rotation amount accuracy improves, but the apparatus cannot increment pulse signals until a sufficient time period passes indicating motor stop
Solution Approach 1:
The patent applies preliminary action by continuously calculating and storing the integral of counter electromotive voltage during motor operation. This preliminary calculation is performed in advance so that when correction is needed, the data is already prepared and can be immediately used for accurate rotation amount calculation without waiting for a time period to pass.
Solution Approach 2:
The patent makes the correction mechanism dynamic by continuously monitoring the relationship between actual and average integral values during motor operation. The system dynamically adjusts the pulse signal count based on real-time integral comparisons, allowing accurate rotation amount detection to be obtained at appropriate timing rather than waiting for a fixed time period after motor stop.
3Productivity
If multiple pulse signals are generated based on ripple components, then rotation information can be calculated, but noise may cause erroneous pulse signal generation leading to unreliable rotation amount
Solution Approach 1:
The patent uses feedback to verify the validity of generated pulse signals. By continuously comparing the actual integral of counter electromotive voltage with the average integral, the system can identify and correct erroneous pulse signals caused by noise, thereby maintaining reliable rotation amount calculation while preserving efficient rotation information processing.
Solution Approach 2:
The patent converts the harmful effect of noise into a beneficial correction opportunity. When noise causes erroneous pulse generation, the integral comparison mechanism detects the discrepancy and corrects it, thereby transforming potential errors into verified accurate measurements. The correction unit uses the integral data to identify and fix noise-induced errors, improving overall reliability.
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 maintains accurate rotation angle detection even during inertial rotation and reduces errors caused by noise, ensuring reliable rotation information without the need for additional sensors, thus enhancing the motor's operational reliability.
Implementation Method 1
calculates the rotation angle based on an inter-terminal voltage between terminals of the motor and an electric current flowing through the motor
Implementation Method 2
generates a first signal based on a ripple component included in the electric current flowing through the motor
Data Source
AI summary
A motor module includes a motor and a rotation angle detector including a rotation angle calculator that calculates a rotation angle based on a voltage and an electric current of the motor, a first signal generator that generates a first signal based on a ripple component included in the electric current, an operation part that corrects the rotation angle based on the first signal and the rotation angle, and a rotation information calculator that calculates information on rotation of the motor based on an output from the operation part. The operation part outputs, to the rotation angle calculator, a command to correct the rotation angle when the first signal is generated for the first time while the rotation angle is within a predetermined angle range, and ignores the first signal that is generated for the second or subsequent time while the rotation angle is within the predetermined angle range.