Rotational Position Detection for AC Servomotor Using Magnetic Pole Edge
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Solution Overview
Problem
Existing methods for detecting the rotational position of an AC servomotor require expensive high-resolution components and significant space, making them costly and difficult to implement in compact motor designs.
Innovation Solution
A method that detects the magnetic pole position of a three-phase AC servomotor using a low-resolution structural component, generating a three-phase square wave signal with a 120-degree phase difference, and computing rotational speed and position based on edge detection, allowing for high-resolution position estimation with minimal space and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If incremental-type encoders or absolute-type encoders are used to detect rotational position with predetermined resolution, then measurement precision is improved, but device complexity and cost increase due to requiring optical or magnetic detectors, encoder plates, and significant installation space
Solution Approach 1:
The patent extracts only the essential function of rotational position detection by removing complex optical/magnetic detector assemblies and encoder plates. It uses a simplified approach where a single sensor detects magnetic pole positions to generate square wave signals, extracting the core detection capability while eliminating unnecessary complexity.
Solution Approach 2:
The patent replaces expensive, high-precision encoder components with inexpensive, low-resolution structural components. A simple magnetic sensor and basic signal processing circuitry substitute for costly optical encoders, achieving acceptable detection resolution at significantly reduced cost and complexity.
2Measurement precision
If high-precision encoder plates and optical or magnetic detectors are installed to ensure predetermined resolution, then measurement precision is improved, but the installation space requirement increases, making it difficult to build encoders into flat motors with short shaft lengths
Solution Approach 1:
The patent removes the bulky optical or magnetic detector assemblies and encoder plates that occupy significant space. By extracting only the essential detection function and implementing it through a compact magnetic sensor system, the installation footprint is dramatically reduced for flat motor applications.
Solution Approach 2:
The patent uses compact, low-cost magnetic sensors and simple signal processing circuits that require minimal installation space, replacing the space-intensive optical encoder assemblies. This enables encoder integration into flat motors with short shaft lengths where space is constrained.
3Measurement precision
If optical or magnetic detectors and high-precision encoder plates are used to achieve predetermined resolution, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive optical encoders, magnetic detectors, and precision encoder plates with inexpensive magnetic sensors and simple signal processing circuits. This substitution dramatically reduces component costs while maintaining adequate detection resolution for the application.
Solution Approach 2:
The patent extracts the essential detection function from complex, expensive encoder systems and implements it through minimal components. By removing unnecessary complexity and using only the essential magnetic field detection capability, manufacturing costs are significantly reduced.
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
Enables accurate detection of the rotational position with high resolution using a low-cost, space-efficient mechanism, reducing the need for expensive encoder plates and allowing for compact installations.
Implementation Method 1
detecting the magnetic pole position of each phase of a three-phase AC servomotor... The detection signal of the magnetic pole position of each phase of the AC servo motor can be directly obtained from the magnet rotor provided to the AC servo motor and a Hall element, MR element, or other magnetic sensor for detecting a magnetic pole
Data Source
AI summary
A motor rotational position detecting method detects the magnetic pole position of each phase of a three-phase AC servomotor, generates a three-phase square wave signal having a phase difference of 120 degrees, allocates data on the rotational position of a motor shaft to the edge of each square wave signal, calculates the rotational speed of the motor on the basis of the elapsed time from the previous edge detection point to this time edge detection point, and estimates the rotational position of the motor shaft at a certain period and outputs it on the basis of the rotational speed of the motor and the rotational position allocated to this time edge in the rotational section from this time edge detection point to the next edge detection point. As a result, a detection mechanism can be constructed with a small installation space and at low cost and the output of a high-resolution encoder can be obtained in a pseudo manner.