Electric Motor Rotor Position Sensing via Magnetic Flux Density
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Solution Overview
Problem
Existing electric motors with rotation angle sensors face challenges such as high costs, complex production, space constraints, and susceptibility to environmental conditions like condensation and dirt, limiting their application in harsh environments.
Innovation Solution
An electric motor design that generates analog rotor position signals by detecting the magnetic flux density of a sensor magnet, using digital and analog rotor position sensors arranged on a printed circuit board to produce high-resolution speed and direction determination signals, ensuring functionality under harsh conditions and simplifying production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical encoders are used to precisely determine speed and position, then measurement precision is improved, but device complexity and cost increase, and the motor requires more space
Solution Approach 1:
The patent replaces optical encoders with a magnetic sensor system that detects the magnetic field of a sensor magnet mounted on the rotor. This substitution eliminates the need for complex optical components and their attachment mechanisms, while maintaining high measurement precision for speed and position determination
Solution Approach 2:
The patent uses magnetic field distribution as a copy or representation of rotor position information. By detecting the magnetic flux density pattern generated by the sensor magnet, the system obtains precise position and speed data without requiring physical optical encoder components
2Measurement precision
If optical encoders are mounted on the shaft end, then measurement precision is improved, but the number of free shaft ends decreases, reducing adaptability
Solution Approach 1:
The patent transitions from mounting sensors on the shaft end (one-dimensional constraint) to integrating magnetic sensors on the stator core that detect the magnetic field in the air gap (three-dimensional space utilization). This allows both shaft ends to remain free while maintaining precise position determination
3Measurement precision
If optical encoders are used, then measurement precision is improved, but reliability decreases under harsh environmental conditions due to susceptibility to condensation and dirt
Solution Approach 1:
The patent replaces optical sensing components with magnetic field sensors that detect the magnetic flux density pattern. Since magnetic fields penetrate non-magnetic materials and are not affected by condensation or dirt, this substitution significantly improves reliability in harsh environmental conditions while maintaining measurement precision
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 design allows for compact, cost-effective, and reliable speed and direction determination, enabling precise control even at low speeds and in harsh environments, without the need for expensive optical encoders.
Implementation Method 1
analog rotor position signals of a specific form and phase position which are generated during operation by detecting the magnetic flux density of a sensor magnet (82) arranged on the motor shaft (87)
Data Source
Figure 1
Figure 2
Figure 3a~4b
AI summary
An electric motor has a stator and a rotor (14) which can rotate about a rotation axis (85). This has a sensor magnet (82) with an even number of sensor poles (71, 72, 73, 74). The sensor magnet (82) is designed to produce a magnetic flux with a magnetic flux density which has a sinusoidal profile over the rotation angle. Furthermore, at least two analogue rotor position sensors (460, 465) are provided in order to produce analogue rotor position signals (B_S1, B_S2) which characterize the magnetic flux density of the magnetic flux acting on the respective sensor (460, 465) from the sensor magnet (82). These analogue rotor position sensors (460, 465) are arranged in the area of the circumference of the sensor magnet (82) on a common planar mount arrangement (468), which is essentially parallel to the rotation axis (85) of the sensor magnet, where the mount arrangement (468) is intersected by a first plane (470) that is at right angles to the rotation axis (85). These analogue rotor position sensors (460, 465) are arranged at such a distance from one another on the mount arrangement (468) that they produce two sinusoidal signals (B_S1, B_S2) with a phase shift of 90° during operation. A signal generator (90) is used to produce at least one pulsed signal (A, B) from these two sinusoidal signals (B_S1, B_S2) which have been phase-shifted through 90°. The instantaneous rotation speed can be determined accurately from this pulsed signal.