Slotless Motor Sensor Ring for Accurate Rotor Positioning
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Solution Overview
Problem
Challenges exist in accurately positioning the rotor in slotless motors due to the lack of stator teeth, which complicates the placement of rotor position sensors, leading to imprecise motor control and reduced efficiency.
Innovation Solution
A rotor position sensing element is introduced, comprising a sensor ring and attachment that is fixed relative to the coil windings, allowing precise positioning by determining the reference point for the rotor's orientation relative to the coil blocks, using sensors like hall-effect or magnetostrictive position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a rotor position sensor is placed in a slotless motor without stator teeth, then the motor can achieve slotless construction with reduced cogging torque, but the sensor positioning becomes complex and measurement precision deteriorates
Solution Approach 1:
The patent introduces a sensor ring as an intermediary component between the sensor and the rotor. This sensor ring provides a stable reference frame for the sensor, enabling accurate rotor position measurement without requiring stator teeth. The sensor ring acts as a mediator that decouples the sensor positioning requirement from the stator structure, allowing slotless motor construction while maintaining measurement precision.
Solution Approach 2:
The patent segments the sensor system into distinct components: the sensor itself, the sensor ring, and the attachment mechanism. This segmentation allows each component to be optimized independently - the sensor ring can be precisely positioned relative to the rotor while the sensor can be mounted on the stator, resolving the positioning complexity issue.
2Measurement precision
If a rotor position sensor is placed on or between stator teeth in a slotted motor, then accurate rotor position readings are achieved, but the motor structure becomes complex with slots and teeth
Solution Approach 1:
The patent extracts the tooth structure from the stator, creating a slotless motor design. The positioning function previously provided by stator teeth is transferred to a separate sensor ring component. This extraction eliminates the complexity of slotted construction while maintaining the ability to provide accurate rotor position readings through the alternative sensor ring reference system.
3Measurement precision
If tight tolerances are applied to stator, rotor and motor housing for high precision sensor readings, then measurement precision improves, but manufacturing cost and complexity increase
Solution Approach 1:
The patent introduces a new dimensional reference system using the sensor ring that is independent of the stator-rotor-housing assembly tolerances. By creating a separate reference frame on the sensor ring, the system achieves high measurement precision without requiring tight tolerances on the mechanical components. The sensor ring serves as a stable reference that decouples measurement accuracy from manufacturing tolerances.
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
Enhances motor control precision and efficiency by providing accurate rotor position readings, reducing interference from component tolerances and enabling precise torque generation.
Implementation Method 1
using sensors like hall-effect or magnetostrictive position sensors
Implementation Method 2
using sensors like hall-effect or magnetostrictive position sensors
Implementation Method 3
the order that each phase winding is energised generates a torque in the rotor due to the interaction between the magnetic field generated in the coils and the permanent magnets on the rotor
Data Source
AI summary
The present invention relates to a slotless motor comprising a rotor position sensing element. The motor has a rotor having a rotational axis and a plurality of coil windings arranged into an integer N number of distinct blocks, each block being arranged about the rotational axis and having a gap between each adjacent pair of blocks. The rotor position element has a sensor ring having a sensor fixed to the sensor ring and a sensor ring attachment extending from the sensor ring wherein the sensors are spaced around the rotational axis and wherein the rotor position sensing element is configured to hold the sensor ring relative to at least one of the blocks such that the sensor is held in a predetermined position.