Fractional-Slot Brushless Motor Coils for High Slot Fill
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Solution Overview
Problem
Existing robot motors face challenges in achieving high torque capability and slot fill factor, which limits their per mass motor constant and output power density, due to constraints in winding processes and stator design.
Innovation Solution
A fractional-slot and inrunner type permanent magnet brushless motor with a concentrated stator winding and preset winding coils, where each stator tooth is inserted into multiple winding coils, allowing for improved slot fill factor and electromagnetic design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stator tooth with pole shoes is used to ensure low cogging torque and smooth operation, then the motor operates smoothly with low cogging torque, but the slot fill factor is limited due to constraints in winding process
Solution Approach 1:
The patent divides the stator core into multiple independent stator teeth without pole shoes, allowing each tooth to be independently wound. This segmentation enables the winding process to access each tooth separately, significantly improving the slot fill factor while maintaining smooth operation and low cogging torque through proper magnetic tooth design
Solution Approach 2:
The patent removes the pole shoes from the stator tooth structure. By taking out the pole shoes, the winding process is no longer constrained by the pole shoe geometry, allowing for much higher slot fill factors. The magnetic teeth are designed independently to provide the necessary magnetic path while enabling improved winding access
2Ease of manufacture
If a dedicated winding machine and specific winding process are used for each stator tooth, then the winding can be completed, but the slot fill factor is seriously limited
Solution Approach 1:
The patent segments the winding process into independent operations for each stator tooth. By dividing the stator into multiple accessible teeth without pole shoes, the winding machine can efficiently wind each tooth independently, achieving high slot fill factors while maintaining manufacturing ease through standardized repeated operations
Solution Approach 2:
Instead of having the winding process adapt to the pole shoe structure (traditional approach), the patent inverts the approach by designing the stator teeth specifically to accommodate the winding process requirements. The teeth are shaped and positioned to enable optimal winding access and fill factor, rather than conforming to pole shoe geometry
3Force
If high-speed and low-torque design with high reduction ratio is adopted to reach high actuator torque output, then the actuator torque output is achieved, but the per mass motor constant and output power density are limited
Solution Approach 1:
The patent changes the fundamental motor design parameters by adopting fractional-slot concentrated winding topology and eliminating pole shoes. These parameter changes enable higher slot fill factors and improved electromagnetic loading, allowing the motor to achieve high torque density and power density without relying on high reduction ratios, thereby improving per mass motor constant
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 solution significantly enhances the slot fill factor, leading to improved per mass motor constant and output power density, while ensuring smooth operation and low cogging torque.
Implementation Method 1
The rotor includes permanent magnet and a permanent magnet carrier, wherein the permanent magnet produces rotating excitation field
Data Source
AI summary
A permanent magnet brushless motor, robot joint, a servo actuator, and a robot are provided. The motor is of fractional-slot and inrunner type, including a stator (1) and a rotor (2). The stator (1) includes a stator iron core (10) and a stator winding, the stator winding is a concentrated winding, and the stator iron core (10) has an integral structure. The stator iron core includes a stator yoke and stator teeth, the stator teeth include a plurality of stator teeth (102) protruding from the stator yoke, and the surfaces of the stator teeth (102) are provided with insulating layers. The stator winding comprises a plurality of preset winding coils (11) formed by machine, and each stator tooth is inserted into x winding coils, wherein x is greater than or equal to 1. The rotor (2) comprises a permanent magnet (21) and a permanent magnet carrier (22). The embodiments of the present disclosure can improve a slot fill factor, and optimize an electromagnetic design while ensuring the smooth operation of the meter, thereby improving a per mass motor constant and output power density of the motor.