Rotary Actuator Stator Teeth for Low Inductance
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Solution Overview
Problem
Existing electromechanical rotary actuators face challenges in achieving high torque constant with low coil resistance and low coil inductance, leading to heat generation issues and cogging torque problems in optical scanning applications.
Innovation Solution
The design incorporates a stator with slots and restoring magnets or contoured cavities to provide bidirectional torque and rotor position restoration, allowing for a two-pole or four-pole rotor magnet configuration with coils placed around teeth, which reduces inductance and enhances thermal dissipation while maintaining torque constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a toothless stator design with a solid cylindrical magnet is used, then the actuator achieves smooth rotation and low cogging torque, but the coil inductance becomes high and heat dissipation is poor
Solution Approach 1:
The stator is segmented into multiple teeth instead of being a smooth tube, creating discrete magnetic paths that reduce coil inductance and improve heat dissipation through the tooth structure while maintaining smooth rotation through proper pole configuration
Solution Approach 2:
The stator teeth are designed with specific local magnetic properties and geometries to concentrate flux in certain areas while providing thermal pathways, creating localized quality variations that simultaneously address magnetic performance and thermal management
2Volume of moving object
If the coil occupies a small space and is bonded to the inside of the stator tube, then the actuator achieves compact size, but heat generated by the coil cannot be removed effectively
Solution Approach 1:
Heat dissipation is enhanced by utilizing the radial dimension through stator teeth that conduct heat from the coil to the outer stator surface, adding a thermal conduction pathway in the radial direction while maintaining compact axial and radial dimensions
3Temperature
If a toothed stator arrangement is used, then heat dissipation is improved, but the coil inductance becomes greatly increased
Solution Approach 1:
The tooth geometry parameters (width, height, spacing) are optimized to balance magnetic circuit reluctance and coil inductance while maintaining effective heat dissipation pathways, achieving a parameter set that satisfies both thermal and electromagnetic performance requirements
4Object-generated harmful factors
If the gap between stator teeth is increased to reduce inductance, then the cogging torque increases significantly
Solution Approach 1:
The tooth and pole configurations are designed with asymmetric geometries and non-uniform spacing patterns that reduce cogging torque through magnetic field symmetry cancellation while maintaining adequate gap dimensions for low inductance
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 configuration achieves a balance of high torque constant, low coil resistance, and reduced inductance, effectively addressing heat generation and cogging torque issues, resulting in improved performance and reliability for optical scanning applications.
Implementation Method 1
At least one electrical coil may extend around at least a portion of one tooth of the at least two teeth, wherein the electrical coil is excitable for providing bidirectional torque to the rotor
Implementation Method 2
When the coil is energized, a Lorentz Force is imposed on both the coil and the magnet
Implementation Method 3
The rotor restoring means is positioned for restoring the rotor to a central rotation angle when current is withheld to the at least one electrical coil
Data Source
AI summary
An electromechanical rotary actuator includes a rotor and a stator having one or more slots into which one or more coils are placed. The stator includes a rotor position restoring means which overcomes cogging outside a desired rotation range. The rotor position restoration means may include one or more restoring magnets or optionally include a contoured cavity within the stator proximate the rotor. One stator includes teeth having contoured ends forming a portion of the aperture within which the rotor operates. Distal ends of the teeth form a relatively large gap compared to typical actuators, wherein the gap is sized to the rotor magnet. An actuator desirably having a high torque constant, low coil resistance and a low coil inductance is provided.