Limited Rotation Rotary Actuator with Magnetic Spring Return
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Solution Overview
Problem
Conventional electromechanical rotary actuators have limited angular range and suffer from mechanical shock, non-linearity, and repeatability issues, making them unsuitable for applications requiring wide and precise rotation angles, especially in optical scanning where linear current-versus-angle characteristics and self-damping are necessary.
Innovation Solution
An electromechanical limited rotation rotary actuator design featuring a stator with arcuate teeth and a diametral magnetized rotor, providing a non-uniform gap for restoration torque and bidirectional torque control, enabling angular ranges exceeding +/-80 degrees with linear output-angle versus input-current characteristics and self-damping capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional electromechanical rotary actuators are used, then they can provide two discreet rotation angles, but they suffer from mechanical shock, limited angular range, and non-linearity
Solution Approach 1:
The patent replaces the traditional mechanical spring return mechanism with a magnetic field-based restoration system. The diametral magnetized rotor interacts with the stator teeth to create a magnetic spring effect that provides restoration torque without mechanical contact, eliminating mechanical shock while enabling wide angular ranges exceeding +/-80 degrees.
Solution Approach 2:
The patent changes the magnetic circuit parameters by using a non-uniform air gap between the rotor magnet and stator teeth. This non-uniform gap creates a magnetic spring constant that varies with rotor angle, providing linear current-versus-angle characteristics over a wide range while maintaining shock-free operation.
2Measurement precision
If open-loop control with spring-like return mechanism is used, then the shaft returns to nominal angle when no current is applied, but linearity depends on torque-versus-angle characteristics and hysteresis effects degrade repeatability
Solution Approach 1:
The patent substitutes the mechanical spring return mechanism with a magnetic field-based restoration system. The diametral magnetized rotor creates a magnetic spring effect that provides consistent restoration torque without mechanical contact, eliminating hysteresis effects and improving repeatability while maintaining system simplicity.
Solution Approach 2:
The patent optimizes the non-uniform air gap parameters to create a magnetic spring constant that varies with rotor angle in a controlled manner. This parameter optimization achieves linear current-versus-angle characteristics over a wide angular range, improving measurement precision without adding complexity.
3Measurement precision
If closed-loop control with angular position sensor is used, then speed, linearity and repeatability are greatly improved, but complexity and cost increase
Solution Approach 1:
The patent makes the actuator self-servicing by incorporating intrinsic magnetic spring characteristics that provide restoration torque and centering force. The non-uniform air gap design creates self-damping effects and linear current-versus-angle characteristics without requiring external sensors or complex control electronics, reducing system complexity while maintaining precision.
4Ease of operation
If metal spring return mechanism is used, then return-to-center action is provided, but angular range is limited to +/-25 degrees or less
Solution Approach 1:
The patent replaces the mechanical spring return mechanism with a magnetic field-based restoration system. The diametral magnetized rotor creates a magnetic spring effect that provides restoration torque without the angular range limitations of mechanical springs, enabling operation over +/-80 degrees or more while maintaining reliable return-to-center action.
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 actuator achieves a wide angular range with linear current-versus-angle control and self-damping, enhancing speed and repeatability, while being cost-effective and easy to assemble, addressing the limitations of existing actuators in optical scanning and other applications.
Implementation Method 1
A rotor has at least one diametral magnetized magnet bidirectionally operable with the stator and extending into the aperture, wherein a non-uniform gap is formed between the magnet and the arcuate end portions of the teeth, and wherein the shape of the gap provides a restoration torque resulting in a spring-like return-to-center action of the rotor
Implementation Method 2
An electrical coil extends around at least a portion of one tooth of the at least two teeth, wherein the electrical coil is excitable for magnetizing the tooth and providing bidirectional torque to the rotor
Data Source
AI summary
An electromechanical limited rotation rotary actuator comprises a stator having an aperture extending axially therein and at least two teeth having arcuate end portions forming an aperture. A rotor includes a diametral magnetized magnet bidirectionally operable with the stator and extending into the aperture. A non-uniform gap is formed between the magnet and the end portions of the teeth, and wherein the shape of the gap provides a restoration torque resulting in a spring-like return-to-center action of the rotor. An electrical coil extends around at least a portion of one tooth and is excitable for magnetizing the tooth and providing bidirectional torque to the rotor.