External Rotor Motor Actuator for Limited Angle Rotation
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Solution Overview
Problem
Conventional rotational motion electro-mechanical actuators (EMAs) with high gear ratios are slow, complex, and costly due to the need for precise gear trains and commutation, which limits their speed of response and efficiency in achieving limited angle actuation.
Innovation Solution
An actuator system utilizing an external rotor motor with a simple drive train comprising pins and links, which reduces the need for high gear ratios and eliminates the need for commutation by restricting the motor's rotation to less than 90 degrees, allowing for faster and more compact operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a high gear ratio is used to achieve limited angle actuation, then the desired range of motion is achieved, but the speed of response becomes slow
Solution Approach 1:
The patent changes the fundamental operating parameters by using an external rotor motor with limited angular travel (less than 90 degrees) instead of a conventional internal rotor motor. This parameter change eliminates the need for high gear ratios while maintaining the desired range of motion, thereby improving speed of response.
Solution Approach 2:
The patent inverts the conventional motor structure by using an external rotor motor instead of an internal rotor motor. This inversion allows the motor to operate with limited angular travel and eliminates the need for commutation, directly addressing the speed-response issue caused by high gear ratios.
2Productivity
If an internal rotor motor is used to minimize system inertia, then rotational motion is achieved, but the actuator becomes complex due to commutation requirements
Solution Approach 1:
The patent inverts the conventional motor structure by placing the rotor outside the stator, creating an external rotor motor. This inversion eliminates the need for commutation since the motor operates with limited angular travel, thereby reducing device complexity while maintaining rotational motion capability.
Solution Approach 2:
The patent extracts the commutation system from the motor design by using an external rotor configuration that operates without commutation. This extraction simplifies the actuator design by removing multiple wires and switches required for commutation control.
3Device complexity
If multiple rotations of the motor are required to achieve the desired range of motion, then the gear ratio is reduced, but the actuator length becomes excessive
Solution Approach 1:
The patent changes the motor's angular travel parameter to less than 90 degrees and uses an external rotor configuration, which eliminates the need for high gear ratios. This allows the actuator to achieve the desired range of motion in a compact length without excessive actuator length.
4Force
If an external rotor motor is used to provide greater torque, then the need for high gear ratios is reduced, but the motor travel is limited to less than 90 degrees
Solution Approach 1:
The patent changes the motor configuration to an external rotor design with limited angular travel (less than 90 degrees). This parameter change provides greater torque output, which compensates for the limited angular travel by eliminating the need for high gear ratios, thereby achieving the desired range of motion more efficiently.
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 external rotor motor design enhances speed and reduces complexity and cost by providing higher torque and eliminating the need for complex gear trains and commutation, resulting in a more efficient and compact actuator system for limited angle rotation.
Implementation Method 1
an external permanent magnet rotor having a set of poles configured to rotate less than 90 degrees around the stator
Implementation Method 2
a drive train connecting the external permanent magnet rotor to the drive shaft, and configured to allow transmission of a first component of rotational motion
Data Source
AI summary
The actuator system has a external rotor motor having: (i) an internal armature configured as a stator having a set of coils wrapped around a set of arms, and (ii) an external permanent magnet rotor having a set of poles configured to rotate less than 90 degrees around the stator. The actuator system has a drive shaft configured to be rotated by the external rotor motor. The actuator system has a drive train connecting the external permanent magnet rotor to the drive shaft, and configured to provide gear ratio to the drive shaft.