Low-Cogging Actuator With High-Backdrivability Speed Reduction
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Solution Overview
Problem
Existing actuators with integrated motors and speed reducers face challenges in achieving high backdrivability due to significant friction in the transmission path and unbalanced backdrivability, particularly influenced by cogging torque from the motor.
Innovation Solution
The actuator combines a low-cogging motor with a high-efficiency speed reducer, where the cogging torque multiplication by the reduction ratio is equal to or less than the output starting torque of the speed reducer, and incorporates a control unit to further suppress cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional motor and speed reducer are combined in an actuator, then the actuator can reduce rotation speed, but the backdrivability deteriorates due to friction and cogging torque
Solution Approach 1:
The patent applies parameter changes by specifying that the speed reducer must have an efficiency of 60% or more and the motor must be a low-cogging motor where the multiplication of cogging torque and reduction ratio is equal to or less than the output starting torque of the speed reducer. These parameter specifications directly address the backdrivability issue while maintaining speed reduction functionality.
2Force
If the reduction ratio of the speed reducer is increased, then the output torque is amplified, but the cogging torque multiplication worsens the backdrivability
Solution Approach 1:
The patent resolves this contradiction by establishing a specific parameter relationship: the multiplication of cogging torque and reduction ratio must be equal to or less than the output starting torque of the speed reducer. This parameter constraint ensures that even with high reduction ratios that amplify output torque, the cogging torque effects remain within acceptable limits for maintaining backdrivability.
3Loss of energy
If the efficiency of the speed reducer is improved, then the transmission loss is reduced, but the overall backdrivability remains limited by motor cogging torque
Solution Approach 1:
The patent addresses this by imposing dual parameter requirements: the speed reducer efficiency must be 60% or more, and simultaneously the motor must satisfy the condition that cogging torque multiplied by reduction ratio is equal to or less than the output starting torque. This combination of parameter changes ensures both low transmission loss and acceptable overall backdrivability.
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 significantly improves the overall backdrivability of the actuator, reducing friction and enhancing the ease with which external forces are transmitted, thereby achieving better control accuracy.
Implementation Method 1
a speed reducer that reduces rotation of the motor. The speed reducer has an efficiency of 60% or more
Implementation Method 2
the motor is a low-cogging motor in which a multiplication of a cogging torque and a reduction ratio is equal to or less than an output starting torque of the speed reducer
Data Source
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AI summary
An object of the present invention is to provide an actuator (100) capable of improving overall backdrivability including a motor (40). An actuator (100) includes: a motor (40); and a speed reducer (10) that reduces rotation of the motor (40), in which the speed reducer (10) has an efficiency of 60% or more, and the motor (40) is a low-cogging motor in which a multiplication of a cogging torque and a reduction ratio is equal to or less than an output starting torque of the speed reducer (10).