Motor Actuator Backdrivability with High-Efficiency Speed Reduction
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Solution Overview
Problem
Existing actuators with motors and speed reducers face challenges in improving overall backdrivability, particularly due to high friction in the transmission path of the speed reducer and the influence of cogging torque from the motor.
Innovation Solution
The actuator combines a high-efficiency speed reducer with an efficiency of 60% or more and a motor with suppressed cogging torque, achieved through control unit management, to enhance overall backdrivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a speed reducer with high reduction ratio is used to reduce motor speed, then the motor can operate at lower speeds, but the friction in the transmission path increases and backdrivability deteriorates
Solution Approach 1:
The patent changes the efficiency parameter of the speed reducer to 60% or more, which is a significant improvement over conventional speed reducers. This parameter change directly addresses the friction issue by selecting a speed reducer type (such as harmonic drive or strain wave gear) that inherently has lower friction and higher efficiency, thereby improving backdrivability while maintaining the speed reduction function
Solution Approach 2:
The patent converts the harmful effect of friction into a benefit by carefully selecting a speed reducer mechanism where the friction characteristics are optimized. The high-efficiency speed reducer transforms what would normally be energy loss into acceptable operating conditions, allowing the system to achieve both speed reduction and good backdrivability
2Power
If conventional speed reducers are used, then speed reduction is achieved, but the overall backdrivability of the actuator including the motor is insufficient
Solution Approach 1:
The patent merges the motor and high-efficiency speed reducer into an integrated actuator system where the two components work synergistically. The control unit coordinates the motor operation with the speed reducer characteristics, creating a unified system that achieves both power transmission and excellent backdrivability, rather than treating them as separate functional elements
Solution Approach 2:
The patent applies parameter changes to both the mechanical system (speed reducer efficiency ≥60%) and the control system (cogging torque suppression control) to simultaneously improve power transmission and backdrivability. The control parameters are adjusted to compensate for the speed reduction ratio, maintaining optimal performance across the entire actuator system
3Force
If motor cogging torque is not suppressed, then the motor generates necessary torque, but the backdrivability is reduced due to cogging torque effects
Solution Approach 1:
The patent applies dynamic control to suppress cogging torque by continuously adjusting the motor current and control parameters based on the rotor position and operating conditions. This dynamic approach allows the motor to generate necessary torque when needed while minimizing cogging effects during backdriving, creating adaptive performance that responds to real-time operational requirements
Solution Approach 2:
The control unit implements feedback control to monitor and suppress cogging torque effects. By detecting the rotor position and current state, the control system adjusts the motor commands to counteract cogging forces, ensuring smooth backdrivability while maintaining the ability to generate torque when required for actuation
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 actuator (100) includes a control unit (80) that performs control to suppress a cogging torque of the motor (40).