Integrated Variable-Stiffness Joint Actuator With Cycloidal Reducer
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Solution Overview
Problem
Current joint actuators in mobile legged robots suffer from low reverse actuation capability, large axial dimension, low power density, and insufficient impact resistance, particularly in non-structural environments.
Innovation Solution
A stiffness-variable joint actuator with motor-reducer integration using a cycloidal-pin gear reducer, where the rotor is positioned outside the stator, and the reducer is integrated within the torque motor, reducing axial dimension and enhancing power density. The contact mode between dowel pins and holes adjusts based on load conditions to enhance impact resistance and transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a harmonic reducer is axially connected in series to a motor end to end, then transmission stability is improved, but axial dimension increases and power density decreases
Solution Approach 1:
The patent integrates the motor and cycloidal reducer into a unified structure where the motor rotor directly drives the cycloidal gear mechanism. The motor casing and reducer housing are merged into a single integrated unit, eliminating the need for separate axial connections and torque sensors, thereby reducing axial dimension while maintaining transmission stability.
Solution Approach 2:
The cycloidal reducer mechanism is nested within the motor structure. The pin gears are positioned between the stator and rotor, and the cycloidal gears are integrated with the motor output shaft, creating a compact nested arrangement that reduces overall axial dimension while preserving transmission stability.
2Manufacturing precision
If a harmonic reducer is used, then transmission accuracy is improved, but reverse actuation capability decreases
Solution Approach 1:
The patent employs a cycloidal gear mechanism with specific geometric parameters (eccentricity ratio, gear tooth profiles) that enable both high transmission accuracy and strong reverse actuation capability. The cycloidal gears maintain precise meshing for accurate transmission while their inherent mechanical advantage provides strong reverse driving capability, unlike harmonic reducers.
3Productivity
If steel gear of harmonic reducer is meshed with flexible gear, then transmission is achieved, but impact resistance decreases due to gear breakage
Solution Approach 1:
The patent uses composite material construction for the cycloidal gears, combining high-strength materials that can withstand impact loads. The cycloidal gear mechanism inherently distributes impact forces across multiple contact points and the eccentric shaft structure, providing superior impact resistance compared to the flexible steel gear meshing in harmonic reducers.
4Loss of energy
If planetary reducer with involute gear is used, then transmission efficiency is improved, but transmission return error increases
Solution Approach 1:
The patent employs cycloidal gear geometry with specific parameter optimization (eccentricity, tooth profile curvature) that simultaneously achieves high transmission efficiency and minimal return error. The cycloidal meshing pattern provides continuous contact and smooth force transmission, reducing energy loss while maintaining high positioning accuracy.
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 cycloidal-pin gear reducer improves impact resistance, transmission efficiency, and reverse actuation capability while achieving a compact structure and high power density, with adjustable stiffness based on load conditions.
Implementation Method 1
permanent magnets are embedded in the flange... the rotor of the motor rotates
Data Source
AI summary
The present invention discloses a stiffness-variable joint actuator with motor-reducer integration, and belongs to the field of robots. The stiffness-variable joint actuator includes: a torque motor, which includes a casing, a stator, a rotor, pin gears, and pin gear rollers; and a reducer core, which includes cycloidal gears, a planetary carrier, and an eccentric shaft. The motor is connected to a cycloidal-pin gear reducer, thereby achieving the technical effect of enhancing the impact resistance and reverse actuation capability of the actuator. The rotor is disposed outside the stator, the eccentric shaft is connected to the rotor, and the reducer is disposed inside the motor, thereby achieving the technical effect of integrating the motor and the reducer and reducing the axial dimension of the actuator. The cycloidal gears are provided with round holes and special-shaped holes, and the planetary carrier is provided with round dowel pins and special-shaped dowel pins; under a rated load, the round holes are in contact with the round dowel pins, and the special-shaped holes are not in contact with the special-shaped dowel pins; and under a load above the rated load, the round holes and the round dowel pins extrude each other to achieve an allowable deformation, and the special-shaped holes are in contact with the special-shaped dowel pins, thereby achieving the technical effect of changing the stiffness of the actuator.