Hollow-Rotor Roller Screw Linear Drive for Real-Time Control
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Solution Overview
Problem
Current linear actuators in humanoid robots face challenges with poor real-time control performance, efficiency, reliability, and increased size due to brushed motors and multi-stage planetary gear structures, which also suffer from unbalanced three-phase resistance and torque issues.
Innovation Solution
A linear drive mechanism featuring a casing with openings, a stator, a hollow rotor, and a roller screw with a screw nut and center screw, enabling direct drive between the motor and motion mechanism, utilizing a magnet-conducting hollow shaft structure and Hall sensor chips for precise control, and a toothless groove structure for smooth operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brushed motors and multi-stage planetary gear structures are used, then the linear actuator can achieve force transmission, but the real-time control performance deteriorates due to significant hysteresis after multiple stages of reduction
Solution Approach 1:
The patent removes the planetary gear reduction stage from the transmission system, achieving direct drive between the motor and screw mechanism. This extraction of the intermediate reduction stage eliminates the hysteresis and complexity associated with multi-stage gearing while maintaining force transmission capability through the direct motor-screw connection.
2Force
If the number of stages in the transmission is increased, then the force transmission capability is improved, but the efficiency decreases rapidly
Solution Approach 1:
The patent replaces the mechanical planetary gear reduction system with a direct-drive screw mechanism. This substitution eliminates the energy losses inherent in multiple mechanical reduction stages while maintaining adequate force transmission through the motor's direct connection to the screw, achieving both force capability and efficiency.
3Reliability
If brushed motors are used, then the linear actuator can operate, but reliability issues occur due to unbalanced three-phase resistance and torque from contact problems with brushes
Solution Approach 1:
The patent eliminates the brushed motor's mechanical brush contact system by采用ing a brushless motor design. This substitution removes the source of unbalanced three-phase resistance and torque issues caused by brush wear and contact problems, significantly improving operational reliability through contactless commutation.
4Reliability
If a casing is set up to constrain the motor stator and nut into an integral structure, then system safety is improved, but the overall size of the linear actuator increases
Solution Approach 1:
The patent merges the motor stator and nut into an integral casing structure, combining two separate components into a unified housing. This merging provides structural support and safety constraints for both components while optimizing space utilization, preventing the overall size from increasing proportionally to what would be expected from separate housings.
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 mechanism achieves high efficiency, reliable control, and compact size with reduced mounting space, while eliminating brush friction and simplifying assembly, thus enhancing system reliability and responsiveness.
Implementation Method 1
a stator arranged in the casing; a hollow rotor arranged in the stator and rotatably connected to the stator
Implementation Method 2
a roller screw arranged in the rotor, comprising: a screw nut fixed in the rotor and a center screw arranged on an inner peripheral side of the screw nut
Data Source
AI summary
The present application provides a linear drive mechanism, including a casing with openings at both ends, a front cover and a rear cover fixed at opposite ends of the casing, a stator arranged in the casing, a hollow rotor arranged in the stator and rotatably connected to the stator, a roller screw arranged in the rotor. The roller screw includes a screw nut fixed in the rotor and a center screw arranged on an inner peripheral side of the screw nut and arranged through the front cover, and the screw nut is rotatably connected to the center screw. The stator drives the rotor to rotate the screw nut, to drive the center screw to perform a linear telescopic motion. The linear drive mechanism of the present application has a good linear drive effect, good real-time controllability, high efficiency of multi-stage transmission, high reliability, and saves mounting space.