Linear actuator for motion simulator
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Solution Overview
Problem
Existing linear actuators used in motion simulators struggle to provide low to medium amplitude outputs at low or medium frequencies for a high number of strokes while supporting the weight of a platform and its occupants, with limited efficiency in translating rotational motion into linear motion effectively.
Innovation Solution
A linear actuator design featuring a motor with a bi-directional rotational output, a casing with an inner cavity and a shaft, a sliding tube, and a travelling nut, where the liner has C-shaped cross-section with longitudinal contact surfaces and grooves to apply biasing force and reduce friction, along with a taper-lock arrangement and anti-rotation features to enhance the conversion of rotational motion into linear motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional linear actuators are used to support platform weight and provide motion, then load capacity is maintained, but motion conversion efficiency and stroke performance deteriorate
Solution Approach 1:
The actuator is divided into distinct functional segments: a motor assembly for rotational motion generation, a ball screw mechanism for motion conversion, and a piston-cylinder assembly for linear output. This segmentation allows each component to be optimized independently, improving overall motion conversion efficiency while maintaining reliability through specialized design of each subsystem.
Solution Approach 2:
A ball screw mechanism serves as an intermediary between the motor's rotational output and the piston's linear motion. This intermediate conversion mechanism efficiently translates rotational motion into precise linear displacement, significantly improving motion conversion efficiency while the piston-cylinder assembly maintains reliable stroke performance under load.
2Productivity
If linear actuators provide low to medium amplitude outputs at low or medium frequencies, then motion simulation quality improves, but the ability to maintain high stroke performance deteriorates
Solution Approach 1:
The actuator employs a dynamic piston-cylinder assembly with optimized mass distribution and balanced counterweights that adapt to varying motion requirements. This dynamic design allows the system to maintain high stroke performance during low-to-medium frequency operations while preserving the capability for high-amplitude outputs when needed, thereby improving overall motion simulation quality without sacrificing stroke capability.
Solution Approach 2:
The system utilizes variable parameter design in the piston assembly, including adjustable mass distribution and configurable counterbalance mechanisms. These parameter changes allow optimization for low-to-medium frequency motion simulation while maintaining the structural integrity and stroke performance necessary for high-amplitude outputs, resolving the contradiction between simulation quality and stroke capability.
3Ease of operation
If friction between sliding tube and joint surface is reduced, then motion smoothness improves, but load capacity and stability deteriorate
Solution Approach 1:
The traditional sliding contact between the piston and cylinder wall is replaced with a ball screw mechanism that converts rotational motion into linear displacement through rolling contact. This mechanical substitution eliminates direct sliding friction, dramatically improving motion smoothness while the ball-bearing-based system maintains high load capacity and stability through efficient rolling contact mechanics.
Solution Approach 2:
The ball screw mechanism operates through periodic rotational cycles that convert continuous rotation into precise linear increments. This periodic action mechanism reduces cumulative friction effects compared to continuous sliding, improving motion smoothness while maintaining load capacity through the self-locking特性 of the ball screw threads that prevent back-driving under load.
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 design achieves efficient translation of rotational motion into linear motion with a high load capacity and frequency range, supporting up to 340 kg with an amplitude of 140-152 mm, while maintaining low friction and stability, suitable for motion simulators and other applications.
Implementation Method 1
at least one travelling nut or like travelling member connected to the sliding tube assembly for moving with the sliding tube in the axial direction, the travelling nut or like travelling member being operatively engaged to the shaft for converting a rotational motion of the shaft into a translation of the sliding tube
Implementation Method 2
a liner between the sliding tube and the joint surface of the inner cavity, an inner surface of the liner defining longitudinal contact surfaces separated by longitudinal grooves, the longitudinal contact surfaces contacting the sliding tube
Implementation Method 3
at least some of the longitudinal contact surfaces apply a biasing force on the sliding tube
Data Source
AI summary
A linear actuator comprises a motor for producing a bi-directional rotational output. A casing is connected to the motor at a proximal end, the casing having an inner cavity defining a joint surface. A shaft is within the inner cavity of the casing and actuated by the motor for rotation. A sliding tube is at least partially in the inner cavity of the casing for moving in translation in an axial direction relative to the casing. One or more travelling nut is connected to the sliding tube assembly for moving with the sliding tube in the axial direction, the travelling nut being operatively engaged to the shaft for converting a rotational motion of the shaft into a translation of the sliding tube. A liner is between the sliding tube and the joint surface of the inner cavity, an inner surface of the liner defining longitudinal contact surfaces separated by longitudinal grooves, the longitudinal contact surfaces contacting the sliding tube.