Inverted Roller Screw Actuator for Lighter, Stiffer Flight Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Long stroke ball screw actuators used in aerial vehicles have low stiffness and high weight, leading to low natural frequencies and complex maintenance, which increases space requirements and maintenance time.
Innovation Solution
An actuator system featuring an inverted roller screw with a plurality of rollers and a lubricant distribution system, where the rollers have roller threads engaging with nut threads on an inverted nut, reducing weight and maintenance complexity by providing efficient lubrication to the rollers and nut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If larger output rod and ball screws are employed to increase stiffness and natural frequency, then the stiffness and natural frequency improve, but the weight increases
Solution Approach 1:
The patent inverts the conventional ball screw configuration by placing the nut on the stationary side and the screw on the moving side. This inversion allows the use of a smaller, lighter screw while maintaining stiffness requirements, as the load path is optimized through the inverted configuration. The lighter screw directly reduces the moving weight while the inverted design preserves the necessary structural rigidity.
2Strength
If larger output rod and ball screws are employed to increase stiffness and natural frequency, then the stiffness and natural frequency improve, but the space required increases
Solution Approach 1:
By inverting the ball screw configuration, the patent enables a more compact design where the screw occupies less space. The inverted arrangement allows the screw to be positioned within the actuator housing rather than extending externally, reducing the overall space footprint while maintaining the stiffness required for high natural frequency operation.
3Ease of operation
If conventional ball screw actuators are used, then the actuator can move the flight control surface, but the maintenance is time consuming and complex
Solution Approach 1:
The patent incorporates a self-lubricating mechanism where the ball screw is filled with lubricant that is automatically distributed to friction surfaces during operation. This self-service lubrication system eliminates the need for manual lubrication maintenance, reducing maintenance complexity and time requirements while ensuring continuous operation capability.
4Ease of operation
If conventional ball screw actuators are used, then the actuator can move the flight control surface, but the maintenance time increases
Solution Approach 1:
The self-lubricating ball screw design automatically replenishes lubricant to friction surfaces during normal operation, eliminating the need for periodic manual lubrication. This self-service capability significantly reduces maintenance time by preventing lubricant depletion and wear, allowing the actuator to operate for extended periods without intervention.
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 actuator system achieves reduced weight and increased stiffness, improving dynamic load capacity and simplifying maintenance by lubricating components without disassembly, resulting in a weight savings of 5% to 15% and enhanced operational efficiency.
Implementation Method 1
The at least one roller includes a plurality of roller threads. The inverted nut is coupled about the shaft such that the plurality of nut threads are configured to engage with the plurality of roller threads to move the inverted nut relative to the shaft.
Implementation Method 2
The inverted nut includes a source of a lubricant in fluid communication with the inner bore and the plunger is configured to be received within the inner bore to supply the lubricant to the at least one roller.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An actuator system for a flight control surface of an aerial vehicle includes a motor (102), and an inner shaft (108). The inner shaft includes a first portion at a first end and a second portion that extends from the first portion to a second end of the inner shaft. The first portion of the inner shaft is coupled to the motor. The second portion of the inner shaft is coupled to at least one roller (206) that includes roller threads. The actuator system includes an inverted nut (110) defining an inner bore and having an outer diameter that defines an output rod (110). The inner bore includes nut threads. The inverted nut is coupled about the inner shaft such that the nut threads are to engage with the plurality of roller threads to move the output rod, and the output rod is to be coupled to the flight control surface.