Dual Ball Screw Actuator for Variable Speed and Brake Force
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Solution Overview
Problem
Existing electromechanical linear actuators for aircraft braking face a compromise between speed and force, often requiring complex gear shifting solutions that increase system complexity, weight, and failure points.
Innovation Solution
The development of an electromechanical actuator with a dual screw configuration, featuring a dual ball screw system with slightly different lead constants, allowing for a dual speed operation without the need for a traditional gearbox.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reduction gear ratio and ball screw lead constant are used, then the actuator structure is simple, but a compromise must be made between speed and force
Solution Approach 1:
The patent applies dynamics by making the ball screw lead constant variable through a selectable mechanism. The ball screw assembly can be switched between different lead constants (first lead constant for high speed, second lead constant for high force), transforming a static system into a dynamic one that adapts to different operational requirements. This resolves the contradiction by allowing the actuator to achieve both high speed and high force at different times without compromising structural simplicity.
Solution Approach 2:
The patent changes the parameter of ball screw lead constant from fixed to variable. By providing a mechanism to select between different lead constants, the system can optimize performance for either speed or force depending on the operational phase. This parameter change enables the actuator to overcome the compromise inherent in fixed-parameter designs.
2Speed
If gear shifting solutions are added to achieve variable speed, then speed and force requirements are met, but system complexity increases
Solution Approach 1:
The patent extracts the traditional gearbox component from the system and replaces it with a ball screw assembly that has a selectable lead constant. This removal of the complex gear shifting mechanism while retaining the variable speed/force capability through the ball screw's selectable geometry directly addresses the contradiction by eliminating unnecessary complexity.
Solution Approach 2:
The patent substitutes the traditional mechanical gear shifting system with a ball screw-based mechanism. Instead of using multiple gears and shafts to achieve variable speed ratios, the system uses a ball screw assembly where the lead constant can be selected, providing a more compact and simpler mechanical solution.
3Speed
If gear shifting solutions are implemented, then dual speed operation is achieved, but weight increases
Solution Approach 1:
The patent merges the functions of speed variation and force multiplication into a single ball screw assembly with selectable lead constants. Instead of having separate mechanisms for speed control and force generation, the ball screw system combines both functions, reducing overall system weight while achieving dual-speed operation.
4Speed
If more components are added for gear shifting, then speed control is improved, but failure points increase
Solution Approach 1:
The patent removes the gear shifting components (gears, shafts, bearings, lubrication systems) that create multiple failure points. By extracting these complex components and replacing them with a simpler ball screw assembly with selectable lead constants, the system achieves speed control with fewer parts and consequently fewer potential failure points.
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
This solution enables faster translation speed with lesser force during initial deployment and greater force with slower translation speed during full application, reducing system complexity and weight while maintaining effective braking performance.
Implementation Method 1
a first ball screw (112) and a second ball screw (110), each having a screw (121, 125) and a nut (123), configured to translate along the axis of rotation (A, B) in response to rotation of the rotor (104)
Data Source
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AI summary
An electromechanical actuator (EMA) (100,200) is provided. The EMA may comprise a ball nut (116, 216) having an annular geometry centered about an axis. A dual ball screw (110, 210) may be disposed radially inward from the ball nut and configured to rotate about the axis. The dual ball screw may also be mechanically coupled to the ball nut. A ball screw (112, 212) may be disposed radially inward from the ball nut and configured to rotate about the axis. The ball screw may also be mechanically coupled to the dual ball screw.