Centering Release Reset Mechanism for Aircraft Stabilizer Actuators
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Solution Overview
Problem
Modern aircraft stabilizer actuators face catastrophic failures due to unaddressed deflections and oscillations when the primary load path fails, as existing designs lack adequate mechanisms to prevent load sharing between primary and secondary paths during normal operations and fail to minimize oscillatory modes effectively.
Innovation Solution
A centering, release, and reset mechanism with a primary load path element and a secondary load path element, featuring a pin-key, compression cam, tension cam, and leaf spring assembly, which allows freedom of movement and minimizes axial backlash by engaging locks only upon primary load path failure, preventing excessive oscillations and ensuring structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary load path is designed with gaps to prevent load sharing during normal operations, then the primary load path can operate without interference, but excessive axial backlash occurs when the primary load path fails and the secondary load path is engaged
Solution Approach 1:
The cam mechanism is pre-configured with specific geometric profiles and preload forces that automatically activate when the pin-key reaches certain positions during primary load path failure. The cams are designed to engage the pin-key and minimize axial backlash before oscillatory modes can develop, preventing the harmful effects rather than reacting to them later
Solution Approach 2:
The mechanism changes the mechanical parameters of the secondary load path dynamically. During normal operation, gaps maintain zero preload. Upon primary failure, the cam mechanism introduces controlled preload forces and changes the stiffness characteristics of the secondary path, transforming it from a loose standby to a tightly engaged load-bearing structure that resists oscillations
2Stability of the object's composition
If locks are engaged to minimize axial backlash in the secondary load path, then oscillatory modes are prevented, but the actuator becomes jammed and uncontrollable
Solution Approach 1:
The locking mechanism is designed to be dynamic rather than static. The cam-follower arrangement allows the locks to engage and disengage based on the operational state. During normal operation, the follower maintains clearance from the cam lobes, keeping the secondary path loose and the actuator fully controllable. Upon primary failure, the follower contacts the cam lobes, activating the locks to prevent oscillations while still allowing controlled movement through the ball screw mechanism
3Reliability
If the secondary load path is designed to automatically mobilize upon primary load path failure, then structural integrity is maintained, but the transfer of support occurs rapidly causing excessive oscillations
Solution Approach 1:
The cam mechanism with preload forces acts as a cushioning element during the transition from primary to secondary load path. The gradual engagement of the cam lobes with the follower, combined with the spring preload, provides a controlled, progressive transfer of load rather than an abrupt shift. This cushioning effect dampens oscillations during the failover process while maintaining structural integrity
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 effectively transfers load from the primary to the secondary path without shared loading during normal operations, minimizing axial backlash and preventing catastrophic failures by engaging locks only when necessary, thus ensuring the actuator remains stable and controllable.
Implementation Method 1
a leaf spring assembly includes a spring carrier piloted on an end of the secondary load path element; and, leaf springs carried by the spring carrier and fastened to the secondary load path element. The leaf springs provide the preload force.
Implementation Method 2
A compression cam is positioned within an opening in the secondary load path element. The opening defines a grooved cam seat for permitting the compression cam to have a defined pivot and stop. A tension cam is positioned within the opening in the secondary load path element.
Data Source
AI summary
The mechanism includes a primary load path element having at least one slot. A pin-key within the primary load path element slot allows freedom of movement in a rotational direction orthogonal to a positioning direction. A secondary load path element includes at least one secondary load path element slot. A key is positioned between the load path elements. A compression cam is positioned within an opening in the secondary load path element that defines a grooved cam seat. A tension cam is positioned within the opening in the secondary load path element. The tension cam has a defined pivot and stop. A cam follower rests on lobe surfaces of the cams. The cam follower applies a preload force to both cams opposing the cam's rotation. A push rod is seated in a hole in the cam follower and extends through a respective hole in the secondary load path element.