Rotary Actuator Stop Module for Non-Jamming End-of-Stroke Braking
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Solution Overview
Problem
Existing end-of-stroke stopping mechanisms for rotary drive actuators, such as geared rotary actuators in aircraft control systems, face challenges in quickly dissipating excess rotational kinetic energy while minimizing weight and size, and preventing jamming at travel limits, especially when reverse rotation is required for resetability.
Innovation Solution
A stop module is implemented that mechanically links two gear stages with different rotational speeds, using spur gear nuts and a brake plate to impede relative motion and engage brake disks at travel limits, allowing for safe stopping and resetability through axial travel of the nuts and brake plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a hard stop mechanism is used to quickly dissipate rotational kinetic energy at travel limits, then stopping speed is improved, but jamming occurs preventing reset by reverse rotation
Solution Approach 1:
The stop module employs dynamic binding where the brake plate is selectively engaged by the spur gear nuts only when the speed difference between the two planetary gear stages exceeds a threshold. During normal operation or reverse rotation, the nuts remain disengaged, allowing free rotation. This dynamic engagement/disengagement mechanism enables quick stopping when needed while preventing permanent jamming that would block reset operations.
Solution Approach 2:
The system changes the engagement parameter of the stop module based on the speed difference between gear stages. When the speed difference parameter exceeds a threshold, the brake plate engages; when it falls below the threshold (during reverse rotation or normal operation), the brake plate disengages. This parameter-based control resolves the contradiction by making the stopping mechanism conditional rather than permanent.
2Power
If a stop module is added to dissipate excess rotational kinetic energy, then stopping capability is improved, but device weight and size increase
Solution Approach 1:
The stop module is integrated into the existing planetary gear system, where the brake plate and spur gear nuts utilize the speed difference between existing gear stages to perform both the stopping function and the reset function. The brake plate serves as both the stopping element and the reset indicator, eliminating the need for separate heavy-duty stopping mechanisms. This multi-functionality approach achieves strong stopping capability while minimizing additional weight.
3Reliability
If a stop module is added to prevent jamming at travel limits, then reliability is improved, but device complexity increases
Solution Approach 1:
The stop module operates autonomously by exploiting the natural speed difference between the two planetary gear stages. The spur gear nuts automatically engage the brake plate when the speed difference indicates an end-of-stroke condition, and automatically disengage when reverse rotation occurs. This self-regulating mechanism prevents jamming without requiring external control systems, sensors, or complex actuation mechanisms, thereby maintaining simplicity while improving reliability.
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 effectively prevents jamming, ensures quick stopping and resetability, and minimizes weight and size, making it suitable for aircraft applications by leveraging the speed difference in multistage planetary gear systems.
Implementation Method 1
a first spur gear nut and a second spur gear nut threadably mated with the threaded portion of the first stage carrier
Data Source
AI summary
A rotary actuator has a stop module configured to mechanically link two gear stages travelling at different rotational speeds when an end-of-stroke travel limit is reached, thereby causing the rotary actuator to bind because relative motion between the gear stages is impeded.