Wedge Brake Assembly for HAP Propeller Descent Control
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Solution Overview
Problem
High altitude platforms (HAPs) operating in the stratosphere face challenges in maintaining directional control and preventing uncontrolled propeller rotation during descent or power loss, which can lead to entanglement with envelope or parachute components and overvoltage issues.
Innovation Solution
A reusable wedge brake mechanism is implemented, comprising a brake pad, a housing, a brake sensor, and an actuator assembly with a magnet and solenoid, which engages the propeller hub to stop rotation quickly and prevent free spinning, using a spring and Hall Effect sensor for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the propeller is allowed to rotate freely during descent or power loss, then the HAP can maintain operational flexibility, but the propeller may become entangled with envelope or parachute components and cause overvoltage issues
Solution Approach 1:
The brake mechanism is pre-configured with the brake pad positioned near the propeller hub, and the actuator assembly is pre-charged with potential energy (via the spring) to immediately engage the brake when needed. This preliminary preparation allows the system to transition from flexible rotation to controlled stopping without delay during emergency descent scenarios.
Solution Approach 2:
The brake pad acts as an intermediary element between the propeller hub and the housing, providing controlled friction to stop propeller rotation. The actuator assembly serves as another intermediary, mediating between the control system and the brake pad to enable precise engagement and disengagement timing.
2Reliability
If a brake mechanism is added to stop propeller rotation quickly, then entanglement and overvoltage issues are prevented, but the device complexity increases
Solution Approach 1:
The brake mechanism components (brake pad, housing, actuator assembly) are merged into a compact integrated unit that attaches to the propeller assembly. The actuator assembly combines the magnet, spring, and arm member into a single coordinated mechanism, reducing the number of separate systems needed while maintaining the safety function.
Solution Approach 2:
The brake mechanism serves multiple functions: it stops propeller rotation during descent to prevent entanglement, prevents overvoltage issues by controlling propeller speed, and can be engaged or disengaged based on operational mode. The actuator assembly provides both engagement and disengagement capabilities through a single unified mechanism.
3Reliability
If the brake pad is constantly engaged to prevent rotation, then safety is maintained, but the propeller cannot rotate for lateral propulsion
Solution Approach 1:
The brake mechanism transitions from a static engaged state to a dynamic controllable state. The actuator assembly enables the brake pad to move between engaged and disengaged positions based on real-time operational requirements, allowing the system to adapt between safety mode and propulsion mode seamlessly.
Solution Approach 2:
The system uses feedback from operational conditions (descent mode vs. propulsion mode) to control brake engagement. When descent is detected or power is lost, the brake engages automatically; when lateral propulsion is needed, the brake disengages to allow propeller rotation. This feedback-based control ensures both safety and operational effectiveness.
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 brake mechanism enables rapid stopping of the propeller within 0.3-2.0 seconds, preventing entanglement and overvoltage, and maintaining system safety during descent or power loss scenarios.
Implementation Method 1
The actuator assembly may include a spring configured to provide a spring force to cause the brake pad to engage the propeller hub
Implementation Method 2
a brake pad configured to engage with a hub portion of the propeller assembly to stop the rotation of the propeller assembly
Implementation Method 3
a Hall Effect sensor in operative communication with the second magnet affixed to the second extension, in which the Hall Effect sensor is configured to detect the strength of a magnetic field associated with the second magnet to detect a relative displacement of the brake pad
Implementation Method 4
an actuator assembly including a magnet and an actuator... The actuator may be a solenoid
Data Source
AI summary
Aspects of the technology relate to a braking assembly for a lateral propulsion system of a high altitude platform (HAP) configured to operate in the stratosphere. Power is supplied to a propeller assembly as needed during lateral propulsion so that the HAP can move to a desired location or remain on station. When lateral propulsion is not needed, power is no longer supplied to the propeller assembly and it may slowly cease rotating. However, in certain situations, it may be necessary to cause the propeller assembly to stop rotating as soon as possible. This can include an unplanned descent. Rapid braking can avoid the propeller blades from entangling in the envelope, parachute or other parts of the HAP. A reusable brake is employed to prevent uncontrolled rotation of the propeller on descent, or otherwise to prevent the propeller from spinning freely when not being used to propel the HAP laterally.