Kernekoncepter
This paper presents an algorithmic and mechanical approach to addressing the quadrotor fault-tolerant problem in case of rotor failures, including a fault-tolerant detection and control scheme, and a modular mechanical design to enhance the steady-state angular velocity dynamics for flight safety.
Resumé
The paper introduces and validates a fault-tolerant control scheme that combines multiple attitude error metrics with a fault-tolerant detection module. It studies the intricate connection between the introduction of augmented drag obtained through a modular mechanical design appendage and the resulting yaw rate of the compromised quadrotor, aiming to enhance steady-state angular velocity dynamics for flight safety.
The key highlights and insights are:
- The paper evaluates three distinct reduced attitude error metrics (current yaw, S2, and thrust vector) for fault-tolerant control, finding the S2 and thrust vector methods perform similarly and better than the current yaw metric.
- The fault detection algorithm uses L1 adaptation to estimate the damage percentage of each rotor-propeller pair, triggering the transition to fault-tolerant control when damage exceeds 50%.
- Experiments show the maximum speed of the fault-tolerant controller is 3 m/s and the maximum attitude angle (roll, pitch) is approximately 30°. Aggressive maneuvers result in large position errors.
- The paper analyzes the relationship between the added rotational drag and the resulting steady-state yaw rate, providing a platform-agnostic guideline that the drag coefficient should be between 0.05 to 0.35 to maintain a controllable yaw rate within the gyroscope limits.
- The transition from normal to fault-tolerant control requires a reaction time of 100-150 ms and sufficient initial altitude (at least 1 m) to avoid a dramatic descent during the transition period.
Statistik
The quadrotor used in the experiments has a total weight of 700 g and a thrust-to-weight ratio of 2.5 to 1.
The gyroscope on the platform is rated up to 35 rad/sec (±2000°/s).
Citater
"Quadrotors have gained popularity over the last decade, aiding humans in complex tasks such as search and rescue, mapping and exploration. Despite their mechanical simplicity and versatility compared to other types of aerial vehicles, they remain vulnerable to rotor failures."
"We find the maximum speed of our fault-tolerant controller to be 3 m/s and the maximum attitude angle (roll, pitch) to be approximately 30°. The maximum speed is due to the current size of our indoor arena, and the system is capable of greater speeds with the room for further acceleration."
"To maintain a controllable steady-state yaw rate, the quadrotor's rotational drag coefficient should fall within the range of 0.05 to 0.35, irrespective of the platform."