Aircraft Control Allocation With Null-Space Task Prioritization
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Solution Overview
Problem
Overdetermined systems with multiple actuators, such as aircraft, face challenges in prioritizing control axes to ensure safety and controllability, especially when operating near the limits of their control volume, where low-priority tasks may adversely affect high-priority tasks.
Innovation Solution
A method that involves determining pseudo-control commands and dissociating the control matrix into sub-matrices to prioritize tasks, projecting non-primary tasks into the null space of higher-priority tasks to prevent interference, ensuring that actuator control commands for primary tasks are not affected by secondary or tertiary tasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple tasks with different priorities are combined in a single control assignment problem, then the system can perform both primary and non-primary tasks, but the low-priority tasks may adversely affect the high-priority tasks and solution stability
Solution Approach 1:
The control assignment problem is segmented into multiple independent sub-problems, each corresponding to a specific task priority level. The control matrix D is dissociated into sub-matrices Di, and the pseudo-control command up is decomposed into components up,i for each priority level i. This segmentation allows each task to be solved independently in sequence, preventing lower-priority tasks from affecting higher-priority ones.
Solution Approach 2:
The patent introduces a new dimension of task priority indexing into the control problem. By associating each task with a priority index i and solving tasks in sequential order from highest to lowest priority, the system adds a temporal and hierarchical dimension to the control assignment, ensuring that higher-priority tasks are satisfied before allocating remaining actuator capacity to lower-priority tasks.
2Reliability
If the control matrix is dissociated into sub-matrices for different task priorities, then high-priority tasks can be solved independently, but the system complexity increases
Solution Approach 1:
The control matrix D is explicitly segmented into sub-matrices Di corresponding to different task priority levels. Each sub-matrix Di handles a specific priority level i, allowing independent computation of control commands for each task group. This segmentation structure makes the complexity manageable by breaking down the large control problem into smaller, priority-based sub-problems.
Solution Approach 2:
The patent applies preliminary action by first solving the highest-priority task (i=1) to obtain control commands u1, then using these results as a basis for solving the next priority level task. Each subsequent task solution builds upon the previously computed control commands, ensuring that higher-priority requirements are met before addressing lower-priority ones.
Data Source
AI summary
A method for controlling an overdetermined system with multiple power-restricted actuators that perform a primary task and non-primary tasks, including: a) determining a pseudo-control command based on a physical model of the system, which pseudo-control command represents the torques and a total thrust force acting on the system, b) determining a control matrix, c) dissociating the control matrix into sub control matrices, wherein the sub control matrices and the corresponding sub pseudo-control commands correspond to the primary task for i=1 and for i>1 correspond to the non-primary task(s) and a priority of the non-primary tasks decreases with increasing index i, d) determining actuator control commands for solving the primary task, e) projecting the non-primary tasks into the null space of the primary task, and into respective null spaces of all of the non-primary tasks of higher priority, if present, and f) providing the actuator control commands from d) and e) at the actuators.