Geometric Control Envelope for Stable Motor Command Limiting
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Solution Overview
Problem
Control systems for drones and other vehicles face challenges in mapping desired flight commands to motor commands due to motor limitations, leading to unstable control conditions when commands exceed maximum or minimum motor settings.
Innovation Solution
A geometric control envelope system that projects desired operation points into a geometric space, ensuring motor commands remain within safe limits by using a closest point within the envelope, prioritizing control aspects, and scaling dimensions to maintain stable flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If motor mapping function is used to convert flight commands to motor commands, then flight control is achieved, but motors may operate beyond maximum or minimum limits causing unstable control conditions
Solution Approach 1:
The control envelope is pre-computed based on motor characteristics, maximum/minimum limits, and mapping function parameters before flight operations. This preliminary calculation establishes safe operating boundaries that prevent motors from exceeding their limits during actual flight control, thereby maintaining both ease of operation and control stability
Solution Approach 2:
The control envelope acts as an intermediary layer between the flight command input and the motor mapping function. It filters and constrains the mapping function outputs to ensure they remain within safe motor operating limits, preventing unstable control conditions while preserving the intended flight control functionality
2Reliability
If geometric control envelope is implemented to limit motor commands, then motor operating limits are enforced, but control system complexity increases
Solution Approach 1:
The control envelope geometry is pre-computed offline based on motor characteristics, maximum/minimum limits, and mapping function parameters. This eliminates the need for complex real-time calculations during flight, as the envelope boundaries are stored and simply evaluated against motor commands, thus enforcing motor limits without significantly increasing runtime control system complexity
Solution Approach 2:
The control envelope transforms the one-dimensional motor command limiting problem into a multi-dimensional geometric constraint problem. By representing motor commands as points in a geometric space with constraints defined by envelope surfaces, the system efficiently handles multiple motor limit constraints simultaneously through geometric evaluation rather than sequential logical checks
Data Source
AI summary
A vehicle and method of control comprising generating a geometric control envelope in a geometric space of operation points defined by a number of control aspects, the envelope having vertices representing maximum values of the control aspects, and determining a desired operation point in the geometric space representing a control input. Further, the method includes if the desired operation point is outside the envelope, scaling up a first one of the control aspects by a first factor, determining an effective operation point in the envelope geometrically closest to the desired operation point, scaling down all of the control aspects by a second factor inverse of the first factor, and instructing the propulsion mechanisms to propel the vehicle according to the effective operation point.