Aircraft Velocity Control via Dual-Loop Feedback
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Solution Overview
Problem
Existing flight control systems for aircraft experience undesirable accelerations and oscillations in turbulent air conditions, leading to passenger discomfort due to inadequate control of airspeed and inertial velocity.
Innovation Solution
A dual-loop feedback control system that combines airspeed and inertial velocity signals to generate an actuator command, minimizing primary error and reducing longitudinal accelerations by integrating the airspeed error signal, thereby stabilizing the aircraft and reducing engine power changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical closed-loop feedback control system is used to control airspeed, then the airspeed can be maintained at the commanded value, but undesirable longitudinal accelerations and oscillations occur in turbulent air conditions
Solution Approach 1:
The control system is segmented into two independent loops: an outer airspeed control loop and an inner inertial velocity control loop. Each loop handles a specific aspect of velocity control, allowing the system to address both airspeed maintenance and turbulence-induced accelerations separately and effectively
Solution Approach 2:
Inertial velocity serves as an intermediary parameter between the airspeed command and the actuator control. The inner loop controls inertial velocity to counteract turbulence effects, while the outer loop maintains airspeed, creating a coordinated control strategy that reduces harmful accelerations
2Measurement precision
If the control system commands throttle position changes to correct airspeed errors, then airspeed control is achieved, but engine power changes cause additional accelerations and passenger discomfort
Solution Approach 1:
The inner inertial velocity loop acts in advance to counteract turbulence-induced velocity changes before they translate into airspeed errors that would require large throttle adjustments. By pre-compensating for inertial velocity changes, the system reduces the magnitude of engine power changes needed
Solution Approach 2:
The system changes the control parameter from direct throttle position control to a two-stage approach: first controlling inertial velocity, then adjusting airspeed. This parameter transformation allows the system to achieve airspeed control while minimizing harmful engine power changes
3Device complexity
If a single-loop airspeed control system is used, then the system complexity is low, but the system exhibits overshoots and undershoots in turbulent conditions
Solution Approach 1:
The control system is divided into two nested loops with distinct functions: the outer airspeed loop provides stable reference management, while the inner inertial velocity loop provides rapid disturbance rejection. This segmentation enhances stability without requiring overly complex control algorithms
Solution Approach 2:
The system implements dual feedback mechanisms: airspeed feedback for long-term stability and inertial velocity feedback for short-term disturbance rejection. This layered feedback approach improves stability by addressing both steady-state and dynamic behavior
Data Source
AI summary
A flight control system for an aircraft receives a selected value of a first parameter, which is either the airspeed or inertial velocity of the aircraft. A primary feedback loop generates a primary error signal that is proportional to the difference between the selected value and a measured value of the first parameter. A secondary feedback loop generates a secondary error signal that is proportional to the difference between the selected value of the first parameter and a measured value of a second flight parameter, which is the other of the airspeed and inertial velocity. The primary and secondary error signals are summed to produce a velocity error signal, and the velocity error signal and an integrated value of the primary error signal are summed to produce an actuator command signal. The actuator command signal is then used for operating aircraft devices to control the first parameter to minimize the primary error signal.