Piezoelectric Modal Sensors for Missile Flight Control
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Solution Overview
Problem
Flight control systems for missiles face instability due to flexible body dynamics, leading to self-exciting vibrations and potential structural damage, which existing solutions like phase-compensated and gain-compensated control systems struggle to address effectively, especially in lightweight and cost-sensitive designs.
Innovation Solution
The implementation of piezoelectric modal sensors to measure and subtract flexible body mode rates and accelerations from IMU data, using sensors configured to sense specific modes like the 1st lateral bending mode without inducing phase loss, thereby improving gain and phase margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If phase-compensated control systems are used to mitigate flexible body dynamics, then stability is improved, but device complexity and manufacturing cost increase due to carefully designed actuators and critical IMU placement requirements
Solution Approach 1:
The patent introduces flexible body mode sensors as an intermediary element that directly measures the flexible body modes. This mediator provides explicit measurement of the problematic vibrations, allowing the control system to compensate for them without requiring complex actuator designs or critical IMU placement. The sensors act as a bridge between the flexible body dynamics and the control system, simplifying the overall solution.
2Reliability
If digital notch filters are used to attenuate flexible body modes, then gain margin is improved, but phase margin deteriorates due to additional phase loss in the control loop
Solution Approach 1:
The patent extracts the flexible body mode information from the overall system dynamics by using dedicated sensors to measure these modes directly. By separating the measurement of flexible body modes from the rigid body motion measurements, the system can compensate for flexible modes without introducing the phase loss associated with digital notch filters. This extraction approach allows independent handling of flexible mode compensation.
3Stability of the object's composition
If actuator bandwidth is increased to actively dampen the 1st lateral bending mode, then phase compensation is achieved, but power consumption and stress on actuators increase
Solution Approach 1:
The patent enables the system to self-monitor flexible body modes through dedicated sensors, providing direct feedback about the vibration states. This self-service capability allows the control system to respond efficiently to flexible mode excursions without requiring excessive actuator bandwidth or power consumption. The sensors provide the information needed for precise, energy-efficient compensation.
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
This approach enhances the stability of the flight control system by maintaining suitable gain and phase margins, reducing latency, and allowing for higher performance and maneuverability in missiles, as demonstrated by improved gain and phase margins compared to conventional digital notch filtering.
Implementation Method 1
The sensor is configured to sense the mode over variations in the modal frequency without inducing additional phase loss in the control loop
Data Source
AI summary
A flight control system is provided with one or more modal sensors that are each configured to measure the rate and possibly acceleration for a flexible body mode of the flight vehicle. The modal sensor's rate and suitably acceleration are subtracted from the rate and acceleration measured by the IMU such that the values provided to the flight controller more closely represent only the rate and acceleration of the flight vehicle's rigid airframe component. A piezoelectric modal sensor is capable of sensing a particular flexible body mode over variations in the modal frequency without inducing additional phase loss in the control loop in order to maintain suitable phase and gain margins. Sensors are suitably provided for at least and possibly only the 1st lateral bending modes in the pitch and yaw channels.