Servo System Structural Mode Elimination via Accelerometer Feedback
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Solution Overview
Problem
Existing servo systems fail to effectively eliminate structural deformation modes in flexible structures, leading to limited performance and increased jitter in gimbal stabilization, as they often require lowering the zero dB crossover frequency or using notch filters that restrict gain and stability.
Innovation Solution
A servo system employing multiple accelerometers to sense accelerations in flexible structures, generating a compensation feedback signal that eliminates structural modes, allowing the servo loop to operate near or above resonant frequencies, thereby increasing gain while maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional servo control is used to stabilize flexible structures, then the system can operate at lower frequencies, but the zero dB crossover frequency must be lowered which limits performance and increases jitter
Solution Approach 1:
The patent employs accelerometers to measure structural vibrations and feeds this information back to the servo controller. The controller generates compensation signals that counteract the measured vibrations, allowing the system to maintain stability at higher crossover frequencies by actively canceling out structural modes rather than avoiding them.
Solution Approach 2:
Accelerometers serve as intermediary sensors that measure the structural response between the motor and the flexible structure. By placing sensors at strategic locations on the flexible structure, the system can detect vibrations and use them to generate compensating signals that eliminate structural modes.
2Reliability
If notch filters are used to eliminate structural modes, then stability can be maintained, but gain is restricted which limits performance
Solution Approach 1:
Instead of using passive notch filters that attenuate specific frequencies, the system uses active feedback control with accelerometers to measure and counteract vibrations in real-time. This allows the full gain to be utilized across the bandwidth without the performance degradation caused by notch filter attenuation.
3Measurement precision
If multiple accelerometers are used to sense structural modes, then measurement precision improves, but device complexity increases
Solution Approach 1:
The flexible structure is divided into multiple segments or modes of vibration, each sensed by strategically placed accelerometers. By segmenting the measurement task across multiple sensors positioned at nodes of different vibrational modes, the system achieves comprehensive coverage of structural dynamics with a minimal number of sensors.
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
The solution enables the servo system to operate at higher bandwidths, reduce structural mode deformations, and minimize jitter, allowing for improved stabilization and disturbance rejection in flexible structures.
Implementation Method 1
A first sensor, a second sensor, a motor, and a servo controller are provided. The first sensor is disposed relative to a first of the two masses of the flexible structure to sense a first acceleration of the first mass. The second sensor is disposed relative to a second of the two masses to sense a second acceleration of the second mass.
Data Source
AI summary
A servo system is provided for controlling movement of a flexible structure having multiple masses and elements. Each element couples a respective two of the masses and functions as a spring when the flexible structure is subject to a linear or rotational input at or above a frequency at which the respective element exhibits flexure. The servo system includes multiple sensors, where each sensor is disposed relative to a respective one of the masses to sense a respective acceleration. A motor having a torque input may operatively be configured to output one of a linear or rotational force on the first mass based on a torque signal present on the torque input. A servo controller that receives each sensed acceleration from each sensor may generate a compensation feedback signal based on a sum of sensed accelerations. The torque signal may be output to the motor based on the compensation feedback signal.