A method for evaluating the thrust of a space propulsion device with wide range time variations using a disturbance...

Area of Science:

• Aerospace Engineering
• Control Systems Engineering
• Measurement Science

Background:

• Traditional thrust measurement methods struggle with high-frequency variations, particularly beyond the resonant frequency of the test apparatus.
• Accurate thrust evaluation is critical for rocket engine development, performance optimization, and safety.

Purpose of the Study:

• To present a new method for evaluating thrust with high-frequency variations using a disturbance observer.
• To assess the accuracy and applicability of this method across a wide frequency range (0-100 Hz).
• To compare the influence of proportional-derivative-integral (PID) controller design on the proposed method versus conventional techniques.

Main Methods:

• Implementing setpoint control on a pendulum-type thrust stand using a solenoid actuator.
• Measuring pendulum acceleration and solenoid-actuator current during controlled operation.
• Utilizing a disturbance observer to determine thrust from measured data, enabling analysis of frequency variations.

Main Results:

• The disturbance observer method successfully evaluates thrust with constant, low-frequency, and high-frequency variations beyond the resonant frequency.
• A prototyped device showed thrust measurement errors of 20% below 90 Hz.
• PID controller design had a less significant impact on the proposed method's accuracy compared to the conventional null-balance method.

Conclusions:

• The developed method provides accurate thrust evaluation across a broad frequency spectrum, including challenging high-frequency ranges.
• The proposed technique offers comparable or improved performance to conventional methods with potentially less sensitivity to PID controller tuning.
• This advancement has significant implications for precise rocket engine testing and characterization.