A Force Control Test Rig for the Dynamic Characterization of Helicopter Primary Flight Control Systems

Abstract

This paper describes an electronically controlled active force control system developed to test the tail rotor actuator of a new medium size helicopter. As for all hydraulic force control systems, the critical control issue is to mitigate the disturbance generated by the actuator velocity. For this particular case, the problem was accrued by the high bandwidth of the tail rotor actuator. To define the optimum control algorithm a model based approach was followed, estimating, when unable to measure directly, mechanical and hydraulic model parameters with a dedicated experimental campaign. A controller was eventually developed able to cope with the severe dynamic disturbances by introducing velocity and acceleration compensation laws. The controller was then implemented in a high recursion rate real time machine interfacing with a servovalve controlling the flow to a hydraulic actuator provided with hydrostatic bearings to minimize the friction force. The actuator force was sensed by a load cell providing the feedback signal for the force servoloop. A critical feature of the control was the need to develop a dedicated complex filter for the velocity signal able to cancel out the signal noise while allowing to retain the correct real time information of the actuator velocity and maintain adequate stability margins.

A Virtual Test Bench of a Parallel Hybrid Propulsion System for UAVs

“…The first one is to mount physical inertias equal to I s1 , I s2 and I s3 on the motor axis EM1, EM2 and EM3. This approach is commonly used in test benches of flight servo-actuators, where the inertia of the flight control surface is simulated by an adjustable mass, but has the drawback of needing additional space on the real test bench [16].…”

“…The virtualization of part of the test bench is pretty common in the automotive field, as reported in [14], where the electric energy storage has been replaced with a software-in-the-loop. The same procedure is usually applied in complex aeronautic test benches and Iron Birds, where aerodynamic forces acting on flight control surfaces are often reproduced by an hydraulic servo-actuator suitably controlled by a dedicated software [15,16], while it is still rather uncommon for propulsion systems.…”

Low weight additive manufacturing FBG accelerometer: Design, characterization and testing

“…The designed FBG accelerometer should have a resonance frequency that allows its application to aerospace structures. Derkevorkian et al [53] measured natural frequencies of 2.4, 14.677, 41.096 and 80.530 Hz in an aluminium wing and Bertucci et al [54] studied a maximum frequency of 100 Hz for the dynamic characterization of helicopters primary flight control systems. Therefore, the objective of the present work was the design of an accelerometer to study a maximum frequency about 200 Hz.…”

Design of a Real-Time Test Bench for UAV Servo Actuators

“…In a publication of Braun 3 , a similar setup is described, however with a load application device identical to the aircraft actuator. A sophisticated approach for hydraulic actuators of helicopters can be found in the study of Bertucci 4 . The present work focuses on reproducing various rudder deflection scenarios and monitoring parameters such as applied mechanical torque and electric current.…”