Session: 07-03-02: Design and Control of Robots, Mechanisms and Structures

Paper Number: 94779

94779 - Performance Evaluation of a Helicopter Main Rotor Hydraulic Control System Using Rotor Equivalent Dynamic Parameters 

Hydraulic control systems are commonly used in helicopter main rotor control applications to provide necessary lifting and maneuvering capability under varying environmental conditions because of agility of the system and operational capability under heavy loads. It is significant to obtain better performance from hydrauli control system to ease the helicopter control as increasing the sensitivity of the system. In this study, a complete helicopter main rotor hydraulic control system is modeled by using MATLAB/Simulink to simulate system responses. Kinematic model of helicopter input are obtained. Hydraulic control systems are operated towards two significant effects that are transmitted from from rotor systems, aerodynamic loads and inertial effects. Aerodynamic loads arise as a result of change in the pitch angles of the blades and flows through flight control actuators through blade and swashplate assemblies. Inertial loads are due to inertia of the rotor assembly because it has a consideable heavier assembly compared to actuator system. Hydraulic control system opposes these forces while changing the orientation of the assembly at the same time. To demonstrate the effect of the flight control actuator and inspect frequency response, rise  time and peak time parameters for the actuator, hydraulic interface of a flight control actuator is obtained. There are three types of input that can be given to flight control actuators that transmit piston output to stationary swashplate which determines the pitch angles of each blade depending on the rotation angle of the rotating swashplate component. Main rotor swashplate which has Pitch, Roll and Vertical motion degrees of freedom is used to change pitch angles of rotor blades independent from each other and depending on the angle of the rotation. Pitch (alpha) and Roll (beta) angle of stationary swashplate is obtained. Finally, 4 degrees of freedom rotor equivalent model is obtained. Effect of spring and damping coefficients of swashplate assembly is demonstrated. To enhance the overall performance of the control system, a P and PI controllers are developed. System responses are inspected in two stages. First, frequency response and phase lag of the system are observed under sinusoidal pilot input for both pitch and roll movement of the swashplate assembly. Next, Rise Time and Peak Time of the system are observed under step pilot input. It is concluded that adding a proportional controller to common feedback controller enhances the performance of the hydraulic system hugely. All performance parameters are tabulated and compared at the end of the analysis. 

Presenting Author: Hasan Ali Düzagaç Middle East Technical University

Presenting Author Biography: Graduated from Bogazici University Mechanical Engineering Department. Currently a Master's Degree student in Middle East Technical University in Mechanical Engineering at the Thesis stage. The thesis topic is "Design and Evaluation of a Helicopter Main Rotor Electrohydraulic Control System". Current working as a Hydraulic Control System Design Engineer in Turkish Aerospace Helicopter Vice Predicency for 3 years. Responsible from design and implementation of hydraulic power system components such as hydraulic pump, reservoir, filter modules, valves. Implementation of flight control actuators, landing gear actuators, wheel brake hydraulic components and main rotor hydraulic dampers. Following the test activities, certification and qualification process. Involving helicopter level flight tests to evaluate overall performance o hydraulic control systems.

Authors:

Hasan Ali Düzagaç Middle East Technical University
Hakan Calıskan Middle East Technical University
Raif Tuna Balkan Middle East Technical University