ME2142
ME2142-1 FREQUENCY RESPONSE
(Formal Report)
2012/2013
Department of Mechanical Engineering
National University of Singapore
Name : Sim Jing Yu (A0071187A) Group : 3L1 Date : 09/09/2012
Objective
To determine the phase and gain margins of the servo by performing a frequency response test on an aircraft electro-hydraulic servo-actuator
To verify that increasing the gain causes instability
Introduction
The servo system comprises a servo-actuator and an amplifier unit. A similar system is used in aircrafts to add autopilot outputs (electrical) as mechanical movement into the control rods, which connects the pilot’s stick to the aircraft control surfaces (elevators, fins etc.). The unit receives a voltage input and is required to realize a mechanical movement proportional to that input voltage. Since a considerable force is required a hydraulic servo is used. Generally the time delay to change the output position should be minimal but the response should not oscillate. These specifications usually determine the gain (or attenuation) and phase angle at some frequency. The servo-actuator is shown in Fig. 1 and the amplifier unit is shown in Fig. 2. To permit the loop gain to be varied, the feedback resistor of the amplifier is connected externally.
Note that the motor is driven in a push-pull manner. The motor has a continuous current flowing through it with a LVDT with it. When an error signal is detected, the current increases in one coil and decreases in the other: The net differential current causes the motor to move.
The servo-actuator consists of four parts:
(i) a servo motor )
(ii) a valve spool ) all within the main body
(iii) an actuator )
(iv) a linear potentiometer which is attached alongside the main body.
As the motor is moved by the input signal it tends to block one
(Formal Report)
2012/2013
Department of Mechanical Engineering
National University of Singapore
Name : Sim Jing Yu (A0071187A) Group : 3L1 Date : 09/09/2012
Objective
To determine the phase and gain margins of the servo by performing a frequency response test on an aircraft electro-hydraulic servo-actuator
To verify that increasing the gain causes instability
Introduction
The servo system comprises a servo-actuator and an amplifier unit. A similar system is used in aircrafts to add autopilot outputs (electrical) as mechanical movement into the control rods, which connects the pilot’s stick to the aircraft control surfaces (elevators, fins etc.). The unit receives a voltage input and is required to realize a mechanical movement proportional to that input voltage. Since a considerable force is required a hydraulic servo is used. Generally the time delay to change the output position should be minimal but the response should not oscillate. These specifications usually determine the gain (or attenuation) and phase angle at some frequency. The servo-actuator is shown in Fig. 1 and the amplifier unit is shown in Fig. 2. To permit the loop gain to be varied, the feedback resistor of the amplifier is connected externally.
Note that the motor is driven in a push-pull manner. The motor has a continuous current flowing through it with a LVDT with it. When an error signal is detected, the current increases in one coil and decreases in the other: The net differential current causes the motor to move.
The servo-actuator consists of four parts:
(i) a servo motor )
(ii) a valve spool ) all within the main body
(iii) an actuator )
(iv) a linear potentiometer which is attached alongside the main body.
As the motor is moved by the input signal it tends to block one