9.2.4 Variation Factors of Working Pressure
and Frequency Characteristics of System
(1) Influence Factors of Working Pressure
Steering gear system design is generally based on constant working pressure
and optimal conditions, which is rarely seen. Therefore, it is of great significance to analyze the working conditions of the system under changing pressures. The electro-hydraulic servo valve is the key component of the hydraulic
servo system. Its technical performance has a great influence on the whole
system. The transfer function of the servo valve is an approximate linear
analytical expression of the dynamic characteristics of the servo valve. The
actual dynamic characteristics of servo valves are related to many factors, such
as input signal amplitude, oil supply pressure, oil temperature, environment
temperature, load conditions, and so on. Valve coefficients are usually obtained
under the assumption of constant supply pressure. The actual working process
of aircraft steering system is a complex and changeable process. The unstable
factors of servo valve inlet pressure are as follows.
1. Changes in ballistic conditions and external loads;
2. Interaction between multiple parallel loops or subsystems;
3. The primary energy work is unstable, including power supply characteristics, high temperature of gas energy, low-temperature performance differences, variable characteristics of hydraulic pumps, and the decline of
volume efficiency in the working process;
4. The difference between the actual working point of relief valve and the
adjustment working point is the deviation of working point.
(2) Simulation results of amplitude–phase–frequency characteristics
Taking the fluctuation of working pressure as an example, the frequency
characteristics of the steering system are analyzed. Combining with the
dynamic technical indicators of frequency bandwidth under different working
pressures given in a servo valve sample, the three coefficients of the
electro-hydraulic servo valve are fitted in the range of working pressure
changing according to the actual operating conditions. Figure 9.42 shows the
simulation results of amplitude–phase–frequency characteristics of a steering
system under varying pressure. The coefficient of servo valve changes when the
working pressure of the system decreases, which results in the decrease of the
amplitude of the output frequency response. In the design of hydraulic steering
system, the output frequency characteristics should be guaranteed to meet the
practical requirements within the minimum allowable working pressure range.
122
9 High-Temperature and High-Speed Gas Turbine Pump …
and Frequency Characteristics of System
(1) Influence Factors of Working Pressure
Steering gear system design is generally based on constant working pressure
and optimal conditions, which is rarely seen. Therefore, it is of great significance to analyze the working conditions of the system under changing pressures. The electro-hydraulic servo valve is the key component of the hydraulic
servo system. Its technical performance has a great influence on the whole
system. The transfer function of the servo valve is an approximate linear
analytical expression of the dynamic characteristics of the servo valve. The
actual dynamic characteristics of servo valves are related to many factors, such
as input signal amplitude, oil supply pressure, oil temperature, environment
temperature, load conditions, and so on. Valve coefficients are usually obtained
under the assumption of constant supply pressure. The actual working process
of aircraft steering system is a complex and changeable process. The unstable
factors of servo valve inlet pressure are as follows.
1. Changes in ballistic conditions and external loads;
2. Interaction between multiple parallel loops or subsystems;
3. The primary energy work is unstable, including power supply characteristics, high temperature of gas energy, low-temperature performance differences, variable characteristics of hydraulic pumps, and the decline of
volume efficiency in the working process;
4. The difference between the actual working point of relief valve and the
adjustment working point is the deviation of working point.
(2) Simulation results of amplitude–phase–frequency characteristics
Taking the fluctuation of working pressure as an example, the frequency
characteristics of the steering system are analyzed. Combining with the
dynamic technical indicators of frequency bandwidth under different working
pressures given in a servo valve sample, the three coefficients of the
electro-hydraulic servo valve are fitted in the range of working pressure
changing according to the actual operating conditions. Figure 9.42 shows the
simulation results of amplitude–phase–frequency characteristics of a steering
system under varying pressure. The coefficient of servo valve changes when the
working pressure of the system decreases, which results in the decrease of the
amplitude of the output frequency response. In the design of hydraulic steering
system, the output frequency characteristics should be guaranteed to meet the
practical requirements within the minimum allowable working pressure range.
122
9 High-Temperature and High-Speed Gas Turbine Pump …