This paper addresses the stability problem of pump controlled asymmetric hydraulic actuators and proposes a physical solution for it. The system under consideration utilizes a shuttle valve to compensate for unequal flow rates due to the asymmetry in the actuator. Possible hydraulic circuit configurations resulting from various valve positions are defined on the load pressure versus velocity plane and a generalized linear model of the system is derived. The investigation shows that there exists a critical load pressure region in which any equilibrium point requiring a partially open spool position is unstable during the retraction of the actuator. A particular valve underlap is proposed in order to avoid the instability and a shuttle valve selection guide is presented. Theoretical findings are validated by both numerical simulations and experimental tests. Results show that the undesired pressure oscillations are removed up to certain actuator velocities with the use of an underlapped shuttle valve.

The main area of emphasis in this paper is to investigate the methods and technology for aerodynamic configuration sizing of missiles and to develop a software platform in MATLAB® environment as a design tool which has an ability of optimizing the external configuration of missiles for a set of flight requirements specified by the user through a graphical user interface. A genetic algorithm based optimization tool is prepared by MATLAB® that helps the designer to find out the best external geometry candidates in the conceptual design stage. Missile DATCOM is employed as the aerodynamic coefficient prediction package to determine aerodynamic coefficients of each external geometry candidate in finding their performance merits by integrating their dynamic equations of motion. Numerous external geometry candidates are rapidly eliminated according to objectives and constraints specified by designers, which provide necessary information in preliminary design. In this elimination, the external geometry candidates are graded according to their flight performances in order to discover an optimum solution. All of the flight performance data are obtained by running a two degree-of-freedom simulation in the vertical plane. In order to solve the resulting multi-objective optimization problem with a set of constraint of linear and nonlinear nature and in equality and inequality forms, geneticalgorithm-based methods are applied. Hybrid encoding methods in which the integer configuration variables (i.e., nose shape and control type) and real-valued geometrical dimension (i.e., diameter, length) parameters are encoded in the same individual chromosome. An external configuration design tool (EXCON) is developed as a synthesis and external sizing tool for the subsonic cruise missiles. A numerical example, the reconfiguration problem of an anti-ship cruise missile, is presented to demonstrate the accuracy and feasibility of the conceptual design tool.

In this study, a valveless energy saving hydraulic position control servo system controlled by two pumps is investigated. In this system, two variable speed pumps driven by servomotors regulate the flow rate through a differential cylinder according to the needs of the system, thus eliminating the valve losses. The mathematical model of the system is developed in MATLAB Simulink environment. A Kalman filter is applied to reduce the noise in the position feedback signal. In the test set up developed, open loop and closed loop frequency response and step response tests are conducted by using MATLAB Real Time Windows Target (RTWT) module, and test results are compared with the model outputs.

This paper describes the application of the equation error method to aerodynamic parameter estimation of a gliding flight vehicle. The flight test data used is not originally designed for estimation, causing data collinearity. A strategy is devised to deal with this situation so that the model identification and parameter estimation can be performed. A computer tool is developed in Matlab ® environment for the flight test data processing and aerodynamic identification/estimation. The results of the study show that, although the stepwise regression and equation error method have some potential to be used for flight vehicles other than aircraft, the quality of the flight test data and input design is crucial for aerodynamic parameter identification.

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