Engineering topics

Stewart, Elwood C.

Publications and source records attributed to Stewart, Elwood C..

4 records

NASA NTRS1961

An Explicit Linear Filtering Solution for the Optimization of Guidance Systems with Statistical Inputs

The determination of optimum filtering characteristics for guidance system design is generally a tedious process which cannot usually be carried out in general terms. In this report a simple explicit solution is given which is applicable to many different types of problems. It is shown to be applicable to problems which involve optimization of constant-coefficient guidance systems and time-varying homing type systems for several stationary and nonstationary inputs. The solution is also applicable to off-design performance, that is, the evaluation of system performance for inputs for which the system was not specifically optimized. The solution is given in generalized form in terms of the minimum theoretical error, the optimum transfer functions, and the optimum transient response. The effects of input signal, contaminating noise, and limitations on the response are included. From the results given, it is possible in an interception problem, for example, to rapidly assess the effects on minimum theoretical error of such factors as target noise and missile acceleration. It is also possible to answer important questions regarding the effect of type of target maneuver on optimum performance.

Stewart, Elwood C.↗

NASA NTRS1959

The Synthesis of Optimum Homing Missile Guidance Systems with Statistical Inputs

An analytical approach is presented which is applicable to the optimization of homing navigation guidance systems which are forced to operate in the presence of radar noise. The two primary objectives are to establish theoretical minimum miss distance performance and a method of synthesizing the optimum control system. The factors considered are: (1) target evasive maneuver, (2) radar glint noise, (3) missile maneuverability, and (4) the inherent time-varying character of the kinematics. Two aspects of the problem are considered. In the first, consideration is given only to minimization of the miss distance. The solution given cannot be achieved in practice because the required accelerations are too large. In the second, results are extended to the practical case where the limited acceleration capabilities of the missile are considered by placing a realistic restriction on the mean-square acceleration so that system operation is confined to the linear range. Although the exact analytical solution of the latter problem does not appear feasible, approximate solutions utilizing time-varying control systems can be found. One of these solutions - a range multiplication type control system - is studied in detail. It is shown that the minimum obtainable miss distance with a realistic restriction on acceleration is close to the absolute minimum for unlimited missile maneuverability. Furthermore, it is shown that there is an equivalence in performance between the homing and beam-rider type guidance systems. Consideration is given to the effect of changes in target acceleration, noise magnitude, and missile acceleration on the minimum miss distance.

Stewart, Elwood C.↗

NASA NTRS1959

The Effects of Target and Missile Characteristics on Theoretical Minimum Miss Distance for a Beam-Rider Guidance System in the Presence of Noise

A study has been made to determine the relative importance of those factors which place an inherent limitation on the minimum obtainable miss distance for a beam-rider navigation system operating in the presence of glint noise and target evasive maneuver. Target and missile motions are assumed to be coplanar. The factors considered are the missile natural frequencies and damping ratios, missile steady-state acceleration capabilities, target evasive maneuver characteristics, and angular scintillation noise characteristics.

Stewart, Elwood C.↗

NASA NTRS1950

Dynamic Response of Control Servo System Installed in NAES-Equipped SB2C-5 Airplane (BuAer No. 83135)

Dynamic--response measurements for various conditions of displacement and rate signal input, sensitivity setting, and simulated hinge moment were made of the three control-surface servo systems of an NAES-equipped remote-controlled airplane while on the ground. The basic components of the servo systems are those of the General Electric Company type G-1 autopilot using electrical signal. sources, solenoid-operated valves, and hydraulic pistons. The test procedures and difficulties are discussed, Both frequency and transient-response data, are presented and comparisons are made. The constants describing the servo system, the undamped natural frequency, and the damping ratio, are determined by several methods. The response of the system with the addition of airframe rate signal is calculated. The transfer function of the elevator surface, linkage, and cable system is obtained. The agreement between various methods of measurement and calculation is considered very good. The data are complete enough and in such form that they may be used directly with the frequency-response data of an airplane to predict the stability of the autopilot-airplane combination.

Smaus, Louis H.↗