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TECHNICAL FORUM

J. Dyn. Sys., Meas., Control. 1973;95(1):1-2. doi:10.1115/1.3426643.
Abstract
Topics: Algorithms
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):2-3. doi:10.1115/1.3426646.
Abstract
Commentary by Dr. Valentin Fuster

AWARDS

J. Dyn. Sys., Meas., Control. 1973;95(1):6. doi:10.1115/1.3426653.
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Abstract
Commentary by Dr. Valentin Fuster

PROFILES

J. Dyn. Sys., Meas., Control. 1973;95(1):7-9. doi:10.1115/1.3426655.
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Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Dyn. Sys., Meas., Control. 1973;95(1):10-16. doi:10.1115/1.3426641.

The bits of history are in the recorder/controller field and each bit of history is strictly from the author’s limited view like the prairie dog’s view of the prairie. Although some of the bits pertain to work which had subsequent impact in the field, several of the bits have been selected for inclusion simply because the author has a vivid recollection (in each case) of solving a problem, which he then thought was important.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):17-23. doi:10.1115/1.3426642.

The concept of fuzzy dynamic programming and of guaranteed cost control initiated by Chang is applied to the inverse problem of guaranteed cost control for linear systems containing uncertain parameters. Obtained, for a class of linear systems with uncertain parameters, is a frequency-domain criterion which, analogous to that for the deterministic system, is sufficient for the control law to be of guaranteed cost type. The author presents an iterative method which, if convergent, enables one to solve the inverse problem for the general linear systems.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):24-27. doi:10.1115/1.3426644.

This paper investigates the proper selection of a performance index to satisfy a word statement of desired effect. A performance index formed as the time integral of Un is solved for various values of n. When viewed in this light, the classical quadratic index (n = 2) gives a seemingly arbitrary solution. From this investigation the true optimal control solution can be ascertained. For the different values of n, solutions for totally different performance can be obtained. Performance indices combining two effects of minimum control effort and minimum response error are also investigated. The differences of a summed combination and a multiplicative combination are studied.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):28-35. doi:10.1115/1.3426645.

The nonlinear equations of motion for a railway vehicle wheelset having curved wheel profiles and wheel-flange/rail contact are presented. The dependence of axle roll and vertical displacement on lateral displacement and yaw is formulated by two holonomic constraint equations. The method of Krylov-Bogoliubov is used to derive expressions for the amplitudes of stationary oscillations. A perturbation analysis is then used to derive conditions for the stability characteristics of the stationary oscillations. The expressions for the amplitude and the stability conditions are shown to have a simple geometrical interpretation which facilitates the evaluation of the effects of design parameters on the motion. It is shown that flange clearance and the nonlinear variation of axle roll with lateral displacement significantly influence the motion of the wheelset. Stationary oscillations may occur at forward speeds both below and above the critical speed at which a linear analysis predicts the onset of instability.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):36-43. doi:10.1115/1.3426647.

The paper is concerned with determination of the state components in the case of measurements of output and control signals of the plant with errors. The optimal operators have been considered, which in the case of least favorable measurement errors give a minimal value of error of component to be defined. Particularly a case of signal measurement with errors which differ from each other has been considered. It has been shown that optimal operators are certain linear operators. The way of selecting these optimal operators from linear operators has been also shown. Namely it has been proved that for all cases which are considering the so called mini-max principle preserve its validity. Other theorems which can help to select optimal operators are formulated.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):44-48. doi:10.1115/1.3426648.

The negative-inertia mechanism consists of a double-worm drive with a small flywheel attached to the output shaft. By connecting the drive in parallel with the servo load, very high deceleration rates can be obtained. The drive thus effectively cancels most of the load inertia, as long as the load is decelerated. During acceleration, the drive adds slightly to the original load inertia. Characteristic design equations of the system are described, and experimental results presented. The drive is intended mainly for velocity servos, where very high decelerating torques are required without using clutch-brake mechanisms or excessively large servomotors.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):49-54. doi:10.1115/1.3426649.

An approach for the computer simulation of nonlinear multiport systems is presented. Bond graph techniques are utilized in the development. The objective of the formulation is to derive a system of mixed first-order differential/algebraic equations, whose solution is facilitated by approximating the derivatives by a linear combination of the present and several previous solution points. Thus the original system of equations is converted to a system of implicit nonlinear algebraic equations which are solved by a Newton iteration procedure. The formulation procedure lends itself to mechanization similar to ENPORT. Computational results from an illustrative example show the method to be excellent in speed and accuracy relative to other simulation approaches.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):55-63. doi:10.1115/1.3426650.

A work is described which studied the capabilities of a STOL aircraft equipped with digital minicomputer serving as an autopilot making a curved approach to a runway along a path prescribed by the Air Traffic Control system using radio-navigation data supplied by the developing Scanning Fan Beam Microwave Landing Guidance System. The work involved the development of an ATC scheme for effectively generating a flyable curved approach path and specifying such a path to the aircraft being served. The paths produced are made up of alternating straight and circular segments along which the plane is to maintain prescribed constant airspeeds. The digital autopilot functions include Navigation, Control Trimming, Anticipatory calculations, Generation of Control Commands based on utilization of linear optimal state-feedback control theory, Filtering (including Kalman techniques) of state measurements, and Estimation of prevailing winds. A complete simulation of such a system aboard a McDonnell-Douglas 188/Breguet 941 STOL transport, with realistic winds, turbulence, and measurement noise, was created and exercised on the Purdue University CDC 6500 computer system, and showed the capability of excellent adhesion of the airplane to the commanded flight path.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):64-67. doi:10.1115/1.3426651.

This paper is concerned with linear distributed parameter systems whose input-output operators are representable in integral form. Two types of control are considered: (i) distributed control which is a function of both a spatial variable x (lying in a compact set Ω) and a time variable t, and (ii) “point” control which is applied at a specific point in Ω and is a function only of t. For such systems, a basic theorem is stated and proved, namely, that there exists a countable subset E of Ω with the following property: any state which can be attained by applying a distributed control can also be attained arbitrarily closely by applying a finite number of point controls applied at points in the set E. The theorem is applied to some specific systems, and further possible applications of the theorem are discussed.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):68-75. doi:10.1115/1.3426652.

This paper is concerned with the basis for thermoregulation under conditions of thermodynamic equilibrium. The thermoregulatory system can in principle only be understood through an appropriate integration of its physical, chemical, physiological and neurological aspects. The common description of thermoregulation simply as a hypothalamic “feedback” control of a servomechanical “set point” has not led to an adequate self-contained model. Review of steady-state data (nude, resting human, low wind and humidity, 5–45 deg C ambient temperature Ta ) indicates that, at the very least, there are physical-physiological aspects of thermoregulation not explained by a hypothalamic set point model. Rather, we can point to a wide spectrum of cyclic “thermodynamic engine” processes which regulate the various subsystems of the body [1]. The cooperative orchestration of all these processes produces a dynamic regulation of temperature, essentially as a self-regulation. This dynamic regulation produces an overall thermal equilibrium for the entire body. To illustrate some unresolved equilibrium problems: Reported mean skin temperatures T s versus Ta are incompatible with the physically determined skin-to-air transfer coefficient of about 7 kcal/m2 /hr/deg C. At low Ta , either mean metabolism M must be higher or T s must be lower, or the physical conductance must be rejected. One experimental test suggests that T s is lower than commonly quoted (e.g., T s = 26 deg C instead of 30 deg C at Ta = 20 deg (C). Such discrepancies may arise if free convective transfer is suppressed or if experiments are not carried on to equilibrium. Change in metabolism, heat storage, and tissue temperature may be significant for several hours, requiring at least 3 hours of sample data for accurate equilibrium temperature measurements. At low Ta , there is no solid evidence for metabolic regulation; in the cold, equilibrium M rises only 20–30 percent, not 200–300 percent as proposed by some workers. At high Ta , the usual definition of mean tissue conductance [C = M/(Tc − T s )] leads to nonphysically large C as T s approaches deep body temperature Tc . This paper is restricted to the physiological-physical modeling of the regulation of a variety of coupled fluxes (e.g., oxidative metabolism, evaporative flux, free and forced convective flux, fluid heat exchange) and potentials (e.g., internal and surface temperatures, evaporative phase changes). To resolve the foregoing difficulties we offer two hypotheses: (a) the body autoregulates a vital core; peripheral regions cool, e.g., extremity Ts drops toward ambient, the regulated core “contracts” longitudinally; (b) a significant portion of the evaporative heat loss may occur below the skin’s surface. Adjustment of two parameters emerging from these hypotheses allows a consistent modeling of steady-state thermoregulation. We suggest that hypothalamic control is one component of regulation and operates at higher frequency (with 7-min period) than steady-state autoregulation (3-hr period).

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):76-85. doi:10.1115/1.3426654.

The vehicle-guideway system is modeled as an arbitrary number of lumped, doubly-sprung vehicle mass systems traveling in tandem along simple supported beams. The vehicle load is transmitted to the guideway as a time-varying uniform pressure compatible with vehicle motion. Effects of the dimensionless system parameters on vehicle heave acceleration, and guideway deflections and bending moments at high vehicle speeds are evaluated. Results for a vehicle which includes pitching motion compare favorably with those for a vehicle without pitch where the front and rear masses are uncoupled. By proper choice of parameters, passenger compartment heave accelerations can be minimized, although to keep this acceleration below 0.05g for vehicles traveling 100–300 mph requires systems with low vehicle to beam mass and frequency ratios as well as low vehicle lower to upper mass ratios. The benefits of distributed air cushion pressure to vehicle and guideway design are shown. Also, if the ratio of lower to upper vehicle mass is low, a constant moving pressure conservatively predicts the guideway response.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):86-91. doi:10.1115/1.3426656.

Two means of providing a high quality air cushion ride at high speed using simple passive suspension systems are investigated. The inclusion of the proper amount of camber in guideway beams is shown to greatly reduce both low and high speed heave accelerations. A three-stage passively suspended vehicle including two degrees of pitching motion is shown to eliminate the high speed peak in accelerations present with two-stage vehicles. The effects of secondary and tertiary damping, of the vehicle to span length ratio, and of guideway camber on the ride quality of this vehicle are investigated. Coupled with cambered guideway beams, the three-stage passive suspension system appears to be an attractive alternative to active suspension systems.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Dyn. Sys., Meas., Control. 1973;95(1):92-96. doi:10.1115/1.3426657.

This article describes the results of a questionnaire survey taken within the last two years of the state of control education in university mechanical engineering departments. The results of the analysis showed in general that control per se is not regarded as a subject of singular importance in engineering curricula. For instance, 13.25 percent of the replies indicated no control courses at the undergraduate level; 42.1 percent of the replies indicated control as an elective, and 42.16 percent as a required undergraduate course; and 44.5 percent replied with no control laboratory. Use of computers, however, was very common (77.1 percent teaching analog and digital computation, 6 percent teaching digital only, and 0 percent teaching analog only). Details of courses and texts were solicited. It was found that most departments do not offer graduate courses in control, most having less than five masters and less than three doctoral students.

Commentary by Dr. Valentin Fuster

BIBLIOGRAPHIES

J. Dyn. Sys., Meas., Control. 1973;95(1):97-99. doi:10.1115/1.3426658.
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Abstract
Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. Dyn. Sys., Meas., Control. 1973;95(1):100. doi:10.1115/1.3426628.
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Abstract
Topics: Circuit design
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):100. doi:10.1115/1.3426629.
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Abstract
Topics: Equations
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):100-101. doi:10.1115/1.3426632.
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Abstract
Topics: Dynamic systems
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):101. doi:10.1115/1.3426633.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):102. doi:10.1115/1.3426635.
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Abstract
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):102. doi:10.1115/1.3426636.
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Abstract
Topics: Probability
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):102-103. doi:10.1115/1.3426637.
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Abstract
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):103. doi:10.1115/1.3426638.
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Abstract
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):103-104. doi:10.1115/1.3426639.
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Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1973;95(1):104. doi:10.1115/1.3426640.
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Abstract
Topics: Control systems
Commentary by Dr. Valentin Fuster

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