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AWARDS

J. Dyn. Sys., Meas., Control. 1980;102(2):53-58. doi:10.1115/1.3149595.
FREE TO VIEW

“In recognition of his creative accomplishments in all aspects of dynamic systems theory and practice, his inspiring example to students and colleagues, and his supreme enthusiasm. His accomplishments include, but are hardly limited to, innovations in fluid transmission line and fluid transient theory, seminal contributions to analog, digital and hybrid simulation methodology, and development of an integrated notational and computational framework for energetic systems (bond graphs).”

Commentary by Dr. Valentin Fuster

TECHNICAL FORUM

J. Dyn. Sys., Meas., Control. 1980;102(2):59-60. doi:10.1115/1.3149596.
Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):60-61. doi:10.1115/1.3149597.
Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Dyn. Sys., Meas., Control. 1980;102(2):62-68. doi:10.1115/1.3149598.

The demand for increased productivity of welding operations has led to the expanded use of computer control to allow higher production rates while maintaining weld quality. The charateristics of the gas metal arc welding process and the relationship between welding parameters, the desired output of the welding process, and the automation of the process are discussed. A strategy for two-axis welding torch positioning and velocity control is developed based on preview control techniques. To evaluate the applicability of the proposed control method the motion of heat source along different welding paths is simulated on an analog computer with on-line control of process time constants by an LSI-11 microcomputer. The simulation results show that high quality seam tracking can be accomplished by controlling the torch motion using the proposed method. The method appears to be suitable for on-line control of welding processes.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):69-76. doi:10.1115/1.3149599.

Industrial robots are mechanical manipulators whose dynamic characteristics are highly nonlinear. To control a manipulator which carries a variable or unknown load and moves along a planned path, it is required to compute the forces and torques needed to drive all its joints accurately and frequently at an adequate sampling frequency (no less than 60 Hz for the arm considered). This paper presents a new approach of computation based on the method of Newton-Euler formulation which is independent of the type of manipulator-configuration. This method involves the successive transformation of velocities and accelerations from the base of the manipulator out to the gripper, link by link, using the relationships of moving coordinate systems. Forces are then transformed back from the gripper to the base to obtain the joint torques. Theoretically the mathematical model is “exact”. A program has been written in floating point assembly language which has an average execution time of 4.5 milliseconds on a PDP 11/45 computer for a Stanford manipulator. This allows an on-line computation within control systems with a sampling frequency no lower than 60 Hz. A further advantage of using this method is that the amount of computation increases linearly with the number of links whereas the conventional method based on Lagrangian formulation increases as the quartic of the number of links.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):77-84. doi:10.1115/1.3149600.

The problem of designing longitudinal control systems which provide acceleration and jerk limited response for automated vehicle systems is examined. Non-dimensional models of vehicles propelled by d-c traction motors are used to evaluate the feasibility of the model-reference control concept. Analytical and computer simulation techniques are used to evaluate performance and assure critical string behavioral characteristics - asymptotic string stability and fixed end-point speed transition region (proper curve negotiation).

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):85-93. doi:10.1115/1.3149601.

A method is presented which permits the simulation of the coupled lateral-vertical rigid body vibration response of a rubber-tired automated guideway transit (AGT) vehicle subject to guideway random irregularities. A coupled lateral-vertical dynamic model is developed. The general motions are expressed by Euler angles and inertial displacements. Basic vehicle dynamic modes are determined. A predicted lateral acceleration spectrum of the linearized model using guideway surface profile models for inputs are compared with the measured lateral acceleration spectra and found to agree reasonably well in the lower frequency (below about 7 Hz) range. Good agreement was found to exist between the predicted and measured root mean square (rms) accelerations for a wider range of frequencies.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):94-100. doi:10.1115/1.3149602.

Bond graphs are used for finite mode representations of distributed system dynamics. As long as all inputs to the system are “efforts” in a causal sense, then no formulation problems exist. However, if some of the system inputs are causal “flows”, then differential causality will exist and extremely tedious, often impossible, algebraic loops must be solved to formulate system equations. A procedure is developed which avoids these algebraic problems by including additional modal compliance in the system model without its associated modal inertia. The result of this approach is a finite mode distributed system model, devoid of artificially induced high frequencies, extremely accurate in a chosen frequency range, and capable of interacting with other distributed system models. The procedure is demonstrated through example.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):101-105. doi:10.1115/1.3149587.

Auxiliary signals which are proportional to the tracking error between the process and identifier outputs are introduced into the s eries-p arallel (SP) identifier [1-2]. The coefficients of these auxiliary signals are updated at each computational cycle. The asymptotic hyperstability of the resulting SP identifier with variable relaxation gains is proved theoretically and demonstrated experimentally. Computational considerations for implementing SP identifiers are noted and the on-line computational requirements of the two SP identifiers are then compared.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):106-113. doi:10.1115/1.3149588.

A process of condensation is used to develop a geometric programming approach to the necessary conditions for a constrained optimum in an elementary way. Special features of geometric programming not found in other optimization procedures and which offer significant advantages in the design of optimum compensators are developed. Compensator design is formulated as an optimum pole placement problem subject to a time delay response constraint. The geometric programming approach results in simple explicit equations for the optimum compensator parameters.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):114-122. doi:10.1115/1.3149589.

Whistling is a self-excited transverse instability that produces intense noise at a resonant frequency of a circular saw. Experiments were undertaken to examine the noise source dependence upon tooth shape, tooth number, rotation speed and the surrounding air pressure. The source model supported by the data is a self excited fluid-structure instability possibly with a wake oscillation sustained or enhanced by the blade motion.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):123-129. doi:10.1115/1.3149590.

Severity of the skiing environment can be interpreted only through the response of the lower extremity to the excitation of the environment. Identification of a linear, four degree of freedom, lower extremity ski torsion model was undertaken. A new procedure is introduced for filtering the deterministic trends from the random torsion data measured between the boot and ski during skiing. Trend removal is necessary for identification. The objective function for the identification was the square of the difference between the spectrum of the trend-removed torsion data and the spectrum of the model torsion. Following identification, the model responses predicted during two authentic skiing falls were computed, thus permitting a comparison of their relative severity.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 1980;102(2):130-135. doi:10.1115/1.3149591.

Evaporators controlled by a thermostatic expansion valve can exhibit an undesirable oscillating behavior, known as hunting. The equations describing the hunting can be characterized by an open-loop transfer function, the coefficients of which are the physical parameters of a refrigeration system. Several known experimental facts are explained theoretically by means of this transfer function, which also provides a starting point for finding new methods to improve the behavior. A particular improvement was verified experimentally.

Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. Dyn. Sys., Meas., Control. 1980;102(2):136-137. doi:10.1115/1.3149592.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

DISCUSSIONS

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