Henry M. Paynter

Bond graph models of acoustical transducers

Abstract Pure circuit models of transducers have been used for many years with varying degrees of success. However, pure circuit models impose restrictions not all of which are predicated on laws of physics. These restrictions can produce transducer models which are nonphysical. Bond graph models offer an alternative that is less restrictive and thus better able to provide clear physical insight. We discuss the problem of pure circuit models of transducers and the advantages of bond graph approaches by examination of the special case of a piezoelectric transducer.

Dynamic Modeling and Simulation of Gaseous Systems

A computer-based model for analyzing air/gas system dynamics has been developed. A set of generic elements are interconnected by generalized junction structures to represent a variety of system configurations. The response of pressure, flow, temperature and heat transfer rate at any point or station in a system is then determined due to a wide range of fluid, thermal and mechanical disturbances. The model has been used to analyze furnace implosions in fossil fuel power plants. A coal-fired plant model has been constructed and simulated. The model simulations of the furnace pressure excursions are in close agreement with the data from the field tests.

Thermodynamic treatment of tug-&-twist technology. 2. Thermodynamic twistor design

For pt. 1 see Japan-USA Symposium on Flexible Automation, Boston, MA, USA, p.111-17. Various jointed-arm or jointed-leg robots called Arthrobots can use the new technical field variously called rubber-tronics or pneumo-elastics and designated here as tug-&-twist technology. By establishing an angular enthalpy analogous to the enthalpy developed in the first part for linear tension actuators (tuggers), a new class of twisters is conceived and constructed. A transforming transducer, in the form of a fluid-driven torsional device called a twister actuator, is used. Analysis for this device is based upon the application of thermodynamic principles and in particular, the use of this enthalpy function. Volume measurements then show that the thermodynamic treatment leads to an approximate model that predicts output torque taking into account the effect of shell stretch due to pressure.

The Differential Analyzer as an Active Mathematical Instrument: Control Applied to Mechanism and Circuitry

As part of a 1989 ACC Plenary Lecture, we feature here the essential role played by amplification and control in the successful development of the differential analyzer (DA). This first occurred with the introduction of the capstan torque amplifier in Vannevar Bushs largely mechanical form (as the 1930 MDA) and then later with use of the voltage operational amplifier in an electronic embodiment (as the 1947 EDA or electronic analog computer). Certain essential components and features of both MDAs and EDAs are outlined and contrasted, where the fast all-electronic EDA best exemplifies the distinctive benefits attending the evolution from mostly mechanical to fully electrical implementation.

Fool’s Paradise: The Wedding Dance of Physics and Control

This paper discusses the subtle interplay between physics and control guided by the metaphor of a marriage, with its wedding dance, shivaree and consummation. Physics is constrained by conservation, control, by causality. The revolutionary concept of a signal is the shotgun that forced the wedding.

Remarks on Riemann's method of characteristics

The method of Riemann characteristics has been used for more than a century to describe linear and nonlinear waves propagating in a medium. In this paper, the history of the method of characteristics is reviewed and examples of its use are provided. The useful properties of the method of characteristics are discussed, namely: that it may be applied to both linear and nonlinear systems; that it may be applied equally well to solids, liquids, and gases; and that it provides a clear picture of the causal relations governing system behavior. One‐dimensional wave propagation in uniform and nonuniform ducts and pipes is discussed in terms of the characteristics, and the importance of impedance scaling is shown. The use of characteristics when there is heat transfer is also discussed for a uniform duct.

Waves‐scatter bond graphs for electroacoustic systems

Electroacoustics was born as a twin to the telephone 110 years ago. Today electroacoustic transduction involves a sophisticated science and technology. Early in this evolution alternating currents and electrical oscillations were compared to the better‐understood mechanical vibrations, but electro‐technology advanced so rapidly that mechanical systems were soon treated conversely by analogous electrical circuits. Yet because a strict correspondence does not exist at the microscopic and continuum levels, several alternative analogies emerged so that now engineers confront a lack of uniform methodology, particularly when dealing with distributed transducers. Bond graphs were developed to meet just such needs by treating all physical systems as a set of multiport elements richly interconnected by another set of power bonds, which together enforce continuity‐conservation laws for mass, momentum, charge, and energies. Furthermore, to provide self‐consistent signal causality and detailed balances of power dissipation and entropy production, scattering variables can be employed at all ports, and wave variables on all bonds. Such characteristic variables and their methods of use were first introduced by Bernhard Riemann in 1860 for finite amplitude sound waves and later reintroduced in the 1940s for microwave circuitry. Some applications are given of this powerful approach to practical electroacoustical devices and systems.

Thermodynamic analysis of a mechatronic pneumatically driven spherical joint

Jointed-member robotic devices (Arthrobots) can benefit from the pneumatic tug-and-twist technology. In particular, two crossed Twistor-pairs provide a flexural spherical joint in the form of a Twistor gimbal-drive. Previous papers have shown that the performance characteristics of both Tuggers and Twistors may be derived from a unique appropriate enthalpy function, which results in open-loop proportional control. This paper develops the Twistor enthalpy H(P, /spl alpha/) based upon independent volume and torque measurements, which fully accounts for pressure-dependent Twistors stretch and Coulomb torque. This function then provides model equations for mechatronic computer-control of the final spherical joint.

The shortcomings of pure circuit models of transducers

Circuit models of transducers have been used for decades and have proven to be useful tools for prediction of transducer behavior. In this approach, the transduction mechanism is typically modeled using ideal two‐port transformers or gyrators that neither dissipate nor store energy. Energy loss and storage are taken into account using one‐port elements connected to the transducing gyrator or transformer. An alternative approach to transducer modeling recognizes that the transduction mechanism itself generally is associated with energy storage or dissipation. In this formulation, the transduction mechanism is typically modeled using a two‐port energic element (such as a two‐port capacitance). A comparison of the two formulations for piezoelectric transducers shows that there are two fundamental shortcomings introduced in the circuit model approach that are not present in the energic multiport element approach: The transformer modulus must be made a function of the strain of the piezoelectric material, and ...

Representation of Measured Ejector Characteristics by Simple Eulerian Bond Graph Models

Ejectors (or jet pumps) are highly reliable pure fluidic devices very commonly used in power plants, propulsion systems, petrochemical processes and other thermofluid systems. However, little off-design data has been available in a form suitable for dynamic simulation and control system design. Fortunately, concerns of the nuclear industry have recently led the Idaho National Engineering Laboratory (INEL) to obtain, from their LOFT Test Support facility, ejector test data sufficiently extensive to formulate a complete model accurately describing all flow conditions. Thus an elementary fixed-constant bond graph structure will approximate complete ejector characteristics, while a model only slightly more complex fits all INEL data within experimental scatter.