The application of a hybrid two-port model to teleoperators with force and velocity sensing at the master and slave is presented. The interfaces between human operator and master, and between environment and slave, are ports through which the teleoperator is designed to exchange energy between the operator and the environment. By computing or measuring the input-output properties of this two-port network, the hybrid two-port model of an actual or simulated teleoperator system can be obtained. It is shown that the hybrid model (as opposed to other two-port forms) leads to an intuitive representation of ideal teleoperator performance and applies to several teleoperator architectures. Thus measured values of the h matrix or values computed from a simulation can be used to compare performance with the ideal. The frequency-dependent h matrix is computed from a detailed SPICE model of an actual system, and the method is applied to a proposed architecture. >

A design framework for teleoperators with kinesthetic feedback

The dependence of muscle force on muscle length gives rise to a "spring-like" behavior which has been shown to play a role in the execution of single-joint posture and movement. This paper extends this concept and considers the influence of the apparent mechanical behavior of the neural, muscular and skeletal system on the control and coordination of multiple degree of freedom posture and movement.

A rigorous definition of "spring-like" behavior is presented. From it a numerically quantifiable, experimental test of spring-like behavior is formulated. It is shown that if the steady-state force-displacement behavior of a limb is not spring-like, this can only be due to the action of inter-muscular feedback, and can not be due to intrinsic muscle properties. The directional character of the spring-like behavior of a multiple degree of freedom system is described. The unique way in which synergistic coactivation of polyarticular muscles may modulate the directional properties of the spring-like behavior of a multiple degree of freedom system is explained.

Dynamic aspects of postural behavior are also considered. The concept of mechanical impedance is presented as a rigorous dynamic generalisation of the postural stiffness of the limb. The inertial behavior of the system is characterised by its mobility. As with the stiffness or impedance, in the multiple degree of freedom case it has a directional property. The way in which the apparent kinematic redundancy of the musculo-skeletal system may be used to modify its dynamic behavior is explained. Whereas the inertial behavior of a single limb segment is not modifiable, it is shown that the apparent inertial behavior of a multiple degree of freedom system may be modulated by repositioning the joints.

A unified description of the posture and movement of a multi-joint system is presented by defining a "virtual trajectory" of equilibrium positions for the limb which may be specified by the neuro-muscular system. The way in which this approach may lead to a simplification of some the apparent computational difficulties associated with the control of multi-joint motion is discussed.

The mechanics of multi-joint posture and movement control

Dynamic interaction with the environment is fundamental to the process of manipulation. This paper describes an approach to the design of ‘interaction controllers’ and contrasts this with an approa...

Robust control of dynamically interacting systems

The Ptolemy project studies heterogeneous modeling and design of concurrent systems. Th is on embedded systems , particularly those that mix technologies, including for example analog a digital electronics, hardware and software, and electronics and mechanical devices (including M microelectromechanical systems). The focus is also on systems that are complex in the sense t mix widely different operations, such as signal processing, feedback control, sequential decision ing, and user interfaces. Modelingis the act of representing a system or subsystem formally. A model might be mathe cal, in which case it can be viewed as a set of assertions about properties of the system such as tionality or physical dimensions. A model can also be constructive, in which case it defin computational procedure that mimics a set of properties of the system. Constructive models ar used to describe behavior of a system in response to stimulus from outside the system. Cons models are also called executable models. Designis the act of defining a system or subsystem. Usually this involves defining one or m models of the system and refining the models until the desired functionality is obtained within a constraints. Design and modeling are obviously closely coupled. In some circumstances, models m immutable, in the sense that they describe subsystems, constraints, or behaviors that are ex imposed on a design. For instance, they may describe a mechanical system that is not under des must be controlled by an electronic system that is under design. Executable models are sometimes called simulations, an appropriate term when the executab model is clearly distinct from the system it models. However, in many electronic systems, a mode starts as a simulation mutates into a software implementation of the system. The distinction be the model and the system itself becomes blurred in this case. This is particularly true for emb software.

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Overview of the Ptolemy project

We describe an ontology for mathematical modeling in engineering. The ontology includes conceptual foundations for scalar, vector, and tensor quantities, physical dimensions, units of measure, functions of quantities, and dimensionless quantities. The conceptualization builds on abstract algebra and measurement theory, but is designed explicitly for knowledge sharing purposes. The ontology is being used as a communication language among cooperating engineering agents, and as a foundation for other engineering ontologies. In this paper we describe the conceptualization of the ontology, and show selected axioms from definitions. We describe the design of the ontology and justify the important representation choices. We offer evaluation criteria for such ontologies and demonstrate design techniques for achieving them.

An ontology for engineering mathematics

From the Publisher:
The SYSKIT is a linear system software toolkit that contains a highly integrated set of programs with applications to system dynamics,controls and vibrations. It includes file management,a time processor for eigenvalue and time response,a conversion module for vibrations,a frequency domain module for frequency response and root locus,and output display modules for time,frequency,and root locus data.

R. Robert Rosenberg

Papers

Introduction to physical system dynamics