Bayliss C. McInnis

Adaptive Control of Blood Pressure

Stochastic adaptive controllers have been developed for automatic control of blood pressure during infusions of cardiostimulatory or vasoactive drugs. An adaptive algorithm based upon a minimum variance control law is presented. A more advanced algorithm obtained by augmenting the performance measure to include the rate of charge of the control signal is also presented. An autoregressive-moving-average (ARMA) model, representing the dynamics of the system, and a recursive least-squares parameter estimation technique are used for both algorithms. A series of experiments was performed in dogs, utilizing an electronically activated drug infuser. Stable control was achieved, even when the circulatory state of the animal underwent major changes, using either algorithm. On the basis of theoretical considerations and experimental results, we expect that these adaptive controllers will significantly improve the performance of drug infusion systems in clinical applications.

Technical communique: Adaptive control and identification of the dissolved oxygen process

This paper suggests how nonlinear adaptive control might lead to improved control of the dissolved oxygen (DO) concentration in the aerator of a wastewater treatment plant. The DO dynamics can be represented by a bilinear model for which we are interested in both parameter identification and control. The estimation of key parameters of the process model is important because the values of these parameters cannot be obtained from direct measurement. Hence a least-squares procedure for obtaining unique parameter estimates is developed and then combined with a minimum variance control algorithm to obtain an adaptive controller which is used both to generate useful parameter estimates and to control the process. Extensions to the case where the parameters vary at the same rate as the DO are also discussed.

Model reference adaptive control for systems having non-square transfer functions

This paper describes algorithms for model reference adaptive control of systems having non-square transfer functions. The motivation for this study was a problem related to the control of an artificial heart having 3 outputs and 2 inputs. The paper treats the case where the number of inputs is greater than or less than the number of outputs. The adaptive control algorithms developed here are shown to be globally convergent provided a subset of the parameters is projected into a suitably defined convex region. This is a natural generalization of procedures used in the single-input single-output case.

On stochastic compartmental modeling

This communication contains a proof of the fact that the coefficient of variation of the contents of a compartment of a stochastic compartmental model with deterministic rate parameters is small for large populations. We can therefore conclude that the use of stochastic compartmental models is not of great consequence in the case of systems involving large populations when only the randomness of the transfer mechanism is considered.

Division and sign detection algorithms for residue number systems

Abstract This paper is concerned with the operations of division and sign detection in residue number systems. CORDIC, a well-known iterative algorithm originally designed for conventional floating point representation, is adapted for residue division. Since sign detection is required by the division algorithm we have also considered this problem. A modified sign detection algorithm which yields a high degree of parallelism is introduced resulting in time efficient division and sign detection.

Kinematics and dynamics in robotics: A tutorial based upon classical concepts of vectorial mechanics

Methods are presented for kinematical and dynamical modeling and analysis of robots that are based upon vectorial mechanics. Basic principles for robotics are presented using classical definitions and concepts. An example of the application of the Newton-Euler equations is included.

Brief paper: Optimal control of bilinear systems: Time-varying effects of cancer drugs

A bilinear model is introduced to study the effects of anti-tumor drugs on the kinetics of the cell cycle. Optimal control theory is applied in the estimation of these time-varying effects based on a least squares fit of laboratory data. This methodology enables the authors to quantify the effects of a drug on each phase of the cell cycle.

A stochastic compartmental model with continuous infusion

This paper deals with stochasticm-compartmental systems with continuous time-dependent infusions into all compartments and reversible time-independent flows between any two compartments. A methodology for the first two moments of the distribution of the number of units in the different compartments at any point in time is outlined without resorting to the usual techniques of generating functions and inverse Laplace transforms. A possible application to a systems analysis of the kidney transplant system is discussed.

Stochastic compartmental modeling and parameter estimation with application to cancer treatment follow-up studies†

In this paper we use marginal probabilities to derive expressions for the means, variances and covariances of m-compartment systems. We also present an efficient algorithm for the estimation of the parameters of the system using time series data when measurements are available from k of the m compartments. An application of the analysis and parameter estimation procedure for a model representing the results of a cancer treatment follow-up study is given.

A microcomputer-based control system for the total artificial heart

Abstract A microcomputer-based control system for a pneumatically driven artificial heart is developed in which the control philosophy consists of P-wave synchronization and stabilization of atrial pressures at desired levels. A self-tuning algorithm based on pole-placement for a two-input, two-output PI-controller is proposed. An electrical analogue model of the circulatory system is used to illustrate the coupling effect of the systemic and pulmonary circulations by decoupling the whole system into subsystems. The performance of the control system has been demonstrated by in vitro experiments on a mock circulatory system. It is shown that stabilization of atrial pressures gives a good solution to the balancing problem of blood volume output, and the adjustment of the desired levels of atrial pressures corresponding to changes of heart rate produces effective physiological control.