H. Chizeck | University of Washington (original) (raw)

Papers by H. Chizeck

Research paper thumbnail of An optimal control analysis of motor strategies in a brain-computer interface task

2013 6th International IEEE/EMBS Conference on Neural Engineering (NER), 2013

Optimality principles have provided concise and powerful descriptions of a wide variety of motor ... more Optimality principles have provided concise and powerful descriptions of a wide variety of motor tasks, including arm-reaching, saccadic movements, and human walking. Here, we consider whether optimal control methods can be used to understand the control strategy employed in a visual braincomputer interface (BCI) task controlled by isolated cortical neurons (units). Using an inverse optimal control method we obtain, from many candidate cost functions, a weighted objective function which is consistent with average trajectories of a movement task under both brain and native limb control. The objective function has physiological and theoretical relevance, and we consider its implications for the movement strategies in each task type. Furthermore, the objective function is suggestive of a closed-loop optimal control model. The results of this paper show that optimal control theory can provide significant utility towards understanding motor strategies and system properties in BCIs.

Research paper thumbnail of Estimating mechanical parameters of leg segments in individuals with and without physical disabilities

IEEE Transactions on Neural Systems and Rehabilitation Engineering, 1996

Methods are described for estimating the inertia, viscosity, and stiffness of the lower leg aroun... more Methods are described for estimating the inertia, viscosity, and stiffness of the lower leg around the knee and of the whole leg around the hip that are applicable even to persons with considerable spasticity. These involve: (1) a “pull” test in which the limb is slowly moved throughout its range of motion while measuring angles (with an electrogoniometer) and torques

Research paper thumbnail of Self-tuning controller for drug delivery systems

International Journal of Control, 1988

Page 1. Self-tuning controller for drug delivery systems GI VOSStS, H. J. CHZECK and PG KATONAt A... more Page 1. Self-tuning controller for drug delivery systems GI VOSStS, H. J. CHZECK and PG KATONAt A new adaptive control algorithm, the ...

Research paper thumbnail of Relationship between intracranial and sagittal sinus pressure in normal and hydrocephalic dogs

Pediatric Neuroscience, 1988

The relationship between intracranial and sagittal sinus pressure in normal and kaolin-induced hy... more The relationship between intracranial and sagittal sinus pressure in normal and kaolin-induced hydrocephalic greyhounds was examined. In normal dogs there was an average 14 mm Hg pressure difference between the ventricles and the sagittal sinus. Elevations of intraventricular pressure were accompanied by small but consistent elevations in sagittal sinus pressure. In hydrocephalic dogs the average pressure differential was only 2 mm Hg. Also elevations of intraventricular pressure were accompanied by greater elevations in sagittal sinus pressures than those seen in normal dogs. The volume-buffering capacity of the sagittal sinus was decreased, and sinography revealed filling of unusual venous collaterals in hydrocephalic dogs--both suggesting an increased resistance to outflow in the sagittal sinus.

Research paper thumbnail of Linear quadratic control of a loaded agonist-antagonist muscle pair

IEEE Transactions on Biomedical Engineering, 1987

A discrete-time control law which gives the optimal applied force for a given position trajectory... more A discrete-time control law which gives the optimal applied force for a given position trajectory of a linear second-order external load is computed using linear quadratic regulator (LQR) theory. This control law is used with an existing first-order fixed interpulse interval (IPI) muscle force controller to regulate position in a simulated electrically stimulated loaded agonist-antagonist muscle system. Both force and position feedback are required to implement the control strategy. A nonlinear second-order model of a predominantly slow twitch muscle is used in the simulation. The results suggest that good position control of a loaded antagonist-agonist muscle system is possible if a linear model of the external load is appropriate.

Research paper thumbnail of Discrete-time Markovian-jump linear quadratic optimal-control

This. paper is concerned with the optimal control of discrete-time linear systems that possess ra... more This. paper is concerned with the optimal control of discrete-time linear systems that possess randomly jumping parameters described by finite state Markov processes. For problems having quadratic costs and perfect observations, the optimal control laws and expected costs-to-go can be precomputed from a set of coupled Riccati-like matrix difference equations. Necessary and sufficient conditions are derived for the existence of optimal constant control laws which stabilize the controlled system as the time horizon becomes infinite, with finite optimal expected cost.

Research paper thumbnail of Helping paraplegics walk: looking beyond the media blitz

Research paper thumbnail of Instrumented parallel bars for three-dimensional force measurement

Journal of rehabilitation research and development, 1992

This paper describes the modification and instrumentation of standard parallel bars to allow for ... more This paper describes the modification and instrumentation of standard parallel bars to allow for the measurement of applied forces on both horizontal bars in three dimensions. This measurement system has been used in the development and evaluation of functional electrical stimulation (FES) devices for standing and gait restoration in paralyzed patients. Real-time measurement of forces applied by the upper body of the patient to the parallel bars is of use in the evaluation of FES stimulation patterns (or automatic controllers of stimulation). Such measurements are useful in the redesign of stimulation patterns and/or stimulation controllers.

Research paper thumbnail of Adaptive multivariable drug delivery: control of arterial pressure and cardiac output in anesthetized dogs

IEEE Transactions on Biomedical Engineering, 1987

Research paper thumbnail of Adaptive control of electrically stimulated muscle

IEEE Transactions on Biomedical Engineering, 1987

ABSTRACT

Research paper thumbnail of Etiology of ventriculomegaly in choroid plexus papilloma

Pediatric Neuroscience

In order to test the hypothesis that overproduction of cerebrospinal fluid can cause the hydrocep... more In order to test the hypothesis that overproduction of cerebrospinal fluid can cause the hydrocephalus seen in choroid plexus papillomas, adult mongrel dogs with and without hydrocephalus were subjected to high pressure intraventricular infusions of artificial cerebrospinal fluid (CSF). Pre- and postinfusion volumes were calculated, using a new method for on-line measurement of ventricular volume involving linear measurements from Conray ventriculograms. Ventricular volumes increased an average of 8% in 36 h. The dogs previously made hydrocephalic by the intracisternal injection of kaolin had a significant volume increase (34% in 36 h). Overproduction of CSF alone can produce hydrocephalus, but the presence of hydrocephalus in choroid plexus papillomas is more likely to be a result of the complex interaction of CSF overproduction and partial restriction of CSF flow.

Research paper thumbnail of Abstract KALMAN FILTERING WITH STATISTICAL STATE CONSTRAINTS

For linear dynamic systems with white process and measurement noise, the Kalman ¯lter is known to... more For linear dynamic systems with white process and measurement noise, the Kalman ¯lter is known to be the minimum variance linear state estimator. In the case that the random quantities are Gaussian, then the Kalman ¯lter is the minimim variance state estimator. However, in the appli-cation of Kalman ¯lters known signal information is often either ignored or dealt with heuristically. For instance, state variable constraints (which may be based on physical considerations) are often neglected because they do not ¯t easily into the structure of the optimal ¯lter. Previous work by the authors demonstrated an analytic method of incorporating deterministic state equality constraints in the Kalman ¯lter. This paper extends that work to develop the properties of Kalman ¯lters in the presence of statistical state constraints. That is, given a linear system such that the expected values of the state variables satisfy some linear equality, we can constrain the Kalman ¯lter estimates to sat-1 is...

Research paper thumbnail of Automatic regulation for administration of therapeutic agents

IEEE transactions on bio-medical engineering, 1987

Research paper thumbnail of Fully implanted adaptive deep brain stimulation in freely moving essential tremor patients

Objective: Deep brain stimulation (DBS) is a safe and established treatment for essential tremor ... more Objective: Deep brain stimulation (DBS) is a safe and established treatment for essential tremor (ET) and several other movement disorders. One approach to improving DBS therapy is adaptive DBS (aDBS), in which stimulation parameters are modulated in real time based on biofeedback from either external or implanted sensors. Previously tested systems have fallen short of translational applicability due to the requirement for patients to continuously wear the necessary sensors or processing devices, as well as privacy and security concerns. Approach: We designed and implemented a translation-ready training data collection system for fully implanted aDBS. Two patients chronically implanted with electrocorticography strips over the hand portion of M1 and DBS probes in the ipsilateral ventral intermediate nucleus of the thalamus for treatment of ET were recruited for this study. Training was conducted using a translation-ready distributed training procedure, allowing a substantially highe...

Research paper thumbnail of A software structure for implementing multi-state feedback controllers in FNS systems

ABSTRACT A software structure is described that has been developed for the implementation of feed... more ABSTRACT A software structure is described that has been developed for the implementation of feedback controllers for standing, gait, and stair climbing using functional neuromuscular stimulation (FNS) in paralyzed individuals. The control structure has two levels. The upper level controller monitors the progression of the controlled system through a finite set of allowable states. The occurrence of particular events marks the transition of the system from one state to another. In each state a specified set of lower level controllers is used to achieve certain tasks.< >

Research paper thumbnail of Symbolic solution of non-Markovian jump linear quadratic (JLQ) systems

The authors consider a class of scalar JLQ problems wherein the form transition probabilities are... more The authors consider a class of scalar JLQ problems wherein the form transition probabilities are state-dependent and are piecewise constant in the state. The optimal solution is known to exhibit interesting algorithmic formulations of the control involving logical expressions and recursions. These are amenable to symbolic computation rather than to numerical processing. Symbolic computational methods can be used to design the optimal control law explicitly. A specific example is given, and extensions to more general problems are discussed

Research paper thumbnail of Nonlinear Recursive Identification Of Recruitment Curve And Dynamics Of Electrically Stimulated Muscle

Research paper thumbnail of Closed-Loop Controller-Design of Neuroprosthetics for Functional Walking in Paralyzed Patients

Research paper thumbnail of Algebraic Systems Theory and DNA Structure

Research paper thumbnail of A unified approach to the analysis and design of predictive control

Research paper thumbnail of An optimal control analysis of motor strategies in a brain-computer interface task

2013 6th International IEEE/EMBS Conference on Neural Engineering (NER), 2013

Optimality principles have provided concise and powerful descriptions of a wide variety of motor ... more Optimality principles have provided concise and powerful descriptions of a wide variety of motor tasks, including arm-reaching, saccadic movements, and human walking. Here, we consider whether optimal control methods can be used to understand the control strategy employed in a visual braincomputer interface (BCI) task controlled by isolated cortical neurons (units). Using an inverse optimal control method we obtain, from many candidate cost functions, a weighted objective function which is consistent with average trajectories of a movement task under both brain and native limb control. The objective function has physiological and theoretical relevance, and we consider its implications for the movement strategies in each task type. Furthermore, the objective function is suggestive of a closed-loop optimal control model. The results of this paper show that optimal control theory can provide significant utility towards understanding motor strategies and system properties in BCIs.

Research paper thumbnail of Estimating mechanical parameters of leg segments in individuals with and without physical disabilities

IEEE Transactions on Neural Systems and Rehabilitation Engineering, 1996

Methods are described for estimating the inertia, viscosity, and stiffness of the lower leg aroun... more Methods are described for estimating the inertia, viscosity, and stiffness of the lower leg around the knee and of the whole leg around the hip that are applicable even to persons with considerable spasticity. These involve: (1) a “pull” test in which the limb is slowly moved throughout its range of motion while measuring angles (with an electrogoniometer) and torques

Research paper thumbnail of Self-tuning controller for drug delivery systems

International Journal of Control, 1988

Page 1. Self-tuning controller for drug delivery systems GI VOSStS, H. J. CHZECK and PG KATONAt A... more Page 1. Self-tuning controller for drug delivery systems GI VOSStS, H. J. CHZECK and PG KATONAt A new adaptive control algorithm, the ...

Research paper thumbnail of Relationship between intracranial and sagittal sinus pressure in normal and hydrocephalic dogs

Pediatric Neuroscience, 1988

The relationship between intracranial and sagittal sinus pressure in normal and kaolin-induced hy... more The relationship between intracranial and sagittal sinus pressure in normal and kaolin-induced hydrocephalic greyhounds was examined. In normal dogs there was an average 14 mm Hg pressure difference between the ventricles and the sagittal sinus. Elevations of intraventricular pressure were accompanied by small but consistent elevations in sagittal sinus pressure. In hydrocephalic dogs the average pressure differential was only 2 mm Hg. Also elevations of intraventricular pressure were accompanied by greater elevations in sagittal sinus pressures than those seen in normal dogs. The volume-buffering capacity of the sagittal sinus was decreased, and sinography revealed filling of unusual venous collaterals in hydrocephalic dogs--both suggesting an increased resistance to outflow in the sagittal sinus.

Research paper thumbnail of Linear quadratic control of a loaded agonist-antagonist muscle pair

IEEE Transactions on Biomedical Engineering, 1987

A discrete-time control law which gives the optimal applied force for a given position trajectory... more A discrete-time control law which gives the optimal applied force for a given position trajectory of a linear second-order external load is computed using linear quadratic regulator (LQR) theory. This control law is used with an existing first-order fixed interpulse interval (IPI) muscle force controller to regulate position in a simulated electrically stimulated loaded agonist-antagonist muscle system. Both force and position feedback are required to implement the control strategy. A nonlinear second-order model of a predominantly slow twitch muscle is used in the simulation. The results suggest that good position control of a loaded antagonist-agonist muscle system is possible if a linear model of the external load is appropriate.

Research paper thumbnail of Discrete-time Markovian-jump linear quadratic optimal-control

This. paper is concerned with the optimal control of discrete-time linear systems that possess ra... more This. paper is concerned with the optimal control of discrete-time linear systems that possess randomly jumping parameters described by finite state Markov processes. For problems having quadratic costs and perfect observations, the optimal control laws and expected costs-to-go can be precomputed from a set of coupled Riccati-like matrix difference equations. Necessary and sufficient conditions are derived for the existence of optimal constant control laws which stabilize the controlled system as the time horizon becomes infinite, with finite optimal expected cost.

Research paper thumbnail of Helping paraplegics walk: looking beyond the media blitz

Research paper thumbnail of Instrumented parallel bars for three-dimensional force measurement

Journal of rehabilitation research and development, 1992

This paper describes the modification and instrumentation of standard parallel bars to allow for ... more This paper describes the modification and instrumentation of standard parallel bars to allow for the measurement of applied forces on both horizontal bars in three dimensions. This measurement system has been used in the development and evaluation of functional electrical stimulation (FES) devices for standing and gait restoration in paralyzed patients. Real-time measurement of forces applied by the upper body of the patient to the parallel bars is of use in the evaluation of FES stimulation patterns (or automatic controllers of stimulation). Such measurements are useful in the redesign of stimulation patterns and/or stimulation controllers.

Research paper thumbnail of Adaptive multivariable drug delivery: control of arterial pressure and cardiac output in anesthetized dogs

IEEE Transactions on Biomedical Engineering, 1987

Research paper thumbnail of Adaptive control of electrically stimulated muscle

IEEE Transactions on Biomedical Engineering, 1987

ABSTRACT

Research paper thumbnail of Etiology of ventriculomegaly in choroid plexus papilloma

Pediatric Neuroscience

In order to test the hypothesis that overproduction of cerebrospinal fluid can cause the hydrocep... more In order to test the hypothesis that overproduction of cerebrospinal fluid can cause the hydrocephalus seen in choroid plexus papillomas, adult mongrel dogs with and without hydrocephalus were subjected to high pressure intraventricular infusions of artificial cerebrospinal fluid (CSF). Pre- and postinfusion volumes were calculated, using a new method for on-line measurement of ventricular volume involving linear measurements from Conray ventriculograms. Ventricular volumes increased an average of 8% in 36 h. The dogs previously made hydrocephalic by the intracisternal injection of kaolin had a significant volume increase (34% in 36 h). Overproduction of CSF alone can produce hydrocephalus, but the presence of hydrocephalus in choroid plexus papillomas is more likely to be a result of the complex interaction of CSF overproduction and partial restriction of CSF flow.

Research paper thumbnail of Abstract KALMAN FILTERING WITH STATISTICAL STATE CONSTRAINTS

For linear dynamic systems with white process and measurement noise, the Kalman ¯lter is known to... more For linear dynamic systems with white process and measurement noise, the Kalman ¯lter is known to be the minimum variance linear state estimator. In the case that the random quantities are Gaussian, then the Kalman ¯lter is the minimim variance state estimator. However, in the appli-cation of Kalman ¯lters known signal information is often either ignored or dealt with heuristically. For instance, state variable constraints (which may be based on physical considerations) are often neglected because they do not ¯t easily into the structure of the optimal ¯lter. Previous work by the authors demonstrated an analytic method of incorporating deterministic state equality constraints in the Kalman ¯lter. This paper extends that work to develop the properties of Kalman ¯lters in the presence of statistical state constraints. That is, given a linear system such that the expected values of the state variables satisfy some linear equality, we can constrain the Kalman ¯lter estimates to sat-1 is...

Research paper thumbnail of Automatic regulation for administration of therapeutic agents

IEEE transactions on bio-medical engineering, 1987

Research paper thumbnail of Fully implanted adaptive deep brain stimulation in freely moving essential tremor patients

Objective: Deep brain stimulation (DBS) is a safe and established treatment for essential tremor ... more Objective: Deep brain stimulation (DBS) is a safe and established treatment for essential tremor (ET) and several other movement disorders. One approach to improving DBS therapy is adaptive DBS (aDBS), in which stimulation parameters are modulated in real time based on biofeedback from either external or implanted sensors. Previously tested systems have fallen short of translational applicability due to the requirement for patients to continuously wear the necessary sensors or processing devices, as well as privacy and security concerns. Approach: We designed and implemented a translation-ready training data collection system for fully implanted aDBS. Two patients chronically implanted with electrocorticography strips over the hand portion of M1 and DBS probes in the ipsilateral ventral intermediate nucleus of the thalamus for treatment of ET were recruited for this study. Training was conducted using a translation-ready distributed training procedure, allowing a substantially highe...

Research paper thumbnail of A software structure for implementing multi-state feedback controllers in FNS systems

ABSTRACT A software structure is described that has been developed for the implementation of feed... more ABSTRACT A software structure is described that has been developed for the implementation of feedback controllers for standing, gait, and stair climbing using functional neuromuscular stimulation (FNS) in paralyzed individuals. The control structure has two levels. The upper level controller monitors the progression of the controlled system through a finite set of allowable states. The occurrence of particular events marks the transition of the system from one state to another. In each state a specified set of lower level controllers is used to achieve certain tasks.< >

Research paper thumbnail of Symbolic solution of non-Markovian jump linear quadratic (JLQ) systems

The authors consider a class of scalar JLQ problems wherein the form transition probabilities are... more The authors consider a class of scalar JLQ problems wherein the form transition probabilities are state-dependent and are piecewise constant in the state. The optimal solution is known to exhibit interesting algorithmic formulations of the control involving logical expressions and recursions. These are amenable to symbolic computation rather than to numerical processing. Symbolic computational methods can be used to design the optimal control law explicitly. A specific example is given, and extensions to more general problems are discussed

Research paper thumbnail of Nonlinear Recursive Identification Of Recruitment Curve And Dynamics Of Electrically Stimulated Muscle

Research paper thumbnail of Closed-Loop Controller-Design of Neuroprosthetics for Functional Walking in Paralyzed Patients

Research paper thumbnail of Algebraic Systems Theory and DNA Structure

Research paper thumbnail of A unified approach to the analysis and design of predictive control