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Biomedical subjects

R E Gander

Publications and source records attributed to R E Gander.

12 recordsLinked to original sources
PubMed1997

Model Predictive Impedance Control: A Model for Joint Movement.

Impedance control has been suggested as the strategy employed by the central nervous system to control human postures and movements. A realization of this strategy is presented that uses a model predictive control algorithm as a higher motor controller. External disturbances are explicitly included in the model. The combination of 3 key factors-joint impedance control, model predictive controller, and external disturbance input-forms the basis for the generality of this model. The model was applied to 3 different types of joint movements: a tracking movement with an unpredicted disturbance, a rhythmic movement, and an unstable biped model of human walking. Computer simulation results showed excellent performance of the model in all 3 cases for optimal values of active joint impedances and an exact match between the musculoskeletal system and the model internal to the model predictive controller. The controller was also able to maintain acceptable performance in the presence of a 25% mismatch between the musculoskeletal system and its internal model.

equilibrium-point hypothesis↗
PubMed1996

Determination of nerve conduction velocity distribution from sampled compound action potential signals.

The sampled compound action potential (CAP) data sequence was expressed as the circular convolution of the delay sequence and the sampled single fiber action potential (SFAP) data sequence. An algorithm, based on Hirose's method [1], was then developed to separate the delay sequence from the sampled CAP data sequence, and the nerve conduction velocity distribution (NCVD) was consequently calculated from the delay sequence. The NCVD was found to be the product of the amplitude of the SFAP and the number of fibers. Simulations show that the estimated results were in good agreement with the calculated results. Experiments were performed on ten sciatic nerves from five bullfrogs (Rana pipens) using two independent variables: interelectrode distance and stimulus current strength. The results estimated from CAP's recorded under each condition reflect the corresponding feature of NCVD of the condition. The advantage of the technique is to provide detailed information about both slow and fast conducting fibers. This technique also offers the possibility to directly calculate the nerve fiber diameter distribution from the sampled CAP data sequences.

Action Potentials↗
PubMed1992

A movement pattern generator model using artificial neural networks.

Artificial neural networks (ANN's) allow a new approach to biological modeling. The main applications of ANN's have been geared towards the modeling of the association and learning mechanisms of the brain; only a few researchers have explored them for motor control. The fact that ANN's are based on biological systems indicates their potential application for a biological act such as locomotion. Towards this goal, we have developed a "movement pattern generator," using an ANN for generating periodic movement trajectories. This model is based on the concept of "central pattern generators." Jordan's sequential network, which is capable of learning sequences of patterns, was modified and used to generate several bipedal trajectories (or gaits), coded in task space, at different frequencies. The network model successfully learned all of the trajectories presented to it. The model has many attractive properties such as limit cycle behavior, generalization of trajectories and frequencies, phase maintenance, and fault tolerance. The movement pattern generator model is potentially applicable for improved understanding of animal locomotion and for use in legged robots and rehabilitation medicine.

Animals↗
PubMed1991

Real-time digital median frequency estimator for surface myoelectric signals.

A prototype instrument is described that uses a digital signal processor to estimate the median frequency of the myoelectric signal in real time. A set of tenth-order digital low-pass filters is used to track the median frequency. An estimate of frequency is obtained once every 256 ms with a resolution of 1 Hz.

Algorithms↗
PubMed1989

Changes in the myoelectric signal (MES) power spectra during dynamic contractions.

Power spectra of surface myoelectric signals (MES) have been estimated during dynamic contractions of the biceps brachii. The effect of applied torque, velocity of contraction and muscle length have been studied with respect to median frequency and total spectral power. The results of the investigation carried out thus far can be summarised as follows: (1) The median frequency is observed to vary with the applied torque and the muscle length but not with the velocity of contraction. (2) The expected dependence of the MES power with the applied torque, velocity and muscle length was confirmed. These results suggest that the power spectrum could be used to reveal changes in the electrophysiological characteristics of a muscle during dynamic contractions as is the case with static contractions.

Adult↗
PubMed1976

Comparison of peripheral and portal routes of insulin infusion by a computer-controlled insulin infusion system (artificial endocrine pancreas).

This study was undertaken to determine the different consequences of portal and peripheral routes of insulin administration by the artificial endocrine pancreas. Intraportal glucose was infused (10 mg./min./kg. for 60 minutes) in anesthetized normal and pancreatectomized dogs while blood glucose concentrations were monitored continuously. During computer-controlled insulin administration normal glucose tolerance was restored by both portal and peripheral routes of insulin delivery. There were also no significant differences in (1) glycemic patterns, (2) insulin infusion patterns, (3) peripheral IRI levels, and (4) total insulin requirements between the two routes. It is apparent that the peripheral route, which is more readily accessible than the portal route, may be an appropriate infusion site for an implantable or portable prosthesis for controlling blood glucose concentration.

Animals↗
PubMedDate not supplied

Biomedical engineering education in Canada, 1996.

This paper updates the information contained in a previously published paper, ¿Bioengineering Education in Canada, 1988,¿ which appeared in the Journal of Clinical Engineering (Volume 13, No. 5). It describes the current biomedical engineering and biomedical engineering technology programs available in Canada, but does not attempt to evaluate them. There are no undergraduate degree programs specifically in biomedical engineering, although three universities have created options in biomedical engineering in undergraduate programs. Also, the clinical engineering program at the University of British Columbia has been discontinued.

Biomedical Engineering↗
PubMedDate not supplied

An all-plastic double-lumen catheter for continuous blood sampling.

The all-plastic double-lumen catheter described in this paper represents a significant improvement over previously reported catheters. It is used routinely for continuous blood withdrawal in two clinical investigation units and one experimental laboratory in Toronto. No experiments have been terminated due to catheter failure or clot formation and no maximum time limit of its use has been established. In clinical use with adult patients (4), the outer cannula has been kept open overnight with a slow saline drip after 18 hours of use. The same cannula has then been reused the next day for another 16 hours with a new adapter precut to size. Its design enzures that: (1) heparin is mixed with the blood at the site of blood sampling. (2) Blood is never brought into contact with glass or metal. (3) The blood channel is a uniform polyethylene tube with no discontinuities and no junctions, except where it is introduced into the peristaltic pump tube. The overall manufacturing process is simple, and percutaneous insertion is straightforward. Through its use, clotting in the blood withdrawal line and thrombus formations in the blood analyzer are no longer problems to limit the use of techniques requiring continuous blood withdrawal.

Blood Specimen Collection↗