bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Nonstationary Response of Vehicles With Multiple Wheels
Authors: Harrison R. F. , Hammond J. K.
Published: July 2009

Vehicles moving on rough surfaces are subject to inputs which are often conveniently regarded as random processes. In general, the excitation process is “perceived” by the vehicle as a nonstationary random process either due to inhomogeneity in the ground profile or variations in the vehicle’s velocity, or both, Hitherto this second case has not been tractable analytically due to the time variable delay between inputs. In this paper this difficulty is overcome and expressions are derived for the propagation of the mean vector and zero-lag autocovariance matrix. An example of a vehicle modelled by a bicycle configuration is discussed.
Decentralized Fixed-Interval Smoothing Algorithms
Authors: Watanabe Keigo
Published: July 2009

The Weineret-Desai smoother formula is applied to derive new decentralized fixed-interval smoothing algorithms for a decentralized estimation structure consisting of a central processor and of M local processors. Such algorithms are based on decentralizing the estimates of global backward information filter and obtained from the use of the superposition principle in scattering framework. The smoothing update problem is also investigated to illustrate the application of the proposed algorithms. The emphasis is on computational efficiency, independence of local a priori statistics, and flexibility of implementation.
End Effector Path Generation
Authors: Goldenberg A. A. , Lawrence D. L.
Published: July 2009

The path followed by a robotic manipulator is often defined by a sequence of Cartesian knots, i.e., position and orientation (location) of the end effector and the corresponding linear and angular velocity (speed) at each knot. The path location and speed in the interval between knots are not specified. Typically the control of robots is performed in terms of joint coordinates. Often, the joint coordinates corresponding to the path knots are splined together using lower degree polynomials. The actual path and speed followed by the end effector can be obtained by performing forward (direct) kinematics—a pointwise transformation. To obtain a good approximation of the actual path, many points must be used. In this paper an efficient first order approximation of the actual path using third order (cubic) interpolating polynomials is presented. The technique eliminates the need for repeatedly using the forward kinematics. The technique is illustrated by means of numerical examples.
Generalized Optimal Feedback Controllers for Discrete-Time Linear Systems
Authors: Cheok K. C. , Loh N. K. , Zohdy M. A.
Published: July 2009

This paper presents a unified treatment to the problem of optimal feedback control of discrete-time linear shift-invariant systems using state feedback, output feedback, dynamical output feedback, and observer-controller feedback. A class of generalized optimal feedback controllers is proposed as a basis for obtaining existing results as well as for deriving new results such as the interesting min-max feedback controllers. The essence of the generalized results lies in the minimization of a class of generalized performance measures subject to a flexible controller configuration. The stability aspect of the generalized optimal feedback controlled system is addressed.
Multiple Solutions for a Class of Continuous Nonlinear Systems
Authors: Fish A. J.
Published: July 2009

A nonlinear state space representation of a nonlinear system implies that the system has a unique solution for a given set of initial conditions and system controls. But not all nonlinear systems have unique solutions for a given set of initial conditions and system controls. This paper presents an algebraic theory for solving continuous nonlinear systems equations that have multiple solutions.
Model Reference Adaptive Control of Feed Force in Turning
Authors: Daneshmend L. K. , Pak H. A.
Published: July 2009

This paper applies the discrete-time single-input/single-output Model Reference Adaptive Control (MRAC) design technique of Landau and Lozano to the problem of regulating feed force on a lathe under varying cutting conditions. A first-order model is used to represent the relationship between feed force and the control input (feedrate). The MRAC scheme is implemented on a multi-microprocessor based computer-numerical-control system. Results of applying various algorithms derived from the MRAC design technique are presented.
A Redundancy Management Procedure for Fault Detection and Isolation
Authors: Ray Asok , Desai Mukund
Published: July 2009

This paper presents the theoretical basis of a novel redundancy management procedure developed for fault detection and isolation (FDI) in strategic processes such as spacecraft, aircraft, and nuclear plants where multiply-redundant measurements are available for individual variables. The set of redundant measurements may comprise both direct sensor outputs and analytically derived measurements. The redundancy management procedure presented in this paper is essentially independent of the fault detection strategy and measurement noise statistics, and builds upon the concept of partitioning the set of measurements into “consistent” and “inconsistent” subsets for purposes of estimation and fault isolation, respectively. The proposed procedure is suitable for real-time applications using commercially available microcomputers and its efficacy has been verified on-line in operating nuclear reactors.
Dynamic Matching of Acceleration Transducers
Authors: Peleg Kalman , Shpigler Shabtai
Published: July 2009

Small mismatches between similarly manufactured accelerometers stem from slight differences between their flexural elements, seismic masses and their mountings, as well as variations in damping ratios. This is not detrimental for measuring absolute accelerations, but when it is desired to measure differential accelerations, very large errors may result. This is probably the main reason why transducers for measuring differential acceleration are not generally commercially available. Measuring the differential acceleration between two accelerometers mounted in different locations of an item provides a convenient means of measuring the relative velocity and displacement by single and double integration of the differential acceleration signal. To do this with good accuracy both accelerometers must have identical static and dynamic response characteristics. A method of matching the D.C. and dynamic response characteristics of any number of similarly manufactured piezoresistive acceleration transducers is described. This method is based on electronic compensation networks whereby the combined transfer functions of the transducers and their compensation networks are matched, enabling differential acceleration measurements with good accuracy. In addition to matching the effective transfer functions of the transducers, this method also significantly extends the operating frequency range in both absolute and differential measurements. The line taken is based on a general mathematical model, which was developed for quantifying error sources in differential measurements at large.
Joint Estimation and Control of Jump Linear Systems With Multiplicative Noises
Authors: Mariton M.
Published: July 2009

Jump Linear Quadratic Gaussian systems are considered in the presence of state-and control-dependent noises. Assuming that the jumps of the model parameters are perfectly observed, it is possible to formulate and solve an optimal input synthesis problem. It is found that the optimal solution does not present the certainty equivalence property, so that the estimation and control synthesis must be treated simultaneously. Optimal equations for the filter and regulator gains are obtained in terms of a set of coupled nonlinear matrix differential equations.
A Method for Inverse Robot Calibration
Authors: Shamma J. S. , Whitney D. E.
Published: July 2009

A method is described for the inverse calibration of a manipulator or robot. Inverse calibration is defined to be finding the joint angles necessary to drive a robot to a desired endpoint location. The joint angles recommended by the robot controller’s internal model will not, in general, drive the robot to the desired location because of inaccuracies in this model. Inverse calibration seeks to reduce the error. Unlike previous work in calibration, the method reported here does not require modeling any specific phenomena that may cause the error; hence it is not limited in accuracy by inability to identify all the error sources. The method consists of finding approximation functions by which corrections are made to the encoder readings recommended by the robot’s internal model. These functions are found by measuring the error at discrete locations throughout a region of the robot’s workspace and then least-squares fitting third order trivariate polynomials to the error samples. A forward calibration (one which reports actual tool location from given encoder readings) based on the above method is also described. The inverse calibration is tested on a six DOF PUMA simulation. Results show that the endpoint location error can be reduced from an average of about 1.2 mm down to an average of about 0.12 mm.
Zero Phase Error Tracking Algorithm for Digital Control
Authors: Tomizuka Masayoshi
Published: July 2009

A digital feedforward control algorithm for tracking desired time varying signals is presented. The feedforward controller cancels all the closed-loop poles and cancellable closed-loop zeros. For uncancellable zeros, which include zeros outside the unit circle, the feedforward controller cancels the phase shift induced by them. The phase cancellation assures that the frequency response between the desired output and actual output exhibits zero phase shift for all the frequencies. The algorithm is particularly suited to the general motion control problems including robotic arms and positioning tables. A typical motion control problem is used to show the effectiveness of the proposed feedforward controller.
Application of Generalized Orthogonal Polynomials to Parameter Estimation of Time-Invariant and Bilinear Systems
Authors: Wang Maw-Ling , Yang Shwu-Yien , Chang Rong-Yeu
Published: July 2009

Generalized orthogonal polynomials (GOP) which can represent all types of orthogonal polynomials and nonorthogonal Taylor series are first introduced to estimate the parameters of a dynamic state equation. The integration operation matrix (IOP) and the differentiation operation matrix (DOP) of the GOP are derived. The key idea of deriving IOP and DOP of these polynomials is that any orthogonal polynomial can be expressed by a power series and vice versa. By employing the IOP approach to the identification of time invariant systems, algorithms for computation which are effective, simple and straightforward compared to other orthogonal polynomial approximations can be obtained. The main advantage of using the differentiation operation matrix is that the parameter estimation can be carried out starting at an arbitrary time of interest. In addition, the computational algorithm is even simpler than that of the integral operation matrix. Illustrative examples for using IOP and DOP approaches are given. Very satisfactory results are obtained.
Optimal Input Design for the Dynamic Testing of Mechanical Systems
Authors: deSilva C. W.
Published: July 2009

A technique to synthesize optimal excitations for dynamic testing is presented. A quadratic function of the frequency response at modeled degrees of freedom of the test object is employed as the test severity measure, subject to an energy constraint on forcing excitation. The optimal test excitation is generated by successively solving a matrix-eigenvalue problem, off line, at all discrete spectral points of interest and then inverse Fourier transforming the optimal spectrum. The technique provides the worst excitation vector, which is the optimal test excitation, as well as the best excitation vector, which corresponds to the best operating environment. Two numerical examples are provided to illustrate the technique. In both cases the worst severity is found to be one or more orders of magnitude higher than the best severity, for the same level of input excitation energy. These results support the practical experience that serious undertesting and severe overtesting can result for comparable levels of forcing input, unless the spectral content of test excitation is carefully chosen by taking the dynamic characteristics of the test object into consideration. The concepts presented in this paper can lead to improved design approaches for disturbance isolators.
A Theoretically Motivated Reduced Order Model for the Control of Dynamic Biped Locomotion
Authors: Furusho J. , Masubuchi M.
Published: July 2009

A new reduced order model of a biped locomotion system and its theoretical basis are presented based upon the concept of local feedback. It has been reported from physiological studies that local feedback at each articular joint exists in human motor control, and the authors have already studied from the viewpoint of control engineering that local feedback makes the total system robust. A theorem is presented by which two dominant modes are obtained by the application of local feedback at each articular joint in the biped locomotion machine and it is shown that these two modes correspond to inverted-pendulum modes. The reduced order model derived by using these two modes contains the effect of the motion of body and swing leg which is indispensable for the control of biped locomotion. It is shown that this model can approximate very well the original higher model in almost all walking phases containing start-up and stopping motions.
A Relative Stability Study on the Dynamics of the Turning Mechanism
Authors: Olgac Nejat , Zhao Guoquan
Published: July 2009

A typical turning process is taken as a representative dynamic event for metal machining operations. The intrinsically oscillatory nature of this process is discussed, considering a number of parametric identifiers in the model. This oscillatory behavior is stable in the general sense of “stability.” However, under varying cutting conditions and for different system parameters, the “degree of stability” may be of importance. This issue is addressed to assist the off-line tool path determinations (i.e., parts programming) in some optimal fashion. Frequency response techniques are used. Following a definition for the “level of stability” comparative listings for various turning cases are given. Zone of preference for the operation parameters are depicted for future reference.
Pole Allocation Using Matrix Perturbations
Authors: Baruh H.
Published: July 2009

An approach is presented for pole placement in controllers and observers. The first-order perturbation of the system eigensolution is used to analyze and design the feedback gains. The accuracy of the control (or observer) design depends on how small a perturbation the control gains are on the uncontrolled system, and it is assessed qualitatively and quantitatively.
On Sliding Observers for Nonlinear Systems
Authors: Slotine J.-J. E. , Hedrick J. K. , Misawa E. A.
Published: July 2009

Sliding controllers have recently been shown to feature excellent robustness and performance properties for specific classes of nonlinear tracking problems. This paper examines the potential use of sliding surfaces for observer design. A particular observer structure including switching terms is introduced for both systems in companion form and systems in general form. The analysis of systems in companion form shows that sliding observers have promising properties in the presence of modeling errors and sensor noise, as highlighted through two numerical examples. Extensions to general nonlinear observable systems are also discussed.
Modeling and Control of Elastic Joint Robots
Authors: Spong M. W.
Published: July 2009

In this paper we study the modeling and control of robot manipulators with elastic joints. We first derive a simple model to represent the dynamics of elastic joint manipulators. The model is derived under two assumptions regarding dynamic coupling between the actuators and the links, and is useful for cases where the elasticity in the joints is of greater significance than gyroscopic interactions between the motors and links. In the limit as the joint stiffness tends to infinity, our model reduces to the usual rigid model found in the literature, showing the reasonableness of our modeling assumptions. We show that our model is significantly more tractable with regard to controller design than previous nonlinear models that have been used to model elastic joint manipulators. Specifically, the nonlinear equations of motion that we derive are shown to be globally linearizable by diffeomorphic coordinate transformation and nonlinear static state feedback, a result that does not hold for previously derived models of elastic joint manipulators. We also detail an alternate approach to nonlinear control based on a singular perturbation formulation of the equations of motion and the concept of integral manifold. We show that by a suitable nonlinear feedback, the manifold in state space which describes the dynamics of the rigid manipulator, that is, the manipulator without joint elasticity, can be made invariant under solutions of the elastic joint system. The implications of this result for the control of elastic joint robots are discussed.
A Digital Algorithm for Near-Minimum-Time Control of Robot Manipulators
Authors: Kao C. K. , Sinha A. , Mahalanabis A. K.
Published: July 2009

A digital state feedback control algorithm has been developed to obtain the near-minimum-time trajectory for the end-effector of a robot manipulator. In this algorithm, the poles of the linearized closed loop system are judiciously placed in the Z-plane to permit near-minimum-time response without violating the constraints on the actuator torques. The validity of this algorithm has been established using numerical simulations. A three-link manipulator is chosen for this purpose and the results are discussed for three different combinations of initial and final states.
Motion Control Algorithms for Sensor-Equipped Robots
Authors: Shoham M. , Koren Y.
Published: July 2009

This paper deals with the development of kinematic algorithms for the control of sensor-equipped robots. The kinematics is solved in the sensor coordinate system, which reduces the computation efforts, and allows the elimination of the first joint encoder. Simplification of the algorithms can be obtained when approximations are used to solve the inverse kinematics. Three control algorithms based on approximations are presented. However, with these algorithms, convergence to the target is not always guaranteed. A Theorem which specifies the sufficient conditions required for a trajectory to converge to a target point is proved. Based on this Theorem robot parameters can be selected in the design stage of the manipulator. This is illustrated for several types of manipulators.
Optimal Control of Deterministic Systems Described by Integrodifferential Equations Via Chebyshev Series
Authors: Chou Jyh-Horng , Horng Ing-Rong
Published: July 2009

The optimal control problem for deterministic systems described by integrodifferential equations is investigated. Based on the shifted Chebyshev series, a directly computational formulation for evaluating the optimal control and trajectory is developed. The formulation is straightforward and convenient for digital computation. An illustrative example is given to demonstrate the availability of the presently proposed method.
Improved Gradient-Type Algorithms for Zero Terminal Gradient Optimal Control Problems
Authors: Kuo Chung-Feng , Kuo Chen-Yuan
Published: July 2009

Difficulties often arise when we apply the gradient type algorithms employing penalty functions to optimal control problems with variable final time. There is another class of optimal control problems for which the necessary conditions for optimality require a zero gradient at the final time. This causes the gradient-type algorithms, in their standard forms, to become incapable of changing the terminal value of the control variable at each iteration and the rate of convergence is adversely affected. In this paper, we first apply a new transformation method developed by Polak [19] which transforms the variable final time problem into a fixed final time problem. Second, an improved gradient-type algorithm is developed to overcome the zero terminal gradient problem. It is shown that, by applying this transformation and improved algorithm to four examples, not only the variable final time and zero terminal gradient problems are solved and the control vector updated in the correct direction but the rate of convergence of the improved algorithm is faster than that of the traditional gradient-type algorithms.
Performance Evaluation of Medium Access Control Protocols for Distributed Digital Avionics
Authors: Ray Asok
Published: July 2009

The paper presents the results of an ongoing research project where the objectives are to evaluate medium access control (MAC) protocols in view of the requirements for distributed digital flight control systems (DDFCS) of advanced aircraft and to recommend a specific protocol for their prototype development. The selection of an appropriate MAC protocol is critical for the dynamic performance of an aircraft because the DDFCS, in addition to the sampling time delay, is subject to time-varying transport delays due to data latency of messages at different terminals of the control loop. The SAE linear token bus, SAE token ring and the conventional MIL-STD-1553B protocols have been analyzed using combined discrete-event and continuous-time simulation techniques. The impact of data latency on the dynamic performance of an advanced aircraft is illustrated by simulation of the closed loop DDFCS.
A Digital System for the Recording of Impact Velocity, Acceleration and Forming Load of a High Energy Rate Forming Machine
Authors: Derriche O. , Hodgson D. C.
Published: July 2009

A noncontacting device has been developed to measure the instantaneous displacement, velocity, or acceleration of a moving body. The device, based on a solid-state camera, has been used to measure some of the main parameters in a high-speed metal forming operation, though in principle it could be applied to almost any moving body. Errors associated with the digital nature of the measurement are discussed and evaluated.
Modeling and Analysis of an Inherently Multi-Rate Sampling Fuel Injected Engine Idle Speed Control Loop
Authors: Powell B. K. , Cook J. A. , Grizzle J. W.
Published: July 2009

This paper develops a model for the idle speed control of a six cylinder electronically fuel injected, spark ignition engine. The inherently discrete microprocessor based fuel controller is not constrained to operate at the engine’s natural sampling rate, resulting in a hybrid (continuous-discrete) multi-rate system. A method for evaluating the stability of the system is developed.
Stability of Dynamical Systems With Multiple Nonlinearities
Authors: Miyagi Norio , Miyagi Hayao
Published: July 2009

This note applies the direct method of Lyapunov to stability analysis of a dynamical system with multiple nonlinearities. The essential feature of the Lyapunov function used in this note is a non-Lure´ type Lyapunov function which surpasses the Lure´-type Lyapunov function from the point of view of the stability region guaranteed. A modified version of the multivariable Popov criterion is used to construct non-Lure´ type Lyapunov function, which allow for the dynamical sytems with multiple nonlinearities.
Automated Noninvasive Clinical Dehydration Detection Device
Authors: Jiang L. T. , Frischknecht A. , Sienko K. H.
Published: July 2009

Dehydration is a common problem in healthy individuals as well as the elderly and chronically ill. People are often poorly attuned to hydration, and despite widespread awareness of the problem, fatal and near-fatal episodes occur frequently. Typical indicators of hydration status include changes in body weight, urine specific gravity, blood plasma levels, and bioelectrical impedance. Challenges to estimating hydration status from these indicators include the invasive nature of some methods as well as the cost and time required. We have developed a noninvasive device for monitoring hydration status. Our design is inspired by the traditional clinical protocol that approximates fluid loss on the order of 1-2% dehydration by assessing radial pulse before and after a supine to standing transition. The prototype comprises an inertial measurement unit (Xsens MTi) and a wearable heart rate monitor (Polar S810i). In order to compare heart rate behavior under normal and low hydration levels, fluid loss equivalent to 1-4% of the baseline body weight was induced by exercise in three healthy subjects during two data collection sessions. In the first (control) session, subjects replaced fluids every 15 minutes during exercise to maintain their body weight within 0.2% of their baseline value. Fluids were not replaced during the second (test) session, and subjects lost an average of 1.2% of their body weight. Heart rate and body position measurements were recorded before and after exercise while subjects performed repeated supine-to-standing movements and knee-to-chest stretching exercises (supine position only). All post-processing was performed using MATLAB (The MathWorks). Average heart rate was calculated over a 10 second period. Pilot data demonstrates the device's ability to detect hydration changes on the order of 1% in one-third the time required by the traditional clinical protocol (30 seconds compared to 90 seconds). The average rise time from baseline to maximum heart rate and the maximum heart rate following supine-to-standing transitions were significantly longer and greater, respectively, in the dehydrated subjects. Although not statistically significant, the average heart rate during knee-to-chest stretching exercises was elevated in the dehydrated state.
Design of an Endoreactor for the Cultivation of a Joint-Like-Structure
Authors: May E. , Herder J. L. , Kuiper J. H. , Roberts S. , Sivananthan S. , Richardson J. B. , Grünhagen T. , Urban J. , Douglas T. , Warnke P. H. , Martinez I. Z. , Johansen O.
Published: July 2009

To avoid revision surgeries in artificial joint replacements and to allow young people to have a joint replacement, using biological joint replacement created by tissue engineering is a promising alternative. Several research groups have tissue engineered bone [Warnke 2004] and cartilage [Chung 2007] separately. The tissue engineering of a joint, consisting of bone and cartilage is the next frontier. The present study focuses on the design of a novel device, named Endoreactor, that is employing the mechanosensitivity of cells to create a joint-like-structure (JLS) consisting of a bone and cartilage sandwich, similar to an amphiarthrosis, by applying a mechanical loading regime to a stem cell seeded scaffold construct during endocultivation. This way, the patients who will eventually need the new joint will serve as their own bioreactor, having the joint grow in their own body. In the JLS, the outside layers are designed to become bone, using a 6 mm thick scaffold with high stiffness. The center layer is a 4 mm thick scaffold which is compliant so as to experience more strain than the outside scaffolds to stimulate cartilage formation. Compression is realized by placing the JLSs between the long links of a kite-shaped four-bar linkage. This Endoreactor is powered by natural body motion through connection to the musculoskeletal system of the host, which in the experimental phase is a Gottingen minipig. The loading frequency and rest versus active time is dictated by the activity level of the minipig. This results in a natural loading pattern that is employed for the stimulation of cartilage formation in the JLS. A tensile force created during ambulation is converted into compressive action between the two long links of the mechanism. A mechanical stop limits the motion. This way controlled intermittent dynamic compression between 2.5% and 12.5% is realized in the cartilage layer of the JLS. All functions are integrated into a single piece compliant mechanism which is produced out of titanium using 3D rapid prototyping by selective laser melting technology. The mechanism can be fitted with cages that hold the scaffolds for bone and cartilage in place and protect them from external loads while being implanted. A safety spring was added to accommodate for large actuation excursions. A number of prototypes were produced and tested for fatigue, plastic deformation, failure load, and displacements of the long links at the JLS locations under different axial loads. These tests confirmed the proper mechanical functioning of the Endoreactor. Work with animal models making use of the device to culture an amphiarthosis-like joint is foreseen in the near future. This work was carried out at part of MYJOINT: Living Bioreactor—Growing a New Joint in a Human Back, EU FP6-2004-NEST-C-1, Proposal No. 028861.
Design Optimization of Single-Port Minimally Invasive Intervention Devices
Authors: Hammond F. , Shimada K. , Zenati M.
Published: July 2009

Despite the success of multiple-port minimally invasive intervention (MII) systems, current research is fast moving away from standard, kinematically rigid MII instruments toward more flexible, highly articulated devices, such as robotic catheters, probes, and forceps. These new devices afford surgeons the same dexterity and range of motion as multiple-port systems while using only a single incision. Single-port MII devices hold the promise of facilitating procedures in small, geometrically complex spaces, such as those seen cardiothoracic surgery, with even lower risks of infection and patient discomfort than possible with multiple-port systems. However, the mechanical sophistication of these robotic devices requires careful consideration of morphological design to ensure that the complexity and cost of design is not economically prohibitive enough to outweigh the clinical benefits of improved robot flexibility. This study focuses on the intelligent design of a kinematically redundant, single-port MII robot architecture by way of morphological optimization. This MII device morphology is optimized to access the cardiothoracic cavity through a single 12 mm subxiphoid port and reach several regions of interest, consistent with procedures such as epicardial ablation and therapeutic substance injection, with minimal physiologic disturbance. The optimization process employs a recently developed morphological fitness metric to measure a candidate morphology's ability to navigate the cardiothoracic environment and perform surgical maneuvers with high end-effector flexibility while maintaining safe distances from anatomical structures. This fitness metric uses a Jacobian-based formulation to quantify a robot's capacity to avoid collisions with motion impediments and to minimize the mechanical torque required for the intended task. In addition to performance-based criterion, this optimization process also considers design factors such as part manufacturability and expense which heavily influence economic feasibility. Morphological optimization is performed by searching the mechanical design parameter space, which consists of part dimensions and linkage types, using genetic algorithms. The execution of specific surgical maneuvers is simulated for each candidate morphology until the fitness metric is maximized. Final simulations of the optimized device morphology working in the cardiothoracic cavity are performed to demonstate the functional advantages of the optimized single-port robot over current multiple-port systems.
A Cardiac Sound Reproduction Apparatus for Improved Stethoscope Testing
Authors: Nordehn G. , Ulseth R. , Bartek T. , McDonald B. , McNally A. , Menart M. , Eames S. , Flynn M. , Blaire B. , Drewek A. , Branson E. , Burns S.
Published: July 2009

Valvular heart disease is a significant problem. The primary case physician initially does assessment through auscultation. Accuracy in classification of sounds is suboptimal (20 to 40%). Lower frequencies of heart sounds are important in classification of murmurs associated with valvular heart disease. We find stethoscope sound intensity capture falls significantly at the 1500 Hz range and lower. Strategies to improve auscultation accuracy include improving stethoscope features or developing a device that, when used with the stethoscope, augments sound capturing abilities at lower frequencies. Testing necessitated development of a reliable (without significant intra-sound variation) cardiac sound reproduction device. A sound permeable contracting polymer when used with a stethoscope signficantly increases sound intensity captured in the 625 Hz to 1500 Hz range, when tested with a reliable cardiac sound reproduction device. We prepared an air-sealed device with an amplifier, four internal speakers capable of emitting high quality, low frequency sounds, and a listening pad. An existing electronic stethoscope with, and then without, a sound permeable contracting polymer captured three sounds (normal, innocent systolic murmur, pathological systolic murmur) five times per sound. The sounds were placed in computer files. FFTs were constructed. Sound intensity within the 625 Hz to 1400 Hz range, when the sound permeable contracting polymer is used with the electronic stethoscope, relatively improves, on average, approximately 11 dB, compared to sound captured with the same electronic stethoscope without the sound permeable contracting polymer. This difference is numerically statistically significant (p<0.001). Intra-sound variability testing (standard deviation) of FFTs was not significant. A sound permeable contracting polymer used with an electronic recording stethoscope significantly improves sound intensity in an important auscultation frequency range. Intra-sound testing variation was insignificant. A study is underway to demonstrate impact using an absolute reference point. However, as amplification within existing electronic stethoscopes is commercially available, potential variation in relative reference points may be overcome with existing amplification features on electronic stethoscopes, allowing improved capture of heart sounds within the 625 Hz to 1400 Hz range. Limitations include the need for human subject study. Further testing, including human subjects testing is needed prior to application for FDA approval. FDA approval is needed before any use on humans. The methodology should not be utilized clinically without FDA approval.
Innovation and Design: Pollution Prevention Opportunities in Medical Device Design
Authors: Becker J. , Zimmer C. , Larson K.
Published: July 2009

A wide variety of materials and chemicals are used in the development, production, cleaning, packaging, sterilization and shipment of medical devices. Some of these materials are used in large quantities and are often a source of waste. Some materials, such as poly vinyl chloride (PVC) plastics, have toxicity concerns. Additionally, many chemicals including chlorinated solvents and ethylene oxide are carcinogenic or highly toxic and can be detrimental to the environment and public health. While the medical device industry is highly regulated in the United States by the Food and Drug Administration, new green initiatives in the European Union are modifying the regulatory oversight of chemicals, materials, and their manufacture. In addition, hospitals are working to reduce waste and pollution as part of their operations and are increasingly asking vendors to assist them. Minimizing waste and pollution associated with medical devices can improve a company's environmental performance and save money. The primary focus in medical device manufacturing is patient safety and compatibility. Environmental considerations, which can include potential cost savings, are often overlooked in the design and process development phases. Numerous pollution prevention and energy efficiency options exist for medical device manufacturers. These options can be integrated into the development, design and process protocols, and engineering change orders when designing a new product or improving an existing part. By having a process design evaluation plan that includes environmental considerations, companies can effectively manage the creation of waste streams, toxicity of material inputs, and process efficiencies as a mechanism at both the front-end and the duration of the product line. These options often cut costs and can help reduce current and prospective regulatory burdens. The Minnesota Technical Assistance Program (MnTAP) at the University of Minnesota has been assisting businesses with pollution prevention and cost savings for 25 years. MnTAP's engineers and scientists have worked with the medical device industry to reduce the quantity of packaging and waste associated with cardiac catheters, reduce the use of toxic cleaning solvents, minimize the use of PVC, and research safer disinfection and sterilization methods. This poster includes case studies of the above mentioned projects, an overview of less toxic sterilization methods, and tools for medical device manufacturing that meet FDA requirements, but reduce waste and toxicity during production and use.
Design of a Novel Perfusion System to Perform MR Imaging of an Isolated Beating Heart
Authors: Eggen M. , Swingen C. , Matta P. , Bateman M. , Rolfes C. , Quill J. , Richardson E. , Howard S. , Iaizzo P.
Published: July 2009

Isolated mammalian hearts have been used to study cardiac physiology, pharmacology, and biomedical devices in order to separate myocardial characteristics from the milieu of the intact animal and to allow for increased control over experimental conditions. Considering these benefits and that MRI is the “gold” standard for measuring myocardial function, it was considered desirable to have a system which would allow simultaneous MR imaging of an isolated beating heart. Here we describe a unique portable system, which enables physiologic perfusion of an isolated heart during simultaneous MR imaging. A two unit system was designed to physiologically support a large mammalian isolated heart during MR imaging were a modified Krebs-Henseleit perfusate was used as a blood substitute. The first unit, which resides in an adjacent support room next to the scanner, contains all electronically powered equipment and components (with ferromagnetic materials) which cannot operate safely near the magnet, including (1) a thermal module and custom tube in tube heat exchanger warming the perfusate to 38°C; (2) a carbogen tank (95% O2 5% CO2) and hollow fiber oxygenator; and (3) two centrifugal blood pumps which circulates and pressurizes the left and right atrial filling chambers. The second unit, which resides next to the magnet and is free of ferromagnetic materials, receives warmed, oxygenated perfusate from the first unit via PVC tubing. The isolated hearts were connected to the second unit via four cannulae sutured to the great vessels. A support system placed inside the scanner on the patient bed secured the hearts and cannulae in the correct anatomical position. To date, this system was tested in a 1.5 T Siemens scanner using swine hearts (n=2). The hearts were arrested with St. Thomas cardioplegia and removed via a medial sternotomy. After cannulation of the great vessels, reperfusion, and defibrillation, four-chamber and tagged short-axis cine loops were acquired using standard ECG gating. Tagged short-axis images obtained at the base, mid-ventricle, and apex were used to measure the following functional parameters for one heart: LV end-diastolic volume=38.84 ml, LV end-systolic volume=23.23 ml, LV stroke volume=15.6 ml, LV ejection fraction=40.18%, and peak LV circumferential strain=16%. The feasibility of MR imaging an isolated, four-chamber working large mammalian heart was demonstrated using a custom designed and built portable MRI compatible perfusion system. This system will be useful in studying in vitro cardiac function (including human hearts) and developing MRI safe biomedical devices and MRI guided therapies in a controlled setting.
Silicon Eye
Authors: Thuvvakkadan S. , Nair V. J.
Published: July 2009

Silicon eye can be otherwise called as a complete eye implant. The project overview is given in brief by the description of main components. Here in the silicon eye, a biconcave gel lens is used in connection with a micro controller. A porous silicon nano photodiode is placed before the gel lens. This specially designed transparent diode will help in identifying the intensity of light receiving in the beginning of the processing chain. An effective drainage system (with the help of two valves) will control the working of gel lens. All these components together form the primary circuit to enable the process of auto focusing. The micro controller is connected with all components of the system. The primary circuit is connected to a secondary circuit which consists of an artificial silicon retina and a chemical synapse. By the combined and co-ordinate working of both these will enable vision. The power supply, which all the electrical components here need is given by a series of nano paper batteries placed beneath the retinal layer (carbon nano tubes can also be implemented instead or along with it). The converted electrical impulses (from intensity of light received) will be carried to the visual area of brain through optic nerve by the effective interaction with a number of artificial chemical synapses. Finally this silicon eye will be an effective implant for the damaged eye. And we are sure that this will be a great breakthrough in the modern medicine.
The Development of a Novel Adaptive Seating System for Children with Neuromuscular Disorders
Authors: Telfer S. , Solomonidis S. , Spence W.
Published: July 2009

Adaptive seating has been defined as the customized prescription and application of sitting support devices based on therapeutic principles. It is recognized that for children with neuromuscular disorders that result in poor postural control, a comfortable adaptive seating system that provides them with the support needed to maintain a sitting position can be essential for raising their overall level of well being. These systems are also used to try and prevent or to slow the progression of skeletal deformities. However, problems with current adaptive seating systems do exist. After extensive research into these problems we developed a novel adaptive seating system which aims to improve on current designs. It includes a number of innovative features including

• Active dynamic supports: The backrest and headrest are mounted on gas springs, allowing them to move in order to accommodate the user's task induced movement or abnormal muscle tone. The forces applied to and the position of the supports are monitored and used to control motors attached to the gas springs. This means that the user can, when required, be returned to their original position in a controlled but still dynamic manner. The “floating” nature of these supports, especially the backrest, is also intended to allow for some growth of the user.

• Novel backrest shape: In an attempt to positively influence abnormal hip extensor tone, the user's trunk is given a predominantly lateral rather than posterior type of support. Preliminary results suggest that this approach could have some beneficial effects in terms of reducing abnormal hip extensor tone.

• Multi-planar tilting seat base: Tilting of the base in the saggital and coronal planes can be actuated manually or pre-programmed to do so automatically at set intervals. This aims to improve user comfort and prevent the development of pressure sores and could also be used to accommodate deformities such as pelvic obliquities.

Through these features the novel system has the potential to provide improved comfort, support and functionality for the users and to reduce the burden place on those who care for them.
Variable Self-Optimizing Cochlear Model for Heart Murmur Detection/Classification
Authors: Ahmad W. , Hayee M. I. , Nordehn G. , Burns S. , Fitzakerley J. L.
Published: July 2009

Accurate detection and classification of heart murmurs by auscultation is suboptimal and not always definitive. The murmur information perceived by the physician brain is the combined effect of both patient's (human) heart and the physician's ear. The information containing the murmur characterization which is retrieved by the human brain resides in the electrical signal coming out of the cochlea. For the very reasons described here, cochlea-like processing has been successfully applied to multiple speech recognition related technologies. This had not, before our prior work, been applied to human heart murmur analysis. Our prior research consisted of three steps: (1) capturing heart sounds, (2) processing the sounds using a cochlea-like filter, and then, (3) classifying each sound as being normal or a murmur using an artificial neural network (ANN). Previously in our research, we used a static cochlea-like filter model in step 2 as described above, which resulted a significant improvement in terms of accuracy of heart murmur classification. Our cochlear filter analysis helped identify information-rich frequency segments in human heart sound. We want to advance the cochlear filter model from a static to a variable frequency selective model with feedback from ANN for better optimization of the heart murmur classification. The heart sounds will be processed in ways more closely replicating the human cochlea than the static cochlear filter. A variable self optimizing cochlear filter will better reproduce the mechanism of the human cochlea in that it will contain a feedback system from ANN to cochlear processing to automatically select the most useful frequencies based upon a threshold mechanism filtering out those frequencies which do not contain significantly useful information about classification of heart murmur. The output of the sounds in the frequency range remaining (variable self-optimizing cochlear filtered sounds) may then be used by the neural network to make a final decision about murmur classification. Our hypothesis is that a variable self-optimizing cochlear filter will significantly improve the accuracy in classification of heart sounds as normal or murmur when compared to a static cochlear filter. Using this approach, we plan to develop an AI based system which will classify heart sounds with a success rate significantly better than the static cochlear filter previously developed.