scholarly journals Clinical applications of neurochemical and electrophysiological measurements for closed-loop neurostimulation

2020 ◽  
Vol 49 (1) ◽  
pp. E6 ◽  
Author(s):  
J. Blair Price ◽  
Aaron E. Rusheen ◽  
Abhijeet S. Barath ◽  
Juan M. Rojas Cabrera ◽  
Hojin Shin ◽  
...  
Keyword(s):  
Real Time ◽  
Closed Loop ◽  
Neurological Diseases ◽  
Pulse Frequency ◽  
Open Loop ◽  
Compulsive Disorder ◽  
Specific Disease ◽  
Disease States ◽  
Stimulation Parameters ◽  
The Individual

The development of closed-loop deep brain stimulation (DBS) systems represents a significant opportunity for innovation in the clinical application of neurostimulation therapies. Despite the highly dynamic nature of neurological diseases, open-loop DBS applications are incapable of modifying parameters in real time to react to fluctuations in disease states. Thus, current practice for the designation of stimulation parameters, such as duration, amplitude, and pulse frequency, is an algorithmic process. Ideal stimulation parameters are highly individualized and must reflect both the specific disease presentation and the unique pathophysiology presented by the individual. Stimulation parameters currently require a lengthy trial-and-error process to achieve the maximal therapeutic effect and can only be modified during clinical visits. The major impediment to the development of automated, adaptive closed-loop systems involves the selection of highly specific disease-related biomarkers to provide feedback for the stimulation platform. This review explores the disease relevance of neurochemical and electrophysiological biomarkers for the development of closed-loop neurostimulation technologies. Electrophysiological biomarkers, such as local field potentials, have been used to monitor disease states. Real-time measurement of neurochemical substances may be similarly useful for disease characterization. Thus, the introduction of measurable neurochemical analytes has significantly expanded biomarker options for feedback-sensitive neuromodulation systems. The potential use of biomarker monitoring to advance neurostimulation approaches for treatment of Parkinson’s disease, essential tremor, epilepsy, Tourette syndrome, obsessive-compulsive disorder, chronic pain, and depression is examined. Further, challenges and advances in the development of closed-loop neurostimulation technology are reviewed, as well as opportunities for next-generation closed-loop platforms.

scholarly journals Closed-loop conductance scanning tunneling spectroscopy: demonstrating the equivalence to the open-loop alternative

2015 ◽  
Vol 6 ◽  
pp. 1116-1124 ◽  
Author(s):  
Chris Hellenthal ◽  
Kai Sotthewes ◽  
Martin H Siekman ◽  
E Stefan Kooij ◽  
Harold J W Zandvliet
Keyword(s):  
Closed Loop ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Open Loop ◽  
Scanning Tunneling ◽  
Image Charge ◽  
Tunneling Barrier ◽  
Molecular Systems ◽  
Individual Contributions ◽  
The Individual

We demonstrate the validity of using closed-loop z(V) conductance scanning tunneling spectroscopy (STS) measurements for the determination of the effective tunneling barrier by comparing them to more conventional open-loop I(z) measurements. Through the development of a numerical model, the individual contributions to the effective tunneling barrier present in these experiments, such as the work function and the presence of an image charge, are determined quantitatively. This opens up the possibility of determining tunneling barriers of both vacuum and molecular systems in an alternative and more detailed manner.

Controlling Nylon Dyeing by Dye and Chemical Metering

1997 ◽  
Vol 67 (8) ◽  
pp. 609-616 ◽  
Author(s):  
Ralph McGregor ◽  
Manpreet S. Arora ◽  
Warren J. Jasper
Keyword(s):  
Adaptive Control ◽  
Binary Mixture ◽  
Real Time ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Good Reproducibility ◽  
Acid Dyes ◽  
Loop Control ◽  
Polyamide Fibers ◽  
The Individual

Closed-loop control of the dosing of dyes and chemicals is used to obtain an on-tone build-up of shade in dyeing polyamide fibers with a binary mixture of monosulfonated acid dyes. Computerized dosing pumps control the pH, the dyebath concentrations of the individual dyes, and the total sorption of each dye during the process. This real-time, closed-loop adaptive control yields good reproducibility and uniform shade build-up in a laboratory dyeing machine. It is possible to reuse a dyebath containing residual dyes and chemicals from a previous dyeing.

scholarly journals Generic characterization of electrical test benches for AC- and HVDC-connected wind power plants

2020 ◽  
Vol 5 (2) ◽  
pp. 561-575
Author(s):  
Behnam Nouri ◽  
Ömer Göksu ◽  
Vahan Gevorgian ◽  
Poul Ejnar Sørensen
Keyword(s):  
Real Time ◽  
Wind Power ◽  
Wind Turbines ◽  
Closed Loop ◽  
Short Circuit ◽  
Open Loop ◽  
Device Under Test ◽  
Generic Structure ◽  
Electrical Test ◽  
Grid Connection

Abstract. The electrical test and assessment of wind turbines go hand in hand with standards and network connection requirements. In this paper, the generic structure of advanced electrical test benches, including grid emulator or controllable grid interface, wind torque emulator, and device under test, is proposed to harmonize state-of-the-art test sites. On the other hand, modern wind turbines are under development towards new features, concerning grid-forming, black-start, and frequency support capabilities as well as harmonic stability and control interaction considerations, to secure the robustness and stability of renewable-energy-based power systems. Therefore, it is necessary to develop new and revised test standards and methodologies to address the new features of wind turbines. This paper proposes a generic test structure within two main groups, including open-loop and closed-loop tests. The open-loop tests include the IEC 61400-21-1 standard tests as well as the additional proposed test options for the new capabilities of wind turbines, which replicate grid connection compliance tests using open-loop references for the grid emulator. In addition, the closed-loop tests evaluate the device under test as part of a virtual wind power plant and perform real-time simulations considering the grid dynamics. The closed-loop tests concern grid connection topologies consisting of AC and HVDC, as well as different electrical characteristics, including impedance, short-circuit ratio, inertia, and background harmonics. The proposed tests can be implemented using available advanced test benches by adjusting their control systems. The characteristics of a real power system can be emulated by a grid emulator coupled with real-time digital simulator systems through a high-bandwidth power-hardware-in-the-loop interface.

scholarly journals Design Considerations for Long Term Non-invasive Brain Computer Interface Training With Tetraplegic CYBATHLON Pilot

2021 ◽  
Vol 15 ◽  
Author(s):  
Neethu Robinson ◽  
Tushar Chouhan ◽  
Ernest Mihelj ◽  
Paulina Kratka ◽  
Frédéric Debraine ◽  
...  
Keyword(s):  
Real Time ◽  
Closed Loop ◽  
Brain Computer Interface ◽  
Brain Activation ◽  
Classification Performance ◽  
Open Loop ◽  
Computer Interface ◽  
Single Subject ◽  
User Engagement

Several studies in the recent past have demonstrated how Brain Computer Interface (BCI) technology can uncover the neural mechanisms underlying various tasks and translate them into control commands. While a multitude of studies have demonstrated the theoretic potential of BCI, a point of concern is that the studies are still confined to lab settings and mostly limited to healthy, able-bodied subjects. The CYBATHLON 2020 BCI race represents an opportunity to further develop BCI design strategies for use in real-time applications with a tetraplegic end user. In this study, as part of the preparation to participate in CYBATHLON 2020 BCI race, we investigate the design aspects of BCI in relation to the choice of its components, in particular, the type of calibration paradigm and its relevance for long-term use. The end goal was to develop a user-friendly and engaging interface suited for long-term use, especially for a spinal-cord injured (SCI) patient. We compared the efficacy of conventional open-loop calibration paradigms with real-time closed-loop paradigms, using pre-trained BCI decoders. Various indicators of performance were analyzed for this study, including the resulting classification performance, game completion time, brain activation maps, and also subjective feedback from the pilot. Our results show that the closed-loop calibration paradigms with real-time feedback is more engaging for the pilot. They also show an indication of achieving better online median classification performance as compared to conventional calibration paradigms (p = 0.0008). We also observe that stronger and more localized brain activation patterns are elicited in the closed-loop paradigm in which the experiment interface closely resembled the end application. Thus, based on this longitudinal evaluation of single-subject data, we demonstrate that BCI-based calibration paradigms with active user-engagement, such as with real-time feedback, could help in achieving better user acceptability and performance.

scholarly journals Real-time synthesis of imagined speech processes from minimally invasive recordings of neural activity

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Miguel Angrick ◽  
Maarten C. Ottenhoff ◽  
Lorenz Diener ◽  
Darius Ivucic ◽  
Gabriel Ivucic ◽  
...  
Keyword(s):  
Real Time ◽  
Neural Activity ◽  
Communication Channel ◽  
Closed Loop ◽  
Open Loop ◽  
Depth Electrodes ◽  
Whispered Speech ◽  
Frontal Activity ◽  
Synthesis Approach

AbstractSpeech neuroprosthetics aim to provide a natural communication channel to individuals who are unable to speak due to physical or neurological impairments. Real-time synthesis of acoustic speech directly from measured neural activity could enable natural conversations and notably improve quality of life, particularly for individuals who have severely limited means of communication. Recent advances in decoding approaches have led to high quality reconstructions of acoustic speech from invasively measured neural activity. However, most prior research utilizes data collected during open-loop experiments of articulated speech, which might not directly translate to imagined speech processes. Here, we present an approach that synthesizes audible speech in real-time for both imagined and whispered speech conditions. Using a participant implanted with stereotactic depth electrodes, we were able to reliably generate audible speech in real-time. The decoding models rely predominately on frontal activity suggesting that speech processes have similar representations when vocalized, whispered, or imagined. While reconstructed audio is not yet intelligible, our real-time synthesis approach represents an essential step towards investigating how patients will learn to operate a closed-loop speech neuroprosthesis based on imagined speech.

EFFECT OF STIMULUS PARAMETERS IN THE TREATMENT OF SEIZURES BY ELECTRICAL STIMULATION IN THE KAINATE ANIMAL MODEL

2011 ◽  
Vol 21 (02) ◽  
pp. 151-162 ◽  
Author(s):  
POOJA RAJDEV ◽  
MATTHEW WARD ◽  
PEDRO IRAZOQUI
Keyword(s):  
Electrical Stimulation ◽  
Pulse Width ◽  
Closed Loop ◽  
Seizure Activity ◽  
Open Loop ◽  
Stimulation Frequency ◽  
Total Charge ◽  
Stimulation Parameter ◽  
Loop Control ◽  
Stimulation Parameters

Preliminary results from animal and clinical studies demonstrate that electrical stimulation of brain structures can reduce seizure frequency in patients with refractory epilepsy. Since most researchers derive stimulation parameters by trial and error, it is unclear what stimulation frequency, amplitude and duration constitutes a set of optimal stimulation parameters for aborting seizure activity in a given patient. In this investigation, we begin to quantify the independent effects of stimulation parameters on electrographic seizures, such that they could be used to develop an efficient closed-loop prosthesis that intervenes before the clinical onset of a seizure and seizure generalization. Biphasic stimulation is manually delivered to the hippocampus in response to a visually detected electrographic seizure. Such focal, responsive stimulation allows for anti-seizure treatment delivery with improved temporal and spatial specificity over conventional open-loop stimulation paradigms, with the possibility of avoiding tissue damage stemming from excessive exposure to electrical stimulation. We retrospectively examine the effects of stimulation frequency (low, medium and high), pulse-width (low and high) and amplitude (low and high) in seizures recorded from 23 kainic acid treated rats. We also consider the effects of total charge delivered and the rate of charge delivery, and identify stimulation parameter sets that induce after-discharges or more seizures. Among the stimulation parameters evaluated, we note 2 major findings. First, stimulation frequency is a key parameter for inhibiting seizure activity; the anti-seizure effect cannot be attributed to only the charge delivered per phase. Second, an after-discharge curve shows that as the frequency and pulse-width of stimulation increases, smaller pulse amplitudes are capable of eliciting an after-discharge. It is expected that stimulation parameter optimization will lead to devices with enhanced treatment efficacies and reduced side-effect profiles, especially when used in conjunction with seizure prediction or detection algorithms in a closed-loop control application.

scholarly journals Design of a Research Laboratory Drive System for a Synchronous Reluctance Motor for Vector Control and Performance Analysis

Inventions ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 64
Author(s):  
Hamidreza Heidari ◽  
Anton Rassõlkin ◽  
Ants Kallaste ◽  
Toomas Vaimann ◽  
Ekaterina Andriushchenko ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Vector Control ◽  
Real Time ◽  
Research Laboratory ◽  
Closed Loop ◽  
Open Loop ◽  
Drive System ◽  
Control Algorithms ◽  
Synchronous Reluctance Motor ◽  
Reluctance Motor

Motor-drive systems have the most significant share in industrial energy consumption, which requires a deep study in every aspect of the field. This paper presents a synchronous reluctance motor (SynRM) drive system based on Plecs RT box 1. The system’s design provides the opportunity for the open-loop and closed-loop control of the motor and a characteristic performance analysis of the motor. This paper focuses on the hardware implementation of a research laboratory setup and the precise vector control of the SynRM in real-time. The application of the digital controller and inverter to drive SynRM is examined. The voltage, current, and speed transducers were employed for monitoring the protective measures and to control the motor in the closed-loop. The design of the signal conditioning and the intermediary cards for isolation and data acquisition are described in detail. An algorithm is proposed to measure the whole system parameters, including motor, inverter, and cables. Thanks to the RT box 1, the principle of real-time simulation of control algorithms is investigated, and the rapid control prototyping of field-oriented control (FOC) of SynRM was implemented. The simulation of the system was carried out in the Plecs platform, and the results are presented. The experimental results of the implemented control algorithms validate the setup’s performance and the control algorithm. Finally, as a study of the motor’s performance, the efficiency map of the motor is drawn in different speed and torque ranges.

Closing the loop

2011 ◽  
pp. 1869-1874
Author(s):  
Roman Hovorka
Keyword(s):  
Type 1 Diabetes ◽  
Real Time ◽  
Closed Loop ◽  
Insulin Delivery ◽  
Insulin Analogues ◽  
Open Loop ◽  
Subcutaneous Insulin ◽  
Closed Loop Systems ◽  
Acting Insulin

The standard therapy of type 1 diabetes is based on multiple daily injections of short- and long acting-insulin analogues accompanied by blood glucose self-monitoring. However, treatment goals identified by the Diabetes Control and Complications Trial are difficult to achieve due, at least in part, to a high risk of hypoglycaemia associated with many currents forms of intensive insulin therapy. Recent technological developments in real-time subcutaneous continuous glucose monitoring (CGM), combined with the continuous subcutaneous insulin infusion (CSII), could potentially reduce this risk. Since late 1990s at least five continuous or semicontinuous glucose monitors have received regulatory approval (1). CGM has been shown to improve glycaemic control in adults with type 1 diabetes, although apparent barriers to effectiveness in children and adolescents remain to be identified (see Chapter 13.4.9.1) (2). The availability of commercial CGM devices has reinvigorated research towards closed-loop systems (3-6), in which insulin is delivered according to real-time needs, as opposed to open-loop systems, which lack real-time responsiveness to changing glucose concentrations. Closed-loop insulin delivery, in which the insulin delivery is informed by the measured glucose concentrations has the potential gradually to revolutionize the management of type 1 diabetes by reducing or eliminating the risk of hypoglycaemia while achieving near-normal glucose levels. A closed-loop system, also called the ‘artificial pancreas’, comprises three components: a CGM device to measure real-time glucose concentration, a titrating algorithm to compute the amount of insulin needed, and an insulin pump delivering a rapid-acting insulin analogue (see Fig. 13.4.9.2.1). Only a few prototypes have been developed. Progress has been hindered by suboptimal accuracy and reliability of CGM devices, the relatively slow absorption of subcutaneously administered ‘rapid’-acting insulin analogues, and the lack of adequate control algorithms. So far, testing has been confined to the clinical setting. However, a concentrated effort promises an accelerated progress towards home testing of closed-loop systems. The research focus centres on systems utilizing subcutaneous glucose sensing and subcutaneous insulin delivery. This approach has the greatest potential for a near-future commercial exploitation, although other approaches utilizing intraperitoneal or intravenous sensing/delivery are, in principle, also feasible.

scholarly journals Multisensory Testing Framework for Advanced Driver Assistant Systems Supported by High-Quality 3D Simulation

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8458
Author(s):  
Paweł Jabłoński ◽  
Joanna Iwaniec ◽  
Michał Jabłoński
Keyword(s):  
Real Time ◽  
Closed Loop ◽  
Detection Algorithm ◽  
Test System ◽  
Open Loop ◽  
Present System ◽  
High Quality ◽  
System Architectures ◽  
The Real ◽  
Assistant Systems

ADAS and autonomous technologies in vehicles become more and more complex, which increases development time and expenses. This paper presents a new real-time ADAS multisensory validation system, which can speed up the development and implementation processes while lowering its cost. The proposed test system integrates a high-quality 3D CARLA simulator with a real-time-based automation platform. We present system experimental verifications on several types of sensors and testing system architectures. The first, open-loop experiment explains the real-time capabilities of the system based on the Mobileye 6 camera sensor detections. The second experiment runs a real-time closed-loop test of a lane-keeping algorithm (LKA) based on the Mobileye 6 line detection. The last experiment presents a simulation of Velodyne VLP-16 lidar, which runs a free space detection algorithm. Simulated lidar output is compared with the real lidar performance. We show that the platform generates reproducible results and allows closed-loop operation which, combined with a real-time collection of event information, promises good scalability toward complex ADAS or autonomous functionalities testing.

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