Publication Date: 2021
AEU - International Journal of Electronics and Communications (16180399)140
Sensor nodes and IoT systems require blocks that not only consume low power but also have good accuracy. Voltage reference generators are also considered important building blocks in sensor interface circuits. This paper presents a solution to increase the accuracy of low power subthreshold voltage generators by lowering the circuit sensitivity to temperature and supply voltage variations. The enhancement is achieved by using two separate stages for temperature coefficient (TC) and line sensitivity (LS) correction. A 0.18 µm standard CMOS process has been used for the proposed structure. The effects of parameter variations in the fabrication process are investigated using post-layout simulation and Monte Carlo analysis. In the supply voltage of 0.4–2 V, an LS of 143.8 ppm/V is obtained. In typical corner conditions, the achieved TC is 7.45 ppm/°C over the temperature range of 0–80 °C. Due to process changes, and mainly affected by threshold voltage variations, the average TC can change to 39.2 ppm/°C. The minimum power consumption at 0 °C and at a supply voltage of 0.4 V is 3.25 pW while the power consumption increases to 2.84 nW in 80 °C and at the maximum supply voltage of 2 V. © 2021 Elsevier GmbH
Habibi, M.,
Shahpari n., N.,
Habibi M.,
Malcovati p., ,
De La Rosa J.M. Publication Date: 2023
IEEE Access (21693536)11pp. 67113-67125
The input capacitance of the SAR ADC is considered a drawback in many applications. In this paper, a 12-bit low-power SAR ADC with low-input capacitance is proposed. The ADC is based on a separated DAC and sample-and-hold blocks (SB) structure. The SB structure suffers from variation in the input common-mode voltage of the comparator, leading to nonlinear input-referred offset and kickback noise. Here, a closed-loop low-power rail-to-rail offset cancellation technique for the comparator, based on body voltage tuning, is proposed. In order to stabilize the closed loop structure, the open loop gain is controlled by adapting the gain of the preamplifier. Using this structure, the rail-to-rail offset is kept lower than 110 mu V and the overall power of the comparator is 1 pJ/Conv. Complementary-clocked dynamic branches are exploited at the input of the comparator to decrease the common-mode dependent kickback noise error to less than 1 LSB. The bootstrapped switch's controlling signal is also modified to achieve less than 1 LSB error and 18.9% lower power consumption. The proposed ADC is designed in standard 180 nm CMOS technology with a 1.8 V supply voltage and the input capacitance is reduced to 2 pF, which leads to power consumption of 41 nW in the input voltage supply. Electrical simulations including PVT, MonteCarlo, and post-layout parasitic extraction were conducted to ensure the effectiveness of the approach. The ADC features an ENOB of 11.1-bit and a sampling rate of 1 MHz with a power consumption of 117.9 mu W including the input power supply which are competitive with the state-of-the-art, and demonstrate the virtue of the proposed approach.
Publication Date: 2025
IET Power Electronics (17554543)18(1)
This paper presents a novel high-performance and dependable step-up multi-level inverter topology designed specifically for photovoltaic applications. A gain factor of nine is attained, coupled with automatic self-voltage balancing of capacitors and the intrinsic capability to generate both positive and negative voltage levels. All power switches withstand voltages lower than the peak of the output voltage. The quantity of power switches, DC input sources, and the blocking voltage on the switches are reduced. Also, the proposed inverter demonstrates a minimal cost function in comparison to similar topologies. The performance of the 19-level step-up inverter has been confirmed through simulation as well as laboratory results obtained from a constructed prototype. © 2025 The Author(s). IET Power Electronics published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Previous methods for narrowband interference suppression in spread spectrum systems require training sequences. In practical overlay systems, transmission of the training sequences is impossible, because narrowband system and spread spectrum system are two separate entities, and presently the narrowband systems are in use and standardized and any changes may not be allowed. Hence, the narrowband systems cannot transmit training sequences for the spread spectrum system. In this paper we present a blind method for narrowband interference suppression in direct sequence Code Division Multiple Access (CDMA) systems. The proposed scheme is a nonlinear predictor consisting of a non-linear device and two random walk tracking algorithms. The main feature of this approach is that it does not require training sequences for tracking and suppressing narrowband interference. Simulation results show that in multiuser case, the performance of the proposed approach is better than Kalman filter. © 2004 IEEE.
Publication Date: 2009
Chaos, Solitons and Fractals (09600779)42(3)pp. 1755-1765
In this paper, a chattering-free sliding mode controller design for uncertain chaotic systems is presented. Since the implementation of the sliding mode control may cause a significant problem of chattering, many modified methodologies have been developed to overcome this drawback. However, each of them has own problems such as lack of robustness against disturbance variations, steady-state error, large convergence time and effect on transient performance. This paper proposes an improved sliding mode control strategy in which a modified sliding condition in a continuous function in control signal is taken into account instead of discontinuous part and also it adds an auxiliary continuous control to the control input. Then, the stability of controlled system is proved by using Lyapunov's direct method. The usefulness of this proposed method for eliminating the chattering phenomenon in transient and steady states, in the face of uncertain chaotic systems with disturbances, is well appeared. For this purpose, the Lorenz system is studied and its simulation results are presented to demonstrate the effectiveness of the proposed control scheme. © 2009 Elsevier Ltd. All rights reserved.
Publication Date: 2011
Expert Systems with Applications (0957-4174)38(10)pp. 12643-12653
Precise speed control of an Interior Permanent Magnet Synchronous Motor (IPMSM) drive becomes a complex issue due to the nonlinear nature of its developed torque. The system nonlinearity becomes severe when the IPMSM drive operates in the field weakening region. In order to achieve perfect control characteristics, the main purpose of this paper is to present a detailed comparison of various intelligent based controllers for flux weakening speed control of an IPMSM drive. In this paper, the Brain Emotional Learning Based Intelligent Controller (BELBIC), Genetic-Fuzzy Logic Based Controller (GFLBC), as well as genetic-PI based controller, are considered. BELBIC is a computational model of emotional processing mechanism in the brain. The effectiveness of the proposed BELBIC controller-based IPMSM drive is verified by simulation results at different operating conditions. Moreover, control regimes such as Maximum Torque Per Ampere (MTPA) control and flux weakening (FW) control as well as voltage and current constraints have been successfully applied. The results prove BELBIC's perfect control characteristics, such as fast and smooth speed response, low maximum starting current, adaptability to speed and load changes and robustness to parameter variations, disturbance and sudden one-phase interruption. © 2010 Elsevier Ltd. All rights reserved.
Publication Date: 2014
Advances in Polymer Technology (07306679)33(S1)
This paper addresses the preparation of polyaniline (PAni) and polypyrrole (PPy) nanostructures as humidity sensor elements. The semicrystalline microstructure and chemical structure of synthesized PAni and PPy were studied by X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The morphology of these polymers was studied by scanning electron microscopy and transmission electron microscopy, indicating fibrillar and tubular nanostructures for PAni and PPy, respectively. The humidity sensing performances of sensors based on the prepared nanostructural PAni and PPy were investigated, and the sensing mechanisms of both systems have been discussed. The interesting reverse behaviors during humidity exposure of PAni- and PPy-based sensors in different water vapor concentrations have been comprehensively justified. The temperature dependency of the electrical conductivity for PAni and PPy samples was investigated. The UV-vis spectroscopy was used to study the effect of moisture on the electronic transport properties of PAni and PPy nanostructures. © 2014 Wiley Periodicals, Inc.
Publication Date: 2010
Iranian Journal of Electrical and Computer Engineering (16820053)9(2)pp. 127-133
In feed forward neural networks, hidden layer neurons' saturation conditions, which are the cause of flat spots on the error surface, is one of the main disadvantages of any conventional gradient descent learning algorithm. In this paper, we propose a novel complementary scheme for the learning based on a suitable combination of anti saturated hidden neurons learning process and accelerating methods like the momentum term and the parallel tangent technique. In our proposed method, a normalized saturation criterion (NSC) of hidden neurons, which is introduced in this paper, is monitored during learning process. When the NSC is higher than a specified threshold, it means that the algorithm moves towards a flat spot as the hidden neurons fall into saturation condition. In this case, in order to suppress the saturation of hidden neurons, a conventional gradient descent learning method can be accompanied by the proposed complementary gradient descent saturation prevention scheme. When the NSC assumes small values, no saturation detected and the network operates in its normal condition. Therefore, application of a saturation prevention scheme is not recommended. We have evaluated the proposed complementary method in accompaniment to the gradient descent plus momentum and parallel tangent, two conventional improvements on learning methods. We have recorded remarkable improvements in convergence success as well as generalization in some well known benchmarks. © 2010.
Publication Date: 2014
International Review of Aerospace Engineering (19737459)7(4)pp. 134-141
In this paper a comprehensive model of a tracker system including derive subsystem is presented. Since the main part of the under consideration system consists a two Degree-Of-Freedom (DOF) gimbal subsystem, at first, the model of a two-axis gimbal is considered. For this purpose, after introducing the coordinate systems and different transformation matrices, the related equations of pitch and yaw axes by considering the friction torques, mass unbalances and cable restraint torques are derived. Moreover, all disturbance terms and the methods for their reduction or elimination are investigated. Then, the derive system of the gimbal including a DC motor with a gear is modeled and governing overall equations of the whole system is obtained. In order to have a model with practical considerations, the model of rate gyro which is used for measuring the angular velocities is also included. Finally, the simulation results of the under consideration case study by using the derived comprehensive dynamical equations of this paper are provided. Analysis of these results are used to synthesis the behavior of the practical system and choosing the suitable control structure in order to achieve stabilization and tracking objectives. © 2014 Praise Worthy Prize S.r.l. All rights reserved.
Publication Date: 2017
Journal of Solar Energy Engineering (15288986)139(5)
This paper proposes a new method based on a Markov model to calculate the reliability of grid-connected photovoltaic (PV) systems. This system is a grid-connected PV system consisting of PV modules, a multiphase DC-DC converter, an inverter, an inverter controller, and an maximum power point tracking (MPPT) controller at University of Isfahan. This system is considered repairable. Also, different levels of operation are considered for the system equipment. Reliability of the PV modules, the multiphase DC-DC converter, and the inverter has been calculated by the Markov model. Finally, the reliability of the entire PV system is calculated by the Markov model. The proposed algorithm is applied to the PV system positioned at University of Isfahan. Simulation results show the applicability of this method for calculating the reliability of grid-connected PV systems. Copyright © 2017 by ASME.
Publication Date: 2015
Journal of Renewable and Sustainable Energy (19417012)7(5)
Due to the growing use of photovoltaic (PV) systems in recent years, the reliability of these systems as one of the most important issues regarding durability and correct performance is important. This paper presents a comprehensive assessment of the reliability of Residential PV System (RPVS) in various conditions based on the Markov model. The systems taken into considerations consist of PV modules, a DC-DC converter, an inverter, an inverter controller, and a maximum power point tracking (MPPT) controller. These systems are considered repairable. To evaluate the effect of the three-phase boost converter and the PV modules on reliability, these systems have been considered towards this specific perspective. Furthermore, the impact of various factors on the reliability of the system components and the entire system is evaluated. Simulation results demonstrate the capacity of the proposed method to assess and comparison of the reliability of different RPVS. Also, the results indicate the impact of various factors such as temperature on it. © 2015 AIP Publishing LLC.
Publication Date: 2016
Renewable and Sustainable Energy Reviews (13640321)63pp. 1-12
Voltage stability assessment is a major issue in monitoring the power system stability. Different voltage stability indices (VSIs) have been proposed in the literature for voltage stability assessment. These indices can be used for distributed generation (DG) placement and sizing, detecting the weak lines and buses and triggering the countermeasures against voltage instability. This paper reviews the VSIs from different aspects such as concepts, assumptions, critical values and equations. The review results provide a comprehensive background to find out the future works in this field and select the best VSI for different applications like DG placement and sizing and voltage stability assessment. © 2016 Elsevier Ltd.
Takarli, R.,
Amini, A.,
Khajueezadeh, M.,
Zarbil, M.S.,
Vahedi, A.,
Kiyoumarsi, A.,
Tarzamni, H.,
Kyyra, J. Publication Date: 2023
IEEE Access (21693536)11pp. 81224-81255
Finding efficient and satisfactory energy storage systems (ESSs) is one of the main concerns in the industry. Flywheel energy storage system (FESS) is one of the most satisfactory energy storage which has lots of advantages such as high efficiency, long lifetime, scalability, high power density, fast dynamic, deep charging, and discharging capability. The above features are necessary for electric vehicles (EVs), railways, renewable energy systems, and microgrids. Also, electrical machines, power electronics converters, and control systems are the cores of energy transfer in FESS. Therefore, they have a critical role in determining efficiency, power rating, power factor, cost, angular velocity, and volume of FESS. So, in this study, the FESS configuration, including the flywheel (rotor), electrical machine, power electronics converter, control system, and bearing are reviewed, individually and comprehensively. Additionally, the mentioned components have been categorized to be a guide for future research. The investigated electrical machines are compared by Finite Element Analysis (FEA). Subsequently, our laboratory's measurement results are reviewed experimentally showing the progress in the field of FESS, such as designing robust control algorithms and an Interior Permanent Magnet-Synchronous Reluctance Machine (IPM-SynRM) to use in FESS.
Publication Date: 2017
Renewable and Sustainable Energy Reviews (1364-0321)67pp. 341-363
Due to different viewpoints, procedures, limitations, and objectives, the scheduling problem of distributed energy resources (DERs) is a very important issue in power systems. This problem can be solved by considering different frameworks. Microgrids and Virtual Power Plants (VPPs) are two famous and suitable concepts by which this problem is solved within their frameworks. Each of these two solutions has its own special significance and may be employed for different purposes. Therefore, it is necessary to assess and review papers and literature in this field. In this paper, the scheduling problem of DERs is studied from various aspects such as modeling techniques, solving methods, reliability, emission, uncertainty, stability, demand response (DR), and multi-objective standpoint in the microgrid and VPP frameworks. This review enables researchers with different points of view to look for possible applications in the area of microgrid and VPP scheduling. © 2016 Elsevier Ltd
Publication Date: 2019
Renewable and Sustainable Energy Reviews (1364-0321)108pp. 355-368
Using different types of renewable energy sources considering their uncertainties causes numerous challenges for minimizing the operation cost and maximizing the reliability of system. Hence, stochastic programming is an essential tool to consider the system uncertainties. This paper presents a day-ahead energy management system to decrease the operation cost and increase the reliability of a Microgrid considering a number of challenges for supporting electrical and thermal loads. In the proposed method, micro-CHP units, renewable energy sources, auxiliary boiler and energy storage system are all responsible for supplying the electrical and thermal loads. The problem is formulated as a multi-objective optimization problem. Moreover, the influence of considering the electrical energy storage system as a non-ideal battery with charge/discharge efficiency less than 1 is investigated. Also, demand response programs are provided based on load shifting contracts to consumers. A scenario-based approach is used to cover the uncertainties of renewable energy sources, market price and electrical load. Besides, this paper considers both islanding and grid-connected modes of Microgrid and investigates the influence of demand side management on operation cost and reliability in both modes. The capability of the proposed algorithm is analyzed by simulation results of a 3-feeder Microgrid. © 2019 Elsevier Ltd
Publication Date: 2017
IEEE Transactions on Power Electronics (0885-8993)32(12)pp. 9117-9130
In this paper, an overall power control strategy is proposed for control of a fixed-pitch small-scale wind energy conversion system operating at both underrated and overrated wind speeds. At underrated wind speeds, the dynamical behavior of the rotor is considered, and the optimal reference torque is generated without the need of wind speed sensors through a robust variable structure observer with the aim of maximum power point tracking. At overrated wind speed, the flux-weakening strategy is invoked to let the machine exploit maximum electrical torque under given current and voltage constraints. As a new approach, the optimal reference flux magnitude together with a reference torque angle is provided by online numerically solving an optimization problem in the whole wind speed range. Moreover, a space-vector-modulation -based direct torque control (SVM-DTC) is used to track the provided references for flux magnitude and torque angle. In particular, the SVM-DTC is composed of a reference voltage vector calculator providing a desired voltage vector. The effectiveness of the proposed overall power control strategy is verified not only by applying the strategy to a commercial 10-kW wind turbine simulated in MATLAB/Simulink, but also by experimental results derived from a developed laboratory setup. © 1986-2012 IEEE.
In this paper, a new control methodology for single-master/multi-slave teleoperation systems is presented. First, the dynamics of slave robots and the tool are incorporated into an augmented system. Then, an adaptive sliding mode controller is proposed to transform both tool and master dynamics into desired impedances in the presence of unmodeled dynamics. Then, the traditional two channel architecture is modified in order to achieve prefect transparency. Finally, simulation results are presented to illustrate the enhanced performance of the proposed control methodology. © 2011 IEEE.
Publication Date: 2014
ISA Transactions (00190578)53(2)pp. 415-422
For the participation of the steam power plants in regulating the network frequency, boilers and turbines should be co-ordinately controlled in addition to the base load productions. Lack of coordinated control over boiler-turbine may lead to instability; oscillation in producing power and boiler parameters; reduction in the reliability of the unit; and inflicting thermodynamic tension on devices. This paper proposes a boiler-turbine coordinated multivariable control system based on improved sliding mode controller (ISMC). The system controls two main boiler-turbine parameters i.e., the turbine revolution and superheated steam pressure of the boiler output. For this purpose, a comprehensive model of the system including complete and exact description of the subsystems is extracted. The parameters of this model are determined according to our case study that is the 320 MW unit of Islam-Abad power plant in Isfahan/Iran. The ISMC method is simulated on the power plant and its performance is compared with the related real PI (proportional-integral) controllers which have been used in this unit. The simulation results show the capability of the proposed controller system in controlling local network frequency and superheated steam pressure in the presence of load variations and disturbances of boiler. © 2013 ISA.
Panah, P.G.,
Hoshmand, R.,
Gholipour, M.,
Macana, C.A.,
Guerrero, J.M.,
Vasquez, J.C. Publication Date: 2021
Sustainable Energy Technologies and Assessments (2213-1388)48
Islanded microgrids with high shares of RES are more exposed to frequency disturbances. The largest generator is typically in charge of frequency regulation. This study tries to upgrade this monopoly to a competitive market. A novel framework is proposed to invite prosumers of any kind/size to participate in a local ancillary service market. A multi-criteria decision-maker is developed to select the proper service from the pool of bids. Flexibility Flags and Prosumer Deviation Index are introduced to quantify the behaviors of individuals and the stability of autonomous microgrids. Furthermore, an innovative reward/punishment framework is suggested for the billing of subscribers. In this method, the extra cost of the activated reserved power is solely compensated by disturbance makers rather than the conventional way of blindly charging all subscribers for frequency regulation. An urban microgrid including electric vehicles, micro combined heat/power generator, thermostatic loads, and kinetic energy storage is considered for the performance assessment. The results indicate that electric vehicles and flexible loads are privileged. Also, the bill of the planned loads for the regulation service falls from 46–48% down to 3–6% under the proposed framework while the cost of frequency regulation drops by 59% when the unnecessary reserved power is modified. © 2021 Elsevier Ltd
Publication Date: 2016
IEEE Communications Letters (10897798)20(10)pp. 2015-2018
A cyclostationary feature-based wideband spectrum sensing is proposed in which cyclic frequency offset is considered. The received signal passes through a rough and flexible filter which its effective band tuned to a specific part of the received signal spectrum. It belongs to a target signal, which possibly exists in the received signal. Some cyclic frequencies of the target are employed to derive the normalized least mean square algorithm that estimates the filter output from its frequency shifted samples. Based on the weight estimate's norm, the algorithm is tuned to find the accurate cyclic frequencies. If it succeeded, it means that the target signal is present. On the other hand, a complete search without major weights estimate means that the target signal is absent. In addition, the overall system, named cyclic frequency lock loop can be reformed as a demodulator for sinusoidal frequency modulation signals. The method is very easy to implement and has less computational complexity comparing with its other spectrum sensing counterparts. Simulation results validate the efficiency of the proposed method. © 2016 IEEE.
Publication Date: 2017
Sensor Review (02602288)37(4)pp. 468-477
Purpose - The purpose of this study is to propose a pulse width based, in-pixel, arbitrary size kernel convolution processor. When image sensors are used in machine vision tasks, large amount of data need to be transferred to the output and fed to a processor. Basic and low-level image processing functions such as kernel convolution is used extensively in the early stages of most machine vision tasks. These low-level functions are usually computationally extensive and if the computation is performed inside every pixel, the burden on the external processor will be greatly reduced. Design/methodology/approach - In the proposed architecture, digital pulse width processing is used to perform kernel convolution on the image sensor data. With this approach, while the photocurrent fluctuations are expressed with changes in the pulse width of an output signal, the small processor incorporated in each pixel receives the output signal of the corresponding pixel and its neighbors and produces a binary coded output result for that specific pixel. The process is commenced in parallel among all pixels of the image sensor. Findings - It is shown that using the proposed architecture, not only kernel convolution can be performed in the digital domain inside smart image sensors but also arbitrary kernel coefficients are obtainable simply by adjusting the sampling frequency at different phases of the processing. Originality/value - Although in-pixel digital kernel convolution has been previously reported however with the presented approach no in-pixel analog to binary coded digital converter is required. Furthermore, arbitrary kernel coefficients and scaling can be deployed in the processing. The given architecture is a suitable choice for smart image sensors which are to be used in high-speed machine vision tasks. © Emerald Publishing Limited.
Habibi, M.,
Habibi M.,
Bafandeh A.,
Montazerolghaem M.A. Publication Date: 2014
Integration (1679260)47(4)pp. 417-430
The high speed and in-pixel processing of image data in smart vision sensors is an important solution for real time machine vision tasks. Diverse architectures have been presented for array based kernel convolution processing, many of which use analog processing elements to save space. In this paper a digital array based bit serial architecture is presented to perform certain image filtering tasks in the digital domain and hence gain higher accuracies than the analog methods. The presented method benefits from more diverse convolution options such as arbitrary size kernel windows, compared with the digital pulse based approaches. The proposed digital cell structure is compact enough to fit inside an image sensor pixel. When incorporated in a vision chip, resolutions of up to 12 bit accuracy can be obtained in kernel convolution functions with 35×28 μm2 layout area usage per pixel in a 90 nm technology. Still, higher accuracies can be obtained with larger pixels. The power consumption of the approach is approximately 10 nW/pixel at a frame rate of 1 kfps. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Publication Date: 2026
Journal of the Franklin Institute (00160032)363(2)
This paper explores the challenges of synchronizing Euler-Lagrange networks that include a dynamic leader, utilizing a disturbance observer method. In this network, each agent is characterized by Euler-Lagrange equations of motion with dynamics that are not fully known. Unlike most existing approaches for handling uncertainties in Euler-Lagrange networks, the structure of the dynamic equations is assumed to be unavailable, making existing adaptive control schemes inapplicable. Therefore, a new formulation is proposed for Euler-Lagrange networks to lump the uncertain dynamical terms, estimate them, and suppress their effects accordingly. The closed-loop stability of the overall system is analyzed using the Lyapunov stability theorem. Simulation results show that the proposed approach outperforms two existing benchmark control methods. © 2025 The Franklin Institute. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Publication Date: 2016
Sensor Review (02602288)36(4)pp. 368-376
Purpose - The purpose of this paper is to present a DNA hybridization detection sensor. An inexpensive fabrication procedure was used so that the sensors can be disposed economically after the measurement is completed. Design/methodology/approach - Field effect transistor (FET) devices are used in the proposed structure. The FET device acts as a charge detection element and produces an amplified output current based on surface charge variations. As amplification is performed directly at the sensor frontend, noise sources have less effect on the detected signal, and thus, acceptably low DNA concentrations can be detected with simple external electronics. ZnO nano layers are used as the FET active semiconductor channel. Furthermore, a photobiasing approach is used to adjust the operating point of the proposed FET without the need for an additional gate terminal.Findings - The proposed sensor is evaluated by applying matched and unmatched target DNA fragments on the fabricated sensors with capture probes assembled either directly on the ZnO surface or on a nano-platinum linker layer. It is observed that the presented approach can successfully detect DNA hybridization at the nano mole range with no need for complex laboratory measurement devices. Originality/value - The presented photobiasing approach is effective in the adjustment of the sensor sensitivity and decreases the fabrication complexity of the achieved sensor compared with previous works. © Emerald Group Publishing Limited.
Publication Date: 2015
Microelectronic Engineering (01679317)131pp. 29-35
In this paper, an oligonucleotide hybridization detection sensor is presented. The sensor uses field effect transistor (FET) devices to sense the surface charge, amplify it and produce a detectable output signal. With the FET device, hybridization can be detected at lower volumes and concentrations. The FET device is based on solution processed ZnO nano layers as the semiconductor channel. Since the design uses a low cost fabrication procedure, the sensors can be disposed economically after successful completion of the measurements. Furthermore the presented ZnO FET device benefits from double gate advantages. The bottom gate is used to provide the required initial bias conduction channel while the top gate is used to modulate the threshold voltage using the surface charge variations. The effect of platinum nano particles on thiolated DNA probe assembly at the sensor surface is also investigated in this paper. The presented concept is evaluated using a probe station instrument. The input-output transfer curve of the FET is extracted for different surface configurations including DNA probe, DNA probe hybridized with a match (complementary) target and DNA probe coated with un-match DNA sequence. It is shown that the hybridization can be identified with threshold voltage shifts of the transfer curve. It is also observed that the nano platinum linkers increase the sensor's sensitivity. © 2014 Elsevier B.V. All rights reserved.
Publication Date: 2023
IET Control Theory and Applications (17518644)17(12)pp. 1637-1647
In collaborative haptic training systems, a novice operator is interfaced with an expert operator and cooperatively performs some task on a real/virtual environment. Most control architectures for collaborative haptic training systems do not consider the switching task dominance together with investigating overall stability in the presence of nonlinear dynamics and uncertainty. In this paper, a theoretical framework is presented for switching task dominance in collaborative haptic training systems based on supervision and intervention of the expert operator. To that effect, the novice operator performs the operation with as little as possible interference haptic signals in the normal operational conditions. On the other hand, the expert operator is able to intervene the operation to guide the novice operator when it is necessary. The most challenging part of controller design for such systems is to provide the mentioned supervisory framework in a way that the stability of interaction between the operators and the system is ensured with acceptable task performance in various operational conditions. This work offers a variable-gain dual robust control scheme to address the above problem. The key idea is that the tracking gain of each controller is adjusted in real-time to switch the task authorities. It is verified that the input-to-state stability property is satisfied for each subsystem. Then, the overall stability is proved by leveraging the small gain theorem. Finally, the functionality and performance of the suggested control architecture is demonstrated through simulation and experimental studies. © 2023 The Authors. IET Control Theory & Applications published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
The widespread use of minimally invasive surgery (MIS) demands an appropriate framework to train novice surgeons (trainees) to perform MIS. One of the effective ways to establish a cooperative training system is to use virtual fixtures. In this paper, a guiding virtual fixture is proposed to correct the movements of the trainee according to trainer hand motion performing a real MIS surgery. The proposed training framework utilizes the position signals of trainer to modify incorrect movements of the trainee which leads to shaping the trainee's muscle memory. Thus, after enough training sessions the trainee gains sufficient experience to perform the surgical task without any further help from the trainer. The passivity approach is utilized to analyze the stability of system. Simulation results are also presented to demonstrate the effectiveness of the proposed method. © 2018 IEEE.
