S. A. Akbar

Bio: S. A. Akbar is an academic researcher from Academy of Scientific and Innovative Research. The author has contributed to research in topics: Capacitive sensing & Computer science. The author has an hindex of 9, co-authored 39 publications receiving 200 citations. Previous affiliations of S. A. Akbar include Central Electronics Engineering Research Institute & Council of Scientific and Industrial Research.

A time domain bridge-based impedance measurement technique for wide-range lossy capacitive sensors

Abstract: In this paper, a new, simple and accurate impedance measurement technique (IMT) for wide range lossy capacitive sensor is proposed. The proposed technique accepts sensors having capacitance ‘Cx’ with lossy resistance ‘Rx’ in parallel. The proposed IMT is based on the separation of in-phase and quadrature components, which is achieved by using phase to time converter. For comparative study, two circuit configurations are proposed. In first proposed solution, the sensor parameters are measured by separating the real and imaginary part of the output electrical signal. In the second proposed configuration, the measurement range is enhanced using an auto-balancing approach, which is achieved by monitoring phase difference between input and output voltages. Experimental evaluation of the proposed configurations reveals that the first configuration is able to estimate the sensor capacitance in the range 200–1200 pF and lossy resistance in the range of 100 kΩ–1.2 MΩ with a maximum error of 6%. The second configuration exhibits an enhanced range of 100–2000 pF for sensor capacitance and 33 kΩ–3 MΩ for lossy resistance with a maximum error of 5%. The IMT was interfaced with a fabricated γ-Al2O3 based impedance humidity sensor, measured its Cx (70 pF–800 pF) and Rx (35 kΩ–4 MΩ) at different concentration of humidity, calculated the humidity, and compared its performance with existing techniques, showing the practicality of the proposed IMT.

Evolution of Lock-In Amplifier as Portable Sensor Interface Platform: A Review

Abstract: The phase-sensitive detection (PSD), popularly referred to as lock-in amplifier (LIA) has been around for quite a long time. Lock-in amplifier has been quite a versatile measurement instrument for extracting low-level signals buried in noise. In the recent past, the importance of LIA has been realized as a sensor interfacing platform and a number of portable implementations targeting sensing applications have been reported. This review surveys LIA design, implementation and application as portable sensor interfaces. The paper put forward a brief history of phase-sensitive detection leading up to the state-of-the-art implementation in various fields of application. Different designs and implementation techniques for LIA have been categorized and introduced as per the design topologies. The main category being analog, digital, FPGA and CMOS integrated design. Finally, the application of LIA in resistive, capacitive, impedance, optical and Nano-bio sensors is categorized and investigated in detail.

Fuzzy logic based depth control of an autonomous underwater vehicle

Abstract: This paper presents an adaptive fuzzy logic based controller for the depth control of an Autonomous Underwater Vehicle(AUV). The kinematic and dynamic motion of an AUV is described using six degree of freedom differential equations of motion using bodyand earth-fixed frame of references. Due to hydrodynamic forces, these equations are complex, non-linear and highly coupled therefore are impractical for use in controller design. In practice, system is commonly decomposed into three non-interactive systems such as diving subsystem, steering subsystem and speed subsystem. In this study a reduced order model was derived for diving system using depth plane dynamics and a suitable dual loop control strategy is formulated by synthesizing fuzzy logic based control in series with a phase lead dynamic compensator to achieve the desired set point tracking and reasonably good performance objectives under variety of disturbances encountered in oceanic environments. The obvious benefits of this type of approach lies in the simplicity of the scheme compared to the conventional deterministic systems and easy implementation for real time control of the Autonomous Underwater Vehicles. The proposed fuzzy logic based controller accepts deterministic information, the depth of the vehicle as input and achieves imprecise reasoning and de-fuzzification to generate a deterministic control output which manipulates the pitch angle and hence the depth of the vehicle. The simulated results clearly demonstrate the efficacy of this approach as compared to the conventional PID controller designed and tuned using Ziegler-Nichols scheme.

Design and development of digital PID controller for DC motor drive system using embedded platform for mobile robot

Abstract: In Agriculture industry, plants are prone to diseases caused by pathogens and environment conditions and it is a prime cause to lose of revenue. It requires continuous monitoring of plants and environment parameters to overcome this problem.

A CCII-based relaxation oscillator as a versatile interface for resistive and capacitive sensors

Abstract: In this paper, a novel Current-Mode (CM) square/triangular wave oscillator, based on second generation current conveyor (CCII), operating as resistance/capacitance to time conversion is described. The proposed oscillator, which consists of two CCII as an active element, three grounded resistances and one capacitance found to be an effective alternate of voltage mode based interfaces for wide range capacitive and resistive sensors. The interface circuit was implemented with commercially available current feedback operational amplifier AD844 from Analog Devices and passive components. Experimental results confirmed the theoretical expectations, showing good linearity in wide oscillation frequency/period range, which can be independently adjusted through resistive or capacitive external passive components. Experimental measurement was also conducted on a fabricated capacitive humidity sensor to verify the real time application of the proposed interface circuit. The interface circuit has shown a good accuracy and linearity for wide variation in capacitance of humidity sensor.

Bayesian Block Structure Sparse Based T–S Fuzzy Modeling for Dynamic Prediction of Hot Metal Silicon Content in the Blast Furnace

Abstract: Since the hot metal silicon content simultaneously reflects the product quality and the thermal state of the blast furnace, its modeling is crucial and representative. In order to facilitate the realization of control, this paper proposes a Bayesian block structure sparse based Takagi–Sugeno (T–S) fuzzy modeling method, with which the main important fuzzy rules and the corresponding pivotal consequent parameters can be selected automatically to obtain a compact fuzzy model with good generalization performance. For being conjugate to the Gaussian likelihood that would lead to the associated Bayesian inference to be performed in closed form, a hierarchy of block structure sparse priori is adopted, and the variational Bayesian inference is used to solve it. The screening of model inputs and data processing appropriately consider the characteristics of the blast furnace process. The applicability and performance of the proposed method are demonstrated on no. 2 blast furnace of Liuzhou Steel in China.

Uncertainty and disturbance estimator based sliding mode control of an autonomous underwater vehicle

Abstract: In this paper, a highly non-linear model of an autonomous underwater vehicle (AUV) with six degrees-of-freedom is linearized to yaw (horizontal) and pitch (vertical) planes under several working conditions. For controlling steering and diving planes, an uncertainty disturbance estimator based sliding mode control (UDE-SMC) scheme is proposed and designed separately as single-input single-output controllers for horizontal and vertical plane dynamics of an AUV system. The proposed UDE-SMC scheme is effective in compensating the uncertainties in the hydrodynamic parameters of the vehicle and rejecting unpredictable disturbances due to ocean currents. The UDE-SMC consists of an equivalent and estimated lumped uncertain terms to suppress the effect of external disturbances and parametric uncertainties acting on the vehicle dynamics. Numerical simulations were performed to validate the UDE-SMC.

Autobalancing Analog Front End for Full-Range Differential Capacitive Sensing

Abstract: The authors here propose an analog interface for differential capacitance estimation, able to reveal and quantify capacitive variations. Different from other works in the literature, the proposed interface can operate on a full-range scale. This solution takes inspiration from a preliminary work of the same authors, whose working principle is based on a modified De-Sauty AC bridge configuration; in particular, two (differential) capacitors and two resistors are employed, one of which is implemented by a voltage-controlled resistor (VCR). In this paper, the electronic interface has been redesigned to obtain full-range operation and a linear input–output characteristic. The implemented autobalancing mechanism controls the VCR generating a reference voltage following the sensor output. Simulation results in two different circuit configurations performed by OrCAD PSpice have shown a very good agreement with a theoretical model implemented in MATLAB/Simulink environment. In addition, an evaluation of the goodness of the experimental measurements at steady and unsteady conditions is given. Experimental tests on a discrete-component prototype have been carried out using an automated test equipment including National Instruments tools and a dedicated software in the LabVIEW environment. Measurements have shown satisfactory results, the standard deviation being on the order of 0.01, in the worst case. The linearity error has been evaluated as well, resulting in lower than 1% full scale.

QoS Enabled IoT Based Low Cost Air Quality Monitoring System with Power Consumption Optimization

Abstract: Abstract Air pollution has emerged as a major concern of the current century. In recent times, fellow researchers have conducted numerous researches in the area of air quality monitoring. Still, air quality monitoring remains an open research area due to various challenges such as sophisticated topology design, privacy and security, power backup, large memory requirements and deployment of such systems at resource-constrained sites. The proposed research work is an attempt to address the issues of communication topology design, assessment of the Quality of Service (QoS) levels against accuracy, sensing throughput and power consumption optimization. In the undertaken work, the proposed IoT based Air Quality Monitoring system has been deployed at indoor and outdoor sites to measure air quality parameters such as PM10, PM2.5, carbon monoxide, temperature and humidity. The proposed system is also tested at variety of quality of service levels at the indoor and outdoor sites. The conducted experiments have also recorded accuracy in terms of reliable delivery of the messages under employed protocol.