S.A. Akbar

A CCII-based wide frequency range square/triangular wave generator

In this paper, we propose a current-mode based solution suitable for triangular/square wave generator using second generation current conveyor. The proposed oscillator, which utilizes two second generation current conveyor (CCII) as active elements, three resistors and a capacitor, is based on resistance-capacitance (RC) cell and found to be effective alternate of voltage-mode based oscillators. Experimental results were obtained by implementing the proposed circuit using commercially available CCII (AD844) and passive components. Simulation and experimental results have confirmed the theoretical expectations, showing good linearity in wide oscillation frequency range. The sensitivity and operating frequency of the proposed oscillator can be adjusted using passive components. The proposed configuration finds useful applications in wide range capacitive/resistive sensor front end.

A robust H-infinity based depth control of an autonomous underwater vehicle

This paper presents a robust H-infinity based control methodology for an Autonomous Underwater Vehicle(AUV). The kinematics and dynamics of an AUV is described using six degree of freedom differential equations of motion using body and earth-fixed frame of references. Due to hydrodynamic forces, these equations are highly coupled and non-linear. From the practical point of view it is essential to consider a reduced order model for efficient controller design. Hence the system is commonly subdivided into smaller subsystems, like depth, steering (or yawing) and speed subsystems, which are considered to be mutually non-interactive from the controller design perspective. In this study a reduced order model was derived using the depth plane dynamics of the vehicle. The working environment of an AUV is vastly uncertain due to varying environmental conditions, thereby demanding a robust controller which has the ability to adapt to these uncertainties and provide stabilizing effect irrespective of the change in the surrounding conditions. The proposed H-infinity controller takes into account the uncertainties in the hydrodynamic parameters which arise due to changing operating conditions and provides suitable control action for desired set point tracking as well as disturbance rejection. The altitude of the vehicle is strongly dependent on the pitch angle, and the controller presented here takes care of both the pitch and depth plane dynamics. The mixed sensitivity approach for H-infinity controller design is followed, and the efficacy of the controller is compared with Linear Quadratic Gaussian(LQG) controller and the Mixed H2/H-infinity controller. The controller design and simulation has been done in Matlab, and the simulated results provide satisfactory results, for disturbance rejection and set point tracking for the H-infinity controller in presence of hydrodynamic parametric uncertainties.

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

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.

Development of virtual humidity sensor system

This paper presents the development of an active bridge based virtual humidity sensor system, where the capacitive humidity sensor and a reference capacitor forms two arms of the bridge. The bridge is excited by an AC voltage source of 1 kHz with amplitude of 200mV (rms). The amplitude of the input and output voltages and their phase difference are measured by National Instruments (NI) LabVIEW virtual instruments (VI) blocks through NI data acquisition (DAQ) card. The governing equations for evaluating the capacitance and resistance of the sensor are implemented by Virtual Instruments blocks to directly display the measured values. The sensor capacitance is also measured with Agilent Impedance Analyzer and accuracy of measurement for pure capacitance is found to be 1 %.

Small and medium range wireless electronic notice board using Bluetooth and ZigBee

When information exchange occurs between people via a network, then authentication and security of data have more priority. This paper introduces a low cost, handheld, wireless electronic notice board by using Atmels ATmega32 microcontroller and different wireless technologies (Bluetooth and ZigBee) and their performance analysis based on the parameter such as range, BER (bit error rate), RSSI (Received signal strength indicator), signal attenuation and power consumption. The notice board receives serial data from wireless module receiver and displays it on the graphical liquid crystal display. We have realized a common communication receiver hardware for notice board having compatibility with both wireless modules i.e. Bluetooth and ZigBee. We used KS0108 based 128×64 graphical LCD as display element.

Development of embedded system for carbon nano tube (CNT) based Ammonia (NH3) gas sensor

This paper presents a simple, precise, and versatile embedded system for gas concentration measurement of a sensor chip using in-house developed carbon nanotube (CNT) based gas sensor and characterization of packaged device in an ambient. The characterization equation having relation between change in resistance and ppm is obtained by gas sensing measurements and implemented in the embedded system based on MSP430 microcontroller. There is an implementation of a bridge circuit method with instrumentation amplifier to determine the resistance of CNT gas sensor. The proposed signal conditioning circuit is implemented for the prefabricated SWCNT based NH3 gas sensor and the analysis of NH3 response at different concentrations and with experimental results is reported in this work.

A simple analog interface for capacitive sensor with offset and parasitic capacitance

In this paper, a simple but efficient analog interface circuit for floating capacitive sensor is presented. In most of the capacitive sensor, the offset and parasitic components are associated with the sensor and varies with the measurand. In these sensors, the change in the sensor capacitance due to measurand can be very small but having a relatively large offset capacitance in parallel and also the value of parasitic capacitances are not constant and varies with measurand. Hence, the error due to offset and parasitic components will propagate in the output which will degrade the performance of the sensor system. The proposed analog front end circuit accepts these types of sensors and provide an output voltage proportional to capacitance change due to measurand. A prototype board has been developed and tested for different values of the parasitic and offset capacitance by varying the variable sensor capacitance. The circuit validate the theoretical expectation and without any visible effect on output voltage on offset and parasitic capacitance. The worst case error for all taken cases are found to be within 1%. In order to test the validity of proposed interface circuit in real time application, a capacitive humidity sensor is fabricated and tested with the proposed circuitry. The interface circuit found to be working well with humidity sensor in the range of 30 to 90% RH.

Development of self-stabilizing 3-DOF -RRR camera system using fuzzy logic

Gimbal system for surveillance applications are often needed moving camera system. Surveillance camera units mounted on moving vehicles create apparent movement in image plane, which causes difficulties in pointing and tracking of a specific featured object. This paper describes the development and control of the robotic system having 3-revolutionary joints, (RRR/3-R) robotic manipulator platform using orthogonal servo motors, and image based object tracking and camera stabilizing scheme controlled with fuzzy logic to neutralize the movement of object. Stabilizing platform moves in pan-tilt way using orthogonal servos to keep the movable object image in center of image frame. For back tracking of the yaw and pitch angles a MEMS based IMU unit is mounted on camera to analyze the object tracking by monitoring the servo motor angles, that indicates the validity and precision of applied control logic. To compensate the yaw and pitch of the system, two independent fuzzy logic control loop are designed to control the position of pan and tilt servo motor.