Boby George

A Multiple Inductive Loop Vehicle Detection System for Heterogeneous and Lane-Less Traffic

This paper presents a novel inductive loop sensor that can detect vehicles under a heterogeneous and less-lane-disciplined traffic and thus can be used to support a traffic control management system in optimizing the best use of existing roads. The loop sensor proposed in this paper detects large (e.g., bus) as well as small (e.g., bicycle) vehicles occupying any available space in the roadway, which is the main requirement for sensing heterogeneous and lane-less traffic. To accomplish the sensing of large as well as small vehicles, a multiple loop system with a new inductive loop sensor structure is proposed. The proposed sensor structure not only senses and segregates the vehicle type as bicycle, motor cycle, scooter, car, and bus but also enables accurate counting of the number of vehicles even in a mixed traffic flow condition. A prototype of the multiple loop sensing system has been developed and tested. Field tests indicate that the prototype successfully detected all types of vehicles and counted, correctly, the number of each type of vehicles. Thus, the suitability of the proposed sensor system for any type of traffic has been established.

Virtual Instrument for the Measurement of Haemo-dynamic Parameters Using Photoplethysmograph

This paper presents the design and development of a virtual instrument for the measurement of haemodynamic parameters namely, pulse rate and oxygen saturation in arterial blood based on the popular photoplethysmographic (PPG) principle. A clip-on sensor, housing red and infrared (IR) light emitting diodes and suitable photo detectors is developed. The sensor is interfaced to a PC utilizing the audio channel of the sound card, thus dispensing with expensive analog to digital converter hardware. Since the frequency response of the audio channel is not suitable for the PPG waveforms of red and IR, FM modulation and demodulation are employed. An empirical relationship is developed for the computation of the oxygen saturation in arterial blood using the red and IR PPG data and the well-known and well-established extinction coefficients of haemoglobin with and without oxygen. Data acquisition and processing are accomplished under LabVIEW virtual environment

Switched Capacitor Signal Conditioning for Differential Capacitive Sensors

A novel switched capacitor signal-conditioning circuit for differential capacitive sensors is proposed. The main advantage of the proffered method lies in the fact that it accepts sensors possessing either linear or inverse characteristics and provides a linear output. Moreover, the output is dependent only on a pair of dc reference voltages and the transformation constant of the sensor. Hence, increased linearity and accuracy is easily achieved by employing precision dc reference voltages. Results from the tests on a prototype elucidate the practicality of the proposed method

Electronic Scheme for Computing Inverse-Cosine and its Application to a GMR Based Angle Sensor

This paper presents a new, simple but effective, electronic method to obtain inverse-cosine of an electrical variable. The proposed method is very useful for linearization of sensors whose output is a cosine or sine function of the physical quantity being sensed. The inverse-cosine of the variable is obtained by comparing it with a reference sinusoidal wave. The proposed method is easy to implement using electronic components. Using the new technique, a giant magneto-resistance-based angle sensor that provides an output linearly proportional to the angle being sensed has been developed, and the details are reported in this paper. A prototype of the angle sensor has been built, and the practicality of the new method has been tested successfully. The developed sensor provides a linear output for a range of 0° to 180°. The worst case error was found to be less than 0.35° for a range of 10°-170°.

An Efficient Multiple-Loop Sensor Configuration Applicable for Undisciplined Traffic

This paper presents an effective multiple-inductive-loop pattern suitable for heterogeneous and less lane-disciplined traffic and its performance evaluation. Vehicle detection system based on conventional inductive loops works well only for lane-based and homogeneous traffic. A multiple-loop system for sensing vehicles in a heterogeneous and less lane-disciplined condition has been reported recently. The scheme proposed in this paper employs a new configuration, where all the loops are connected in series, which considerably reduces the system complexity and improves reliability. Each loop has a unique resonance frequency and the excitation source given to the loops is programmed to have frequency components covering all the loop resonance frequencies. When a vehicle goes over a loop, the corresponding inductance and resonance frequency will change. The shift in frequency or its effect in any/every loop can be simultaneously monitored, and the vehicles can be detected and identified as a bicycle, a motorcycle, a car, a bus, etc., based on the signature. Another advantage of this scheme is that the loops are in parallel resonance; hence, the power drawn from the source will be minimal. A prototype multiple-loop system has been built and tested based on the proposed scheme. The developed system detected, classified, and counted vehicles accurately. Moreover, the system also computes and provides the speed of the vehicle detected using a single set of multiple loops. The accuracy of the speed measurement has been compared with actual values and found to be accurate and can be used for real-time intelligent transportation system (ITS) applications under heterogeneous and less lane-disciplined (e.g., Indian) conditions.

A multiple loop vehicle detection system for heterogeneous and lane-less traffic

This paper presents a novel inductive loop sensor which detects large (e.g., bus) as well as small (e.g., bicycle) vehicles and help a traffic control management system in optimizing the best use of existing roads. To accomplish the sensing of large as well as a small vehicle, a multiple loop inductive sensor system is proposed. The proposed sensor structure not only senses and segregates the vehicle type as bicycle or motor cycle or car or bus but also enables accurate counting of the number of vehicles that too in a mixed traffic flow condition. A prototype of the multiple loop sensing system has been developed using a virtual instrumentation scheme and tested. Field tests indicate that the prototype successfully detected all types of vehicles and counted, correctly, the number of each type of vehicles. Thus the suitability of the proposed multi loop sensor system for any type of traffic has been established.

Dual Slope Resistance to Digital Converter

A dual slope resistance to digital converter applicable to differential resistive sensors is presented. A dual slope digital converter is appropriately modified so that it accepts directly the resistive elements of a differential resistive sensor and provide a digital output that is linearly proportional to the physical quantity being sensed by the sensor. High accuracy is easily obtained since the output is decided only by a pair of dc reference voltages and the transformation constant of the sensor. Sensitivity analysis shows that the effect of circuit parameter variations on the output is minimal. The efficacy of the proposed scheme is clearly demonstrated by the test results obtained on a prototype.

A magnetically coupled inductive loop sensing system for less-lane disciplined traffic

A new multiple inductive loop detector system that uses the mutual inductances between an outer loop and multiple inner loops is presented in this paper. Automated detection, classification and speed measurement of vehicles are a challenging task in a no-lane and heterogeneous traffic. A recently reported multiple loop scheme is a solution but it is complex and less reliable due to large number of electrical connections required to realize the system. This paper proposes a loop sensor wherein small inner loops are placed within a large outer loop. In the new system the outer loop alone is connected to the measurement unit and all the inner loops are simply coupled inductively to the outer loop. This scheme is simple and can be easily employed to convert an existing single loop system to a multiple loop system by incorporating the inner loops. A suitable measurement scheme based on a synchronous detection is employed that guarantees accurate measurement. A special excitation that ensures parallel resonance of the whole inductive system is employed to keep the power consumption minimum. A prototype of the proposed system has been built and the practicality has been tested. The new system correctly sensed the vehicles, categorized and counted them in an undisciplined traffic.

Design and Analysis of a Dual-Slope Inductance-to-Digital Converter for Differential Reluctance Sensors

A new, simple, and high accuracy dual slope inductance-to-digital converter (DSIDC) suitable for differential reluctance sensors is presented in this paper. Differential reluctance sensors have two inductors that vary in a push-pull manner with respect to measurand. In many such sensors, the relationship between inductance and measurand is nonlinear. It is known that a small linear range can be obtained by taking the difference between the values of the sensor inductances. The proposed DSIDC accepts the sensor inductances having nonlinear characteristics and provides a linear digital output directly proportional to the measurand [without employing a dedicated analog-to-digital converter (ADC)]. The output of the DSIDC is linear for the full range of the sensor. As the output is in digital form, it can be easily stored and processed in a digital system. The DSIDC is based on dual-slope ADC principle and possesses many advantages. The effect of various parameters on the performance of the DSIDC was analyzed, quantified, and presented in this paper. A prototype DSIDC has been built and tested with a differential variable reluctance based displacement transducer. Output from the DSIDC was linear for the full range of input.

Motion Artifact Reduction and Data Compression of Photoplethysmo-graphic Signals utilizing Cycle by Cycle Fourier Series Analysis

Artifact-free clean photoplethysmographic (PPG) signals obtained at red and infrared (IR) wavelengths are required for the estimation of the level of oxygen saturation (SpO2) in arterial blood of a patient. Movement of a patient corrupts a PPG signal with motion artifacts and introduces large errors in the computation of SpO2- A novel method to remove motion artifacts from corrupted PPG signals by applying Fourier series analysis on a cycle by cycle basis is presented in this paper. Over and above artifact reduction, the proposed method also provides data compression. Experimental results indicate that the proposed method is insensitive to heart rate variation, introduces negligible error in the processed PPG signals due to the additional processing, preserves all the morphological features of the PPG, provides 35 dB reduction in motion artifact and achieves a data compression factor of 12.