Double Magnetic Loop and Methods for Calculating Its Inductance

Abstract

Due to their simplicity and operating mode, magnetic loops are one of the most used traffic sensors in Intelligent Transportation Systems (ITS). However, at this moment, their potential is not being fully exploited, as neither the speed nor the length of the vehicles can be surely ascertained with the use of a single magnetic loop. In this way, the vast majority of them are only being used to count vehicles on urban and interurban roads. For this reason, in order to contribute to the development of new traffic sensors and make roads safer, this paper introduces a theoretical study to explain the design and peculiarities of the innovative double loops, how to calculate their magnetic field and three different methods to calculate their inductance. Finally, the different inductance values obtained by these three methods will be analyzed and compared with experimental measurements carried out by our research group in order to know which method is more accurate and if all of them are equally reliable.

Vehicle Identification by Means of Radio-Frequency-Identification Cards and Magnetic Loops

“…This waveform depends mainly on parameters related to the vehicle such as length, engine position or number of axles. This is the reason why these waveforms are different for each type of vehicle, which allows through simple signal processing to obtain the speed and length and classify vehicles as bicycles, motorcycles, cars, trucks and buses [17]- [19], as seen in Fig. 3.…”

Advantages offered by the double magnetic loops versus the conventional single ones

“…Nevertheless, the double loop is still unknown. For this reason we presented in a previous paper a theoretical study to explain the design and peculiarities of the innovative double loops, how to calculate their magnetic field and three different methods to calculate their inductance [29]. In order to have a better understanding of the magnetic profiles generated by these new loops, the space was divided into three sections.…”

“…The operation of these sensors is straightforward, since it is based on the impedance variation that is recorded in the magnetic loops during the passage of vehicles over them [29]. These are buried in the pavement and are placed in such a way that they form an oscillating circuit together with the electronic unit located in the control booth.…”

“…Like any resonant circuit [30], the oscillation frequency of the whole system is given by where k is a constant that depends on the characteristics of the electronic components used in the construction of the oscillator circuit [30] and L is the loop inductance expressed in Henrys [29]. Thus, when a vehicle passes over a loop, it is obtained its magnetic profile by analyzing the inductance or frequency variation recorded.…”

“…With the implementation and use of the double loops in urban and interurban roads, this problem would be solved and it would only be necessary to use a double loop in order to calculate all the previous data, since they have a simpler, more compact and more economical electronics [29]. In this way, it would be possible to develop a more reliable and lower cost traffic sensor than its predecessor and with many more features by using the same technology and operating mode already widely known.…”