Field Assisted Quantum Tunneling Enabled Pressure-sensitive Composites And Their Intelligent Traffic Detection System

Intelligent transportation system (ITS) is an effective way to solve the increasingly serious traffic problems. Field assisted quantum tunneling enabled silicon rubber-based composite is a kind of unique pressure-sensitive conductive composite with the advantages of large resistance change range under the external force, easy preparation and excellent mechanical properties. It is therefore expected to be developed as a multiple traffic parameter monitoring sensor for intelligent traffic system.With attentions to preparation, pressure-sensitivity, mechanism and application of the field assisted quantum tunneling enabled silicon rubber-based composites, the pressure-sensitive behaviors of the composites under different types of loads are systematically studied in this thesis. Based on the research results, the mechanism of pressure-sensitivity of the composites is investigated and a mathematical model describing pressure-sensitivity is accordingly developed. The feasibility of the composites for intelligent traffic detection system application is also verified. The main research contents and results are as follows:(1) Under different curing conditions, the field assisted quantum tunneling enabled silicon rubber-based composites were fabricated using different kinds of nickel particles, different dosages of nickel particles and different silicon rubber types. The conductive characteristics and microstructures of the composites are analyzed. The results show that the composites act as an insulator without loading, which is because the nickel particles are well separated by the silicon rubber without causing the formation of percolation conducting network in the composites. Magnetic field treatment can promote the generation of chain conductive structures effectively, thus causing a significant increase in the conductivity of the composites.(2) The influence rules of silicon rubber matrix, kind and dosage of nickel particles as well as magnetic field treatment on the pressure-sensitivity of field assisted quantum tunneling enabled silicon rubber-based composites are investigated. The reproducibility of the pressure-sensitivity of the composites under cyclic load is explored. Based on Cotton's equation and Burger's model, the descriptions of stress relaxation behavior and electrical resistance relaxation behavior of the composites under static load are given respectively. The results show that the composites with remarkable response to external force can be used to develop traffic detection sensors. The increase of the dosage of nickel particles can improve the stability and reproducibility of the pressure-sensitivity of the composites. Electrical resistance relaxation behavior of the composites is partly controlled by the stress relaxation behavior.(3) Based on the theory of percolation conduction, the mechanisms of the pressure-sensitivity of field assisted quantum tunneling enabled silicon rubber-based composites under uniaxial load are discussed and further qualitatively explained by adopting effective conducting path model. On the basis of this model combined with quantum tunneling effect and field emission effect, a mathematical model describing the pressure-sensitivity of the composites is established. The results show that the dominant mechanisms of the remarkable pressure-sensitivity of the composites under uniaxial load are the quantum tunneling effect and the field emission effect. The proposed mathematical model can be well described the pressure-sensitivity of the composites.(4) Integrated with field assisted quantum tunneling enabled silicon rubber-based composites, an intelligent traffic detection system is designed and implemented. The performances of traffic detection for the developed systems with different sensitivities and different layout forms are tested in an experimental road for different types of test vehicles and for different vehicle speeds. The performances of the developed systems are also investigated in a real road. Test results show that the developed systems have the advantages of high sensitivity, fast response and recovery, low energy consumption, high detection precision and the capacity to actualize the detection of multiple traffic parameters including vehicle presence, vehicle speed, vehicle count, vehicle occupancy, vehicle weight and vehicle classification. In addition, with the merits of small size as well as simple configuration, they are easy to install and maintain.