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technologies for TPMS was presented by Roundy [ 1 ] and Kubba et al. [ 2 ] recently provided an excellent and detailed overview of TPMS systems. TPMS are becoming increasingly mandatory in the automotive market as more stringent environmental regulatory frameworks [ 3 ] are being established to lower fuel consumption and CO 2 emissions. Maintaining a correct tire pressure also contributes signifi cantly to passenger safety as it directly affects the vehicle's handling and control. Underinfl ated tires can cause high heat generation, which leads to rapid tire wear, tread separation, blow-out, and loss of vehicle control. Vehicles with underinfl ated tires also suffer from reduced lateral stability and require longer stopping distances, especially on wet roads. Overinfl ated tires, on the other hand, suffer from poor grip and reduce the vehicle's stability. Tire failure at high speed is a particular concern since it increases the potential for vehicle roll-over.To alleviate these problems, TPMS are being designed to continuously monitor the air pressure inside automotive tires. The purpose of TPMS is to provide a warning signal if the air pressure inside the tire falls outside maximum/minimum safe limits. Conventional TPMS consist of tire pressure modules that are either installed onto the wheel rim, inside the tire cavity, or are attached to the inner lining of the tire. The pressure sensors continuously measure the air pressure, as well as other physical quantities such as temperature and acceleration, and transmit the readings to an onboard receiver/display by radio frequency transmission.The direct and indirect methods are used to monitor tire pressure. The indirect system relies on the fact that an underinfl ated tire, with a smaller diameter, will rotate faster than a correctly infl ated tire. For these systems, each wheel contains a rotational speed sensor and the speed of each wheel is compared to the average speed of all the wheels to determine if one is rotating signifi cantly faster than the others. Indirect methods also include those measuring the distance of the wheel centers to the ground and identifying an underinfl ated tire as one with its wheel center closer to the ground. The direct system has sensors within each tire to measure the pressure directly and this data is relayed to the driver in real-time. Although the systems vary in transmitting options, most direct systems use radio frequency (RF) signals to send data to an electronic control unit.Currently, the electrical power for TPMS is provided almost exclusively by batteries, which have a limited lifespan and Tire pressure monitoring systems (TPMS) are becoming increasingly important to ensure safe and effi cient use of tires in the automotive sector. A typical TPMS system consists of a battery powered wireless sensor, as part of the tire, and a remote receiver to collect sensor data, such as pressure and temperature. In order to provide a maintenance-free and battery-less sensor solution there is growing interest in using energy harvesting ...

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Conventional energy harvester typically consists of a cantilevered composite piezoelectric beam which has a proof mass at its free end while its fixed end is mounted on a vibrating base structure. The resulting relative motion between the proof mass and the base structure produces a mechanical strain in the piezoelectric elements which is converted into electrical power by virtue of the direct piezoelectric effect. In this paper, the harvester is provided with a dynamic magnifier consisting of a spring-mass system which is placed between the fixed end of the piezoelectric beam and the vibrating base structure. The main function of the dynamic magnifier, as the name implies, is to magnify the strain experienced by the piezoelectric elements in order to amplify the electrical power output of the harvester. With proper selection of the design parameters of the magnifier, the harvested power can be significantly enhanced and the effective bandwidth of the harvester can be improved. The theory governing the operation of this class of cantilevered piezoelectric energy harvesters with dynamic magnifier (CPEHDM) is developed using the finite element method. Numerical examples are presented to illustrate the merits of the CPEHDM in comparison with the conventional piezoelectric energy harvesters (CPEH). The obtained results demonstrate the feasibility of the CPEHDM as a simple and effective means for enhancing the magnitude and spectral characteristics of CPEH.

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