A sensor system for measuring human motions is presented. The system consists of a number of miniature wireless inertial sensors that are attached to limbs of a person, and a PC with a wireless receiver that interprets and presents the measurement data. Each of the sensors measures 3D-acceleration, 3D-magnetization (earth magnetic field) and 3D-angular speed (gyroscopes). The data is transmitted via a proprietary protocol on an 802.15.4 radio. The angular accuracy of the calibrated system was found to be better than 3 degrees. The system is currently being applied in a pilot trial for motor rehabilitation of stroke patients.

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This paper reports the method and results of amplifying the power output of a piezoelectric energy harvester excited by random vibrations. The amplification is achieved by applying a dual-mass-spring system. A maximum power amplification of 80 times has been experimentally demonstrated. The generated power output from a piezoelectric energy harvester, when excited by asmeasured random vibrations, amounts to 28.9 µW. This is sufficient to operate a battery-free Tire Pressure Monitoring System (TPMS) for wireless sensing of pressure and temperature in car tires. Thus, the piezoelectric energy harvester with power amplification is proved to be a viable solution to replace batteries in the TPMS application.

In this paper, we highlight considerations for synchronization issues in body area networks. Requirements for the synchronization accuracy in body area networks depend on the application at hand. Synchronization may be needed for power management, sample ordering, calculation of stimulus responses and for sensor fusion. This paper provides a theoretical exercise to help understand the accuracy required for typical human motion sensing. It gives an overview of various synchronisation strategies used and implemented in prototype systems. Lessons learnt from practical implementations using Bluetooth, an IEEE 802.15.4 proprietary network and Nanonet are presented to illustrate the principles involved.The discussion provides some considerations and the requirements for typical WBAN applications.

A wireless energy autonomous filling yarn detector for an air jet weaving machine has been designed, built and tested on an opto-mechanical mock-up of the weaving loom. The energy autonomous operation of the detector is sustained by a commercially available vibrational energy harvester which can deliver several mW to the sensor node. The sensor node relies on the combination of three main blocks: an optical detector, a microcontroller and a wireless transceiver. The first block is responsible for the detection of the filling yarn, the wireless transceiver for the communication with the base station integrated with the weaving machine controller, while the microcontroller supervises and regulates the overall system operation. The node has been designed and assembled selecting commercial off-the-shelf components among the most power efficient available on the market. In order to further limit the power consumption, the trigger to wake up the sensor and start a measurement relies on the same optical link used for the filling yarn detection. After a yarn detection, the system is configured to communicate the event to the base station and go back to sleep. It has been demonstrated that at a machine speed of 1500 rpm, the vibrational energy harvester can harvest a power of 11 mW while the sensor node board only consumes 2.5 mW on the average. Keywords-wireless sensor; energy autonomous; filling yarn detector; low power sensor nodeI.