Research And Design On Human Motion Parameters Wireless Acquisition System

Three-dimensional human-computer interaction technology based on sensor, image processing is a hot research area at home and abroad. However, most current research are using wired network to transmit human motion sensing data, which brings a lot of trouble. This project raised a method to transmit human motion parameters by wireless network. And the work in this paper is to design a wireless data acquisition system, which aims at transmitting the sensor data to Sink node. There are three kinds of node in this system: sensor node, cluster header and Sink node. Sensor node collects human motion parameters. Cluster header receives, processes and transmits sensor data. Sink node receives sensor data which is transmitted by cluster header and transmits the data to PC machine. Besides designing the hardware and software of these three kinds of nodes, this paper mainly discusses communication protocol of this system, and the time synchronization mechanism which is an important support technology for wireless sensor network.Communication protocol should be designed to minimize the network energy consumption, and this system is only needed to consider the issue of sensor node power consumption. At the same time, the protocol should be designed to minimize the system packet loss rate, packet loss rate is an important measurement of the communication protocol. Networking and communication process is simply as follows: First, the nodes are initialized, Sink node periodically sends beaconing signals. Second, cluster header joins the network according to Sink node's beaconing signal, and then periodically sends beaconing signals, receives and transmits sensor data. Third, sensor node joins the network according to cluster header's beaconing signal, and then periodically collects data and sends them to cluster header. The experimental results show that under this communication protocol, the sensor node has a small energy consumption and the system has a low packet loss rate.Good time synchronization mechanism can improve the performance of communication protocol. According to the characteristics of this system, this paper proposes a time synchronization algorithm based on virtual timestamp. The algorithm works as follows: the parent node periodically sends beaconing signal, and the parent node cycle is equal to the time difference of sending two consecutive beaconing signals. Child node receives the beaconing signal and records the corresponding time. The cycle of child node should be equal to the time difference of two consecutive beaconing signal reception time. If it isn't equal, then the child node should adjust its cycle. The experimental results show that the system has a good synchronization performance.