The Research On Motion Capture System Based On Accelerate Sensors

With the development of Motion Capture Technique, the efficient and rapid capture of human body moving information has become reality. Motion Capture Technique has been applied in many areas such as sports competition, animated games, and film productions. The current Motion Capture Technique has been classified into four systems: Mechanical Motion Capture system, Acoustic Motion Capture system, Magnetic Motion Capture system and Optical Motion Capture system.According to the advantages and disadvantages in the four Motion Capture Systems mentioned above, this paper designs a 2D Motion Capture System based on STC89C58 MCU,CC1100 wireless transmit block and MMA7455 accelerate sensors, which is convenient and of high performance cost ratio. This system has an easy structure, a low cost and a desirable measuring performance. While used, this system only needs to fix sensors on the tester, no particular circumstance and other equipments are required. Also this system is easy to operate and afford. Sensors: This paper selects a wildly used three-axis accelerate sensor:MMA7455, which is of high performance ratio and low power consumption when working at 125HZ collecting mode. In order to measure the movement and gesture of human body precisely, this paper decides to distribute 10 sensors respectively among left and right ankle, left and right knee, left and right wrist, left and right elbow, neck and waist. Besides, all the sensors are fixed on the same direction, which is convenient for program writing.MCU: This paper selects STC89C58 MCU, which is of low power consumption, to drive sensors and acquire the data. The MCU simulates I2C bus to drive accelerate sensors in which way, each of the 10 sensors is carried by two ports. Wireless communication block: This paper selects UHF wireless communication chip, which has both sending and receiving function, to simultaneously send the data acquired by sensors to receiver CC1100.The receiver CC1100 then sends the data to upper computer through USB to Serial Port.Host computer : The host computer which is programmed in VB6.0 receives and processes the data sent by CC1100.We add MSCOMM controller to it and set it in byte-receive mode and the baud rate of serial ports is set at 115200bps.After analyzing the errors of sensors, the paper proposes several types of algorithm and then makes a comparison between them, finally reduces the errors of accelerate sensors by filtering below arithmetic average and also transforms the output of sensors into acceleration form. After that we first calculate the tilt angle of MMA7455 by space coordinate transform algorithm and then calculate the joint angle of human body movement by analyzing human body gesture, so that we can finally get the 2D space displacement of human body movement. Meanwhile by making a projection process of human body movement in 3D space, the movement appears to be more lively. At last, the host computer runs the painting program which paints the window repetitively, so that the movement images acquired are guaranteed real-time. At the same time, the system is able to draw the accelerate data for some particular spots and create accelerate curves by analyzing which we can observe the real-time changes on acceleration.Compared to other motion capture systems of the same kind, this system is convenient to use ,of high performance cost ratio and has strong anti-jamming capacity ,a low request for outside environment so that it is fitful for schools ,colleges and middle-small companies.