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Demonstrating measurement of gyroscopic effects applied to a soccer ball Willem Boshoff wboshoff@nmisa.org. Content. Background Technology Integration Demonstration Conclusion. Background.

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  1. Demonstrating measurement of gyroscopic effects applied to a soccer ballWillem Boshoffwboshoff@nmisa.org

  2. Content • Background • Technology • Integration • Demonstration • Conclusion

  3. Background • It is becoming common in sport transmissions to have real-time display of electronically measured data • Examples in cricket and motorsport • Many existing patents for instance to track golf balls • Many ways to measure: • Transmitted signal picked up by 3 receivers using triangular calculation for position • GPS on board • Image capturing and frame grabbing • This presentation suggest a method of measuring only the gyro effects on a soccer ball. Not included are other factors like acceleration and direction • Signals can be stored and analysed historically or transmitted real time to a dedicated receiver for analytical purposes • We suggest an ‘open protocol’ transmission for public use • Third party software • User specific software for analytical and training use

  4. Technology • Solid state gyroscopes X, Y and Z • Analog Devices manufactures angular rate sensors using its surface-micromachining process (operation) • ADIS 16100 X 3 • SPI digital interface for 12 bit accuracy • Sensitivity is ±300º/s which can be increased by adding external passive components • Maximum g-force without damage: 2000g • Microprocessor • Similar to processors used in household appliances • Very efficient battery usage • Integrated and lightweight • Microchip PIC processor (16F872 at 20Mhz) • SPI interface • UART serial IO (RS232)

  5. Technology continued • Data • Real time at 115200Baud • Protocol: 00FFF, 00FFF, 00FFF; • Typical static position data: 007CC, 007D0, 007C0; • Transceiver / transmitter • 2.4Ghz serial transceiver transmitting RS232 protocol • Battery • Lithium Polymer 3 cell 11.1V • Current: <100mA

  6. Integration Microprocessor Receiver X-Gyro Transmitter Y-Gyro Open Protocol Z-Gyro User device Lithium Polymer Battery

  7. Software • PIC programmed using C-Compiler • // ************Gyro1 • long send_to_gy1(int16 gy_data) • { • cmdout = gy_data; • datinl = input(DOUT); • datinl = 0; • output_high(DIN); • output_high(CLK); • output_low(CS1); • delay_us(2); • for (i=1;i<=16;++i) • { • output_bit(DIN, shift_left(&cmdout,2,0)); • delay_us(2); • output_low(CLK); • delay_us(4); • shift_left(&datinl,2,input(DOUT)); • output_high(CLK); • } • output_high(CS1); • rotate_right(&datinl,2); • datinl = datinl & 0b0000111111111100; //Mask lsbvirgeraas • return(datinl); • }

  8. Software continued • User device sample programmed using VB6 • If Len(workstr) > 19 Then • If Mid(workstr, 20, 1) = ";" Then • lsbyte = Mid(workstr, 4, 2) • msbyte = Mid(workstr, 2, 2) • Gyro1 = Val(convt(lsbyte, msbyte)) • lsbyte = Mid(workstr, 11, 2) • msbyte = Mid(workstr, 9, 2) • Gyro2 = Val(convt(lsbyte, msbyte)) - 62 • lsbyte = Mid(workstr, 18, 2) • msbyte = Mid(workstr, 16, 2) • Gyro3 = Val(convt(lsbyte, msbyte)) + 12 • End If

  9. Demonstration • Ball • Raw data stream • User program example

  10. Conclusion • This demonstration was very simple only measuring 3 gyro effects • Very little optimisation of embedded software to eliminate noise and increase sensitivity • User program is a simple demonstration on a slow computer • Can be presented in 3D or similar environments making it much more user friendly as well as presentable • Applications: • Discuss • Javelin • Etc

  11. END • wboshoff@nmisa.org • Thank you

  12. Operation of resonance gyro • The ADIS16100 operates on the principle of a resonator gyro. Two polysilicon sensing structures each contain a dither frame, which is electrostatically driven to resonance. This produces the necessary velocity element to produce a Coriolis force during angular rate. At two of the outer extremes of each frame, orthogo-nal to the dither motion, are movable fingers that are placed between fixed pickoff fingers to form a capacitive pickoff structure that senses Coriolis motion. The resulting signal is fed to a series of gain and demodulation stages that produce the electrical rate signal output. The rate signal is then converted to a digital representation of the output on the SPI pins. The dual-sensor design rejects external g-forces and vibration. ….. • <BACK>

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