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© NMISA 2010 Demonstrating measurement of gyroscopic effects applied to a soccer ball Willem Boshoff

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1 © NMISA 2010 Demonstrating measurement of gyroscopic effects applied to a soccer ball Willem Boshoff

2 © NMISA 2010 Content Background Technology Integration Demonstration Conclusion

3 © NMISA 2010 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 © NMISA 2010 Technology Solid state gyroscopes X, Y and Z –Analog Devices manufactures angular rate sensors using its surface-micromachining process (operation)(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 © NMISA 2010 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 © NMISA 2010 Integration Microprocessor X-Gyro Transmitter User device Lithium Polymer Battery Y-Gyro Z-Gyro Open Protocol Receiver

7 © NMISA 2010 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 lsb vir geraas – return(datinl); –}

8 © NMISA 2010 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 © NMISA 2010 Demonstration Ball Raw data stream User program example

10 © NMISA 2010 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 © NMISA 2010 END Thank you

12 © NMISA 2010 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. …..

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