© NMISA 2010

Demonstrating measurement of gyroscopic effects applied to a soccer ball

Willem Boshoffwboshoff@nmisa.org

© NMISA 2010

Content

• Background• Technology• Integration• Demonstration• Conclusion

© 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

© NMISA 2010

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)

© 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

© NMISA 2010

Integration

Mic

ropr

oces

sor X-Gyro

Tr

ansm

itter

User device Lithium Polymer Battery

Y-Gyro

Z-Gyro

Open Protocol

Rece

iver

© 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);– }

© 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

© NMISA 2010

Demonstration

• Ball• Raw data stream• User program example

© 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

© NMISA 2010

END

• wboshoff@nmisa.org• Thank you

© 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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