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WP.2 Biomechanical

WP.2 Biomechanical. BC & KM. Performance Factor Identification. Literature review Identified papers that examined kinematic details during serve in players of mixed abilities…. Sequence of events: Initial knee extension Max knee extension velocity Max shoulder external rotation **

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WP.2 Biomechanical

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  1. WP.2 Biomechanical BC & KM

  2. Performance Factor Identification • Literature review • Identified papers that examined kinematic details during serve in players of mixed abilities….

  3. Sequence of events: • Initial knee extension • Max knee extension velocity • Max shoulder external rotation ** • Max trunk tilt angular velocity • Max upper torso velocity • Max pelvis velocity • Max elbow extension velocity • Max wrist flexion velocity • Max shoulder internal rotation velocity ** • Absolute comparison basis: • Angular displacement of wrist and elbow at and following impact

  4. Inertial body sensor integration • Below is the original Tyndall IMU system tested by DCU 433MHz Radio Transceiver IMU Rev 1.7 Battery, Power Layer + 70g accelerometer • Rev 1.7 IMU Sensor Specification • • 2 x +/- 2g accelerometer (2 x 2-axis ADXL202E) • • 2 x magnetometer (2 x 2-axis HMC1052) • • 3 x +/-150 °/sec gyroscope (3 x 1-axis ADXRS150)

  5. Issues Identified during Testing • DCU tests with professional tennis player using the above hardware • revealed the following issues: • Accelerometer range of +/- 2g inadequate • Gyroscope range of +/- 150°/s leads to saturation at high turn rate • Note: A single modified IMU with 600°/s gyros performed better but also saturated at high turn rate • Sampling rate of 30 samples/sec (1 Tx-Rx pair) was inadequate • Following the above tests, the following ‘ideal’ target for the IMU specification was written by DCU

  6. Current Investigation • To meet new target specification, currently looking at higher spec, pin-compatible gyro and accelerometer sensors and upgrading the radio transceiver Original gyro 150deg/sec Now looking at 1200 deg/sec device Originally using 433MHz Radio and 30-50Hz max sampling rate Now investigating use of Zigbee or Nordic NRF201 radio to allow increased sampling rate Original device uses 2g accelerometer Now looking at replacing with a 10g device • Challenges/Issues • Finding suitable, pin-compatible off-the-shelf sensor devices (mostly solved) • Time will be required to order/receive components, rework, calibrate and test final IMU layers – see Gantt later in presentation

  7. Current Status • Accelerometers • We have sourced +/-10g devices (ADXL210E) that are pin compatible • Devices now ordered from US and they should be received by mid-end of May • Gyroscopes • Looks like 1200 °/sec is the maximum we can provide with the current hardware • This would use pin compatible ADXRS300 modified to give 4x times standard range • Latency • Have completed preliminary work using a Zigbee radio transceiver • Currently achieving 300Hz sampling with Zigbee for 1 transmit/receive pair • Now looking at networking 5 transmitter devices and 1 receiver • Also evaluating use of Nordic radio to further decrease latency • We expect to have this work completed by end of May • Heading Info • Philip is developing IMU firmware for the microcontroller in format required for Labview GUI – will allow heading display using GUI based on magnetometer/accelerometer sensors • Calibration/Packaging • We have ordered a calibration table to calibrate IMUs • Working on packaging for IMU

  8. Gantt Chart • We would hope to have final units available for the end of June. The existing IMU systems would be used in the mean time for continued evaluation • Would be useful to know the deployment plans and dates, if dates fixed etc?

  9. Stroke Characterisation & Biomechanical Evaluation Captured a database of tennis motions using the VICON motion capture system. In addition, IMU data was captured along with the VICON data.Currently working on: - Simulating IMU readings from Motion Capture (VICON) data Using the motion of the joint "bones" to determine the expected accelerometer/gyro/mag valuesUsing the aligned IMU data as ground truth. - Using measured IMU data to animate a human skeleton (body) by mapping it to a motion in our motion database (vicon)

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