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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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performance factor identification
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 **
      • 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
inertial body sensor integration
Inertial body sensor integration
  • Below is the original Tyndall IMU system tested by DCU

433MHz Radio Transceiver


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)
issues identified during testing

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
current investigation
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
current status
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
gantt chart
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?
stroke characterisation biomechanical evaluation
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)