Transcript Slide 1
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 ** 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 • Below is the original Tyndall IMU system tested by DCU 433MHz Radio Transceiver IMU Battery, Power Layer + 70g accelerometer Rev 1.7 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 •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 Required Current Comment Acceleromete rs +/- 10g +/- 2g Alternative pin-compatible sensor required Gyroscopes +/- 3,400°/sec 150°/sec or 600°/sec Alternative pin-compatible sensor required Sampling 150Hz (5 <=52Hz (1 Latency issue needs to be resolved 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 Original device uses 2g accelerometer Originally using 433MHz Radio and 30-50Hz max sampling rate Now investigating use of Zigbee or Nordic NRF201 radio to allow increased sampling rate 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 •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 •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 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 values Using 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)