Inertial sensor orientation for cricket bowling monitoring

Inertial sensors are a potential method of measuring the elbow angle during cricket bowling, currently an indicator of illegal bowling. To detect the elbow angle it was necessary to orient sensors relative to the elbow axis. An elbow orientation exercise was developed and the sensor orientation relative to the elbow axis calculated for upper-arm, forearm and wrist mounted sensors for different muscle loading and wrist rotation. Inertial rate-gyroscope outputs were compared for sensors before and after adjustment for elbow-axis orientation. This output was compared to the results obtained from a Vicon motion capture analysis system. Adjusting the sensor orientation based on the output from the orientation exercise improved the correlation between outputs of the upper-arm and forearm sensors but also indicated that the sensors were susceptible to muscle loading and wrist rotation effects that will need to be accounted for in any sensor based illegal bowling detection system.