Reappearance of change in time of rotation axis with simulation in baseball-type acceleration sensor

Abstract

We develop an output simulator for a baseball-type acceleration sensor in which one three-axis sensor for low acceleration and three sensors for high acceleration are installed. The acceleration vector at any position inside this ball-type sensor in rotational motion is formulated on the basis of the assumption that all the sensors are in rigid configuration. Since this simulator can estimate kinematically the acceleration under the change in time of rotation axis on the sensor coordinate system, we investigate the behavior of the rotation axis suggested in the previous flight experiment. In order to confirm the accuracy of the sensor outputs, preliminary experiment is performed, in which acceleration outputs are measured by rolling the ball-type sensor along a slope. The comparison of obtained acceleration outputs with theoretical values shows sufficient agreement. At the same time, the moment of inertia of the ball-type sensor is measured. Sensor outputs are simulated under two different conditions, in one of which the rotation axis is changing in time and the axis is fixed in the other. As the result, the acceleration output in the former condition varies linearly while the output keeps almost constant in the latter. The measured outputs of the flight experiment successfully reappear in the results under the former condition. The error between the simulated and measured outputs is calculated to 18 trial data of straight and curve balls, and the errors in the former condition become smaller than those in the latter. The present result therefore concludes that the rotation axis of the ball-type sensor in flight changes with time.