In this application video, a 2-cam (16 Mpx) MSpeedDIC system is used to measure the displacement, velocity
& acceleration of a toy rocket upon (pressure) launch.
In the measurement, the acquisition speed/camera frame rate of 1000 Hz is selected. Although the max
resolution at full frame rate is 16 Mpx at 265 Hz/fps, the Region-of-Interest (RoI) for the cameras is cropped
in height to increase the operational framerate. The available frame rate is then updated in Istra4D for the selected
vertical RoI height, allowing 1000 Hz to be achieved with ca. 4 Mpx resolution.
The projection calibration is performed by rotating the stereo rig (whilst keeping the cameras and lenses fixed) away
from the test object. The 10mm double-sided calibration target is automatically recognized in the Istra4D V4.11
software via it’s QR-code, which entails information about the grid spacing, std. tolerances, and front/rear
properties (such as thickness, which is used for double-sided biplanar setups). The rear-side of the target is shown,
which is indicated as red circle at target axis. (This can also be seen later in the projection visualization model)
The projection parameters are computed live with feedback. Users can easily manoeuvre & orientate the target
based on the visual indicators.
A ringbuffer recording is performed at 1000 Hz capturing a total of 2500 frames/steps. The pre/post trigger was
set at the end of the recording, as such, the rocket is launched, then the trigger is initiated saving all the images
that occurred before the rocket left the station.
Using the marker “auto-detect” all coded markers are automatically found in Istra4D V4.11. A temporal plot of the
total displacement, total velocity, and total acceleration of one of the selected points can be seen.
What is interesting about the temporal plot is that although the velocity increases the further the rocket travels, the
rocket does actually not accelerate uniformly. Between steps 20 to 40, it is likely that pressure is building up within
the rocket body and from steps 40 to 80, it is likely that the pressure release is valve is then switched opened. In steps
80 to 120, the air is escaping from the rocket body (which is still connected from the station launcher).
In steps 120 to 140, the rocket decelerates most likely due to internal friction between the rocket body and station
launcher. As of step 140, the internal fraction is eliminated and the pressurized air slowly escapes, and the rocket launch
is flying from momentum impulse.
Motion Analysis of a toy (pressure-launched) rocket using the MSpeedDIC system in Istra4D V4.11
To learn more about how Dantec Dynamics can help you solve your testing challenges, contact us today.
