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4 PRELIMINARY EXPERIMENT
4.1 Purpose
In addressing the above problem, the most difficult
challenge would be a collision between two air jet
streams, which probably generates turbulence.
Regarding a motion of an object in a single air jet
stream, hydrodynamic analysis is possible to some
extent, and there is a model-based control approach
(Becker, A. et al., 2009). However, neither theory nor
experiments have been reported on a behaviour of an
object in a turbulent field where two air jets collide,
therefore there have been absolutely no idea how to
address it. Thus, in order to get a hint for the problem,
we first decided to observe natural phenomena as it is.
Namely, as a preliminary experiment, we tried to
investigate the behaviour of the object in the
confluence area between the two air jets under a
condition that the two air jet flow rates are constant.
4.2 Preliminary Experiment Content
4.2.1 2 Observation of Object Behaviour at
the Confluence Area
Experiments were conducted to measure the object
levitation steady position in the state of collision
between the two air jet flow rates
and the
angles (
as parameters. An example is shown
below. Fig. 4 shows the results when the input voltage
5.5[V] and the injection angle
=
60[deg].From this result, it is possible to float by the
Coanda effect even in a fluid field where two jet
streams merge. And also, it was confirmed that the
resultant force applied to the object from the two air
jets can be roughly handled as a vector in a linear
lumped constant system.
4.2.2 An Experiment of the Object Relay by
a Passive and Heuristic Method
According to the above primary experiment, it was
confirmed that it is possible to hold an object at the
confluence area of two air jets, so next experiments
are performed to change these nozzle angles. As
shown in Fig.2, under the condition that the two air
jet flow rates are constant or zero, we conducted a
simple and heuristic experiment as follows;
(1) The left nozzle passively holds the object
vertically.
(2) Its angle slowly tilts toward the right nozzle
while the right nozzle is waiting for the object in
the intermediate point with the same air jet flow
rate.
(3) When the left air jet reaches the intermediate
point, then its air jet turns off and
simultaneously the right nozzle starts to
clockwisely rotate.
As shown in Fig. 5, immediately after the
confluence of the two air jets, Z has shown severe
vibrations with a maximum amplitude of about 180
mm. And after that, the vibration amplitude
gradually decreased passively due to air friction
and finally the success of the relay motion was
confirmed. And we can see that Y almost perfectly
synchronized with the movement of
. In this
passive and heuristic experiment, the relay
operation success rate was 7 out of 10 times (70%).
5 PROPOSED CONTROL
METHOD
5.1 Approach to Problem Solving
The above preliminary experiments are based on
simple natural phenomena where there is no artificial
control for the air jet. Here, we aim to realize more
stable relay operation by adding active feedback
control. Based on the preliminary experiment results,
we expected that regarding the horizontal direction,
the object can be passively stabilized by the Coanda
effect. Simultaneously regarding the vertical
direction, we expected that the feedback control can
work to stabilize the position utilizing the two air jet
resultant force. Specifically, we propose the
following three policies based on the assumption of
the lumped constant system.
Figure 4: Position of the levitated object and confluence
point of the two air jets.
A Spatial Motion Control to Transfer an Object between a Pair of Air Jet
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