Citation: Kawasaki, N.; Tonomura,
K.; Ohara, M.; Shinojima, A.; Takada,
Y. Effects on Trajectory of a Spear
Using Movement of Robotic Fish
Equipped with Spear Shooting
Mechanism. Robotics 2022, 11, 14.
https://doi.org/10.3390/
robotics11010014
Academic Editor: Marco Ceccarelli
Received: 10 December 2021
Accepted: 7 January 2022
Published: 11 January 2022
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Article
Effects on Trajectory of a Spear Using Movement of Robotic
Fish Equipped with Spear Shooting Mechanism
Naoki Kawasaki *, Kazuki Tonomura, Masashi Ohara , Ayane Shinojima and Yogo Takada
Department of Mechanical and Physical Engineering, Osaka City University, Osaka 558-8585, Japan;
m1651024@edu.kit.ac.jp (K.T.); m20ta006@hb.osaka-cu.ac.jp (M.O.); a18tl017@xg.osaka-cu.ac.jp (A.S.);
takada@eng.osaka-cu.ac.jp (Y.T.)
* Correspondence: n_k_ocu@outlook.jp
Abstract:
In Japan, the disruption of ecosystems caused by alien fish in lakes and ponds is a major
issue. To address this problem, we propose that the robotic fish COMET can assist in alien fish
extermination by adding the function of spear shooting. The way of extermination is that when
COMET finds an alien fish, let COMET approach an alien fish without being wary it and spear it.
In this study, we investigated the spear shooting process under different movement conditions to
determine the impact on the accuracy of the trajectory of the spear. The results confirmed that a
certain set of conditions can improve the accuracy of hitting the target with a spear using specific
movements of the robotic fish.
Keywords: motion simulation; robotic fish; spear shooting
1. Introduction
The disruption of ecosystems caused by alien fish is a global issue, including
in Japan [1]
.
In particular, this is because several different alien species of fish, including large-
mouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus), live in lakes and
ponds in Japan and it is difficult to recover the ecosystems of the Edo era [
2
,
3
]. Pre-
fectures and local governments treat alien fish as harmful ecosystem destroyers and
practice extermination [4,5].
In general, extermination is practiced through fishing, electric shock boats, gill nets and
spear guns [
6
–
8
] and are primarily practiced by humans. Only alien fish can be exterminated
by fishing and spear guns. However, they require a lot of manpower. Extermination
practiced by electric shock boats, or gill nets need less manpower. Although, there is a risk
of exterminating non-alien fish. Extermination by shooting a spear using a robotic fish can
be done without human intervention.
Several studies have been conducted for ecological surveys, such as fish tracking
using image processing on robotic fish [
9
–
11
]. Moreover, it has been confirmed that the
robotic fish COMET (compact observation machine equipped with tailfin) developed by
Aritani et al. [
12
] can track fish without them being aware of it. The specifications of
this small robotic fish are listed in Table 1 and the schematics of its internal structure are
shown in Figure 1. Figure 2 shows a photograph of the side view of the robot [
12
]. The
COMET consists of parts that are cut from acrylic resin and possess two joints. In addition,
magnetic actuators consisting of a neodymium magnet and a coil were attached to these
joints. COMET is equipped with a 2-cell 7.4 V, 250 mAh lithium polymer battery as a power
source. Power of magnetic actuators is supplied from the battery and the battery voltage
is stepped down to 5 V, 3.3 V and 2.8 V and supplied to the control board. The angular
velocity of the rolling motion when the COMET swims straight is approximately 120
◦
/s
and the angular velocity of the yawing motion is approximately 40
◦
/s.
Robotics 2022, 11, 14. https://doi.org/10.3390/robotics11010014 https://www.mdpi.com/journal/robotics
