Highly Maneuverable Biorobotic Underwater Vehicles 11.6 Discussion 297
Part B | 11.6
11.5.2 SPLINE
1. Tension and position control of a fishing line or cable [11.14]
2. Simultaneous tension and position control in a fishing line or cable [11.14]
3. Swimming of a 7:3 m-long cable to commanded
depth, using two SPLINE propulsors, one at each
end of the cable
4. Turning of a short-length cable while holding it
taut and maintaining depth in a shallow water tidal
basin [11.14].
Demonstrations (1–3) were carried out in large laboratyory tanks; number of propulsors: one in one end
only in (1–2, 4), and one at each end in (3).
11.5.3 RAZOR
1. Cruising and remotely operated vehicle (ROV)like maneuvering, including hovering and stationkeeping
2. Numerous demonstrations of underwater and surface maneuverings carried out in Narragansett Bay,
RI, in more realistic mission environments than is
possible in the laboratory.
11.6 Discussion
Exploratory transitioning to utility is a filtering process
applied to basic research. The material in this chapter and the papers on the underlying science [11.9, 11,
12, 15] indicate the steepness of the transition pyramid,
most being eliminated quickly. Anecdotally, the transition process of underwater vehicles appears to have
attained greater maturity than that of flying vehicles, if
non-biology-based micro air vehicles are excluded.
The section on integrated design principles shows
how disturbance-rejecting nonlinear sensing, which is
currently a large gap, should be built. In view of the
infancy of nonlinear sensing, we are far off from the full
potential of what biology-inspired integrated platforms
can offer.
In our experience, the research that transitions to
utility is that where understanding is developed to the
extent that a mathematical formulation of the mechanism is possible. In our design and control, scaling laws
and an understanding of the cycle-averaging process
have been found to be useful. To develop reliable control laws, we have experimentally calibrated full-scale
actuators in the operational range whenever possible.
We have not used any computational fluid dynamics because, in practice, it is postdictive and not predictive.
The value of actuator materials such as strong artificial muscles has been emphasized in the past for
actuation of shape deformation of animal-like propulsors [11.7, 44–48]. However, ionic polymer, or the
much heralded carbon nanotechnology is yet to make
an impact on platforms of 1 m scale.
The Naval utility of platform-length scales much
smaller than 1 m has not been demonstrated. This may
be due to boundary between the strengths of feasible
actuation that is stiff versus highly flexible. System
considerations indicate that some approaches such as
jets (of squid) are inherently inefficient compared to
flapping fins (of fish which impart more momentum
to the water without the constraint of internal bladder
size) and cannot be scaled up (the oxygen consumption
rate of squid is five to seven times higher than that of
fish) [11.49]. Furthermore, it does not seem to be useful
to develop approaches that are vulnerable to saltwater
corrosion and blockage due to biological growth, which
always accompanies prolonged exposure to a natural
oceanic environment. Caution is in order because, based
on past experience of underwater research at NUWC, in
some cases extrapolation of developments from clean
water to oceanic environments can be fatal.
By many accounts, the NUWC flapping fin propulsion and control technology has matured. These technologies have been built in affordable modular form
that is detachable/attachable to a platform. Future
prospects include their evaluation for stabilizing (and
recovering) platforms in distress and in high sea
states, or for tautening towed cables. Future interest
in biorobotics would be sustained if its mission value
is continuously demonstrated to the users and if it is
combined with conventional approaches. In basic research, an assessment needs to be made to identify the
nagging obstacles to the development of strong muscle
technology. In biorobotics basic research, integration
of the SPR mechanism with flapping fins needs to be
generalized. The results in Figs. 11.2 through 11.7 indicate that in the current stage of maturity, biorobotics is
straddling between the laboratory and near-shore open
waters.
Part B | 11.6
11.5.2 SPLINE
1. Tension and position control of a fishing line or cable [11.14]
2. Simultaneous tension and position control in a fishing line or cable [11.14]
3. Swimming of a 7:3 m-long cable to commanded
depth, using two SPLINE propulsors, one at each
end of the cable
4. Turning of a short-length cable while holding it
taut and maintaining depth in a shallow water tidal
basin [11.14].
Demonstrations (1–3) were carried out in large laboratyory tanks; number of propulsors: one in one end
only in (1–2, 4), and one at each end in (3).
11.5.3 RAZOR
1. Cruising and remotely operated vehicle (ROV)like maneuvering, including hovering and stationkeeping
2. Numerous demonstrations of underwater and surface maneuverings carried out in Narragansett Bay,
RI, in more realistic mission environments than is
possible in the laboratory.
11.6 Discussion
Exploratory transitioning to utility is a filtering process
applied to basic research. The material in this chapter and the papers on the underlying science [11.9, 11,
12, 15] indicate the steepness of the transition pyramid,
most being eliminated quickly. Anecdotally, the transition process of underwater vehicles appears to have
attained greater maturity than that of flying vehicles, if
non-biology-based micro air vehicles are excluded.
The section on integrated design principles shows
how disturbance-rejecting nonlinear sensing, which is
currently a large gap, should be built. In view of the
infancy of nonlinear sensing, we are far off from the full
potential of what biology-inspired integrated platforms
can offer.
In our experience, the research that transitions to
utility is that where understanding is developed to the
extent that a mathematical formulation of the mechanism is possible. In our design and control, scaling laws
and an understanding of the cycle-averaging process
have been found to be useful. To develop reliable control laws, we have experimentally calibrated full-scale
actuators in the operational range whenever possible.
We have not used any computational fluid dynamics because, in practice, it is postdictive and not predictive.
The value of actuator materials such as strong artificial muscles has been emphasized in the past for
actuation of shape deformation of animal-like propulsors [11.7, 44–48]. However, ionic polymer, or the
much heralded carbon nanotechnology is yet to make
an impact on platforms of 1 m scale.
The Naval utility of platform-length scales much
smaller than 1 m has not been demonstrated. This may
be due to boundary between the strengths of feasible
actuation that is stiff versus highly flexible. System
considerations indicate that some approaches such as
jets (of squid) are inherently inefficient compared to
flapping fins (of fish which impart more momentum
to the water without the constraint of internal bladder
size) and cannot be scaled up (the oxygen consumption
rate of squid is five to seven times higher than that of
fish) [11.49]. Furthermore, it does not seem to be useful
to develop approaches that are vulnerable to saltwater
corrosion and blockage due to biological growth, which
always accompanies prolonged exposure to a natural
oceanic environment. Caution is in order because, based
on past experience of underwater research at NUWC, in
some cases extrapolation of developments from clean
water to oceanic environments can be fatal.
By many accounts, the NUWC flapping fin propulsion and control technology has matured. These technologies have been built in affordable modular form
that is detachable/attachable to a platform. Future
prospects include their evaluation for stabilizing (and
recovering) platforms in distress and in high sea
states, or for tautening towed cables. Future interest
in biorobotics would be sustained if its mission value
is continuously demonstrated to the users and if it is
combined with conventional approaches. In basic research, an assessment needs to be made to identify the
nagging obstacles to the development of strong muscle
technology. In biorobotics basic research, integration
of the SPR mechanism with flapping fins needs to be
generalized. The results in Figs. 11.2 through 11.7 indicate that in the current stage of maturity, biorobotics is
straddling between the laboratory and near-shore open
waters.