Instrumentation & Measurement Magazine 25-9 - 30

package called DeepLabCut. The toolbox uses the feature detectors
from DeeperCut [20]. By labeling only a few hundred
frames, one can train tailored, robust feature detectors that
are capable of localizing a variety of experimentally relevant
body parts. Semih Gunel et al. [21] present DeepFly3D, a software
that infers the 3D pose of tethered, adult Drosophila using
multiple camera images. DeepFly3D does not require manual
calibration, uses pictorial structures to automatically detect
and correct pose estimation errors, and uses active learning to
iteratively improve performance.
Behavior Analysis by Angular Phase
Diagram
The result of the experimental observation is used to reconstruct
the trends of two relative angles which can be clearly
shown in an angular phase diagram [22]. Changes in the lifting
angle (hip joint in the up-down direction) and femorotibial
angle (hip joint in moving direction) relative to swing angle
(knee joint) are focused in this project, as shown in Fig. 3
which illustrates gecko behaviors while trotting (337.1 mm/s)
and walking (66.7 mm/s) on horizontal surfaces and trotting
(241.5mm/s) and walking (30.6 mm/s) on vertical surfaces,
respectively. One point on the curve in each subplot represents
the values of two angles represented by the horizontal
and vertical coordinates. The density of the points denotes
speed. The smaller the density is, the faster the angle changes.
The shifting direction is indicated by the arrow, while the close
shape shows the periodicity. The amplitudes can be viewed
in each subplot by the curve location. The patterns of trotting
and walking in the horizontal and vertical substrate can be
contrasted and examined by combining all of the plots into a
single diagram.
As illustrated in Fig. 3, geckos travelling on horizontal surfaces
experienced faster joint rotation as their speed increased.
The forelimbs' swinging scope stayed close to 59 degrees when
moving forward but increased from 72 degrees to 79.2 degrees
when moving backward. The scope of the forward swinging
forelimbs increased from 33.7 degrees to 36.7 degrees with
increasing speed, while the scope of the backward swinging
forelimbs stayed nearly constant at 87.5 degrees. The lifting
angle of the forelimbs was always positive, to keep the center
of mass close to the surface when moving up vertical surfaces.
The hindlimbs' swing angles on both horizontal and vertical
surfaces were unaffected by different gaits [16].
Each phase plot of joint angle versus joint angle can also
be plotted independently. In addition to studying the curve's
characteristics, which are relevant from the pure biological
perspective, joint leg motion can be employed as a reference
for robot locomotion control by directly regulating the joint angles,
as in Central Pattern Generator (CPG) [23]. Even though
the results of the phase diagrams cannot be immediately applied
to the control of a robot's locomotion, they provide a
Fig. 3. Phase plots of joints angles when gecko moving on trotting and walking gaits on horizontal and vertical substrates. (From [16] with permission ©2009
Springer Nature.)
30
IEEE Instrumentation & Measurement Magazine
December 2022

Instrumentation & Measurement Magazine 25-9

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