Instrumentation & Measurement Magazine 26-2 - 54

To realize the adhesion pre-compression of the arc surface,
the swinging phase limb B needs to apply a main force
FSB
, and FBx
and FBz
to the arc surface. Due to the interaction of the force, the
arc surface will generate a reverse force FB
can be obtained by decomposing this force in the horizontal
x-axis direction and the vertical z-direction. At this time, the
body of the robot will be subjected to the reaction forces FOx
and FOz
and the swinging phase limb is driven to move to the left in
the horizontal direction by the horizontal direction FOx
limb A needs to be given, and the arc surface will be subjected
to the reverse force FqA
and FvDx
. To
suppress the influence of external forces in these two directions,
the downward adhesion force FvAz
of the stance phase
in the x direction. The force at
limb C is basically the same as that at limb A, and will not
be repeated here. The swinging phase limb D of the robot is
subjected to the adhesion forces FvDz
that hinder the
movement of the body of the robot in the x-axis and z-axis
directions.
The force analysis of the preloading state is:





M F   1    
   
Oy
M FF F F
M F F FF F
F F
Ox   
(


qA Bx
F
Bz vz
vDz
x
z
vAz
v z
C
vAz Bz vAz
qA Ox q x
F F F F F
vDx Bx
FOz
F FvDx
qC
2
A 1C 2
vz vDz
   
     
Oz     ) W<0
F F F xDO 0
It can be seen from the analysis of the above mechanical results
that the body of the robot will rotate clockwise around
the z-axis, counterclockwise around the x-axis and clockwise
around the z-axis. If the robot is expected to remain
stable in the y-axis direction, a force in the negative direction
of the x-axis needs to be applied at limb A, and a force
in the positive direction of the x-axis is applied at limbs C
and D. If it is desired to maintain rotational balance in the
x-axis direction, a force in the negative direction of the zaxis
needs to be applied at limb A, and a positive force in
the z-axis direction should be applied at limbs C and D. If
it is desired to maintain rotational balance in the z-axis direction,
a positive z-axis force should be applied to limbs
A and C, and a negative z-axis force should be applied to
limb D. Obviously, these three conditions can be satisfied at
the same time except for the C limb. At limbs A and D, the
overturning moment of gravity will be the same as the rotation
direction of the x-axis direction, so the robot will be
accelerated to fall. Therefore, the rotation requirements in
the x-axis direction should be given priority, and an active
control force should be applied to A, C, and D of the stance
phase limb.
When the other swinging phase limbs of the robot experience
the constant pre-pressure stage, the mechanical analysis
process is consistent with the above, and the corresponding
mechanical strategies are used to effectively control the rotation
of the body of the robot.
54
L ( )L 0
L ( )L 0
vCz
of the arc surface, in which the swing phase limb is
driven to move away from the arc surface by the vertical FOz
,
Test Experiment of Curved Surface Adhesion
Area of Imitation Gecko-mimicking Robot
To test the above-mentioned control algorithm corresponding
to the vertical arc surface, a corresponding robot test system is
built in this paper, as shown in Fig. 4. The test system includes:
the experimental prototype of the imitation gecko robot, the
inner and outer arc surfaces, the host computer controller, the
high-speed motion camera, etc. Among them, the host computer
can directly control the main controller of the robot's
Raspberry Pi, and the plexiglass made of acrylic material is
selected for the simulated arc surface, and the high-speed camera
is used to record the posture of the robot in real time during
the movement. To ensure that each task is executed according
to the specified time sequence, multi-threading technology is
adopted, and each task is executed in turn according to the way
of clock slice rotation. In addition, in order to ensure the realtime
performance of the task, a real-time patch is installed on
the embedded Linux operating system of the main controller.
When the gecko-mimicking robot moves in the vertical di(4)
rection,
the adhesion of the stance phase plays an important
role in the stability of the body of the robot. It is known from
the previous experiments that the adhesion area and the adhesion
force have a linear relationship. Therefore, in this section,
we track and record the change of the adhesion area between
the sticky sole and the curved surface of the gecko-mimicking
robot when the gecko-mimicking robot moves on the curved
surface under the position control and mechanical control
modes, respectively, to verify the improvement effect of the
mechanical control algorithm on the adhesion force. The test
experiment of the outer arc surface takes the movement of the
gecko robot in the amble gait with a radius of 400 mm as an example.
The high-speed camera is used to record the adhesion
area of the right front limb when it moves, and the adhesion
area is binarized. When the stance phase adopts position control,
the partial measurement results of its adhesion area are
shown in Fig. 4c, where the first 1.5 s is the state when the robot
is in contact with the arc surface and adheres and then enters
the constant force preloading stage. At 2 s, the robot swings
the phase limb to complete the preload, and then the swinging
phase limb becomes the stance phase limb; The 3 s~8 s is the
record of the adhesion area of the robot in the static state. The
area of the adhesion area does not change much from 3 s to 6
s, and the adhesion changes at the 7 s and 8 s, as shown in Fig.
4b. At this time, the swinging phase limb is the right hind limb,
which also proves that the movement of the swinging phase
limb has a greater impact on the stance phase limb.
After the active compliance control strategy is used to
adjust the active force of the supporting limb, the partial acquisition
results of its viscous area are shown in Fig. 4b. The
change of the adhesion area during the whole movement process
is counted, and the statistical results are shown in Fig. 4c.
It can be seen from the figure that the change of the adhesion
area is more gentle after the mechanical control is adopted.
The standard deviation statistics of the adhesion area fluctuations
of the supporting limbs between 2 s and 8 s show that
the standard deviation of the adhesion area is 9.18 cm2
after
IEEE Instrumentation & Measurement Magazine
April 2023
Instrumentation & Measurement Magazine 26-2

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