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Biologically Inspired Robotics
TABLE 2.4
Relation between the Direction of the Robot and the
Controlled Bias Input
Orientation of the Head
Δu 0 > 0
Δu 0 < 0
Right
7XUQOHIW
7XUQULJKW
Left
7XUQULJKW
7XUQOHIW
It is difficult to apply a uniform rule such as a left or right turn for wheeled
drive robots to the snake-like robot. The turn direction of the creeping
motion is mainly determined by two factors: the sign of bias Δu 0 and the
direction of the head module at the time when the signal begins shifting.
If the orientation of the head is toward the right, a positive value of bias Δu 0
will carry out a left turn, whereas a negative value of bias Δu 0 will cause a
right turn. A reverse situation occurs when the orientation of the head is
toward the left. The principle for controlling the direction of a snake-like
robot is shown in Table 2.4.
2.4.5 Control of the Round Motion
With an elongated and limbless body, a snake can perform not only turn
motions to avoid an obstacle but also round motions to escape from irregular
terrain. This is one of the most important characteristics of the snakes that
is different from other animals. Utilizing this advantage of the snake, the
snake-like robot can also creep through barriers conveniently.
In order to achieve this kind of motion, the frequency of the excitation signal for the first joint angle is altered from A to B in the half period, as shown
in Figure 2.10. This change is transmitted to the next joint consecutively in
the same way as that in turning motion. From Figure 2.10b, we can see that
the increment of the signal period has resulted in a smaller phase difference between two adjacent joint angles. Thus, the locomotion curve of the
snake-like robot will have larger motion amplitude. Consequently, an asymmetric forward locomotion to pass around the obstacle is achieved. From the
above discussion of the linear relation between the output period and the
time constant (τ 1 and τ 2 ) of the CPG, the desired output can be generated by
changing the time constant. This means that the round motion can be performed while the time constant is changed from the head joint to the tail joint
one joint at a time with a constant interval.
2.5 Experiments
To verify the validity of the CPG-based control system, some experiments were
carried out on our snake-like robot (Figure 2.11). The robot model is composed
Biologically Inspired Robotics
TABLE 2.4
Relation between the Direction of the Robot and the
Controlled Bias Input
Orientation of the Head
Δu 0 > 0
Δu 0 < 0
Right
7XUQOHIW
7XUQULJKW
Left
7XUQULJKW
7XUQOHIW
It is difficult to apply a uniform rule such as a left or right turn for wheeled
drive robots to the snake-like robot. The turn direction of the creeping
motion is mainly determined by two factors: the sign of bias Δu 0 and the
direction of the head module at the time when the signal begins shifting.
If the orientation of the head is toward the right, a positive value of bias Δu 0
will carry out a left turn, whereas a negative value of bias Δu 0 will cause a
right turn. A reverse situation occurs when the orientation of the head is
toward the left. The principle for controlling the direction of a snake-like
robot is shown in Table 2.4.
2.4.5 Control of the Round Motion
With an elongated and limbless body, a snake can perform not only turn
motions to avoid an obstacle but also round motions to escape from irregular
terrain. This is one of the most important characteristics of the snakes that
is different from other animals. Utilizing this advantage of the snake, the
snake-like robot can also creep through barriers conveniently.
In order to achieve this kind of motion, the frequency of the excitation signal for the first joint angle is altered from A to B in the half period, as shown
in Figure 2.10. This change is transmitted to the next joint consecutively in
the same way as that in turning motion. From Figure 2.10b, we can see that
the increment of the signal period has resulted in a smaller phase difference between two adjacent joint angles. Thus, the locomotion curve of the
snake-like robot will have larger motion amplitude. Consequently, an asymmetric forward locomotion to pass around the obstacle is achieved. From the
above discussion of the linear relation between the output period and the
time constant (τ 1 and τ 2 ) of the CPG, the desired output can be generated by
changing the time constant. This means that the round motion can be performed while the time constant is changed from the head joint to the tail joint
one joint at a time with a constant interval.
2.5 Experiments
To verify the validity of the CPG-based control system, some experiments were
carried out on our snake-like robot (Figure 2.11). The robot model is composed