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CPG-Based Control of Serpentine Locomotion of a Snake-Like Robot
Published in Yunhui Liu, Dong Sun, Biologically Inspired, 2017
When the rhythmic excitations exerted on each joint of the snake-like robot are sinusoidal waves, a symmetrical undulatory locomotion will be obtained. Because the winding angles to the left and right balance out, the robot proceeds in a straight line of travel on balance. However, as shown in Figure 2.9, if the amplitude of a wave in the half period is altered from A to B, this change will be transmitted to the next joint successively after a constant interval Δt and thus the balance state will be shifted accordingly. Subsequently, the overall direction of the snake-like robot will be changed. Here, interval Δt should be the same value as the phase difference between the CPGs so that the change of the parameters can be continuous. This can be calculated from Equation (2.5). Due to the linear relation between the output amplitude and the driving input u0 of the CPG, the value of the bias ΔA can be adjusted by driving input u0 directly. Thus, a right or left turning motion can be executed by exerting a positive or negative bias Δu0 on the amplitude of the joint angles from the head to the tail.
Swimming
Published in Malcolm S. Gordon, Reinhard Blickhan, John O. Dabiri, John J. Videler, Animal Locomotion, 2017
John O. Dabiri, Malcolm S. Gordon
A broad range of aquatic animal species have independently converged on the use of undulatory locomotion, including eels, water snakes, and water worms. Figure 3.35 illustrates the body shape and kinematics that we use to construct a model of the swimming dynamics.
Exploiting natural dynamics for gait generation in undulatory locomotion
Published in International Journal of Control, 2020
Taylor Ludeke, Tetsuya Iwasaki
In conclusion, Definitions 3.2 and 3.3 fully describe an undulatory gait for a long, slender body subject to resistive anisotropic forces from the environment. The natural gait can be calculated in an instant using the explicit formulas that analytically show how the gait is affected by system parameters. The gait exploits natural dynamics of the body-environment system for efficient locomotion, and the travel speed can be adjusted by setting the resonance appropriately through the stiffness value. The result is useful for designing gaits of robotic locomotors as well as for understanding the mechanisms underlying undulatory locomotion observed in nature.