Towards autonomous locomotion: CPG-based control of smooth 3D slithering gait transition of a snake-like robot

Abstract

Snake-like robots with 3D locomotion ability have significant advantages of adaptive travelling in diverse complex terrain over traditional legged or wheeled mobile robots. Despite numerous developed gaits, these snake-like robots suffer from unsmooth gait transitions by changing the locomotion speed, direction, and body shape, which would potentially cause undesired movement and abnormal torque. Hence, there exists a knowledge gap for snake-like robots to achieve autonomous locomotion. To address this problem, this paper presents the smooth slithering gait transition control based on a lightweight central pattern generator (CPG) model for snake-like robots. First, based on the convergence behavior of the gradient system, a lightweight CPG model with fast computing time was designed and compared with other widely adopted CPG models. Then, by reshaping the body into a more stable geometry, the slithering gait was modified, and studied based on the proposed CPG model, including the gait transition of locomotion speed, moving direction, and body shape. In contrast to sinusoid-based method, extensive simulations and prototype experiments finally demonstrated that smooth slithering gait transition can be effectively achieved using the proposed CPG-based control method without generating undesired locomotion and abnormal torque.

Adaptive Path Following and Locomotion Optimization of Snake-Like Robot Controlled by the Central Pattern Generator

“…In this paper, different gaits are controlled by a Hopf CPG controller. The controller combined with the efficiency critic function (20) can generate uniform outputs with desired amplitudes and phase differences without additional adjustments. To explore the relation between locomotion efficiency and parameters, locomotion controlled by different gait parameters in the same flat ground with tangential fraction = 1 and normal fraction = 3 is simulated.…”

“…The optimization algorithm used in this research is inspired by the obligate brood parasitic behaviour of some cuckoo species in combination with the LeV y flights behaviour of some fruit flies. The optimization objection is maximized locomotion efficiency in (20), to given ranges of these parameters.…”

“…In [19], a unified neural oscillator network is researched to control three different types of locomotion by adjusting several parameters. Smooth transition and autonomous locomotion control methods are investigated in [20][21][22]. However, some important performances such as locomotion efficiency and path following accuracy of snake-like robots are not considered in these studies.…”

Triple-layered central pattern generator-based controller for 3D locomotion control of snake-like robots

“…However, the major defect of sin-based method is that it cannot ensure the smooth gait transition. 13,14 The biologists have proved that the rhythmic locomotion of vertebrates is controlled by central pattern generator (CPG). CPG is a neural network capable of generating rhythmic pattern outputs spontaneously and simultaneously.…”

“…A critically damped equation is used to modulate the amplitude and offset of each joint control function. 24,25,28 Bing et al 14 proposed a novel gradient system-based CPG combining the critically damped equation. The CPG can generate smooth transition of body shape and locomotion speed.…”