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CPG-Based Control of Serpentine Locomotion of a Snake-Like Robot
Published in Yunhui Liu, Dong Sun, Biologically Inspired, 2017
Usually, there are several ways to construct a CPG model by connecting different numbers of neurons. For instance, a dual-neuron model and a tri-neuron CPG model are shown in Figures 2.1b and 2.1c, respectively. These two CPG models have been adopted in the control systems of many bionic robots (Kimura, Akiyama, and Sakurama 1999; Lu et al. 2005). Due to the complicated structure and numerous computations, a CPG model with four or more neurons is not often used in practical applications Because the output of an individual neuron always has a positive value, the output of the CPG module yout, which is defined by subtracting the output of the second neuron y2 from the first neuron y1, is used to get a symmetrical rhythmic signal with both positive and negative values. yout=y1−y2
Muscle mechanics and neural control
Published in Youlian Hong, Roger Bartlett, Routledge Handbook of Biomechanics and Human Movement Science, 2008
Motor circuits in the spinal cord are not only relevant to execute stretch and withdrawal reflexes but also to enable natural locomotion. Animal studies provide strong evidence that the spinal cord contains the basic circuitry to produce locomotion. As early as 1911, Graham-Brown observed in the cat that coordinated flexor-extensor alternating movements could be generated in the absence of descending or afferent input to the spinal cord (Graham-Brown, 1911). The neural network in the spinal cord which has the capacity to produce this basic locomotor rhythm is called central pattern generator (CPG). The original half-centre model proposed by Graham-Brown consists of a flexor and an extensor half centre that individually possess no rhythmogenic ability, but which produce rhythmic output when reciprocally coupled. However, based on this model it is difficult to explain the diverse patterns which can be generated by spinal CPGs (Stein et al., 1998; Burke et al., 2001). To overcome this problem, it was proposed that multiple oscillators are flexibly coupled to create different patterns (Grillner, 1981). According to this model, spinal CPGs are able to realize many different motor behaviours like walking, swimming, hopping, flying and scratching. The basic pattern produced by a CPG is influenced by signals from other parts of the CNS and sensory information arising from peripheral receptors. This sensory feedback can help to increase the drive to the active motoneurons and is also needed for corrective responses which may be reflectively or voluntarily performed.
Biomechanics and Biomimetics in Flying and Swimming
Published in Akihiro Miyauchi, Masatsugu Shimomura, Industrial Biomimetics, 2019
Hao Liu, Toshiyuki Nakata, Gen Li, Dmitry Kolomenskiy
For example, Chowdhury et al. [35] translated the BCF mode carangiform swimming behavior of a biological fish to a robotic fish. The robotic fish model (kinematics and dynamics) is integrated with the Lighthill mathematical model framework to generate posterior body undulatory movements. A central pattern generator (CPG) controller consists of coupled networks capable of producing coordinated oscillatory patterns of rhythmic activity, while receiving simple adjustment signals [188]. In the amphibious snake robot [41], Crespi and Ijspeert used a locomotion controller based on the biological concept of CPGs; furthermore, the gaits are optimized online rather than as an off-line optimization process [41].
Control strategy for intraspinal microstimulation based on central pattern generator
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Xiongjie Lou, Yan Wu, Song Lu, Xiaoyan Shen
The central pattern generator (CPG) is a motor neuronal network located in the spinal cord that can generate rhythmic control output to stimulate muscle movement and control the rhythmic movement of hindlimbs (Rybak et al. 2006; Asadi and Erfanian 2011). Therefore, by electrically stimulating the site of CPG on the spinal cord, we can use a small number of electrodes to restore the movement of the paralyzed lower limbs in a way that is closer to the physiological state. Previous studies have demonstrated that the polarity reversal of stimulation signals reverses the alternating motor pattern in the spinal cord CPG site (Shen et al. 2022). The positive pulse stimulates this CPG site to induce forward and backward movements of the left and right hindlimbs, respectively. Once the polarity of the stimulation signal is reversed, negative pulse stimulation is used to induce backward and forward movements of the left and right hindlimbs, respectively. Therefore, we can realise a complete alternating movement of the rat hindlimbs by combining the two pulse signals with opposite polarities in a certain time sequence.
Bionic control of exoskeleton robot based on motion intention for rehabilitation training
Published in Advanced Robotics, 2019
Wendong Wang, Lei Qin, Xiaoqing Yuan, Xing Ming, Tongsen Sun, Yifan Liu
Thus far, there have been many applications of rehabilitation robots [9,10] for the lower-limbs treatments. Among these robots, the power-assisted exoskeletons have attracted much interest of researchers, especially using the central pattern generator (CPG) that basic neural component, which can harmonize rhythmic movements [11,12], such as movement of human, breathing, chewing, walking, etc. Combining the CPG concepts, the repetitive movement treatment has been addressed. Sajjad [13] proposed a CPG algorithm to generate trajectories of snake-shaped robots in different motion modes, such as serpentine and side-wound. Hadi [14] proposed a new real-time trajectory generation method for masticatory rehabilitation robots, and used CPG algorithm to develop mandibular trajectory and help the mandible to exercise recovery training. Moreover, it is shown that using the CPG model in the control system can facilitate natural interaction between the power-assisted exoskeletons and human.