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Embodied AI, or the tale of taming the fungus eater
Published in Arkapravo Bhaumik, From AI to Robotics, 2018
1.d) Walking in biped and quadruped: Central pattern generators (CPGs), are oscillatory neuron circuits modelled on the central nervous system and produce and govern rhythmic motor processes which are similar to known animal/human motor patterns. In nature, these processes work from within the organism, without any sensory input from limbs, other muscles or any other motor control, and are believed to be responsible for chewing, breathing, digesting and locomotion. Such rhythmic motor processes for locomotion have been confirmed for cats, dogs and rabbits and are believed to exist for human locomotion. A CPG can be said to be analogous to a pendulum, producing sinusoids at a constant frequency. A pattern generator is useful for mimicking known biological motor functions when it involves two or more motor processes such that each process follows the next one in a serial order. Therefore, to devise a CPG solution to a dynamic problem researchers design a number of primitives which work in a serial order to realise a biological process, such as walking or breathing.
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.