A central pattern generator circuit for rhythmic robotic chewing locomotion in low-voltage analog CMOS technology

Abstract

It is well known that rhythmic animal locomotive behavior such as walking, running, swimming, and flying is driven by biological neural networks with a phase-locked oscillatory behavior called a central pattern generator (CPG). This article describes a CPG circuit for the locomotion control of rhythmic robotic chewing. A two-neuron CPG model, which is slightly modified from the Matsuoka oscillator model, was implemented in a low-voltage analog CMOS circuit using the IBM 130 nm CMOS technology. A new concept of a −3 dB rhythmic chewing bandwidth has been introduced to account for the time constants in the model. The significance of the −3 dB chewing bandwidth is that any effort by the animal to chew at a faster rate than the inherent chewing bandwidth of that animal is likely to result in a reduced chewing force. Compared with the digital implementation, the analog CPG consumes less power and occupies less silicon area. The analog CPG consists of compensated current-mode low-pass filters and current mirrors implementing the neurons, which are cross-connected by inhibitory synaptic links. There are two tonic sensory inputs, two internal states, and two adaptation outputs for muscles for the CPG circuit.