A Novel Ergodic Sequential Logic CPG: Efficient FPGA Implementation and Realizations of Various Gaits and their Safe Transitions

In this study, a novel ergodic sequential logic (SL) central pattern generator (CPG) is presented. First, a novel ergodic SL oscillator is presented and it is shown that the oscillator can realize oscillations with various amplitudes and frequencies by adjusting its parameters. Second, using the oscillator, the ergodic SL CPG is presented. It is shown that the CPG can realize multiple gaits of a six-legged robot by adjusting its parameters. Third, a modulation method of the CPG to realize safe transitions between different gaits is proposed. Experiments validate that the modulation method can realize safe transitions between different gaits of the robot, whereas a straightforward method of changing the gaits leads to unsafe operations of the robot. Furthermore, it is shown that the ergodic SL CPG is much more hardware-efficient compared to a commonly used digital processor CPG. Finally, it is discussed that the presented CPG and its modulation method will contribute to develop a hardware-efficient smart gait controller of legged robots, which can realize safe gait changes.