A simple walking strategy for biped walking based on an intermittent sinusoidal oscillator

Abstract

SUMMARYThis paper presents a control algorithm for biped walking by extension of previous work in the fields of central pattern generator (CPG) and passive walking. The algorithm takes advantage of the passive dynamics of walking, assisting only when necessary with an intermittent sinusoidal oscillator. The parameterized oscillator is used to drive the hip joint; the triggering and ceasing of the oscillator during a walking cycle can be modulated by the sensory feedback. The results from simulation indicate a stable, efficient gait, and robustness against model inaccuracy and environmental variation. We also examine the effects of oscillator parameters and link parameters on the gait, and design a controller to suppress the bifurcation phenomenon based on the error of prior step periods.

Globally stable control of a dynamic bipedal walker using adaptive frequency oscillators

“…However, the influence of ǫ and other AFO parameters needs to be studied in a more systematic fashion. The absence of ǫ in (5) suggests that this parameter does not have a significant role in determining steady-state values of step frequency and stride length. But at the same time, the coupling strength ǫ determines the rate of adaptation of AFO frequency [7], and a such may have a critical role in maintaining stability as the walker's gait progresses towards steady state.…”

“…Figure 3(a) shows limit cycle solutions ( Θ, ω) for (5). The main finding is that, unlike the AFO-coupled LTI system referred to earlier [21], here the frequency of the limit cycle is not determined by the intrinsic dynamics of the system.…”

“…For the present study the ratio of hip to foot mass chosen was 10. The modified dynamic walker, shown in Figure 12, is based on the model presented in Fu [5]; it features curved feet and assumes a locking mechanism for the knees. The model's walking gait consists of two qualitatively distinct modes.…”

“…• The mode transitions are based on the walker model by Fu [5]. The first transition occurs when the swing leg becomes fully extended and the knee joint becomes locked.…”

“…Nakanishi [4] proposed a frequency adaptation algorithm for bipedal walking based on phase resetting. The stabilizing properties of phase resetting in a biped have been investigated by Fu [5]. Coupled nonlinear oscillator systems are also capable of achieving inter-leg coordination in bipedal walkers as well as coordination among the leg's own segments [4,6].…”