Analysis of Time Zero Reset method for Virtual Slope Walking

In our previous work, we proposed a novel method Virtual Slope Walking(VSW) for biped locomotion. Mechanical energy is restored by actively extending stance leg in this method. VSW has two kinds of implementations, termed self-excited mode and parametric excited mode, respectively. In self-excited mode, stance leg extension is controlled according to its angle, but the measure of leg´s angle is difficult in practical implementation; while in parametric excited mode stance leg extension is controlled according to time. In this paper, we investigate a method for VSW using parametric excited mode named Time Zero Reset method, which controlling stance leg extension with relative time, time zero is reset at each heelstrike. The method generates stable period-1 and multi-period walking cycles which not seen in VSW before. The results of stability analysis show the method has strong tolerance to disturbances. Compared to previous parametric excited mode with open-loop control, it has wider speed range and is more robust to disturbances with low cost as only touchdown sensors are needed.