Effects of compliant ankles on bipedal locomotion

Abstract

The influence of ankle compliance on bipedal robot locomotion is investigated in this paper. The focus is on reduction of energy consumption. The concept of hybrid zero dynamics is adapted to design walking gaits with three phases: underactuated heel roll, full actuation and underactuated toe roll. Ankle springs work in parallel with the ankle actuators. Stiffness and offset of the linear torsional springs at the ankle and gait parameters are optimized simultaneously. It is shown that simultaneous optimization of spring properties and gait is superior to optimizing the spring after the gait. Optimal spring stiffness and offset lead to a major reduction in energy consumption. Furthermore, a more human-like gait is observed for simultaneous optimization of gait and spring parameters compared to gait optimization with zero stiffness.

Compliant Joints Increase the Energy Efficiency of Bipedal Robot

“…This is contrary to Ref. 7 and Ref. 10 where they found ankle springs useful for stability and energetic efficiency.…”

Effects of knee locking and passive joint stiffness on energy consumption of a seven-link planar biped

“…Figure 3 shows that the optimization criterion is significantly reduced after introducing identical springs to both hip joints in parallel with existing actuator. It was however observed that adding springs to both knees or ankles were not effective in our case contrary to [19], [24] where they found ankle springs useful for stability and energetic efficiency. This is because we considered a flat foot impact and there is no double support phase and no rotation of support foot during entire swing phase.…”

“…The number of humanoid robots having arms, head and feet are increasing and researchers are concentrating on the energetic effects of arms, feet and compliance in the walking gaits by adding springs to the bipeds. Most of the researchers including [6], [19], [20], [17] are motivated by the hypothesis that bipeds with compliant ankles may be able to exhibit more natural-looking gaits with better energetic efficiency and walking stability as compared to bipeds without compliant joints. Several researchers studied that the design of the knee joint can help to improve the walking efficiency [10] and others concentrated on the addition of passive elastic members in the knee and hip joints.…”

Persistent homology for automatic determination of human-data based cost of bipedal walking

“…In [6] is a domain not seen in the human walking wherein the biped only has one contact point at the right heel (see Fig. 11 for an illustration).…”

“…Traditionally, most models of bipedal robots have employed a single domain model [1][2][3][4], which assumes an instantaneous double support phase and usually excludes the presence of feet (models of this form began with the so-called compass gait biped, which did not have knees or feet). Adding feet to the bipedal robot results in the need to extend the domain breakdown beyond a single discrete phase, which is typically done by either adding a phase where the heel is off the ground or a double support phase where both feet are on the ground, or any combination thereof [5][6][7]. This lack of consistency among models in the literature motivates the desire to determine if there does in fact exist a single ''universal'' domain breakdown that should be used when modeling bipedal robots, especially in the context of obtaining human-like bipedal walking.…”