Search

This study investigates local stability of a four-link limit cycle walking biped with flat feet and compliant ankle joints. Local stability represents the behavior along the solution trajectory between Poincare sections, which can provide detailed information about the evolution of disturbances. The effects of ankle stiffness and foot structure on local stability are studied. In addition, we apply a control strategy based on local stability analysis to the limit cycle walker. Control is applied only in the phases with poor local stability. Simulation results show that the energy consumption is reduced without sacrificing disturbance rejection ability. This study may be helpful in motion control of limit cycle bipedal walking robots with flat feet and ankle stiffness and understanding of human walking principles. [ABSTRACT FROM AUTHOR]

This paper focuses on chaos control of a seven-link torque-stiffness-controlled dynamic walking model, actuated by a bio-inspired control system. The biped consists of compliant hip, knee and ankle joints and flat feet. We employed Ott–Grebogi–Yorke and delayed feedback control methods, responsible for small errors around the equilibrium solution and large errors far away, respectively. In simulation, we study the stabilization of bifurcations and chaotic behaviors under diverse actuation parameters, and the convergence speed to 1-period gaits. The results of this paper may provide insights into motion control of dynamic walking robots and principles of human locomotion. [ABSTRACT FROM AUTHOR]

Walking behavior is modulated by controlling joint torques in most existing passivity-based bipeds. Controlled Passive Walking with adaptable stiffness exhibits controllable natural motions and energy efficient gaits. In this paper, we propose torque-stiffness-controlled dynamic bipedal walking, which extends the concept of Controlled Passive Walking by introducing structured control parameters and a bio-inspired control method with central pattern generators. The proposed walking paradigm is beneficial in clarifying the respective effects of the external actuation and the internal natural dynamics. We present a seven-link biped model to validate the presented walking. Effects of joint torque and joint stiffness on gait selection, walking performance and walking pattern transitions are studied in simulations. The work in this paper develops a new solution of motion control of bipedal robots with adaptable stiffness and provides insights of efficient and sophisticated walking gaits of humans. [ABSTRACT FROM AUTHOR]

This paper presents a seven-link dynamic walking model that is more close to human beings than other passivity-based dynamic walking models. We add hip actuation, upper body, flat feet, and ankle joints with torsional springs to the model. Walking sequence of flat-feet walkers has several substreams, which forms bipedal walking with dynamic series of phases. We investigate the effects of ankle stiffness on gait selection and evaluate different gaits in walking velocity, efficiency, and stability. Experimental results indicate that ankle stiffness plays different roles in different gaits and the gaits, which are more close to human walking with moderate speed, achieve better motion characteristics. [ABSTRACT FROM PUBLISHER]

Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. In this paper, we investigate the effects of foot shape on energetic efficiency and dynamic stability of passivity-based bipeds with upper body. Three walking models with point feet, round feet and flat feet were presented. Each model has an upper body constrained to keep midway between legs. We use computer simulations to find which foot shapes are indeed optimal in view of energetic efficiency and dynamic stability for a passive dynamic biped with upper body. Simulation results indicate that feet improve both the energetic efficiency and dynamic stability of passive dynamic bipeds. [ABSTRACT FROM AUTHOR]

In human walking, toes play an important role in supporting the body and controlling the forward motion. These functions are achieved by muscles and tendons around toe joints. To further understand the importance of toe and how toe muscle functions affect the locomotion, we employ a simple bipedal walking model with compliant joints. The ankle joints and toe joints are modeled as torsional springs and the actuation patterns are similar to that of normal human walking. Experimental results show that adding adaptable compliant toe joints could benefit the stability and energy efficiency. By generating plantar flexion moment after heel-off, the toes contribute to stabilize the body and control the forward motion. In addition, multi-joint foot structure could improve the energy efficiency by reducing the energy consumption of ankle joints. A proper toe actuation pattern could result in a proper toe dorsiflexion and reduce the maximal ankle plantar flexion, leading to a smoother and more efficient locomotion. [ABSTRACT FROM AUTHOR]