This paper presents a novel posture control approach based on feedback compensation of the lateral acceleration. The narrow and small PR (Personal Robot) is required to control its posture for realization of the quick turning and vertical posture even on the bumpy road. However, in the conventional control approach using the posture angle as controlled variable, ZMP (Zero Moment Point) can not be settled to the desired point, when the perturbation of the tire pressure is happened to PR, and the condition of the road surface is changed. Furthermore, some gyro sensors and acceleration sensors have to be equipped to estimate the accurate posture angle for the conventional control approach. In this paper, a novel control approach only using one acceleration sensor and one gyro sensor is proposed to realize the desired ZMP at steady state. The proposed control approach can make the lateral acceleration of the PR into zero in order to realize the desired posture angle during turning and vertical posture even on the bumpy road. The effectiveness of the proposed approach is verified by the experiments using a prototype of the PR.
A new wheelchair add-on drive system using an active-caster is proposed in this paper. The proposed system enables a manual wheelchair to be driven in the same manner as the conventional electric wheelchair hence it equips single drive wheel. In this paper, the kinematics and dynamics of the wheelchair with the single active-caster are modeled for deriving a control law and analyzing the motion of a motorized wheelchair. To verify the availability of the proposed drive system, a prototype wheelchair is designed and built. The experiments using the prototype show expected moving capability in which the 2DOFs of the wheelchair are controlled independently with no restrictions of a non-holonomic constraint.
An attempt to extend passive dynamic walking from a slope to a horizontal surface have begun since the late 80's about the same time as the research on passive dynamic walking. A method using inclination of an upper body has been originally examined by McGeer, which enables a biped with the upper body to walk on the horizontal surface using counter torque of the torque generating to maintain the body inclination. However there are no deep insight into properties of the method such as stability against the inclination and robustness. Moreover, no researchers could achieve a real biped using the body inclination, and then the method would be sensitive against uncertainties (e.g., the ground undulation and small obstacles), accordingly. In this paper, we introduce an upper body and circular arc feet to a compass model biped and achieve various dynamic walking gait using thrust via the upper body inclination through numerical simulations. Stability of the walking gait is also analyzed using the Poincaré method. Moreover, a geometric tracking control using a cyclic motion of the biped walking is introduced in order to achieve more robust gait. Stability of the controlled walking is also analyzed using a Poincaré map of HZD. In addition, we discuss the difference between the walking using the upper body inclination and the geometric tracking controlled walking.
The human action of standing up is regarded as a key aspect of rehabilitation for maintaining a basic standard of daily life. At clinical sites, a different phenomenon that departs from the standard theory for this action has been observed, suggesting that a distinctive biarticular muscle function is involved. We therefore performed electromyography (EMG) kinesiology to analyze the action of standing up and model the results in order to clarify the function of the biarticular muscle in the lower extremity. During standing up with a vertically upward movement of the trunk, EMGs demonstrated full activity of the monoarticular extensors of the knee joint and the biarticular muscle of rectus femoris. In experimental analysis with this model, parallel linkage function of rectus femoris allowed standing up with monoarticular extensors of the knee joint alone providing the driving force. The analysis further showed that in the dynamic action of standing up, parallel linkage retains the inertial force generated by contraction of the monoarticular extensors of the knee joint and thus retains the force of rearward trunk falling and effectively functions to direct floor reaction force toward the center of gravity.
This paper describes a method of skill assist efficiency control by using semi-active assist mechanisms based on phase difference limitation method. The skill assist in this study means the motion correction effect in periodical motions. The semi-active assist mechanisms can make the assist force with the phase difference, because the mechanism uses elastic materials as the source of the assist force. This force is controlled by adjusting the fixed point of the elastic materials by using the connected actuator as a series-elastic actuator. We confirmed the motion correction effect of our skill assist based on the phase difference control in previous study. Our proposed method in this study can control the skill assist efficiency to arbitrary value by limitation of the phase difference. Moreover, we confirmed that the proposed method can control its effect through experiments with several value of the efficiency. As a result of this study, we confirmed the fundamental ability of our developed method to control the motion correction ratio depending on types of task or personal differences in periodical motions.