Passive Legs Research Articles

Biomechanical Evaluation of Stair Ambulation Using Impedance Control on an Active Prosthesis.

Active prostheses can provide net positive work to individuals with amputation, offering more versatility across locomotion tasks than passive prostheses. However, the effect of powered joints on bilateral biomechanics has not been widely explored for ambulation modes different than level ground and treadmill walking. In this study, we present the bilateral biomechanics of stair ascent and descent with a powered knee-ankle prosthesis compared to the biomechanical profiles of able-bodied subjects at different configurations of stair height between 102 mm and 178 mm. In addition, we include reference profiles from users with passive prostheses for the nominal stair height of 152 mm to place our findings in relation to the typical solution for individuals with transfemoral amputation (TFA). We report the biomechanical profiles of kinematics, kinetics, and power, together with temporal and waveform symmetry and distribution of mechanical energy across the joints. We found that an active prosthesis provides a substantial contribution to mechanical power during stair ascent and power absorption during stair descent and gait patterns like able-bodied subjects. The active prosthesis enables step-over-step gait in stair ascent. This translates into a lower mechanical energy requirement on the intact side, with a 57% reduction of energy at the knee and 26% at the hip with respect to the passive prosthesis. For stair descent, we found a 28% reduction in the negative work done by the intact ankle. These results reflect the benefit of active prostheses, allowing the users to complete tasks more efficiently than passive legs. However, in comparison to able-bodied biomechanics, the results still differ from the ideal patterns. We discuss the limitations that explain this difference and suggest future directions for the design of impedance controllers by taking inspiration from the biological modulation of the knee moment as a function of the stair height.

Secondary-Side Phase-Shift-Controlled Dual-Transformer-Based Asymmetrical Dual-Bridge Converter With Wide Voltage Gain

A novel dual-transformer-based asymmetrical dual-bridge (DT-ADB) converter with secondary-side phase-shift control strategy is proposed. The primary side of the DT-ADB converter is a fully active full bridge, and the secondary side is a semiactive bridge comprising of one active leg and two passive legs. The current and power of the two transformers in the converter are shared automatically by adopting primary-side-series and secondary-side-parallel configuration, and the turns ratio of the transformer is reduced by employing two transformers. The high-frequency-link inductor is reduced because the voltage applied on the inductor is reduced compared to previous converters, and hence the efficiency and power density can be improved. Zero-voltage turn-on of all the active switches and zero-current turn-off of all the diodes are achieved in a wide operation range. Furthermore, the turn-off losses of the secondary-side active switches are reduced because only half of the output current flows through the switches. Moreover, the proposed topology offers several other advantages including continuous output current and smaller output filter requirement. The operation principle is analyzed and experimental results are provided to verify the effectiveness and advantages of the proposed converter.

Model-Based Experimental Development of Passive Compliant Robot Legs from Fiberglass Composites.

We report on the methodology of developing compliant, half-circular, and composite robot legs with designable stiffness. First, force-displacement experiments on flat cantilever composites made by one or multifiberglass cloths are executed. By mapping the cantilever mechanics to the virtual spring model, the equivalent elastic moduli of the composites can be derived. Next, by using the model that links the curved beam mechanics back to the virtual spring, the resultant stiffness of the composite in a half-circular shape can be estimated without going through intensive experimental tryouts. The overall methodology has been experimentally validated, and the fabricated composites were used on a hexapod robot to perform walking and leaping behaviors.

Gait generation and change of direction for the underactuated three-legged robot

This paper describes a three-legged robot that consists of one actuated leg and two passive legs. The active leg has a knee joint and an ankle joint. The passive legs have no knee joint, although they have a passive ankle joint respectively. The passive leg part and the actuated leg part are linked by a hip part. The robot behavior is passive while the robot is supported by its passive legs and swings the actuated leg part. Generally, in the event that an actuator or a transmitting mechanism fails, robots cannot apply torques to the joint. We therefore took up a walking robot with passive knee joints not only for the energy-efficient walking but also with a view to making ambulation failsafe in case of mechanical failures.

1A1-G08 劣駆動3足機構における旋回移動運動

In this paper, the turning motion of a three-legged robot is subjected. The robot consists of one actuated leg and one pair of passive leg. The active leg has a knee joint and an ankle joint. And the passive leg has no knee joint, but it has a passive ankle joint. The passive leg part and the actuated leg part are linked by a hip part. The robot behavior is passive while the robot is supported by its passive legs and swings the actuated leg part. For the purpose of changing the direction of walking, additional joints at side legs are proposed.

A unified method to find active forces and passive wrench of some parallel manipulators with n SPS active legs and a passive leg

A unified analysis approach is proposed for solving the active force and the passive wrench of some parallel manipulators with n SPS-type active legs and an unactuated passive leg. Firstly, some mathematical formulae for solving the force transformation matrix and active force and passive wrench are derived, and many possible types of the unactuated passive constrained legs are synthesized. Secondly, three parallel manipulators with three to five SPS-type active legs and a different passive leg are presented to illustrate as how to solve their inverse kinematics, force matrix, active forces, and passive wrench, and singularity by using the force matrix. Thirdly, some examples are given, and solving results have been verified by the simulation mechanism approach.