A Novel Adjustable Damper Design for a Hybrid Passive Ankle Prosthesis

Specifications of actuators when interacting with biological systems such as the human body are entirely different from those used in industrial machines or robots. One important instance of such applications is assistive devices and prostheses. Among various approaches in designing prostheses, recently, semi-active systems attracted the interest of researchers. Even more, some commercial systems benefit from designs such as implementing an adjustable damper in the ankle prosthesis to increase range of motion. The main reason for adding damper is to assist amputees’ walking locomotion on slopes (especially downward). In this paper, we introduce a hydraulic damper design for use in the transtibial prosthetic foot. In the fabricated hydraulic prosthetic foot, two one-way flow control valves are exploited to tune the damping ratio in the plantar flexion and dorsiflexion, independently. Using the carbon prosthetic foot in series to a damper and spring could improve mimicking intact foot movement. First, we present the details of the damper and the prosthesis mechanical design. Then, we introduce experiment-based modeling for the damper’s conceptual design in the proposed prosthesis using SIM-Hydraulic and MATLAB. This device is fabricated and tested in a pilot experiment. The compact design with reduced weight and size of the prosthetic foot are additional advantages of the proposed prosthetic foot.

Effect of Trunk Swinging Behaviors on Planar Bipedal Walking with an Upper Body on Gentle Slope

Bipedal walking locomotion is one of the characteristics of human behavior. Both the lower body and the upper body (trunk) behaviors affect walking characteristics. To achieve a suitable gait, it is important to understand the effect of the trunk behavior. Therefore, in this paper, the effects of three types of trunk swinging behavior on planar bipedal gait in a model with an upper body – forward swinging, backward swinging, and no swinging – were evaluated using numerical simulations. To reduce control inputs and reflect the effect of upper body behavior, an underactuated bipedal walker without knee joints was adopted. This walker walked down a gentle slope using only hip actuation between the stance leg and the trunk. As a result, unique gait characteristics that depended on the direction of the trunk swinging behavior were found, including a longer step length and a lower-frequency gait with forward trunk swinging behavior and a shorter step length and higher-frequency gait with smaller angular momentum with backward trunk swinging behavior.

Choosing the Best Locomotion Mode in Reconfigurable Rovers

The use of autonomous rovers for planetary exploration is crucial to traverse long distances and perform new discoveries on other planets. One of the most important issues is related to the interaction between the rover wheel and terrain, which would help to save energy and even avoid getting entrapped. The use of reconfigurable rovers with different locomotion modes has demonstrated improvement of traction and energy consumption. Therefore, the objective of this paper is to determine the best locomotion mode during the rover traverse, based on simple parameters, which would be obtained from propioceptive sensors. For this purpose, interaction of different terrains have been modelled and analysed with the ExoTeR, a scale prototype rover of the European ExoMars 2020 mission. This rover is able to perform, among others, the wheel walking locomotion mode, which has been demonstrated to improve traction in different situations. Currently, it is difficult to decide the instant time the rover has to switch from this locomotion mode to another. This paper also proposes a novel method to estimate the slip ratio, useful for deciding the best locomotion mode. Finally, results are obtained from an immersive simulation environment. It shows how each locomotion mode is suitable for different terrains and slopes and the proposed method is able to estimate the slip ratio.

Boosting the efficiency of a footstep piezoelectric-stack energy harvester using the synchronized switch technology

In this article, the self-supported power conditioning circuits are studied for a footstep energy harvester, which consists of a monolithic multilayer piezoelectric stack with a force amplification frame to extract electricity from human walking locomotion. Based on the synchronized switch harvesting on inductance (SSHI) technology, the power conditioning circuits are designed to optimize the power flow from the piezoelectric stack to the energy storage device under real-time human walking excitation instead of a simple sine waveform input, as reported in most literatures. The unique properties of human walking locomotion and multilayer piezoelectric stack both impose complications for circuit design. Three common interface circuits, for example, standard energy harvesting circuit, series-SSHI, and parallel-SSHI, are compared in terms of their output power to find the best candidate for the real-time-footstep energy harvester. Experimental results show that the use of parallel-SSHI circuit interface produces 74% more power than the standard energy harvesting counterpart, while the use of series-SSHI circuit demonstrates a similar performance in comparison to the standard energy harvesting interface. The reasons for such a huge efficiency improvement using the parallel-SSHI interface are detailed in this article.

Development of an Insect-Inspired Hexapod Robot Actuated by Soft Actuators

Insects are one of the most diverse group of animals on the planet and are almost ubiquitous. Their walking locomotion has inspired engineers and provided effective solutions for designing transport methods for legged robots. In this paper, we introduce a hexapod walking robot that mimics the design and walking motions of insects. The robot is characterized by small size, light weight, simple structure, and considerably fast walking speed. Three pairs of its legs are driven by three five-degrees-of-freedom (5DOF) soft actuators based on dielectric elastomer (DE) actuators which can provide up to five movements (including three translations and two rotations) within a compact structure. The robot imitates the crawling motion of an insect using the alternating tripod gait. The experiments show that the robot can achieve an average walking speed of 5.2 cm/s (approximately 21 body-lengths per minute) at 7 Hz of actuation frequency on flat rigid surfaces. Furthermore, the robot also demonstrates the omnidirectional capabilities of walking sideways and rotating its body direction, which enhance the potential of applying the proposed robot in practical uses.

Synchronized Switch Harvesting on Inductor Interface to Promote Piezoelectric Stack Energy Harvesting From Human Walking

In this paper, a self-supported power conditioning circuit is developed for a footstep energy harvester, which consists of a monolithic multilayer piezoelectric stack with a force amplification frame to extract electricity from human walking locomotion. Based on a synchronized switch energy harvesting on inductance (SSHI) interface and a peak detector topology, the power conditioning circuit is designed to optimize the power flow from the piezoelectric stack to the energy storage device under real-time human walking excitation instead of a simple sine waveform input, as reported in most literatures. The unique properties of human walking locomotion and multilayer piezoelectric stack both impose complications for circuit design. Three common interface circuits, e.g. standard energy harvesting (SEH) circuit, series-SSHI and parallel-SSHI are compared in experiments to find which one is the best suit for the real-time-footstep energy harvester. Experimental results show that the use of parallel-SSHI circuit interface produces 85% more power than the SEH counterpart, while the use of series-SSHI circuit demonstrates the similar performance in comparison to the SEH interface. The reasons for such a huge efficiency improvement by using the parallel-SSHI interface are detailed in this paper.