Energy-efficient Locomotion Research Articles

Concept of a Series-Parallel Elastic Actuator for a Powered Transtibial Prosthesis

The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during one stride at the ankle joint when walking at normal cadence and stores/releases 9 J of energy, contributing to energy efficient locomotion. According to Winter, a subject produces on average of 250W peak power at a maximum joint torque of 125 Nm. As a result, powering a prosthesis with traditional servomotors leads to excessive motors and gearboxes at the outer extremities of the legs. Therefore, research prototypes use series elastic actuation (SEA) concepts to reduce the power requirements of the motor. In the paper, it will be shown that SEAs are able to reduce the power of the electric motor, but not the torque. To further decrease the motor size, a novel human-centered actuator concept is developed, which is inspired by the variable recruitment of muscle fibers of a human muscle. We call this concept series-parallel elastic actuation (SPEA), and the actuator consists of multiple parallel springs, each connected to an intermittent mechanism with internal locking and a single motor. As a result, the motor torque requirements can be lowered and the efficiency drastically increased. In the paper, the novel actuation concept is explained, and a comparative study between a stiff motor, an SEA and an SPEA, which all aim at mimicking human ankle behavior, is performed.

Parametrically excited inverted double pendulum and efficient bipedal walking with an upper body

SUMMARYWalking locomotion involves complex movement of total center of mass. Not only the lower body behavior but also the upper body behavior affects the walking characteristics. Therefore, in this paper we derive the principle of parametrically excited inverted double pendulum to consider both lower body and upper body dynamics. We propose one approach to utilize the upper body behavior of the robot for energy efficient bipedal locomotion. In addition, we analyze the property of parametrically excited inverted double pendulum.

Neural control and adaptive neural forward models for insect-like, energy-efficient, and adaptable locomotion of walking machines.

Living creatures, like walking animals, have found fascinating solutions for the problem of locomotion control. Their movements show the impression of elegance including versatile, energy-efficient, and adaptable locomotion. During the last few decades, roboticists have tried to imitate such natural properties with artificial legged locomotion systems by using different approaches including machine learning algorithms, classical engineering control techniques, and biologically-inspired control mechanisms. However, their levels of performance are still far from the natural ones. By contrast, animal locomotion mechanisms seem to largely depend not only on central mechanisms (central pattern generators, CPGs) and sensory feedback (afferent-based control) but also on internal forward models (efference copies). They are used to a different degree in different animals. Generally, CPGs organize basic rhythmic motions which are shaped by sensory feedback while internal models are used for sensory prediction and state estimations. According to this concept, we present here adaptive neural locomotion control consisting of a CPG mechanism with neuromodulation and local leg control mechanisms based on sensory feedback and adaptive neural forward models with efference copies. This neural closed-loop controller enables a walking machine to perform a multitude of different walking patterns including insect-like leg movements and gaits as well as energy-efficient locomotion. In addition, the forward models allow the machine to autonomously adapt its locomotion to deal with a change of terrain, losing of ground contact during stance phase, stepping on or hitting an obstacle during swing phase, leg damage, and even to promote cockroach-like climbing behavior. Thus, the results presented here show that the employed embodied neural closed-loop system can be a powerful way for developing robust and adaptable machines.

유연 다리 구조를 가진 로봇의 에너지 효율적 주행 제어

In this study, we aim to develop energy efficient walking and running robot with compliant leg. So, we propose the energy efficient locomotion control method. And, we experiment the proposed control method applying to the experimental robot with compliant leg. From the experiment, we look at whether the proposed control method can the robot walk and run energy efficiently.

Energy Efficiency of Robot Locomotion Increases Proportional to Weight

The task of producing steady, stable and energy efficient locomotion in legged robots with the ability to walk in unknown terrain have for many years been a big challenge in robotics. This work is focusing on how different robots build from the modular robotic system, LocoKit by Larsen et al. [1], performs compared to animals, and also on the similarities between robots an animals. This work shows, that there in robots exist the same connection between cost of transport and the weight of the robots as is true for animals.

Optimal Control and Design of Bipedal Robots with ComplianceOptimale Steuerung und Auslegung zweibeiniger Laufroboter mit elastischen Gelenken

Abstract The purpose of this paper is to present an interesting area of appplication for modern optimal control techniques in robotics. Optimal control can significantly improve the control of bipedal walking motions, in particular by an optimal exploitation and an appropriate tuning of compliance. Two optimization methods for gait generation and three bipedal robot models are used to highlight three aspects: optimally tuned elastic elements significantly reduce energy consumption for locomotion, produce natural-looking gaits, and enhance the open-loop stability of the gait. It is concluded that optimization of compliance in legged robots is a promising approach towards dynamic, energy-efficient locomotion.

MECHANICAL PROPERTIES OF THE ACHILLES TENDON IN THE PRESENCE OF TENDINOSIS

INTRODUCTION The purpose of this study was to investigate the effect of Achilles tendon pathology on the mechanical characteristics of the Achilles tendon. The functional importance of the Achilles tendon in producing energy efficient locomotion, its high incidence of injuries and its possible relation to joint stability are all compelling factors underscoring the need to investigate mechanical properties of tendons in the presence of pathology. A deeper understanding of the mechanical characteristics of tendons in the presence of pathology has important implications for injury prevention, treatment and optimization of task performance. We hypothesized that individuals with Achilles tendinosis will demonstrate a lower Achilles tendon stiffness as compared to healthy controls.

The force-driven harmonic oscillator model for energy-efficient locomotion in individuals with transtibial amputation

The force-driven harmonic oscillator (FDHO) model states that the driving force is minimum at the resonant period of an oscillator. By manipulating prosthetic mass, this study explored the compromise of resonant periods between the two legs in persons with unilateral traumatic transtibial amputation (TTA) at self-selected walking velocity (SSWV), with an aim to better understand the energy minimization mechanisms of walking. It was hypothesized that (1) SSWV was the most energy-efficient walking velocity (MEWV), (2) the stride period at SSWV ( T s) is a compromise between the resonant periods of the normal leg ( T n) and the prosthetic leg ( T p) when they are dissimilar. Eight subjects completed multiple-speed treadmill walking tests (at 53, 67, 80, 93, and 107 m/min) according to three mass conditions (60%, 80%, and 100% of the normal leg below-knee mass) in a random order. Oxygen consumption and stride period were measured, and SSWV was empirically determined. The MEWV, the speed with minimum energy expenditure per distance traveled, was derived from quadratic regression, and its stride period ( T m) was estimated. A theoretical compromise period ( T v) between T n and T p was predicted by a virtual single pendulum system based on Huygens' Law. Across different mass conditions, comparisons were made among: T s, T m, T v, T n, and T p. Results showed that: (1) T s was significantly different from T m; (2) T s was greater than both T n and T p; (3) no significant difference was found between T m and T n. Implications for amputee rehabilitation in terms of thigh muscle training and prosthesis development were discussed.