Leg Mechanism Research Articles

An Avian-Inspired Passive Mechanism for Quadrotor Perching

Flying robots capable of perch-and-stare are desirable for reconnaissance missions. Inspired by an adaptation that enables songbirds to sleep in trees without active muscle control, the research presented herein details the design for a passive mechanism that enables a rotorcraft to perch reminiscent of a bird perching on a tree branch. Perching is accomplished through the integration of a compliant, underactuated gripping foot and a collapsing leg mechanism that converts rotorcraft weight into tendon tension in order to passively actuate the foot. Analysis of mechanism behavior is presented, and stability tests were performed to characterize the ability of the system to reject disturbances. The results indicate that it is possible to passively perch a rotorcraft on multiple surfaces and support reasonable environmental disturbances. The analysis in this paper can enable passive perching design optimization in vertical take-off and landing systems.

로봇 발의 접촉 반발력이 무릎 및 힙 관절에 미치는 영향

본 논문에서는 컴플라이언스 특성의 발을 갖는 이족 로봇의 다리 메커니즘을 제시한 후, 이족 로봇을 위한 전형적인 보행 패턴에서 발의 접촉 반발력과 이것이 무릎과 힙 관절에 미치는 영향을 고찰하고자 한다. 이러한 분석은 보행 로봇이 걸음 동작을 수행할때, 발의 물리적인 접촉력의 영향을 파악하는데 있어서 유용하고, 다리 메커니즘의 관절 사양을 결정하는데 활용될 수 있다. 결과적으로, 로봇 발 메커니즘의 컴플라이언스 특성이 발의 접촉 반발력에 의해 영향을 받는 보행 다리 관절의토오크 특성을 완화시키는데 기여할 수 있음을 보인다. This paper presents a model of bipedal leg mechanism with a compliant foot, and the contact repulsion of the foot for a typical walking pattern and its influence on the knee and hip joints of the leg will be analyzed. This analysis is useful for us to figure out the physical impact of the foot when a walking robot takes a step. Also it can be applied to determine the joint specification of the leg mechanism. As a result, it is shown that the compliance characteristics of a robotic foot can contribute to alleviate the joint torques of the leg affected by the contact repulsion of the foot.

Analysis of Static and Optimization of Structural Parameters for a Novel Leg Mechanism

In order to increase wosrkspace and carrying capacity of leg mechanism and improve popularity and adaptability of leg mechanism, a novel mechanism is proposed which has three branches of 6-DOF, which used 3-UPS parallel mechanism as the prototype of the mechanism. The static performance of the leg mechanism is analyzed and the structure parameters are designed. First, the static transmission equation of the leg mechanism is established by using the principle of virtual works which simplifies the calculation process of the leg mechanism. Further, the static performance evaluation index and the global torque performance evaluation index are defined, and the performance atlas of the static performance evaluation index is plotted at the work spaces of the leg mechanism. Moreover, by using of the space model theory, the structural dimensions parameters are optimized of the leg mechanism. Finally, using a set of optimal structural dimensions parameters and the virtual prototype of leg mechanism is designed. The research provides a theoretical basis for further investigation on leg mechanism.

Design of a slider-crank leg mechanism for mobile hopping robotic platforms

Legged locomotion has been widely researched due to its effectiveness in overcoming uneven terrains. Due to previous efforts there has been much progress in achieving dynamic gait stability and as the next step, mimicking the high speed and efficiency observed in animals has become a research interest. The main barrier in developing such a robotic platform is the limitation in the power efficiency of the actuator: the use of pneumatic actuators produce sufficient power but are heavy and big; electronic motors can be compact but are disadvantageous in producing sudden impact from stall which is required for high speed legged locomotion. As a new attempt in this paper we suggest a new leg design for a mobile robot which uses the slider-crank mechanism to convert the continuous motor rotation into piston motion which is used to impact the ground. We believe this new mechanism will have advantage over conventional leg mechanism designs using electronic motors since it uses the continuous motion of the motor instead of sudden rotation movements from stall state which is not ideal to draw out maximum working condition from an electronic motor. In order to control impact timing from the periodic motion of the piston a mechanical passive clutch trigger mechanism was developed. Dynamic analysis was performed to determine the optimal position for the mechanical switch position of the clutch trigger mechanism, and the results were verified through simulation and experiment. Development of a legged locomotion with two degrees of freedom, slider-crank mechanism for impact and additional actuation for swing motion, is proposed for future work.

1A1-B10 二関節筋パワーアシストスーツの研究 : 第2報 重量物保持モデルの開発(医療ロボティクス・メカトロニクス(1))

In this study, we develop a power assist suit adapted to bi-articular muscles model. Before now we have already developed the leg mechanism of power assist suit adapted to bi-articular muscles model using parallel links. The leg mechanism of power assist suit adapted to bi-articular muscles model has high torque and safety from a series of experimental results. Therefore, we improve Power Assist Suit based on conventional leg mechanism confirmed the good efficiency. Furthermore the new model is able to hold 10kgf weight as a result of mechanical improvement. In addition, we consider distinction method by Neural network with electromyography control.

A Passive Dynamic Walking Model Based on Knee-Bend Behaviour: Stability and Adaptability for Walking down Steep Slopes

This paper presents a passive dynamic walking model based on knee-bend behaviour, which is inspired by the way human beings walk. The length and mass parameters of human beings are used in the walking model. The knee-bend mechanism of the stance leg is designed in the phase between knee-strike and heel-strike. q* which is the angular difference of the stance leg between the two events, knee-strike and knee-bend, is adjusted in order to find a stable walking motion. The results show that the stable periodic walking motion on a slope of r <0.4 can be found by adjusting q*. Furthermore, with a particular q* in the range of 0.12< q*<0.18, the walker can walk down more steps before falling down on an arbitrary slope. The walking motion is more stable and adaptable than the conventional walking motion, especially for steep slopes.

Design and Analysis of a Low Cost And Easy Operated Leg Mechanism For A Walking Robot

In this paper, several walking machines and robots have been conceived, designed and built in the last twenty years to open new fields of application. Compared to wheeled vehicles walking machines show the advantage that they can act in highly unstructured terrain without having prepared this terrain in advance by streets or rails. Legged robots cross obstacles more easily; depend less on the surface conditions and quality and, in general, exhibit better adaptability. In this paper a numerical and experimental analyses of a pantograph-leg are presented. In particular, a suitable model of the leg has been analyzed and Kinematics and Dynamics have been solved. A parametric study has been also carried out in order to investigate the influence of some basic design parameters on its motion capabilities.

Work Analysis of Compliant Leg Mechanisms for Bipedal Walking Robots

In this study, we analyse the work of bipedal walking robots with compliant feet. For this purpose, a walking model of bipedal robots with compliant feet is considered. The ligamentous structure of the human foot is used for the compliant feet mechanisms of the bipedal robot considered herein. A work principle is used for determining the corresponding work at the joint space of the compliant legs according to the reaction force which is propagated from the foot space. The usefulness of the work analysis is demonstrated through exemplary simulations. Consequently, it is shown that the work analysis can be used for evaluating the fatigue of the bipedal robot accumulated by the physical walking impact between the supporting foot and the contact surface. Furthermore, comfortable walking by means of footgear with a compliance is addressed.

1A1-P10 ザトウグモ型6足歩行ロボットASURA Iの開発 : 第4報:脚機構の解析と基本動作実験(脚移動ロボット(1))

1A1-P10 ザトウグモ型6足歩行ロボットASURA Iの開発 : 第4報:脚機構の解析と基本動作実験(脚移動ロボット(1))

DESIGN AND OPTIMIZATION OF AN EIGHT-BAR LEGGED WALKING MECHANISM IMITATING A KINETIC SCULPTURE, “WIND BEAST”

Legged off-road vehicles exhibit better mobility while moving on rough terrain. Development of legged mechanisms represents a challenging problem and has attracted significant attention from both artists and engineers. In this paper, we present the design of a single-degree-of-freedom legged walking mechanism using the mechanism design theory and optimization to imitate a well-known kinetic sculpture, a Wind Beast. The optimization is set up to: i) minimize the energy input and ii) maximize the stride length. The optimization is based on the dynamic force analysis. A prototype of the optimized walking mechanism with 6 legs was built to demonstrate its smooth motion. The success in designing a legged mechanism capable of imitating the well-known kinetic sculpture using the engineering design theories is a small step bridging the gap between art and engineering.

Operation analysis of a Chebyshev-Pantograph leg mechanism for a single DOF biped robot

In this paper, operation analysis of a Chebyshev-Pantograph leg mechanism is presented for a single degree of freedom (DOF) biped robot. The proposed leg mechanism is composed of a Chebyshev four-bar linkage and a pantograph mechanism. In contrast to general fully actuated anthropomorphic leg mechanisms, the proposed leg mechanism has peculiar features like compactness, low-cost, and easy-operation. Kinematic equations of the proposed leg mechanism are formulated for a computer oriented simulation. Simulation results show the operation performance of the proposed leg mechanism with suitable characteristics. A parametric study has been carried out to evaluate the operation performance as function of design parameters. A prototype of a single DOF biped robot equipped with two proposed leg mechanisms has been built at LARM (Laboratory of Robotics and Mechatronics). Experimental test shows practical feasible walking ability of the prototype, as well as drawbacks are discussed for the mechanical design.

Advanced age affects the individual leg mechanics of level, uphill, and downhill walking

Advanced age brings biomechanical changes that may limit the uphill and/or downhill walking ability of old adults. Here, we investigated how advanced age alters individual leg mechanics during level, uphill, and downhill walking. We hypothesized that, compared to young adults, old adults would exhibit: (1) reduced trailing leg propulsive ground reaction forces (GRFs) and positive work rates during uphill walking, and (2) reduced leading leg braking ground reaction forces and negative work rates during downhill walking. We calculated the individual leg mechanical work performed by 10 old (mean±SD, age: 72±5 yrs) and 11 young (age: 26±5 yrs) adults walking at 1.25m/s on a dual-belt force-measuring treadmill at seven grades (0° and ±3°, ±6°, ±9°). As hypothesized, old adults exhibited significantly reduced propulsive GRFs (e.g., −21% at +9°) and average trailing leg positive work rates (e.g., −26% at +9°) compared to young adults during both level and uphill walking. Old adults compensated by performing greater positive work than young adults during the subsequent single support phase. In contrast, we reject our second hypothesis. We found no differences in braking GRFs or negative work rates between old and young adults. However, old adults exhibited significantly reduced second peak perpendicular GRFs during downhill walking compared to young adults. Our findings most notably identify how advanced age may impair uphill walking ability and thus independence and quality of life.

How to sprain your ankle – a biomechanical case report of an inversion trauma

In order to develop preventive measures against lateral ankle sprains, it is essential to have a detailed understanding of the injury mechanism. Under laboratory experimental conditions the examination of the joint load has to be restricted with clear margins of safety. However, in the present case one athlete sprained his ankle while performing a run-and-cut movement during a biomechanical research experiment. 3D kinematics, kinetics, and muscle activity of the lower limb were recorded and compared to 16 previously performed trials. Motion patterns of global pelvis orientation, hip flexion, and knee flexion in the sprain trail deviated from the reference trials already early in the preparatory phase before ground contact. During ground contact, the ankle was rapidly plantar flexed (up to 1240°/s), inverted (up to 1290°/s) and internally rotated (up to 580°/s) reaching its maximum displacement within the first 150ms after heel strike. Rapid neuromuscular activation bursts of the m. tibialis anterior and the m. peroneus longus started 40–45ms after ground contact and overshot the activation profile of the reference trials with peak activation at 62ms and 74ms respectively. Therefore, it may be suggested that neuromuscular reflexes played an important role in joint control during the critical phase of excessive ankle displacement.The results of this case report clearly indicate that (a) upper leg mechanics, (b) pre-landing adjustments, and (c) neuromuscular contribution have to be considered in the mechanism of lateral ankle sprains.

Mathematical Simulation of Leg's a 5-Dof a Biped Robot

This paper aims to present special issues concerning the analysis of mobile robots with kinematic motion effects on the stability study. In the analysis, the authors used inverse kinematics, which enables rapid modelling and identifying solutions as regards the stability of bipedal robots. The symbolic solution for kinematics equations of biped robots is of great importance for the efficient controllability of these robots. In recent years, numerous researches have been done based on simulation of legged mechanism, especially on biped robots simulation and control. The following article focuses on the biped robot simulation and control handle with the aid of mathematical modeling methods (in MATLAB)

Study on Mechanics Structural Synthesis of Six-Legged Walking Robot with Parallel Leg Mechanisms

In order to use the parallel leg mechanisms in the six-legged robot, a six-legged walking robot with parallel leg mechanisms was presented. A six-legged walking robot type synthesis method based on screw theory was proposed. By this method, the paper carried on the structural synthesis of whole robot and the parallel leg mechanisms. 2-UPS&UP mechanism was chosen as the leg mechanism of the six-legged walking robot. 2-UPS&UP mechanism had been proven not to be an instantaneous mechanism by the displacement manifold theory. The specific structure of the six-legged walking robot based on2-UPS&UP mechanism was designed. These studies laid the theoretical foundation for further study of the six-legged walking robot. This type synthesis method could be used for the design of other multi-legged walking robot.

Design and Analysis of a Lower Limb Rehabilitation Robot

The paper present a new lower-limb rehabilitation robot which consists of two mechanical legs with 3 DOF. The length of two mechanical legs and the angle of seat back of the rehabilitation robot can be adjusted over a certain range to fit various patients. The robot can exercise a single joint or multiple joints. It has three training modes: active training, passive training and assist training. In order to evaluate the rehabilitation effect of the robot, all joints were equipped with torque sensors and absolute position encoders. which is very important for the design of the rehabilitation robot. Besides, the rehablitaion traning can combined with sEMG/FES. The robot are installed beside a chair, the patient can sit or lie in the chair, which is more comfortable than standing or suspending. The analysis and experimental results demonstrate that the proposed rehabilitation robot is safe and reliable , the workspace can meets the needs of normal gait.

Mechatronical Approach of Analyzing One DOF Leg Mechanism in Order to Construct a Walking Robot System

A mechatronic integrated approach regarding the modeling, analysis and design of one DOF leg mechanism configuration is presented. This mechanism will be implemented in the structure of a walking robot and its configuration is inspired from Jansens type of walking mechanism. The trajectory shape described by the end point of the leg during a walking cycle is analyzed based upon a 2D model developed in Matlab. A mathematical model that consists in structural analysis and equations regarding three types of kinematic constraints proposed for synthesis process is briefly described.

Multi-functional foot use during running in the zebra-tailed lizard (Callisaurus draconoides)

A diversity of animals that run on solid, level, flat, non-slip surfaces appear to bounce on their legs; elastic elements in the limbs can store and return energy during each step. The mechanics and energetics of running in natural terrain, particularly on surfaces that can yield and flow under stress, is less understood. The zebra-tailed lizard (Callisaurus draconoides), a small desert generalist with a large, elongate, tendinous hind foot, runs rapidly across a variety of natural substrates. We use high-speed video to obtain detailed three-dimensional running kinematics on solid and granular surfaces to reveal how leg, foot and substrate mechanics contribute to its high locomotor performance. Running at ~10 body lengths s(-1) (~1 m s(-1)), the center of mass oscillates like a spring-mass system on both substrates, with only 15% reduction in stride length on the granular surface. On the solid surface, a strut-spring model of the hind limb reveals that the hind foot saves ~40% of the mechanical work needed per step, significant for the lizard's small size. On the granular surface, a penetration force model and hypothesized subsurface foot rotation indicates that the hind foot paddles through fluidized granular medium, and that the energy lost per step during irreversible deformation of the substrate does not differ from the reduction in the mechanical energy of the center of mass. The upper hind leg muscles must perform three times as much mechanical work on the granular surface as on the solid surface to compensate for the greater energy lost within the foot and to the substrate.

Mechanical Design of a Trunk with Redundant and Viscoelastic Joints for Rhythmic Quadruped Locomotion

Passive mechanisms, such as free joints and viscoelastic components, enable natural oscillation of the robot body, which allows rhythmic locomotion with low energy and computational costs. In particular, joint viscoelasticity can be a powerful candidate for changing natural oscillation and so influence the operation performance of locomotion. The present study considers the passive mechanism of a trunk, and investigates the contributions of a trunk mechanism with redundant joints and tunable viscoelasticity to quadruped locomotion. A physical quadruped robot with a trunk mechanism is developed, and the walking performance of this robot for various gait patterns and joint viscoelasticities is investigated. A simulation model is also constructed based on the physical robot, and the contribution of the viscoelasticity to trunk oscillation and the appropriate joint viscoelasticity and number of trunk joints are discussed. Experimental results obtained using the physical robot indicate that the proposed trunk mechanism contributes to successful locomotion as compared to a robot with a rigid trunk and that the velocity is influenced by not only the gait pattern, but also the joint viscoelasticity (i.e., there are appropriate couplings of the joint viscoelasticity and gait pattern). The simulation results indicate that the trunk mechanism requires joint viscoelasticity in order to achieve oscillation and that a greater number of joints having a smaller joint viscoelasticity enables higher velocity. These results suggest that, in addition to the leg mechanism and the controller design, the design of the trunk mechanism is also important.

2A2-V01 負荷感応無段変速機構を膝関節に搭載した脚機構の開発(脚移動ロボット(2))

2A2-V01 負荷感応無段変速機構を膝関節に搭載した脚機構の開発(脚移動ロボット(2))