In this paper we evaluate the potential of Variable Stiffness Actuation to utilize its inherent joint elasticity and capability to adjust the intrinsic joint stiffness. These abilities make it possible to realize fundamentally different motion control schemes in comparison to intrinsically stiff robots. In this paper we treat the problem of how to generate optimally fast link side velocity at a...

INTRODUCTION It has been shown that walking kinematics remain near to normal after mobile bearing total ankle replacement (TAR). However, no information is available on mechanical joint loading. The purpose of this study was to determine whether mechanical load and 'quasi-stiffness' of the ankle joint after TAR differs from the normal load and stiffness of a healthy ankle joint during walking. ...

Spring-like leg behavior is found in both humans and animals when running. In a spring-mass model, running proves to be self-stable in terms of external perturbations or variations in leg properties (for example, landing angle). However, biological limbs are not made of springs, rather, they consist of segments where spring-like behavior can be localized at the joint level. Here, we use a two-s...

An H∞ synthesis method for control of a flexible joint, with non-linear spring characteristic, is proposed. The first step of the synthesis method is to extend the joint model with an uncertainty description of the stiffness parameter. In the second step, a non-linear optimisation problem, based on nominal performance and robust stability requirements, has to be solved. Using the Lyapunov shapi...

BACKGROUND Gender differences in passive frontal plane knee stiffness may contribute to the increased anterior cruciate ligament injury rate in females. Gender-based stiffness differences have been attributed to anthropometric variations, but little data exist describing this relationship. Furthermore, sex hormone levels appear to influence joint stiffness, but the differential effects of insta...

Serving to improve stability and energy efficiency during locomotion, in nature, animals modulate their leg stiffness to adapt to their terrain. Now incorporated into many locomotive robot designs, such compliance control can enable disturbance rejection and improved transition between changing ground conditions. This paper presents a novel design of a variable stiffness leg utilizing a magneto...

This paper examines the role of grasper compliance and kinematic configuration in environments where object size and location may not be well known. A grasper consisting of a pair of two-link planar fingers with compliant revolute joints was simulated as it passively deflected during contact with a target object. The kinematic configuration and joint stiffness values of the grasper were varied ...

25 Standing balance requires multi-joint coordination between the ankles and hips. We investigated 26 how humans adapt their multi-joint coordination to adjust to various conditions and whether the 27 adaptation differed between healthy young participants and healthy elderly. Balance was disturbed 28 by push/pull rods, applying two continuous and independent force disturbances at the level of t...

BACKGROUND Sex differences may exist in cognitive faculties and neuromuscular strategies for maintaining joint stability. The purpose of this study was to assess whether preparatory and reactive knee stiffening strategies are affected differently in males and females exposed to sex-biased cognitive loads. METHODS 20 male and 20 female volunteers were tested for knee joint stiffness and quadri...

The paper considers a novel modular and intrinsically safe redundant robotic system with biologically inspired actuators (pneumatic artificial muscles and rubber bellows actuators). Similarly to the biological systems, the stiffness of the internal parallel modules, representing 2 DOF joints in the serial robotic chains, is controlled by co-activation of opposing redundant actuator groups in th...