This paper presents the stiffness characteristics of a three-prismatic-universal–universal (3-PUU) translational parallel kinematic machine (PKM). The stiffness matrix is derived intuitively based upon an alternative approach considering actuations and constraints, and the compliances subject to both actuators and legs are involved in the stiffness model. The stiffness performance of the manipu...

Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness-based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel res...

This paper describes a multi-fingered haptic palpation method using stiffness feedback actuators for simulating tissue palpation procedures in traditional and robot-assisted minimally invasive surgery. Soft tissue stiffness is simulated by changing the stiffness property of the actuator during palpation. For the first time, granular jamming and pneumatic air actuation are combined together to r...

This paper investigates the stiffness characteristics of spherical parallel manipulators. By virtue of singular value decomposition, the 6×6 dimensionally inhomogeneous Cartesian stiffness matrix is transformed into two homogeneous ones, i.e., the rotational and translational stiffness matrices. The decomposed singular values and the corresponding vectors indicate the directions of high/weak st...

purpose: core stability and leg stiffness are two determinant mechanisms in athletic performance and risk injury. this study aimed to investigate the gender differences and relationship of these two factors in athletes. methods: in this cross-sectional study, core stability and leg stiffness of 12 male and 12 female iranian squash players at national level were examined utilizing mcgill’s test ...

The stiffness of a parallel manipulator is not only concerned with its detailed structure but also affected by the allocation scheme of actuators. Even though the precise values of stiffness cannot be derived since the link structure is not definitive at the stage of mechanism design, the effect of the allocation of actuators on the mechanism stiffness can be qualitatively evaluated in order to...

BACKGROUND The purpose of this study was to determine the relative contribution of fibrosis-mediated and myofibril-mediated stiffness in rats with mild and severe right ventricular (RV) dysfunction. METHODS AND RESULTS By performing pulmonary artery banding of different diameters for 7 weeks, mild RV dysfunction (Ø=0.6 mm) and severe RV dysfunction (Ø=0.5 mm) were induced in rats. The relativ...

Cells from many different tissues sense the stiffness and spatial patterning of their microenvironment to modulate their shape and cortical stiffness. It is currently unknown how substrate stiffness, cell shape, and cell stiffness modulate or interact with one another. Here, we use microcontact printing and microfabricated arrays of elastomeric posts to independently and simultaneously control ...

The mechanical stiffness of running-specific prostheses likely affects the functional abilities of athletes with leg amputations. However, each prosthetic manufacturer recommends prostheses based on subjective stiffness categories rather than performance based metrics. The actual mechanical stiffness values of running-specific prostheses (i.e. kN/m) are unknown. Consequently, we sought to chara...

When humans hop or run on different surfaces, they adjust their effective leg stiffness to offset changes in surface stiffness. As a result, the overall stiffness of the leg-surface series combination remains independent of surface stiffness. The purpose of this study was to determine whether humans make a similar adjustment when springs are placed in parallel with the leg via a lower limb orth...