Probe guides are surgical fixtures that are rigidly attached to bone anchors in order to place a probe at a target with high accuracy (RMS error < 1 mm). Applications include needle biopsy, the placement of electrodes for deep-brain stimulation (DBS), spine surgery, and cochlear implant surgery. Targeting is based on pre-operative images, but targeting errors can arise from three sources: (1) a...

This paper presents an approach for stiffness modelling of the lower mobility parallel manipulators using the generalized Jacobian. The approach can be implemented by two steps:(1) The first order deflection analysis by decomposing twist space of the end-effector into a pair of complementary twist subspaces associated with the permitted and restricted instantaneous motions, (2) The kinestatic a...

Wound dressing biomaterials are increasingly being designed to incorporate bioactive molecules to promote healing, but the impact of matrix mechanical properties on the biology of resident cells orchestrating skin repair and regeneration remains to be fully understood. This study investigated whether tuning the stiffness of a model wound dressing biomaterial could control the behavior of dermal...

We study the spectral properties of the stiffness matrices coming from the Qp Lagrangian FEM approximation of d-dimensional second order elliptic differential problems; here, p = (p1, . . . , pd) ∈ Nd and pj represents the polynomial approximation degree in the j-th direction. After presenting a construction of these matrices, we investigate the conditioning (behavior of the extremal eigenvalue...

The paper focuses on the accuracy improvement of stiffness models for parallel manipulators, which are employed in high-speed precision machining. It is based on the integrated methodology that combines analytical and numerical techniques and deals with multidimensional lumped-parameter models of the links. The latter replace the link flexibility by localized 6-dof virtual springs describing bo...

In this paper, we address the stiffness synthesis problem of variable geometry double planar parallel robots. For a desired stiffness matrix, the free geometrical variables are calculated as a solution of a corresponding polynomial system. Since in practice the set of free geometrical variables might be deficient, the suggested solution addresses also the case where not all stiffness matrix ele...

Matrix variate distributions are are used to quantify uncertainty in the mass, stiffness and damping matrices. The proposed approach is based on the so called Wishart random matrices. The probability density function of the system matrices are derived using the maximum entropy method. It is assumed that the mean of the system matrices are known. A new optimal Wishart distribution is proposed to...

Rigidity matrices for multi-layered media are derived for isotropic and orthotropic layers by a simple direct procedure which brings to light their fundamental mathematical structure. The method was introduced many years ago by the author in the more general context of dynamics and stability of multi-layers under initial stress. Other earlier results are also briefly recalled such as the deriva...