The structure of the cell mechanical model. The cell model contains the membrane networks, the internal cytoskeleton, ACPs, motors and their functions, including the binding/unbinding and the folding/unfolding of the proteins, the polymerization/depolymerization of cytoskeletal filaments, and the walk of motors.

A novel spatial parallel manipulator designed to assemble diagnostic instruments in SG-III is introduced in this paper. Firstly, resorting to screw theory, mobility analysis of this manipulator is investigated. Then the inverse kinematics problem is determined by the method of RPY transformation, with the singularity analyzed. As a key issue in parallel manipulators, it is more difficult to solve the forward kinematics problem, since it is highly nonlinear and coupled. In this work, three different approaches are presented to deal with this issue, which include the back propagation neural network, the simplified ant colony optimization and the proposed improved Newton iterative method. Simulation of each approach is conducted, and their merits and demerits are compared in detail. It is concluded that the improved Newton iterative method which can provide good initial iteration values possesses the best performance to estimate the nonlinear forward kinematic mapping of the considered parallel manipulator

This work investigates the stiffness characteristics of a planar parallel manipulator with variable platforms. The stiffness model is established with shape variables of the base and mobile platforms based on the Jacobian matrix. By virtue of a nondimensionalization of the inhomogeneous stiffness matrix, two homogeneous submatrices are obtained. Upon which, two kinds of performance indices are derived to evaluate the manipulator’s stiffness behaviors, one for translation and the other for rotation. Stiffness performance of the considered manipulator with three types of platforms, namely variable base platform, variable mobile platform and both variable base and mobile platforms, is analyzed. To validate the stiffness models, the established analytical models are compared with the FEA based evaluations. In order to find the configurations with the best global stiffness performance, stiffness optimization with consideration of shape variables is conducted with the particle swarm optimization algorithm. Finally, a case study of platforms’ shape changing in stiffness adjustment is presented.

Singularity is an inherent property of robotic manipulators. A manipulator becomes singular when it gains or losses degrees of freedom at a particular configuration. In this work, a type of singularities caused by special shapes of platforms, either the mobile or the base platform, is addressed. This type of singularities pertains to the architecture singularity, but associated only with special shape designs of base and mobile platforms and spans in the whole workspace, which is referred as shape singularity. The paper provides formulations of shape singularity. The geometry and algebra properties of shape singularity are analyzed. Three examples of shape singularity identification for parallel mechanisms with prismatic joints are included, one for 3-DOF planar mechanisms, the others for 3-DOF and 6-DOF spatial mechanisms. The application of shape singularity in adjustable compliance mechanism design is illustrated.