Determination of the closed-form workspace area expression and dimensional optimization of planar parallel manipulators

Optimization is an important step in the design and development of a planar parallel manipulator. For optimization processes, workspace analysis is a crucial and preliminary objective. Generally, the workspace analysis for such manipulators is carried out using a non-dimensional approach. For planar parallel manipulators of two degrees of freedom (2-DOF), a non-dimensional workspace analysis is very advantageous. However, it becomes very difficult in the case of 3-DOF and higher DOF manipulators because of the complex shape of the workspace. In this study, the workspace shape is classified as a function of the geometric parameters, and the closed-form area expressions are derived for a constant orientation workspace of a three revolute–revolute–revolute (3-RRR) planar manipulator. The approach is also shown to be feasible for different orientations of a mobile platform. An optimization procedure for the design of planar 3-RRR manipulators is proposed for a prescribed workspace area. It is observed that the closed-form area expression for all the possible shapes of the workspace provides a larger solution space, which is further optimized considering singularity, mass of the manipulator, and a force transmission index.

Analysis of kinematics and statics for a novel 6-DoF parallel mechanism with three planar mechanism limbs

A novel 6-degree-of-freedom (DoF) parallel manipulator with three planar mechanism limbs is proposed and its kinematics and statics are analyzed systematically. First, the characteristics of the proposed manipulator are analyzed and the degree of freedom is calculated. Second, the formulae for solving the displacement, the velocity, and the acceleration are derived. Third, an analytic example is given for solving the kinematics and statics of this manipulator, and the analytic solved results are analyzed and verified by the simulation mechanism. Finally, a workspace is constructed and analyzed based on a comparison between the proposed manipulator and another 6-DoF parallel manipulator.

Kinematics analysis and singularities of novel decoupled parallel manipulators with simplified architecture

Parallel manipulators (PMs) with decoupled kinematics can be obtained by combining a translational PM (TPM) with a spherical PM (SPM) either in multiplatform architectures or in integrated more-complex architectures. Some of the latter type are inspired by the 6–4 fully parallel manipulator (6–4 FPM), whereas others of the same type are deduced by suitably combining TPMs' limbs and SPMs' limbs into more cumbersome limbs which contain more than one actuated joint. The decoupled PMs (DPMs) presented here pursue an intermediate concept between the last two which keeps all the actuators on or near to the base in a simplified architecture with only three limbs. These features preserve the lightness of the mobile masses, together with the associated good-dynamic performances, and reduce the limitations on the workspace due to the eliminated limbs and to possible limb interferences. The finite and instantaneous kinematics of the proposed DPMs is studied, thus proving the practical implementation of the proposal.

An overview of kinematic and calibration models using internal/external sensors or constraints to improve the behavior of spatial parallel mechanisms

This paper presents an overview of the literature on kinematic and calibration models of parallel mechanisms, the influence of sensors in the mechanism accuracy and parallel mechanisms used as sensors. The most relevant classifications to obtain and solve kinematic models and to identify geometric and non-geometric parameters in the calibration of parallel robots are discussed, examining the advantages and disadvantages of each method, presenting new trends and identifying unsolved problems. This overview tries to answer and show the solutions developed by the most up-to-date research to some of the most frequent questions that appear in the modelling of a parallel mechanism, such as how to measure, the number of sensors and necessary configurations, the type and influence of errors or the number of necessary parameters.

A worm-inspired new spatial hyper-redundant manipulator

In this work a novel spatial hyper-redundant manipulator inspired in the motions of the worms is introduced. The displacement analysis is presented in a semi-closed form solution, whereas the velocity and acceleration analyses are carried out by means of the theory of screws. Among typical applications of most hyper-redundant manipulators, interesting biomechanical applications such as the simulation of the motion of the spine are available for this new artificial worm.

Kinematic analysis of partially decoupled fully-parallel manipulators of type 5-5 and 4-5

This paper presents two fully parallel manipulators of type 5-5 and 4-5 with special geometry that makes them partially decoupled. The direct kinematic analysis and the singularity study of these manipulators are addressed, which show that the motion of the manipulators can be easily controlled. Computational considerations are reported, which demonstrate that the algorithms proposed for the direct kinematic analysis are very efficient. Moreover, a comparison with other special geometries illustrates that the proposed manipulators are valuable solutions and represent a good compromise between an efficient controllability and a simple practical feasibility.