Abstract
Abstract. This extensive review paper, which involves 204 papers, discusses comprehensively a number of performance indices that are instrumental in the design of parallel kinematics manipulators. These indices measure the workspace as well as its quality including the distance to singularity, dexterity, manipulability, force transmission, accuracy, stiffness, and dynamic performance. After being classified, the indices are discussed in terms of some important aspects including definition, physical meaning soundness, dependency, consistency, scope of applicability, and computation cost. For the sake of completeness, some key mathematical expressions of the indices are provided.
Highlights
Parallel kinematics manipulators (PKMs) have been extensively studied in the last two decades with a few of them deployed into commercial market for demanding tasks such as high-speed pick-and-place and aircraft component machining as they offer high dynamics, high agility, high payload-to-weight ratio, distributed joint errors, and simple inverse kinematics
Yuefa and Tsai (2016) classified singularities for lower mobility PKMs into three types: (i) limb singularity which occurs when the limb twist system degenerates and the moving platform loses one or more degrees of freedom (DOF), (ii) platform singularity which occurs when the overall wrench system of the moving platform degenerates and the moving platform gains one or more DOF, and (iii) actuation singularity which occurs when inappropriate joints are chosen as the active joints and the moving platform still possesses certain DOF all the actuators are locked
It should be mentioned that, after realizing that all previously proposed transmission indices only evaluate the relation between input and output powers, Briot et al (2013) investigated a complementary method to evaluate the reactions at passive joints due to an external wrench, which are typically high in the singularity neighbourhood and can cause breakdown of a mechanism
Summary
Parallel kinematics manipulators (PKMs) have been extensively studied in the last two decades with a few of them deployed into commercial market for demanding tasks such as high-speed pick-and-place and aircraft component machining as they offer high dynamics, high agility, high payload-to-weight ratio, distributed joint errors, and simple inverse kinematics. If the local performance index cannot be expressed analytically in terms of the workspace, Eq (2) can be used to perform discrete averaging In the latter case, the number of points N being evaluated may affect the accuracy of the averaging. Zhang et al (2014) proposed the use of a global performance index which evaluates the distribution characteristics of a performance index, including central tendency, dispersion, and shape. This global index integrates four performance indices: global average index (GAI), global volatility index (GVI), global skewness index (GSI), and global kurtosis index (GKI). As a result of the more completeness of this paper, the number of relevant references are significantly increased
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