Continuum robots are kinematically redundant and their dynamic models are highly nonlinear. This study aims to overcome this difficulty by presenting a more practical dynamic model of a certain class of continuum robots called cable-driven continuum robot (CDCR). Firstly, the structural design of a CDCR with two rotational degrees of freedom (DOF) is introduced. Then, the kinematic models are derived according to the constant curvature assumption. Considering the complexity of the kinetic energy expression, it has been approximated by the well-known Taylor expansions. This case corresponds to weak bending angles within the specified bending angle range of the robot. On the other hand, due to the low weight of the CDCR components, the gravitational energy effects can be neglected compared to those stemmed from the elastic energy. Thereafter, the corresponding dynamic model is established using Euler-Lagrange method. Static and dynamic models have been illustrated by examples. This analysis and dynamic model development have been compared with the existing scientific literature. The obtained results shown that the consistency and the efficiency of accuracy for real-time have been carried out. However, the dynamic modeling of CDCR with more than 2-DOF leads to a more complex mathematical expression, and cannot be simplified by adopting the similar assumptions and methodology used in the case of 2-DOF.
In this paper, we will perform a comparison between two approaches of dimensional synthesis of parallel robots. The first one concerns the single-objective optimization approach; in this case, the dimensional synthesis is expressed by taking into account only one performance criterion but enables to get a final solution if it exists. The second one concerns the multi-objective optimization approach; it enables to simultaneously take into account several performance criteria. However, thisRidha Kelaiaia approach appears to provide a set of solutions instead of a single expected final solution which should directly enable to carry out the structural synthesis. In fact, the search of a single final solution is postponed to a further step where the designers have to impose and/or restrict certain parameters. And we will establish if it is really necessary to make a multi-objective optimization approach or if a singleobjective is sufficient to reach the objectives set in the specifications (user requirements). A discussion is proposed concerning the arising questions related to each approach and leading to the optimal dimensional synthesis. The PAR2 robot with two degree-of-freedom is used to exemplify the analysis and the comparison of the two approaches. The proposed comparison can be applied to any classes of parallel robots.
Continuum robot modeling is a research topic that focuses on ways to develop kinematic models while respecting some kinematics specificity as well as mechanical properties of such class of robots. The purpose of this article is to present a new alternative approach for solving inverse kinematic models for multi-sections of continuum manipulators. To achieve this work, it is assumed that each constitutive section is curved in a circular arc shape with an inextensible central structure axis. At first, the article presents a solution of an inverse kinematic model for one bending section and details some adopted methodologies, based on the identical inverse kinematic model of parallel robots, used for computation of the links’ length. The latter allows concatenating between multiple platforms to realize a bending section. The inverse kinematic model of the multi-section manipulator is then developed using a modular concept where the endpoint coordinates of each bending section are determined using a metaheuristic method. Finally, to validate the proposed approach, some simulation and experimental studies have been carried out on the Compact Bionic Handling Arm. From this investigation, it was found that the multiple test results show the ability of the developed metaheuristic approach to avoid obstacles and to adopt a real-time implementation with multi-section configuration. On the other hand, this type of concept can enable to model all continuum robots with multiple bending sections.
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