A design of 2-DoFs spherical parallel manipulator with adjustable workspace

The research subject of this paper is spherical 2-DOF Parallel manipulator with actuation redundancy, Mechanical dimension optimum design method of the manipulator has been presented, which considered both global performance index and local performance index, we can obtain relative synthetically optimization mechanical dimension by the method. We finished the optimum program by virtue of software VB and Matlab, and realized dimension optimum design of spherical 2-DOF parallel manipulator with actuation redundancy considered different performance index on different application occasion.

Design and kinematic analysis of a 3-RRR spherical parallel manipulator reconfigured with four–bar linkages

Spherical parallel manipulators (SPMs) are used to orient a tool in the space with three degrees of freedom exploiting the strengths of a multi-limb architecture. On the other hand, the performance of parallel kinematics machines (PKMs) is often affected by the occurrence of different kinds of singular configurations. The paper aims at characterizing a class of SPMs for which all singularities come to coincide and a single expression is able to describe all the singular configurations of the machines. The study is focused on a class of SPMs with 3-RFR topology (Revolute-Planar-Revolute pairs for each of the three limbs) addressing the mobility and singularity analysis by means of polynomial decomposition and screw theory. The neatness of the equations that are worked out, expressed in a robust formulation based on rotation invariants, allows a straightforward planning of singularity free tasks and simplifies the synthesis of dexterous machines.

This work deals with the forward and inverse kinematic analysis of a coaxial spherical parallel manipulator (SPM) by using the Euler angles representation for the mobile’s platform orientation. A unique solution for the inverse and forward kinematic problem which corresponds with the assembly mode of a physical prototype is considered. The screw theory is then used to derive the Jacobian matrix as well as to carry out the velocity analysis. Finally, the solutions from both analysis are compared with numerical results obtained by simulation using ADAMS View software for different position and velocity trajectories, showing the validity of the obtained results.

In this paper, a novel 3-degree-of-freedom (DOF) parallel manipulator that can perform three rotations around the remote centre is presented. The theory of screws and reciprocal screws is employed for the analysis of the geometric conditions. In particular, using circular guide to instead of R joints, so that has the advantage of enabling continuous 360° revolute around Z-axis. The inverse kinematics of mechanism is given and the workspace has a good performance. To compare with the machine constructed with traditional joints, it has the advantage of high rigidity and precision.

This article deals with the optimum design of 3-RRR planar parallel manipulators. Based on the kinematic model and Jacobian matrix, the global conditioning index, global velocity index and global stiffness index of 3-RRR parallel manipulators are investigated. The corresponding atlases are represented graphically in the established design space, and the geometrical parameters without dimension are determined. An example is presented to achieve the optimum dimensional parameter based on the optimum non-dimensional result. The result of this article is not only useful for the development of 3-RRR planar parallel manipulators, but also helpful for the optimum design of other parallel manipulators.

SUMMARYIn this paper, we propose a unique, 3 degree-of-freedom (DOF) parallel wrist. Specifically, an over-constrained spherical 3-DOF parallel mechanism is presented and the modified structure, which avoids the redundant constraints, is also introduced.

Optimum design of 3-DOF spherical parallel manipulators with respect to the conditioning and stiffness indices

This work presents the design of a reconfigurable planar parallel manipulator (RPPM). The RPPM is designed to act as a testbed manipulator for theories on redundant actuation of parallel manipulators and can reconfigure into three different revolute‐jointed mechanism types: a 2‐branch 2‐DOF (degree‐of‐freedom) 5‐bar mechanism; a 2‐branch 3‐DOF 6‐bar mechanism; and a 3‐branch 3‐DOF 8‐bar mechanism. The design of the RPPM allows for any shoulder or elbow joint to be actuated. In this work, the criteria and constraints of the design are presented. The final design of the RPPM is shown, followed by a discussion of the final design and how it relates to the initial design criteria and constraints. © 2004 Wiley Periodicals, Inc.

SUMMARYThis paper deals with the design of 3-legged distributed-compliance XYZ compliant parallel manipulators (CPMs) with minimised parasitic rotations, based on the kinematically decoupled 3-PPPRR (P: prismatic joint, and R: revolute joint) and 3-PPPR translational parallel mechanisms (TPMs). The designs are firstly proposed using the kinematic substitution approach, with the help of the stiffness center (SC) overlapping based approach. This is done by an appropriate embedded arrangement so that all of the SCs associated with the passive compliant modules overlap at the point where all of the input forces applied at the input stages intersect. Kinematostatic modelling and characteristic analysis are then carried out for the proposed large-range 3-PPPRR XYZ CPM with overlapping SCs. The results from finite element analysis (FEA) are compared to the characteristics found for the developed analytical models, as are experimental testing results (primary motion) from the prototyped 3-PPPRR XYZ CPM with overlapping SCs. Finally, issues on large-range motion and dynamics of such designs are discussed, as are possible improvements of the actuated compliant P joint. It is shown that the potential merits of the designs presented here include a) minimised parasitic rotations by only using three identical compliant legs; b) compact configurations and small size due to the use of embedded designs; c) approximately kinematostatically decoupled designs capable of easy controls; and d) monolithic fabrication for each leg using existing planar manufacturing technologies such as electric discharge machining (EDM).

This paper presents a new method for the optimum design of parallel manipulators by taking both the kinematics and dynamic characteristics into account. The optimum design of a 3-DOF 4-RRR planar parallel manipulator with actuation redundancy is investigated to demonstrate the method. The kinematic performance indices such as the conditioning index, the velocity index, and workspace area are analyzed. Further, the dynamic dexterity, which is used to evaluate the dynamic characteristics, is investigated. The corresponding atlases are represented graphically in the established design space. Based on these atlases, the geometrical parameters without dimension are determined. Then the optimum dimensional parameters are achieved based on the optimum non-dimensional result. By using the method proposed in this paper, the designer can obtain the optimum result with respect to both kinematic performance indices and dynamic performance indices. Since the dynamic performance is considered in the process of optimum design by using the method proposed in this paper, it is expected to realize the high dynamics of parallel manipulators.

In this article‚ a new approach is presented to determine the various shapes of workspaces of 5 bar symmetric planar parallel manipulators. Here the shape of the workspace is determined by the number of ways the workspaces of the two serial manipulators intersect with each other. Geometric conditions are established in each case and area of each shape of workspace is determined in closed form. Singularity is another important consideration in the design of parallel manipulators. In this paper, an approach is presented to go through the singularity points using an automatic selective actuation mechanism. A prototype 5-bar planar manipulator is fabricated along with an automatic selective actuation mechanism demonstrating the manipulator going through the singularity points.

A new 3T1R parallel manipulator (PM) 2PPaRR-2PPaRU with rotational pitch motion is proposed in this paper. In such a mechanism, there are four limbs connected to the moving platform (MP) through several revolute joints and universal joints, and all actuated joints are prismatic joints with an axis along a vertical direction. Mobility and motion characteristics are verified by constraint screw theory. The inverse kinematic solutions and the singularity configurations are derived through kinematic analysis. Next, the workspace analysis and the connection between [Formula: see text] and the volume of the reachable workspace are performed. The local motion/force transmission index is selected to evaluate the local transmission performance of 2PPaRR-2PPaRU PM. Finally, the global motion/force transmission index and the volume of reachable workspace are considered simultaneously to optimize the structural parameters. The 2PPaRR-2PPaRU PM with improved local transmission performance and reachable workspace has been achieved after optimization.

The concept of a medical parallel manipulator device applicable to chest compressions in the process of cardiopulmonary resuscitation (CPR) is proposed in this paper. According to the requirements of CPR action, a new translational parallel manipulator (TPM) is designed for such applications. And a thorough kinematic analysis and optimization are performed for the designed TPM. The mobility of the manipulator is analyzed using screw theory. The inverse kinematics and forward kinematics problems' are solved in details and the singularities are investigated afterwards. Utilizing a numerical search method, the manipulator workspace has been generated with the consideration of factors from medical aspects. The architectural optimization has been carried out based on a mixed performance being a weighted sum of global dexterity index and space utility ratio index, and the simulation results are presented. The research work provides a sound base for the development of a medical manipulator to assist in CPR operation.

This paper presents the design of a 6-degreeof-freedom (DOF) hybrid cable-driven parallel manipulator (HCDPM) with a central elastic rod. HCDPM is integrated with a multi-rotor unmanned aerial vehicle (UAV) for the contact inspection of floating offshore wind turbines (FOWTs) by delivering a sensor. Flexible cables allow the end-effector (EE) to actively adapt to the target’s movements during approach. Once the EE attaches to the target, the central rod detaches from the EE and the cables slacken. This setup enables the sensor to directly detect signals from the FOWTs without being influenced by the UAV’s movements and vibrations, thanks to the unidirectional tension transmission in the cables. Finally, the accuracy of the modeling and the significance of introducing the central rod were validated through co-simulation and workspace calculation. The results indicate that the inclusion of the rod significantly improves the model’s precision, design’s stiffness, and the workspace.