3-DOF Parallel Mechanism Research Articles

Kinematic design of a novel 4-DOF parallel mechanism for turbine blade machining

This paper presents a novel four-degree-of-freedom (4-DOF) partially decoupled parallel mechanism which can generally be used in machining processes, but here, it is particularly designed for turbine blade machining. Forward and inverse kinematic formulations have been derived for proposed mechanism, and using Jacobian matrix has proved that the mechanism has no singularity in its workspace. The workspace has been analyzed using a geometric approach, and the required stroke lengths of mechanism’s actuators for the defined task have been acquired.

Singularity Analysis and Simulation of 3-PRRR Parallel Mechanism

A new 3-DOF parallel mechanism is presented and its kinematics analysis model was established based on the vector method. Based on the speed equations of the mechanism, its singular conditions and singular configurations were analyzed systematically. Moreover, a given mechanism’s singularity was simulated by using cylindrical coordinate search method based on its inverse displacement solutions. The results show that the workspace of mechanism with outset chains is much bigger than mechanism with inset chains. The analysis and simulation on singularity provide a theoretical basis for the dimension synthesis and optimization of this kind of parallel mechanism.

Force/Motion Transmissibility Analysis of Six Degree of Freedom Parallel Mechanisms

Drawing mainly on the concepts of dual space and dual basis in linear algebra and on existing screw theory, this paper presents a novel and systematic approach for the force/motion transmissibility analysis of 6DOF parallel mechanisms. By taking the reciprocal product of a wrench on a twist as a linear functional, the property exhibited by the dual basis allows the formulation of the force/motion transmissibility between the joint space and operation space in an accurate and concise manner. The consistency between the force/motion transmissibility and the minimum singular value of the Jacobian for singularity identification is rigorously proved. This leads to the development of a set of homogeneously dimensionless local and global transmission indices for measuring the closeness to singular configurations as well as for kinematic performance evaluation over a given workspace. A Stewart platform is employed an exemplar to illustrate the effectiveness of the approach.

The Research about Parallel Mechanism Workspace for Quenching

To research 3-DOF parallel mechanism institutions applying to the process of plasma arc surface strengthening, the author establishes an inverse kinematics of institutions mathematical model, and then, basing on its structural constraints and using the boundary finding, draws the workspace. It has guiding significance for the establishment of robotic the plasma arc surface strengthening process.

Structural synthesis for a lower-mobility parallel kinematic machine with swivel hinges

In this paper, a novel parallel kinematic machine is proposed. Its active platform (main supporting spindle) is manufactured with swivel hinges, that is, we substitute the spherical hinge with a swivel hinge. The active platform is also divided into several layers, which alters the characteristics of a single-layer-platform parallel machine. This paper applies a comprehensive structural approach based on position and orientation characteristics (POC). Each single open chain (SOC) is studied independently from the whole mechanism; we also analyse the POC of each kinematic pair. By the method of union, we obtain the POC matrix of the output motion of each link. Based on the verification of the 5-DOF (degree of freedom) parallel kinematic machine, we construct 3-DOF and 4-DOF parallel mechanisms with swivel hinges through the combination and union of different chains, and develop them into a series. • Develop the parallel mechanism with swivel hinges into a series. • Study single open chain based on position and orientation characteristics. • Construct mechanisms of different degrees of freedom with single open chain. • Get and verify the inverse general solution with single open chain for the series.

Design of a novel 3-DoF parallel kinematic mechanism: type synthesis and kinematic optimization

SUMMARYThis paper deals with the design of a three-degree-of-freedom (3-DoF) parallel kinematic mechanism (PKM) with high orientational capability. First, a type synthesis method based on Grassmann line geometry and a line-graph method is proposed, and a novel 3-DoF PKM is derived based on this method. Thereafter, the parasitic motions of the derived mechanism are identified under two different orientation description methods, i.e., Tilt-and-Torsion angles (T&T angles) and Roll-Pitch-Yaw angles (RPY angles), and the kinematic optimization considering the motion/force transmissibility is carried out. On this basis, the orientational capability of the discussed mechanism is investigated, and the high orientational capability is demonstrated. The design of the 3-DoF PKM in this paper is very meaningful to the development of the five-axis machine tools with hybrid architectures. The design methods of type synthesis and kinematic optimization can also be used in the design of other PKMs.

Burnishing Process Using Spherical 5-DOF Hybrid-Type Parallel Mechanism with Force Control

This paper proposes a novel diamond tip burnishing process to improve the integrity of various free-curved surfaces using a spherical 5-Degree-Of-Freedom (5-DOF), hybrid parallelmechanism. The developed parallel mechanism, which has high rigidity and a large workspace, is composed of a spherical 3-DOF parallel mechanism and anXYstage, and is equipped with a burnishing tool on its output link. Using a threedimensional force control system, the parallel mechanism can adjust the thrust force in the burnishing process. The surface roughness and profile of the stainless steel (AISI 316) workpiece, burnished by the proposed method, were evaluated. The surface integrity depended on the values of cross-feed and thrust force, which were controlled by the hybrid parallel mechanism. In addition, the surface roughness improved as cross-feed decreased and thrust force increased. The preliminary surface roughness ofRa= 2.5 µm was improved toRa= 0.25 µm in the burnishing process of the free curved surface, and homogeneous surface integrity was obtained. The results thus suggest that the proposed burnishing method can achieve a highquality surface finish, even on a free curved surface.

Dynamic Formulation and Simplified Model of a Novel 3-DOF Parallel Mechanism with Actuation Redundancy

Dynamics plays an important role in the application of parallel mechanism, which is the key to analyze the dynamic characteristics and achieve high-precision operation. The inverse dynamic model for a novel redundantly actuated parallel mechanism is formulated in the task space using Lagrangian formalism and the driving force is optimized by utilizing the minimal 2-norm method. By investigating the contribution of each term in the dynamic model to the driving force, a simplified strategy of the dynamic model for real-time control application is presented, and the subsequent model error is compensated by adopting RBF neural network. Simulation results verify the correctness and effectiveness of the proposed dynamic model and simplified strategy.

Reconfiguration analysis of a 3-DOF parallel mechanism using Euler parameter quaternions and algebraic geometry method

This paper deals with the reconfiguration analysis of a 3-DOF (degrees-of-freedom) parallel mechanism (PM) with multiple operation modes – a disassembly-free reconfigurable PM – using the Euler parameter quaternions and algebraic geometry approach. At first, Euler parameter quaternions are classified into 15 cases based on the number of constant zero components and the kinematic interpretation of different cases of Euler parameter quaternions is presented. A set of constraint equations of a 3-RER PM with orthogonal platforms is derived with the orientation of the moving platform represented using a Euler parameter quaternion and then solved using the algebraic geometry method. It is found that this 3-RER PM has 15 3-DOF operation modes, including four translational modes, six planar modes, four zero-torsion-rate motion modes and one spherical mode. The transition configurations, which are singular configurations, among different operation modes are also presented. Especially, the transition configurations in which the PM can switch among eight operation modes are revealed for the first time.

A 6-DOF reconfigurable hybrid parallel manipulator

This paper presents a case study on a reconfigurable hybrid parallel robot dubbed ReSl-Bot. It addresses the realm of reconfigurable 6-DOF parallel mechanisms, for sustainable manufacturing. It also features a self-reconfigurable architecture. A systematic analysis involving kinematics, constant orientation workspace, singularity and stiffness is developed in detail. Interesting features are discussed, revealing some unique characteristics of the studied architecture. A multi-objective optimization procedure is also carried out with weighted stiffness, dexterity and workspace volume as the performance indices.

Kinematic Analysis of a Novel 3-DOF Parallel Mechanism with Actuation Redundancy

Kinematic analysis plays an important role in the research of parallel kinematic mechanism. This paper addresses a novel forward kinematic solution based on RBF neural network for a novel 2PRRR-PPRR redundantly actuated parallel mechanism. Simulation results illustrate the validity and feasibility of the kinematic analysis method.

The Application of a Grating Tiling Device with Parallel Mechanism in an Inertial Confinement Fusion (ICF) System

The size of pulse compression gratings (PCG) is very big in the ICF system, so we obtained a large size grating by mechanically stitching small caliber gratings. And we design the splicing mechanism to be a 5-DOF Parallel Mechanism with macro/micro dual feed drive control to meet the requirements of large travel, high precision, high stability and 5-DOF of the grating tiling. The macro-moving part is designed to be the 5PTS-1PPS parallel mechanism, using the Feed Mechanism of ballscrew with Stepper Motor Drive.The micro-moving part is designed to be 5TSP-1PPS parallel mechanism, using the feed mechanism of Flexure Hinge with Piezoelectric Ceramic Actuator. We derived control algorithm of parallel mechanism by the method of the Kinematics of parallel mechanism. We analyzed the systematic error and put forward the error correction method in order to improve the positioning accuracy. At last, we designed an optical detecting system to evaluate the feasibility of this scheme, the positioning accuracy and the Stability of parallel Splicing structure. The results showed that the mechanism performance can meet the requirements of grating tiling work.

Design and Analysis of a Novel 5 Dimensional Active Vibration Isolator with Parallel Mechanism

A novel 5-DOF parallel mechanism applied to active vibration isolation is proposed in this paper. And by using Newton-Euler approach we set up models of the kinematics and dynamics of the isolator. Besides, a wide-range giant magnetostrictive actuator (GMA) composed of a GMA and a micro-displacement amplification mechanism is designed for the actuation of the isolator. Finally modal analysis of this isolator is carried out in ANSYS software to testify that the parallel mechanism is suitable for active vibration isolation.

Solution of Working Space about the 4-DOF Parallel Mechanism by ADAMS

This article is based on ADAMS software platform to solve working space of the 4-DOF parallel mechanism. Design a kind of 4-DOF parallel mechanism and establish virtual prototype on ADAMS software platform. Then through enumeration three branched chain parameters combination, even without the premise of kinematics positive solution, we can solve it working space using the forward solving method and get the branched chain parameter with the reference point position corresponding numerical relations. It greatly simplifies the solution of the working space of parallel mechanism, is more advantageous to parameter optimization and trajectory planning of parallel mechanism.

Error Analysis of a 3-DOF Parallel Mechanism for Milling Applications

Parallel mechanisms have been investigated during the last two decades, due to the fact that they present some advantages in a comparison with serial structures. This work deals with the error analysis of a 3-dof asymmetric parallel mechanism, purposely conceived for milling applications. In a comparison with the previous proposed concepts, this type of kinematic structure demonstrates a promising behavior. Topologically, the architecture is simpler and lighter than Tricept because it has no central passive limb. In addition, only the constraining active limb needs to satisfy the parallelism and orthogonality conditions. Furthermore, one degree of freedom, associated to the third actuator, is decoupled from the other two. Important issues, related to this type of kinematic structure, such as the mappings of the tool positioning error throughout the available workspace, due to the actuators imprecisions and manufacturing tolerances, are discussed in detail.

A new six-parallel-legged walking robot for drilling holes on the fuselage

In this paper, a new kind of six-parallel-legged robot is presented. It is designed for drilling holes on the aircraft surface. Each leg of the robot is a 3-DOF parallel mechanism with three chains: 1UP and 2UPS. The three prismatic joints are active joints and can be controlled either by position or by force. First, the task process and the gait plan are discussed and then, according to the requirement, the control method is introduced. After that, the mechanism topology patterns under different working conditions are studied and the control mode of each motor is determined. Then the kinematical model is built up, based on which the position control curves can be obtained. The simulation result shows that the robot can walk pretty well on the fuselage surface and that the actuation forces are quite smooth. Furthermore, the first prototype has been manufactured and some experiments such as walking and manipulation have been done.

Design of Large Motion Range and Heavy Duty 2-DOF Spherical Parallel Wrist Mechanism

Wrist mechanisms are important elements of robotic arms because they significantly affect the arm’s handling ability. Although various wrist mechanisms have been developed to date, a mechanism with a compact structure, a wide range of motion and a large load capacity has not yet been realized. Thus, in this paper, we propose 2-DOF Spherical Parallel (2DSP) mechanism, a heavy-duty wrist mechanism with a large motion range, and clarify its features both analytically and experimentally. The 2DSP mechanism is driven by a 2-DOF spherical parallel mechanism and is supported by a universal joint located at its center. This structure allows the 2DSP mechanism to realize a large motion range and load capacity and simplifies its kinematic analysis. Based on this analysis, we clarify the design process to maximize the motion range and propose a preferable structure of passive joints from the viewpoint of load capacity and production cost. We also describe the detailed design of a 2DSP mechanism for a rescue robot we developed previously and verify the feasibility of the proposed mechanism.

The Statics Analysis and Verification of 3-DOF Parallel Mechanism Based on Two Methods

Statics of the 3-RSS/S parallel ankle-rehabilitation robot is analyzed in this paper using two methods, i.e. the component vector method and the principle of virtual work. Static equilibrium equations based on component vector theory were established on a moving platform, and cranks of 3-RSS/S parallel Ankle-rehabilitation Robot, using this method, to obtain mathematical relationships between the external torque of moving platform and the output torque of three cranks. The velocity Jacobian matrix of the robot is calculated firstly using the principle of virtual work method, then the force Jacobian matrix is obtained based on the relationship between velocity Jacobian matrix and force Jacobian matrix. The results of the two methods are verified and found to be consistent by calculation, and the force Jacobian matrix of the robot is the basis of the force feedback control for the Ankle-rehabilitation Robot.

Modeling, design, and control of 6-DoF flexure-based parallel mechanisms for vibratory manipulation

Small amplitude periodic motion of a 6-degree-of-freedom (DoF) rigid plate causes rigid parts on the surface to slide under the influence of friction as if immersed in a configuration-dependent velocity field. A plate whose motion is fully programmable is therefore a simple yet versatile manipulator. To develop such a manipulator, this paper addresses the design and control of a 6-DoF parallel mechanism intended for small-amplitude, high frequency vibration. We derive a linear model for the class of parallel mechanisms consisting of a rigid plate coupled to linear actuators through flexures. Using this model, we discuss manipulator design geared toward either universal parts feeding or single task automation. The design process is formulated as a constrained optimization over a design space that includes the geometry of the manipulator (actuator orientations and flexure attachment points) and the viscoelastic properties of the flexures. Finally, we present a frequency-based iterative learning controller for tracking periodic plate acceleration trajectories in R6 for all designs. Experimental data collected from our PPOD2 manipulator is used to validate the model and demonstrate the performance of the controller.

Multi-task oriented design of an asymmetric 3T1R type 4-DOF parallel mechanism

In performing tasks requiring less than 6 degrees-of-freedom (DOF), lower mobility robots having a parallel structure are effective. This work investigates an asymmetric type 4 degrees-of-freedom parallel mechanism having Schönflies motions. This mechanism would be useful for multi-purpose tasks because it incorporates a transmission linkage with appropriate output modules. The mobility analysis, kinematic modelling, and singularity analysis for the mechanism are performed. Optimal design parameters with respect to both the workspace size and kinematic isotropy are identified by employing composite global design index. In addition, to cope with the singularity problem, a new design involving redundant actuation is suggested. And dynamic simulations are conducted to reaffirm its high potential in real manufacturing applications.