Testing Pull-Rodof of the Parallel Kinematic Structure (original) (raw)

Didactic Prototype of a Machine Tool Based on a Parallel Kinematic Mechanism

In the past recent years Parallel Kinematic Mechanisms (PKM) have attracted a lot of attention from academic and industrial communities due to their potential applications not only as robot manipulators but also as machine tools. Traditionally, these systems are employed as flight simulators for pilot training or even people entertaining. From the analysis of their typical topologies, it can be observed that they are composed by two or more closed kinematic chain mechanisms. In general, they demonstrate a higher performance than serial kinematic mechanisms, once the last ones present deficiencies related to structural stiffness, load capacity and positioning accuracy. On the other hand, parallel kinematic mechanisms are much more rigid, accurate and have higher load capacity and, therefore, can be lighter. Besides, when these mechanisms are used as machine tools, they are able to produce workpieces with very complex geometries, giving shapes and surfaces which would be difficult to obtain from conventional or even NC machine tools. This article deals with a type of parallel kinematic mechanism with four degrees of mobility that allows positioning and orientation of the platform (table) that supports a piece to be machined. This article also presents the mechanism mathematical model, describes the prototype built, shows technical specifications of its subsystems and comments its future applications.

Kinematic-structural analysis of spatial mechanisms application to the parallel kinematic machines

A kinematic-structural analysis is considered on a well-known parallel kinematics manipulator: the Tsai manipulator, using procedures useful for other generic parallel manipulators. Firstly the kinematic analysis will be made, obtaining the singular configurations and the blocking positions, key points for the later structural analysis. Then the structural analysis of the mechanism will be made, observing the stiffness that presents for different positions within its workspace, and obtaining graphs that represent the stiffness of the mechanism based on the position.

Kinematic Analysis of Planar Parallel Mechanism

The paper deals with kinematic model of parallel mechanism equipped with elastic members. The main aim is to determine the workspace of particular point of the mechanism in order to designing of whole mechanism for the future. Whole mechanisms should consist of several same segments which creates concept of serial mechanism. Since there is investigated parallel mechanism, at first has to be solved inverse kinematic model in order to obtain generalized variables, which are necessary for direct kinematic model. In the paper Jacobian matrix is derived for investigated mechanism. Then the algorithm for inverse kinematic model is described. The inverse kinematic model uses damped least squares method which appears as suitable method for our purposes. The results of inverse kinematic solution is consequently used for direct kinematic model, which is described by homogeneous transformation matrices. The planar parallel mechanism is simulated in software Matlab and the results are expressed in the graphs as well as our approach is discussed in the conclusion.

Didatic prototype of a machine tool based on a parallel kinematic mechanism

2001

In the past recent years Parallel Kinematic Mechanisms (PKM) have attracted a lot of attention from academic andindustrial communities due to their potential applications not only as robot manipulators but also as machine tools. Traditionally, these systems are employed as flight simulators for pilot training or even people entertaining. From the analysis of their typical topologies, it can be observed that theyare composed by two or more closed kinematic chain mechanisms. In general, theydemonstrate a higher performance than serial kinematic mechanisms, once the last ones present deficiencies related to structural stiffness, load capacity and positioning accuracy. On the other hand, parallel kinematic mechanisms are much more rigid, accurate and have higher load capacity and, therefore, can be lighter. Besides, when these mechanisms are used as machine tools, they are able to produce workpieces with very complex geometries, giving shapes and surfaces which would be difficult to obt...

Characterisation of parallel kinematic machines based on structural workspaces

Mechanics & Industry, 2013

In this paper, we present the static and dynamic structural characterisation of a low-mobility parallel kinematic manipulator, involving analysis of its stiffness and vibrational dynamic behaviour. The study starts by building numerical models of the behaviour of the manipulator to be compared to experimental measurements from a prototype. For the case study, we consider a four-degree-of-freedom (x, y, z, θz) manipulator with prismatic actuators designed by the COMPMECH research group at the University of the Basque Country. The characterisation allows the behaviour of the static and dynamic stiffness, as well as the natural frequencies of the manipulator, to be mapped in the manipulator workspace. These maps together with kinematic, static and dynamic constraints lead to the definition of operational, static, dynamic and structural workspaces, respectively. Further, we analyse the modes of the manipulator to determine dynamic displacements, these being key in the performance in the machining tasks for which the robot was designed.

A Comparative Study of Parallel Kinematic Architectures for Machining Applications

Parallel kinematic mechanisms are interesting alternative designs for machining applications. Three 2-DOF parallel mechanism architectures dedicated to machining applications are studied in this paper. The three mechanisms have two constant length struts gliding along fixed linear actuated joints with different relative orientation. The comparative study is conducted on the basis of a same prescribed Cartesian workspace for the three mechanisms. The common desired workspace properties are a rectangular shape and given kinetostatic performances. The machine size of each resulting design is used as a comparative criterion. The 2-DOF machine mechanisms analyzed in this paper can be extended to 3-axis machines by adding a third joint.

A Novel Parallel-Kinematics Machine Tool

In the paper a novel parallel-kinematics machine (PKM) tool is introduced, consisting of two innovative components. The first is a manipulator capable of producing a special class of motions, namely, those produced with manipulators termed SCARA, an acronym Selective-Compliance Assembly Robot Arm. We propose to integrate this manipulator with another device, a tool-orienting head producing pitch and roll of a cutting tool; the latter is a mechanism of the automotive-differential type, whereby the gears have been replaced with cams and rollers. The first module of the PKM, contrary to conventional SCARA systems, has its four motors fixed to a common base, either at the ceiling or on the floor. The kinematics of the new manipulator is outlined. The second module of the PKM, an innovative robotic pitch-roll wrist, was designed using multi-lobe cams. The two-degree-of-freedom wrist has a double-layer structure. The outer layer consists of two roller-carriers (RCs), which are connected to actuators by means of corresponding shafts of horizontal axes protruding from the wrist frame. The inner layer is a cam sub-assembly driven by RCs to rotate as a planetary train, the wrist functioning, as their bevel-gear counterparts, under the principle of spherical differential mechanisms. The novel parallel-kinematics machine offers significant advantages over existing systems: higher dexterity of the tool-head and higher operational speed with sufficient rigidity, which should lead to higher productivity.

The Manta and the Kanuk: Novel 4-Dof Parallel Mechanisms for Industrial Handling

Proc. of ASME Dynamic Systems and Control Division …

Two novel 4-DOF very fast parallel robots were designed. This paper introduces the new parallel mechanism designs which are named the Manta and the Kanuk. In order to reduce manipulator overall costs, the actuator and encoder numbers are minimized to the exact effective degrees-of-freedoms (DOF) which is usually not the case in most parallel robot designs. The robots allow end-effector displacements along the three Cartesian translations and one platform transversal rotation. The two remaining rotations are blocked by the intrinsic mechanical structure including the rotation along the platform normal which is always limited in range. The main advantages are high stiffness through the multiple kinematic chain structure which allow for low mass designs. Moreover, they feature simple mechanical construction. Thus, it shall be possible to achieve very high throughput since high accelerations are feasible. To circumvent the known workspace limitations, the actuators were selected to be prismatic along linear axes. The applications are automated warehouse manipulation, mediatheque manipulation, machine tool tool changers, loading and unloading. A 2x other Equation still holds for angular calculations.