Direct Pose Measurement: A Suitable Way to Increase the Accuracy of Parallel Robots?

2007 ◽  
Author(s):  
Christian Munzinger ◽  
Martin Kipfmu¨ller
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Parallel Robots ◽  
Dynamic Parameters ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Parallel Kinematic Machines ◽  
Machine Tool Structures ◽  
Conventional Machine ◽  
Parallel Kinematic

Parallel robots are showing a high potential for the application in machine tools requesting high stiffness and dynamics. Nevertheless, a broad use of parallel mechanisms in machine tools is nowadays avoided by the minor accuracy of parallel kinematic machines compared to conventional machine tool structures, which entails the need for complex calibration algorithms. In this paper, a strategy to avoid the calibration of parallel kinematic machines by rearranging the measurement system to the end effector is presented. Because this rearrangement entails a massive modification of the machine tools control circuit that causes stability problems, first tests of the concept have been carried out via simulation. The focus of these tests was to determine the necessary dynamic parameters of a suitable machine tool’s structure. The results of these tests are used to derive guidelines for the design of a machine tool with direct pose measurement. Finally, a design approach for a suitable machine tool is presented.

scholarly journals Stiffness and Damping of Epoxy Granite

2020 ◽  
Vol 9 (3) ◽  
pp. 1105-1108
Keyword(s):  
Cast Iron ◽  
Machine Tool ◽  
Machine Tools ◽  
Weight Ratio ◽  
High Strength ◽  
Cutting Conditions ◽  
Polymer Concrete ◽  
Machine Tool Structures ◽  
Conventional Machine ◽  
Stiffness And Damping

The productivity and accuracy of machine tools now became most significant as the cutting conditions changes continuously. Therefore to withstand against these cutting conditions the machine tool structural material must have higher stiffness and damping. This review deals with various research works to study the stiffness and damping of epoxy granite or polymer concrete. It is reported that the epoxy granite shows improved damping and high strength to weight ratio than that of conventional machine tool structures of steel and cast iron.

Real-Time Error Prediction for High-Precision Operation of Parallel Kinematic Machines

2012 ◽  
Author(s):  
Z. M. Bi ◽  
Guoping Wang
Keyword(s):  
Real Time ◽  
Machine Tools ◽  
Real Time Control ◽  
Motion Error ◽  
Parallel Kinematic Machines ◽  
Time Control ◽  
Operation Speed ◽  
Conventional Machine ◽  
Internal Forces ◽  
Parallel Kinematic

Closed-loop parallel kinematic machines (PKMs) have been proposed to improve precision and operation speed over conventional machine tools and robots. However, an embarrassing dilemma is that most of the existing PKMs achieve very lower precision in contrast to equivalent serial machine tools or robots, which are competitive to same tasks. Limited works have been conducted to evaluate errors thus improve precision of machine in real-time control. It becomes necessary to explore the relation of the motion error with the dynamics of a PKM. In this paper, the new model of the error evaluation has been proposed; three major sources of error under consideration are the deformations of the components under dynamic loads, the deformations at joint contacts, and the clearances of passive joints. To illustrate the modeling procedure, the dynamic model of machine is developed to determine internal forces among components and locations of joint contacts. Errors caused by machine dynamics are evaluated analytically in real time; in particular, the errors happened at the contacts of passive joints are estimated based on Hertz theory. The developed error models can be applied to compensate the motion errors of tool tip in real-time. The Exechon parallel kinematic machine is used as a case study, the results from simulation has been compared with the test data.

A Parallely Actuated Work Support Module for Reconfigurable Machining Systems

1998 ◽  
Author(s):  
Venkat Gopalakrishnan ◽  
Sridhar Kota
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Degrees Of Freedom ◽  
Mechanical Design ◽  
Performance Criteria ◽  
Machining Accuracy ◽  
Parallel Mechanisms ◽  
Element Analysis ◽  
Work Support ◽  
Reconfigurable Machining

Abstract In order to respond quickly to changes in market demands and the resulting product design changes, machine tool manufacturers must reduce the machine tool design lead time and machine set-up time. Reconfigurable Machine Tools (RMTs), assembled from machine modules such as spindles, slides and worktables are designed to be easily reconfigured to accommodate new machining requirements. The essential characteristics of RMTs are modularity, flexibility, convertibility and cost effectiveness. The goal of Reconfigurable Machining Systems (RMSs), composed of RMTs and other types of machines, is to provide exactly the capacity and functionality, exactly when needed. The scope of RMSs design includes mechanical hardware, control systems, process planning and tooling. One of the key challenges in the mechanical design of reconfigurable machine tools is to achieve the desired machining accuracy in all intended machine configurations. To meet this challenge we propose (a) to distribute the total number of degrees of freedom between the work-support and the tool and (b) employ parallely-actuated mechanisms for stiffness and ease of reconfigurability. In this paper we present a novel parallely-actuated work-support module as a part of an RMT. Following a brief summary of a few parallel mechanisms used in machine tool applications, this paper presents a three-degree-of-freedom work-support module designed to meet the machining requirements of specific features on a family of automotive cylinder heads. Inverse kinematics, dynamic and finite element analysis are performed to verify the performance criteria such as workspace envelope and rigidity. A prototype of the proposed module is also presented.

scholarly journals Modal Kinematic Analysis of a Parallel Kinematic Robot with Low-Stiffness Transmissions

Robotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 132
Author(s):  
Paolo Righettini ◽  
Roberto Strada ◽  
Filippo Cortinovis
Keyword(s):  
High Speed ◽  
Parallel Robots ◽  
Maximum Speed ◽  
Kinematic Structure ◽  
End Effector ◽  
New Approach ◽  
Working Space ◽  
Modes Of Vibration ◽  
Parallel Kinematic ◽  
Actuated Joints

Several industrial robotic applications that require high speed or high stiffness-to-inertia ratios use parallel kinematic robots. In the cases where the critical point of the application is the speed, the compliance of the main mechanical transmissions placed between the actuators and the parallel kinematic structure can be significantly higher than that of the parallel kinematic structure itself. This paper deals with this kind of system, where the overall performance depends on the maximum speed and on the dynamic behavior. Our research proposes a new approach for the investigation of the modes of vibration of the end-effector placed on the robot structure for a system where the transmission’s compliance is not negligible in relation to the flexibility of the parallel kinematic structure. The approach considers the kinematic and dynamic coupling due to the parallel kinematic structure, the system’s mass distribution and the transmission’s stiffness. In the literature, several papers deal with the dynamic vibration analysis of parallel robots. Some of these also consider the transmissions between the motors and the actuated joints. However, these works mainly deal with the modal analysis of the robot’s mechanical structure or the displacement analysis of the transmission’s effects on the positioning error of the end-effector. The discussion of the proposed approach takes into consideration a linear delta robot. The results show that the system’s natural frequencies and the directions of the end-effector’s modal displacements strongly depend on its position in the working space.

Design Optimization of Machine-Tool Structures With Respect to Dynamic Characteristics

1983 ◽  
Vol 105 (1) ◽  
pp. 88-96 ◽  
Author(s):  
M. Yoshimura ◽  
T. Hamada ◽  
K. Yura ◽  
K. Hitomi
Keyword(s):  
Machine Tool ◽  
Design Optimization ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Structural Model ◽  
Optimization Method ◽  
Practical Applications ◽  
Design Variables ◽  
Design Changes ◽  
Machine Tool Structures

This paper proposes a design optimization method in which simplified structural models and standard mathematical programming methods are employed in order to optimize the dynamic characteristics of machine-tool structures in practical applications. This method is composed of three phases: (1) simplification, (2) optimization, and (3) realization. As design variables employed in this optimization are greatly reduced, machine-tool structures are optimized effectively in practice. With large design changes being conducted through this multiphase procedure, dynamic characteristics of machine tools can be greatly improved. This method is demonstrated on a structural model of a vertical lathe.

Effect of Workpiece Location on Manipulability Measure in 5-Axis-Controlled Machine Tools

2010 ◽  
Vol 4 (3) ◽  
pp. 268-272 ◽  
Author(s):  
Yoshio Mizugaki ◽  
Keyword(s):  
Machine Tool ◽  
Cutting Force ◽  
Machine Tools ◽  
Inverse Kinematics ◽  
Computational Results ◽  
Computer Aided Manufacturing ◽  
End Effector ◽  
Computer Aided ◽  
Manipulability Measure ◽  
Work Table

This paper clarifies the effects of workpiece location in a 5-axis-controlled machine tool from the viewpoint of Inverse kinematics including Manipulability measure: an index representing the variance of movement of end-effector in a serial linkage. Firstly the importance of Inverse kinematics in Computer Aided Manufacturing is emphasized and then Singularity and Manipulability measure are expanded for multiaxis-controlled machine tools. Secondly the computational results of Manipulability measure for different workpiece locations and tool orientations show that setting the workpiece in the centre of the rotary work-table is most preferable. Regardless of large differences in Manipulability measure at different locations, there were few differences of the resultant cutting force in machining experiments. Finally the brief conclusion is mentioned.

Efficient Simulation of Parallel Kinematic Machine Tools

2009 ◽  
Author(s):  
Martin Kipfmu¨ller ◽  
Christian Munzinger
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Development Process ◽  
Special Focus ◽  
Full Potential ◽  
Parallel Kinematic Machine ◽  
Machine Tool Industry ◽  
Simulation Tools ◽  
Parallel Kinematic ◽  
Parallel Kinematic Machine Tools

Today’s machine tool industry mainly consists of small and medium-sized enterprises. Thus, the simulation of new products often does not seem to be cost effective due to the small number of items produced and the high cost of simulation tools. Nevertheless, the use of simulation tools is essential in order to tap the full potential of new challenging concepts like parallel kinematic machines. This paper presents a simulation method supporting the development process of parallel kinematic machine tools from the first concept to the prototype. In order to render the method applicable for the machine tool industry, a special focus is placed on tool efficiency. A modular modeling concept will ensure that the structure of the first kinematic model of the concept phase can be enhanced during the development process and developed into more detailed models, e.g. for dimensioning calculations or to study the dynamic behavior of machine tools. Thus, the method efficiently supports the whole development process with a simulation model gradually increasing in detail according to the requirements of the machine tool designer.

Congratulations! Best Paper Award & Best Review Award 2013

2013 ◽  
Vol 7 (5) ◽  
pp. 473-473
Author(s):  
Editorial Office
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Selection Process ◽  
Indirect Measurement ◽  
Paper Award ◽  
Award Winner ◽  
Machine Tool Structures ◽  
Volumetric Accuracy ◽  
Automation Technology ◽  
Five Axis

The fourth Best Paper Award 2013 and the first Best Review Award 2013 ceremony was held in Kasumigaseki, Tokyo, Japan, on August 2, 2013, attended by the winner and IJAT committee members who took part in the selection process. The Best Paper was severely selected from among 81 papers published in Vol.6 (2012) and the Best Review was selected from 9 reviews published from 2010 to 2012. The Best Paper Award winner was given a certificate with a nearly US$1,000 honorarium and the Best Review Award winner was given a certificate with commemorative shield.   The Best Paper Award 2013 is as follows: Title: Estimation of Dynamic Mechanical Error for Evaluation of Machine Tool Structures Authors: Daisuke Kono, Sascha Weikert, Atsushi Matsubara, and Kazuo Yamazaki Int. J. of Automation Technology Vol.6 No.2, pp. 147-153, March 2012   The Best Review Award 2013 is as follows: Title: Indirect Measurement of Volumetric Accuracy for Three-Axis and Five-Axis Machine Tools: A Review Authors: Soichi Ibaraki and Wolfgang Knapp Int. J. of Automation Technology Vol.6 No.2, pp. 110-124, March 2012

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

1999 ◽  
Author(s):  
Luc H. Rolland
Keyword(s):  
Parallel Mechanism ◽  
Kinematic Chain ◽  
Parallel Robot ◽  
Chain Structure ◽  
Parallel Robots ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Low Mass ◽  
Loading And Unloading ◽  
Very High

Abstract 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.

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