Machines

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13 pages, 3820 KiB

Open AccessArticle

Transfer of Process References between Machine Tools for Online Tool Condition Monitoring

by Berend Denkena, Benjamin Bergmann and Tobias H. Stiehl

Machines 2021, 9(11), 282; https://doi.org/10.3390/machines9110282 - 10 Nov 2021

Cited by 4 | Viewed by 2626

Process and tool condition monitoring systems are a prerequisite for autonomous production. One approach to monitoring individual parts without complex cutting simulations is the transfer of knowledge among similar monitoring scenarios. This paper introduces a novel monitoring method which transfers monitoring limits for [...] Read more.

Process and tool condition monitoring systems are a prerequisite for autonomous production. One approach to monitoring individual parts without complex cutting simulations is the transfer of knowledge among similar monitoring scenarios. This paper introduces a novel monitoring method which transfers monitoring limits for process signals between different machine tools. The method calculates monitoring limits statistically from cutting processes carried out on one or more similar machines. The monitoring algorithm aims to detect general process anomalies online. Experiments comprise face-turning operations at five different lathes, four of which were of the same model. Results include the successful transfer of monitoring limits between machines of the same model for the detection of material anomalies. In comparison to an approach based on dynamic time warping (DTW) and density-based spatial clustering of applications with noise (DBSCAN), the new method showed fewer false alarms and higher detection rates. However, for the transfer between different models of machines, the successful application of the new method is limited. This is predominantly due to limitations of the employed process component isolation and differences between machine models in terms of signal properties as well as execution speed. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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18 pages, 4483 KiB

Open AccessArticle

Kinematic Analysis and Parameter Measurement for Multi-Axis Laser Engraving Machine Tools

by Zhenshuo Yin, Qiang Liu, Pengpeng Sun and Ji Ding

Machines 2021, 9(10), 237; https://doi.org/10.3390/machines9100237 - 16 Oct 2021

Cited by 3 | Viewed by 3281

Abstract

Multi-axis Laser Engraving Machine Tools (LEMT) are widely used in precision processing of parts with complex surface. The accuracy of kinematic model and parameter measurement are the key factors determining the processing quality of LEMT. In this paper, a kinematic model of multi-axis [...] Read more.

Multi-axis Laser Engraving Machine Tools (LEMT) are widely used in precision processing of parts with complex surface. The accuracy of kinematic model and parameter measurement are the key factors determining the processing quality of LEMT. In this paper, a kinematic model of multi-axis LEMT was established based on Homogeneous Transformation Matrix (HTM). Two types of unknown parameters, linkage parameters and positioning parameters, were measured in the presented model. Taking advantage of the characteristics of laser processing, this paper proposed a rapid measurement method of linkage parameters by combining the machine tool motion with the laser marking action. For positioning parameters, this study proposed a non-contact measurement method based on structured light scanner, which can obtain the translation values and the rotation values from the Workpiece Coordinate System (WCS) to the Basic Coordinate System (BCS) simultaneously. After the measurement of two kinds of parameters of a multi-axis LEMT was completed, the processing of a spatial curve was performed and the average contour error was controlled at 15.1

μ

m, which is sufficient to meet the project requirements. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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25 pages, 8964 KiB

Open AccessArticle

Reconfigurable Machine Tool Design for Box-Type Part Families

by Yongquan Wang, Guangpeng Zhang, Jiali Wang, Pan Liu and Nina Wang

Machines 2021, 9(8), 148; https://doi.org/10.3390/machines9080148 - 29 Jul 2021

Cited by 2 | Viewed by 2914

Abstract

The reconfigurable manufacturing system (RMS) is a new manufacturing technology and paradigm that resolves the contradictions regarding high efficiency, low cost and flexible production in the mass production of part families. Reconfigurable machine tools (RMTs) are the core components of RMSs. A new [...] Read more.

The reconfigurable manufacturing system (RMS) is a new manufacturing technology and paradigm that resolves the contradictions regarding high efficiency, low cost and flexible production in the mass production of part families. Reconfigurable machine tools (RMTs) are the core components of RMSs. A new approach is proposed for the design of RMTs, which is closely related to the process planning of a given box-type part family. The concepts of the processing unit and the processing segment are presented; they are not only the basic elements of the processing plans of machined parts, but also closely related to the structural design of RMTs. Processing units created by processing features can be combined into various processing segments. All the processing units of one processing segment correspond to the machining operations performed by one RMT. By arranging the processing segments according to the processing sequence, a variety of feasible processing plans for a part can be obtained. Through analysis of the established similarity calculation model for processing plans, the most similar processing plans for the parts in a given part family can be determined and used for the structural design of RMTs. Therefore, the designed RMTs can achieve rapid conversion of processing functions with the least module replacement or adjustment to realize the production of the parts in the part family. Taking the production of a gearbox part family as an example, the validity of the presented method is verified. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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12 pages, 1508 KiB

Open AccessEditor’s ChoiceArticle

Dimensional (Parametric) Synthesis of the Hexapod-Type Parallel Mechanism with Reconfigurable Design

by Alexey Fomin, Anton Antonov, Victor Glazunov and Giuseppe Carbone

Machines 2021, 9(6), 117; https://doi.org/10.3390/machines9060117 - 12 Jun 2021

Cited by 15 | Viewed by 3323

Abstract

The study provides a solution to a dimensional synthesis problem for a hexapod-type reconfigurable parallel mechanism, which can change its configuration to realize different trajectories of its output link while having a single drive. The work presents an original procedure to find the [...] Read more.

The study provides a solution to a dimensional synthesis problem for a hexapod-type reconfigurable parallel mechanism, which can change its configuration to realize different trajectories of its output link while having a single drive. The work presents an original procedure to find the dimensions of some mechanism’s links and their initial configuration to reproduce these trajectories. After describing the mechanism, the paper examines kinematic relations representing the basis for the subsequent synthesis algorithm. Next, the obtained expressions are extended and provide a system of equations to be solved. The structure of this equation system allows it to be solved effectively by numerical methods, which is demonstrated with an example. The proposed algorithm of dimensional synthesis does not require solving the optimization problems, in contrast to the familiar methods of dimensional synthesis of parallel mechanisms. Further, the suggested approach to the synthesis problem allows finding solution in a fast and computationally efficient manner. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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6292 KiB

Open AccessArticle

Direct Uncertainty Minimization Framework for System Performance Improvement in Model Reference Adaptive Control

by Benjamin C. Gruenwald, Tansel Yucelen and Jonathan A. Muse

Machines 2017, 5(1), 9; https://doi.org/10.3390/machines5010009 - 8 Mar 2017

Cited by 11 | Viewed by 4754

Abstract

Inthispaper, adirectuncertaintyminimizationframeworkisdevelopedanddemonstrated for model reference adaptive control laws. The proposed framework consists of a novel architecture involvingmodiﬁcationtermsintheadaptivecontrollawandtheupdatelaw. Inparticular,theseterms areconstructedthroughagradientminimizationprocedureinordertoachieveimprovedclosed-loop system performance with adaptive control laws. The proposed framework is ﬁrst developed for adaptive control laws with linear reference models and then generalized to [...] Read more.

Inthispaper, adirectuncertaintyminimizationframeworkisdevelopedanddemonstrated for model reference adaptive control laws. The proposed framework consists of a novel architecture involvingmodiﬁcationtermsintheadaptivecontrollawandtheupdatelaw. Inparticular,theseterms areconstructedthroughagradientminimizationprocedureinordertoachieveimprovedclosed-loop system performance with adaptive control laws. The proposed framework is ﬁrst developed for adaptive control laws with linear reference models and then generalized to adaptive control laws with nonlinear reference models. Two illustrative numerical examples are included to demonstrate the efﬁcacy of the proposed framework. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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2226 KiB

Open AccessArticle

Life Cycle Analysis of Double-Arm Type Robotic Tools for LCD Panel Handling

by Heather Wyatt, Allan Wu, Rami Thomas and Yuelei Yang

Machines 2017, 5(1), 8; https://doi.org/10.3390/machines5010008 - 4 Mar 2017

Cited by 14 | Viewed by 8846

Abstract

This study includes a life cycle assessment of double-arm type robotic tools made with three different materials. The robotic arms are used for Liquid Crystal Display (LCD) panel handling. The environmental impacts generated during all the life stages of the robots have been [...] Read more.

This study includes a life cycle assessment of double-arm type robotic tools made with three different materials. The robotic arms are used for Liquid Crystal Display (LCD) panel handling. The environmental impacts generated during all the life stages of the robots have been investigated. The study shows that composite materials have less environmental impact compared with metallic materials. It is also found that the most significant impact category generated by the robotic tools is carcinogen, while the use stage of the robotic tool’s life cycle has the greatest environmental impact. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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31677 KiB

Open AccessArticle

A Method for Design of Modular Reconfigurable Machine Tools

by Zhengyi Xu, Fengfeng Xi, Lilan Liu and Li Chen

Machines 2017, 5(1), 5; https://doi.org/10.3390/machines5010005 - 4 Feb 2017

Cited by 27 | Viewed by 12450

Abstract

Presented in this paper is a method for the design of modular reconfigurable machine tools (MRMTs). An MRMT is capable of using a minimal number of modules through reconfiguration to perform the required machining tasks for a family of parts. The proposed method [...] Read more.

Presented in this paper is a method for the design of modular reconfigurable machine tools (MRMTs). An MRMT is capable of using a minimal number of modules through reconfiguration to perform the required machining tasks for a family of parts. The proposed method consists of three steps: module identification, module determination, and layout synthesis. In the first step, the module components are collected from a family of general-purpose machines to establish a module library. In the second step, for a given family of parts to be machined, a set of needed modules are selected from the module library to construct a desired reconfigurable machine tool. In the third step, a final machine layout is decided though evaluation by considering a number of performance indices. Based on this method, a software package has been developed that can design an MRMT for a given part family. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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30440 KiB

Open AccessArticle

Automatic Motion Generation for Robotic Milling Optimizing Stiffness with Sample-Based Planning

by Julian Ricardo Diaz Posada, Ulrich Schneider, Arjun Sridhar and Alexander Verl

Machines 2017, 5(1), 3; https://doi.org/10.3390/machines5010003 - 18 Jan 2017

Cited by 20 | Viewed by 9816

Abstract

Optimal and intuitive robotic machining is still a challenge. One of the main reasons for this is the lack of robot stiffness, which is also dependent on the robot positioning in the Cartesian space. To make up for this deficiency and with the [...] Read more.

Optimal and intuitive robotic machining is still a challenge. One of the main reasons for this is the lack of robot stiffness, which is also dependent on the robot positioning in the Cartesian space. To make up for this deficiency and with the aim of increasing robot machining accuracy, this contribution describes a solution approach for optimizing the stiffness over a desired milling path using the free degree of freedom of the machining process. The optimal motion is computed based on the semantic and mathematical interpretation of the manufacturing process modeled on its components: product, process and resource; and by configuring automatically a sample-based motion problem and the transition-based rapid-random tree algorithm for computing an optimal motion. The approach is simulated on a CAM software for a machining path revealing its functionality and outlining future potentials for the optimal motion generation for robotic machining processes. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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6435 KiB

Open AccessFeature PaperArticle

Study on the Kinematic Performances and Optimization for Three Types of Parallel Manipulators

by Dan Zhang and Bin Wei

Machines 2016, 4(4), 24; https://doi.org/10.3390/machines4040024 - 16 Dec 2016

Cited by 3 | Viewed by 4675

Abstract

The modelling, optimization issues and stiffness for several types of three degrees-of-freedom parallel robotic manipulators, i.e., 3-DOF pure translational, 3-DOF pure rotational and 3-DOF mixed motion types, are studied in this paper. First of all, the kinematics and Jacobian for the robotic manipulators [...] Read more.

The modelling, optimization issues and stiffness for several types of three degrees-of-freedom parallel robotic manipulators, i.e., 3-DOF pure translational, 3-DOF pure rotational and 3-DOF mixed motion types, are studied in this paper. First of all, the kinematics and Jacobian for the robotic manipulators are determined through different approaches; secondly, objective functions modelling are presented, and the associated optimization issues and the geometric parameters’ effect on the objective functions for the robotic mechanisms are illustrated and analyzed in detail. Through employing several multi-objective optimization approaches, we manifest an overall process and approach for multi-objective optimization of robotic systems. The correlation among different stiffness models is finally presented. The results indicate that the kinetostatic compliance model is the closest one to the traditional stiffness model. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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1290 KiB

Open AccessArticle

Kinematics and Dynamics of a Translational Parallel Robot Based on Planar Mechanisms

by Mario A. Garcia-Murillo, Roger E. Sanchez-Alonso and Jaime Gallardo-Alvarado

Machines 2016, 4(4), 22; https://doi.org/10.3390/machines4040022 - 9 Nov 2016

Cited by 7 | Viewed by 10788

Abstract

In this contribution, a novel translational parallel robot composed of an arrangement of mechanisms with planar motion is presented. Its mobility is analyzed and the position analysis is solved by using equations derived from mechanical constraints. Furthermore, the analysis of velocity and acceleration [...] Read more.

In this contribution, a novel translational parallel robot composed of an arrangement of mechanisms with planar motion is presented. Its mobility is analyzed and the position analysis is solved by using equations derived from mechanical constraints. Furthermore, the analysis of velocity and acceleration are solved by means of the screw theory. For completeness, the inverse dynamics are also presented and solved by means of an interesting combination of the screw theory and the virtual work principle. Finally, a numerical example is included to show the application of the kinematic model, which is verified with the aid of a commercially available software. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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3822 KiB

Open AccessArticle

Study on Payload Effects on the Joint Motion Accuracy of Serial Mechanical Mechanisms

by Dan Zhang and Bin Wei

Machines 2016, 4(4), 21; https://doi.org/10.3390/machines4040021 - 4 Nov 2016

Cited by 4 | Viewed by 4495

Abstract

Robotic manipulators have been widely used in many arenas, when the robotic arm performs positioning, a traditional controller (e.g., a proportional-integral-derivative, PID controller) has the problem of not being able to compensate the payload variations. When the end-effector of the robotic arm grasps [...] Read more.

Robotic manipulators have been widely used in many arenas, when the robotic arm performs positioning, a traditional controller (e.g., a proportional-integral-derivative, PID controller) has the problem of not being able to compensate the payload variations. When the end-effector of the robotic arm grasps different payload masses as most applications require, the output of joint motion will vary under different payload masses, which will decrease the end-effector positioning accuracy of the robotic arm system. Based on the model reference adaptive control technique, the payload variation effect can be solved, therefore improving the positioning accuracy. This paper studies payload effects on the joint motion accuracy of serial mechanical mechanisms. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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6848 KiB

Open AccessArticle

Self-Sensing Electromagnets for Robotic Tooling Systems: Combining Sensor and Actuator

by Tobias Kamf and Johan Abrahamsson

Machines 2016, 4(3), 16; https://doi.org/10.3390/machines4030016 - 10 Aug 2016

Cited by 9 | Viewed by 7198

Abstract

A low-cost method, which integrates distance sensing functionality into a switched electromagnet by using a hybrid switching mode and current ripple measurements, is proposed. The electromagnet is controlled by a micro-controller via a MOSFET H bridge, utilizing a comparator-based current control. Additionally, a [...] Read more.

A low-cost method, which integrates distance sensing functionality into a switched electromagnet by using a hybrid switching mode and current ripple measurements, is proposed. The electromagnet is controlled by a micro-controller via a MOSFET H bridge, utilizing a comparator-based current control. Additionally, a method for calculating the inductance of the electromagnet and approximating the magnetic contact between the electromagnet and its target is also presented. The resulting tool is attached to an industrial robot, and the system performance using this setup is evaluated. Distance sensing in the range of 0 mm to 5.2 mm is demonstrated. It is also shown that the relation between magnetic contact, coil current and calculated inductance can be reduced to a predictive look-up table, enabling the quality of the magnetic contact to be estimated using minimal computational effort. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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