Publication Date: 2016
Advanced Robotics (01691864)30(2)pp. 97-108
Handling objects with robotic soft fingers without considering the odds of slippage are not realistic. Grasping and manipulation algorithms have to be tested under such conditions for evaluating their robustness. In this paper, a dynamic analysis of rigid object manipulation with slippage control is studied using a two-link finger with soft hemispherical tip. Dependency on contact forces applied by a soft finger while grasping a rigid object is examined experimentally. A power-law model combined with a linear viscous damper is used to model the elastic behavior and damping effect of the soft tip, respectively. In order to obtain precise dynamic equations governing the system, two second-order differential equations with variable coefficients have been designed to describe the different possible states of the contact forces accordingly. A controller is designed based on the rigid fingertip model using the concept of feedback linearization for each phase of the system dynamics. Numerical simulations are used to evaluate the performance of the controller. The results reveal that the designed controller shows acceptable performance for both soft and rigid finger manipulation in reducing and canceling slippage. Furthermore, simulations indicate that the applied force in the soft finger manipulation is considerably less than the rigid "one.". © 2015 Taylor and Francis and The Robotics Society of Japan.
Hadian jazi, S.,
Keshmiri m., M.,
Sheikholeslam, F.,
Shahreza, M.G.,
Keshmiri, M. Publication Date: 2014
Robotica (02635747)32(5)pp. 783-802
Considering undesired slippage between manipulated object and finger tips of a multi-robot system, adaptive control synthesis of the object grasping and manipulation is addressed in this paper. Although many studies can be found in the literature dealing with grasp analysis and grasp synthesis, most assume no slippage between the finger tips and the object. Slippage can occur for many reasons such as disturbances, uncertainties in parameters, and dynamics of the system. In this paper, system dynamics is analyzed using a new presentation of friction and slippage dynamics. Then an adaptive control law is proposed for trajectory tracking and slippage control of the object as well as compensation for parameter uncertainties of the system, such as mass properties and coefficients of friction. Stability of the proposed adaptive controller is studied analytically and the performance of the system is studied numerically. Copyright © Cambridge University Press 2013.
Hadian jazi, S.,
Keshmiri m., M.,
Sheikholeslam, F.,
Shahreza, M.G.,
Keshmiri, M. Publication Date: 2012
Advanced Robotics (01691864)26(15)pp. 1693-1726
This paper addresses dynamic analysis and control synthesis of object grasping in a cooperative multirobot system with n-serial manipulators from an undesired slippage point of view. Two control approaches are presented in this article; a modified version of a conventional method in grasp synthesis and a new method based on a new modeling of system dynamics. A new formulation for frictional contact is used in dynamical modeling, where equality and inequality equations of the standard Coulomb friction model are all converted to a single second-order differential equation. A multiphase controller is utilized to control the object trajectory tracking as well as object slippage in the new control approach. Performance and robustness of both approaches are studied numerically. The results show superiority of the new method and its desirable and excellent performance. © 2012 Taylor & Francis and The Robotics Society of Japan.
Considering slippage between finger tips and an object, adaptive control synthesis of grasping and manipulating an object by a multi-fingered system is addressed in this paper. Slippage can occur due to many reasons such as disturbances, uncertainties in parameters and dynamics. In this paper, using a novel representation of friction and slippage dynamics, a new approach is introduced to analyze the system dynamics. Then an adaptive controller with a simple update rule is proposed to ensure the bounded trajectory tracking and slippage control, and at the same time to compensate for parameter uncertainties including coefficients of friction. The performance of the proposed adaptive controller is shown analytically and studied numerically. Copyright © 2008 by ASME.
Publication Date: 2008
2(PARTS A AND B)pp. 1047-1055
Considering slippage between finger tips and an object, adaptive control synthesis of grasping and manipulating an object by a multi-fingered system is addressed in this paper. Slippage can occur due to many reasons such as disturbances, uncertainties in parameters and dynamics. In this paper, using a novel representation of friction and slippage dynamics, a new approach is introduced to analyze the system dynamics. Then an adaptive controller with a simple update rule is proposed to ensure the bounded trajectory tracking and slippage control, and at the same time to compensate for parameter uncertainties including coefficients of friction. The performance of the proposed adaptive controller is shown analytically and studied numerically. © 2008 by ASME.
Publication Date: 2008
Advanced Robotics (01691864)22(13-14)pp. 1559-1584
Grasping an object by a cooperating system such as multi-fingered hands and multi-manipulator robotic system has received much attention. Research has focused on analysis of force-closure grasps and the synthesis of optimal grasping, when there is no slipping condition. Although the control system is designed to keep the contact force in the friction cone and avoid the slipping condition, slippage can occur for many reasons. In this research, dynamics analysis and control synthesis of a manipulator moving an object on a horizontal surface using the contact force of an end-effector are performed considering the slipping condition. Equality and inequality equations of frictional contact conditions are replaced by a single second-order differential equation with switching coefficients in order to facilitate the dynamic modeling. Accuracy of this modeling is verified by comparing the results of the model with those of SimMech. Using this modeling of friction, a set of reduced order form is obtained for equations of motion of the system. A new method is proposed to control the object motion and the end-effector undesired slippage based on the reduced form. Finally, performance of the method is evaluated both numerically and experimentally. © 2008 VSP.
Considering slippage in the end-effectors of a set of two cooperating manipulators grasping an object, this paper presents a new dynamic modeling and control synthesis of grasping phenomenon. This dynamic modeling is based on a new formulation for frictional contact where equality and inequality equations in the standard Coulomb Friction model are converted all to a single second order differential equation with switching coefficients. Accuracy of the friction model is verified by comparing its results with those of SimMech. Then equations of motion are reduced to conventional form for nonconstrained system. Assuming the new reduced order system to be BIBO, internal stability of the whole system is analyzed. In the control synthesis of the system a multi phase controller is utilized to control the trajectory tracking of the object as well as slippage control of the end-effectors on the object surfaces. For the proposed controller, a proof is given for system stability and its performance and robustness are shown numerically. The results show superiority of the method and its desirable and excellent performance. Copyright © 2007 by ASME.
Publication Date: 2007
Proceedings of the IASTED International Conference on Modelling and Simulation (10218181)pp. 149-154
Almost all of the researches on object grasping by manipulators and cooperating robots consider no slippage between end-effectors and object, however it can occur. This paper presents dynamics analysis and control synthesis of a manipulator moving an object on a horizontal surface using contact force of end-effector considering slipping condition. Equality and inequality equations of frictional contact conditions are replaced by a single second order differential equation with switching coefficients in order to facilitate the dynamical modeling. Using this modeling of friction, a set of reduced order form is obtained for equations of motion of the system and a new method is proposed to control end-effector slippage on the object.
Publication Date: 2025
Expert Systems with Applications (0957-4174)264
Additive manufacturing (AM) has become a transformative technology in modern production, enabling complex geometric designs with minimal material waste. A significant aspect of AM, particularly in fused deposition modeling (FDM), is the need for precise prediction of mechanical properties, such as ultimate tensile strength (UTS), which is crucial for industrial applications. This study examines whether simple machine learning (ML) algorithms can accurately predict the UTS of 3D-printed polylactic acid (PLA) parts, and evaluates the effectiveness of ML techniques, especially ensemble methods, in enhancing prediction accuracy. To this end, the study compares simple ML algorithms to identify the most accurate model for predicting the UTS of 3D-printed PLA parts. Subsequently, an average ensemble technique combines four ML algorithms, namely categorical boosting (CatBoost), extreme gradient boosting (XGBoost), gradient boosting machine (GBM), and light gradient boosting machine (LGBM), to predict UTS. In this technique, the average predicted UTS values of CatBoost, XGBoost, GBM, and LGBM are taken as the final predicted UTS value. Additionally, 11 ensemble configurations of these algorithms are analyzed to determine the optimized ensemble configuration. The results show that the CatBoost algorithm, with an R2 of 94.46%, achieved the highest predictive accuracy among individual ML algorithms. Moreover, the CatBoost-XGBoost-GBM-LGBM ensemble was the most accurate configuration, achieving an R2 of 98.05% with less than 10% error in predicting 37 external data points not included in the training and testing sets. This study advances predictive modeling in AM by demonstrating that ML, particularly ensemble techniques, can reliably predict material properties, paving the way for more robust applications of AM in industry. © 2024 Elsevier Ltd
Publication Date: 2025
Materials Letters (18734979)379
Publication Date: 2024
Materials Today Communications (23524928)41
Assessing the elastic modulus of 3D-printed polylactic acid (PLA) components is essential for understanding their stiffness and load capacity, which are crucial for predicting product performance and durability. In this study, the predictive accuracy of a Tabular Neural Network (TabNet) algorithm for determining the elastic modulus of 3D-printed PLA components via fused deposition modeling (FDM) was investigated. Utilizing a comprehensive dataset of 128 literature-sourced data points, divided into 80 % for training and 20 % for validation, the study proposed a new Taguchi-based method for efficient hyperparameter optimization of the TabNet algorithm. This optimization revealed that a configuration of 8 decision blocks, 16 attention blocks, and 5 decision steps, along with the “Adam” optimizer, a gamma of 1, learning rate of 0.1, and lambda-sparse of 0.01, yielded the highest prediction accuracy for the elastic modulus of PLA parts. The performance of the optimized TabNet model was evaluated using R-squared (R²), Mean Absolute Error (MAE), Mean Squared Error (MSE), and Root Mean Squared Error (RMSE) measures. The findings highlighted an R² of 96.855 %, an MAE of 0.158, an MSE of 0.037, and an RMSE of 0.193 in the validation dataset, demonstrating substantial predictive reliability. To further test the model's robustness, fourteen unseen data points were analyzed. The observed discrepancies between predicted and actual values were under 10 %, affirming the Taguchi-optimized TabNet algorithm's effectiveness in forecasting the elastic modulus of FDM 3D-printed PLA components. This investigation provides a significant advancement in additive manufacturing, introducing a precise and reliable method for predicting the mechanical properties of 3D-printed materials. © 2024 Elsevier Ltd
Publication Date: 2024
Materials Today Communications (23524928)39
Alloys are engineered materials aimed at enhancing mechanical properties. Extensive research has focused on identifying the optimal metal composition for alloys with superior tensile strength. This study validates the stiffness and strength values of an aluminum-copper alloy through a comparison with a molecular dynamics simulation. Subsequently, 100 data points were obtained from the simulation, and a deep neural network (DNN) with three hidden layers was employed. The DNN was trained, tested, and its structure optimized using the Taguchi design of experiment. The proposed DNN structures successfully predicted the maximum values of the stiffness and strength, which were further verified using molecular dynamics simulation. Notably, the results demonstrated the complete reliability of the Taguchi-designed DNN algorithm in this application. © 2024 Elsevier Ltd
Publication Date: 2025
Progress in Additive Manufacturing (23639520)
Extrusion-based additive manufacturing of thermosets and short fiber-reinforced thermoset composites is a challenging task and remains, despite recent advances, unable to fully leverage the entire design freedom offered by state-of-the-art technology due to low viscosity and solidification way of ink. This study introduces an enhanced direct ink writing (DIW) technique for effectively printing thermoset resins and corresponding short glass fiber-reinforced composites, achieved without adding any rheological modifiers and using ultraviolet (UV) curing. The proposed method utilizes time-dependent rheological control to enhance the ink's properties, offering a cost-effective and experimentally simplified approach. Experimental results suggest that the raster angle had no substantial effect on the mechanical properties, or in other words, the printed specimens behave like an isotropic material. To achieve maximum tensile properties, the ink parameters, such as fiber weight fraction, mixing time, and mixing speed, were optimized using the Taguchi design of experiment. The results showed a strong correlation between predicted and observed values, confirming the efficacy of the approach. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.
Publication Date: 2024
International Journal of Advanced Manufacturing Technology (02683768)132(3-4)pp. 1827-1842
A simple and inactive structure is able to transform into a complex and active one via four-dimensional (4D) printing. Controlling bending deformation, activation time, and temperature is crucial in 4D printing. This study aimed to comprehensively evaluate and analyze the effect of different process parameters on the bending deformation of polylactic acid (PLA) shape-morphing produced by material extrusion additive manufacturing. These parameters included layup, layer thickness, printing speed, nozzle temperature, nozzle diameter, and bed temperature. Since the bending deformation is significantly affected by the specimen wall, this study has focused, for the first time, on the simultaneous influence of process parameters and presence of a wall on the deformation. Furthermore, the study examined the influence of printing parameters on activation time and activation temperature. The results indicated that increasing the pre-strain stored in the parts led to a decrease in activation time and activation temperature. Subsequently, the Taguchi design of experiment method was used to optimize the most influential parameters on the bending deformation. The difference between the optimal predicted and the experimental deformations was less than 2%. Layer thickness, layup, nozzle temperature, and printing speed were recognized as the most effective parameters for controlling deformation, respectively. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.
Additive manufacturing (AM) technology of thermoset polymer composites has great potential to address the disadvantages of widely used thermoplastic resins in terms of processing, cost, modification of compound formulation, dimensional stability, and stress crack resistance. Whilst there are other AM processes for thermoset polymer composites, the two most common techniques; VAT photopolymerization and extrusion-based methods are discussed. This chapter deals with the basics of these two technologies and attempts to describe the limitations and advantages of each. In particular, the key features and challenges regarding both techniques are presented. Furthermore, common materials available for thermosetting AM systems are described in combination with the 3D printing of fiber-reinforced polymer composites. A description of the important parameters that enhance the performance of printed parts is provided. © 2024 Elsevier Inc. All rights are reserved including those for text and data mining AI training and similar technologies.
Publication Date: 2023
Composites Part A: Applied Science and Manufacturing (1359-835X)171
Additive manufacturing (AM) has a great potential to create complex parts and systems lighter and stronger compared to traditional manufacturing operations. So far, several polymeric materials including different types of thermoset polymers and recently fiber reinforced thermosetting composites have been used in different additive manufacturing processes. Printed parts have shown an enhanced performance compared to their counterparts made by conventional techniques. This review article presents the state-of-the-art in the field of polymer-based additive manufacturing processes employed for thermoset resins, their corresponding fiber reinforced composites, main process parameters, build strategies, and their effects on the mechanical behavior of printed parts. This paper enlightens the basics of material extrusion, vat photopolymerization, and hybrid AM processes. In particular, these techniques involve Direct Ink Writing (DIW), Frontal Polymerization (FP), Reactive Extrusion (RE), In-bath print and cure (IBPC) that fall under extrusion-based AM system, and Stereolithography (SLA), Digital Light Processing (DLP) falling under vat photopolymerization AM. © 2023 Elsevier Ltd
Publication Date: 2022
International Journal of Adhesion and Adhesives (01437496)118
Various geometric and material parameters such as adhesive thickness, adhesive overlap, adherend thickness, and composite layup may affect the strength of the joint under quasi-static loading and failure mode of bonded composite-to-composite single-lap joints (SLJs) and are investigated by previous studies. The study herein broadens these findings by looking into the effect of lamina fiber angle adjacent to the adhesive layer on the damage initiation and evolution in detail. In this regard, a composite-to-composite adhesively bonded SLJ with adherends made of E-glass/epoxy composites and [04//θ/03] (where//shows the adhesive location) layups are manufactured and tested under quasi-static tensile loading. The adhesive type is semi-flexible Araldite 2015. Experimental results show that by increasing the fiber angle from 0° to 90°, the shear stress in the adhesive layer is decreased while the peel stress is increased. In examining typical fracture interfaces for each layup configuration, a full description of failure mode assessment is obtained. In particular, the SLJ is modeled in Abaqus using cohesive elements with bilinear traction-separation law. Numerical results indicate that the bilinear cohesive law cannot model the exact load-displacement curve due to semi-flexible behavior of the epoxy adhesive, but it can predict maximum strength precisely. The failure of composite joints is significantly influenced by shear stress. © 2022
Publication Date: 2021
Journal of Manufacturing Processes (15266125)67pp. 12-22
Precision injection molding of high performance components requires primary error sources affected the molded component to be identified and isolated such that these errors can be reduced if needed. To systematically isolate and quantify the contribution of misalignment, thermal variation and component warpage to the accumulated error observed on the component, a methodology is presented and tested around an existing mold which produced parts with high dimensional variability. The mold featured two concentric guide pillars on opposite sides of the parting plane and rectangular centering block elements at three locations. Mold displacements at the parting plane were measured through the incorporation of three eddy-current linear displacement sensors. Thermal error sensitivity was investigated using FEM simulations such that the induced variability from thermal expansion and filling phase was identified and quantified. Finally, molded component warpage was isolated and quantified, again by the means of FEM simulation. The results were confirmed by using the mold on two injection molding machines to produce an array of parts whose key dimensions were measured. © 2021 The Society of Manufacturing Engineers
Jensen, M.L.,
Mahshid, R.,
D'angelo, G.,
Walther, J.U.,
Kiewning, M.K.,
Spangenberg, J.,
Hansen, H.N.,
Pedersen, D.B. Publication Date: 2019
Applied Sciences (Switzerland) (20763417)9(19)
This paper introduces two new deposition-strategies for five degrees of freedom (5DOF) and 6DOF extrusion-based additive manufacturing (AM), called the tool path projection- and parent-child-approach, respectively. The tool path projection method can be automated, and allows for the generation of concentric shells layers, which remedy geometrical deviations (known as the stair-case effect) that are typically seen in 3DOF AM processes that potentially require secondary post treatment by machining or grinding of the final part. In the parent-child approach, the designer specifies the manufacturing direction for each distinct feature, thereby helping to remove the need for support material, as well as enabling new features to be dynamically added to the part. © 2019 by the authors.
Publication Date: 2018
Precision Engineering (01416359)52pp. 201-210
Tolerance analysis provides valuable information regarding performance of manufacturing process. It allows determining the maximum possible variation of a quality feature in production. Previous researches have focused on application of tolerance analysis to the design of mechanical assemblies. In this paper, a new statistical analysis was applied to manufactured products to assess achieved tolerances when the process is known while using capability ratio and expanded uncertainty. The analysis has benefits for process planning, determining actual precision limits, process optimization, troubleshoot malfunctioning existing part. The capability measure is based on a number of measurements performed on part's quality variable. Since the ratio relies on measurements, elimination of any possible error has notable negative impact on results. Therefore, measurement uncertainty was used in combination with process capability ratio to determine conformity and nonconformity to requirements for quality characteristic of a population of workpieces. A case study of sheared billets was described where proposed technique was implemented. The use of ratio was addressed to draw conclusions about non-conforming billet's weight expressed in parts per million (ppm) associated with measurement uncertainty and tolerance limits. The results showed significant reduction of conformance zone due to the measurement uncertainty. © 2017 Elsevier Inc.
Injection moulding is characterized by high precision requirements. In particular, the demands regarding the mould plates alignment are in order of few micro meters. This research introduces a methodology to measure the misalignment in injection moulding. Eddy current sensors are used in the system to perform measurements for a whole cycle. In a long run of the mould, a comparison of mould deviation between the first and the last cycles is obtained.
Publication Date: 2016
Materials and Design (0264-1275)104pp. 276-283
Additive manufacturing is rapidly developing and gaining popularity for direct metal fabrication systems like selective laser melting (SLM). The technology has shown significant improvement for high-quality fabrication of lightweight design-efficient structures such as conformal cooling channels in injection molding tools and lattice structures. This research examines the effect of cellular lattice structures on the strength of workpieces additively manufactured from ultra high-strength steel powder. Two commercial SLM machines are used to fabricate cellular samples based on four architectures— solid, hollow, lattice structure and rotated lattice structure. Compression test is applied to the specimens while they are deformed. The analytical approach includes finite element (FE), geometrical and mathematical models for prediction of collapse strength. The results from the the models are verified with experimental data and it is shown that they agree well. The results from this research show that using lattice structures significantly reduces the strength of material with respect to solid samples while indicating no serious increase of strength compared to hollow structures. In combination with an analysis of microstructures, a description of strength analysis is obtained with respect to process parameters. © 2016 Elsevier Ltd
Additive manufacturing has shown significant improvement in material and machines for high-quality solid freeform fabrication processes such as selective laser melting (SLM). In particular, manufacturing lattice structures using the SLM procedure is of interest. This research examines the effect of cellular materials on compression strength. The specimens are manufactured additively using industrial 3D printing systems from high-strength alloy. The material has the right mechanical properties for manufacturing tool components. This includes samples with solid and lattice structures. The Compression tests are applied to the both samples while they are deformed. The flow stress curves from this research show that using cellular material significantly reduces the yield stress of the samples. This reduction compromises the efficiency of the new structure with respect to the material save.
Petersen, R.S.,
Mahshid, R.,
Andersen, N.K.,
Keller, S.S.,
Hansen, H.N.,
Boisen, A. Publication Date: 2015
Microelectronic Engineering (01679317)133pp. 104-109
A process has been developed to fabricate discrete three-dimensional microcontainers for oral drug delivery application in Poly-l-Lactic Acid (PLLA) polymer. The method combines hot embossing for the definition of holes in a PLLA film and mechanical punching to penetrate the polymer layer around the holes, after filling them with drug. Here, we demonstrate the fabrication of microcontainers with a diameter of 340 μm and a height of 50 μm. The process is temperature benign so that the compositional integrity of the drug is preserved. It also provides a good flexibility for creating different sizes and shapes of microcontainers. Finally, the process is compatible with roll-to-roll processing that could lead to low cost high volume production. © 2014 Elsevier B.V. All rights reserved.
Previous studies have described a high performance transfer press for the application in micro forming. This research extends this finding by conducting a two-stage forming process for the machine tool in order to examine the efficiency of the machine in a real multi-stage process. In particular the analysis focuses on quantifying the effect the forming force has on the elastic deflection of the machine and the tools by examining the displacement of the moving plate under loaded and unloaded conditions. The results of the measurements were used to describe the tilting effect due to the off-center loading applied to the upper tool plate.
The purpose of this research is to fabricate billets for an automated transfer press for micro forming. High performance transfer presses are wellknown in conventional metal forming and distinguished from their automation and mass production. The press used in this research is a vertical mechanical press. When using a vertical mechanical press, the material is fed as billets into the forming zone. Therefore, a large number of highly uniform billets are required to run mass production in such a setup. Shearing technique was used for manufacturing the billets. The efficiency of the shearing tool is examined in terms of volume control, circularity, dimension and sheared surface quality. The shearing tool is based on holders for both bar and cutoff. The tool is fixed in dimensions, since the dimensions of billets are fixed throughout experiments of this research. The paper presents the experimental analysis of the precision of the billets prepared by the tool.
