The past and future of sustainable concrete: A critical review and new strategies on cement-based materials

Using industrial robots as machine tools is targeted by many industries for their lower cost and larger workspace. Nevertheless, performance of industrial robots is limited due to their mechanical structure involving rotational joints with a lower stiffness. As a consequence, vibration instabilities, known as chatter, are more likely to appear in industrial robots than in conventional machine tools. Commonly, chatter is avoided by using stability lobe diagrams to determine the stable combinations of axial depth of cut and spindle speed. Although the computation of stability lobes in conventional machine tools is a well-studied subject, developing them in robotic milling is challenging because of the lack of accurate multi-body dynamics models involving joint compliance able of predicting the posture-dependent dynamics of the robot. In this paper, two multi-body dynamics models of articulated industrial robots suitable for machining applications are presented. The link and rotor inertias along with the joint stiffness and damping parameters of the developed models are identified using a combination of multiple-input multiple-output identification approach, computer-aided design model of the robot, and experimental modal analysis. The performance of the developed models in predicting posture-dependent dynamics of a KUKA KR90 R3100 robotic arm is studied experimentally.

Modelling the dynamics of industrial robots for milling operations

Research trend of the application of information technologies in construction and demolition waste management

Robotic belt grinding of the leading and trailing edges of complex blades is considered to be a challenging task, since the microscopic material removal mechanism is complicated due to the flexible contact state accompanied with greatly varying curvature that finally affects the machined profile accuracy. The resulting poor accuracy of blade edges, to a great extent, is attributed to the trajectory planning method which less considers the dynamics. In this paper, an iso-scallop height algorithm based on the material removal profile (MRP) model is developed to plan the tool paths by taking into consideration the elastic deformation at contact wheel-workpiece interface. An improved constant chord-height error method considering the influence of elastic deformation is then proposed to adaptively plan the grinding points according to the curvature change characteristics of the free-form surface. Based on these two steps, a MRP model based adaptive trajectory planning algorithm is constructed to enhance the profile accuracy facing the robotic belt grinding operation. Simulation and experimental results demonstrate the effectiveness of the proposed trajectory planning algorithm for the robotic belt grinding of blades from the perspectives of surface roughness, profile accuracy and processing efficiency. Particularly this technology serves to solve the problem of over-cutting at the blade leading and trailing edges.

An adaptive trajectory planning algorithm for robotic belt grinding of blade leading and trailing edges based on material removal profile model

Critical review of real-time methods for solid waste characterisation: Informing material recovery and fuel production.

Influence of the addendum modification on spur gear efficiency

Quality assessment for recycling aggregates from construction and demolition waste: An image-based approach for particle size estimation

Nowadays, with the large use of robot manipulators in the most different fields of industrial production, two main aims must be commonly reached: robot dynamic behavior improvement and end-effector position errors reduction. For a N DOF robot arm, in case of specific applications such as milling manufacturing, one of the main source of end-effector position errors can be identified with joint compliances. This aspect, well known in literature, has been confirmed by experimental tests and measurements carried out on a specific robot assigned to non-standard milling manufacturing of marble objects (sculptures realization). To approach and analyze this issue the authors chose the multibody simulation environment. Hence, the authors developed a parametric modelling procedure that, by determining the robot characteristics through CAD model and technical data sheet investigation, provides reliable multibody dynamic models of generic N DOF robot arms. In this modelling approach the robot geometry construction is based on a standard strategy typical of this research field (i.e. Denavit-Hartenberg, Veitschegger-Wu). The developed procedure enables to obtain robot representation at various complexity levels according to the number of modelled robot components and actuation typology (Motion laws defined both in displacement or applied torque). Eventually, for a specific test case, the authors were able to correctly simulate the robot dynamic behavior, as it was demonstrated by numerical/experimental comparison. In this way the influence of the joint compliance behavior and actuator rotational inertia effects on end-effector position accuracy was analyzed.

Multibody modelling of N DOF robot arm assigned to milling manufacturing. Dynamic analysis and position errors evaluation

Nowadays, in the field of robotic, one of the most important objectives is to reduce robot error positioning and improve its dynamic behaviour. One of the main source of error in end effector positioning is due to the joint compliance: robot joint components under operating conditions can be deformed as a function of their stiffness/damping properties. Generally, for industrial robots, harmonic drive gearings are used, their principal characteristics are high transmission ratio and law weight, on the other hand, to realize high transmission ratio, harmonic drive gearings work on inner gear elastic deformation, conferring to the robot joints an excessive compliance that, in some robot applications, cannot be neglected. In this research activity multibody modelling and simulation approach has been used to analyse joint compliance influence on robot position accuracy. The principal aim of this work was the formulation of a modelling procedure that starting from classical robots modelling approach (i.e. Denavit Hartenberg) defines an universal database and a parametric modelling procedure that allows the designer to use any multibody commercial codes to analyse anthropomorphic robots considering or not the compliance effect. All the procedure was developed and managed into a numerical code environment (Matlab/Simulink).An example of commercial anthropomorphic robot was considered by assuming its principal kinematic and dynamic characteristics. Parametric models of the robot have been developed in two different multibody modelling environments (Simmechanics, Adams/View). Moreover the models structure has been built in order to control the robot movements both in motion (open loop) or in force (closed loop). In this case they are interfaced with Simulink code in a so called co-simulation approach that allows to developed a generic control system and test it by using one or more models, less or more refined.Copyright © 2013 by ASME

Parametric Multibody Modeling of Anthropomorphic Robot to Predict Joint Compliance Influence on End Effector Positioning

Sommario Il presente lavoro analizza la problematica della modellazione e simulazione dinamica multicorpo di robot antropomorfi multi link. Obiettivo dell’attivita e quello di definire una procedura di modellazione parametrica che potesse svolgere la sua funzione a vari livelli di complessita pur mantenendo una comune strategia, propria di questo settore di ricerca (es. Denavit-Hartenberg, Veitschegger-Wu), e quindi utilizzabile a fronte di qualsivoglia codice di modellazione e simulazione. Questa procedura di modellazione prevede la possibilita di inserire le cedevolezze ridotte ai giunti nonche l’influenza inerziale dei motori. In aggiunta, con una approccio di cosiddetta co-simulazione, il robot e inserito in un loop retroazionato guidato da un codice numerico di simulazione, universalmente adottato per questi scopi (Simulink). Quindi la metodologia di modellazione e stata dapprima verificata mediante confronto numerico/numerico adottando due codici commerciali e poi mediante confronto numerico/sperimentale per uno specifico robot.

Stefano Baglioni

Papers

Influence of the addendum modification on spur gear efficiency

Quality assessment for recycling aggregates from construction and demolition waste: An image-based approach for particle size estimation

Multibody modelling of N DOF robot arm assigned to milling manufacturing. Dynamic analysis and position errors evaluation

Parametric Multibody Modeling of Anthropomorphic Robot to Predict Joint Compliance Influence on End Effector Positioning

Experimental and numerical validation of multibody models for anthropomorphic robot