Kinematic and dynamic modelling for a class of hybrid robots composed of m local closed-loop linkages appended to an n-link serial manipulator

Recently, more and more hybrid robots have been designed to meet the increasing demand for a wide spectrum of applications. However, development of a general and systematic method for kinematic design and dynamic analysis for hybrid robots is rare. Most publications deal with the kinematic and dynamic issues for individual hybrid robots rather than any generalization. Hence, in this paper, we present a novel method for kinematic and dynamic modelling for a class of hybrid robots. First, a generic scheme for the kinematic design of a general hybrid robot mechanism is proposed. In this manner, the kinematic equation and the constraint equations for the robot class are derived in a generalized case. Second, in order to simplify the dynamic modelling and analysis of the complex hybrid robots, a Lemma about the analytical relationship among the generalized velocities of a hybrid robot system is proven in a generalized case as well. Last, examples of the kinematic and dynamic modelling of a newly designed hybrid robot are presented to demonstrate and validate the proposed method

Analysis of the Compliance Properties of an Industrial Robot with the Mozzi Axis Approach

In robotic processes, the compliance of the robot arm plays a very important role. In some conditions, for example, in robotic assembly, robot arm compliance can compensate for small position and orientation errors of the end-effector. In other processes, like machining, robot compliance may generate chatter vibrations with an impairment in the quality of the machined surface. In industrial robots, the compliance of the end-effector is chiefly due to joint compliances. In this paper, joint compliances of a serial six-joint industrial robot are identified with a novel modal method making use of specific modes of vibration dominated by the compliance of only one joint. Then, in order to represent the effect of the identified compliances on robot performance in an intuitive and geometric way, a novel kinematic method based on the concept of \u201cMozzi axis\u201d of the end-effector is presented and discusse

Compliance Model of Exechon Manipulators with an Offset Wrist

The stiffness of the Exechon hybrid manipulator is a crucial performance indicator as the manipulator is used as a 5-axis machine tool. Normally, the serial module of the Exechon is not included in the kinematic and stiffness analysis. In terms of kinematics, the parallel and serial modules are said to be decoupled, i.e. parallel module can be solved for position and the serial module can be used to compensate the parasitic orientation of the parallel platform. This is only possible when the serial module is a perfect spherical wrist. However, several models of Exechon technology have an offset wrist rather than a spherical one. Such an offset makes it impossible to obtain a kinematic decoupling. In all publications available in the literature, the Exechon is considered to have a perfect spherical wrist. Therefore, this paper presents the inverse kinematics and compliance model of Exechon manipulators with offset wrists. The unknown coefficients in the compliance model are determined by optimizing the model against experimental data. The resulting predictions are then compared against more experimental results to validate the model

Advances in Mechanical Systems Dynamics 2020

The fundamentals of mechanical system dynamics were established before the beginning of the industrial era. The 18th century was a very important time for science and was characterized by the development of classical mechanics. This development progressed in the 19th century, and new, important applications related to industrialization were found and studied. The development of computers in the 20th century revolutionized mechanical system dynamics owing to the development of numerical simulation. We are now in the presence of the fourth industrial revolution. Mechanical systems are increasingly integrated with electrical, fluidic, and electronic systems, and the industrial environment has become characterized by the cyber-physical systems of industry 4.0. Within this framework, the status-of-the-art has become represented by integrated mechanical systems and supported by accurate dynamic models able to predict their dynamic behavior. Therefore, mechanical systems dynamics will play a central role in forthcoming years. This Special Issue aims to disseminate the latest research findings and ideas in the field of mechanical systems dynamics, with particular emphasis on novel trends and applications

On the Mitigation of Late Stage Redesign in Mechatronics Using Integrated Approaches

RÉSUMÉ Les systèmes mécatronique combinent des éléments issus du génie mécanique, électrique, contrôle et logiciel. Due à la nature multi-domaine de ces systèmes, il est nécessaire de s’assurer d’un processus de conception optimal afin de réduire le temps et le cout de développement. De ce fait, cette thèse s’intéresse aux boucles de re-conception tard durant le processus de développement. Ces boucles peuvent être causé entre autres par des interactions négatives qui affectent la performance et l’intégration des composantes et sous-systèmes et l’incertitude dans les paramètres du système. Premièrement, cette thèse propose une nouvelle méthode de modélisation qui permet d’identifier et d’évaluer les dépendances durant les phases initiales de conception. Cette méthode est ensuite utilisée dans la création d’un index qui permet de représenter le niveau total de dépendances négative du système. L’index est ensuite utilisé dans l’évaluation multicritère, ce qui permet de choisir des systèmes étant plus faciles à concevoir. Finalement, une méthode de modélisation qui permet de considérer de façon concurrente les dépendance positive et négative est présenté. Par la suite, cette thèse propose d’utiliser les nombres flous afin de traiter l’incertitude des paramètres. En premier lieu, la thèse montre que les nombres flous peuvent être utilisé afin de simuler le comportement d’un système mécatronique sujet à de l’incertitude. De plus, une méthode de conception utilisant la simulation floue est proposée afin de concevoir les systèmes mécatronique de façon robuste. De plus, les nombres floues permettent de déterminer la stabilité du système, ce qui permet le développement d’une méthodologie de conception robuste totalement intégré, qui considère à la fois l’aspect physique et contrôle du système.----------ABSTRACT Mechatronic systems are highly integrated devices, with elements from mechanical, electrical, software and control engineering. It is thus necessary to ensure a streamlined design process to reduce development time and cost. Consequently, this thesis researches on the issue of late stages redesigns in mechatronics. The late stages redesigns may occur due to problems while integrating the different components and subsystems. Two causes of these redesigns are unpredicted negative interactions between the elements of the system, and inadequate performance due to uncertainties. To deal with the issue of negative interactions, this thesis first suggests a modeling method that enables to identify and assess negative dependencies early during the design process. It is shown that the modeling method can be efficiently used to detect dependencies that would be detrimental to the system’s performance and which may require more design effort. Then, based on this modeling method, an index representing the total level of negative dependencies present within the system is proposed. The index is shown to be able to predict decrease of performance due to the negative dependencies and can thus be used as a valuable criterion during decision making. Finally, a modeling method to handle concurrently positive and negative dependencies is suggested. This modeling method is shown to have an impact on the currently existing complexity metrics and should thus allow to better represent the reality of the design. Furthermore, to deal with the issue of uncertainties affecting the performance of the system, this thesis proposes a design methodology using fuzzy numbers. First, it is shown that fuzzy numbers can be used to model and simulate the uncertain behavior of mechatronic systems while being computationally efficient. Then a robust design methodology is presented and shown to be effective in optimizing a mechatronic system while reducing the uncertainties in the performance. Furthermore, based on the use of fuzzy numbers in the modeling of the mechatronic system, it is shown that it is possible to determine the stability of the device under uncertainties. Finally, a fully integrated robust design methodology is presented, which consider both control and design parameters selection, and which can be used to mitigate late stages redesigns due to improper performance. In sum, this thesis investigates and suggests multiple integrated design solutions to mitigate late stages redesigns in the mechatronic design process