Real-time simulation of multibody systems with applications for working mobile vehicles

This dissertation describes an approach for developing a real-time simulation for working mobile vehicles based on multibody modeling. The use of multibody modeling allows comprehensive description of the constrained motion of the mechanical systems involved and permits real-time solving of the equations of motion. By carefully selecting the multibody formulation method to be used, it is possible to increase the accuracy of the multibody model while at the same time solving equations of motion in real-time. In this study, a multibody procedure based on semi-recursive and augmented Lagrangian methods for real-time dynamic simulation application is studied in detail. In the semirecursive approach, a velocity transformation matrix is introduced to describe the dependent coordinates into relative (joint) coordinates, which reduces the size of the generalized coordinates. The augmented Lagrangian method is based on usage of global coordinates and, in that method, constraints are accounted using an iterative process. A multibody system can be modelled as either rigid or flexible bodies. When using flexible bodies, the system can be described using a floating frame of reference formulation. In this method, the deformation mode needed can be obtained from the finite element model. As the finite element model typically involves large number of degrees of freedom, reduced number of deformation modes can be obtained by employing model order reduction method such as Guyan reduction, Craig-Bampton method and Krylov subspace as shown in this study The constrained motion of the working mobile vehicles is actuated by the force from the hydraulic actuator. In this study, the hydraulic system is modeled using lumped fluid theory, in which the hydraulic circuit is divided into volumes. In this approach, the pressure wave propagation in the hoses and pipes is neglected. The contact modeling is divided into two stages: contact detection and contact response. Contact detection determines when and where the contact occurs, and contact response provides the force acting at the collision point. The friction between tire and ground is modelled using the LuGre friction model, which describes the frictional force between two surfaces. Typically, the equations of motion are solved in the full matrices format, where the sparsity of the matrices is not considered. Increasing the number of bodies and constraint equations leads to the system matrices becoming large and sparse in structure. To increase the computational efficiency, a technique for solution of sparse matrices is proposed in this dissertation and its implementation demonstrated. To assess the computing efficiency, augmented Lagrangian and semi-recursive methods are implemented employing a sparse matrix technique. From the numerical example, the results show that the proposed approach is applicable and produced appropriate results within the real-time period.

Co-creating Value For Smart Phone Operating Systems Via Virtual Discussion Forums

In the traditional way, value is created by manufacturer or producer of a product without engaging the customers. So, traditionally value creation is a monopoly in the part of a manufacturer. After gathering all the raw materials the manufacturers are inserting value to a product. And the inserted value is recognized in the time of consuming the product. In the modern time though there is traditional way of value creation but with the increase of more educated, smart, and technically sound customers the idea of value creation has changed. Now, customers are also contributing in value creation as value co-creator even before the product is consumed. This scenario has been encountered in the thesis with the main purpose of how value is cocreated in smart phone operating systems. The purpose is further divided into the following supobjectives: o What is value co-creation in smart phone operating systems? o Who participates in value co-creation in smart phone operating systems? o What are the procedures that are involved in value co-creation in smart phone operating systems? The research was conducted as a qualitative desk study by observing two of the leading smart phone operating system providers. Data has been collected from the official discussion forum of both the operating system providers. Other general concepts relating to the purpose of the study has been encountered through literature review. The research findings reveal that customers and companies both together co-create value of anticipated level when they communicate and interact with each other. However, most of the time customer to customer interactions, dialogues and discussions that come out in the core conversation help the value co-creation. The value co-creation framework sets up the customer at the main focus of value creation theory. By nullifying the inherited notion that companies only create value within its boundary and provide it to their customers in exchange of currencies. Rationally, it has been commenced that the firms are merely compromising value propositions to its customers. But the value has been co-created in a point where offerings are combined and interacted with customers’ capabilities, knowledge, resources and perceptions. This new perspective has radically altered the prospect of firms towards its customers. Typically customers are now taking part in value cocreation as a crucial member.