Mitchel Keil

Validation of a non-linear mathematical model for predicting the shape of brake hoses in automotive applications

It is a challenge to depict the shape of flexible components in solid modeling software. This is because flexible components in an automobile are subject to large elastic deformations during the movement of the rigid components to which they are attached. The principles of computation of the orientation of entities in a simplified coordinate system, vector mathematics, the file I/O features and structured C++ programming were used to view the rubber hose in CAD after modeling the hose using simulation software. The deviations of the hose shape at 0°, 90°, and 180° twist position obtained from the non-linear mathematical model and the actual location of the real hose obtained by using ATOS II scanning equipment were reduced by modifying various parameters. At the end of the trials the mean deviation was below 1 mm at the 0° position and below 6 mm at the 90° and 180° twist positions. A regression analysis was performed for generalization of the force deformation values characterizing the non-linear behavior of off-axis elements. This analysis makes this modeling technique applicable for predicting the shape of hose lengths in the range of 227.8— 2474 mm between any two attachments in space. Subsequently, the regression model was used to predict the hose shape for a different length. The results show that non-linear model with off-axis elements predicts the hose shape much more accurately than the linear model with beams.

Reducing lead time for modeling in CAD simulation softwares

Flexible components, such as rubber hoses, are subject to large elastic deformations during movement of the rigid components to which they are attached. Currently, there is no inherent capability in any solid modeling software to accurately depict the shape of the hose between any two attachment points. Keil (2001) made the hose model in ADAMS/View simulation software. Keil (2002) stated that it is a very time consuming and cumbersome process to set up the model with the flexible beams and its associated joints for modeling of a flexible body without any user errors. This paper presents a method to automatically build a flexible element model using the principles of spatial orientation and vector mathematics. These accurate mathematical principles would maintain the precision in the flexible element model as suggested by Keil while reducing the time for building a hose model to minutes from hours

Experimental Validation of Computer Simulation of Deformations in Hydraulic Hoses

Nowadays in academics and industry, where multiple computer-based tools are being employed for design and analysis of engineering systems, it is of chief importance to provide to the user of such software tools information about the importance of validation in a lab-setting. It can be said that it is even more important in academics because students are at the initial phase of their engineering formation. Towards that end, a project involving flexible elements, such as hoses and cables, was utilized to get students involved in a validation exercise. Flexible elements are absolutely essential to the safe and successful operation of any vehicle, but they are often difficult to design and define because they are subject to large elastic deformations and because of their potential collisions with other components. This combination of factors leaves flexible elements to be rushed into production near the end of a design cycle. Therefore, in collaboration between industry and academia, a CAE-based scheme has been developed and has been implemented as a software tool to assist in the design (routing) of flexible components. For validation purposes, a group of four students in a Capstone Design Course were asked to apply Reverse Engineering (RE) techniques to measure points along an actual hose and enter those points into the simulation software for comparison and validation of the model. This validation process is the work presented in this manuscript. Keywords— Hoses, validation, deformations. Digital Object Identifier (DOI): http://dx.doi.org/10.18687/LACCEI2015.1.1.252 ISBN: 13 978-0-9822896-8-6

A Method for Precise Placement of Hose Models

A method is presented for precise mounting of a hose model with any specified twist. Once mounting points and directions are specified, a hose of a specified length can be developed using discrete beams. A divide and conquer approach is employed to position, orient, decouple the free end of the hose model in a twist free state that is then twisted to a specified angle. The development of the kinematic elements necessary to do this is presented. Some Cosserat models have been shown to branch into multiple solutions while the method presented here has always converged to the minimum energy solution. The method for linking the hose model to other linkages is discussed as well one common error committed by users in implementing the link. In order to model the torsional properties of the hose, the torsional stiffness must be modified. A method for doing this using digital scans is discussed. Failure to consider preset and hysteresis of the hoses can cause considerable error in predicting interference as is demonstrated. Simply taking the mount orientations out of a common plane can cause significant stress to build up in the model from torsional coupling during a simple linear translation.

On the commutativity of sequential finite rotations

Non-commutativity of finite rotations is a fundamental issue that needs to be addressed in mathematical models dealing with sequential finite rotations. Comprehending rotational motions required to orient a rigid link or associated reference frames in a three-dimensional space can be quite challenging for beginning students. In this paper we present the problem of non-commutativity of finite rotations and a constraint to allow their commutativity. The constraint, in the form of a chain rule, consists of a lemma for forward and backward propagation of the prescribed rotations. The proposed scheme has been implemented using a commercial graphics package for visual demonstration of a rigid body going through three identical finite rotations but in different sequences. The unique final orientation of the body in each of the cases confirms the commutative nature of the constrained rotations. Using this method, sequential finite rotation becomes easy to comprehend and can be used as a tool for learning the concepts associated with finite rotations as well as for kinematical analysis involving sequential rotations.