A Motion Planning Approach for Fabrication of Complex 3-D Shapes in a LENS� Process

This paper discusses an approach for planning the motion of the laser deposition head relative to the part for fabrication of complex 3-D shapes such as parts with overhangs, branches, and internal cavities in direct metal deposition processes such as the LENS‘ process. The proposed approach is based on slicing the solid model of the part into equal-thickness slices perpendicular to the normal build direction and formulating a motion planning strategy based on the properties of these slices. The paper discusses the four sub-approaches that are proposed to handle a variety of complex 3-D shapes parts.Mechanical Engineerin

Deep learning computer vision for robotic disassembly and servicing applications

Fastener detection is a necessary step for computer vision (CV) based robotic disassembly and servicing applications. Deep learning (DL) provides a robust approach for creating CV models capable of generalizing to diverse visual environments. Such DL CV systems rely on tuning input resolution and mini-batch size parameters to fit the needs of the detection application. This paper provides a method for determining the optimal compromise between input resolution and mini-batch size to determine the highest performance for cross-recessed screw (CRS) detection while utilizing maximum graphics processing unit resources. The Tiny-You Only Look Once v2 (Tiny-YOLO v2) DL object detection system was chosen to evaluate this method. Tiny-YOLO v2 was employed to solve the specialized task of detecting CRS which are highly common in electronic devices. The method used in this paper for CRS detection is meant to lay the ground-work for multi-class fastener detection, as the method is not dependent on the type or number of object classes. An original dataset of 900 images of 12.3 MPx resolution was manually collected and annotated for training. Three additional distinct datasets of 90 images each were manually collected and annotated for testing. It was found an input resolution of 1664 x 1664 pixels paired with a mini-batch size of 16 yielded the highest average precision (AP) among the seven models tested for all three testing datasets. This model scored an AP of 92.60% on the first testing dataset, 99.20% on the second testing dataset, and 98.39% on the third testing dataset

A new approach to teaching a mechanical systems design course

This paper discusses a new approach to teaching a senior-level mechanical systems design course at the University of Rhode Island. The MCE401 class was split into 9 teams, each with four students. Team members were selected to complement their learning styles. To each team, additional 4 students from the URI Business school were added. In the Fall semester, each team selected one of several different, product-oriented design projects or proposed their own project topic subject to certain requirements. The students were asked to perform a patent search, to critique related products, to prepare a marketing study, to propose a design of this product, and to realize their design using a 3-D solid-modeling software. At the end of the Fall semester, groups competed for funding for activities in the following Spring term that included building prototypes of their design, formulating business plans for commercialization, and applying for patent protection. The new proposed format gave students better understanding and exposure to the entrepreneurial process of product design and innovation

A new approach to teaching a mechanical systems design course

This paper discusses a new approach to teaching a senior-level mechanical systems design course at the University of Rhode Island. The MCE401 class was split into 9 teams, each with four students. Team members were selected to complement their learning styles. To each team, additional 4 students from the URI Business school were added. In the Fall semester, each team selected one of several different, product-oriented design projects or proposed their own project topic subject to certain requirements. The students were asked to perform a patent search, to critique related products, to prepare a marketing study, to propose a design of this product, and to realize their design using a 3-D solid-modeling software. At the end of the Fall semester, groups competed for funding for activities in the following Spring term that included building prototypes of their design, formulating business plans for commercialization, and applying for patent protection. The new proposed format gave students better understanding and exposure to the entrepreneurial process of product design and innovation

Motion Planning for Cladding Operations in a 5-Axis LENS� Machine

This paper presents a motion planning approach for some basic part shapes that require 5-axis motion control in a LENS machine. The paper discusses an approach that allows a cladding layer to be deposited on a cylindrical or a semi-spherical part for re-build operations. For cylindrical parts, the deposited layer could take the form of a tube, a spiral, or stepped/tappered tube. The approach allows arbitrary values for the parameters of these layers, and automatically translates the part parameters into a motion control program to run the LENS machine. The developed methodology was tested on an Optomec 850 machine, and the results were successful.Mechanical Engineerin

Integrating a Smartphone-Based Vibration Experiment into an Engineering Course

A smartphone coupled with a low-cost physical system can be used to conduct a meaningful at-home engineering experiment that provides an environment for experiential and personalized learning. The objective of this study is to improve students\u27 understanding of the response of a dynamic system through integrating an at-home experiment into a lecture-only class using a smartphone as the measurement system. The paper reports on the use of the linear acceleration sensor in smartphones to conduct an at-home experiment to measure the vibration characteristics of a cantilever beam in a junior-level, systems dynamic course. All students in the class were provided with a spring steel beam and a C-shaped clamp. The students mounted their own phone at the end of the beam, and an app was used to record the acceleration of the beam for three different beam lengths. From the experimental data, the students were asked to determine the damped natural frequency of the beam and compare it to theory. The study was performed over three years with a total of 302 students. Data analysis of the short pre and post quiz conducted with the experiment showed that the at-home experiment had a positive effect on students\u27 understanding of key concepts. Furthermore, written and verbal comments from the students showed that the students valued the learning they got from performing this experiment

A study of learning styles and team performance

This paper reports on a study that was performed over a 4-year long period in which the performance of undergraduate mechanical engineering students on a team project, enrolled in a senior mechanical systems course at the University of Rhode Island, was correlated with their learning styles as measured by the Brain Dominance Model. To measure the learning style of each student, the Brain Works program, developed by Synergistic Learning Incorporated, was used in this study due to its ease of administration and explanation of results. The students were asked to report to the instructor the two numbers that the program generated: one is a left/right brain measure and the other, an auditory/visual measure. In the first two years of this study, the 4-5 members of each team were grouped based on their learning styles score with the objective of forming teams with members whose scores are in three or more different quadrants of the left/visual plane. In the last two years, the teams were formed randomly, but the students were asked to report their learning styles scores. Data was also collected on the performance of each student in the course and in the team project. To determine if the learning styles have any correlation to the performance of the team, a correlation analysis was performed on combination of many variables some of which are exam grade, project grade, and composite learning score for the team. The results show that the competence level of the team as measured by the exam grade has the most influence on the team performance, while the learning style makeup of the team has a less pronounced effect

Modeling of flexure-hinge type lever mechanisms

A general approach for the design of flexure-hinge type lever mechanisms that are commonly used in the design of translational micro-positioning stages is presented in this paper. The paper focuses on the development of design equations that can accurately predict the behavior of such stages especially the lost motion due to hinge stretching. The development of these equations is based on a static analysis of a general configuration of a single-axis, translational, flexure-hinge type, piezo-driven micro-positioning stage using a multi-lever structure. The displacement ratio between the input and output motions of one of the levers, plus the stiffness at either end of this lever are obtained based on the analysis. The overall displacement and stiffness of the micro-positioning stage are then obtained by cascading the individual results from every lever. The developed equations include the effects of the flexure hinge bending and stretching. The developed equations were applied to design of a vertical motion micro-positioning stage. The stiffness and displacement of this stage are predicated by these equations, which are compared to the stiffness and displacement directly obtained from the finite element modeling and actual testing of the same micro-positioning stage. The comparison shows that the analytical approach gave nearly similar results (within 10%), which implies that the developed equations can accurately predict the characteristics of flexure-hinge type lever mechanisms. © 2003 Elsevier Inc. All rights reserved

An Invariant Pattern Recognition Machine Using a Modified ART Architecture

A novel invariant pattern recognition machine is proposed based on a modified ART architecture. Invariance is achieved by adding a new layer called F3, beyond the F2 layer in the ART architecture. The design of the weight connections between the nodes of the F2 layer and the cells of the F3 layer are similar to the invariance net. Computer simulations show that the model is not only invariant to translations and rotations of 2-D binary images but also noise-tolerant to these transformed images. © 1993 IEE

Modeling hysteresis in piezoceramic actuators

A major deficiency of piezoceramic actuators is that their open-loop control accuracy is seriously limited by hysteresis. This paper discusses the adaptation of the Preisach model to describe the nonlinear hysteresis behavior of these actuators. The adapted model is used to predict the response of a piezoceramic actuator to a sinusoidal input and a triangular input. The predictions are compared with experimental measurements on a stacked piezoceramic actuator. The model reproduces the hysteresis loop of the actuator to within 3% over the entire working range of 0-15 μm. This opens the possibility of incorporating the model into a control loop in order to overcome the accuracy problem. © 1995