Computer-aided design and analysis for a class of nonlinear systems

A report is presented on the results of the second benchmark control problem prepared by the Benchmark Working Group of the IEEE Control Systems Society Technical Committee on computer-aided control system design (CACSD). The problem deals with a continuous-time missile autopilot design. The purpose of this benchmark is to provide a useful measure of some of the capabilities of computer-aided control system design packages. The problem requires time simulations, eigenvalue calculations, and frequency-response plots of relatively high-order linear systems. The problem is described, and the results submitted to date are summarized. >

Computer-aided multivariable control system design for processes with time delays

Features in the design of a graphical man-machine interface for pre-processing the inputs to computer-aided control system design software are described in this paper. The primary objective is to allow the control engineer to communicate with a modem graphics workstation in a natural, familiar and friendly way, by means of block diagrams, signal flow graphs and standard mathematical text. Graphical methods for the input and output of these are described. Transformations between different system descriptions are considered which allow all algebraic manipulations and reductions to be performed on signal flow graphs. For these manipulations, rule-based methods are shown to be effective. The possibility of using symbolic computation languages for algebraic operations is also considered.

Since the emergence of Computer Aided Design (CAD) software in 1957, educators have been committed to equipping design engineering students with proficiency in the most widely employed CAD tools in the industry. In the early days, training focused on step by step instructions and understanding CAD theory. Overtime, lecturers adopted more hands-on practice, project-based learning and collaborative learning techniques [1]. The abundance of online resources and tutorials has allowed lecturers, particularly in Higher Education (HE), to focus less on training and more on theory and use of various software and techniques. Over the last decade, the number, pace and emergence of unique sub-sector software development has grown exponentially, making it difficult for educators to adopt a fixed CAD curriculum. In the early days, the dominant players in the CAD software arena until the early 2010s were Solidworks, Rhino 3D, and Autodesk Maya, each equipped with its own proprietary rendering engine. However, over the past decade, there has been a proliferation of CAD software alternatives, complemented by independent rendering engines like Keyshot, notably embraced by software applications such as Blender, Gravity sketch, and Sketchup. In particular, Blender and Rhino's Grasshopper add-on have experienced a surge in user-generated custom add-ons, broadening the array of available features and functionalities. The rapid expansion of Artificial Intelligence (AI) tools over the last two years has introduced a new layer of complexity, as tools such as Midjourney, Stable Diffusion, and Control Net have gained prominence in the industry. The exponential growth of computational tools available has presented higher education institutions with a perplexing choice regarding which CAD software to teach and the most effective pedagogical methods [2]. This complexity is further compounded by the dynamic nature of software development and the diverse career paths of students, each demanding a distinct skill set for success. This intricate situation prompts the inquiry into an approach to future-proof and tailor CAD software education to the unique requirements of each student cohort . Perhaps the same tool that advances learning can be used for future-proofing? Whilst there are examples of successful uses of AI in education in other disciplines, the inquiry using baseline data from undergraduate and postgraduate students at a world leading institution raises additional questions: • Can we design an AI tool that develops bespoke CAD learning for students? • Can this learning go beyond simple command instructions and extract higher universal principles of CAD theory? • Specifically in HE, can AI be used to create individual learning plans based on student’s interests, industry needs and ongoing advances in CAD? References : [1] Brink, Kilbrink & Gericke, 2023. Teach to Use CAD or through Using CAD: An Interview Study with Technology Teachers. International journal of technology and design education 33.3: 957–979. [2] Xie, 2018. Learning and Teaching Engineering Design through Modeling and Simulation on a CAD Platform. Computer applications in engineering education 26.4: 824–840. [3] Ye, Peng, Chen & Cai, 2004. Today's students, tomorrow's engineers: an industrial perspective on CAD education, Computer-Aided Design, Volume 36, Issue 14, 2004, 1451-1460.

Parameter Estimation of the Nonlinear Dynamics of a Thyristor Driven DC-Motor Experimental Set-Up Using HMF-Method

Applying geometric and dimensional tolerances (GD&T) to part features in computer-aided design (CAD) software is essential so that the part will function properly and to guide downstream manufacturing and inspection processes. However, it is not well characterized how CAD software implements capabilities for a designer to apply GD&T to a part. Of course, CAD software vendors do their own internal testing of those capabilities and users evaluate CAD software so that it satisfies their CAD modeling requirements. However, there has never been any rigorous public-domain testing of CAD software GD&T implementations. To improve that situation, the National Institute of Standards and Technology (NIST) has developed a system to test implementations of GD&T in CAD software. Representative part geometry with GD&T applied to features was modeled in four of the major CAD systems. Errors with semantic representation and graphical presentation of the GD&T were collected and analyzed. The testing methodology, test results, and data analysis demonstrate how well the CAD system GD&T implementations perform. The testing project results can be used as a basis for future testing, methods, and standards to evaluate defects in GD&T applied to part features.

We have developed a novel software package which is able to simulate the performance parameters of the solar cells based on diffusion process parameters as well as finger-bus design parameters. An algorithm for computer aided design (CAD) incorporated in this software package is useful for designing and optimizing the finger-bus dimension for optimum solar energy harvesting. The CAD algorithm of this software package can save the optimized finger-bus design in a .dxf format which can then be directly used as layout for mask making of the metallization layers using screen printing, CMOS based lithography or e-beam writer. The .dxf format file generated by our software package can also be viewed using other CAD softwares such as AutoCAD, L-Edit, etc. This software package also simulate the sheet resistivity of the doped poly-silicon layer based on the process parameters — POCl 3 diffusion temperature, duration of POCl 3 diffusion reaction, annealing temperature and annealing duration. This research paper presents the new algorithm incorporated in the novel software as discussed above as well as the optimization of the process parameters and finger-bus design.

Evaluation of the virtual cement gap parameter of different CAD software programs in designing a single crown restoration: An in vitro study

This paper describes a methodology for automation of measurements in Computer-Aided Design (CAD) software by enabling the use of supervised learning algorithms. The paper presents a proof of concept of how dimensions are placed automatically in the drawing at predicted positions. The framework consists of two trained neural networks and a rule-based system. Four steps compound the methodology. 1. Create a data set of labeled images for training a pre-built convolutional neural network (YOLOv5) using CAD automatic procedures. 2. Train the model to make predictions on 2D drawing imagery, identifying their relevant features. 3. Reuse the information extracted from YOLOv5 in a new neural network to produce measurement data. The output of this model is a matrix containing measurement location and size data. 4. Convert the final data output into actual measurements of an unseen geometry using a rule-based system for automatic dimension generation. Although the rule-based system is highly dependent on the problem and the CAD software, both supervised learning models exhibit high performance and reusability. Future work aims to make the framework suitable for more complex products. The methodology presented is promising and shows potential for minimizing human resources in repetitive CAD work, particularly in the task of creating engineering drawings.

It has been always a challenge to grade and assess the students’ CAD (Computer-Aided Design) three-dimensional models in the class. The high number of the files and complexity of models make the task time-consuming and tedious many times. For example, even opening and closing each CAD file takes a lot of time. When hundreds of CAD models need to open and verified, it takes more than one hour to finish the task. The work has been done to simplify this task and make it easy using Commercial CAD software’s API (Application Programming Interface), which can be used to automate and customize the CAD software. The API contains hundreds of functions that you can call from Visual Basic for Applications (VBA), VB.NET, Visual C#, Visual C++ 6.0, and Visual C++/CLI. These functions provide direct access to CAD functionality such as opening a file, check the important physical properties of three-dimensional models. Custom API program has been programmed for the task. The custom program executes the internal commends in CAD software and retrieve the data you need from each CAD file automatically. The program opens the multiple CAD files in the folder and check each file’s physical properties and save the information in MS Excel for the review. The program checks the volume (w.r.t the given coordinates) in two standard units (English and S.I. Units), the creator of model (to prevent the plagiarism) and degrees of sketch. In this paper, the following topics will be discussed and presented. 1) The problem with manual grading and assessment, 2) History and background of API functionality in commercial CAD software, 3) Examples of simple source code for API usage, 4) Running example of the API program for the given task, 5) Comparison between manual assessment and automatic assessment using API in terms of spent time. 6) Future improvement with API program. Actual demonstration of the program will be given during the presentation.

This study set out to compare the three-dimensional (3D) trueness of crowns produced from three types of lithium disilicate blocks. The working model was digitized, and single crowns (maxillary left second molar) were designed using computer-aided design (CAD) software. To produce a crown design model (CDM), a crown design file was extracted from the CAD software. In addition, using the CDM file and a milling machine (N = 20), three types of lithium disilicate blocks (e.max CAD, HASS Rosetta, and VITA Suprinity) were processed. To produce a crown scan model (CSM), the inner surface of each fabricated crown was digitized using a touch-probe scanner. In addition, using 3D inspection software, the CDM was partitioned (into marginal, axis, angular, and occlusal regions), the CDM and CSM were overlapped, and a 3D analysis was conducted. A Kruskal–Wallis test (α = 0.05) was conducted with all-segmented teeth with the root mean square (RMS), and they were analyzed using the Mann–Whitney U-test and the Bonferroni correction method as a post hoc test. There was a significant difference in the trueness of the crowns according to the type of lithium disilicate block (p < 0.001). The overall RMS value was at a maximum for e.max (42.9 ± 4.4 µm), followed by HASS (30.1 ± 9.0 µm) and then VITA (27.3 ± 7.9 µm). However, there was no significant difference between HASS and VITA (p = 0.541). There were significant differences in all regions inside the crown (p < 0.001). There was a significantly high trueness in the angular region inside the crown (p < 0.001). A correction could thus be applied in the CAD process, considering the differences in the trueness by the type of lithium disilicate block. In addition, to attain a crown with an excellent fit, it is necessary to provide a larger setting space for the angular region during the CAD process.

This study investigates the impact of Project Based Learning (PBL) integrated with Computer Aided Design (CAD) software on improving technical drawing skills among vocational high school students. The experimental design involved two groups: an experimental group that received PBL based instruction using CAD software, and a control group that followed traditional instructional methods. The results revealed a significant improvement in the technical drawing skills of the experimental group, as indicated by higher post-test scores compared to the control group. These findings suggest that PBL, when coupled with CAD tools, fosters active learning, critical thinking, and enhances students' ability to visualize and create accurate technical drawings. Additionally, the project-based approach promoted collaboration, real world problem solving, and digital literacy, key competencies in vocational education. The study also identified a substantial effect size (Cohens d=2.97), emphasizing the significant educational impact of the PBL CAD integration. Despite the promising results, the study highlights limitations in terms of generalizability due to the single school sample and suggests further exploration of affective and behavioral outcomes in future research. In conclusion, the integration of PBL and CAD software represents an effective pedagogical strategy for improving technical drawing skills and preparing students for the demands of the modern workforce.

Three-dimensional CAD (Computer Aided Design) software can be used to analyze phenomena related to movement such as vibration and friction. But this requires knowledge for handling material properties and uses special three-dimensional CAD functionality. For these reasons, analysis based on three-dimensional CAD of phenomena is greatly influenced by skill level in model design and enormous time if required due to processing of analysis. Therefore, it is difficult to treat as an auxiliary tool for analysis. Also, various software exist as three-dimensional CAD, but each software varies in method of use. In addition, automatically obtained finite element mesh data in analysis differs depending on software. Therefore, even with the same model, it is difficult to analyze under the same conditions and to obtain the same result [14]. In this paper, we will study the method for analyzing the lubrication phenomena. From this study we will propose a method easy even for beginners, and show that the analysis method is simple and quick and reduces the burden on the designer.

To evaluate the design and manufacture accuracy of a domestic computer aided design (CAD) and computer aided manufacture (CAM) system, and to compare it with similar foreign products. Thirty models of posterior-teeth-single-crown preparations were collected, and STL data of these preparations was collected by Denmark 3Shape scanner. Three copings were made for each preparation, the one designed and manufactured using commercial CAD/CAM system (3Shape CAD software and Wieland T1 CAM equipment) was assigned into control group T0, the one designed and manufactured using domestic CAD software (developed by Peking University School and Hospital of Stomatology and Nanjing University of Aeronautics and Astronautics) and Wieland T1 CAM equipment was assigned into experimental group TCAD for design accuracy evaluation, and the one designed and manufactured using 3Shape CAD software and domestic CAM equipment (developed by Peking University School and Hospital of Stomatology, Tsinghua University and ShanDong XinHua Incorporated Company of medical apparatus and instruments) was assigned into experimental group TCAM for manufacture accuracy evaluation. Finally, the marginal fitness were compared and evaluated by using 3D & Profile measurement microscope laser. The marginal fitness of TCAD was 27.98 (19.10, 46.57) µm in buccal, 32.67 (20.65, 50.82) µm in lingual, 27.38 (22.53, 52.61) µm in mesial, 29.50 (22.68, 53.65) µm in distal; of TCAM was 21.69 (15.87, 30.21) µm in buccal, 18.51 (13.50, 22.51) µm in lingual, 19.15 (15.42, 26.89) µm in mesial, 22.77 (18.58, 32.15) µm in distal; and there were no statistical differences compared with T0 [20.16 (17.16, 48.00) µm in buccal, 21.51 (17.05, 28.31) µm in lingual, 23.54 (17.89, 30.04) µm in mesial and 23.94 (17.93, 28.19) µm in distal] except lingual data of TCAD. The design and machining precision of this domestic CAD/CAM system is at the same level of those comparable foreign products.

This paper describes a structural design system for 3D drawing dies based on functional features using a minimum set of initial information. In addition, it is also applicable to assign the functional features flexibly before accomplishing the design of a solid model for the main parts of a drawing die, such as upper die, lower die, and blank holder. The initial information includes blank sizes, work strokes, die faces, punch open lines, and press data. The proposed system integrated the design knowledge of drawing die into functions of 3D computer-aided design (CAD) software to automate design and to shorten design time. This design system is constructed on a PC and integrated with a Pro/ENGINEER CAD system including feature selector, shape calculator, model generator, design coordinator, and user interface. The proposed system is demonstrated using the example of designing a drawing die for the roof panel of a vehicle within 1 h. The results reveal that it can dramatically improve the design quality and can save both time and costs with excellent design quality.