AboutIntroductory engineering courses within large universities often have annual enrolments exceeding several hundreds of students, while MOOCS and online classes have even larger classes. It is very challenging to achieve differentiated instruction in classrooms with class sizes and student diversity of such great magnitude. In such classes, professors can only assess whether students have mastered a concept by using multiplechoice questions. However, in a multiple choice scenario, students only have to identify the answer rather than create the answer, and the feedback received is only of a binary nature (right or wrong). Additionally, a growing concern among engineering educators is that students are losing both the critical skill of sketched diagrams and the ability to take a real system and reduce it to an accurate but simplified freebody diagram (FBD). Mechanix is a sketchbased deployed tutoring system for engineering students enrolled in statics courses. Mechanix not only allows students to handdraw solutions with planar truss and free body diagrams, just as they would with pencil and paper, but it also checks the student’s work against a handdrawn answer entered by the instructor. It uses sketch recognition to determine both the component shapes and features of the sketched diagram and the relationships between those shapes and features. Mechanix then uses those relationships to determine whether a student’s work is correct and why it is incorrect, enabling Mechanix to return immediate personalized feedback to the student otherwise not possible in large classes. Additionally, because sketching is the preferred mode of problem solving for many professional engineers, producing a tool that utilizes sketching should increase the transfer of skills from the classroom to the real world. Finally, the iterative correction process facilitates student learning. Preliminary results suggest that Mechanix increases homework motivation in struggling students, and have shown that Mechanix is as effective as paperandpencilbased homework for teaching method of joints truss analysis. Focus groups have revealed that students believe Mechanix enhances their learning and that they are highly engaged while using it. Currently, Mechanix can correct three different types of static homework problems: 1) Standard truss problems requiring calculations of method of joints, 2) Freeform free body diagrams, and 3) Creative Design problems. In creative design mode, the student must think creatively to create a viable truss that abides by the constraints. Creative design mode offers an infinite number of possible solutions for the student, and thus presents an interesting recognition problem. Additionally Mechanix contains three different interfaces: 1) the student interface, where the student answers the problem, 2) the instructor question creation interface, where the instructor enters the problem, and 3) the instructor review mode, where the instructor reviews the existing solutions (Figure 5 shows a mockup). To add questions, the instructor simply types the question, uploads an image, draws the answer, and types in the numerical answers. The drawn answer is then compared to the student’s answer for correction. Because the student needs to know where he or she is wrong, Mechanix performs sophisticated analysis on the student’s solution in an attempt to determine where the student has gone wrong. In the case of creative design mode, no solution is drawn, instead only constraints are specified, and Mechanix then uses these constraints to grade the student’s solution. Two types of feedback are given, that of a simple dropdown box, and that of a complete checklist for them to follow. We provide two types of feedback so that the instructor can provide more feedback on initial problems and less later, scaffolding the feedback. 



Download & Try It!User: studentTest / Pass: studentTest User: adminTest / Pass: adminTestDownload the Tutorial! 

Instructor ModeThe instructor can enter answers by drawing the truss or free body diagram and forces. The instructor writes the problem text and can enter a picture related to the problem. There are equation boxes for entering the necessary equations for the answer, and there are panels for entering values of reaction forces, member forces, other input/output forces, and any other extra answers that might not be part of the diagram. The instructor can create multiple assignments and multiple problems per assignment. 

Student ModeOnce a student logs in, he or she can select an assignment and begin working. The student will read the problem and proceed to draw the corresponding diagram. The student can then use the pullout notepad to do scratch work in order to obtain the necessary equations and answer values. Then the student will enter the answers into the appropriate answer boxes. 

General RecognitionAs the user clicks and drags the mouse or tablet pen across the screen, a series of points are registered that form strokes. The program will recognize trusses, arrows, doubleended arrows, axes, and the letters x and y. The power set of all the strokes on the screen are analyzed to determine if any particular combination of strokes forms one of the recognizable shapes. If a shape is recognized, it will become highlighted when the user pans the mouse over it. 

Truss RecognitionA truss is a complex shape that can be constructed from a combination of polygons that share common sides. Recognition of trusses is more complicated than recognition of the other shapes handled by the program. Instead of analyzing combinations of strokes, recognition is based on the detection of intersection points. A shortest path algorithm is used to find the smallest possible polygons that can be formed by a set of intersection points. If any of these polygons share an edge with another polygon, they are combined into a truss. 

Answer CheckingAt any point in time, the student can check his answer by pressing the large check button. The program will compare the student's diagram to the instructor's answer diagram and state anything the student is missing or has wrong. It will also compare the equations and the other answers by comparing the value and units of each answer. 

Use Mechanix in YOUR ClassroomTo obtain usernames and passwords for you and your students, email us at mechanix_support@googlegroups.com. 

Resources and linksMechanix a how to.mp4NSF TUES PI conference.pptx mechanixwithinstructormode.mp4 
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Warning: mysqli_query() expects parameter 1 to be mysqli, boolean given in /home/faculty/hammond/web_home/mechanix.php on line 2562020  TAMU Undergraduate Excellence in Research Award Benton Phillipy Guess, TAMU CSE Departmental Award  
2020  CRA Outstanding Undergraduate Researcher Honorable Mention Benton Phillipy Guess, NSF Computing Research Association  
2015  Best Poster at 2015 ACM International conference on intelligent user interface Dr. Tracy Hammond, Dr. Michael Helms, Dr. Julie Linsey, Trevor Nelligan, Seth Polsley, Jaideep Ray, Mechanix: A SketchBased Educational Interface  
2014  CRA Outstanding Undergraduate Researcher Award Finalist David Turner, NSF Computing Research Association  
2014  2nd Place TAMU Student Research Week Graduate Research Poster in Engineering/Architecture Raniero Lara Garduno, Larry Powell, Enhancing Mechanix  Interface and Algorithms  
2014  2nd Place TAMU Student Research Week Graduate Sigma Xi Award for Interdisciplinary Research Raniero Lara Garduno, Larry Powell, Enhancing Mechanix  Interface and Algorithms  
2013  CRA Outstanding Undergraduate Researcher Honorable Mention David Turner, NSF Computing Research Association  
2013  1st Place TAMU Student Research Week (SRW) Graduate Research Poster in Computational Sciences Dr. Stephanie Valentine, Mechanix  A SketchBased Tutoring System for Statics Courses  
2012  IAAI Innovative Applications of AI Deployed Application Award Dr. Tracy Hammond, Dr. HongHoe (Ayden) Kim, Wenzhe Li, George Lucchese, Dr. Stephanie Valentine, Mechanix: A SketchBased Tutoring System for Statics Course  
2012  1st Place TAMu Student Research Week Undergraduate Research Oral in Computational Sciences David Turner, Creative Design in Mechanix (award: $300) 