TEACHING INTRODUCTORY PROGRAMMING, PROBLEM SOLVING AND INFORMATION TECHNOLOGY WITH ROBOTS AT WEST POINT

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1 TEACHING INTRODUCTORY PROGRAMMING, PROBLEM SOLVING AND INFORMATION TECHNOLOGY WITH ROBOTS AT WEST POINT Jerry Schumacher 1, Don Welch 2, David Raymond 3 Abstract As part of an ongoing initiative to continually revise and improve its introductory computer science courses, the Electrical Engineering and Computer Science Department at the United States Military Academy has added the use of LEGO Mindstorm robots as part of the active-learning environment used to teach Information Technology IT and programming basics. It is critical for the Army and the Nation that its future leaders understand and are capable of taking advantage of IT. All cadets at the United States Military Academy at West Point are required to take a course on IT and problem solving using computer programming. This course is an important first, and sometimes only, opportunity to expose undergraduate students to technology and concepts that will be a part of their daily lives and future careers. The LEGO Mindstorm robots are used in the introductory computer science course to teach fundamental computer programming concepts and introduce the concepts of autonomous vehicles, embedded computer systems and computer simulation. The positive short-term impact on the students taking the course has been substantial and while the long-term impact has yet to be measured, it also has the potential to be substantial. Members of the faculty at West Point developed a computer simulation of the robot environment as well as a Java programming language translator for the LEGO programmable brick, called the RCX. These two tools are combined into a unique programming and teaching environment that we named Jago. Jago enables the robots and robot simulator to be used to teach fundamental programming concepts visually, which some students can more easily grasp and all are clearly excited to use. Based on these results we have incorporated Jago into the core IT course taught at West Point. Index Terms Active learning, autonomous vehicle, Java programming, simulation, robot INTRODUCTION The United States Military Academy is focused on educating graduates to defend the interests of the country. While the last 50 years have seen a direct threat to the United States itself in the form of nuclear weapons, the probability of such an attack is currently very small. In recent years there has been a growth in probability of attack on the United States itself. Principle among those threats is cyberattack. In addition, the world is undergoing a revolution in military affairs. The influence of IT on the battlefield is profound. The military officer without a good grasp of IT may find himself as out of place on the 21 st century battlefield as the Polish horse cavalry found itself in the opening days of World War II. West Point must produce leaders capable of exploiting advances in IT to insure America s defense. All first year cadets at the United States Military Academy are required to take a semester course on Information Technology, a large portion of which is devoted to problem solving using computer programming. For most, this is the only IT course they will ever take. The purpose of the course is twofold: 1) to teach and apply a problem solving methodology using the programming primitives 2) teach them how to learn about new IT and its uses. We believe that it is important for all graduates to understand the programming primitives: selection, iteration and sequence. It is not only important because students will have to apply algorithm concepts using many different tools (like Excel and MathCad) throughout their lives, but because it s hard to fully understand IT without a basic understanding of what makes IT different from other technology. The course is called Introduction to Computing and has two versions: the basic version, CS105 and the advanced version, CS155. Students are placed in CS155 based on their background with computer science and programming as well as an advanced placement test given before their freshmen semester starts. These courses have been undergoing revision over the last two years [1] to improve not only the quality of the instruction but their applicability to cadet and officer needs. The programming language has 1 Jerry Schumacher, United States Military Academy, Department of Electrical Engineering and Computer Science, West Point, New York jerry.s@computer.org 2 Don Welch, United States Military Academy, Department of Electrical Engineering and Computer Science, West Point, New York dd2354@exmail.usma.edu 3 Dave Raymond, United States Military Academy, Department of Electrical Engineering and Computer Science, West Point, New York dd5372@exmail.usma.edu F1B-2

2 been updated to Java and increased emphasis has been placed on active learning, hands-on exercises, and using technology and Java packages. This course, as most courses at West Point, places heavy emphasis on active learning. Because this is not designed to serve as the first course for engineers and comp uter scientists, our approach to programming is different from the traditional approach. We emphasize the algorithmic primitives at the expense of the programming language features that facilitate the construction of useful programs. We also try to tie the IT concepts of the course into the programming lessons to reinforce the understanding of IT [1]. Java was added as the programming language for problem solving because of the ease with which it lends itself to simple GUI programs which are familiar to most freshmen. The use of prewritten Java classes with GUI interfaces integrated into student programs makes it easier to draw the analogy between the commercial programs the students use and the ones they create during class as well as the more complex homework programs. The reasoning for integrating LEGO robots into the course is similar. Students who are predisposed to computer science and engineering usually have more aptitude for understanding the abstract structure of an algorithm. For students that will be majoring in the humanities and social sciences, these concepts are difficult to visualize even with the use of graphical user interfaces (GUI). We have discovered that using robots, students can understand algorithms through the motion of a robot because it is easier to visualize. In addition, using robots in our environment brings two peripheral advantages to the algorithmic concept. The first is the introduction of autonomous vehicles and embedded code. Up to this point most of our students did not consider embedded code. In reality, even the next version of the infantry rifle will have thousands of lines of code embedded inside. Exposure to embedded code is part of the IT curriculum. Most of our students arrive at West Point not understanding the difference between a remotely controlled device and a truly autonomous device. This is another IT learning objective with which students get handson experience. Finally, simulation is a critical military technology. Simulation for many reasons is taking a large role in all aspects of the military from system development, through training and decision support. Working with a simulation and the actual robot gives them an important exposure to this technology. The course is designed to integrate algorithms into IT education. We teach the algorithmic primitives of sequence, selection and iteration using HTML and Java. Students can better visualize these primitives by watching the movement of a robot as opposed to interacting with a program executing on a general-purpose computer. We developed a Java-like interface to the Lego Mindstorms RCX that allows us to teach programming through both the Java GUI and Lego robots. We use a simulator to reinforce IT concepts and to reduce the logistical burden associated with giving students robots kits with over 750 pieces. We call the environment which includes the language, simulator, development environment and interface to the RCX Jago. JAGO ENVIRONMENT Lego Mindstorms Description The LEGO Mindstorm kits are sold in computer superstores, toy stores and discount stores for under $200 a kit and extra parts are available on-line. The kit includes the RCX brick (which, at its heart, is a Hitachi H8/300L processor), motors, touch and light sensors as well as an IR attachment for your PC to download to the RCX brick. While the LEGO programming environment is ingenious in its design for children ages 12 and up it does not provide enough flexibility to teach undergraduate students. As a result, the authors created a new environment called Jago, which enables programming in Java as well as enabling a simulation of the robot. Jago Programming Language Jago is a subset of Java with a number of pre-defined methods that make programming the robot less tedious. The Jago programming environment allows programs written in a subset of Java to be run in a virtual environment or be converted to Not Quite C (NQC) and compiled for execution by the Lego Mindstorms RCX. This environment allows students to create and test their robot control programs without access to a Lego Robot in a virtual world created by the simulator after which they may conduct final testing and evaluation of their work on a Lego Robot in the physical world. A Jago program is a sub-class of the Task Class, which is provided in the Jago environment. The Task Class contains the code that interfaces with the RCX as well as robot primitives that take the tediousness out of programming the robot. The result is that the students employ the algorithmic primitives in the form of the Java control structures (if statements, for loops, while loops) that include calculations and method calls to run the robot. Language Translation To run Jago programs on the Lego robot, we must first convert them to a language that can be compiled into a form that can be downloaded to the RCX. The language we use is Not Quite C (NQC) developed by Dave Baum [2]. We wrote a language translator that would convert code from our Jago language to NQC. The NQC program is then compiled using the NQC compiler and downloaded to the RCX (figure 1). F1B-3

3 FIGURE. 1 JAGO PROGRAM DEVELOPMENT Included below is a sample Jago program that causes the robot to go forward until it hits a wall then backup, turn right and go towards another wall, repeating this process four times. The annotations in the code should be sufficient to explain what each of the robot primitives does. // all Jago programs must extend the Task class public class DemoProgram extends Task int turntime = 120; // time req'd to pivot 90 deg. int backuptime = 100; // used to back off walls // method used to back away from wall before turning public void backup() onrev(out_a+out_c); // set both motors to reverse. pause(backuptime); } // method used to pivot robot right public void turnright() onrev(out_c); // set right motor to reverse. onfwd(out_a); // set left motor to forward pause(turntime); // wait for turn to complete // set both motors to forward } // flow of execution begins in the run method public void run() // make program aware of touch sensor setsensor(sensor_1, SENSOR_TOUCH); // loop 4 times for(int i = 0; i < 4; i++) //set both motors to forward while(sensorvalue(sensor_1)!= 1)} // while wall not hit backup(); turnright(); } // for } // run } // ExampleProgram Robot Simulator Over 500 students take this course each semester. The logistics of issuing and tracking and collecting robot kits for each team is daunting. Especially since each kit contains over 750 parts. Cadets also have very full schedules, minimizing the overhead associated with education is an important goal of the faculty at West Point. We found a way to both minimize the logistics and overhead and achieve a learning objective. We provide a simulator with the Jago environment. The students write their Jago programs and run them on the Jago simulator. This way they can design, code and test their programs in their rooms without spending hours assembling a Lego robot. Once they are confident in their algorithm design, then can bring their completed Jago program to the lab, cross-compile it to Not-Quite C, and download on the RCX to verify that their code runs the robot as well as it does their simulator. On the project due day, the students demonstrate their work on a robot in the classroom as part of a project presentation. PEDAGOGY FOR USING JAGO Common Scenario Provided as Part of the Assignment Embedded computer systems are pervasive in Army weapons systems. These systems will be a part of your daily life in the Army. Understanding how they operate (or fail to) is important in order to take advantage of the system's full potential. The Army is looking at robotic systems for a number of force multiplying systems. Your commander has provided you with a prototype robotic system that can maneuver across terrain with obstacles. Your task is to evaluate the system, write an algorithm to negotiate two F1B-4

4 types of obstacles, and successfully maneuver through a test track. If your algorithm works correctly, and within a specified time limit, the manufacturer will build the fielded system with an embedded version of your code. Good luck and make sure you test your program to ensure it works as advertised. You would not want the Army to buy a system that has a defect. algorithm you design must be able to negotiate any and all such configurations. The second type of duct construction the robot will have to negotiate will be one which has the two walls of the duct which are horizontal to each other and two perpendicular Specific Assignment The Army is developing miniature robots for urban warfare reconnaissance and possible weapons delivery, specifically for close quarters reconnaissance. The winning design will be used on a possible test mission for reconnaissance through an enemy bunker's air ducts just outside of Baghdad. Due to the sensitivity of the mission, tethered robots are not candidates for this mission. Autonomous robots are the least risky option. Due to known intruder detection systems within the bunker's air ducts the robot must negotiate the ductwork within a four-minute time span. The total length of ductwork that the robot must negotiate is 12 feet. The robot has to only negotiate to the end of the ductwork obstacles. A classified payload will be released at that point. Plans obtained from the European company that built the underground bunker in Iraq show the construction of the ductwork to be similar to a maze with two main types of obstacles. The first type of duct construction the robot will have to negotiate will be one which has the two walls of the duct which are horizontal to each other and a perpendicular wall attached to one of the duct side walls (figure A). Figure A The exact dimensions and locations of these obstacles cannot be determined from the plans obtained. The Figure B walls attached to either of the duct side walls (figure B). An opening between the two perpendicular walls will be no smaller than seven inches, which is large enough for the robot to fit through if it is centered on the opening and travels straight through. The exact dimension of the opening and the lengths of the perpendicular walls cannot be determined from the plans obtained. The algorithm you design must be able to negotiate any and all such configurations. A seam in the ductwork, that has a distinctive difference in color, separates these two types of obstacles. The light sensor built into the robot has the ability to detect this color difference. Your mission is to write a Jago program that can be downloaded into a standard Lego robot configuration that your instructor provides. This program will allow the robot to successfully negotiate a test maze that will replicate a possible scenario the robot might encounter in the Iraqi bunker in the shortest possible time. Keep in mind the longest time before payload release is 4 minutes. A simulator has been developed to test your algorithm before you download it into the robot and is available by following the attached instructions. While the simulator will help test and debug your algorithm it is not a perfect representation of the real world. In some cases, your algorithm may work in the simulator but once downloaded in the robot and tested in the maze the results may differ due to environmental effects such as walls that are not F1B-5

5 completely perpendicular to each other and differing traction on the floor of the maze. Your algorithm should account for these differences. RESULTS Six two-person groups were given the project and not only did all of them come up with solution that met the minimum requirements, they all excelled in the overall project. The students that completed the robot project expressed a better appreciation for the design process, which is exactly what we are trying to teach in CS105. One student commented that his group... spent a lot of time trying to come up with an efficient algorithm. Once we thought through the algorithm, writing the code was easy. This is exactly what we are trying to achieve in CS105. We would like the students to leave the course with an understanding of how to use a computer to solve problems. The Java programming language is just another tool in each student s arsenal, and we don t want syntax to get in the way of problem solving. The Java code below is one cadet group s solution to the project described above. /* Program Legobot This program gives instructions to an autonomous lego robot in order for the robot to negotiate a maze. Programmed by: David T. Reyes '03, CO A-2 Casey Woo '03, CO A-2 for: CS 155 Section 02 I MAJ David Raymond public class Legobot extends Task /******************************** Global Data Members ******************************** int halfturn = 130; //time for a 90 deg. turn int fullturn = 250; //time for a 180 deg. turn /******************************** Public Methods void leftturn() void turn180() void righttest() void mainloop() void run() ******************************** /* Method: leftturn Purpose: public void leftturn() This method performs a left turn then moves fwd (North). Once leftturn is complete program control is returned to its calling method (turn180). onrev(out_a+out_c); onfwd(out_c); pause(halfturn); off(out_a+out_c); }//leftturn /* Method: turn180 Purpose: This method instructs the robot to make a 180 degree turn and then move forward (East) to the opposite end of the maze. Ater the robot hits the opposite wall it calls the leftturn() method. After leftturn() is complete and control is returned to turn180(), turn180 performs a break and returns control to its calling method righttest(). public void turn180() onrev(out_a+out_c); onfwd(out_a); pause(fullturn); off(out_a+out_c); //if the robot hits a wall at this point we //can assume that it has reached the //opposite wall so it can turn and continue //to check for gaps while(true) if (sensorvalue(sensor_1) == 1) leftturn(); break; //return to righttest }//if }//while }//turn180 /* Method: righttest() Purpose: After the robot hits its first wall and righttest begins, righttest performs a series of turns to find a gap in the wall. If the robot hits another wall before completing the righttest() method it assumes that it has reached the far end of the wall and calls the turn180() method. If not, the robot continues until it finds a gap and proceeds to the next obstacle. At the completion of each complete righttest or if loop in righttest() this method performs a break that returns control to its calling method, mainloop, which starts the process over again. public void righttest() F1B-6

6 onrev(out_a+out_c); pause(80); onfwd(out_c); pause(halfturn); pause(70); while(true) //if the robot hits a wall after this //turn we can assume that it has reached //the end of the wall and turn around to //check the other side if (sensorvalue(sensor_1) == 1) turn180(); }//if else onfwd(out_a); pause(halfturn); }//else break; //return to mainloop }//while }//righttest /* Method: mainloop Purpose: Determines if the robot hits a wall while going forward (North). If the robot does hit a wall it reacts by calling the righttest() method. public void mainloop() while(true) if (sensorvalue(sensor_1) == 1) righttest(); }//if }//while }//mainloop /* Method: run Purpose: Sets sensor, starts robot, and calls mainloop method public void run() setsensor(sensor_1, SENSOR_TOUCH); mainloop(); } // run } // Legobot FUTURE WORK Future improvements planned are a more visually accurate simulator with the added feature of being able to add new obstacles, backgrounds and active objects. Additionally, a direct compilation and download to the RCX brick from Java without the additional language translation step is planned. With these improvements and the successful integration of a final robot maze project into the advanced, CS155 course, the next step has been to integrate the use of the robots and simulator into the basic CS105 course final project as well as into smaller homework assignments and fundamental programming concept demonstrations such as ones on selection and iteration. Discussions with other departments such as Civil and Mechanical Engineering and Math are in the preliminary stage to take advantage of the basic knowledge the cadets have of the robots and the environment developed. Another proposed addition to the course would be to have 3d and 4th year students in an Electrical Engineering sensor building course build sensors for the robots which would be used in the CS105 and CS155 course homeworks and final projects. The views expressed herein are those of the author and do not purport to reflect the position of the United States Military Academy, the Department of the Army, or the Department of Defense. REFERENCES [1] MAJ David R. Raymond and LTC Donald J. Welch. Integrating Information Technology and Programming in a Freshman Computer Science Course. In the Proceedings of the 2000 Frontiers In Education Conference, Kansas City, MO, Oct., [2] Baum, D., Definitive Guide to LEGO Mindstorms, Apress, NY F1B-7