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Published on January 7, 2008

Author: Davidson

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Robotran: Robot programming adventures for novices in LEGO-land:  Robotran: Robot programming adventures for novices in LEGO-land R. Mark Meyer Debra T. Burhans Canisius College Buffalo, NY Overview:  Overview Our use of LEGO Mindstorms in the curriculum, especially early courses Robolang – a simple, non-threatening programming language Simulation – let them take it home with them How to sneak AI concepts into intro courses What’s NXT? But first... Our chief protagonist:  But first... Our chief protagonist The Pen bot a roverbot with an attached pen so it can draw, like turtle graphics. Educational Objectives:  Educational Objectives Motivate students to stay in CS using the fun and challenge of robotics Recruit new students to CS Teach non-majors simple programming Provide a framework for CS majors to learn Java better (using Lejos) Use social implications of robotics to motivate ethics discussion Introduce students to AI concepts Most of all....:  Most of all.... Our goal is happy students! Curricular Use:  Curricular Use CSC 110 – A “CS 0” course CSC 109 – Another “CS 0” course that is solely robotics EGR 111 – Introduction to engineering (pre-engineers) CSC 111 – Our Java-based “CS 1” CSC 360 – Intelligent Systems: AI, robotics, knowledge bases CSC 391/491 – Seminar, 1 credit hour special projects Role of AI:  Role of AI Only CSC 360 is a true AI course and uses AI techniques: Wumpus world, intelligent agents, searching CSC 109 – focus on basic AI and computing in the context of robotics, programming as a way of creating behaviors CSC 110 – mostly drawing letters, simple algorithms EGR 111 – study sensor electronics, basic programming concepts (BrickCC), engineering through robot building We also sneak AI concepts into CSC 111 Seminar allows students to work on larger AI projects Robotran V.1:  Robotran V.1 Translator program  Robolang – a simple Python-ish language  Translator to true Lejos  Used as web applet or standalone Java app  Can compile and download Robolang Details:  Robolang Details Streamlined syntax for assignments and control structures, especially button handler methods Uses Java expression syntax and transparently inserts into the final Lejos code Simplified robot commands: go forward 10 seconds Motor.A.start(); Motor.B.start(); try { Thread.sleep(10000); } catch (Exception e) {} Simplified function (method) syntax Simple Light Follower program:  Simple Light Follower program program follow1 constant BLACK = 42 loop var lightvalue = S3 display lightvalue if lightvalue < BLACK then stop else go forward end end Light Hunter:  Light Hunter program follow4 global constant BLACK = 42 global var turnedLeft = 1 loop var lightvalue = S3 display lightvalue if lightvalue < BLACK then do findLight else go forward end end define huntLeft() returns number turn left sharp 25 degrees var lightvalue = S3 if lightvalue > BLACK then return 1 else turn right sharp 25 degrees return 0 end end define huntRight() returns number turn right sharp 25 degrees var lightvalue = S3 if lightvalue > BLACK then return 1 else turn left sharp 25 degrees return 0 end end define findLight var result if turnedLeft = 1 then result = huntLeft() if result = 1 then return end result = huntRight() if result = 1 then turnedLeft = 0 return end end if turnedLeft = 0 then if huntRight() = 1 then return end if huntLeft() = 1 then turnedLeft = 1 return end end end Syntactic Sugar:  Syntactic Sugar Use only one equals sign to compare things Allow several syntaxes for assignment statements; avoid the old “equals” confusion let X = 5 set X to 5 Allow parentheses around conditions to be omitted Use clear control structure delimiters: “end” statements Turn around the order of elements in a function definition, à la Pascal define huntRight() returns number The Place of Language:  The Place of Language Continuum of difficulty in Robot languages: Robolab and NXT graphical environment Lisp, Robolang, Python type languages NQC Lejos What is your goal? Teach beginner non-majors to control a robot? Use easy language Inspire engineers? Use NQC Reinforce Java for CS majors? Use Lejos However, a difficult language may turn off students! Alternative: use a ramp-up strategy like “Dr. Java” project Use Scheme first, then Java Lessons Learned from Language Design:  Lessons Learned from Language Design Separating button events from sensor polling is tricky for novices Language structures should aid this distinction when RUN button is pressed do stuff end This shouldn’t be in-line with main program Need definite “program” structure with its own “end” More study is needed to pinpoint troublesome concepts Assignments:  Assignments Robot avoids obstacles by randomly turning after bumps Robot draws letters Robot follows a light source and hunts for it when lost Robot receives input from bumps and button presses, including binary or unary numbers Robot is taught a path which it can then replay (uses arrays) Robot follows a line on the floor Robot stays within a sumo ring and tries to push another robot outside without leaving the ring itself Robot navigates a maze (needs to remember path & obstacles) Navigating the Maze:  Navigating the Maze Robots were programmed in NQC, Lejos, and Robolang Better algorithms, anyone?:  Better algorithms, anyone? The trickiness of the algorithms was a great leveler. There was no strong edge for those who used more complex languages. Robot Competitions are Fun!:  Robot Competitions are Fun! The Physics Team at the Robot Competition (Jeff, Mark, Jim) Taken 18 Nov 2006 AI concepts at work:  AI concepts at work Many of these tasks can motivate AI discussion and algorithm development, esp. searching, strategy and data structures One definition of intelligence: “having a wide repertory of solutions from which to choose when encountering a problem” We can’t do much with the RCX alone due to limited memory and processing time Even the NXT only has 256K RAM, but it can more easily use a wirelessly connected computer as its brain These robots are learning environments, not built to actually explore Mars! Similarly our students are just getting started. Need for a Simulator:  Need for a Simulator Almost everyone agrees we need one Shouldn’t usurp the tactile, kinetic experience Allow students to complete assignments at home or outside of lab Could be used to explore more complicated behaviors Major challenge to build a realistic and useful one! Doomed to Succeed?:  Doomed to Succeed? “... and the demo was launched again. This time the students lost their wireless connection and the process had to begin again. In the end, the visiting Boeing bigwigs gathered around a laptop display and watched an elaborate demonstration of the treasure hunt concept – in simulation. The Boeing folks were quite intrigued and, seemingly, satisfied. ‘Simulations,’ so the saying goes at the RI (Robotics Institute at CMU), ‘are doomed to succeed.’” “Almost Human: Making Robots Think” by Lee Gutkind WW Norton, 2006. Our simulator:  Our simulator Simulate the penbot, only one at a time, geared towards real assignments Don’t get overly caught up with 3d graphics Provide functionality with both Robolang and Lejos Make it flexible for future implementation on NXT Use the lejos compiled code that makes calls to the firmware ROM Create our own ROM object with same API and let the compiled code, running in tinyVM, call it Then our ROM object sends updates to a graphics simulation object Some of the Simulation code...:  Some of the Simulation code... package simulator.rcx; //import simulator.*; /* This class represents the RCX robot during a simulation. It keeps track of * states and properties that are associated with a RCX robot. * Note that most fields are static because components on the RCX are finite * meaning that there are a static number of robot components. (ex: number of * buttons will always be 4) *@author David Puehn */ public class RCX { /* The state the robot is in * 0: off * 1: on * 2: on and running a program */ public static int state = 0; /* The current voltage of the RCX's batteries */ public static double batteryVoltage = 319; //TODO: create me thod to convert voltage to readable value /* The virtual RCX's buttons */ public static Button ButtonRUN = new Button(0x01); public static Button ButtonVIEW = new Button(0x02); public static Button ButtonPRGM = new Button(0x04); /* The virtual RCX's motors */ public static Motor MotorA = new Motor('A'); public static Motor MotorB = new Motor('B'); public static Motor MotorC = new Motor('C'); /* The virtual RCX's sensors */ public static Sensor Sensor1 = new Sensor((short)1); public static Sensor Sensor2 = new Sensor((short)2); public static Sensor Sensor3 = new Sensor((short)3); /* The RCX's ROM */ public static ROM Rom = new ROM(); /* The RCX's Memory */ public static Memory Memory = new Memory(); /* The RCX's Poller */ public static Poller Poller = new Poller(); /* The RCX's Sound */ public static Sound Sound = new Sound(); /* The RCX's User Controls */ public static RcxController Controller = new RcxController(); /* The RCX's LCD */ public static Display LCD = new Display(); /* Holds all of the simulator components so that we can iterate through them */ public static RcxComponent[] components = { ButtonRUN, ButtonVIEW, ButtonPRGM, MotorA, MotorB, MotorC, Sensor1, Sensor2, Sensor3, Rom, Memory, Poller, Sound, LCD }; Emulating the native ROM routines:  Emulating the native ROM routines package simulator.rcx; /* An emulation of the RCX's native ROM routines */ public class ROM implements RcxComponent { //simulates behavior when call to RCX's rom public static void call(short aAddr) { //refresh the lcd if (aAddr == 0x27c8) { RCX.LCD.refresh(); } //clear the lcd else if (aAddr == 0x27ac) { RCX.LCD.clear(); } } //simulates behavior when call to RCX's rom public static void call(short aAddr, short a1) { //setSegment of lcd //a1: the lcd segment if (aAddr == 0x1b62) { RCX.LCD.setSegment(a1); } //clearSegment of lcd //a1: the lcd segment else if (aAddr == 0x1e4a) { RCX.LCD.clearSegment(a1); } //reset two byte timer //a1: who the hell knows? else if (aAddr == 0x339a) { //TODO: figure out what the hell this is } } //simulates behavior when call to RCX's rom public static void call(short aAddr, short a1, short a2) { //readButtons call //a2: pointer address; place to store the button that is pressed if (aAddr == 0x1fb6 && a1 == Opcodes.BUTTONS_READ) { short buttonState = Button.readButtons(); RCX.Memory.writeShort(a2, buttonState); } //systemSound call //a2: 0 = short beep 1 = double beep 2 = descending arpeggio 3 = ascending arpeggio // 4 = long low beep 5 = quick ascending arpeggio else if (aAddr == 0x299a) { if (a1 == Opcodes.SOUND_QUEUED) { RCX.Sound.systemSound(true, (int)a2); } else if (a1 == Opcodes.SOUND_UNQUEUED) { RCX.Sound.systemSound(false, (int)a2); } } //getVoltageInternal call //a2: pointer address; place where to store the voltage else if (aAddr == 0x29f2 && a1 == Opcodes.POWER_BATTERY) { RCX.Memory.writeShort(a2, (short)RCX.batteryVoltage); } } The New Robotran and Simulator:  The New Robotran and Simulator Near future improvements:  Near future improvements Simulator Permit collision detection with the walls Permit building obstacles that the robot can bump into Permit building a black line path on the ground for light following Permit a light source to simulate a flashlight that the robot’s light sensor can detect Better Robolang parser and error messages Our experience:  Our experience Students in early courses that use only Robolang like it They can implement very complex algorithms quickly They participated in a local robot competition and did well Those who went on to CSC 111 seemed to appreciate the link and made the transition to Lejos/Java well Surveys and anecdotal evidence indicate high level of satisfaction After first robot lab: “I actually got a robot to do something!” No statistical difference in final grades between non-robot and robot years in CSC 111 Student Reactions to AI:  Student Reactions to AI Some students who are not very interested in computer science find AI fascinating The interest in AI helps motivate them in robot programming tasks Students are able to make connections between the very simple systems they are using and extremely complex robots such as the Honda Asimo Students appreciate the difficulty of unsolved AI problems such as vision The cultural perception of programmers is negative and boring a la “Office Space”, but roboticists are viewed as interesting and “sexy” Our focus: the students:  Our focus: the students Future Plans:  Future Plans Test the use of programming language structures’ effect on task completion time Test the ease of adjustment to a harder language Continue to track recruitment and retention (problem with small sample size at smaller colleges) Port to the NXT Teach an honors science elective that is heavily liberal arts and is focused on AI and robotics Develop a cross-disciplinary minor in AI/robotics that will draw a larger audience into computer science courses Of course, debug, Debug, DEBUG! Have fun!

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