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© 2021, V10.4
 
  Jython
 
 

 

RobotSim

A OOP based Simulation Package for the Lego NXT/EV3 Robot

(JavaDoc)

Robot applications are usually executed software based before being tested on the robot itself. This not only saves time, but also cost. The software simulator should be designed that no or only few modifications of the simulation program is necessary to run it on the real machine. The standard Lego NXT/EV3 robot is a moving robot for the educational environment using a Lego brick microcontroller, fixed on a gear with two motors. It can be equipped with several sensors, like touch sensors, light sensors, etc. The microcontroller can be programmed in different languages, among them Java and Python. Wrapper libraries NxtJLib and EV3JLib are available that are fully object oriented.

In the class room a robot simulator may be useful not only for demonstration of the robot application development but also if there are not enough NXT/EV3 bricks available for all students. The simulation packages RobotSim presented here is based on the JGameGrid game development framework and the source code of the package is made public to be studied and modified by the users. The design follows closely the NxtJLib package for the NXT brick in remote control mode and the EV3JLib/EV3LibA packages for the EV3 in remote control and autonomous mode.

The core class LegoRobot has a very clean and simple public interface but does most of the work using a private inner class Nxt that extends Actor. As in NxtJLib/EV3JLib, touch and light sensors are derived from the abstract class Part that extends Actor too. The robot's playground is a GameGrid instance with one-pixel resolution which is a private instance variable of LegoRobot. This design hides most of the underlying JGameGrid package and, for basic simulations, the student does not need any knowledge of JGameGrid. To fully understand the possibilities of the RobotSim, take a look at the applications displayed below. The first one is the most elementary application which simply creates a robot with two motors moving it by rotating the motors forward and backward.

Error Page

Error Page

Stack trace:

java.io.FileNotFoundException: The requested resource [/home/pyincludes/SimEx01.html] is not available
	at org.apache.catalina.servlets.DefaultServlet.serveResource(DefaultServlet.java:845)
	at org.apache.catalina.servlets.DefaultServlet.doGet(DefaultServlet.java:497)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	at org.apache.catalina.servlets.DefaultServlet.service(DefaultServlet.java:477)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor64.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580)
	at org.apache.catalina.core.ApplicationDispatcher.access$100(ApplicationDispatcher.java:64)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:113)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:101)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:507)
	at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955)
	at org.apache.jsp.jython_005fex6_jsp._jspService(jython_005fex6_jsp.java:162)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor64.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580)
	at org.apache.catalina.core.ApplicationDispatcher.access$100(ApplicationDispatcher.java:64)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:113)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:101)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:507)
	at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955)
	at org.apache.jsp.apluhomex_jsp._jspService(apluhomex_jsp.java:2358)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor64.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:253)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:191)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.ajp.AjpProcessor.service(AjpProcessor.java:432)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

Request URL:

http://www.aplu.ch/home/apluhomex.jsp

Parameters:

    site: 69