USARSim Tutorial

1. 1 USARSim Tutorial

2. 2 Programming Unreal The Unreal Virtual Machine Similar to Java Virtual Machine Components server, client, rendering engine, and the engine support code. Language: Unreal Script The Tick the smallest unit of time in which all actors in a level are updated States Object�s behaviors management Program state machine at language lever

3. 3 Programming Unreal (cont.) Network Programming Replication The way to communicate between server and client Types: actors, variables, functions Quality: reliable or unreliable Method: conditional replication Only replicate data to the relevance actors Simulated function Function runs both on server and client Similar to the fork() function in C Reference Unreal Networking Architecture http://unreal.epicgames.com/Network.htm UnrealWiki--Replication http://wiki.beyondunreal.com/wiki/Replication

4. 4 Unreal Script Object oriented language Language Reference Unreal Script Reference http://udn.epicgames.com/Two/UnrealScriptReference UnrealScript Lessons http://wiki.beyondunreal.com/wiki/UnrealScript_Lessons Compile Compiling With UCC http://wiki.beyondunreal.com/wiki/Compiling_With_UCC Edit ut2003.ini file Delete you .u file, then run �ucc make� Debug UnrealScript Debugger http://udn.epicgames.com/Two/UnrealScriptDebugger Print out the information you want

5. 5 Sensor Overview How sensor works Calculate based on the ground truth database Add noise and distortion Build sensor class Based on Sensor class Provide sensor data in plain text

6. 6 Sensor (cont.) The Sensor Class Attributes Name & type Noise & distortion Mounting info. Others Static mesh Scale Hidden sensor Methods Initialize setName and mounting Data sensor data, sensor type & sensor�s configuration

7. 7 Sensor (cont.) Build Sensor Extend from sensor class Specify properties (you may add your own attributes) Type Noise & distortion curve (the input-output curve) Static mash, scale and whether display the mesh etc. Provide sensor data Fill the GetData() function Calculate data Add noise Interpolate the input-output curve to distort data Fill the GetConf() function Compile the class

8. 8 Sensor (cont.) Example (range finder)

9. 9 Command The mechanism (Gamebots) BotConnection Receive data Parser data Transfer command to RemoteBot RemoteBot Store commands into variables Robot Check the RemoteBot�s variables every tick Make response to the variable

10. 10 Command (cont.) Add a command In RemoteBot Define variable(s) to store the command Ex. var int speed; In BotConnection theBot: the RemoteBot possesses the BotConnection Add parsing codes in ProcessAction() Check data type Parse data GetArgVal(): get the value of an argument ParseVector(), ParseRot(): get vector and rotation Set the variable of thebot (RemoteBot) Ex. theBot.speed = �;

11. 11 Command (cont.) In Robot class Controller: the RemoteBot of the robot Get the command through the controller Ex. speedCommand = RemoteBot(Controller).speed; Example

12. 12 Robot The workflow

13. 13 Robot (cont.) Maintain chassis� state Method Tick function: PackState() Server packs chassis� state Event: VehicleStateReceived() Unpack and calculate chassis� state Event: KUpdateState() Commit chassis� state Chassis state (rigid body state) Position Direction Liner velocity Angular velocity

14. 14 Robot (cont.) Control part(s) Method Tick function: PackState() Server packs part�s state Server and client update joint�s parameter torque, max speed, steering angle etc. Event: VehicleStateReceived() Unpack and calculate part�s state Unpack joint�s parameters Tick function: set joint�s control parameters Joint control

15. 15 Robot (cont.) Strategy Absolute control vs. relative control Position control vs. speed control vs. torque control State package replication vs. simple variable replication Example Chassis state maintain Rover � Differential(); KUpdateState(); replication expQ; Part state maintain P2DX � Tick(); replication steerAng; Part control P2AT � ProcessCarInput()