%MobileSim

Introduction

MobileSim is software for simulating mobile robots and their environments, for debugging and experimentation with [ARIA][aria] or other software that supports Adept MobileRobots platforms.

MobileSim is based on the Stage library, created by the [Player/Stage project][ps]. Stage and MobileSim are free software, distributed under the terms of the GNU General Public License: see the full license for details.

MobileSim converts a MobileRobots/ActivMedia map (a .map file, created by Mapper3™, Mapper3-Basic, or other means) to a Stage environment, and places a simulated robot model in that environment. It then provides a simulated Pioneer control connection accessible via a TCP port (similar to the real Pioneer's serial port connection). ARIA is able to connect to TCP ports instead of serial ports (ArRobotConnector, for example, automatically tries TCP port 8101 before the serial port).

MobileSim (powered by Stage) has the following features and device models. Device model parameters may be customized in a configuration file, or new models may be defined based on existing models.

• Various models of MobileRobots/ActivMedia differential drive mobile robot bases (Pioneer 3 DX and AT, PowerBot™, AmigoBot™, PeopleBot™, PatrolBot®, Seekur®, Pioneer 2, Pioneer 1).
• You can define custom models of differential drive or omnidirectional robots, laser and sonar, defined either as a Stage model definition, or by loading an Aria parameter (.p) file.
• Sonar range sensor model
• Laser range sensor (SICK LMS-200) model
• Robot odometry pose estimation (with cumulative error)
• Multiple robots (good performance is possible on a fast computer with more than 25 robots)
• Evironment and obstacles are loaded from a MobileRobots/ActivMedia/ARIA map file; use the same map with ARNL/SONARNL or your own software.
• Interactively move robots and obstacles (with customized map file, see below)
• Objects (robots or obstactles) may be configured to be detectable only by some sensors
• Objects (robots or obstacles) may be set as "highly reflective" for special detection by the laser range sensor
• Save image "snapshot" of simulation or save a sequence of images for making movies.
• Map files may be reloaded at run time
• Robots may be interactively repositioned through the GUI or by a command from client software
• Client software may send log messages to MobileSim. Log messages are timestamped and displayed both the GUI and console or log file, with optional HTML formatting.
• Visualization options for sensors, robots and obstacles, such as drawing robot "trails" to show history of motion, color, diagnostic values/visualization, and visualizations for debugging the simulator itself.
• Configurable space and time resolutions.
• Full source code included under the GPL for understanding the simulation implementation, customizing and improving it, or even adapting MobileSim's ARIA communication protocol layer for other simulators.

[aria]: http://robots.mobilerobots.com/wiki/Aria ARIA [ps]: http://playerstage.sourceforge.net Player/Stage/Gazebo project

Installation

To install MobileSim on Windows, run the executable self-installer.

To install MobileSim from either the RPM or Debian (deb) package, use your system's appropriate installation tool (rpm on RedHat, SuSe, etc. and dpkg or Synaptic ("Add downloaded packages") on Debian, Ubuntu, etc.). The RPM was built on RedHat 7.3, and the Debian package was built on Debian 3.1 (sarge) for i386 (32-bit). MobileSim requires the GTK 2.0+ libraries on RedHat, and GTK 2.6+ on Debian. It also requires libstdc++ 2.2 for libc6. (These libraries are standard parts of most Linux installations, but if they are missing you may have to install packages which provide them). If you are running amd64 or ia64 Debian, try installing the ia32-libs-gtk and ia32-libs packages using apt-get, and then installing the MobileSim package with the --force-architecture option to dpkg.

To build MobileSim from source code, obtain the "MobileSim-src" tar/gz archive from [http://robots.mobilerobots.com/wiki/MobileSim][webpage] and follow the instructions in the README.src.text file found inside.

[webpage]: http://robots.mobilerobots.com/wiki/MobileSim MobileSim web page

How to get started

To simulate a robot you need a map file containing lines for walls. A map file with lines can be created using a recent version of Mapper3 or Mapper3-Basic (See [robots.mobilerobots.com][site]) or by other means. See the ARIA Reference Documentation for the ArMap class for a full description of the format, or refer to columbia.map or AMROffice.map, distributed with MobileSim, for an example.

MobileSim may be launched from the Start menu (Windows), or from the Gnome or KDE menu (Linux), or from the command line (any platform).

Run MobileSim from a command line prompt like this:

MobileSim

or, to skip the initial dialog by specifying a map file and robot model to create on the command line:

MobileSim -m *<map file>* -r *<robot model>*

For example:

MobileSim -m columbia.map -r p3dx

The parameters are optional. The default robot model created, if -r is not given, is "p3dx". Some additional robot models include "p3at", "powerbot", "peoplebot", "patrolbot-sh", "seekur", and "amigo".

To create multiple simulated robots, use -r multiple times, naming the robots after the model type, seperated by a colon, if you wish:

 MobileSim -m columbia.map -r p3dx:robot1 -r p3dx:robot2 -r amigo:robot3

If you are working with many robots, it can be inconvenient to create them all at MobileSim startup. If you use -R instead of -r, then a new robot will be created on demand for each client that connects, and destroyed when the client exits. (So the robot's state is not preserved.)

More command-line options are described below.

If you run MobileSim with no command line options, or from the desktop menu, you may select the map and one robot model from a dialog box. Or, you may choose to use no map (but note that in this case, the usable universe is limited to 200 x 200 meters -- gray area indicates the edge.)

Example maps are included with MobileSim. On Linux, you can find these files by navigating from the root file system to /usr/local/MobileSim. On Windows, these maps are in C:\Program Files\MobileRobots\MobileSim. columbia.map included with MobileSim is equivalent to columbia.map included with ARNL.

A window will appear, displaying your map environment and robot(s). The robot will start at a home position in your map, if present, or at the center of the map. The robot's body is drawn based on the aproximate length and width -- including wheels -- of the model selected. You can pan in the window by holding down the right mouse button, or mouse button with the Shift or Control key and dragging. You can zoom with the mouse scroll wheel, or by holding down the middle mouse button or left mouse button with the Alt or Option key, and dragging towards or away from the center of the circle that appears.

The robot may be moved by dragging it with the left mouse button and rotated by dragging it with the right mouse button, or while holding down the Shift or Control key. Note that this will update the robot's true pose, but not its odometry -- it is like picking up the robot off the ground and carrying it to a new location.

You can turn on device visualizations using the View menu. Ranger or Sonar: if a client program has connected and enabled the sonar, sonar field centers will be drawn as grey lines. Laser: If a client program has enabled the laser rangefinder, its range will be drawn as a light blue field. Position: Axes are drawn for the robot's odometry coordinate system, and its true pose, odometric pose, and current velocity are displayed.

A snapshot or sequence of snapshots of the window can be saved as a bitmap file to disk with the Export item in the File menu.

The lower log message pane displays information and warning about what the robots are doing (some commands will result in a log message, but not all). SIM_MESSAGE commands also display messages here. The statusbar pane below the log message pane displays, from left to right: the total time since the simulator started; the ratio of real time per update step and simulation time, indicating how close to real-time (1.0) the simulation is running; the total number of "subscriptions" in the simulation (one per each robot plus one per each device being accessed); and the MobileSim and stage version numbers.

Once running, a program can connect to the simulator via TCP port 8101, and use the same protocol on that TCP port as it does with a real robot over its serial port link. Any ARIA-based program that uses ArRobotConnector or ArTcpConnection will do this automatically. You can specify an alternate port number with the -p option. If multiple robots were requested with multiple -r options, each additional robot will use the next port number (i.e. 8102, 8103, etc.). For these additional robots, you will have to specify the port number when running its ARIA program, usually using the -rrtp (-remoteRobotTcpPort) command-line option.

A tool called convertBitmapToArMap is available in the ARIA utilities and in the MobileSim source code to convert a PNM format bitmap image to an ArMap .map file. On Linux, first install libnetpbm::

sudo apt-get install libnetpbm

Then you can build convertBitmapToArMap using make:

make convertBitmapToArMap

Run with -help for info:

./convertBitmapToArMap --help

A tool called convertSfWorldToMap is also available in ARIA's collection of utility and example programs to convert a Saphira .wld file to a .map, as well as a tool called addSfWorldLinesToMap for importing lines into a .map from a .wld.

Notes, Limitations, and Future Plans

The goal of Stage and MobileSim are to provide an efficient and sufficient simulation of multiple robots. While we have modified Stage to add some features and additional behavior (such as basic sensor noise), the simulation remains simplified. Don't forget to test your code on a real robot. See below for notes on the internal simulation mechanism and robot and sensor models.

"All models are wrong. Some are useful." --George E. P. Box

However, since the full source code for MobileSim and Stage are available (in the "MobileSim-src" package available from the [MobileSim webpage][webpage]), it is always possible to add new models or modify existing models to simulate any particular properties you need. Stage is not hard to understand and modify. If you need any help, ask on the aria-users mailing list, or the Player/Stage mailing list. If you do make any modifications that you think others would find useful, you may post them to aria-users, or send them to [email protected].

A note about data communications channels

On a real robot, ARIA may be communicating with different devices over separate communications channels. For example, ARIA communicates with the robot microcontroller over one RS-232 serial port, with a SICK LMS-200 laser rangefinder over a different RS-232 serial port, simultaneously using two different threads (one contained in ArRobot, the other in ArLMS200 which is a subclass of ArThreadedRangeDevice). Other additional devices may use additional parallel communications channels such as serial, USB and ethernet connections.

However, ARIA communicates with MobileSim over only one TCP socket connection. Therefore all communications with both the simulated robot and simulated devices must occur on this one channel, the same channel as the robot connection. ARIA's Connector classes detect MobileSim and use the appropriate code to handle data transfer with devices via the original "robot" TCP connection to MobileSim. Be aware of this when structuring programs; for example, laser data will not be received unless the ArRobot connection is active and running (using either ArRobot::runAsync() or ArRobot::run()).

Additional notes:

• See below for details on supported commands and specific known problems with the ARCOS/AROS/P2OS command emulation.
• Sonar reflection is not modeled
• Several devices are not available yet, including grippers, arms, general pan-tilt units, IR sensors, bumpers, analog or digital I/O ports, or video cameras.
• MobileSim is somewhat graphics intensive and may compete with e.g. MobileEyes for graphics resources, especially on older computers, VMs, or other systems with limited graphics resources. Graphics display is not fully optimized yet.
• While it is possible to make the simulation run faster (or much slower) than near "real time", it is not well tested how this affects clients. Many clients (including those using ARIA) have timeout limits based on the real system time (it is possible to configure most of ARIA's timeout limits, though. See reference documentation or ask the aria-users group).
  Clients also may not be able to process packets fast enough if the simulation runs much faster than real time, resulting in buffering of data and possibly loss of data.

Future plans for include better sonar model, simulating additional devices, and various user interface features for creating new simulated robots, loading maps, and tweaking their properties. If you have any requests or would like to help add features, please join the discussion on the aria-users mailing list.

Internal Simulation Mechanism and Models

The simulation loop attempts to run at a fixed real-world time interval, corresponding to a fixed simulated-world time interval. In most cases, each simulated time interval would ideally equal the real (system) time taken to perform that interval. This ratio is monitored and a short running average is displayed in the bottom of the MobileSim GUI window, and is also available from the SIM_STAT packet. It should normally be at or close to 1.0 most of the time. (The desired ratio can be adjusted, but will cause problems with most software).

At each iteration, the Stage simulation engine checks for GUI input (if GUI is enabled), then updates state of each simulated robot, sensor, and other device in the simulation -- it is at this stage that the robot is moved if moving, the environment is searched to determine sensor readings, etc. (See below for some deatils.) Then the GUI display (if enabled) is updated. The simulation update interval is configurable. The default rate is 100ms.

Client communications are also done at a given interval (100ms by default). For each robot, data is sent if a client is connected to that robot, according to the Pioneer protocol. This includes its odometric position estimate, miscellaneous state, and, if enabled, simulated sonar and laser data.
Commands are read from the client software (if any were sent), and stored for the appropriate Stage device model to handle in the next iteration of the simulation loop.

Each robot, and each sensor or other device on each robot, is simulated by a model object. The code for these models can be found in the stage/src subdirectory of the MobileSim source code.

Simulation environment

The contents of the simulated world are read from a map file (ArMap format, same as used by Mapper3 and other AMR software). The ArMap file contains obstacle data given as points and/or lines which will be sensable by all sensors, and with which robots can also collide. It is also possible to represent simple shapes in the map file which will only be present in the simulator (and are not used by ARNL for localization or planning). These objects may be configured as visible or invisible to different sensor types, and as subject to collisions by other models (i.e. robots) or not. See below for details.

In addition, the shape of all simulated robot models are also present in the environment, and subject to collision and sensing by other robots.

The simulation environment is represented with a minimum resolution, which is by default 2 cm. (This can be adjusted with the --resolution command-line argument, see below for details.)

position model, a movable robot

A mobile robot that can move within the world. The robot may be differential-drive (two degrees of freedom, capable of translational and rotational motion), or omnidirectional (three degrees of freedom, capable of translational, lateral or rotational motion). Motion can be commanded via desired velocities in each axis (velocity control, from VEL, TRANSVEL, and RVEL comands), or discrete changes in position may be commanded relative-position control from MOVE and DHEAD commands, or absolute heading from HEAD command). In addition, clients can request artifically dropping the robot at any new position in the world.

The code implementing the position model can be found in the MobileSim source code in stage/src/model_position.c.

At each simulation loop, the position model is updated according to the most recently received velocity commands. Velocity is controlled on three independent axes: translation (robot local X), lateral translation (robot local Y, non-differential drive robots only) and rotation (robot local Theta). The position model determines the currently desired velocities on each axis of motion (X, Y (seekur robot only), and Theta). This is clamped according to previously set maximum speed parameters. Previously set acceleration or deceleration parameters and the duration of the simulated loop iteration are then used to determine an increased or decreased velocity from the robot's current velocity, and a potential new position is projected from the current position using these velocities. This is followed by collision checking, and then an update of the simulated odometric pose estimate.

If a relative distance translation (MOVE) command is active, then a velocity proportional to the remaining distance and the configured maximum velocity is used. If the robot has already moved the commanded move distance however, then desired velocity is set to 0. The desired velocity will later be limited according to maximum speed configured.

If a translation velocity command (VEL) is active instead, then this value is used as the desired velocity.

If the robot is omnidirectional (not differential drive), then the same is done for Y (LATVEL commands velocity in Y. There is no command in the Pioneer protocol for relative distance on Y.)

If an absolute heading command (HEAD) is active, then a rotational velocity proportional to the difference from the current heading is used. If the robot has already rotated to the commanded heading however, then no rotational velocity is desired. The desired velocity will later be limited according to maximum speed configured.

Relative heading commands (DHEAD) are converted to absolute heading commands when recieved based on the robot's current heading at the time the command is received.

If a rotational velocity command (RVEL) is active instead, then this value is used as the desired rotational velocity.

Next, all desired speeds as specified or calculated above are limited by maximum upper limit parameters. These are set separately by software clients using SETV and SETRV commands (or initial defaults specified in the model definitions in PioneerRobotModels.world.inc.)

Next, acceleration and deceleration parameters are used to ramp the robot's current velocities up or down towards the desired velocities. Acceleration and decelaration parametrs are set separately by clients using SETA and SETRA commands (or initial defaults from the model definitions are used). (A client may also specify a temporary override deceleration value via the ESTOP/QSTOP commands. Deceleration is then reset back to the previous value once the robot has stopped.) If accelerating, the new velocity is incremented by acceleration * dt, where dt is the time elapsed since the last update of the position model in the previous simulation loop iteration: we assume that the next simulation iteration will be within a similar time interval. If decelerating, velocity is decreased. If the desired velicity is within a threshold of the current velocity, then the desired velocity is simply used.

The above process can be logged for debugging by switching the definitions of some macros in the model_position.c source code and recompiling, though note that this will generate a lot of output.

Next, a collision test is performed for the new position of the robot. If any part of the robot shape (including the shapes of any other attached sensor models, such as laser rangefinder) will collide with the environment or any other robot or model, then the robot is not moved to the new position, so motion is effectively stopped immediately. The collision state is indicated to client software via the "stall" flag.

As the robot moves, an updated virtual odometric pose within a global cartesian coordinate frame is also calculated, with error artificially introduced. This is provided to client software as its odometric pose estimate.

Only position, velocity and acceleration of the robot as a whole is simulated. Other aspects of the robot's motion such as momentum or inertia are not simulated, nor are component parts such as wheels, nor the robot's interaction with the world other than collision detection.

The updated pose estimate is calcualed by projecting the robot along its current basic trajectory (velocities) from the previous pose estimate, plus some error. (The pose is initialized to (0,0,0) when the simulated robot is created.)

mx = (vx * dt) * (1 + error.x)
my = (vy * dt) * (1 + error.y)
mth = (vth * dt) * (1 + errror.th)  
pose.x += mx * cos(th) - my * sin(th)
pose.y += mx * sin(th) + my * cos(th)
pose.th += mth 

vx, vy, vth are the robot's current velocity in its local X and Y axes, and rotational velocity. Th is the robot's current heading (in global pose coordinate frame).
Note that on differential drive robots, vy is always 0 since it cannot directly move along its Y axis, but may be nonzero on robots capable of lateral motion.

In MobileSim 0.6.x, error values of 0.0075 for error.x and error.y and 0.0075 for error.th are used by default for all robots, except for "p3dx_noerr" where no error is used. Starting in MobileSim 0.9.x, there are several choices for calculating error, which can be selected via the --odom-error-mode command-line argument. random_each_update is the default (as was errorneously documented previously.)

• random_init Choose random values within a configured range at startup; each new robot will have different amount of error, even if same type.
• random_each_update Chose random values within configured range at each simulation iteration.
• constant Constant values, configured for each robot type.
• none Use 0 for error values.

The error ranges are specified in the robot model definitions (PioneerRobotModels.world.inc) and new custom model definitions may specify error ranges that override defaults. (See Model Definitions below.) The odom_error_range_x, odom_error_range_y, and odom_error_range_a properties specify ranges for error in each axis. Alternatively, an odom_error property can be used for constant error (if constant mode) or for symetric positive/negative error values (random modes) (this is for compatibilty). (Units are meters and radians.) The actual error values being used can be obtained by client software via the SIMSTAT packet (see below).

MobileSim can also calculate a simulated GPS position. This is calculated using the georeference position of the map file, and the simulated robot's position in the map (true position, not pose estimate.) A map must have a georeference point (OriginLatLongAlt) for this to work. The latitude and longitude are provided in the SIMSTAT packet. Some robot models have a GPS receiver position defined, when the corresponding real robot has a standard mounting location for the GPS receiver or antenna. If not, the center of the robot is assumed. Note that ARIA also has a GPS receiver location parameter in its robot parameter files. Some software (such as MOGS) use this to offset GPS positions it receives from both a real GPS and the simulator.

laser model

The laser model represents a simplified scanning rangefinder sensor. The position of the simulated laser in the world is relative to the position of the robot position model and the simulated laser data is updated after the robot has moved.

The code implementing the laser model can be found in the MobileSim source code in stage/src/model_laser.c.

A scanning rangefinder measures distance ranges at fixed degree intervales over its field of view.
At each simulation loop iteration, each of these range values is deterimed by a raycasting algorithm to search the simulation environment at that time. The field of view of the sensor is divided by the number of range samples that wil be taken to determine the angle of each sample. A small amount of static random error is added to each sample's angle, and then for each sample ray, the environment quadtree is searched along until another object is located, or the maximum distance capable is reached. Then the intersaction point between the ray and the shape of that object is calculated, and the distance between the center of the laser rangefinder model and that point is calculated. Finally, a small amount of random error is added to that range value.

A laser may be mounted upside down, in which case the order of readings is reversed.

Objects in the environment may be flagged as invisible to laser sensors, in which case they are ignored.

If the detected object has been configured with a special "reflectance" value, then this is stored with the range value, optionally modified by configurable rules (e.g. distance, angle of incidence, etc.) This simulates the capability of the SICK LMS-200 and some other lasers to differentiate special refelctor material applied to objects.

A range error of +/- 5 mm and angular error of +/- 0.04 degrees is used for simulated LMS-200.
A range error of +/- 7.5mm and angular error of +/- 0.04 degrees is used for LMS-100. A range error of +/- 6mm and agular error of +/- 0.04 degrees is used for S300.

If client software has requested laser data, then at each interval of client communications, the most recently calculated set of laser range data is sent to the client.

ranger model (used for sonar)

The "ranger" model is used to simulate sets of individual, relatively short range distance sensors, such as sonar and IR range sensors. It differs from the "laser" model in that the positions and orientations of each individual sensor transciever can be configured separately.

The code implementing the ranger model can be found in the MobileSim source code in stage/src/model_ranger.c.

In the simplest, default mode, for each configured sensor transciever, a raycasting algorithm is used to search the environment from the center of the sensor's field of view, within the minimum and maximum configured range. This distance is stored as the range data.

In the alternative "closest ray" mode, several raycasts are made within the field of view of the sensor transciever, and the shortest range is used. This mode is not used by default.

Finally, some random error may be added to the range value. +/- 0.5 mm is used, since sonar is generally stable, if not as accurate as the laser in most conditions.

Objects in the environment may be flagged as invisible to laser sensors, in which case they are ignored.

No special timing, acoustic, reflection, or other factors are currently simulated.

Advanced Usage

Command-line Arguments

A full listing of MobileSim's command line parameters follows:

Usage: MobileSim [-m map] [-r robot model ...] [...options...]

---

--map map Load map file (e.g. created with Mapper3)

-m map Same as -map map

--nomap Create an "empty" map to start with. Same as -map "". Ignored if -m is also given.

--robot Create a simulated robot of the given model. model[:name] If an ARIA robot parameter file is given for model, then MobileSim attempts to load that file from the current working directory, and create an equivalent model definition. May be repeated with different names and models to create multiple simulated robots. Name portion is optional. For example: --robot p3dx --robot amigo:MyRobot -r custom.p:CustomBot See PioneerRobotModels.world.inc for model definitions.

-r Same as --robot modelor--robot` model:name *model[:name]

--robot-factory Instead of creating one robot of the given model, accept any model number of client programs on its port, creating a new instance of the model for each client, and destroying it when the client disconnects.

-R model Same as --robot-factory model

-p port Emulate Pioneer connections starting with TCP port port (Default: 8101)

-W worldfile Use Stage worldfile worldfile instead of map, and instead of standard world configuration files.

--stageworld Same as -W.

--fullscreen-gui Display window in fullscreen mode.

--maximize-gui Display window maximized.

--minimize-gui Display window minimized (iconified)

--noninteractive Don't display any interactive dialog boxes that might block program execution. Also restart MobileSim if it crashes (Linux only).

--lite-graphics Disable some graphics for slightly better performance

--no-graphics Disable all graphics drawing for slightly better performance

--html Print log messages and other output in HTML rather than plain text

--cwd dir Change directory to dir at startup. Client programs can then load maps relative to this directory.

--log-file file Print log messages to file instead of standard error console.

-l file Same as --log-file file.

--log-file-max-size If the amoount of data written to the log file exceeds size size bytes, then rotate the log files (up to 5) and open a new log file. This option keeps the total size of all the log files under *size**5 bytes. If --noninteractive is given, the default for size is 5 MB. Otherwise, the default is not to limit the size of the log file at all.

--update-interval ms Time between each simulation update step. (Default is 100 ms. less may improve simulation performance but impact client responsiveness and data update.)

--update-sim-time ms How much simulated time each simulation update takes (Default is equal to update-intenval. More than update-interval results in faster-than-realtime simulation, which may cause problems for clients)

--start x,y,th Use x, y, th as robot starting point (even if the map has Home objects).

--start outside Start robots 2m outside the map bounds -- it later must be moved to within the map bounds to be used.

--start random Randomly choose a starting place within the map bounds.

--resolution r Use resolution r (milimeters) for collisions and sensors. Default is 20mm (2cm)

--ignore-command Ignore the command whose number is given. Refer to robot manual and MobileSim num documentation for command numbers. For example, to prevent client programs from moving the robot's true position with the SIM_SET_POSE command, number 224, use --ignore-command 224. May be repeated. Warning: MobileSim and/or your program may not function correctly if some critical commands are ignored.

--less-verbose Be a bit less verbose about logging messages, especially things that might be frequently logged (such as unsupported commands), to avoid filling up log files with useless info.

--log-timing-stats Log some simulation timing information every 30 seconds.

--bind-to-address Only listen on the network interface with IP address address for new address client connections (default is to listen on all addresses). This lets you run more than one MobileSim process on the same TCP ports on a machine that has more than one network interface.

--disable-crash-handler Disable the GDB crash handler (and just abort program on fatal signals). No effect on Windows, where there is no crash handler.

---

Note: Windows' command shell unfortunately does not display the standard console output of GUI programs like MobileSim. To see MobileSim's output, you can either use the --log-file option to log to a file, or run MobileSim from another command shell, such as the MSYS shell (download MSYS here).

Model Definitions

The standard Pioneer robot model definitions are in the file PioneerRobotModels.world.inc, which is installed with MobileSim (by default, in /usr/local/MobileSim on Linux and C:\Program Files\MobileRobots\MobileSim on Windows). This file is used to create the desired robot model when loading a MobileRobots/ActivMedia .map file, and you may include it in your custom Stage worlds as well. It must be present to run MobileSim. To define modified or custom robot model definitions, either modify this file, or create one of these directories:

• ~/.MobileSim/include/ if on Linux (where ~ is your home directory), or
• C:\Documents and Settings\*<Your User Name>*\MobileSim\include on Windows XP (Where is your user account name.), or
• C:\Users\*<Your User Name>*\MobileSim\include on Windows 7+ (Where is your user account name.), or

Any files MobileSim finds in this include directory (except files that begin with a dot ".") are included into the world configuration after PioneerRobotModels.world.inc. (You can also put Stage world and GUI settings, and even model instantiations into these files as well. See the Stage documentation for complete documentation of the syntax of these files.) New model definitions from these files can be used with the -r option on the command line using the model definition name, or by typing the name into the Robot Model field of MobileSim's initial dialog box.

When you define a new model, you can change the pioneer_robot_subtype property; this is the robot subtype string that ARIA uses to load client-side parameters for the robot. If you do change this value, you must also create a parameter file (.p file) for that new type in ARIA's 'params' directory.

MobileSim expects common resources like the PioneerRobotModels.world.inc file to be in the standard installation location (/usr/local/MobileSim on Linux; C:\Program Files\MobileRobots\MobileSim on Windows) unless an environment variable named MOBILESIM is set, or on Windows, in the \SOFTWARE\MobileRobots\MobileSim\Install Directory registry key. Change these if you want MobileSim to use resources in a different directory than the standard installation location.

Robot speed limits

Model definitions for robots ("position" models) have speed limits defined. This is analogous to the limits set in a real robot's firmware.

Stage Worldfile Override

Instead of using a map file and the model definitions in PioneerRobotModels.world.inc and the files in ~/.MobileSim/include, you may also simply provide a Stage-format world file with the -W or -stageworld command line options. If provided, MobileSim uses only this world file for world configuration, it does not use the common PioneerRobotModels.world.inc, or the files in your "include" directory.

Special Simulator Obstacles Objects

MobileSim includes some "box" model definitions in its model definitions file PioneerRobotModels.world.inc. These are 0.5 x 0.5 meter objects that you can place anywhere in the map, and move with the mouse during the simulation. These boxes are created in the same way as robots, using the -r command line argument. Use the --start option to choose their locations. You can create your own model definitions based on the box model type as well (e.g. with different dimensions, color, etc.) MobileSim's predefined box model types are described below:

`box`

A 0.5 x 0.5 m yellow box that is an obstacle which can also be sensed by laser and sonar.

`box-nolaser`

A 0.5 x 0.5 m yellow box that is an obstacle which can be sensed by sonar, but not lasers.

`box-nolaser-nosonar`

A 0.5 x 0.5 m yellow box that is an obstacle which can not be sensed by sonar or lasers (the robot will collide with it and trigger bumpers and stall).

`box-reflector`

A 0.5 x 0.5 m yellow box that is an obstacle which can be sensed by sonar, and by laser with a high reflectance value (2).

For example, you can create a simulation with two movable boxes and a Pioneer 3-DX robot with the following command: MobileSim -r p3dx -r box -r box

You can also define custom map object types in a map file, which will allow you to add them to that map file using Mapper3. MobileSim recognizes some additional attributes of the custom types in order to create extra objects in the simulation.

`Sim.Obstacle=`*yes|no*

If this attribute is given to a `SectorType`, then MobileSim creates an extra movable box. (Not supported yet for `BoundaryType`) If the value is `yes`, then the object will be an obstacle that the robot will collide with. If `no`, then the robot will pass through it. This attribute controls whether a box is created or not, it must be given with either a yes or no value.

`Sim.LaserReflect=`*int*

If the *int* value is greater than 1, then it will be returned to the client with laser readings, if the laser sensor model is able to detect it according to its rules for detecting reflectors. (See `Reflector` below).

If 1, it will be detected as a normal object by the laser. If 0, it will not be detected by the laser at all.

`Sim.SonarReflect=`*yes|no*

If `yes`, then the object will be detected by sonar. If `no`, then it will not be detected by sonar.`

`Reflector`

This creates a line in the map that has a higher "reflectance" value than the normal LINES data. (Note, ARIA version 2.5 or later is needed to be able to read the reflectance value data from the simulater LRF). Both sides of the line will have high reflectance.

To add these custom object type definitions to a map file, first manually edit the map to define a custom type that has a simulator specific attribute. For example, the following defines five object types:

• a normal box

• a highly reflective box

• an box that is invisible to laser and sonar but which the robot will collide with

• a box that is invisible to laser and sonar and which the robot will not collide with (it is simply visible in the simulator, this is useful as a simple marker of a place in the map)

• a reflector line

  MapInfo: SectorType Name=BoxObstacle Label=Sim_BoxObstacle Sim.Obstacle=yes MapInfo: SectorType Name=ReflectiveBoxObstacle Label=Sim_ReflectiveBoxObstacle Sim.Obstacle=yes Sim.LaserReflect=32 MapInfo: SectorType Name=InvisibleBox Label=Sim_InvisibleBox Shape=Plain Sim.Obstacle=yes Sim.LaserReflect=0 Sim.SonarReflect=no MapInfo: SectorType Name=MarkerBox Label=Sim_MarkerBox Shape=Plain Sim.Obstacle=no Sim.LaserReflect=0 Sim.SonarReflect=no MapInfo: BoundaryType Name=Reflector Label=Reflector Desc=Reflector "Color0=0xFF00FF"

You can also add attributes such as Shape, Desc, Color0 and Color1. To include spaces in the Desc or Label attributes, surround the whole key=value part in quotes (e.g. "Desc=Invisible Box for Simulator").

Once these definitions are added to a map file which is then loaded into Mapper3, then Mapper3 makes them available: in the Boundary tools for Reflector lines, and the Sector tools for boxes. You can modify the Color and Shape parameters if you would like them to be displayed differently in Mapper3. When instances of the objects are added with Mapper3 they are then added to the map file as "Cairn" map objects (similar to goals etc.).

Special Sectors in Map File

MobileSim will recognize certain special sectors if they appear in the map file. Mapper3 does not recognize all of these by default, but if you add the appropriate MapInfo lines to the map with a text editor (see below), they will appear in the "Advanced Areas" menu of Mapper3.

• BadGPSSector and SimBadGPSSector: If a map has a GPS georeference point (OriginLatLongAlt), then MobileSim will provide simulated latitude and longitude in the SIMSTAT packet (see description of SIMSTAT below.)
  If the robot is inside a BadGPSSector or SimBadGPSSector, then the value provided in SIMSTAT for the "good GPS" field will be 0. Otherwise it will be 100. ArSimulatedGPS in ARIA will use this to indicate either "NoFix" (if -1), or "SimulatedFix" (if 100) or "BadFix" (0) fix type and ideal (1.0) or bad (0.0) DOP value. MOGS uses BadGPSSector to prevent intermittent or inconsistent GPS positions from reducing navigation quality while in areas that have been marked as "known-bad" areas of GPS coverage.

To enable the creation of BadGPSSector and SimBadGPSSector in Mapper3, use a text editor to add the following lines to the map file:

MapInfo: SectorType "Name=BadGPSSector" "Label=BadGPS" "Desc=Area where GPS is known to be unreliable" "Color0=0x888888" "Color1=0xbea4ce"
MapInfo: SectorType "Name=SimBadGPSSector" "Label=SimBadGPS" "Desc=Area where GPS will be made unreliable in MobileSim" "Color0=0x779977" "Color1=0xbea4ce"

Default Map File

If you find that you are often loading the same map file into MobileSim over and over again, you can save a step by copying that map file into ~/.MobileSim (Linux) or \Documents and Settings\*<User Name>*\MobileSim (Windows) and naming it init.map. If this map file exists, MobileSim will load this map at startup if no command-line option is given, rather than dislpaying the initial Load Map File dialog box.

Exit Codes

The MobileSim process has the following exit codes:

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  0           No error      
  255 (-1)    Error in command line arguments      
  254 (-2)    Error writing a temporary file on startup      
  253 (-3)    Error loading a map file      
  252 (-4)    Error initializing Stage      
  250 (-6)    Error loading a robot parameters file (.p file) to define a robot model      
  249 (-7)    Error initializing the Pioneer emulation

thread 248 (-8) Error opening a TCP socket for a robot or factory
236 (-20) MobileSim crashed, but crash handler caught signal and logged information to log file.

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Error codes may also be requested in the SIM_EXIT command by a client (use positive error codes less than 127, to differentiate from possible MobileSim codes).

Robot Protocol Support

Currently the following parts of the ARCOS/AROS/P2OS/AmigOS/PSOS protocols are supported. This covers all robot motion commands used by ARIA (including both direct motion requests and actions), and several other features.

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Name Command # Argument Description Type

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PULSE 0 none No-op (but reset watchdog timeout)

OPEN 1 int Start up standard devices and send SIP packets

CLOSE 2 int Stop standard devices

ENABLE 4 uint Enable (1) or disable (0) motors

SONAR 28 uint Disable (0) or re-enable (1) sonar (but using argument bits 1-4 to select particular arrays is not supported)

CONFIG 18 int Request a configuration packet

STOP 29 int Stops the robot from moving

VEL 11 int Set the translational velocity (mm/sec)

ROTATE 9 int Set rotational velocity, duplicate of RVEL (deg/sec)

RVEL 21 int Set rotational velocity, duplicate of ROTATE (deg/sec)

VEL2 32 2bytes Independent wheel velocities. High 8 bits are left wheel velocity, low 8 bits are right wheel velocity.

HEAD 12 uint Turn to absolute heading 0-359 (degrees)

SETO 7 none Resets robots odometry back to 0, 0, 0

DHEAD 13 int Turn relative to current heading (degrees)

SETV 6 int Sets maximum velocity and MOVE velocity (mm/sec)

SETRV 10 int Sets the maximum rotational and HEAD velocity (deg/sec)

SETA 5 int Sets forward translational acceleration or deceleration (mm/sec/sec)

SETRA 23 int Sets rotational accel(+) or decel(-) (deg/sec)

MOVE 8 int Translational move (mm)

LATVEL 110 int Set lateral velocity (on robots that support it, i.e. Seekur)

LATACCEL 113 int Set lateral acceleration or deceleration (on robots that support it, i.e. Seekur)

BATTEST 250 int Artificially set battery voltage, in decivolts (e.g. 105 for 10.5 volts)

ESTOP/QSTOP 55 none Stop with maximum deceleration.

BUMPSTALL 44 int Configure bumpstall behavior.

TTY2 42 string Log with string contents

TTY4 60 string Log with string contents

RESET/MAINT 253/255 none Abort MobileSim for debugging. If running in noninteractive mode on Linux, restart program after logging some debugging informamtion using gdb.

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Simulator-only commands

For compatability with SRISim and old ARIA versions, equivalent commands with deprecated ID numbers are also accepted, with a warning.

MobileSim will always use the robot name "MobileSim". It will also report an OS version number starting with "S." and the string "SIM" for serial number in the CONFIGpac packet, and respond to the SIM_STAT command with a SIMSTATpac packet and the SIM_CTRL,6 command with a SIM_INFO packet. You can use these values in client software to detect whether it is connected to MobileSim or not.

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Name Command Argument Description Type

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SIM_SET_POSE 224 int4,int4,int4 Move robot to global pose in simulator (does not change odometry). The parameters are 4-byte integers for X, Y and Theta. The packet's argument type byte is ignored. Here is an example of how to send this command in ARIA, where robot is an ArRobot object, and x, y and th are int variables containing desired position in milimeters and degrees: ArRobotPacket pkt; pkt.setID(ArCommands::SIM_SET_POSE); pkt.uByteToBuf(0); // argument type: ignored. pkt.byte4ToBuf(x); pkt.byte4ToBuf(y); pkt.byte4ToBuf(th); pkt.finalizePacket(); robot.getDeviceConnection()->write(pkt.getBuf(), pkt.getLength());

SIM_RESET 225 none Move robot to original starting position in simulator (e.g. Home point or Dock) and reset odometry to 0,0,0.

SIM_LRF_ENABLE 230 int 1 to enable simulated laser rangefinder in-band (data packet ID=0x60). 2 to enable simulated LRF with extended information (data packet ID=0x61). 0 to disable LRF. See below for data packet formats.

SIM_LRF_SET_FOV_START 231 int Set start angle of laser field of view

SIM_LRF_SET_FOV_END 232 int Set end angle of laser field of view Currently start and end must be symetrical around 0. ARIA always does this, but if you want configure it differently it won't work.

SIM_LRF_SET_RES 233 int Set degree increment between each reading; with FOV, this number determines the number of readings in each sweep

SIM_CTRL 236 int,... Perform a simulator meta-operation. The initial 2-byte integer indicates the operation. The rest of the packet is operation-specific. See the description below for descriptions of operations.

SIM_STAT 237 none,1,2 or 0 Request SIMSTAT packets (ID=0x62) to be returned. See below. Argument: none or 1 to return one packet, 2 to return a packet before each SIP, or 0 to stop sending.

SIM_MESSAGE 238 byte,string... Display the length-prefixed string in the messages window.

SIM_EXIT 239 int Exit the simulator with the given exit code. Pass a positive integer < 127 as error code, or use 0 to indicate "normal" exit.

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The SIM_CTRL command performs miscellaneous simulater meta-operations. The initial 2-byte integer indicates the operation. The rest of the packet is operation-specific.

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Op # Name Description

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1 Replace Remove existing map data and load a new map from the map file given as a length-prefixed string folowing the operation code. Note: If the path is not absolute, it will be interpreted as relative to MobileSim's startup working directory, or the directory given with the --cwd command-line argument. For compatibility with Windows and other platforms with case-insensitive file naming, the case of the file name does not matter. A SIM_MAP_CHANGED packet will be sent back to any client when MobileSim is done loading a new map (see below).

2 Master Similar to 1, but once this command is received, future replace control commands with operation 1 are ignored, only operation 2 is map accepted. Use this when many clients are requesting different maps, but you want one of them (or a seperate program) to instead have control over which map is being used. A SIM_MAP_CHANGED packet will be sent back to any client when MobileSim is done loading a new map (see below).

3 Master Disable master map mode if enabled by 2 map
clear

4 Rotate If logging to a file (--log-file command-line option given), logs then close current log file, move old log files to backup files (up to 5 are kept), and open a new log file. Only implemented for Linux currently.

5 Log Log detailed internal simulation state for this robot. (For debugging, mainly.) detailed
state

6 Request Request SIMINFO packet (see below). SIMINFO packet

7 Ghost This robot will no longer be visible to other robots' sensors (laser or mode sonar), and other robots will not collide with it.

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The normal simulator laser packet is as follows:

Packet ID                ubyte=0x60
Robot X                  int   
Robot Y                  int
Robot Theta              int
Total No. Readings       int

Current int, index of the first reading given in this packet Packet Len. int, number of bytes of data that follow For each reading: Reading Range int, Range for reading ...

The extended simulator laser packet is as follows:

Packet ID                ubyte=0x61
Total No. Readings       int
Current                  int,      Index of first reading given

in this packet Packet Len. int, number of bytes of data that follow For each reading: Range int, Range for reading #i Reflectance ubyte, Reflectance value, if supported Flags 2 bytes, Reserved ...

Laser Device Index        ubyte,    Reserved
Flags                     ubyte,    Reserved

The SIMSTAT packet is as follows. New fields may be added in future versions.

Packet ID                 ubyte=0x62 (98)
unused/reserved NULL byte ubyte=0      reserved/unused
unused/reserved NULL byte ubyte=0      reserved/unused
Flags                     4ubyte       bit 0=have a map; bit 1=map has origin georeference (OriginLatLonAlt); bit 2=have odometry error data
SimInterval               2ubyte       Configured simulated time one loop interval takes
RealInterval              2ubyte       Configured real time one loop interval should take
LastInterval              2ubyte       Real time the last loop interval was measured at
True X                    4byte        Robot's "true" X position in the simulator
True Y                    4byte        Robot's "true" Y position in the simulator
True Z                    4byte        Robot's "true" Z position in the simulator
True Theta                4byte        Robot's "true" rotation on its vertical axis in the simulator
Geo Lat                   4byte        Robot's latitude (degrees * 10^6). Only valid if map has origin georeference.   
Geo Lon                   4byte        Robot's longitude (degrees * 10^6). Only valid if map has origin georeference.   
Geo Alt                   4byte        Robot's altitude (cm). Only valid if map has origin georeference.   
GPS good                  byte         Normally 100. If robot is inside a `BadGPSSector` or `SimBadGPSSector` area, will be 0.  If there is no simulated GPS (e.g. map is not georeferenced), will be -1.  

Odometry Error X 4byte mm * 10^6. See also Flags field above Odometry Error Y 4byte mm * 10^6. See also Flags field above Odometry Error Th 4byte degrees * 10^6. See also Flags field above

Here is an example of a packet handler function for ARIA that extracts some data from the SIMSTAT packet. Wrap this function in an ArFunctor object and use ArRobot::addPacketHandler() to register it with an ArRobot object.

bool handleSimStatPacket(ArRobotPacket* pkt)
{
   if(pkt->getID() != 0x62) return false; // SIMSTAT has id 0x62
   printf("SIMSTAT pkt received:\n"    );
   char a = pkt->bufToByte();  // unused byte
   char b = pkt->bufToByte();  // unused byte
   ArTypes::UByte4 flags = pkt->bufToUByte4();
   printf("\tFlags=0x%x\n", flags);
   int simint = pkt->bufToUByte2();
   int realint = pkt->bufToUByte2();
   int lastint = pkt->bufToUByte2();
   printf("\tSimInterval=%d, RealInterval=%d, LastInterval=%d.\n", simint, realint, lastint);
   int realX = pkt->bufToByte4();
   int realY = pkt->bufToByte4();
   int realZ = pkt->bufToByte4();
   int realTh = pkt->bufToByte4();
   printf("\tTrue Pose = (%d, %d, %d, %d)\n", realX, realY, realZ, realTh);
   if(flags & ArUtil::BIT1)
   {
      double lat = pkt->bufToByte4()/10e6;
      double lon = pkt->bufToByte4()/10e6;
      double alt = pkt->bufToByte4()/100;
      double qual = pkt->bufToByte()/100;
      printf("\tLatitude = %f deg., Longitude = %f deg., Altitude = %f m, Quality = %f%%\n", lat, lon, alt, qual);
   }
   else
   {
      puts("No geoposition.");
   }
   return true;
}

When connected to MobileSim and using ArGPSConnector, ARIA will create an ArSimulatedGPS object to read the simulated GPS data.

The SIMINFO packet is as follows. New fields may be added in future versions.

Packet ID                ubyte=0x63 (100)
Application name         NULL-terminated string     Name of simulator
Application version      NULL-terminated string     Version of simulator
Flags                    4ubyte                     Bit 0=Sim is interactive with user and has a GUI; Bit 1=Sim crashed last time but was automatically restarted.     
Num. Devices             4ubyte                     Number of devices attached to the robot
For each device:
  Device Name            string                      Unique name for this device
  Device Type             string                     e.g. "laser"
  Device Number           ubyte                      To distinguish individual devices of the same type
  Device Status           ubyte,ubyte,ubyte,ubyte    Device-dependent status code(s)
...

The SIM_MAP_CHANGED packet is as follows. This packet is sent to all connected clients if the map is changed or reloaded for any reason. New fields may be added in future versions.

Packet ID                ubyte=0x66 (102)
User                     ubyte. 1=Map was loaded by user command (e.g. via gui), 0=Map was loaded by client program SIM_CTRL command.
Loaded                   ubyte. 1=A new map was really loaded.  0=Map was not reloaded because already loaded and file is unchanged since last load.
Filename                 string. filename of map that was loaded.

Unsupported commands

The following commands are not supported, and will be ignored, with a warning message. Some are not applicable to the simulator (ENCODER) or pertain to devices that aren't implemented in the simulator yet (gripper, sounds).

ENCODER        19
POLLING        3
SAY            15
JOYINFO        17
DIGOUT         30
GRIPPER        33
ADSEL          35
GRIPPERVAL     36
GRIPPERPACREQUEST 37
IOREQUEST      40
PTUPOS         41
GETAUX         43
TCM2           45
JOYDRIVE       47
HOSTBAUD       50
AUX1BAUD       51
AUX2BAUD       52
GYRO           58
CALCOMP        65
TTY3           66
GETAUX2        67
SOUND          90
PLAYLIST       91
SOUNDTOG       92
OLD_LOADWORLD  63
OLD_LOADPARAM  61
OLD_STEP       64

The following commands will probably never be supported since they do nothing on modern robots or use is discouraged:

DROTATE        14
DCHEAD         22
KICK           34

These commands are supported for compatability with a previous simulator

OLD_LRF_ENABLE     35   int    Start/stop sending laser data in-band 
OLD_LRF_PARMSTART  36   int    Sets start angle 0-180 degrees; also disables laser; with #37, determines "flipped" order of readings.
OLD_LRF_PARMEND    37   int    Sets scan end angle; also disables laser; with #36, determines "flipped" order of readings.
OLD_LRF_PARMINC    38   int    Sets inter-sample angle (100ths of degree)

The following commands are normally disabled, but can be re-enabled with the --srisim-compat command-line argument:

OLD_END_SIM        62          none        Exit simulator (MobileSim exits completely). Note, this command is also used for another use on real robots and newer version of ARIA send it after connecting (so the simulator exits immediately).  You can enable the other SRISim compatability commands with `--srisim-compat`, but disable this command using `--ignore-command 62`
OLD_SETORIGINX     66          int         Set the robot's current true X, (Note, conflicts with TTY3 command)
OLD_SETORIGINY     67          int         ...Y
OLD_SETORIGINTH     68         int         ...Theta
OLD_RESET_TO_ORIGIN     69     none        Reset true X Y, TH to 0,0,0

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Copyright (C) 2011-2015 Adept Technology
Copyright (C) 2016-2017 Adept MobileRobots/Omron Adept Technology All Rights Reserved.

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