Simulation
__TOC__
== Introduction ==
NPS ('''N'''ew '''P'''aparazzi '''S'''imulator) is a more advanced simulator with sensor models and can use different FDM backends. By default [[JSBSim]] is used as FDM (FlightDynamicModel) backend, this allow fairly complex airframes.
JSBSim can be replaced by the FDM of your choice, e.g. YASim or a interconnection with MATLAB simulink
NPS is capable of simulating rotorcraft and fixedwing airframes, with the possibility to add more complex aircrafts/hybrids if a proper model is built using one of the FDM backends.
== Usage ==
See [[Installation|installation of Paparazzi]], [[JSBSim]] and optionally [[FlightGear]] (for visualization).
=== Configuration/Build ===
Add the '''nps''' target to your [[Airframe_Configuration|airframe]] with the fdm you want to use:
{{Box Code|conf/airframes/myaircraft.xml|
...
}}
then depending on the aircraft you want to simulate add a NPS simulator section which defines the model, actuators and sensor parameters used:
E.g for a simple quadrotor:
{{Box Code|conf/airframes/myaircraft.xml|
}}
You can also take a look at the example airframe [https://github.com/paparazzi/paparazzi/blob/master/conf/airframes/examples/quadrotor_lisa_m_2_pwm_spektrum.xml conf/airframes/examples/quadrotor_lisa_m_2_pwm_spektrum.xml] or use it for your first tests.
E.g for a fixedwing like a Bixler,Easystar, etc:
{{Box Code|conf/airframes/myaircraft.xml|
}}
* NPS_ACTUATOR_NAMES: mapping of the motors defined in the [[Rotorcraft_Configuration#Motor_Mixing|MOTOR_MIXING section]] to the actuators in the JSBSim model (the order is important, also make sure that your motors in JSBSim spin in the same direction as your real ones)
* NPS_SENSORS_PARAMS: the parameter file for the sensor simulation (noise/delay) under ''conf/simulator/nps/'' (e.g. [https://github.com/paparazzi/paparazzi/blob/master/conf/simulator/nps/nps_sensors_params_default.h nps_sensors_params_default.h])
* NPS_JSBSIM_MODEL: name of the JSBSim model in ''conf/simulator/jsbsim/aircraft/'' (e.g. [https://github.com/paparazzi/paparazzi/blob/master/conf/simulator/jsbsim/aircraft/simple_quad.xml simple_quad]), if not defined it defaults to AIRCRAFT_NAME
* NPS_JSBSIM_INIT: the xml file containing the initial conditions (location, attitude, wind) for JSBSim in ''conf/simulator/jsbsim/aircraft/'' (e.g. [https://github.com/paparazzi/paparazzi/blob/master/conf/simulator/jsbsim/aircraft/reset00.xml reset00]) This define is optional and if not specified the initial position of the aircraft will be set to the flight plan location. Prior to v5.1 this was called INITIAL_CONDITITONS.
* NPS_JSBSIM_LAUNCHSPEED: if defined this sets an initial launchspeed in m/s for fixedwings, available since v5.1.0_testing-54-g2ac094f
* NPS_JS_*: Joystick mappings, see [http://docs.paparazziuav.org/latest/nps__radio__control__joystick_8c.html]
Then build the nps target...
== Running the Simulation ==
The most convenient way to start the simulation is via the ''Simulation'' session from the [[Paparazzi Center]].
Just select e.g. the Quad_LisaM_2 example airframe and start the ''Simulation'' session with the simulator, GCS and server.
If you have added PAPARAZZI_HOME AND PAPARAZZI_SRC to the environmental variables of your terminal (See [[Installation#Environment_Variables|Setting up environment variables]]), you can also start it via the generic simulation launcher:
sw/simulator/pprzsim-launch --aircraft Quad_LisaM_2 --type nps
Prior to '''v5.0''' pprzsim-launch was not available. Click expand to see the details.
In earlier versions, start your tools (e.g. [[GCS]], [[server]] and messages) separately, then launch the nps simulator for your aircraft directly:
./var/Quad_LisaM_2/nps/simsitl
=== Options ===
Start the simulator with the ''--help'' option to list them all.
* ''--ivy_bus'': Set ivy bus broadcast address to use (default 127.255.255.255, 224.255.255.255 on OSX)
* ''--rc_script'': Execute script with specified number to emulate RC input.
* ''--js_dev'': Use joystick for radio control (specify index, normally 0), also see [[NPS#Use_a_Joystick]].
* ''--spektrum_dev'': Spektrum device to use for radio control (e.g. /dev/ttyUSB0)
* ''--fg_host'': Host for FlightGear visualization (e.g. 127.0.0.1)
* ''--fg_port'': Port on FlightGear host to connect to (Default: 5501)
* ''--fg_time_offset'': FlightGear time offset in seconds (e.g. 21600 for 6h), this is useful if it is currently night at the location you are flying and you want to add an offset to fly in daylight. (Since ''v4.9_devel_413-g9d55d6f)
=== Typical Simulation ===
In general you go through the same steps as with the real aircraft:
* It should start on the ground and you have to wait a few seconds until the AHRS is aligned.
* If you have a (simulated) RC, you can now arm the motors and fly around in manual.
* To fly autonomously, make sure your ''AUTO2'' mode is ''NAV'', you can change it in the GCS->settings->system->auto2.
** Switch to it if you are using an RC, otherwise you should already be in this mode.
** Arm your motors: either via the resurrect button or by going to the ''Start Motors'' block of the [[Flight Plans|Flight Plan]].
** Takeoff: via the takeoff button or the corresponding flight plan block.
* Do your stuff... :-)
=== Pausing or running the sim at a different speed ===
If you start the simulation from a terminal, hit ''CTRL-z'' to pause it. You can then enter a different time factor (default 1.0) to make the simulation run slower or faster than real-time. Hit enter to resume the simulation or ''CTRL-z'' again to suspend it like any normal Unix process (use the ''fg'' (foreground) command to un-suspend it again).
This simulation speed parameter ?can be edited? in a configuration file : FIXME
=== Use a Joystick ===
You can use a [[joystick]] (or connect your RC transmitter as a joystick) to control the quad in the simulator.
sw/simulator/pprzsim-launch --aircraft Quad_LisaM_2 --type nps --js_dev 0
or directly calling the nps simsitl binary:
./var/Quad_LisaM_2/nps/simsitl --js_dev 0
Joystick support uses the Simple DirectMedia Layer (SDL) library. Rather than specifying an input device name as one normally does on Linux, you just supply an index value (0, 1, 2,...) of the device you wish to use. Typically, the order of devices is the order in which you plugged them into your computer. The sim will display the name of the device being used to double check. If the -j option is used with no argument, the sim defaults to using device on index 0 (which is usually correct if you have only one joystick attached).
Also see [[Joystick#Calibration]].
=== Visualization in [[FlightGear]] ===
[[FlightGear#Installation|Install]] and [[FlightGear#Using_FlightGear_for_Visualization|start flightgear]], e.g. with a quadrotor model:
fgfs --fdm=null --native-gui=socket,in,30,,5501,udp --prop:/sim/model/path=Models/Aircraft/paparazzi/mikrokopter.xml
restart your simulator with the ''--fg_host'' option:
sw/simulator/pprzsim-launch --aircraft Quad_LisaM_2 --type nps --fg_host 127.0.0.1
=== Visualization in [[Morse]] ===
The Morse simulator can be used to make simulated (or real) rotorcraft fly inside a virtual environment where simulated sensors such as camera or laser scanners can be added and provide measurements.
=== Troubleshooting ===
* If you get an error like "JSBSim failed to open the configuration file: (null)/conf/simulator/jsbsim/aircraft/BOOZ2_A1.xml", you need to set your $PAPARAZZI_SRC and $PAPARAZZI_HOME environment variables. Add the following to your .bashrc, change paths according to where you put Paparazzi. Open a new terminal and launch the sim again.
export PAPARAZZI_SRC=~/paparazzi
export PAPARAZZI_HOME=~/paparazzi
* If you did not install the jsbsim package your JSBSim installation under /opt/jsbsim will be used and you will have to set your library path (either in your shell startup file or when running the sim on the command line), e.g.:
LD_LIBRARY_PATH=/opt/jsbsim/lib ./var/Quad_LisaM_2/nps/simsitl --fg_host 127.0.0.1
* If you get an error like "fatal error: gsl/gsl_rng.h: No such file or directory", you need to install the GNU Scientific Library and corresponding development packages (libgsl).
* If you get an error like "undefined reference to `pcre_compile'", edit file conf/Makefile.nps, look for the line that begins with LDFLAGS and add -lpcre, e.g.:
LDFLAGS += $($(TARGET).LDFLAGS) -lpcre
==== Simulating Multiple Aircraft ====
When simulating multiple aircraft, the ''-udp_broadcast'' argument needs to be specified as part of the datalink invocation:
$PAPARAZZI_HOME/sw/ground_segment/tmtc/link -udp -udp_broadcast
In the case of Mac OS X, the IP ADDR must also be specified:
$PAPARAZZI_HOME/sw/ground_segment/tmtc/link -udp -udp_broadcast -udp_broadcast_addr
You can determine the IP ADDR for your network using '''ifconfig''' command:
Based on the above sample output, the invocation would look like the following:
$PAPARAZZI_HOME/sw/ground_segment/tmtc/link -udp -udp_broadcast -udp_broadcast_addr 192.168.1.255
== Usage Examples ==
=== Plot the value of a message field ===
Start the [[RTPlotter|real-time plotter]] tool menu of [[Paparazzi Center]] or with
./sw/logalizer/plotter
for example drag the label 'int32 phi' from the ROTORCRAFT_FP message to the drawing area of the plotter
* Use the datalink to change the telemetry mode
start 'settings' ( from the tool menu of paparazzi center) or with
./sw/ground_segment/tmtc/settings -ac Quad_LisaM_2
start 'server' to dispatch datalink messages ( from the tool menu of paparazzi center) or with
./sw/ground_segment/tmtc/server
change the field "telemetry" on the first page to "Att loop" and send by pressing the green check button. The label on the left or the drop box should change to "Att loop" confirming your message has been received. "message" should now show that the message "STAB_ATTITUDE_INT" is received
=== Tuning the attitude control loop ===
Here we are going to use the simulator to demonstrate a way of tuning the attitude control loop for a multicopter (rotorcraft firmware only).
* Restart your previous session
* Set telemetry mode to "attitude_loop"
* Display two real time plotter windows
In the first one, plot the field "m_phi" from the "STAB_ATTITUDE_int" message. This is our estimation of roll angle.
On top of that, plot the field "phi" from the "STAB_ATTITUDE_REF_INT" message. This is our reference roll angle, that is, the roll value we are trying to achieve.
In the second plotter, plot the fields "delta_a_fb" and "delta_a_ff". Those are respectively the feedback and feedforward part of our roll command. The sum of those two terms is what is used as roll command.The feedforward part is the part used to follow our trajectory and the feedback part is the part used to reject perturbations.
* In "Settings", go to the "Att Loop" tab
We notice that the vehicle doesn't follow the step trajectory we are trying to make him do accurately.
Start by setting the value of the proportional gain ('pgain_phi') to 1000 instead of 400. The vehicle now follows the trajectory faster but overshoots. To prevent that, increase the value of the derivative gain ('dgain p') from 300 to 700.
If you look at the plotter where you're plotting the commands, you'll notice that during steps, the feedback command has to work hard. This means that our feedforward command is badly tuned, and namely not working hard enough. Increase the value of the feedforward gain ('ddgain p') from 300 to 540. You'll notice that now the feedback command has become marginal during the steps. This is the right value for the gain. Anything bigger will make the feedback command fight against the feedforward command during steps, anything smaller will make the feedback command have to complement the feedforward command.
[[Category:Simulation]] [[Category:Software]] [[Category:User_Documentation]]