gazebo

Jet-plugin v1

Jets are simulated by a custom Gazebo plugin, called jets-plugin-v1. We consider as thrust the reaction force applied from the turbine to the robot link to witch the turbine is attached. The jets port should be easily usable with the WB-Toolbox block to read/write YARP ports.

Setting up env. variables

Ubuntu

Add the following lines to your .bashrc file:

# This can be either the installation directory or the build directory
export IRONCUB_INSTALL_PREFIX=<prefix>

# Gazebo related env variables (see http://gazebosim.org/tutorials?tut=components#EnvironmentVariables )
# Note: sourcing the gazebo setup.sh must be done only if it was not included before by another setup script of another project,
#       otherwise it will overwrite the Gazebo-related enviromental variables already set
source /usr/share/gazebo/setup.sh
export GAZEBO_PLUGIN_PATH=${GAZEBO_PLUGIN_PATH}:${IRONCUB_INSTALL_PREFIX}/lib

Change the line source /usr/share/gazebo/setup.sh to the appropriate line if in your system Gazebo is not installed in /usr.

Windows

Follow the instruction in the main README.

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The plugin can be used in three different ways, depending on the cmake options with which it has been compiled:

cmake option	Description
USE_NONLINEAR_JET_DYNAMICS_PLUGIN	when TRUE, the jets dynamics is simulated with a model obtained from experiment data, and assuming throttle as input. (reference)
USE_FIRST_ORDER_JET_DYNAMICS_PLUGIN	when TRUE, the jets dynamics is simulated with a simple integrator. The input is thrust derivative.
	if both previuos options are FALSE, The input is assumed to be the thrust which is instantly set to Gazebo with no dynamics.

Description

The sdf elements child of plugin supported by this plugin are:

Element name	Type	Description	Example element line
yarpConfigurationFile	Gazebo URI	Location of the YARP .ini configuration file used to store parameters of the plugin	<yarpConfigurationFile>model://flying-box-yarp/conf/jets.ini</yarpConfigurationFile>

The parameters supported by the plugin's .ini YARP configuration file are:

Parameter name	SubParameter	Type	Units	Default Value	Required	Description	Notes
input-port-name	-	string	-	-	Yes	Port name used to read the input of the jets.
thrust-port-name	-	string	-	-	Yes	Port name used to publish the current thrust provided by the jets.
d_thrust-port-name	-	string	-	-	Yes	Port name used to publish the current thrust derivative.
max-thrust-in-N	-	list of doubles	Newton	-	Yes	Maximum value of thrust provided by each jet.
inverse-time-constant-in-one-over-seconds	-	double	1/seconds	-	Yes	Inverse of the time constant of the first order dynamics of the jets (related to USE_FIRST_ORDER_JET_DYNAMICS_PLUGIN option).
link-jets		list of strings	-	-	Yes	List of SDF link names on which the jets are supposed to be attached. The force of the jet is supposed to be applied to the origin of the link frame, along the direction specified by the jet-axis option.
jet-axis		list of vectors	-	-	Yes	List of the axis along with the thrust force is applied, expressed w.r.t. the link frame. For the moment, the force of the jet is supposed to be applied only along one of the axis of the link frame.
jet-coefficients		list of vectors	-	-	Yes	List of the coefficients representing the dynamic model of the jet engines. For more details see also (reference).

Example configuration file:

input-port-name /jets/input:i
thrust-port-name /jets/thrust:o
d_thrust-port-name /jets/d_thrust:o

link-jets (JETCAT_P200-RX_FR, JETCAT_P200-RX_FL, JETCAT_P200-RX_BR, JETCAT_P200-RX_BL)
max-thrust-in-N (63.0, 63.0, 220.0, 220.0)
jet-axis ((-1.0 0.0 0.0), (1.0 0.0 0.0), (0.0 0.0 -1.0), (0.0 0.0 -1.0))

# If the inverse of the time constant is 0.0, the jets are a pure integrator
inverse-time-constant-in-one-over-seconds 0.0

#  parameters-kero
jet-coefficients ((0.306530, -0.024867, -0.973422, 0.055786, 0.022618, 0.688710, 0.038025, -0.089879, -0.001393, -0.958953),
                  (0.306530, -0.024867, -0.973422, 0.055786, 0.022618, 0.688710, 0.038025, -0.089879, -0.001393, -0.958953),
                  (0.237755, -0.012799, -0.860374, 0.023606, 0.008599, 1.139026, 0.019914, -0.050257,  0.000302, -0.692913 ),
                  (0.237755, -0.012799, -0.860374, 0.023606, 0.008599, 1.139026, 0.019914, -0.050257,  0.000302, -0.692913 ))

The ports opened by the plugin are the following:

Port name	YARP type	Unit of measurements	Description
input-port-name	yarp::sig::Vector	N, N/s or throttle %	Vector of size n_jets, defining the input to the jets dynamics.
thrust-port-name	yarp::sig::Vector	N	Vector of size n_jets, reporting the current value of the thrust provided by the jets.
d_thrust-port-name	yarp::sig::Vector	N/s	Vector of size n_jets, reporting the current value of the thrust derivative.

References

@ARTICLE{8977379,
  author={L’Erario, Giuseppe and Fiorio, Luca and Nava, Gabriele and Bergonti, Fabio and Mohamed, Hosameldin Awadalla Omer and Benenati, Emilio and Traversaro, Silvio and Pucci, Daniele},
  journal={IEEE Robotics and Automation Letters}, 
  title={Modeling, Identification and Control of Model Jet Engines for Jet Powered Robotics}, 
  year={2020},
  volume={5},
  number={2},
  pages={2070-2077},
  doi={10.1109/LRA.2020.2970572}}