1. Kiran Arcot EE 587: Advanced Embedded Systems Hardware in the Loop (HIL) March 5th 2014

2. Outline Introduction Hardware in the Loop (HIL)
Pieces required for HIL
HIL on the Discovery Board with PX4 Firmware
Conclusion

3. Introduction What is simulation?
Modeling of a real-world system and process
Many types of simulation
Completely in software
Simulation of collision of galaxies
Lawrence Livermore National Lab nuclear weapons simulation
Simulation in Computational Electromagnetics
Many others (Lexmark printers)
To-scale modeling and simulation
Tsunami simulation at Oregon State University

4. Introduction (cont’d)
Many types of simulation (cont’d)
Military exercises
Training and preparedness
War games
Simulation with hardware input/output
Arcade motorcycle games
Wiimote for tennis game
Occulus Rift the virtual head mounted display
Hardware in the Loop
Mostly a technique employed in real-time embedded systems

5. Hardware in the Loop (HIL)
HIL typically involves
A computer that simulates the “plant”
An embedded microcontroller
Why use HIL?
Cost of the plant is extremely high
Shorter time-to-market
Safety
Parallel development
Testing in inclement weather is made easier
Faster development of newer vehicles

6. Pieces Required for HIL
For HIL on the PX4 we need
X-Plane 10
Q Ground Control (QGC)
The STM32F4-Discovery board
Sensor
Data
MAVLINK
Control inputs
UDP
Control inputs
Control inputs
Control inputs
Control inputs
Control inputs
Control inputs
Control inputs
UDP
UDP
UDP
UDP
MAVLINK
Sensor
Data

7. X-Plane 10 X-Plane 10 Flight simulator by Laminar research
Uses something called “blade element theory” for modeling to calculate aerodynamic forces such as drag, lift in different conditions
In blade theory each wing is divided in to subsections to calculate the forces on it in real time. Then the forces are combined to figure out the overall effect on the aircraft.
Plane Maker and Airfoil Maker
HiLStar 17f is the simulation fixed wing aircraft provided by PX4 developers

8. Q Ground Control (QGC)

9. MAVLink Micro Aerial Vehicle Link By Lorenz Meier Released in 2009
Used for communication between ground stations and the micro aerial vehicle

10. MAVLink (cont’d)

11. HIL on the Discovery board
Default firmware has modules turned off

12. HIL on the Discovery board (cont’d)
Main modules are
Hil
Subscribes to attitude_control topic and publishes attitude_output
att_pos_estimator_ekf
Subscribes to sensor_combined, vehicle_gps_position, parameter_update topics and publishes vehicle_global_pos, vehicle_local_pos and vehicle_attitude topics
fw_pos_control_l1
Subscribes to vehicle_global_position, vehicle_global_position_set_triplet, vehicle_attitude etc. Publishes vehicle_attitude_setpoint

13. HIL on the Discovery board (cont’d)
Main modules are
fw_att_control
Subscribes to vehicle_attitude_setpoint, vehicle_attitude, vehicle_control_mode etc
Publishes actuator_controls_0, vehicle_attitude_setpoint_0

14. Conclusion No sensors, no problem Can test/tweak the PID loops
Can still run HIL on the Discovery board
Can test/tweak the PID loops
Can develop on $15 board as opposed to the $100-$150 PX4FMU