Aircraft Propulsion Parameters¶

This file contains the parameters of the propulsion model.

The propulsion of aircraft in last_letter is modelled as the sum of separate thrusters, placed on arbitrary points on the airframe and in arbitrary orientations. In that manner, a single forward-facing motor can model an airplane power plant, just as easilly as four upwards-facing motors can be used to simulate a quadrotor.

motor/nMotors: The number of thrusters mounted on the aircraft.

chanMotor: The input channel which controls the thruster output. Set to -1 for no thruster control.

CGOffset: The location of the thrust application point in terms of the center of gravity, in X/Y/Z body frame coordinates. Negative X means that the application point is behind the CoG. Positive Y means that the point is to the right of the CoG. Negative Z means that the point is above the CoG.

mountOrientation: The rotation Roll-Pitch-Yaw (in this sequence) rotation angles which rotate the thruster body from the Body Frame to its actual Propeller Frame fixture. Since thrust is mostly generated towards the positive-x direction of the Propeller Frame, for a simplified airplane motor installation on the CoG, this should be [0.0,0.0,0.0]. Care is needed at this point, in case this thruster is gimballed. last_letter gimbals thrusters around the Propeller Frame z-axis. Consequently, mountOrientation should be selected in such a way that gimballing will end-up occuring around the correct axis.

chanGimbal: The input channel which controls the thruster gimbal. Set to -1 for no gimballing action.

gimbalAngle_max: The maximum throw angle (in radians) that the gimbal is providing when given full input.

rotationDir: The direction at which the thruster propeller is rotating. This is used both for visualization, as well as for counter-torque calculation purposes. Valid values are 1 or -1.

There are 4 types of thruster models available. These are selected with the variable motorType:

• 0: Selects dummy thruster model, which has no interactions with the surrounding air. Useful for debugging.
• 1: Beard Engine - Simplified electric motor - propeller model, as provided in the book Small Unmanned Aircraft: Theory and Practice, Randal W. Beard & Timothy W. McLain.
• 2: Internal combustion engine - This model combines an IC engine model with a propeller model. Torque curves are specified for the engine, as well as propeller power and efficiency curves.
• 3: Electric motor - This model combines an electric motor model with a propeller model. This configuration is common to many small-scale RC aircraft. A 3-parameter model is used for the electric motor and power and efficiency curves are used for the propeller modelling.

wrenchProp.force.x = 1.0/2.0*rho*s_prop*c_prop*(pow(inputMotor * k_motor,2)-pow(airspeed,2));
wrenchProp.torque.x = -rotationDir * k_t_p*pow(omega,2);