In this section, it will be explained the T-Rex typical mission profile and the mission phases will be detailed.
Standby phase is a preliminary phase of the operation. The guidance is a “Hold” of Pitch and Roll angles at 0 [rad], of a Ground Speed at 0 [m/s] and a fixed Yaw angle to the current one. During this phase is possible to check, for example, if the aircraft is correctly controlling the attitude by moving it and watching the servos positions changing.
Standby phase panel
Engine OFF is the phase which allows the platform decreasing main rotor RPMs without attitude changes. In fact, the decreasing phase is not instantaneous and the autopilot needs to keep the control until the RPMs would not be able to make attitude changes. Following this fact, this phase has a thrusting control set at zero and VTol and Yaw Guidances.
Thrusting fixed control
VTol Guidance settings
Yaw Guidance settings
The Guidance of this phase is a Hold which allows to mantain Roll and Pitch angles at 0 [rad] during the RPM increasing of the engine until 35 % of thrust.
Hold Guidance configuration
Engine RPM increasing settings
The ready phase is the one that starts to control RPM value with PID controller to maintain it at the desired value (Desired RPM). The Guidance a Hold of RPMs (this guidance will be present in all flight phases), and the same VTol and Yaw of the Standby phase.
Desired RPM value
RPM control loop
Take-off phase is composed by 3 Guidances: VTol, Hold (RPM) and Yaw (Current). The first one is a vertical guidance and following parameters are set:
- Line attraction: 5.0 m.
- Speed: 1.5 m/s.
- Horizontal Hover Gain: 0.3.
- Vertical Hover Gain: 2.24.
- Relative Vertical Distance: -30 m (Positive down).
Hover phase is configured to allow the helicopter maintain the position in the air. The only difference between this phase and the Take Off phase is the vertical distance value which is set at 0 [m] in this case.
Hover phase panel
In Cruise phase, the Guidance is a “Cruise”. The parameters to set are the Cruise Speeds (Cruise and Waypoint reach) and Acceleration limits.
In this case, good starting values are:
- Acceleration limit 0.1.
- Deceleration limit 0.1.
- Cruise Speed 2.0 [m/s].
- Waypoint reach speed 0.5 [m/s].
Yaw Guidance is set in order to make the helicopter controlling yaw angle following the heading angle.
Yaw Guidance panel
This phase has the same settings of the Take-off with a positive Relative vertical distance (positive down).
Landing phase panel
In Landing phase are set the same parameters of the Take Off phase. The only 2 changes are:
- Set Speed fixed at 0.6 [m/s].
- -100.0 [m] of Relative vertical distance (Positive down). In this case, we are supposing that at the instant when the Landing phase starts, the helicopter is flying at AGL < 100 [m].
Yaw Guidance is configured in order to let the helicopter with the Current yaw angle and limiting the yaw rate at 0.6 [rad/s].
Hold phase is used to perform a Stick controlled flight. The phase guidance is composed by Hold and Yaw guidances. It is a Hold which allows maintaining:
- Desired pitch at 0.0 [rad]
- Desired roll at 0.0 [rad]
- Desired Down Ground Velocity at 0.0 [m/s]
- Desired RPMs at 178.0 [rad/s]
Hold phase panel
In this way, if the stick control is not active, the helicopter will keep its position in the air without the need of phase changing. The Yaw Guidance is set on Current. In this phase, the Arcade allows controlling the platform depending on the set gains.