View source for Control Loops

This page presents the default control loops used by the Paparazzi airborne code for navigation, guidance and control.

= General Information =

All the possible combinations of control loops might not be fully detailed.

In the following diagrams, the block '''s''' is used for the '''derivative''' function and '''1/s''' is used for the '''integrator''' function.

The variables' names are the one used in the airborne code (written in '''C'''). Most of this name can the used capitalized in the [[Airframe Configuration]] file in order to define the default value of these variables. If in capital letters in the diagrams, the value is fixed and cannot be changed using [[Settings]] mechanism.

= Fixed-wing autopilot =

== Global view ==

[[Image:Diagram_general.png|General overview]]

The elements '''servos''', '''rc_commands''', '''commands''' and '''command_laws''' correspond to specific section of the [[Airframe Configuration]] file. Most of the code located in these blocks is generated from the xml of th configuration file.

The value '''+/-9600''' correspond to '''+/-MAX_PPRZ'''. This '''pprz''' unit is used as a normalized internal unit for input and output values of the '''control_laws''' block.

== Navigation loop ==

The navigation loop is located in '''sw/airborne/nav.*'''. The navigation routines are called from the [[Flight Plans]].

== Course loop ==

[[Image:Diagram_course_loop.png|Course loop]]

The course loop is the upper stage of the horizontal control.
It is located in '''sw/airborne/firmwares/fixedwing/stabilization/stabilization_attitude.c''' (formerly fw_h_ctl.c).

== Roll loop ==

[[Image:Diagram_roll_loop.png|Roll loop]]

The roll loop is the lower stage of the horizontal control and is used for lateral attitude stabilization. It is located in '''stabilization_attitude.c'''.
If <tt>H_CTL_ROLL_ATTITUDE_GAIN</tt> is undefined, the code will fallback to a attitude-only loop, where <tt>estimator_p</tt> is disregarded and the gain for <tt>estimator_phi</tt> is <tt>H_CTL_ROLL_PGAIN</tt>.

== Altitude loop ==

[[Image:Diagram_altitude_loop.png|Altitude loop]]

The altitude loop is the upper stage of the vertical control.
It is located in '''sw/airborne/firmwares/fixedwing/guidance/guidance_v.c''' (formerly fw_v_ctl.c)

== Auto Throttle and Auto Pitch climb loops ==

Two climb loops are available. The are called from the [[Flight Plans#Navigation_modes|flight plan]] by changing the vertical navigation mode. The default mode is '''Auto Throttle'''.

=== Auto throttle loop ===
[[Image:Diagram_auto_throttle_loop.png|Auto Throttle climb loop]]

=== Auto pitch loop ===
[[Image:Diagram_auto_pitch_loop.png|Auto Pitch climb loop]]

The climb loop is the intermediate stage of the vertical control. It is located in '''guidance_v.c'''.

== Pitch loop ==

[[Image:Diagram_pitch_loop.png|Pitch loop]]

The pitch loop is the lower stage of the vertical control and is used for longitudinal attitude stabilization. It is located in '''stabilization_attitude.c'''.

== Control loops using Airspeed Sensor ==

Adding an airspeed sensor measures actual airspeed resulting in better throttle control and aircraft performance especially in windy conditions. The control loops using an airspeed sensor are described [[Airspeed_sensor|here]].

= Multi-rotor (Booz) autopilot =

== Global View ==

[[Image:Booz_autopilot_globalview.png]]

The code for this autopilot is located in '''sw/airborne/firmwares/rotorcraft'''.

== Vertical Control ==

Depending on the general mode selected, one of the following vertical modes is used.

=== mode: GUIDANCE_V_MODE_RC_CLIMB ===

=== mode: GUIDANCE_V_MODE_CLIMB ===

=== mode: GUIDANCE_V_MODE_HOVER ===

=== mode: GUIDANCE_V_MODE_NAV ===

== Reference generators ==

=== from <math>z</math> set point ===

[[Image:Booz_refgen_z.png]]

=== from <math>\dot{z}</math> set point ===

[[Image:Booz_refgen_zd.png]]

The '''adjust accel''' is a simple algorithm to set acceleration to zero when velocity reaches boundaries.

The code for these reference generators is located in '''guidance/guidance_v_ref.h'''

== Hover loop ==

(coming soon...)

== Horizontal Control ==

Depending on the general mode selected, one of the following horizontal modes is used.

=== mode: GUIDANCE_H_MODE_RATE ===
[[Image:GUIDANCE_H_MODE_RATE.png]]

=== mode: GUIDANCE_H_MODE_ATTITUDE ===
[[Image:GUIDANCE_H_MODE_ATTITUDE.png]]

=== mode: GUIDANCE_H_MODE_HOVER ===

[[Image:GUIDANCE_H_MODE_HOVER.png]]

rotation to body:

<math>\phi_{cmd_{body}}= -\sin \psi \cdot x_{cmd_{earth}} + \cos \psi \cdot y_{cmd_{earth}} </math>

<math>\theta_{cmd_{body}}= -\left( \cos \psi \cdot x_{cmd_{earth}} + \sin \psi \cdot y_{cmd_{earth}} \right) </math>

=== mode: GUIDANCE_H_MODE_NAV ===

Horizontal navigation loop + rotation to body + ref generator + attitude loop (coming soon...)

== Reference generators ==

=== from euler attitude angle set point ===

[[Image:Booz_refgen_att.png]]

Acceleration is set to zero when rate reaches min or max value.

=== from angular rate set point ===

[[Image:Booz_refgen_rate.png]]

== Attitude loop ==

[[Image:attitude_loop.png]]

== Rate loop ==

[[Image:rate_loop.png]]

== Guidance horizontal hover loop ==

[[Image:guidance_horizontal_hover.png]]

== Guidance horizontal navigation loop ==

(coming soon...)

[[Category:Software]] [[Category:Developer_Documentation]]
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