P6DOF Flight Control System Definition¶
The flight control system determines how control inputs from the active pilot object are routed/mixed to move control surfaces, throttles, or other components/controls (such as landing gear, speed brakes, etc.). Many of the control surfaces serve as inputs into aero_component objects.
- flight_controls … end_flight_controls¶
The flight_controls block defines various control surfaces/values (control_surface, control_value, and control_boolean) that control the vehicle and/or effect its performance. The flight_controls block also defines various input/signal modifiers which are referenced within the control surfaces/values (control_surface, control_value, and control_boolean) blocks. It is important to define Control Signal Modifiers before they are referenced in the Control Surfaces and Components blocks.
flight_controls // Control Signal Modifiers mapping_table ... end_mapping_table gain_table ... end_gain_table scalar_gain ... end_scalar_gain clamp_gain ... end_clamp_gain // Control Surfaces and Components control_surface ... end_control_surface control_value ... end_control_value control_boolean ... end_control_boolean end_flight_controls
Control Signal Modifiers¶
The control signal modifiers provide a means to modify control input “signals” from the active pilot object. The modifiers can be used repeatedly within the control_surface, control_value, and control_boolean blocks, as needed.
- mapping_table … end_mapping_table¶
Mapping tables are used to modify a control input signal by modulating with a control value source. The control value can be a range of sources such as mach, alpha, g-load, etc. A table defines the relationship between the control value
mapping_table <string> type ... table_data ... end_table_data end_mapping_table
- type <string>¶
This sets the type of the mapping table. Valid types include:
- mach_mapping
Uses mach as the control_value
- ktas_mapping
Uses ktas as the control_value
- alpha_mapping
Uses alpha as the control_value
- beta_mapping
Uses beta as the control_value
- g_x_load_mapping
Uses g-load-x (Nx) as the control_value
- g_y_load_mapping
Uses g-load-y (Ny) as the control_value
- g_z_load_mapping
Uses g-load-z (Nz) as the control_value
- alt_mapping
Uses altitude as the control_value
- q_mapping
Uses dynamic pressure as the control_value
- signal_mapping
Uses a signal as the control_value
- table_data¶
This table maps a signal/input to an output/value). A typical table is like this:
table_data irregular_table independent_variable control_value precision float independent_variable input precision float dependent_variable precision float control_value 0.0 input -1.0 -0.5 0.0 0.5 1.0 values -0.8 -0.4 0.0 0.4 0.8 control_value 1.0 input -1.0 -0.5 0.0 0.5 1.0 values -0.8 -0.4 0.0 0.4 0.8 control_value 2.0 input -1.0 -0.5 0.0 0.5 1.0 values -0.8 -0.4 0.0 0.4 0.8 end_irregular_table end_table_data
- gain_table … end_gain_table¶
This table maps a signal/input to an output/value). A typical table is like this:
gain_table <string> type ... simple_table # value gain -12.0 0.0 -10.0 1.0 0.00 1.0 10.0 1.0 12.0 0.8 20.0 0.1 30.0 0.0 end_simple_table end_gain_table
- scalar_gain … end_scalar_gain¶
The scalar gain consists of a name and a gain value. Once defined, a scalar gain can be used repeatedly within the control_surface, control_value, and control_boolean blocks to scale a control signal.
scalar_gain <string> gain ... end_scalar_gain
- gain <real-value>¶
This sets the gain of the scalar gain.
- clamp_gain … end_clamp_gain¶
Clamp gains are used to limit a signal between min/max values. The output of signal will be “clamped” to the minimum and maximum values.
clamp_gain <string> min_clamp ... max_clamp ... end_clamp_gain
- min_clamp <real-value>¶
This sets the minimum value that will be allowed to pass the clamp gain.
- max_clamp <real-value>¶
This sets the maximum value that will be allowed to pass the clamp gain.
Control Surfaces and Components¶
The control_surface, control_value, and control_boolean represent control surfaces and other components on the platform that produce forces and moments or control actions on the vehicle.
- control_surface … end_control_surface¶
This defines a “control surface” or other component that can produce aerodynamic effects on the platform. Control surfaces include ailerons, elevators, elevons, rudders, spoilers, speedbrakes, etc. but also include things like landing gear, which can produce drag. See Sample Control Surface for an example of a control_surface block.
Each control_surface is given a name that must be unique and must “map” to an aero_component that will produce the effect of the control_surface.
Warning
The key concept is that each control_surface in the flight_controls block should be “connected” to a corresponding aero_component.
The control_surface name and the aero_component type must match exactly and are case-sensitive.
control_surface <name-string> min_angle ... max_angle ... current_angle ... inputs ... end_inputs angle_mapping_table ... end_angle_mapping_table actuator ... end_actuator end_control_surface
- min_angle <angle-value>¶
This sets the minimum angle of this control surface.
- max_angle <angle-value>¶
This sets the maximum angle of this control surface.
- current_angle <angle-value>¶
This sets the current angle of this control surface.
- inputs … end_inputs¶
Inputs provide a means to modify a “control input/signal” from the active pilot object. If multiple inputs blocks are used, the output from each block is summed with the other inputs for a given control_surface. This can provide a means to “mix” control inputs/signals to drive a particular control surface. For example, an elevon may mix signals from stick_right and stick_back inputs to allow the elevon to be used for both pitch and roll forces/moments.
inputs control_input.. end_control_input end_inputs
- control_input … end_control_input¶
control_input <string> modifier ... end_control_input
- modifier <string>¶
- This indicates which of the Control Signal Modifiers should be used. If multiple modifier entries are present,
they are performed in succession with the result from the previous modifier serving as the input of the next, forming a “chain” of modifiers.
Warning
The key concept is that each control_input in flight_controls should be “connected” to a control_name in control_inputs.
The names must match exactly and are case-sensitive.
- angle_mapping_table … end_angle_mapping_table¶
This table provides a means to “shape” the mapping of input to control surface angle. In many situations, a non-linear mapping will be used, with a reduced slope near zero and increased slope near the endpoints. This often improves the “feel” of controls and provides more control sensitivity near the zero point. Data in the table is normalized input mapping to a control surface angle in degrees.
Sample mapping table:
angle_mapping_table #input angle_deg -1.00 -20.0 0.00 0.0 1.00 20.0 end_angle_mapping_table
In this example, a normalized input of +/- 1 results in a linear mapping to +/- 20 degrees.
- actuator¶
This allows an simple model of an actuator.
actuator max_positive_rate ... max_negative_rate ... max_angle ... min_angle ... current_angle ... end_actuator
- max_positive_rate <angle-rate-value>¶
This is the maximum rate that the actuator can move in the positive direction.
Default: 0.0
- max_negative_rate <angle-rate-value>¶
This is the maximum rate that the actuator can move in the negative direction.
Default: 0.0
- max_angle <angle-value>¶
This is the maximum angle to which the actuator can move.
Default: 0.0
- min_angle <angle-value>¶
This is the minimum angle to which the actuator can move.
Default: 0.0
- current_angle <angle-value>¶
This is the current angle of the actuator.
Default: 0.0
Sample Control Surface¶
This is a sample control surface listing:
control_surface RightElevator_TEUp
min_angle -20.0 deg
max_angle 20.0 deg
current_angle 0.0 deg
inputs
control_input StickRight
modifier Gain_40Percent
modifier Clamp_PosNegOne
end_control_input
end_inputs
inputs
control_input StickBack
modifier Gain_80Percent
modifier Clamp_PosNegOne
end_control_input
end_inputs
angle_mapping_table
#input angle_deg
-1.00 -20.000
-0.90 -12.812
-0.80 -8.744
-0.70 -5.920
-0.60 -3.958
-0.50 -2.596
-0.40 -1.650
-0.30 -0.993
-0.20 -0.537
-0.10 -0.220
-0.05 -0.100
0.00 0.000
0.05 0.100
0.10 0.220
0.20 0.537
0.30 0.993
0.40 1.650
0.50 2.596
0.60 3.958
0.70 5.920
0.80 8.744
0.90 12.812
1.00 20.000
end_angle_mapping_table
actuator
max_positive_rate 60.0 deg/sec
max_negative_rate -60.0 deg/sec
max_angle 20.0
min_angle -20.0
current_angle 0.0
end_actuator
end_control_surface
- control_value¶
This defines a “control value” that can be used to drive controls such as throttles and thrust reversers or control other objects on the platform. A control value provides a range of values, constrained by the specified limits.
control_value <string> min_value ... max_value ... current_value ... inputs ... end_inputs end_control_value
- min_value <real-value>¶
This is the minimum value of the control value.
Default: 0.0
- max_value <real-value>¶
This is the maximum value of the control value.
Default: 0.0
- current_angle <real-value>¶
This is the current angle of the control value.
Default: 0.0
- control_boolean¶
This defines a “control boolean” that can be used to drive “button”, “trigger”, and “switch” types of controls on the platform. A control boolean’s output is either true (on) or false (off).
control_boolean <string> current_value ... threshold_value ... inputs ... end_inputs end_control_boolean
- current_value <integer-value>¶
This should be ‘0’ if the control boolean is false (off) or ‘1’ if the control boolean is true (on).
Default: 0
- threshold_value <real-value>¶
This sets the value above which a signal will be considered to be true (on).
Default: 0.5
Return to p6dof_object_types or p6dof_object_type
