Types

Settings of the FlightPathController.

Loaded from the YAML file returned by fpc_settings() (typically data/fpc_settings.yaml). Construct with FPCSettings(true; dt) to auto-load from disk, or FPCSettings(; dt) for defaults.

Fields

• dt::Float64: controller sample period [s].
• log_level::Int64: logging verbosity (0 = silent, 2 = default).
• prn::Bool: enable general debug printing.
• prn_ndi_gain::Bool: print NDI gain each step.
• prn_est_psi_dot::Bool: print estimated turn rate each step.
• prn_va::Bool: print apparent wind speed each step.
• use_radius::Bool: use turn-radius control mode instead of heading-rate mode.
• use_chi: use course angle χ as the controlled variable instead of heading ψ.
• reset_int1::Bool: reset the main integrator to the last estimated turn rate on state entry.
• reset_int2::Bool: reset the D-term integrator at the second time step after a state transition.
• reset_int1_to_zero::Bool: reset the main integrator to zero (overrides reset_int1).
• init_opt_to_zero::Bool: initialize the root-finder with zero instead of the previous solution.
• p: proportional gain of the PID controller.
• i: integral gain of the PID controller.
• d: derivative gain of the PID controller.
• gain: common scaling factor applied to all of P, I and D.
• c1: NDI model coefficient c₁ (default ≈ 0.0613).
• c2: NDI model coefficient c₂ (default ≈ 1.226).
• k_c1: correction factor for the NDI c₁ term; increase to enlarge the turn radius.
• k_c2: c₂ scaling factor used during the reel-out phase.
• k_c2_high: c₂ scaling factor for reel-out at high elevation angles.
• k_c2_int: c₂ scaling factor for the intermediate phases (LOW_RIGHT, LOW_TURN, LOW_LEFT).
• k_ds: influence of the depower angle on the steering sensitivity.

Settings of the FlightPathPlanner.

Loaded from the YAML file returned by fpp_settings() (typically data/fpp_settings.yaml). Construct with FPPSettings(true) to auto-load from disk, or FPPSettings() for defaults.

Fields

• log_level::Int64: logging verbosity (0 = silent, 2 = default).
• min_depower::Float64: minimum depower during reel-out [%].
• max_depower::Float64: maximum depower during reel-in [%].
• parking_depower::Float64: depower level used while parking [%].
• min_length::Float64: lower tether-length limit for the reel-in/reel-out cycle [m].
• max_length::Float64: upper tether-length limit for the reel-in/reel-out cycle [m].
• max_height::Float64: maximum allowed kite height [m].
• beta_set::Float64: target elevation angle for the figure-of-eight centre point [°].
• w_fig::Float64: half-width of the figure-of-eight pattern [°].
• psi_dot_max::Float64: maximum turn rate of the kite [rad/s].
• r_min::Float64: minimal turn radius [°].
• r_max::Float64: maximal turn radius [°].
• heading_offset_low::Float64: heading lead angle before finishing right/left turns [°].
• heading_offset_int::Float64: heading lead angle for the turn around the intermediate point [°].
• heading_offset_high::Float64: heading lead angle for elevation angles > 47.5° [°].
• heading_offset_up::Float64: heading lead angle before finishing the up-turn [°].
• heading_upper_turn::Float64: heading angle that triggers the upper turn [°].
• k_factor::Float64: scaling factor for the attractor distance.
• timeout::Float64: maximum number of time steps allowed in a single planner state before a forced transition.
• corr_vec::Vector{Float64}: elevation-angle correction look-up table (12 entries).

SystemState

Top-level system state enum used by SystemStateControl.

Values: ssManualOperation, ssParking, ssPowerProduction, ssReelIn, ssWinchControl, ssPower, ssKiteReelOut, ssIntermediate, ssWaitUntil, ssDepower, ssLaunching, ssLanding, ssEmergencyLanding, ssTouchdown.

FlightPathPlanner

Top-level flight path planner as specified in chapter 5 of the PhD thesis of Uwe Fechner.

Manages the sequence of flight path phases (power, turns, intermediate, depower, parking) by running a state machine whose transitions are evaluated on every call to on_new_data. It drives the FlightPathCalculator, and thereby the FlightPathController, with appropriate attractor points or turn-rate commands.

Fields

• fpps::FPPSettings: flight path planner settings (geometry, limits, PID gains).
• fpca::FlightPathCalculator: the associated flight path calculator.
• corr_vec::Vector{Float64}: elevation-angle correction look-up vector (loaded from fpps.corr_vec).
• _state::FPPS: current planner state (one of the FPPS enum values); starts at INITIAL.
• delta_depower: additional depower offset applied when generated power is too high.
• const_dd: depower interpolation coefficient δ_d (default 0.7).
• u_d_ro: relative depower during reel-out (0.01 * fpps.min_depower).
• u_d_ri: relative depower during reel-in (0.01 * fpps.max_depower).
• u_d_pa: relative depower during parking (default 0.25).
• l_low: lower tether-length limit for the reel-in/reel-out cycle [m].
• l_up: upper tether-length limit for the reel-in/reel-out cycle [m].
• z_up: maximum allowed kite height [m].
• count: general-purpose iteration counter.
• finish::Bool: flag set when the current reel-out cycle should finish after returning to centre.
• last_phi: azimuth angle from the previous time step [°], used for zero-crossing detection.
• timeout: counter incremented each call to on_new_data; reset on every state transition.

FlightPathCalculator

Computes the planned figure-of-eight flight path attractor points and the angular speed of the kite (omega) on the unit sphere. A new path is calculated:

• at the beginning of the reel-out phase (when onNewSystemState(ssIntermediate) is called)
• when the elevation set-point changes (call publish(beta_set))

See also docs/planned_flight_path.png.

FlightPathController as specified in chapter six of the PhD thesis of Uwe Fechner.

Main inputs are calls to the functions:

• on_control_command()`
• on_est_sys_state()

Main output is the set value of the steering u_s, returned by the method:

• calc_steering()

Once per time step the method

• on_timer()

must be called.

See also: docs/flight_path_controller_I.png and docs/flight_path_controller_II.png and docs/flight_path_controller_III.png

Fields

• fcs::FPCSettings: settings of the flight path controller.
• count::Int64: cycle counter used for periodic debug output.
• attractor::MVector{2, Float64}: current attractor point [azimuth, elevation] in radians.
• psi_dot_set: desired turn rate [rad/s], or nothing when navigating to an attractor.
• psi_dot_set_final: final desired turn rate [rad/s] after the low-pass filter settles.
• phi: azimuth angle of the kite [rad].
• beta: elevation angle of the kite [rad].
• psi: heading of the kite [rad].
• chi: course (track angle) of the kite [rad].
• chi_factor: blending weight between heading and course (0 = heading only, 1 = course only).
• omega: angular velocity of the kite on the unit sphere [°/s].
• est_psi_dot: estimated turn rate based on heading change [rad/s].
• est_chi_dot: estimated turn rate based on course change [rad/s].
• chi_set: desired flight direction (bearing) computed by navigate() [rad].
• u_d0: minimum depower setting (fully powered kite).
• u_d_max: maximum depower setting (fully depowered kite).
• u_d_prime: normalized depower setting in [0, 1].
• u_s_max: saturation limit for the steering output.
• psi_dot_max: saturation limit for the commanded turn rate [rad/s].
• u_d: actual depower setting in [0, 1].
• k_c2: active c₂ scaling factor for reel-out phase (copied from fcs.k_c2).
• k_c2_int: active c₂ scaling factor for intermediate phases (copied from fcs.k_c2_int).
• k_c2_hight: active c₂ scaling factor for high-elevation reel-out (copied from fcs.k_c2_high).
• c1: effective NDI coefficient c₁ = fcs.c1 * fcs.k_c1 [rad/m].
• c2: effective NDI coefficient c₂ (updated each step based on apparent wind speed).
• intermediate::Bool: true while in an intermediate planner phase (LOW_*).
• va: apparent wind speed at the kite [m/s].
• va_av: low-pass filtered apparent wind speed [m/s].
• va_min: minimum apparent wind speed used for full NDI [m/s].
• ndi_gain: quotient of NDI output over input (used for anti-windup).
• int::Integrator: integrator for the I term of the PID controller.
• int2::Integrator: integrator for the D term of the PID controller.
• k_u: anti-windup gain for the saturated steering signal.
• k_psi: anti-windup gain for the saturated turn rate.
• err: heading/course error fed into the PID controller [rad].
• res::MVector{2, Float64}: residual vector of the nonlinear solver.
• u_s: steering output of the FPC in [-1, 1].
• k_psi_out, k_u_out, k_psi_in, k_u_in: internal anti-windup signals.
• int_in, int2_in: inputs to the I and D integrators (for logging).
• reset_int1::Bool: flag to reset the main integrator at the next calc_steering call.
• radius: commanded turn radius [m], or nothing when not in radius-control mode.
• _n: filter coefficient for the discrete derivative in the D term.
• _i: call counter for calc_steering; used to trigger one-shot initializations.

SystemStateControl

Highest-level state machine that coordinates the winch controller and the flight path planner. It exposes a small set of commands (on_autopilot, on_parking, on_reelin, on_stop, on_winchcontrol) that trigger state transitions, and two outputs per time step: the winch speed set-point (calc_v_set) and the steering signal (calc_steering).

Construct via:

ssc = SystemStateControl(wcs::WCSettings, fcs::FPCSettings, fpps::FPPSettings;
                         u_d0, u_d, v_wind)

KiteObserver

Collects flight path statistics from a simulation log to enable correction of the elevation profile over successive figure-of-eight cycles.

Construct with KiteObserver(), then call observe!(ob, log) to populate.