suboptimumg.log_analysis.understeer#

class suboptimumg.log_analysis.understeer.UndersteerResult[source]#

Bases: BaseModel

Output of measure_understeer_gradient.

Holds the fitted polynomial coefficients and goodness-of-fit statistics, plus the raw filtered arrays needed to build a diagnostic plot.

Fields#

Field

Type

Required

Default

coeffs

ndarray[tuple[Any, …], dtype[float64]]

Yes

groundspeeds

ndarray[tuple[Any, …], dtype[float64]]

Yes

lateral_accel

ndarray[tuple[Any, …], dtype[float64]]

Yes

normalized_residual_std

float

Yes

r_squared

float

Yes

steering_wheel_angles

ndarray[tuple[Any, …], dtype[float64]]

Yes

timestamps

ndarray[tuple[Any, …], dtype[float64]]

Yes

timestamps_full

ndarray[tuple[Any, …], dtype[float64]]

Yes

understeer_angle

ndarray[tuple[Any, …], dtype[float64]]

Yes
Parameters:

  • coeffs (ndarray[tuple[Any, ...], dtype[float64]])

  • r_squared (float)

  • normalized_residual_std (float)

  • lateral_accel (ndarray[tuple[Any, ...], dtype[float64]])

  • understeer_angle (ndarray[tuple[Any, ...], dtype[float64]])

  • timestamps (ndarray[tuple[Any, ...], dtype[float64]])

  • timestamps_full (ndarray[tuple[Any, ...], dtype[float64]])

  • steering_wheel_angles (ndarray[tuple[Any, ...], dtype[float64]])

  • groundspeeds (ndarray[tuple[Any, ...], dtype[float64]])

property K: float#

deg/g.

Type:

Linear understeer gradient (degree-1 coefficient). Units

coeffs: ndarray[tuple[Any, ...], dtype[float64]]#
groundspeeds: ndarray[tuple[Any, ...], dtype[float64]]#
property intercept: float#

deg.

Type:

Intercept (degree-0 coefficient). Units

lateral_accel: ndarray[tuple[Any, ...], dtype[float64]]#
normalized_residual_std: float#
r_squared: float#
steering_wheel_angles: ndarray[tuple[Any, ...], dtype[float64]]#
timestamps: ndarray[tuple[Any, ...], dtype[float64]]#
timestamps_full: ndarray[tuple[Any, ...], dtype[float64]]#
understeer_angle: ndarray[tuple[Any, ...], dtype[float64]]#
suboptimumg.log_analysis.understeer.measure_understeer_gradient(data, time_range, fit_degree=1, symmetric=False, min_lat_accel_g=0.1, force_zero_intercept=False, steering_wheel_angle='ludwig.steeringWheel.angle')[source]#

Measure the understeer gradient K from a steady-state test window.

Computes understeer_angle = |delta_bicycle| - |delta_kinematic| and fits a polynomial of fit_degree against |a_y| in g’s. The degree-1 coefficient is the understeer gradient K (deg/g). K > 0 = understeer, K < 0 = oversteer.

Requires add_groundspeed, add_curvature, add_accelerations, add_kinematic_steer_angle, and add_bicycle_steer_angle to have been run first.

Parameters:

  • data (SingleRunData)

  • time_range ((t_start_s, t_end_s)) – Analysis window in seconds.

  • fit_degree (int) – Maximum polynomial degree to use when fitting curve 1 = linear, 2 = quadratic, 3 = cubic, etc.

  • symmetric (bool) – Use only even powers (0, 2, 4, …) in the fit to enforce symmetry around a_y=0.

  • force_zero_intercept (bool) – Force the fit through the origin.

  • min_lat_accel_g (float) – Minimum lateral acceleration (Units: g) to include in the fit.

  • steering_wheel_angle (str) – Steering wheel angle channel name.

Return type:

UndersteerResult

suboptimumg.log_analysis.understeer.plot_understeer(result, test_type='constant_steer', font_config=FontConfig(large=24, medium=16, small=12), layout_config=LayoutConfig(width=1000, height=700, grid_width_per_col=400, grid_height_per_row=350, grid_horizontal_spacing=0.08, grid_vertical_spacing=0.12, margin={'l': 70, 'r': 50, 't': 90, 'b': 70}, plot_bgcolor='white', scene_bgcolor='rgba(240, 240, 240, 0.8)', title_x=0.5, title_xanchor='center', title_yanchor='top'))[source]#

Return (fit_fig, diagnostic_fig) for an UndersteerResult.

fit_fig: scatter + polynomial fit of understeer angle vs lateral acceleration. diagnostic_fig: time-series of the held-constant channel over the analysis window.

Parameters:

  • result (UndersteerResult)

  • test_type (str) – "constant_steer" or "constant_speed". Determines which channel is shown in the diagnostic figure.

  • font_config (FontConfig)

  • layout_config (LayoutConfig)

Return type:

tuple[Figure, Figure]