def test_basic_math(types):
for x in types["all"]:
for y in types["all"]:
### Arithmetic
x + y
x - y
x * y
x / y
np.sum(x) # Sum of all entries of array-like object x
### Exponentials & Powers
x**y
np.power(x, y)
np.exp(x)
np.log(x)
np.log10(x)
np.sqrt(x) # Note: do x ** 0.5 rather than np.sqrt(x).
### Trig
np.sin(x)
np.cos(x)
np.tan(x)
np.arcsin(x)
np.arccos(x)
np.arctan(x)
np.arctan2(y, x)
np.sinh(x)
np.cosh(x)
np.tanh(x)
np.arcsinh(x)
np.arccosh(x)
np.arctanh(x - 0.5) # `- 0.5` to give valid argument
def indicial_gust_response(
reduced_time: Union[float, np.ndarray],
gust_velocity: float,
plate_velocity: float,
angle_of_attack: float = 0, # In degrees
chord: float = 1):
"""
Computes the evolution of the lift coefficient of a flat plate entering a
an infinitely long, sharp step gust (Heaveside function) at a constant angle of attack.
Reduced_time = 0 corresponds to the instance the gust is entered
(Leishman, Principles of Helicopter Aerodynamics, S8.10,S8.11)
Args:
reduced_time (float,np.ndarray) : Reduced time, equal to the number of semichords travelled. See function reduced_time
gust_velocity (float) : velocity in m/s of the top hat gust
velocity (float) : velocity of the thin airfoil entering the gust
angle_of_attack (float) : The angle of attack, in degrees
chord (float) : The chord of the plate in meters
"""
angle_of_attack_radians = np.deg2rad(angle_of_attack)
offset = chord / 2 * (1 - np.cos(angle_of_attack_radians))
return (2 * np.pi * np.arctan(gust_velocity / plate_velocity) *
np.cos(angle_of_attack_radians) *
kussners_function(reduced_time - offset))
def sigmoid(
x,
sigmoid_type: str = "tanh",
normalization_range: Tuple[Union[float, int], Union[float, int]] = (0, 1)
):
"""
A sigmoid function. From Wikipedia (https://en.wikipedia.org/wiki/Sigmoid_function):
A sigmoid function is a mathematical function having a characteristic "S"-shaped curve
or sigmoid curve.
Args:
x: The input
sigmoid_type: Type of sigmoid function to use [str]. Can be one of:
* "tanh" or "logistic" (same thing)
* "arctan"
* "polynomial"
normalization_type: Range in which to normalize the sigmoid, shorthanded here in the
documentation as "N". This parameter is given as a two-element tuple (min, max).
After normalization:
>>> sigmoid(-Inf) == normalization_range[0]
>>> sigmoid(Inf) == normalization_range[1]
* In the special case of N = (0, 1):
>>> sigmoid(-Inf) == 0
>>> sigmoid(Inf) == 1
>>> sigmoid(0) == 0.5
>>> d(sigmoid)/dx at x=0 == 0.5
* In the special case of N = (-1, 1):
>>> sigmoid(-Inf) == -1
>>> sigmoid(Inf) == 1
>>> sigmoid(0) == 0
>>> d(sigmoid)/dx at x=0 == 1
Returns: The value of the sigmoid.
"""
### Sigmoid equations given here under the (-1, 1) normalization:
if sigmoid_type == ("tanh" or "logistic"):
# Note: tanh(x) is simply a scaled and shifted version of a logistic curve; after
# normalization these functions are identical.
s = _np.tanh(x)
elif sigmoid_type == "arctan":
s = 2 / _np.pi * _np.arctan(_np.pi / 2 * x)
elif sigmoid_type == "polynomial":
s = x / (1 + x ** 2) ** 0.5
else:
raise ValueError("Bad value of parameter 'type'!")
### Normalize
min = normalization_range[0]
max = normalization_range[1]
s_normalized = s * (max - min) / 2 + (max + min) / 2
return s_normalized
def calculate_kussner_lift_coefficient(reduced_time: Union[float, np.ndarray],
gust_strength: float, velocity: float):
"""
Computes the evolution of the lift coefficient of a flat plate entering a sharp, transverse, top hat gust
Reduced_time = 0 corresponds to the instance the gust is entered
(Leishman, Principles of Helicopter Aerodynamics, S8.10,S8.11)
Args:
reduced_time (float,np.ndarray) : Reduced time, equal to the number of semichords travelled. See function reduced_time
gust_strength (float) : velocity in m/s of the top hat gust
velocity (float) : velocity of the thin airfoil entering the gust
"""
return 2 * np.pi * np.arctan(
gust_strength / velocity) * kussners_function(reduced_time)
def get_NACA_coordinates(
name: str = 'naca2412',
n_points_per_side: int = _default_n_points_per_side) -> np.ndarray:
"""
Returns the coordinates of a specified 4-digit NACA airfoil.
Args:
name: Name of the NACA airfoil.
n_points_per_side: Number of points per side of the airfoil (top/bottom).
Returns: The coordinates of the airfoil as a Nx2 ndarray [x, y]
"""
name = name.lower().strip()
if not "naca" in name:
raise ValueError("Not a NACA airfoil!")
nacanumber = name.split("naca")[1]
if not nacanumber.isdigit():
raise ValueError("Couldn't parse the number of the NACA airfoil!")
if not len(nacanumber) == 4:
raise NotImplementedError(
"Only 4-digit NACA airfoils are currently supported!")
# Parse
max_camber = int(nacanumber[0]) * 0.01
camber_loc = int(nacanumber[1]) * 0.1
thickness = int(nacanumber[2:]) * 0.01
# Referencing https://en.wikipedia.org/wiki/NACA_airfoil#Equation_for_a_cambered_4-digit_NACA_airfoil
# from here on out
# Make uncambered coordinates
x_t = np.cosspace(0, 1,
n_points_per_side) # Generate some cosine-spaced points
y_t = 5 * thickness * (
+0.2969 * x_t**0.5 - 0.1260 * x_t - 0.3516 * x_t**2 + 0.2843 * x_t**3 -
0.1015 * x_t**4 # 0.1015 is original, #0.1036 for sharp TE
)
if camber_loc == 0:
camber_loc = 0.5 # prevents divide by zero errors for things like naca0012's.
# Get camber
y_c = np.where(
x_t <= camber_loc,
max_camber / camber_loc**2 * (2 * camber_loc * x_t - x_t**2),
max_camber / (1 - camber_loc)**2 *
((1 - 2 * camber_loc) + 2 * camber_loc * x_t - x_t**2))
# Get camber slope
dycdx = np.where(x_t <= camber_loc,
2 * max_camber / camber_loc**2 * (camber_loc - x_t),
2 * max_camber / (1 - camber_loc)**2 * (camber_loc - x_t))
theta = np.arctan(dycdx)
# Combine everything
x_U = x_t - y_t * np.sin(theta)
x_L = x_t + y_t * np.sin(theta)
y_U = y_c + y_t * np.cos(theta)
y_L = y_c - y_t * np.cos(theta)
# Flip upper surface so it's back to front
x_U, y_U = x_U[::-1], y_U[::-1]
# Trim 1 point from lower surface so there's no overlap
x_L, y_L = x_L[1:], y_L[1:]
x = np.hstack((x_U, x_L))
y = np.hstack((y_U, y_L))
return stack_coordinates(x, y)
def draw_bending(self,
show=True,
for_print=False,
equal_scale=True,
):
"""
Draws a figure that illustrates some bending properties. Must be called on a solved object (i.e. using the substitute_sol method).
:param show: Whether or not to show the figure [boolean]
:param for_print: Whether or not the figure should be shaped for printing in a paper [boolean]
:param equal_scale: Whether or not to make the displacement plot have equal scale (i.e. true deformation only)
:return:
"""
import matplotlib.pyplot as plt
import seaborn as sns
sns.set(font_scale=1)
fig, ax = plt.subplots(
2 if not for_print else 3,
3 if not for_print else 2,
figsize=(
10 if not for_print else 6,
6 if not for_print else 6
),
dpi=200
)
plt.subplot(231) if not for_print else plt.subplot(321)
plt.plot(self.x, self.u, '.-')
plt.xlabel(r"$x$ [m]")
plt.ylabel(r"$u$ [m]")
plt.title("Displacement (Bending)")
if equal_scale:
plt.axis("equal")
plt.subplot(232) if not for_print else plt.subplot(322)
plt.plot(self.x, np.arctan(self.du) * 180 / np.pi, '.-')
plt.xlabel(r"$x$ [m]")
plt.ylabel(r"Local Slope [deg]")
plt.title("Slope")
plt.subplot(233) if not for_print else plt.subplot(323)
plt.plot(self.x, self.force_per_unit_length, '.-')
plt.xlabel(r"$x$ [m]")
plt.ylabel(r"$q$ [N/m]")
plt.title("Local Load per Unit Span")
plt.subplot(234) if not for_print else plt.subplot(324)
plt.plot(self.x, self.stress_axial / 1e6, '.-')
plt.xlabel(r"$x$ [m]")
plt.ylabel("Axial Stress [MPa]")
plt.title("Axial Stress")
plt.subplot(235) if not for_print else plt.subplot(325)
plt.plot(self.x, self.dEIddu, '.-')
plt.xlabel(r"$x$ [m]")
plt.ylabel(r"$F$ [N]")
plt.title("Shear Force")
plt.subplot(236) if not for_print else plt.subplot(326)
plt.plot(self.x, self.nominal_diameter, '.-')
plt.xlabel(r"$x$ [m]")
plt.ylabel("Diameter [m]")
plt.title("Optimal Spar Diameter")
plt.tight_layout()
plt.show() if show else None
def performance(
self,
speed,
throttle_state=1,
grade=0,
headwind=0,
):
##### Figure out electric thrust force
wheel_radius = self.wheel_diameter / 2
wheel_rads_per_sec = speed / wheel_radius
wheel_rpm = wheel_rads_per_sec * 30 / np.pi
motor_rpm = wheel_rpm / self.gear_ratio
### Limit performance by either max voltage or max current
perf_via_max_voltage = self.motor.performance(
voltage=self.max_voltage,
rpm=motor_rpm,
)
perf_via_throttle = self.motor.performance(
current=self.max_current * throttle_state,
rpm=motor_rpm,
)
if perf_via_max_voltage['torque'] > perf_via_throttle['torque']:
perf = perf_via_throttle
else:
perf = perf_via_max_voltage
motor_torque = perf['torque']
wheel_torque = motor_torque / self.gear_ratio
wheel_force = wheel_torque / wheel_radius
thrust = wheel_force
##### Gravity
gravity_drag = 9.81 * np.sin(np.arctan(grade)) * self.mass
##### Rolling Resistance
# Crr = 0.0020 # Concrete
Crr = 0.0050 # Asphalt
# Crr = 0.0060 # Gravel
# Crr = 0.0070 # Grass
# Crr = 0.0200 # Off-road
# Crr = 0.0300 # Sand
rolling_drag = 9.81 * np.cos(np.arctan(grade)) * self.mass * Crr
##### Aerodynamics
# CDA = 0.408 # Tops
CDA = 0.324 # Hoods
# CDA = 0.307 # Drops
# CDA = 0.2914 # Aerobars
eff_speed = speed + headwind
air_drag = 0.5 * atmo.density() * eff_speed * np.abs(eff_speed) * CDA
##### Summation
net_force = thrust - gravity_drag - rolling_drag - air_drag
net_accel = net_force / self.mass
return {
"net acceleration": net_accel,
"motor state": perf,
}
