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"""
MIT License
Copyright (c) 2018 Roger Cheng
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
"""
import math
import logging
import configuration
import roboclaw_wrapper
import adafruit_servo_wrapper
import lewansoul_wrapper
# Python 2 does not have a constant for infinity. (Python 3 added math.inf.)
infinity = float("inf")
class roverwheel:
"""
Rover wheel class tracks information specific to a particular wheel on
the chassis.
"""
def __init__(self, name, x=0, y=0, rollingcontrol=None,rollingparam=None,
steeringcontrol=None, steeringparam=None):
# String is used to identify this wheel in various operations. Bonus if
# the words make sense to a human reader ('front_left') but not required.
self.name = name
# X,Y coordinate of this wheel on the rover chassis, relative to center.
self.x = x
self.y = y
# Rolling velocity motor (optional): a reference to the control object and
# the parameters to identify this wheel to the control.
self.rollingcontrol = rollingcontrol
self.rollingparam = rollingparam
# Steering angle motor (optiona): similar to the above, but for steering.
self.steeringcontrol = steeringcontrol
self.steeringparam = steeringparam
# The most recently commanded steering angle and rolling velocity
self.angle = 0
self.velocity = 0
# If we were given a rolling velocity control, run any initialization we
# need and obtain its label string to show to user.
if self.rollingcontrol:
self.rollingcontrol.init_velocity(self.rollingparam)
try:
self.rollinglabel = self.rollingcontrol.version(self.rollingparam)
except ValueError as ve:
self.rollinglabel = "(No Response)"
# Repeat the above, this time for steering angle control.
if self.steeringcontrol:
self.steeringcontrol.init_angle(self.steeringparam)
try:
self.steeringlabel = self.steeringcontrol.version(self.steeringparam)
except ValueError as ve:
self.steeringlabel = "(No Response)"
def poweroff(self):
"""
Instructs the motor controller to stop rolling, stop holding position,
whatever is the least-effort situation. (If applicable)
"""
self.velocity = 0
if self.rollingcontrol:
self.rollingcontrol.power_percent(self.rollingparam, 0)
# Killing the power leaves the angle wherever it was last (except as
# moved by external forces) so leave self.angle alone.
if self.steeringcontrol:
self.steeringcontrol.power_percent(self.steeringparam, 0)
def anglevelocity(self):
"""
Send the dictated angle and velocity to their respective controls
"""
if self.rollingcontrol:
self.rollingcontrol.velocity(self.rollingparam, self.velocity)
if self.steeringcontrol:
self.steeringcontrol.angle(self.steeringparam, self.angle)
def steerto(self, angle):
"""
Steer this wheel to the specified angle. Caller is responsible for
validation of all parameters.
"""
self.steeringcontrol.angle(self.steeringparam, angle)
def steersetzero(self):
"""
Set the current steering angle of this wheel as the new zero. Caller is
responsible for validation of all parameters
"""
self.steeringcontrol.steer_setzero(self.steeringparam)
def motor_voltage(self):
"""
Query the rolling and steering motor controllers for their current input
voltage levels
"""
voltages = dict()
if self.rollingcontrol:
voltages["Rolling"] = self.rollingcontrol.input_voltage(self.rollingparam)
else:
voltages["Rolling"] = "Not Applicable"
if self.steeringcontrol:
voltages["Steering"] = self.steeringcontrol.input_voltage(self.steeringparam)
else:
voltages["Steering"] = "Not Applicable"
return voltages
class chassis:
"""
Rover chassis class tracks the physical geometry of the chassis and uses
that informaton to calculate Ackerman steering angles and relative
velocity for wheel travel
"""
def __init__(self):
# List of wheels
# Each wheel is a dictionary mapping name of a wheel to its specific info.
self.wheels = dict()
# When turning radius grows beyond this point, the wheel angles are so
# miniscule it is indistinguishable from straight line travel. This hard
# coded default can be updated based on chassis config by calling
# calculate_radius_min_max()
self.maxRadius = 250
# Radius representing the tightest turn this chassis can make. Minimum
# value of zero indicates chassis is capable of turning in place.
# This hard coded default value can be updated based on chassis config by
# calling calculate_radius_min_max()
self.minRadius = 17.75
# The current (velocity, radius) that dictated wheel angle and velocity.
# Velocity unit is up to the caller, math works regardless of units
# inches, metric, quadrature pulses, etc.
# Radius unit must match those used to specify wheel coordinates.
self.currentMotion = (0, infinity)
# A dictionary mapping a name string identifying a motor controller type
# to an instance of the motor controller.
self.motorcontrollers = dict()
def init_motorcontrollers(self):
"""
Creates the dictionary where a name in the configuration file can be
matched with its corresponding motor controller.
"""
try:
# Each instance of this class represents one group of RoboClaw connected
# together on the same packet serial network. Up to eight addressible
# RoboClaws and two motors per controller = up to 16 motors.
rclaw = roboclaw_wrapper.roboclaw_wrapper()
rclaw.connect()
self.motorcontrollers['roboclaw'] = rclaw
except ValueError as ve:
logging.getLogger(__name__).error("Unable to initialize roboclaw: %s",str(ve))
try:
asw = adafruit_servo_wrapper.adafruit_servo_wrapper()
asw.connect()
self.motorcontrollers['adafruit_servo'] = asw
except StandardError as se:
logging.getLogger(__name__).error("Unable to initialize Adafruit Servo HAT library: %s",str(se))
try:
lws = lewansoul_wrapper.lewansoul_wrapper()
lws.connect()
self.motorcontrollers['lewansoul'] = lws
except StandardError as se:
logging.getLogger(__name__).error("Unable to initialize LewanSoul Servo Library: %s",str(se))
def ensureready(self):
"""
Makes sure this chassis class is ready for work by ensuring the required
information is loaded and ready.
"""
if len(self.wheels) > 0:
return
# Initialize motor controller dictionary.
self.init_motorcontrollers()
# Load configuration from JSON.
config = configuration.configuration("roverchassis")
wheeljson = config.load()
# Using the data in configuration JSON file, create a wheel object.
for wheel in wheeljson:
# Retrieve name and verify uniqueness.
name = wheel['name']
if name in self.wheels:
raise ValueError("Duplicate wheel name {} encountered.".format(name))
# Initialize all optional motor control values to None
steeringcontrol = None
steeringparam = None
rollingcontrol = None
rollingparam = None
# Fill in any rolling velocity motor control and associated parameters
rolling = wheel['rolling']
if rolling:
rollingtype = rolling[0]
if len(rolling) == 2:
rollingparam = rolling[1]
else:
rollingparam = rolling[1:]
if rollingtype in self.motorcontrollers:
rollingcontrol = self.motorcontrollers[rollingtype]
else:
raise ValueError("Unknown motor control type")
# Fill in any steering angle motor control and associated parameters
steering = wheel['steering']
if steering:
steeringtype = steering[0]
if len(steering) == 2:
steeringparam = steering[1]
else:
steeringparam = steering[1:]
if steeringtype in self.motorcontrollers:
steeringcontrol = self.motorcontrollers[steeringtype]
else:
raise ValueError("Unknown motor control type")
# Add the newly created roverwheel object to wheels dictionary.
self.wheels[name] = roverwheel(name, wheel['x'], wheel['y'],
rollingcontrol, rollingparam, steeringcontrol, steeringparam)
# Update radius min/max based on the rover chassis configuration info
self.calculate_radius_min_max()
# Wheels are initialized, set everything to zero.
self.move_velocity_radius(0)
def move_velocity_radius(self, velocity, radius=infinity):
"""
Given the desired velocity and turning radius, update the angle and
velocity required for each wheel to perform the desired motion.
Velocity and radius is given relative to rover center.
Radius of zero indicates a turn-in-place movement. (Not yet implemented)
Radius of infinity indicates movement in a straight line.
"""
if abs(radius) < self.minRadius:
# This chassis configuration could not make that tight of a turn.
raise ValueError("Radius below minimum")
if abs(velocity) > 100:
raise ValueError("Velocity percentage may not exceed 100")
self.currentMotion = (velocity, radius)
if radius > self.maxRadius:
# Straight line travel
for wheel in self.wheels.values():
wheel.angle = 0
wheel.velocity = velocity
else:
# Calculate angle and velocity for each wheel
for wheel in self.wheels.values():
# Dimensions of triangle representing the wheel. Used for calculations
# in form of opposite, adjacent, and hypotenuse
opp = wheel.y
adj = radius-wheel.x
hyp = math.sqrt(pow(opp,2) + pow(adj,2))
# Calculate wheel steering angle to execute the commanded motion.
if adj == 0:
wheel.angle = 90
else:
wheel.angle = math.degrees(math.atan(float(opp)/float(adj)))
# Calculate wheel rolling velocity to execute the commanded motion.
if radius == 0:
wheel.velocity = 0 # TODO: Velocity calculation for spin-in-place where radius is zero
else:
wheel.velocity = velocity * hyp/abs(radius)
# If center of rotation is within the wheel track, and between the
# wheel and the origin, then this wheel will need to turn in the
# opposite direction so the rover body can turn about the center.
if (radius < 0 and wheel.x < 0 and wheel.x < radius) or (radius > 0 and wheel.x > 0 and wheel.x > radius):
wheel.velocity = -wheel.velocity
# Go back and normalize al the wheel roll rate magnitude so they are at or
# below target velocity while maintaining relative ratios between their rates.
maxCalculated = 0
for wheel in self.wheels.values():
if abs(wheel.velocity) > maxCalculated:
maxCalculated = abs(wheel.velocity)
if maxCalculated > velocity:
# At least one wheel exceeded specified maxVelocity, calculate
# normalization ratio and apply to every wheel.
reductionRatio = abs(velocity)/float(maxCalculated)
for wheel in self.wheels.values():
wheel.velocity = wheel.velocity * reductionRatio
# We're sending commands for a particular wheel - steering and rolling
# velocity - before we move on to the next wheel. If this causes timing
# issues (wheels start moving before they've finished pointing in the
# right direction, etc.) we may have to send all steering commands first,
# wait until we reach the angles, before sending velocity commands.
for wheel in self.wheels.values():
wheel.anglevelocity()
def calculate_radius_min_max(self):
"""
Once the wheel configuraton has been loaded, read maximum turning ability
of the wheels and calculate the minimum turning radius. Also look at the
radius when the wheels are turned a single degree and use that as maximum
turning radius.
Initial values are established by first finding the wheel with the
greatest X distance from center. Minimum radius is 1% of its distance, and
maximum is 10 times (1000%) of the distance.
"""
wheel_x_max = 0
for wheel in self.wheels.values():
if abs(wheel.x) > wheel_x_max:
wheel_x_max = abs(wheel.x)
if wheel_x_max > 0:
limit_min = wheel_x_max * 0.01
limit_max = wheel_x_max * 10
# Initial values established, now let's look at each wheel and calculate
# its relative min/max and compare against initial values.
for wheel in self.wheels.values():
if wheel.steeringcontrol:
angle_max = wheel.steeringcontrol.maxangle(wheel.steeringparam)
if angle_max < 90:
limit_radius = wheel.x + (wheel.y/math.tan(math.radians(angle_max)))
if limit_radius > limit_min:
limit_min = limit_radius
# If the rover uses steering mechanism that can be more precise than
# +/- one degree, decrease the value accordingly.
limit_radius = wheel.x + (wheel.y/math.tan(math.radians(1)))
if abs(limit_radius) < limit_max:
limit_max = abs(limit_radius)
self.minRadius = limit_min
self.maxRadius = limit_max