twist_controller.py

import rospy
from dbw_mkz_msgs.msg import ThrottleCmd, SteeringCmd, BrakeCmd

from lowpass import LowPassFilter
from pid import PID
from yaw_controller import YawController

GAS_DENSITY = 2.858
ONE_MPH = 0.44704


class Controller(object):
    def __init__(self, vehicle_mass, fuel_capacity, brake_deadband, decel_limit, accel_limit,
                 wheel_radius, wheel_base, steer_ratio, max_lat_accel, max_steer_angle):

        self.yaw_controller = YawController(wheel_base, steer_ratio, 0.1, max_lat_accel, max_steer_angle)

        kp = 0.3
        ki = 0.1
        kd = 0.
        mn = 0.  # Minimum throttle value
        mx = 0.4  # MAximum throttle value
        self.throttle_controller = PID(kp, ki, kd, mn, mx)

        tau = 0.5  # 1/(2pi * tau) = cutoff frequency
        ts = 0.02  # sample time
        self.vel_lpf = LowPassFilter(tau, ts)

        self.vehicle_mass = vehicle_mass
        self.fuel_capacity = fuel_capacity
        self.brake_deadband = brake_deadband
        self.decel_limit = decel_limit
        self.accel_limit = accel_limit
        self.wheel_radius = wheel_radius

        self.last_time = rospy.get_time()

    def control(self, current_vel, dbw_enabled, linear_vel, angular_vel):
        """
        :return: throttle, brake, steer
        """

        if not dbw_enabled:
            self.throttle_controller.reset()
            return 0., 0., 0.

        current_vel = self.vel_lpf.filt(current_vel)

        # rospy.logwarn("Angular vel: {0}".format(angular_vel))
        # rospy.logwarn("Target velocity: {0}".format(linear_vel))
        # rospy.logwarn("Target Angular velocity: {0}\n".format(angular_vel))
        # rospy.logwarn("Current velocity: {0}".format(current_vel))
        # rospy.logwarn("Filtered velocity: {0}".format(self.vel_lpf.get()))

        steering = self.yaw_controller.get_steering(linear_vel, angular_vel, current_vel)

        vel_error = linear_vel - current_vel
        self.last_vel = current_vel

        current_time = rospy.get_time()
        sample_time = current_time - self.last_time
        self.last_time = current_time

        throttle = self.throttle_controller.step(vel_error, sample_time)
        brake = 0.0

        if linear_vel == 0. and current_vel < 0.1:
            throttle = 0.0
            brake = 700  # (400 is too small?) N * m  - to hold the car in place if we are stopped at a light. Acceleration - 1m/s^2

        elif throttle < .1 and vel_error < 0:
            throttle = 0
            decel = max(vel_error, self.decel_limit)
            brake = abs(decel) * self.vehicle_mass * self.wheel_radius  # Torque N*m

        return throttle, brake, steering