巡线小车程序，在没有检测到线的时候，模块直接停止运行了，怎么避免？？

[bwdv]

pid.py程序
from pyb import millis
from math import pi, isnan

class PID:
_kp = _ki = _kd = _integrator = _imax = 0
_last_error = _last_derivative = _last_t = 0
_RC = 1/(2 * pi * 20)
def init(self, p=0, i=0, d=0, imax=0):
self._kp = float(p)
self._ki = float(i)
self._kd = float(d)
self._imax = abs(imax)
self._last_derivative = float('nan')

def get_pid(self, error, scaler):
    tnow = millis()
    dt = tnow - self._last_t
    output = 0
    if self._last_t == 0 or dt > 1000:
        dt = 0
        self.reset_I()
    self._last_t = tnow
    delta_time = float(dt) / float(1000)
    output += error * self._kp
    if abs(self._kd) > 0 and dt > 0:
        if isnan(self._last_derivative):
            derivative = 0
            self._last_derivative = 0
        else:
            derivative = (error - self._last_error) / delta_time
        derivative = self._last_derivative + \
                                 ((delta_time / (self._RC + delta_time)) * \
                                    (derivative - self._last_derivative))
        self._last_error = error
        self._last_derivative = derivative
        output += self._kd * derivative
    output *= scaler
    if abs(self._ki) > 0 and dt > 0:
        self._integrator += (error * self._ki) * scaler * delta_time
        if self._integrator < -self._imax: self._integrator = -self._imax
        elif self._integrator > self._imax: self._integrator = self._imax
        output += self._integrator
    return output
def reset_I(self):
    self._integrator = 0
    self._last_derivative = float('nan')

main.py程序
THRESHOLD = (60, 80, -10, 10, -10, 20) # Grayscale threshold for dark things...
import sensor, image, time
from pyb import LED
from pid import PID
rho_pid = PID(p=0.4, i=0)
theta_pid = PID(p=0.001, i=0)

sensor.reset()
sensor.set_vflip(True)
sensor.set_hmirror(True)
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QQQVGA) # 80x60 (4,800 pixels) - O(N^2) max = 2,3040,000.
#sensor.set_windowing([0,20,80,40])
sensor.skip_frames(time = 2000) # WARNING: If you use QQVGA it may take seconds
clock = time.clock() # to process a frame sometimes.

while(True):
clock.tick()
img = sensor.snapshot().binary([THRESHOLD])
line = img.get_regression([(100,100,0,0,0,0)], robust = True)
if (line):
rho_err = abs(line.rho())-img.width()/2
if line.theta()>90:
theta_err = line.theta()-180
else:
theta_err = line.theta()
img.draw_line(line.line(), color = 127)
print(rho_err,line.magnitude(),rho_err)

[kidswong999]

逻辑有问题，最后那里，应该加缩进

[bwdv]

好的，谢谢大神帮忙！！！！