将上述代码结合四轮小车和pwm进行改写

下面是将之前的代码结合四轮小车和PWM进行改写的示例代码：

import RPi.GPIO as GPIO
import time

# 设置引脚
pin_left_front = 11
pin_left_back = 12
pin_right_front = 13
pin_right_back = 15

# 设置PID参数
kp = 0.5  # 比例系数
ki = 0.1  # 积分系数
kd = 0.2  # 微分系数

# 初始化GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(pin_left_front, GPIO.OUT)
GPIO.setup(pin_left_back, GPIO.OUT)
GPIO.setup(pin_right_front, GPIO.OUT)
GPIO.setup(pin_right_back, GPIO.OUT)

# 初始化PWM
pwm_left_front = GPIO.PWM(pin_left_front, 100)
pwm_left_back = GPIO.PWM(pin_left_back, 100)
pwm_right_front = GPIO.PWM(pin_right_front, 100)
pwm_right_back = GPIO.PWM(pin_right_back, 100)

# 初始化小车控制
def init_car():
    pwm_left_front.start(0)
    pwm_left_back.start(0)
    pwm_right_front.start(0)
    pwm_right_back.start(0)

# 获取灰度传感器数据
def get_sensor_data():
    sensor_data = {
        'left': GPIO.input(pin_left),
        'middle_left': GPIO.input(pin_middle_left),
        'middle': GPIO.input(pin_middle),
        'middle_right': GPIO.input(pin_middle_right),
        'right': GPIO.input(pin_right)
    }
    return sensor_data

# PID控制
def pid_control(sensor_data):
    error = sensor_data['middle'] * 1 + sensor_data['middle_left'] * 0.5 - sensor_data['middle_right'] * 0.5 - sensor_data['left'] * 2 - sensor_data['right'] * (-2)
    output = kp * error
    return output

# 转向控制
def steering_control(output):
    if output > 0:
        # 左转
        pwm_left_front.ChangeDutyCycle(0)
        pwm_left_back.ChangeDutyCycle(abs(output))
        pwm_right_front.ChangeDutyCycle(abs(output))
        pwm_right_back.ChangeDutyCycle(0)
    elif output < 0:
        # 右转
        pwm_left_front.ChangeDutyCycle(abs(output))
        pwm_left_back.ChangeDutyCycle(0)
        pwm_right_front.ChangeDutyCycle(0)
        pwm_right_back.ChangeDutyCycle(abs(output))
    else:
        # 直行
        pwm_left_front.ChangeDutyCycle(0)
        pwm_left_back.ChangeDutyCycle(0)
        pwm_right_front.ChangeDutyCycle(0)
        pwm_right_back.ChangeDutyCycle(0)

# 循迹转弯控制
def track_turn():
    init_car()
    while True:
        sensor_data = get_sensor_data()
        output = pid_control(sensor_data)
        steering_control(output)
        
        time.sleep(0.01)

# 主函数
if __name__ == "__main__":
    try:
        track_turn()
    except KeyboardInterrupt:
        GPIO.cleanup()

请注意，这只是一个示例代码，具体的转弯控制逻辑需要根据你的具体硬件连接和传感器输出进行调整。你需要根据实际情况设置引脚和PWM参数，并编写具体的小车控制逻辑。此外，还需要根据你的控制方式（如具体的PWM调节范围和控制信号）对代码进行相应的修改。