名称：void pid(float angle, float angle_dot)
功能：PID运算
输入参数：
     float angle     倾斜角度
  float angle_dot 倾斜角速度
输出参数：无
返回值：  无
**************************************************/
void pid(float angle, float angle_dot)
{
  u32 temp;
  u16 sl, sr;   TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
  TIM_OCInitTypeDef  TIM_OCInitStructure;   now_error = set_point - angle;   speed_filter();   speed *= 0.7;
  speed += speed_out * 0.3;
  position += speed;
  position -= speed_need;
 
  if(position < -60000)
  {
    position = -60000;
  }
  else if(position > 60000)
  {
    position =  60000;
  }
 
  rout = proportion * now_error + derivative * angle_dot - position * integral2 - derivative2 * speed;
 
  speed_l = -rout + turn_need_l;
  speed_r = -rout + turn_need_r;
 
  if(speed_l > MAX_SPEED) 
  {
    speed_l = MAX_SPEED; 
  }
  else if(speed_l < -MAX_SPEED) 
  {
 speed_l = -MAX_SPEED;
  }   if(speed_r > MAX_SPEED) 
  {
    speed_r = MAX_SPEED; 
  }
  else if(speed_r < -MAX_SPEED) 
  {
 speed_r = -MAX_SPEED;
  }
 
  if(speed_l > 0)
  {
    GPIO_ResetBits(GPIOB, GPIO_Pin_8);  //left fr
 sl = speed_l;
  }
  else 
  {
    GPIO_SetBits(GPIOB, GPIO_Pin_8);
 sl = speed_l * (-1);
  }   if(speed_r > 0)
  {
    GPIO_SetBits(GPIOA, GPIO_Pin_3);  //right fr
 sr = speed_r;
  }
  else 
  {
    GPIO_ResetBits(GPIOA, GPIO_Pin_3);
 sr = speed_r * (-1);
  }
 
  temp = 1000000 / sl;
  if(temp > 65535)
  {
    sl = 65535;
  }
  else
  {
    sl = (u16)temp;
  }
   
  temp = 1000000 / sr;
  if(temp > 65535)
  {
    sr = 65535;
  }
  else
  {
    sr = (u16)temp;
  }    /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = sl - 1;  // (Period + 1) * (Prescaler + 1) / 72M = 1ms 
  TIM_TimeBaseStructure.TIM_Prescaler = 30 - 1; 
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;    TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);   TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_Pulse = sl >> 1;   TIM_OC4Init(TIM4, &TIM_OCInitStructure);  //PB9  left   /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = sr - 1;   
  TIM_TimeBaseStructure.TIM_Prescaler = 30  - 1; 
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);   TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_Pulse = sr >> 1;   TIM_OC3Init(TIM2, &TIM_OCInitStructure);  //PA2 right 
}