[电机控制专用MCU] 无刷电机控制（三）如何通过HALL传感器获取电机速度

一、霍尔传感器与电机转动的本质关系

1. 3个霍尔元件呈120°电角度分布（下图可看出相位差120°），检测转子磁极位置
2. 电机每旋转60°电角度，霍尔组合状态变化一次
3. 完整电周期（360°电角度）产生6次状态变化

给出了三个传感器的输出和每相的相应反电动势（ BEMF）电压波形。

二、速度计算公式的完整推导

设：

l Δt：两次霍尔变化的时间间隔（秒）

l P：电机极对数（磁极数/2）

l f_m：机械转速（转/秒）

推导过程：

每个Δt对应60°电角度

l 完整电周期(360°)时间：T_e = 6 × Δt

l 机械转速：f_m = 1/(P × T_e) = 1/(P × 6 × Δt)

l RPM（转/分）：RPM = 60 × f_m = 60/(6PΔt) = 10/(PΔt)

三、软件实现

1、定时器初始化，配置为输入捕获模式

void Drv_Hall_Init(u32 arr, u16 psc)
{

  
    TMR_TimeBase_T   TIM_TimeBaseStructure;
    TMR_ICConfig_T   TIM_ICInitStructure;
  
    TMR_Reset(TMR2);
    TMR_ConfigTimeBaseStruct(&TIM_TimeBaseStructure);
  
    /* Sets the value of the automatic reload register Period for the next update event load activity
     * Set the Prescaler value used as the divisor of the TIMx clock frequency
     * Set clock split :TDTS = TIM_CKD_DIV1
     * Up counting mode
     */
    TIM_TimeBaseStructure.period        = arr;
    TIM_TimeBaseStructure.div     = psc;
    TIM_TimeBaseStructure.clockDivision = TMR_CKD_DIV1;
    TIM_TimeBaseStructure.counterMode   = TMR_COUNTER_MODE_UP;
    TIM_TimeBaseStructure.repetitionCounter = 0;
    TMR_ConfigTimeBase(TMR2, &TIM_TimeBaseStructure);

    /**
     * Initialize TIM2 input capture parameters
     * CC1S=01 selects the input terminal IC1 to be mapped to TI1
     * Set to double edge capture
     * Map to TI1
     * Configure input frequency division, no frequency division
     * Configure input filter IC1F to 8
     */
    TIM_ICInitStructure.channel     = TMR_CHANNEL_1;
    TIM_ICInitStructure.ICpolarity  = TMR_IC_POLARITY_BOTHEDGE;
    TIM_ICInitStructure.ICselection = TMR_IC_SELECTION_DIRECT_TI;
    TIM_ICInitStructure.ICprescaler = TMR_ICPSC_DIV1;
    TIM_ICInitStructure.ICfilter    = 0x0f;
    TMR_ICConfig(TMR2, &TIM_ICInitStructure);
  
    /** Enable the Hall sensor interface of TIM2 */
    TMR_EnableHallSensor(TMR2);
  
    /** Input trigger source selection TI1 Edge Detector */
    TMR_SelectInputTrigger(TMR2, TMR_TS_TI1F_ED);
  
    /** Select from mode to reset mode */
    TMR_SelectSlaveMode(TMR2, TMR_SLAVEMODE_RESET);

    TMR_EnableMasterSlaveMode(TMR2);
  
    /** Allow interrupts to be triggered    */
    TMR_EnableInterrupt(TMR2, TMR_INT_UPDATE);
    TMR_EnableInterrupt(TMR2, TMR_INT_CH1);
    TMR_ClearIntFlag(TMR2, TMR_INT_FLAG_UPDATE);
    TMR_ClearIntFlag(TMR2, TMR_INT_FLAG_CH1);
    TMR_ICConfigStructInit(&TIM_ICInitStructure);
  
//    NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
//    NVIC_InitStructure.NVIC_IRQChannelPriority = 1;
//    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
//    NVIC_Init(&NVIC_InitStructure);

    TMR_Enable(TMR2);
}

2、定时器输入捕获中断，获取时间差，计算速度

void TMR2_IRQHandler(void)
{
  static uint8_t i = 0;
  uint8_t j = 0;
  
  if(TMR_ReadIntFlag(TMR2, TMR_INT_FLAG_CH1) != RESET) 
  {
    i++;
    if(i >= 6)
    {
      i = 0;
    }
    /*Hall change time capture*/
    Motor_1st.HALL.HallTime[i] = TMR2->CC1;
    /*Read HALL value*/
    ReadHallValue = HALL_JudgeState();
    Motor_1st.HALL.RunHallValue = ReadHallValue;
  
    Motor_1st.HALL.HallTimeSum = 0;
    for(j=0;j<6;j++)
    {
      Motor_1st.HALL.HallTimeSum += Motor_1st.HALL.HallTime[j];
    }
    /*Motor speed calculation*/
    Motor_1st.HALL.SpeedTemp = SPEEDX/Motor_1st.HALL.HallTimeSum;
  
    if(SpeedFdk.Out >= 200)
    {
      if(Motor_1st.BLDC.RPValue.s16Act < 100)
      {
        PWMH_OFF_PWML_OFF
      }
      else
      {
        MotorDrive(ReadHallValue);
      }
    }
  
    TIMFlag.HallDelay = 0;
  
    TMR_ClearIntFlag(TMR2, TMR_INT_FLAG_CH1); 
  }
  
  if(TMR_ReadIntFlag(TMR2, TMR_INT_FLAG_UPDATE) != RESET)
  {
    TIMFlag.HallDelay++;
    if(TIMFlag.HallDelay >= 10)
    {
      TIMFlag.HallDelay = 0;
      Motor_1st.HALL.SpeedTemp = 0;
      SpeedFdk.Out = 0;
      MovingAvgInit(&SpeedFdk);
    }
    TMR_ClearIntFlag(TMR2,TMR_INT_FLAG_UPDATE); 
  }
}

四、总结

通过定时器输出捕获，获取每次HALL状态时间差，从而计算出电机的速度，只可简单实现电机运行功能。实际应用中任存在一些问题，比如电机霍尔角度安装本身就会存在偏差，导致实际的角度并不是60度电角度；同时电机负载突变也会导致某段时间速度波动大，导致速度估算出现错误。