在直流减速电机控制中,最常用的方法就是通过PWM来控制直流电机的转速。在控制小车走直线的过程中,需要两者的转速一置(如果要走得很直,还需要在短时间内保证两者的行程大致相当,这可以用PID算法来控制)。 因此,在检测到两者转速不一样时,需要动态调整其中一个或两个轮子的PWM的点空比(简单点的就以一个轮为基准,调整另外一个轮子即可;如果以一个固定的标准的话,需要调整两个轮子的PWM占空比)。
程序第一步:设置GPIO,略(输出PWM的管脚用Mode_AF_PP即可)
程序第二步:设置定时器,(保证产生两路PWM即可,我用的是TIM4)
void TIM4_Configuration(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
//时间基初始化
TIM_TimeBaseInitStructure.TIM_Period=144; //18K/144=125Hz,这个是电机PWM的频率
TIM_TimeBaseInitStructure.TIM_Prescaler=4000; //72000000/4000=18K
TIM_TimeBaseInitStructure.TIM_ClockDivision=TIM_CKD_DIV1;
TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInitStructure.TIM_RepetitionCounter=0x0000;
TIM_TimeBaseInit(TIM4,&TIM_TimeBaseInitStructure);
//输出比较模式设置,用于4路PWM输出
TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM2; //输出PWM
TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable; //使能正向通道
TIM_OCInitStructure.TIM_OutputNState=TIM_OutputState_Disable; //失能反向通道
TIM_OCInitStructure.TIM_Pulse=PWM_L; //左轮DIR的占空比
TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_Low; //输出极性为低电平
TIM_OCInitStructure.TIM_OCNPolarity=TIM_OCPolarity_High;//互补输出极性为高电平
TIM_OCInitStructure.TIM_OCIdleState=TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState=TIM_OCNIdleState_Reset;
TIM_OC1Init(TIM4,&TIM_OCInitStructure); //PWM_L初始化
TIM_OC1PreloadConfig(TIM4,TIM_OCPreload_Disable); //改变点空比后,立即产生效应
TIM_OCInitStructure.TIM_Pulse=PWM_R; //左轮PWM的占空比
TIM_OC2Init(TIM4,&TIM_OCInitStructure); //PWM_R初始化
TIM_OC2PreloadConfig(TIM4,TIM_OCPreload_Disable); //改变点空比后,立即产生效应
//使能定时器4
TIM_Cmd(TIM4,ENABLE);
TIM_CtrlPWMOutputs(TIM4,ENABLE);
程序第三步:
在SysTick中断中,读取两个轮子的速度(具体的方法是:每0.1秒读一次,并以此人作为速度的依据),并比较,如果以右轮为基准,则调整左轮的PWM占空比。涉及到关键语句是:TIM_SetCompare1();
u16 COUN1=0;
u16 COUN2=0;
volatile u16 Dist_L=0; //左轮行程脉冲数
volatile u16 Dist_R=0; //右轮行程脉冲数
void SysTick_Handler(void)
{
COUN1=TIM1->CNT; //左轮在0.1秒里脉冲数
COUN2=TIM2->CNT; //右轮在0.1秒里脉冲数
Dist_L=Dist_L+COUN1; //左轮行程脉冲数
Dist_R=Dist_R+COUN2; //右轮行程脉冲数
if( (COUN1-COUN2)>2)
{
PWM_L= TIM_GetCapture1(TIM4);
TIM_SetCompare1(TIM4, PWM_L - 4);
}
else if ( (COUN2-COUN1)>2)
{
PWM_L= TIM_GetCapture1(TIM4);
TIM_SetCompare1(TIM4, PWM_L + 4);
}
TIM_SetCounter(TIM1, 0);
TIM_SetCounter(TIM2, 0);
}
关于TIM_SetCompareX(;)这个函数,还是有很多用途的,其中另外一个用途,就是用于产生不同频率的PWM,具体程序如下:
u16 capture = 0;
extern vu16 CCR1_Val;
extern vu16 CCR2_Val;
extern vu16 CCR3_Val;
extern vu16 CCR4_Val;
void TIM2_IRQHandler(void)
{
/* TIM2_CH1 toggling with frequency = 183.1 Hz */
if (TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_CC1 );
capture = TIM_GetCapture1(TIM2);
TIM_SetCompare1(TIM2, capture + CCR1_Val );
}
/* TIM2_CH2 toggling with frequency = 366.2 Hz */
if (TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);
capture = TIM_GetCapture2(TIM2);
TIM_SetCompare2(TIM2, capture + CCR2_Val);
}
/* TIM2_CH3 toggling with frequency = 732.4 Hz */
if (TIM_GetITStatus(TIM2, TIM_IT_CC3) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_CC3);
capture = TIM_GetCapture3(TIM2);
TIM_SetCompare3(TIM2, capture + CCR3_Val);
}
/* TIM2_CH4 toggling with frequency = 1464.8 Hz */
if (TIM_GetITStatus(TIM2, TIM_IT_CC4) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_CC4);
capture = TIM_GetCapture4(TIM2);
TIM_SetCompare4(TIM2, capture + CCR4_Val);
}
}
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