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）。
1 程序第一步：设置GPIO，略（输出PWM的管脚用Mode_AF_PP即可） 2 3 程序第二步：设置定时器，（保证产生两路PWM即可，我用的是TIM4） 4 5 void TIM4_Configuration(void) 6 { 7 TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure; 8 TIM_OCInitTypeDef TIM_OCInitStructure; 9 10 //时间基初始化 11 TIM_TimeBaseInitStructure.TIM_Period=144; //18K/144=125Hz,这个是电机PWM的频率 12 TIM_TimeBaseInitStructure.TIM_Prescaler=4000; //72000000/4000=18K 13 TIM_TimeBaseInitStructure.TIM_ClockDivision=TIM_CKD_DIV1; 14 TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up; 15 TIM_TimeBaseInitStructure.TIM_RepetitionCounter=0x0000; 16 17 TIM_TimeBaseInit(TIM4,&TIM_TimeBaseInitStructure); 18 19 //输出比较模式设置,用于4路PWM输出 20 TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM2; //输出PWM 21 TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable; //使能正向通道 22 TIM_OCInitStructure.TIM_OutputNState=TIM_OutputState_Disable; //失能反向通道 23 TIM_OCInitStructure.TIM_Pulse=PWM_L; //左轮DIR的占空比 24 TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_Low; //输出极性为低电平 25 TIM_OCInitStructure.TIM_OCNPolarity=TIM_OCPolarity_High;//互补输出极性为高电平 26 TIM_OCInitStructure.TIM_OCIdleState=TIM_OCIdleState_Set; 27 TIM_OCInitStructure.TIM_OCNIdleState=TIM_OCNIdleState_Reset; 28 29 TIM_OC1Init(TIM4,&TIM_OCInitStructure); //PWM_L初始化 30 TIM_OC1PreloadConfig(TIM4,TIM_OCPreload_Disable); //改变点空比后,立即产生效应 31 32 TIM_OCInitStructure.TIM_Pulse=PWM_R; //左轮PWM的占空比 33 TIM_OC2Init(TIM4,&TIM_OCInitStructure); //PWM_R初始化 34 TIM_OC2PreloadConfig(TIM4,TIM_OCPreload_Disable); //改变点空比后,立即产生效应 35 36 //使能定时器4 37 TIM_Cmd(TIM4,ENABLE); 38 TIM_CtrlPWMOutputs(TIM4,ENABLE);
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);
1 程序第三步： 2 3 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（）； 4 5 u16 COUN1=0; 6 u16 COUN2=0; 7 8 volatile u16 Dist_L=0; //左轮行程脉冲数 9 volatile u16 Dist_R=0; //右轮行程脉冲数 10 void SysTick_Handler(void) 11 { 12 13 COUN1=TIM1->CNT; //左轮在0.1秒里脉冲数 14 COUN2=TIM2->CNT; //右轮在0.1秒里脉冲数 15 Dist_L=Dist_L+COUN1; //左轮行程脉冲数 16 Dist_R=Dist_R+COUN2; //右轮行程脉冲数 17 if( (COUN1-COUN2)>2) 18 { 19 PWM_L= TIM_GetCapture1(TIM4); 20 TIM_SetCompare1(TIM4, PWM_L - 4); 21 } 22 else if ( (COUN2-COUN1)>2) 23 { 24 PWM_L= TIM_GetCapture1(TIM4); 25 TIM_SetCompare1(TIM4, PWM_L + 4); 26 } 27 28 TIM_SetCounter(TIM1, 0); 29 TIM_SetCounter(TIM2, 0); 30 31 } 32 33 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： 34 35 u16 capture = 0; 36 37 extern vu16 CCR1_Val; 38 extern vu16 CCR2_Val; 39 extern vu16 CCR3_Val; 40 extern vu16 CCR4_Val; 41 42 void TIM2_IRQHandler(void) 43 { 44 45 /* TIM2_CH1 toggling with frequency = 183.1 Hz */ 46 if (TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET) 47 { 48 TIM_ClearITPendingBit(TIM2, TIM_IT_CC1 ); 49 capture = TIM_GetCapture1(TIM2); 50 TIM_SetCompare1(TIM2, capture + CCR1_Val ); 51 } 52 53 /* TIM2_CH2 toggling with frequency = 366.2 Hz */ 54 if (TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET) 55 { 56 TIM_ClearITPendingBit(TIM2, TIM_IT_CC2); 57 capture = TIM_GetCapture2(TIM2); 58 TIM_SetCompare2(TIM2, capture + CCR2_Val); 59 } 60 61 /* TIM2_CH3 toggling with frequency = 732.4 Hz */ 62 if (TIM_GetITStatus(TIM2, TIM_IT_CC3) != RESET) 63 { 64 TIM_ClearITPendingBit(TIM2, TIM_IT_CC3); 65 capture = TIM_GetCapture3(TIM2); 66 TIM_SetCompare3(TIM2, capture + CCR3_Val); 67 } 68 69 /* TIM2_CH4 toggling with frequency = 1464.8 Hz */ 70 if (TIM_GetITStatus(TIM2, TIM_IT_CC4) != RESET) 71 { 72 TIM_ClearITPendingBit(TIM2, TIM_IT_CC4); 73 capture = TIM_GetCapture4(TIM2); 74 TIM_SetCompare4(TIM2, capture + CCR4_Val); 75 } 76 77 }
