在直流減速電機控制中，最常用的方法就是通過PWM來控制直流電機的轉速。在控制小車走直線的過程中，需要兩者的轉速一置（如果要走得很直，還需要在短時間內保證兩者的行程大致相當，這可以用PID算法來控制）。 因此，在檢測到兩者轉速不一樣時，需要動態調整其中一個或兩個輪子的PWM的點空比（簡單點的就以一個輪為基准，調整另外一個輪子即可；如果以一個固定的標准的話，需要調整兩個輪子的PWM占空比）。
1 程序第一步：設置GPIO，略（輸出PWM的管腳用Mode_AF_PP即可） 2 3 程序第二步：設置定時器，（保證產生兩路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 //時間基初始化 11 TIM_TimeBaseInitStructure.TIM_Period=144; //18K/144=125Hz,這個是電機PWM的頻率 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 //輸出比較模式設置,用於4路PWM輸出 20 TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM2; //輸出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; //左輪DIR的占空比 24 TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_Low; //輸出極性為低電平 25 TIM_OCInitStructure.TIM_OCNPolarity=TIM_OCPolarity_High;//互補輸出極性為高電平 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); //改變點空比后,立即產生效應 31 32 TIM_OCInitStructure.TIM_Pulse=PWM_R; //左輪PWM的占空比 33 TIM_OC2Init(TIM4,&TIM_OCInitStructure); //PWM_R初始化 34 TIM_OC2PreloadConfig(TIM4,TIM_OCPreload_Disable); //改變點空比后,立即產生效應 35 36 //使能定時器4 37 TIM_Cmd(TIM4,ENABLE); 38 TIM_CtrlPWMOutputs(TIM4,ENABLE);
程序第一步：設置GPIO，略（輸出PWM的管腳用Mode_AF_PP即可） 程序第二步：設置定時器，（保證產生兩路PWM即可，我用的是TIM4） void TIM4_Configuration(void) { TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure; TIM_OCInitTypeDef TIM_OCInitStructure; //時間基初始化 TIM_TimeBaseInitStructure.TIM_Period=144; //18K/144=125Hz,這個是電機PWM的頻率 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); //輸出比較模式設置,用於4路PWM輸出 TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM2; //輸出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; //左輪DIR的占空比 TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_Low; //輸出極性為低電平 TIM_OCInitStructure.TIM_OCNPolarity=TIM_OCPolarity_High;//互補輸出極性為高電平 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); //改變點空比后,立即產生效應 TIM_OCInitStructure.TIM_Pulse=PWM_R; //左輪PWM的占空比 TIM_OC2Init(TIM4,&TIM_OCInitStructure); //PWM_R初始化 TIM_OC2PreloadConfig(TIM4,TIM_OCPreload_Disable); //改變點空比后,立即產生效應 //使能定時器4 TIM_Cmd(TIM4,ENABLE); TIM_CtrlPWMOutputs(TIM4,ENABLE);
1 程序第三步： 2 3 在SysTick中斷中，讀取兩個輪子的速度（具體的方法是：每0.1秒讀一次，並以此人作為速度的依據），並比較，如果以右輪為基准，則調整左輪的PWM占空比。涉及到關鍵語句是：TIM_SetCompare1（）； 4 5 u16 COUN1=0; 6 u16 COUN2=0; 7 8 volatile u16 Dist_L=0; //左輪行程脈沖數 9 volatile u16 Dist_R=0; //右輪行程脈沖數 10 void SysTick_Handler(void) 11 { 12 13 COUN1=TIM1->CNT; //左輪在0.1秒里脈沖數 14 COUN2=TIM2->CNT; //右輪在0.1秒里脈沖數 15 Dist_L=Dist_L+COUN1; //左輪行程脈沖數 16 Dist_R=Dist_R+COUN2; //右輪行程脈沖數 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 關於TIM_SetCompareX（；）這個函數，還是有很多用途的，其中另外一個用途，就是用於產生不同頻率的PWM，具體程序如下： 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 }
