一、原理圖以及簡介
電機如下:
通常電機需要正反轉會需要一個電機驅動板,電機接到電機接口。
電機驅動板如下:
電機狀態表如下:
不同的電機驅動板可能會有略微不同,有的IN1,IN2之外可能還會有ENA輸入信號去PWM脈衝信號來調速度,這個電機驅動板就沒有,就通過直接給IN1,IN2引腳PWM信號,比如左輪正轉,IN1輸入PWM的佔空比一直爲0,IN1和IN2同時爲0就不轉,IN2輸入不同佔空比去調速,關於調速下面也會說到。
STM32板子連接電機驅動板,STM32F103C8T對應電機的引腳圖:
PWM波形如下:
佔空比:
D = t1/T ;
電機的平均轉速爲:
Va = Vmax*D ;
其中Va指的是電機的平均速度,Vmax是指電機在全通電時最大速度,D指的是佔空比。由上面的公式可見,當改變佔空比D時,就可以得到不同電機平均速度Va,從而達到調速的目的。
二、代碼
初始化電機PWM定時器,初始化定時器3和定時器4作爲PWM控制電機,239的預分頻,1000的自動重裝載值,主時鐘是72M,定時器時鐘CK_CNT=72,000,000/(239+1),定時器時鐘是300,000HZ,1/300000≈3.3us計數一次,計數達到1000次,產生一次中斷重新從0開始計數
//初始化電機PWM定時
void setup_car_pwm(void) {
//小車 pwm 初始化
TIM3_Pwm_Init(1000, 239);
TIM4_Pwm_Init(1000, 239);
car_pwm_set(0,0); //設置小車的左右輪速度爲0
}
引腳配置如下圖:
初始化定時器3的PWM模式,PB0配置成定時器3的PWM模式通道3,PB1配置成定時器3的PWM模式的通道4
void TIM3_Pwm_Init(u16 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1; //對應CH3通道PB0
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);
TIM_TimeBaseStructure.TIM_Period = arr;
TIM_TimeBaseStructure.TIM_Prescaler =psc;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &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=500;
TIM_OC3Init(TIM3, &TIM_OCInitStructure);
TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_OC4Init(TIM3, &TIM_OCInitStructure);
TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_Cmd(TIM3, ENABLE);
}
初始化定時器4的PWM模式,PB8配置成定時器4的PWM模式通道3,PB9配置成定時器4的PWM模式的通道4
void TIM4_Pwm_Init(u16 arr,u16 psc) {
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9; //對應CH3通道PB0
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);
TIM_TimeBaseStructure.TIM_Period = arr;
TIM_TimeBaseStructure.TIM_Prescaler =psc;
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=500;
TIM_OC3Init(TIM4, &TIM_OCInitStructure);
TIM_OC3PreloadConfig(TIM4, TIM_OCPreload_Enable);
TIM_OC4Init(TIM4, &TIM_OCInitStructure);
TIM_OC4PreloadConfig(TIM4, TIM_OCPreload_Enable);
TIM_Cmd(TIM4, ENABLE);
}
小車PWM調速,右輪對應的是IN3、IN4控制,也就是PB8、PB9對應的定時器4的通道3和通道4。左輪對應是IN1、IN2控制,對應PB0、PB1定時器3的通道3和通道4。前進就兩個輪子左輪正轉右輪正轉,設置相同的1~1000範圍的CRR調佔空比調節速度。退後就是相反的。
//小車控制函數
//參數 左輪速度和右輪速度 範圍 -1000 到 1000
void car_pwm_set(int car_left, int car_right) {
static int car_left_bak, car_right_bak;
if(car_left >= CYCLE)car_left = CYCLE-1;
else if(car_left <= -CYCLE)car_left = -CYCLE+1;
else if(car_left == 0)car_left = 1;
if(car_right >= CYCLE)car_right = CYCLE-1;
else if(car_right <= -CYCLE)car_right = -CYCLE+1;
else if(car_right == 0)car_right = 1;
car_left = -car_left;
car_right = -car_right;
car_left = car_left/car_dw;
car_right = car_right/car_dw;
if(car_right>0) {
TIM_SetCompare4(TIM4,1);
TIM_SetCompare3(TIM4,car_right);
} else if(car_right<0){
TIM_SetCompare4(TIM4,-car_right);
TIM_SetCompare3(TIM4,1);
} else {
TIM_SetCompare4(TIM4,CYCLE - 1);
TIM_SetCompare3(TIM4,CYCLE - 1);//CYCLE=1000
}
if(car_left>0) {
TIM_SetCompare4(TIM3,1);
TIM_SetCompare3(TIM3,car_left);
} else if(car_left<0){
TIM_SetCompare4(TIM3,-car_left);
TIM_SetCompare3(TIM3,1);
} else {
TIM_SetCompare4(TIM3,CYCLE - 1);
TIM_SetCompare3(TIM3,CYCLE - 1);
}
return;
}