void motor_set_PWM(int left, int right) { //pwm_clock_init(); if(left==0){ pwm_duty(left_forward,left); pwm_duty(left_back,left); } else if (left > 0) { pwm_duty(left_forward,left); pwm_duty(left_back,0); } else { pwm_duty(left_forward,0); pwm_duty(left_back,-left); } if(right==0){ pwm_duty(right_forward,right); pwm_duty(right_back,right); } else if (right > 0) { pwm_duty(right_back,0); pwm_duty(right_forward,right); } else { pwm_duty(right_forward,0); pwm_duty(right_back,-right); } } 这是一段设置pwm占空比来调整小车转速的代码，请告诉我如何更好地避免小车前进的同时轮子后退，导致小车轮子不转

为了避免小车前进时轮子后退，你可以在设置 PWM 占空比之前添加一些逻辑判断。下面是一个修改后的代码示例：

void motor_set_PWM(int left, int right) {
    // 判断左轮方向
    if(left == 0){
        pwm_duty(left_forward, left);
        pwm_duty(left_back, left);
    }
    else if(left > 0){
        pwm_duty(left_forward, left);
        pwm_duty(left_back, 0);
    }
    else{
        pwm_duty(left_forward, 0);
        pwm_duty(left_back, -left);
    }

    // 判断右轮方向
    if(right == 0){
        pwm_duty(right_forward, right);
        pwm_duty(right_back, right);
    }
    else if(right > 0){
        pwm_duty(right_forward, right);
        pwm_duty(right_back, 0);
    }
    else{
        pwm_duty(right_forward, 0);
        pwm_duty(right_back, -right);
    }

    // 额外判断，如果左右轮方向相反，则将左右轮占空比都设为0
    if((left > 0 && right < 0) || (left < 0 && right > 0)){
        pwm_duty(left_forward, 0);
        pwm_duty(left_back, 0);
        pwm_duty(right_forward, 0);
        pwm_duty(right_back, 0);
    }
}

这样，当左右轮方向相反时，会将左右轮的占空比都设置为0，从而避免小车前进时轮子后退的情况发生。