PID debugging of coding motor (speed loop | position loop | follow)

In the previous article, we talked about the coding motor cascade PID Relevant knowledge , As well as some PID Debugging experience , Here, I happened to touch the motor again recently , At the same time, the tool of waveform is added , I think this way can help more people understand this process , At the same time, we can better understand PID This thing .

At the same time, during the school recruitment interview , Some embedded posts do robot control related , Including when I introduce my project, I usually ask some PID Debugging process of ,PID The role of several parameters , Description of inner ring and outer ring, etc , therefore PID It's more important .

If you have any comments on this article, you are welcome to put forward ！

1、 Recognition of coding motor

The content of data reading of coded motor has been introduced in the previous article , The corresponding links are as follows , If necessary, you can understand by yourself ：
Double closed loop control of DC coded motor （ Speed + angle ） control

There is no repetition here , Here we can add some contents , Mainly the data processing part of the encoder , This is to better obtain the angle data , Steps are as follows ：

First, we need to turn on the corresponding interrupt , Data accumulation in interrupt , In this way, you can make some records, such as angle and number of turns

Here, let's review the encoder harness , The harness here is the number of pulses per revolution of the motor , But we are AB Then there are captures that can be on the upper and lower edges , So we can do it 4 Frequency doubling sampling

The final number of turns is designed as follows , The first thing here is to design a positive and negative , If it's positive, add it up , The direction is subtracted , Then the final lap count here is the same .

In this way, we can intuitively show the record of the number of laps , Source code is as follows ：

int Angle = 0;// angle 
int circr = 0;// Number of turns 

const int Step_Angle = 360/4/30;	

void Motor_Get_Angle(TIM_HandleTypeDef *htim)	
{
    
	if(htim == &htim2)
	{
    
		if((htim->Instance->CR1 & 0x0010)>>4)// Direction judgment 
			//  It can also be used here htim->Instance->CR1 To judge  0X01 Better ahead of time ,0X11 It's counter clockwise 
			Angle -= Step_Angle;
		else
			Angle += Step_Angle;
	}
	if(Angle == 360)
	{
    
		circr++;
		Angle = 0;
	}
	if(Angle == -360)
	{
    
		circr--;
		Angle = 0;
	}
}

2、 Upper computer waveform display

1、 Function is introduced

Here is the recommended VOFA+ This serial assistant , With waveform display function , More powerful , About VOFA+ I won't explain this here , There are a lot of information on the Internet , Basically, Baidu can see a lot of relevant information as soon as it searches

If you want to use his blog display function here, you should follow my following operations

After pulling out the waveform function, we need to fill in here for full screen display , As shown below

Select the type of graph and the waveform

Generally we x Just set the axis directly to time

y The axis can be used to set our curve , Note here , There has to be , If the data hasn't been sent, you can't see it

Then we automatically zoom under selection

2、 Agreement that

Enter our agreement and connection first ：

You can see the protocol description as follows ：

Here you can see the description of the agreement , As shown below ：

Another explanation

Mainly the debugging instructions here , Here you can see the first direct use printf That's all right. , But both give examples , So I decided to use the first method to realize , Use printf add , It can be realized .

3、 Speed loop adjustment test certificate

Here I still build the same as the previous article PID framework , See Double closed loop control of DC coded motor （ Speed + angle ） control

About PID Debugging effect of , You can see my article , This article uses simulink To simulate the PID：Matlab Use simulink Set up PID Record

The speed loop used PID As shown below , You can see that the parameters printed are the target value and the current value ：

Here, let's take a look at pure p When adjusting , here KP=200, It's quite big , There are still steady-state errors

Then add I Eliminate the error , here I Just gave 0.1

We simply continue to grow KP, You can see the obvious overshoot

At this time, if one person increases i You can see that the stability of the system decreases

Finally, we can see the debugging effect , As shown below ：

4、 Position ring adjustment test certificate

Here, the position ring controls the position of the motor , The direct way to think of here must be to use it directly PID Calculation , It's perfectly possible , It's just not very stable , The effect is not very good , Anti disturbance is not very good , Therefore, you can choose cascade PID To realize the relevant functions , As follows, I introduce both schemes ：

The following is the direct use location PID Calculate P[ID The situation of
、
Here's how to use speed and position PID The situation of calculation

This process feels like following the parameter adjustment scheme I mentioned above , It's still convenient , It can be debugged quickly , The final effect is as follows ：

5、 Achieve the following effect

Following is actually a PID Linkage with another , The essential situation is to put one of the rings PID The input quantity is replaced by the data collected by the sensor of another motor , But the final control quantity is another motor .

The final effect is as follows ：