Arduino PID Library
by Brett Beauregard，contact: br3ttb@gmail.com
What Is PID? PID是什么
From Wikipedia: "A PID controller calculates an 'error' value as the difference between a measured [Input] and a desired setpoint. The controller attempts to minimize the error by adjusting [an Output]."
So, you tell the PID what to measure (the "Input",) Where you want that measurement to be (the "Setpoint",) and the variable to adjust that can make that happen (the "Output".) The PID then adjusts the output trying to make the input equal the setpoint.
For reference, in a car, the Input, Setpoint, and Output would be the speed, desired speed, and gas pedal（踏板） angle respectively.
Functions
Description 建立一个PID控制器
Creates a PID controller linked to the specified Input, Output, and Setpoint. The PID algorithm is in parallel form.
Syntax
PID(&Input, &Output, &Setpoint, Kp, Ki, Kd, Direction)
PID(&Input, &Output, &Setpoint, Kp, Ki, Kd, POn, Direction)
Parameters：
Input: The variable we're trying to control (double)
Output: The variable that will be adjusted by the pid (double)
Setpoint: The value we want to Input to maintain (double)
Kp, Ki, Kd: Tuning Parameters. these affect how the pid will chage the output. (double>=0)
Direction: Either DIRECT or REVERSE. determines which direction the output will move when faced with a given error. DIRECT is most common.
POn: Either P_ON_E (Default) or P_ON_M. Allows Proportional on Measurement to be specified.
Returns：None
Description 在loop()中做PID运算
Contains the pid algorithm. it should be called once every loop(). Most of the time it will just return without doing anything. At a frequency specified by SetSampleTime it will calculate a new Output.
Syntax：
Compute()
Parameters：None
Returns：
True: when the output is computed
False: when nothing has been done
Description 工作模式设定（自动/手动）
Specifies whether the PID should be on (Automatic) or off (Manual.) The PID defaults to the off position when created.
Syntax：
SetMode(mode)
Parameters：
mode: AUTOMATIC or MANUAL
Returns：None
Description：输出限幅
The PID controller is designed to vary its output within a given range. By default this range is 0-255: the arduino PWM range. There's no use sending 300, 400, or 500 to the PWM. Depending on the application though, a different range may be desired.
Syntax：
SetOutputLimits(min, max)
Parameters：
min: Low end of the range. must be < max (double)
max: High end of the range. must be > min (double)
Returns：None
Description：PID参数实时调整
Tuning parameters (or "Tunings") dictate（决定） the dynamic behavior of the PID. Will it oscillate or not? Will it be fast or slow? An initial set of Tunings is specified when the PID is created. For most users this will be enough. There are times however, tunings need to be changed during run-time. At those times this function can be called.
Syntax：
SetTunings(Kp, Ki, Kd)
SetTunings(Kp, Ki, Kd, POn)
Parameters：
Kp: Determines how aggressively the PID reacts to the current amount of error (Proportional) (double >=0)
Ki: Determines how aggressively the PID reacts to error over time (Integral) (double>=0)
Kd: Determines how aggressively the PID reacts to the change in error (Derivative) (double>=0)
POn: Either P_ON_E (Default) or P_ON_M. Allows Proportional on Measurement to be specified.
Returns：None
Decription：采样时间设定（毫秒）
Determines how often the PID algorithm evaluates. The default is 200mS. For robotics applications this may need to be faster, but for the most part 200mS is plenty fast.
Syntax：
SetSampleTime(SampleTime)
Parameters：
SampleTime: How often, in milliseconds, the PID will be evaluated. (int>0)
Returns：None
Description： 控制方向设定（正作用/逆作用）
If my Input is above Setpoint, should the output be increased or decreased? Depending on what the PID is connected to, either could be true. With a car, the output should be decreased to bring the speed down. For a refrigerator, the opposite is true. The output (cooling) needs to be increased to bring my temperature down.
This function specifies which type of process the PID is connected to. This information is also specified when the PID constructed. Since it's unlikely that the process will switch from direct to reverse, it's equally unlikely that anyone will actually use this function.
Syntax：
SetControllerDirection(Direction);
Parameters：
Direction：DIRECT (like a car，输出减弱) or REVERSE (like a refrigerator，输出增强)
Returns：None
Decription：PID 参数询问显示
These functions query（询问） the PID internals to get current values. These are useful for display purposes.
GetKp()
GetKi()
GetKd()
GetMode()
GetDirection()
Syntax：
GetKp()
GetKi()
GetKd()
GetMode()
GetDirection()
Parameters：None
Returns：The corresponding internal value
Examples PID控制举例
Basic 模拟量输入控制模拟量输出
1 /******************************************************** 2 * PID Basic Example 3 * Reading analog input 0 to control analog PWM output 3 4 ********************************************************/ 5 #include <PID_v1.h> 6 //Define Variables we'll be connecting to double Setpoint, Input, Output; 7 //Specify the links and initial tuning parameters 8 PID myPID(&Input, &Output, &Setpoint,2,5,1, DIRECT); 9 10 void setup() 11 { 12 Input = analogRead(0); //initialize the variables we're linked to 13 Setpoint = 100; 14 myPID.SetMode(AUTOMATIC); //turn the PID on 15 } 16 17 void loop() 18 { 19 Input = analogRead(0); 20 myPID.Compute(); 21 analogWrite(3,Output); 22 }
AdaptiveTunings 自动调整PID参数
1 /******************************************************** 2 * PID Adaptive Tuning Example 3 * One of the benefits of the PID library is that you can 4 * change the tuning parameters at any time. this can be 5 * helpful if we want the controller to be aggressive（进取的） at some 6 * times, and conservative（保守的） at others. in the example below 7 * we set the controller to use Conservative Tuning Parameters 8 * when we're near setpoint and more aggressive Tuning 9 * Parameters when we're farther away. 10 ********************************************************/ 11 #include <PID_v1.h> 12 //Define Variables we'll be connecting to double Setpoint, Input, Output; 13 //Define the aggressive and conservative Tuning Parameters 14 double aggKp=4, aggKi=0.2, aggKd=1; 15 double consKp=1, consKi=0.05, consKd=0.25; 16 //Specify the links and initial tuning parameters 17 PID myPID(&Input, &Output, &Setpoint, consKp, consKi, consKd, DIRECT); 18 19 void setup() 20 { 21 Input = analogRead(0); //initialize the variables we're linked to 22 Setpoint = 100; 23 myPID.SetMode(AUTOMATIC); //turn the PID on 24 } 25 26 void loop() 27 { 28 Input = analogRead(0); 29 double gap = abs(Setpoint-Input); //distance away from setpoint 30 if(gap<10) 31 { 32 myPID.SetTunings(consKp, consKi, consKd); 33 //we're close to setpoint, use conservative tuning parameters 34 } 35 Else 36 { 37 myPID.SetTunings(aggKp, aggKi, aggKd); 38 //we're far from setpoint, use aggressive tuning parameters 39 } 40 myPID.Compute(); 41 analogWrite(3,Output); 42 }
