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- Update tuning methods - Update plotter function - Update documentation, Wiki and examples
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‎README.md‎

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Original file line numberDiff line numberDiff line change
@@ -6,7 +6,12 @@ This is an open loop PID autotuner using a novel s-curve inflection point test m
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This tuning method determines the process gain, dead time, time constant and more by doing a shortened step test that ends just after the [inflection point](http://en.wikipedia.org/wiki/Inflection_point) has been reached. From here, the apparent maximum PV (input) is mathematically determined and the controller's tuning parameters are calculated. Test duration is typically only ½Tau.
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- See [**WiKi**](https://github.com/Dlloydev/sTune/wiki) for test results and more.
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See [**WiKi**](https://github.com/Dlloydev/sTune/wiki) for test results and more:
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- [Get_All_Tunings](https://github.com/Dlloydev/sTune/wiki/Get_All_Tunings)
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- [plotter function reference](https://github.com/Dlloydev/sTune/wiki/plotter-function-reference)
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- [printPidTuner function reference](https://github.com/Dlloydev/sTune/wiki/printPidTuner-function-reference)
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- ***TODO**: digital ON/OFF (relay) temperature control*
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#### Inflection Point Discovery
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@@ -57,7 +62,7 @@ The slope of the tangent line is checked at every sample. When the sign of the c
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pvMax = pvIp + slopeIp * kexp; // where kexp = 4.3004 = (1 / exp(-1)) / (1 - exp(-1))
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```
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- The process gain `Ku` and time constant `Tu` are determined and the selected tuning rule's constants are used to determine `Kp, Ki and Kd`. Also, `controllability` and other details are provided (see comments in `sTune.cpp`).
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- The process gain `Ku` and time constant `Tu` are determined and the selected tuning rule's constants are used to determine `Kp, Ki, Kd, Ti and Td`. Also, `controllability` and other details are provided (see comments in `sTune.cpp`).
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- In the user's sketch, the PID controller is set to automatic, the tuning parameters are applied the PID controller is run.
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### Functions
@@ -71,20 +76,20 @@ sTune(float *input, float *output, TuningRule tuningRule, Action action, SerialM
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- `input` and `output` are pointers to the variables holding these values.
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- `tuningRule` provides selection of 10 various tuning rules as described in the table below.
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- `action` provides choices for controller action (direct or reverse) and whether to perform a fast inflection point test (IP) or a full 5 time constant test (5T). Choices are `directIP`, `direct5T`, `reverseIP` and `reverse5T`.
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- `serialMode` provides 6 choices for serial output as described in the table below.
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| Open Loop Tuning Methods | Description |
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| ------------------------ | ------------------------------------------------------------ |
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| `ZN_PID` | Open loop Ziegler-Nichols method with ¼ decay ratio |
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| `ZN_Half_PID` | Same as `ZN_PID` but with all constants cut in half |
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| `Damped_PID` | Can solve marginal stability issues |
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| `NoOvershoot_PID` | Uses C-H-R method (set point tracking) with 0% overshoot |
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| `CohenCoon_PID` | Open loop method approximates closed loop response with a ¼ decay ratio |
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| `ZN_PI` | Open loop Ziegler-Nichols method with ¼ decay ratio |
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| `ZN_Half_PI` | Same as `ZN_PID` but with all constants cut in half |
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| `Damped_PI` | Can solve marginal stability issues |
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| `NoOvershoot_PI` | Uses C-H-R method (set point tracking) with 0% overshoot |
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| `CohenCoon_PI` | Open loop method approximates closed loop response with a ¼ decay ratio |
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- `serialMode` provides 6 choices for serial output.
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| Open Loop Tuning Methods | Autotune Plot (using PWM output) | Description |
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| ------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ |
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| `ZN_PID` | [![Click to enlarge](https://user-images.githubusercontent.com/63488701/149276354-fcec7626-4f0a-4ce2-a8a2-078745a84dcd.png)](https://user-images.githubusercontent.com/63488701/149275791-a46f353a-3215-486c-a9ce-d96183897272.PNG) | Open Loop Ziegler-Nichols method with ¼ decay ratio |
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| `DampedOsc_PID` | [![Click to enlarge](https://user-images.githubusercontent.com/63488701/149277219-48534317-cf0f-44f0-a5be-12653b2f6e0c.png)](https://user-images.githubusercontent.com/63488701/149275509-68d12ba6-269a-4ce1-b8a7-36037518c49b.PNG) | Damped Oscillation method can solve marginal stability issues |
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| `NoOvershoot_PID` | [![Click to enlarge](https://user-images.githubusercontent.com/63488701/149277649-7bdf4a72-4de6-41b2-9825-628d4d742423.png)](https://user-images.githubusercontent.com/63488701/149275728-4fca57f0-c975-4350-ab45-56d50b7c2cdf.PNG) | No Overshoot uses the C-H-R method (set point tracking) with 0% overshoot |
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| `CohenCoon_PID` | [![Click to enlarge](https://user-images.githubusercontent.com/63488701/149278074-6a01584e-0c9b-44bf-b595-f436f653f220.png)](https://user-images.githubusercontent.com/63488701/149275398-69586823-0267-4834-8183-d383713f2d27.PNG) | Open loop Cohen Coon method approximates closed loop response with a ¼ decay ratio |
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| `Mixed_PID` | [![Click to enlarge](https://user-images.githubusercontent.com/63488701/149278272-5057825c-5d92-4e69-9790-c90fd5235eaf.png)](https://user-images.githubusercontent.com/63488701/149275646-7aa0d8c9-397e-4bc5-8110-85b54a951c4f.PNG) | Mixed method averages the gains for `ZN_PID`, `DampedOsc_PID`, `NoOvershoot_PID` and `CohenCoon_PID` |
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| `ZN_PI` | | Open Loop Ziegler-Nichols method with ¼ decay ratio |
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| `DampedOsc_PI` | | Damped Oscillation method can solve marginal stability issues |
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| `NoOvershoot_PI` | | No Overshoot uses the C-H-R method (set point tracking) with 0% overshoot |
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| `CohenCoon_PI` | | Open loop Cohen Coon method approximates closed loop response with a ¼ decay ratio |
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| `Mixed_PI` | | Mixed method averages the gains for `ZN_PI`, `DampedOsc_PI`, `NoOvershoot_PI` and `CohenCoon_PI` |
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| Serial Mode | Description |
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| --------------- | ------------------------------------------------------------ |
@@ -99,16 +104,16 @@ sTune(float *input, float *output, TuningRule tuningRule, Action action, SerialM
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```c++
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sTune tuner = sTune(&Input, &Output, tuner.ZN_PID, tuner.directIP, tuner.printALL);
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/* ZN_PID directIP serialOFF
103-
ZN_Half_PID direct5T printALL
104-
Damped_PID reverseIP printSUMMARY
105-
NoOvershoot_PID reverse5T printDEBUG
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CohenCoon_PID printPIDTUNER
107-
ZN_PI serialPLOTTER
108-
ZN_Half_PI
109-
Damped_PI
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/* ZN_PID directIP serialOFF
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DampedOsc_PID direct5T printALL
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NoOvershoot_PID reverseIP printSUMMARY
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CohenCoon_PID reverse5T printDEBUG
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Mixed_PID
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ZN_PI
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DampedOsc_PI
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NoOvershoot_PI
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CohenCoon_PI
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Mixed_PI
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*/
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```
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@@ -132,18 +137,19 @@ void SetTuningMethod(TuningMethod TuningMethod);
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#### Query Functions
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```c++
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float GetKp(); // proportional gain
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float GetKi(); // integral gain
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float GetKd(); // derivative gain
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float GetProcessGain(); // process gain
139-
float GetDeadTime(); // process dead time (seconds)
140-
float GetTau(); // process time constant (seconds)
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float GetTimeIntegral(); // process time integral (seconds)
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float GetTimeDerivative(); // process time derivative (seconds)
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float GetKp(); // proportional gain
141+
float GetKi(); // integral gain
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float GetKd(); // derivative gain
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float GetTi(); // integral time
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float GetTd(); // derivative time
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float GetProcessGain(); // process gain
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float GetDeadTime(); // process dead time (seconds)
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float GetTau(); // process time constant (seconds)
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uint8_t GetControllerAction();
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uint8_t GetSerialMode();
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uint8_t GetTuningRule();
150+
uint8_t GetTuningMethod();
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void GetAutoTunings(float * kp, float * ki, float * kd);
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```
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#### Controllability of the process

‎examples/Autotune_PID_v1/Autotune_PID_v1.ino‎

Lines changed: 11 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -29,17 +29,17 @@ float input = 0, output = 0, kp = 0, ki = 0, kd = 0; // tuner
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PID myPID(&Input, &Output, &Setpoint, 0, 0, 0, DIRECT);
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32-
sTune tuner = sTune(&input, &output, tuner.ZN_PID, tuner.directIP, tuner.printALL);
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/* ZN_PID directIP serialOFF
34-
ZN_Half_PID direct5T printALL
35-
Damped_PID reverseIP printSUMMARY
36-
NoOvershoot_PID reverse5T printDEBUG
37-
CohenCoon_PID printPIDTUNER
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ZN_PI serialPLOTTER
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ZN_Half_PI
40-
Damped_PI
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sTune tuner = sTune(&Input, &Output, tuner.Mixed_PID, tuner.directIP, tuner.printALL);
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/* ZN_PID directIP serialOFF
34+
DampedOsc_PID direct5T printALL
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NoOvershoot_PID reverseIP printSUMMARY
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CohenCoon_PID reverse5T printDEBUG
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Mixed_PID
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ZN_PI
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DampedOsc_PI
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NoOvershoot_PI
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CohenCoon_PI
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Mixed_PI
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*/
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void setup() {
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analogReference(EXTERNAL); // AVR
@@ -58,8 +58,9 @@ void loop() {
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case tuner.tunings: // active just once when sTune is done
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tuner.GetAutoTunings(&kp, &ki, &kd); // sketch variables updated by sTune
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myPID.SetMode(AUTOMATIC); // the PID is turned on (automatic)
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myPID.SetSampleTime((testTimeSec * 1000) / samples); // PID sample rate
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Output = 0; // required before switching PID to Automatic
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myPID.SetMode(AUTOMATIC); // the PID is turned on (automatic)
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myPID.SetTunings(kp, ki, kd); // update PID with the new tunings
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break;
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‎examples/Autotune_Plotter/Autotune_Plotter.ino‎

Lines changed: 12 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -32,17 +32,17 @@ QuickPID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd,
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myPID.iAwMode::iAwClamp,
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myPID.Action::direct);
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35-
sTune tuner = sTune(&Input, &Output, tuner.ZN_PID, tuner.directIP, tuner.serialPLOTTER);
36-
/* ZN_PID directIP serialOFF
37-
ZN_Half_PID direct5T printALL
38-
Damped_PID reverseIP printSUMMARY
39-
NoOvershoot_PID reverse5T printDEBUG
40-
CohenCoon_PID printPIDTUNER
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ZN_PI serialPLOTTER
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ZN_Half_PI
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Damped_PI
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sTune tuner = sTune(&Input, &Output, tuner.Mixed_PID, tuner.directIP, tuner.printALL);
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/* ZN_PID directIP serialOFF
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DampedOsc_PID direct5T printALL
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NoOvershoot_PID reverseIP printSUMMARY
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CohenCoon_PID reverse5T printDEBUG
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Mixed_PID
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ZN_PI
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DampedOsc_PI
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NoOvershoot_PI
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CohenCoon_PI
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Mixed_PI
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*/
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void setup() {
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analogReference(EXTERNAL); // AVR
@@ -60,16 +60,17 @@ void loop() {
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case tuner.tunings: // active just once when sTune is done
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tuner.GetAutoTunings(&Kp, &Ki, &Kd); // sketch variables updated by sTune
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myPID.SetSampleTimeUs((testTimeSec * 1000000) / samples); // PID sample rate (same as sTune)
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Output = 0; // required before switching PID to Automatic
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myPID.SetMode(myPID.Control::automatic); // the PID is turned on (automatic)
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myPID.SetSampleTimeUs((testTimeSec * 1000000) / samples); // PID sample rate
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myPID.SetTunings(Kp, Ki, Kd); // update PID with the new tunings
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break;
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case tuner.runPid: // this case runs once per sample period after case "tunings"
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Input = (analogRead(inputPin) / mvResolution) - bias;
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myPID.Compute();
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analogWrite(outputPin, Output);
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tuner.plotter(Setpoint, 10); // plots every 10th sample
73+
tuner.plotter(Setpoint, 0.5, 6, 1); // plot output scaled 0.5, plot every 6th sample, plot averaged input
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break;
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}
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// put your main code here, to run repeatedly

‎examples/Autotune_QuickPID/Autotune_QuickPID.ino‎

Lines changed: 11 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -32,17 +32,17 @@ QuickPID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd,
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myPID.iAwMode::iAwClamp,
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myPID.Action::direct);
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sTune tuner = sTune(&Input, &Output, tuner.ZN_PID, tuner.directIP, tuner.printALL);
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/* ZN_PID directIP serialOFF
37-
ZN_Half_PID direct5T printALL
38-
Damped_PID reverseIP printSUMMARY
39-
NoOvershoot_PID reverse5T printDEBUG
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CohenCoon_PID printPIDTUNER
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ZN_PI serialPLOTTER
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ZN_Half_PI
43-
Damped_PI
35+
sTune tuner = sTune(&Input, &Output, tuner.Mixed_PID, tuner.directIP, tuner.printALL);
36+
/* ZN_PID directIP serialOFF
37+
DampedOsc_PID direct5T printALL
38+
NoOvershoot_PID reverseIP printSUMMARY
39+
CohenCoon_PID reverse5T printDEBUG
40+
Mixed_PID
41+
ZN_PI
42+
DampedOsc_PI
4443
NoOvershoot_PI
4544
CohenCoon_PI
45+
Mixed_PI
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*/
4747
void setup() {
4848
analogReference(EXTERNAL); // AVR
@@ -60,8 +60,9 @@ void loop() {
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case tuner.tunings: // active just once when sTune is done
6262
tuner.GetAutoTunings(&Kp, &Ki, &Kd); // sketch variables updated by sTune
63+
myPID.SetSampleTimeUs((testTimeSec * 1000000) / samples); // PID sample rate (same as sTune)
64+
Output = 0; // required before switching PID to Automatic
6365
myPID.SetMode(myPID.Control::automatic); // the PID is turned on (automatic)
64-
myPID.SetSampleTimeUs((testTimeSec * 1000000) / samples); // PID sample rate
6566
myPID.SetTunings(Kp, Ki, Kd); // update PID with the new tunings
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break;
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