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136 lines
4.2 KiB
Markdown
136 lines
4.2 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/PID_RT/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/PID_RT/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/PID_RT/blob/master/LICENSE)
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[](https://github.com/RobTillaart/PID_RT/releases)
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# PID_RT
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Arduino library for PID controller.
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## Description
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The PID_RT class allows the user to instantiate a PID controller.
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This library allows one to
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- adjust the K parameters runtime.
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- stop / start computing runtime.
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(to be elaborated)
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#### Some PID background
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- https://en.wikipedia.org/wiki/PID_controller
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- https://www.ni.com/nl-nl/innovations/white-papers/06/pid-theory-explained.html
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- https://www.youtube.com/watch?v=wkfEZmsQqiA
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E-book
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- https://www.elektor.nl/pid-based-practical-digital-control-with-raspberry-pi-and-arduino-uno-e-book
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## Interface
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```cpp
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#include "PID_RT.h"
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```
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### Constructor
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- **PID_RT()** minimal constructor.
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- **PID_RT(float sp, float Kp, float Ki, float Kd)** constructor that sets minimal parameters to get started.
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### Core
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- **void reset()** resets internals to startup (Kp == Ki == Kd == 0).
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- **void setPoint(float sp)** sets the setPoint, that needs to be reached.
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- **float getSetPoint()** read back the setPoint.
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- **bool compute(float input)** does one iteration of the PID controller.
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Returns **true** after a calculation is done.
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Returns **false** if not computed, either due to stop flag or not yet time to do the calculation.
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- **float getOutput()** get the last calculated output value.
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- **bool setK(float Kp, float Ki, float Kd)** Set the initial **P I D** parameters as a group.
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Overwrites the values set in the constructor.
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### Start Stop
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- **void start()** enable the PID controller to **compute()** new output values.
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- **void stop()** disable the PID controller, see **compute()**.
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- **bool isRunning()** return the enable/disable flag.
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### Behaviour parameters
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- **bool setInterval(uint32_t interval)** set the interval between two **compute()** calls.
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Returns **true** if changed, otherwise **false**.
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- **uint32_t getInterval()** read back interval set.
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- **void setOutputRange(float rangeMin, float rangeMax)** tune the output range, default 0..100
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- **float getOutputMin()** read back setting rangeMin.
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- **float getOutputMax()** read back setting rangeMax.
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- **void setReverse(bool reverse)** reverse behaviour, seldom needed.
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- **bool getReverse()** read back the setting.
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### K-parameters
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- **bool setKp(float Kp)** runtime updates are allowed - at your own risk.
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- **bool setKi(float Ki)** runtime updates are allowed - at your own risk.
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- **bool setKd(float Kd)** runtime updates are allowed - at your own risk.
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- **float getKp()** read back setting.
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- **float getKi()** read back setting.
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- **float getKd()** read back setting.
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### Proportional
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- **void setPropOnInput()** this is default behaviour.
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- **void setPropOnError()** alternative.
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- **bool isPropOnInput()** read back setting.
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- **bool isPropOnError()** read back setting.
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### debugging calls
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- **float getInput()** read last input.
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- **float getLastError()** read the last error.
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- **uint32_t getLastTime()** get the last time **compute()** was called.
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Note this value is incremented with **Interval** every iteration so it
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may have some offset of the actual time. This is chosen as this way it is
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almost sure that no iterations are missed.
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## Operations
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See examples and
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- https://wokwi.com/projects/356437164264235009 (thanks to drf5n)
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## Future
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#### Must
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- update / improve documentation
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- more testing
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#### Should
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- investigate if it works as PI or P controller too.
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- PI as derived or base class?
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- add examples to test more
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- improve unit test
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#### Could
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- add reference to PID book / website?
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- move all code to .cpp
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#### Wont
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