MPid

A microcontroller-friendly PID module.

Description

A light-weight, fast PID library designed for use on embedded systems (but can also run on any machine which has a G++ compiler).

For better performance and control, the PID library supports a generic number type. Number type must support casting to doubles. Fixed-point numbers are recommended for high-speed operation, doubles are recommended for non-time critical algorithms.

Relies on used calling Pid.Run() at a regular and fixed interval (usually in the milli-second range, via an interrupt).

Automatically adjusts Kp, Ki and Kd depending on the chosen time step (Zp, Zi, and Zd are the time-step adjusted values).

DO NOT try and make Kp, Ki, or Kd negative. This results in undefined behaviour.

Smooth Control

Derivative control is only active when at least two calls to Run() have been made (does not assume previous input was 0 on first call, which can cause a huge derivative jolt!).

Easy Debugging

You can print PID debug information by providing a callback via :code:Pid::SetDebugPrintCallback(), which supports method callbacks by utilizing the slotmachine-cpp library.

The following code shows you how to assign a callback for debug printing.

class Printer {
	public:
		void PrintDebug(const char* msg) {
			std::cout << msg;
		}
};

Printer myPrinter;
Pid pidTest;

// Asign callback to Printer's PrintDebug function.
this->pidTest.SetDebugPrintCallback(SlotMachine::CallbackGen<Printer, void, const char*>(&myPrinter, &Printer::PrintDebug));

You can disable all debug info (to free up some memory space) by setting cp3id_config_INCLUDE_DEBUG_CODE in include/Config.hpp to 0. The debug buffer size can be changed with cp3id_config_DEBUG_BUFF_SIZE, again in Config.hpp.

Code Dependencies

Dependency	Delivery	Usage
`<cstdint>`	Standard C++ library	Fixed-width variable type definitions (e.g. `uint32_t`).
MAssert	External module	Providing runtime safety checks against this module.
MUnitTest	External module	Framework for unit tests.

Building

This example assumes you are running on a Linux-like system and have basic build tools like gcc and make installed, as well as cmake.

$ git clone https://github.com/gbmhunter/MFixedPoint.git
$ cd MFixedPoint
$ mkdir build
$ cd build
$ cmake ..
$ make

Usage

// Create a PID object which uses double for all of it's calculations, inputs, and outputs.
Pid<double> pidTest;

main() {
	// Set-up PID controller, non accumulating
	pidTest.Init(
		1.0,									//!< Kp
		1.0,									//!< Ki
		1.0,									//!< Kd
		Pid<double>::PID_DIRECT,				//!< Control type
		Pid<double>::DONT_ACCUMULATE_OUTPUT,	//!< Control type
		10.0,									//!< Update rate (ms)
		-100.0,									//!< Min output
		100.0,									//!< Max output
		0.0										//!< Initial set-point
	);
}

// Call every 10.0ms (as set in Pid.Init())
TimerIsr() {
	// Read input
	input = ReadPin(2);
	// Perform one execution
	pidTest.Run(input);
	// Set output
	SetPin(3) = pidTest.output;
}

See test/PidTest.cpp for more examples.

Issues

For known bugs, desired enhancements e.t.c, see GitHub issues section.

Changelog

See CHANGELOG.md.

artiqsam / MPid