pid_controller

A PID (proportional/integral/derivative) controller in Elixir. "PID" in this context is not to be confused with process ID.

QUICK START

controller =
  PidController.new(kp: 0.2, ki: 0.1)
  |> PidController.set_setpoint(5.0)

# in a loop
{:ok, output, controller} = PidController.output(input, controller)

OVERVIEW

PidController implements a control loop-style feedback controller similar to what is commonly found in industrial control systems. It takes a measured value from the system under control (the process value or process variable), compares it to a setpoint value to produce an error term, then generates a control value based on proportional, integral, and derivative functions of the error term. The control value is then fed back into the system under control.

For a full description of PID controllers and how they work, see https://en.wikipedia.org/wiki/PID_controller.

While the proportional term is a function of the error value only, the integral and derivative terms are also functions of time. The first iteration of PidController acts as if the output/2 function is being called at regular and consistent intervals, even though in practice this is unlikely. A future version will take into account the elapsed time between calls to output/2.

INSTALLATION

If available in Hex, the package can be installed by adding pid_controller to your list of dependencies in mix.exs:

def deps do
  [
    {:pid_controller, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/pid_controller.