BB.PID.Controller (bb_pid_controller v0.2.2)

General-purpose PID controller for BB robots.

Subscribes to configurable topics for setpoint and measurement values, runs a periodic PID loop, and publishes output to a configurable topic.

Architecture

Setpoint Topic ─────────────────────────┐
(configurable message/field)            │
                                        ▼
                               ┌─────────────────┐
Measurement Topic ────────────►│ BB.PID.Controller│
(configurable message/field)   │                  │
                               │   PIDControl     │
                               │   .step()        │
                               └────────┬─────────┘
                                        │
                                        ▼
                               Output Topic
                               (configurable message/field)

One controller instance = one PID loop. Instantiate multiple controllers for multiple control loops.

Example Usage

defmodule MyRobot do
  use BB

  controller :shoulder_pid, {BB.PID.Controller,
    kp: 2.0, ki: 0.1, kd: 0.05,
    output_min: -1.0, output_max: 1.0,

    setpoint_topic: [:actuator, :base_link, :shoulder, :pid],
    setpoint_message: BB.Message.Actuator.Command.Position,
    setpoint_path: [:position],

    measurement_topic: [:sensor, :base_link, :shoulder, :encoder],
    measurement_message: BB.Message.Sensor.JointState,
    measurement_path: [:positions, 0],

    output_topic: [:actuator, :base_link, :shoulder, :servo],
    output_message: BB.Message.Actuator.Command.Velocity,
    output_field: :velocity,
    output_frame_id: :shoulder,

    rate: 100
  }

  # ... rest of robot definition
end

Path Extraction

The *_path options are lists of atoms (field names) and integers (list indices):

setpoint_path: [:position]          # extracts payload.position
measurement_path: [:positions, 0]   # extracts payload.positions |> Enum.at(0)
path: [:data, :readings, 0, :value] # extracts payload.data.readings[0].value