pid_controller.yaml

pid_controller:
  dof_names: {
    type: string_array,
    default_value: [],
    description: "Specifies dof_names or axes used by the controller. If 'reference_and_state_dof_names' parameter is defined, then only command dof names are defined with this parameter.",
    read_only: true,
    validation: {
      unique<>: null,
      not_empty<>: null,
    }
  }
  reference_and_state_dof_names: {
    type: string_array,
    default_value: [],
    description: "(optional) Specifies dof_names or axes for getting reference and reading states. This parameter is only relevant when state dof names are different then command dof names, i.e., when a following controller is used.",
    read_only: true,
    validation: {
      unique<>: null,
    }
  }
  command_interface: {
    type: string,
    default_value: "",
    description: "Name of the interface used by the controller for writing commands to the hardware.",
    read_only: true,
    validation: {
      not_empty<>: null,
    }
  }
  reference_and_state_interfaces: {
    type: string_array,
    default_value: [],
    description: "Name of the interfaces used by the controller getting hardware states and reference commands. The second interface should be the derivative of the first.",
    read_only: true,
    validation: {
      not_empty<>: null,
      size_gt<>: 0,
      size_lt<>: 3,
    }
  }
  use_external_measured_states: {
    type: bool,
    default_value: false,
    description: "Use external states from a topic instead from state interfaces."
  }
  gains:
    __map_dof_names:
      p: {
        type: double,
        default_value: 0.0,
        description: "Proportional gain for PID"
      }
      i: {
        type: double,
        default_value: 0.0,
        description: "Integral gain for PID"
      }
      d: {
        type: double,
        default_value: 0.0,
        description: "Derivative gain for PID"
      }
      derivative_filter_time: {
        type: double,
        default_value: 0.0,
        description: "Time constant (seconds) of the first-order low-pass in the derivative path.
        Continuous form: C_D(s) = D * s / (1 + s * derivative_filter_time). Smaller values => less
        filtering (higher bandwidth); derivative_filter_time = 0 gives an ideal (unfiltered)
        differentiator (not recommended). In discrete time the final difference equation depends on
        'derivative_method' and sample time T.",
        validation: { gt_eq<>: [0.0] }
      }
      u_clamp_max: {
        type: double,
        default_value: .inf,
        description: "Upper output clamp."
      }
      u_clamp_min: {
        type: double,
        default_value: -.inf,
        description: "Lower output clamp."
      }
      i_clamp_max: {
        type: double,
        default_value: .inf,
        description: "Upper integral clamp."
      }
      i_clamp_min: {
        type: double,
        default_value: -.inf,
        description: "Lower integral clamp."
      }
      antiwindup_strategy: {
        type: string,
        default_value: "none",
        description: "Specifies the anti-windup strategy. Options: 'back_calculation',
        'conditional_integration' or 'none'. Note that the 'back_calculation' strategy use the
        tracking_time_constant parameter to tune the anti-windup behavior.",
        validation: {
          one_of<>: [[
            "back_calculation",
            "conditional_integration",
            "none"
          ]]
        }
      }
      integration_method: {
        type: string,
        default_value: "forward_euler",
        description: "Discrete-time scheme for the integral (I) term. Options: 'forward_euler'
        (explicit Euler), 'backward_euler' (implicit Euler), or 'trapezoidal'
        (bilinear/Tustin). In general, 'trapezoidal' offers better accuracy and
        phase characteristics; 'backward_euler' is more numerically stable for larger
        time steps (more dissipative).",
        validation: {
          one_of<>: [[
            "forward_euler",
            "backward_euler",
            "trapezoidal"
          ]]
        }
      }
      derivative_method: {
        type: string,
        default_value: "forward_euler",
        description: "Selects the discrete-time scheme used to discretize the D term of the PID.
        Options: 'forward_euler' (explicit Euler), 'backward_euler' (implicit Euler), or
        'trapezoidal' (bilinear/Tustin). In general, 'trapezoidal' offers better accuracy and phase
        characteristics; 'backward_euler' is more numerically stable for larger
        time steps (more dissipative).",
        validation: {
          one_of<>: [[
            "forward_euler",
            "backward_euler",
            "trapezoidal"
          ]]
        }
      }
      tracking_time_constant: {
        type: double,
        default_value: 0.0,
        description: "Specifies the tracking time constant for the 'back_calculation' strategy. If
        set to 0.0 when this strategy is selected, a recommended default value will be applied."
      }
      error_deadband: {
        type: double,
        default_value: 1.e-16,
        description: "Is used to stop integration when the error is within the given range."
      }
      feedforward_gain: {
        type: double,
        default_value: 0.0,
        description: "Gain for the feed-forward part."
      }
      angle_wraparound: {
        type: bool,
        default_value: false,
        description: "For joints that wrap around (i.e., are continuous).
          Normalizes position-error to -pi to pi."
      }
      save_i_term: {
        type: bool,
        default_value: true,
        description: "Indicating if integral term is retained after re-activation"
      }
      activate_state_publisher: {
        type: bool,
        default_value: false,
        description: "Individual state publisher activation for each DOF. If true, the controller will publish the state of each DOF to the topic `/<controller_name>/<dof_name>/pid_state`."
      }