Class PidROS

Class Documentation

class PidROS

Public Functions

template<class NodeT>
inline explicit PidROS(std::shared_ptr<NodeT> node_ptr, std::string prefix = std::string(""), bool prefix_is_for_params = false)

Constructor of PidROS class.

The node is passed to this class to handler the ROS parameters, this class allows to add a prefix to the pid parameters

Parameters:

  • node – ROS node

  • prefix – prefix to add to the pid parameters. Per default is prefix interpreted as prefix for topics.

  • prefix_is_for_params – provided prefix should be interpreted as prefix for parameters. If the parameter is true then “/” in the middle of the string will not be replaced with “.” for parameters prefix. “/” or “~/” at the beginning will be removed.

PidROS(rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_base, rclcpp::node_interfaces::NodeLoggingInterface::SharedPtr node_logging, rclcpp::node_interfaces::NodeParametersInterface::SharedPtr node_params, rclcpp::node_interfaces::NodeTopicsInterface::SharedPtr topics_interface, std::string prefix = std::string(""), bool prefix_is_for_params = false)
void initialize_from_args(double p, double i, double d, double i_max, double i_min, bool antiwindup)

Initialize the PID controller and set the parameters.

Note

New gains are not applied if i_min_ > i_max_

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • i_max – Upper integral clamp.

  • i_min – Lower integral clamp.

  • antiwindup – Anti-windup functionality. When set to true, limits the integral error to prevent windup; otherwise, constrains the integral contribution to the control output. i_max and i_min are applied in both scenarios.

void initialize_from_args(double p, double i, double d, double i_max, double i_min, bool antiwindup, bool save_i_term)

Initialize the PID controller and set the parameters.

Note

New gains are not applied if i_min_ > i_max_

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • i_max – The max integral windup.

  • i_min – The min integral windup.

  • antiwindup – Anti-windup functionality. When set to true, limits the integral error to prevent windup; otherwise, constrains the integral contribution to the control output. i_max and i_min are applied in both scenarios.

  • save_i_term – save integrator output between resets.

void initialize_from_args(double p, double i, double d, double i_max, double i_min, double u_max, double u_min, double trk_tc, bool saturation, bool antiwindup, AntiwindupStrategy antiwindup_strat, bool save_i_term)

Initialize the PID controller and set the parameters.

Deprecated:

{only when antiwindup_strat == AntiwindupStrategy::NONE:} Old anti-windup technique is deprecated and will be removed by the ROS 2 Kilted Kaiju release.

Note

New gains are not applied if i_min_ > i_max_ or if u_min_ > u_max_.

Warning

{If you pass AntiwindupStrategy::NONE, at runtime a warning will be printed:} "Old anti-windup technique is deprecated. This option will be removed by the ROS 2 Kilted Kaiju release."

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • i_max – The max integral windup.

  • i_min – The min integral windup.

  • u_max – Upper output clamp.

  • u_min – Lower output clamp.

  • trk_tc – 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.

  • saturation – Enables output saturation. When true, the controller output is clamped between u_max and u_min.

  • antiwindup – Anti-windup functionality. When set to true, limits the integral error to prevent windup; otherwise, constrains the integral contribution to the control output. i_max and i_min are applied in both scenarios.

  • antiwindup_strat – 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. When a strategy other than ‘none’ is selected, it will override the controller’s default anti-windup behavior.

  • save_i_term – save integrator output between resets.

void initialize_from_args(double p, double i, double d, double u_max, double u_min, double trk_tc, bool saturation, AntiwindupStrategy antiwindup_strat, bool save_i_term)

Initialize the PID controller and set the parameters.

Note

New gains are not applied if u_min_ > u_max_.

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • u_max – Upper output clamp.

  • u_min – Lower output clamp.

  • trk_tc – 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.

  • saturation – Enables output saturation. When true, the controller output is clamped between u_max and u_min.

  • antiwindup_strat – 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.

  • save_i_term – save integrator output between resets.

bool initialize_from_ros_parameters()

Initialize the PID controller based on already set parameters.

Returns:

True if all parameters are set (p, i, d, i_max, i_min, u_max, u_min and trk_tc), False otherwise

void reset()

Reset the state of this PID controller.

Note

save_i_term parameter is read from ROS parameters

void reset(bool save_i_term)

Reset the state of this PID controller.

Parameters:

save_i_term – boolean indicating if integral term is retained on reset()

double compute_command(double error, const rclcpp::Duration &dt)

Set the PID error and compute the PID command with nonuniform time step size. The derivative error is computed from the change in the error and the timestep dt.

Parameters:

  • error – Error since last call (error = target - state)

  • dt – Change in time since last call in seconds

Returns:

PID command

double compute_command(double error, double error_dot, const rclcpp::Duration &dt)

Set the PID error and compute the PID command with nonuniform time step size. This also allows the user to pass in a precomputed derivative error.

Parameters:

  • error – Error since last call (error = target - state)

  • error_dot – d(Error)/dt since last call

  • dt – Change in time since last call in seconds

Returns:

PID command

Pid::Gains get_gains()

Get PID gains for the controller.

Returns:

gains A struct of the PID gain values

void set_gains(double p, double i, double d, double i_max, double i_min, bool antiwindup = false)

Set PID gains for the controller.

Note

New gains are not applied if i_min > i_max

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • i_max – Upper integral clamp.

  • i_min – Lower integral clamp.

  • antiwindup – Antiwindup functionality. When set to true, limits the integral error to prevent windup; otherwise, constrains the integral contribution to the control output. i_max and i_min are applied in both scenarios.

void set_gains(double p, double i, double d, double i_max, double i_min, double u_max, double u_min, double trk_tc = 0.0, bool saturation = false, bool antiwindup = false, AntiwindupStrategy antiwindup_strat = AntiwindupStrategy::NONE)

Initialize the PID controller and set the parameters.

Deprecated:

{only when antiwindup_strat == AntiwindupStrategy::NONE:} Old anti-windup technique is deprecated and will be removed by the ROS 2 Kilted Kaiju release.

Note

New gains are not applied if i_min > i_max or if u_min_ > u_max_.

Warning

{If you pass AntiwindupStrategy::NONE, at runtime a warning will be printed:}

"Old anti-windup technique is deprecated. This option will be removed by

the ROS 2 Kilted Kaiju release."

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • i_max – The max integral windup.

  • i_min – The min integral windup.

  • u_max – Upper output clamp.

  • u_min – Lower output clamp.

  • trk_tc – 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.

  • saturation – Enables output saturation. When true, the controller output is clamped between u_max and u_min.

  • antiwindup – Anti-windup functionality. When set to true, limits the integral error to prevent windup; otherwise, constrains the integral contribution to the control output. i_max and i_min are applied in both scenarios.

  • antiwindup_strat – 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. When a strategy other than ‘none’ is selected, it will override the controller’s default anti-windup behavior.

void set_gains(double p, double i, double d, double u_max, double u_min, double trk_tc, bool saturation, AntiwindupStrategy antiwindup_strat)

Set PID gains for the controller (preferred).

Note

New gains are not applied if u_min_ > u_max_.

Parameters:

  • p – The proportional gain.

  • i – The integral gain.

  • d – The derivative gain.

  • u_max – Upper output clamp.

  • u_min – Lower output clamp.

  • trk_tc – 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.

  • saturation – Enables output saturation. When true, the controller output is clamped between u_max and u_min.

  • antiwindup_strat – 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.

void set_gains(const Pid::Gains &gains)

Set PID gains for the controller.

Note

New gains are not applied if gains.i_min_ > gains.i_max_

Parameters:

gains – A struct of the PID gain values

void set_current_cmd(double cmd)

Set current command for this PID controller.

Parameters:

cmd – command to set

double get_current_cmd()

Return current command for this PID controller.

Returns:

current cmd

std::shared_ptr<rclcpp::Publisher<control_msgs::msg::PidState>> get_pid_state_publisher()

Return PID state publisher.

Returns:

shared_ptr to the PID state publisher

void get_current_pid_errors(double &pe, double &ie, double &de)

Return PID error terms for the controller.

Parameters:

  • pe[out] – The proportional error.

  • ie[out] – The weighted integral error.

  • de[out] – The derivative error.

void print_values()

Print to console the current parameters.

inline rclcpp::node_interfaces::OnSetParametersCallbackHandle::SharedPtr get_parameters_callback_handle()

Return PID parameters callback handle.

Returns:

shared_ptr to the PID parameters callback handle

Protected Attributes

std::string topic_prefix_
std::string param_prefix_