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 – 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 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 – antiwindup.

  • 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_min and i_max), 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(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_