Ackermann steering controller which can be attached to a model with any number of left and right wheels. More...

#include <AckermannSteering.hh>

Public Member Functions
	AckermannSteering ()
	Constructor.

	~AckermannSteering () override=default
	Destructor.

void	Configure (const Entity &_entity, const std::shared_ptr< const sdf::Element > &_sdf, EntityComponentManager &_ecm, EventManager &_eventMgr) override
	Configure the system.

void	PostUpdate (const UpdateInfo &_info, const EntityComponentManager &_ecm) override

void	PreUpdate (const UpdateInfo &_info, EntityComponentManager &_ecm) override

Public Member Functions inherited from System
	System ()=default
	Constructor.

virtual	~System ()=default
	Destructor.

Additional Inherited Members
Public Types inherited from System
using	PriorityType = int32_t
	Signed integer type used for specifying priority of the execution order of PreUpdate and Update phases.

Static Public Attributes inherited from System
static constexpr PriorityType	kDefaultPriority = {0}
	Default priority value for execution order of the PreUpdate and Update phases.

static constexpr std::string_view	kPriorityElementName
	Name of the XML element from which the priority value will be parsed.

Detailed Description

Ackermann steering controller which can be attached to a model with any number of left and right wheels.

System Parameters

<steering_only>: Boolean used to only control the steering angle only. Calculates the angles of wheels from steering_limit, wheel_base, and wheel_separation. Uses gz::msg::Double on default topic name /model/{name_of_model}/steer_angle. Automatically set True when <use_actuator_msg> is True, uses defaults topic name "/actuators".
<use_actuator_msg> True to enable the use of actutor message for steering angle command. Relies on <actuator_number> for the index of the position actuator and defaults to topic "/actuators".
<actuator_number> used with <use_actuator_commands> to set the index of the steering angle position actuator.
<steer_p_gain>: Float used to control the steering angle P gain.
<left_joint>: Name of a joint that controls a left wheel. This element can appear multiple times, and must appear at least once.
<right_joint>: Name of a joint that controls a right wheel. This element can appear multiple times, and must appear at least once.
<left_steering_joint>: Name of a joint that controls steering for left wheel. This element must appear once. Vehicles that steer rear wheels are not currently correctly supported.
<right_steering_joint>: Name of a joint that controls steering for right wheel. This element must appear once.
<wheel_separation>: Distance between wheels, in meters. This element is optional, although it is recommended to be included with an appropriate value. The default value is 1.0m.
<kingpin_width>: Distance between wheel kingpins, in meters. This element is optional, although it is recommended to be included with an appropriate value. The default value is 0.8m. Generally a bit smaller than the wheel_separation.
<wheel_base>: Distance between front and rear wheels, in meters. This element is optional, although it is recommended to be included with an appropriate value. The default value is 1.0m.
<steering_limit>: Value to limit steering to. Can be calculated by measuring the turning radius and wheel_base of the real vehicle. steering_limit = asin(wheel_base / turning_radius) The default value is 0.5 radians.
<wheel_radius>: Wheel radius in meters. This element is optional, although it is recommended to be included with an appropriate value. The default value is 0.2m.
<odom_publish_frequency>: Odometry publication frequency. This element is optional, and the default value is 50Hz.
<min_velocity>: Minimum velocity [m/s], usually <= 0.
<max_velocity>: Maximum velocity [m/s], usually >= 0.
<min_acceleration>: Minimum acceleration [m/s^2], usually <= 0.
<max_acceleration>: Maximum acceleration [m/s^2], usually >= 0.
<min_jerk Minimum>: jerk [m/s^3], usually <= 0.
<max_jerk Maximum>: jerk [m/s^3], usually >= 0.
<topic>: Custom topic that this system will subscribe to in order to receive command messages. This element is optional, and the default value is /model/{name_of_model}/cmd_vel or when steering_only is true /model/{name_of_model}/steer_angle.
<sub_topic>: Custom sub_topic that this system will subscribe to in order to receive command messages. This element is optional, and creates a topic /model/{name_of_model}/{sub_topic}
<odom_topic>: Custom topic on which this system will publish odometry messages. This element if optional, and the default value is /model/{name_of_model}/odometry.
<tf_topic>: Custom topic on which this system will publish the transform from frame_id to child_frame_id. This element is optional, and the default value is /model/{name_of_model}/tf.
<frame_id>: Custom frame_id field that this system will use as the origin of the odometry transform in both the <tf_topic> gz.msgs.Pose_V message and the <odom_topic> gz.msgs.Odometry message. This element if optional, and the default value is {name_of_model}/odom.
<child_frame_id>: Custom child_frame_id that this system will use as the target of the odometry transform in both the <tf_topic> gz.msgs.Pose_V message and the <odom_topic> gz.msgs.Odometry message. This element is optional, and the default value is {name_of_model}/{name_of_link}.

A robot with rear drive and front steering would have one each of left_joint, right_joint, left_steering_joint and right_steering_joint.

References:

Constructor & Destructor Documentation

◆ AckermannSteering()

AckermannSteering ( )

Constructor.

◆ ~AckermannSteering()

~AckermannSteering ( )

overridedefault

Destructor.

Member Function Documentation

◆ Configure()

void Configure	(	const Entity &	_entity,
		const std::shared_ptr< const sdf::Element > &	_sdf,
		EntityComponentManager &	_ecm,
		EventManager &	_eventMgr
	)

overridevirtual

Configure the system.

Parameters

[in]	_entity	The entity this plugin is attached to.
[in]	_sdf	The SDF Element associated with this system plugin.
[in]	_ecm	The EntityComponentManager of the given simulation instance.
[in]	_eventMgr	The EventManager of the given simulation instance.