Controller of a track on either a conveyor belt or a tracked vehicle. The system should be attached to a model. If implementing a tracked vehicle, use also TrackedVehicle system. More...

#include <TrackController.hh>

Public Member Functions
	TrackController ()
	Constructor.

	~TrackController () override
	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

Controller of a track on either a conveyor belt or a tracked vehicle. The system should be attached to a model. If implementing a tracked vehicle, use also TrackedVehicle system.

The system is implemented along the lines of M. Pecka, K. Zimmermann and T. Svoboda, "Fast simulation of vehicles with non-deformable tracks," 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017, pp. 6414-6419, doi: 10.1109/IROS.2017.8206546.

It does not provide 100% plausible track drivetrain simulation, but provides one that is provably better than a set of wheels instead of the track.

Only velocity control is supported - no effort controller is available.

The basic idea of the implementation is utilizing the so called "contact surface motion" parameter of each contact point between the track and the environment. Instead of telling the physics engine to push velocity towards zero in contact points (up to friction), it tells it to maintain the desired track velocity in the contact point (up to friction).

For better behavior when turning with tracked vehicles, it also accepts the position of the center of rotation of the whole vehicle so that it can adjust the direction of friction along the desired circle.

This system does not simulate the effect of grousers. The best way to achieve a similar effect is to set a very high <mu1> for the track links.

System Parameters

<link>: Name of the link the controller controls. Required parameter.
<debug>: If 1, the system will output debugging info and visualizations. The default value is 0.
<track_orientation>: Orientation of the track relative to the link. It is assumed that the track moves along the +x direction of the transformed coordinate system. Defaults to no rotation (0 0 0).
<velocity_topic>: Name of the topic on which the system accepts velocity commands. Defaults to /model/${model_name}/link/${link_name}/track_cmd_vel.
<center_of_rotation_topic>: The topic on which the track accepts center of rotation commands. Defaults to /model/${model_name}/link/${link_name}/track_cmd_center_of_rotation.
<max_command_age>: If this parameter is set, each velocity or center of rotation command will only act for the given number of seconds and the track will be stopped if no command arrives before this timeout.
<odometry_topic>: The topic on which the track odometry (i.e. position and instantaneous velocity) is published. This can be used e.g. to simulate a conveyor with encoder feedback. Defaults to /model/${model_name}/link/${link_name}/odometry.
<odometry_publish_frequency>: the frequency (in Hz) at which the odometry messages are published. Defaults to 50 Hz.
<min_velocity>/<max_velocity>: Min/max velocity of the track (m/s). If not specified, the velocity is not limited (however the physics will, in the end, have some implicit limit).
<min_acceleration>/<max_acceleration>: Min/max acceleration of the track (m/s^2). If not specified, the acceleration is not limited (however the physics will, in the end, have some implicit limit).
<min_jerk>/<max_jerk>: Min/max jerk of the track (m/s^3). If not specified, the acceleration is not limited (however the physics will, in the end, have some implicit limit).

Examples

See example usage in worlds example/conveyor.sdf and example/tracked_vehicle_simple.sdf.

Constructor & Destructor Documentation

◆ TrackController()

TrackController ( )

Constructor.

◆ ~TrackController()

~TrackController ( )

override

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.