chrono::vehicle::ChSteeringController Class Reference

Description

Base class for all steering path-following PID controllers.

The base class implements the basic functionality to control the error between the location of a sentinel point (a point at a look-ahead distance in front of the vehicle) and the current target point.

The parameters of a steering controller can also be specified through a JSON file; a sample JSON input file is as follows:

 {
     "Gains":
     {
         "Kp":   0.5,
         "Ki" : 0.0,
         "Kd" : 0.0
     },

     "Lookahead Distance": 20.0
 }

Data collection from the steering controller can be started (restarted) and suspended (stopped) as many times as desired. Data collected so far can be written to a file. The tab-separated output ASCII file contains on each line the time, location of the target point, and location of the sentinel point.

#include <ChSteeringController.h>

Inheritance diagram for chrono::vehicle::ChSteeringController:

Collaboration diagram for chrono::vehicle::ChSteeringController:

Public Member Functions
	ChSteeringController ()
	Construct a steering controller with default parameters. More...
	ChSteeringController (const std::string &filename)
	Construct a steering controller with parameters read from a JSON file.
virtual	~ChSteeringController ()
	Destructor.
void	SetLookAheadDistance (double dist)
	Specify the look-ahead distance. More...
void	SetGains (double Kp, double Ki, double Kd)
	Set the gains for the PID controller.
const ChVector &	GetSentinelLocation () const
	Return the current location of the sentinel point. More...
const ChVector &	GetTargetLocation () const
	Return the current value of the target point. More...
virtual void	Reset (const ChVehicle &vehicle)
	Reset the PID controller. More...
double	Advance (const ChVehicle &vehicle, double step)
	Advance the state of the PID controller. More...
void	StartDataCollection ()
	Start/restart data collection.
void	StopDataCollection ()
	Suspend/stop data collection.
bool	IsDataCollectionEnabled () const
	Return true if data is being collected.
bool	IsDataAvailable () const
	Return true if data is available for output.
void	WriteOutputFile (const std::string &filename)
	Output data collected so far to the specified file.

Protected Member Functions
virtual void	CalcTargetLocation ()=0
	Calculate the current target point location. More...

Protected Attributes
double	m_dist
	look-ahead distance
ChVector	m_sentinel
	position of sentinel point in global frame
ChVector	m_target
	position of target point in global frame
double	m_Kp
double	m_Ki
	PID controller gains.
double	m_Kd
double	m_err
	current error (signed distance to target point)
double	m_errd
	error derivative
double	m_erri
	integral of error
utils::CSV_writer *	m_csv
	CSV_writer object for data collection.
bool	m_collect
	flag indicating whether or not data is being collected

Constructor & Destructor Documentation

ChSteeringController()

chrono::vehicle::ChSteeringController::ChSteeringController

(

)

Construct a steering controller with default parameters.

Default values are all gains set to zero (no controller). The user is responsible for calling SetGains and SetLookAheadDistance.

Member Function Documentation

Advance()

double chrono::vehicle::ChSteeringController::Advance	(	const ChVehicle &	vehicle,
		double	step
	)

Advance the state of the PID controller.

This function performs the required integration for the integral component of the PID controller and returns the calculated steering value.

CalcTargetLocation()

virtual void chrono::vehicle::ChSteeringController::CalcTargetLocation ( )

protectedpure virtual

Calculate the current target point location.

All derived classes must implement this function to calculate the current location of the target point, expressed in the global frame. The location of the sentinel point at the current time is calculated and available in m_sentinel.

Implemented in chrono::vehicle::ChPathSteeringControllerStanley, chrono::vehicle::ChPathSteeringControllerSR, chrono::vehicle::ChPathSteeringControllerXT, chrono::vehicle::ChPathSteeringController, and chrono::synchrono::ChMultiplePathSteeringController.

GetSentinelLocation()

const ChVector& chrono::vehicle::ChSteeringController::GetSentinelLocation ( ) const

inline

Return the current location of the sentinel point.

The return vector is expressed in the global reference frame.

GetTargetLocation()

const ChVector& chrono::vehicle::ChSteeringController::GetTargetLocation ( ) const

inline

Return the current value of the target point.

The return vector is expressed in the global reference frame.

Reset()

void chrono::vehicle::ChSteeringController::Reset ( const ChVehicle &  vehicle )

virtual

Reset the PID controller.

This function must be called at a configuration where a valid location for the sentinel point can be calculated. The default implementation in the base class simply calculates the new sentinel point location and sets all errors to 0.

Reimplemented in chrono::synchrono::ChMultiplePathSteeringController, chrono::vehicle::ChPathSteeringControllerStanley, chrono::vehicle::ChPathSteeringControllerSR, chrono::vehicle::ChPathSteeringControllerXT, and chrono::vehicle::ChPathSteeringController.

SetLookAheadDistance()

void chrono::vehicle::ChSteeringController::SetLookAheadDistance ( double  dist )

inline

Specify the look-ahead distance.

This defines the location of the "sentinel" point (in front of the vehicle, at the given distance from the chassis reference frame).

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The documentation for this class was generated from the following files:

• /builds/uwsbel/chrono/src/chrono_vehicle/utils/ChSteeringController.h
• /builds/uwsbel/chrono/src/chrono_vehicle/utils/ChSteeringController.cpp