LWRJointImpedanceController Class Reference

Joint impedance controller interface for the KUKA Light-Weight Robot IV. More...

#include <LWRJointImpedanceController.h>

Inheritance diagram for LWRJointImpedanceController:

List of all members.

Public Member Functions
	LWRJointImpedanceController (const char *InitFileName)
	Constructor.
	~LWRJointImpedanceController (void)
	Destructor.
int	StartRobot (const float &TimeOutValueInSeconds=120.0)
	Starts the robot.
void	SetCommandedJointPositions (const float *CommandedJointPositions)
	Copies the desired joint position vector into the data telegram to be send to the KRC unit.
void	SetCommandedJointTorques (const float *CommandedJointTorques)
	Copies the desired joint torque vector into the data telegram to be send to the KRC unit.
void	SetCommandedJointStiffness (const float *CommandedJointStiffness)
	Copies the desired joint stiffness vector into the data telegram to be send to the KRC unit.
void	SetCommandedJointDamping (const float *CommandedJointDamping)
	Copies the desired joint damping vector into the data telegram to be send to the KRC unit.

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Detailed Description

Joint impedance controller interface for the KUKA Light-Weight Robot IV.

Definition at line 72 of file LWRJointImpedanceController.h.

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Constructor & Destructor Documentation

LWRJointImpedanceController::LWRJointImpedanceController

(

const char *

InitFileName

)

[inline]

Constructor.

The constructor creates the actual object of the class FastResearchInterface, which is used by this class.This constructor performs several procedures. It

• initializes all class attributes,
• reads all parameters of the initialization file specified by InitFileName using the method FastResearchInterface::ReadInitFile(), which further on uses an object of the class InitializationFileEntry,
• sets the priority, which is specified in the initialization file to the calling thread,
• creates the timer thread FastResearchInterface::TimerThreadMain() running at the priority, which is specified in the initialization file,
• creates the communication thread FastResearchInterface::KRCCommunicationThreadMain() running at the priority, which is specified in the initialization file,
• creates the Console object FastResearchInterface::OutputConsole, which provides the possibility of using Console::printf() in real-time parts of the object, and
• creates the DataLogging object FastResearchInterface::DataLogger, which provides the possibility of logging low-level control data under real-time conditions.
  
  
  

In case,

• the initialization file specified by InitFileName cannot be opened,
• the initialization file specified by InitFileName does not contain all required parameters (cf. The Initialization File for the Fast Research Interface Library), or
• one of the threads FastResearchInterface::KRCCommunicationThreadMain() or FastResearchInterface::TimerThreadMain() cannot be created successfully

the constructor lets the calling process terminate and exits with a value of EXIT_FAILURE.

Parameters:

InitFileName

A pointer to an array of char values containing the path and filename of the initialization file (e.g., "/home/lwrcontrol/etc/980039-FRI-Driver.init"). For details about this file, please refer to The Initialization File for the Fast Research Interface Library.

Note:

All threads of this class, that is,

• the timer thread FastResearchInterface::TimerThreadMain(),
• the communication thread FastResearchInterface::KRCCommunicationThreadMain(),
• the output thread of the class Console, Console::ConsoleThreadMain(), and
• the calling thread
  
  

use the Fifo scheduling policy (SCHED_FIFO).

Attention:

The call of the constructor does not fulfill any real-time requirements.

Definition at line 87 of file LWRJointImpedanceController.h.

LWRJointImpedanceController::~LWRJointImpedanceController

(

void

)

[inline]

Destructor.

The destructor deletes the actual object of the class FastResearchInterface, which is used by this class.This destructor performs a set of procedures to cleanly shutdown the robot:

• The communication thread FastResearchInterface::KRCCommunicationThreadMain() is terminated and joins the calling thread. If it still receives data packages from the KRC unit, it will be checked whether the robot has to be shutdown, too (cf. FastResearchInterface::StopRobot()). If the thread does not receive any UDP data telegrams anymore, a signal (SIGTERM) will be sent to the thread FastResearchInterface::KRCCommunicationThread.
• The timer thread FastResearchInterface::TimerThreadMain() is terminated and joins the calling thread.
• If the data logger still has data in its memory that has not been written to a log file yet, this file will be written.
• The DataLogging object FastResearchInterface::DataLogger is deleted.
• The Console object FastResearchInterface::OutputConsole is deleted.
  
  

Attention:

The call of the destructor does not fulfill any real-time requirements.

Definition at line 100 of file LWRJointImpedanceController.h.

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Member Function Documentation

void LWRJointImpedanceController::SetCommandedJointDamping

(

const float *

CommandedJointDamping

)

[inline]

Copies the desired joint damping vector into the data telegram to be send to the KRC unit.

Parameters:

CommandedJointDamping

A pointer to an array of float values; the array has to have at least a size of seven elements. The desired joint damping vector is copied from this array.

Note:

This value will only be relevant if the joint impedance controller is active.

See also:

tFriCmdData

Definition at line 178 of file LWRJointImpedanceController.h.

void LWRJointImpedanceController::SetCommandedJointPositions

(

const float *

CommandedJointPositions

)

[inline]

Copies the desired joint position vector into the data telegram to be send to the KRC unit.

Parameters:

CommandedJointPositions

A pointer to an array of float values; the array has to have at least a size of seven elements. The desired joint position vector (given in radians) is copied from this array.

Note:

This value will only be relevant if the joint position or the joint impedance controller is active.

See also:

tFriCmdData

Definition at line 133 of file LWRJointImpedanceController.h.

void LWRJointImpedanceController::SetCommandedJointStiffness

(

const float *

CommandedJointStiffness

)

[inline]

Copies the desired joint stiffness vector into the data telegram to be send to the KRC unit.

Parameters:

CommandedJointStiffness

A pointer to an array of float values; the array has to have at least a size of seven elements. The desired joint stiffness vector is copied from this array.

Note:

This value will only be relevant if the joint impedance controller is active.

See also:

tFriCmdData

Definition at line 163 of file LWRJointImpedanceController.h.

void LWRJointImpedanceController::SetCommandedJointTorques

(

const float *

CommandedJointTorques

)

[inline]

Copies the desired joint torque vector into the data telegram to be send to the KRC unit.

Parameters:

CommandedJointTorques

A pointer to an array of float values; the array has to have at least a size of seven elements. The desired joint torque vector (given in Nm) is copied from this array.

Note:

This value will only be relevant if the joint impedance or the joint torque controller is active.

See also:

tFriCmdData

Definition at line 148 of file LWRJointImpedanceController.h.

int LWRJointImpedanceController::StartRobot

(

const float &

TimeOutValueInSeconds = 120.0

)

[inline, virtual]

Starts the robot.

This method performs a complete start-up procedure of the robot arm. The following steps are executed:

1. Before the KRL program FRIControl (cf.KRL File: FRIControl.src) is started by the user, the constructor FastResearchInterface::FastResearchInterface::() should be called in order to prevent any loss of UDP packages.
2. If the KRC unit is not already in Monitor Mode (i.e., no communication between the remote host and the KRC unit is performed), the method waits for the call of the KRL function friOpen() to receive UDP messages in order to let the KRC unit switch to Monitor Mode.
3. Once, the KRC unit runs in Monitor Mode, the method sets the KRL variable $FRI_FRM_INT[16] to a value of 10, which lets the KRL program FRIControl call the function friStart() in order to switch from Monitor Mode to Command Mode.
4. In the transition phase, the following command variables are sent from the remote host to the KRC unit (see also: FastResearchInterface::SetControlScheme()):
   
   
   • Joint position control
     • Desired joint position vector = Current joint position vector
     
     
   • Cartesian impedance control
     • Desired Cartesian pose frame = Last commanded Cartesian pose frame
     • Desired Cartesian pose offset frame = Identity frame
     • Desired additional force/torque vector = Zero vector
     • The desired Cartesian stiffness and damping values remain unchanged and may be specified by the user by using the methods FastResearchInterface::SetCommandedCartStiffness() and FastResearchInterface::SetCommandedCartDamping(), if required.
     
     
   • Joint impedance control
     • Desired joint position vector = Current joint position vector
     • Desired joint position offset vector = Zero vector
     • Desired additional joint torque vector = Zero vector
     • The desired joint stiffness and damping values remain unchanged and may be specified by the user by using the methods FastResearchInterface::SetCommandedJointStiffness() and FastResearchInterface::SetCommandedJointDamping(), if required.
     
     
   • Joint torque control:
     • Desired joint torque vector = Zero vector
   
   
5. After the KRC unit switched to Command Mode, the method waits until the robot is ready for operation, that is, until the result value of FastResearchInterface::IsMachineOK() is true.

The complete start-up procedure must not take longer than TimeOutValueInSeconds seconds. If completed successfully, the robot arm is ready for operation. This method should be used pairwise with the method FastResearchInterface::StopRobot() in order to ensure a safe and error-free operation.

Parameters:

ControlMode

Either value of the enumeration FastResearchInterface::LWRControlModes: FastResearchInterface::JOINT_POSITION_CONTROL for joint position control FastResearchInterface::CART_IMPEDANCE_CONTROL for Cartesian impedance control FastResearchInterface::JOINT_IMPEDANCE_CONTROL for joint impedance control If this method is called by an object derived from the class LWRBaseControllerInterface, this parameter is automatically set by their respective method for starting the robot.

TimeOutValueInSeconds

Timeout value in seconds for the user to turn on the robot arm by using the KUKA Control Panel. The default value of this optional parameter is 120 seconds.

Returns:

• ENOTCONN if no connection between the remote host and the KRC unit could be established. Please check
  • whether the KRC unit is turned on and the Ethernet cable (e.g., a crossed cable) is plugged in on both nodes,
  • whether the KRL program FRIControl (cf.KRL File: FRIControl.src) has been started, or
  • whether the KRC node is configured correctly in particular w.r.t. the network settings (cf. Introduction).
• EALREADY if the KRC unit is already in command mode, that is, the KRL function friStart() was already called by a previous call of FastResearchInterface::StartRobot(). If the robot is not ready for operation (i.e., the result of FastResearchInterface::IsMachineOK() is false), call FastResearchInterface::StopRobot() first. It might be required to check whether the KRC unit is running correctly, and whether the KRL program KRL program FRIControl (cf.KRL File: FRIControl.src) is being executed.
• ETIME if the start-up procedure could not be completed within the specified time interval of TimeOutValueInSeconds
• EOK if no error occurred.

See also:

FastResearchInterface::StopRobot()

Implements LWRBaseControllerInterface.

Definition at line 114 of file LWRJointImpedanceController.h.

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

• include/LWRJointImpedanceController.h