(6 intermediate revisions by one user not shown)
Line 13: Line 13:
 
<syntaxhighlight lang="cpp">
 
<syntaxhighlight lang="cpp">
  
#include "control_AllegroHand.h"
+
#include "myAHController.h"
#include "control_AllegroHandCmd.h"
+
#include "myAHControllerCmd.h"
 
+
#define JDOF 16
+
 
+
myAHController::myAHController(rDC rdc)  
control_AllegroHand::control_AllegroHand(rDC rdc)  
+
 
:rControlAlgorithmEx(rdc)
 
:rControlAlgorithmEx(rdc)
, _jdof(0) // everything is NULL to start
+
, _jdof(0)                             // everything is NULL to start
 
, _hand(NULL)
 
, _hand(NULL)
 
, _is_left_hand(false)
 
, _is_left_hand(false)
, _demo_mode(0) // will be used when
+
, _demo_mode(true)   // will be used when
, _demo_start_time(0) // we make our own motion
+
, _demo_start_time(0)           // we make our own motion
 
{
 
{
 
}
 
}
 
+
control_AllegroHand::~control_AllegroHand()
+
myAHController::~myAHController()
 
{
 
{
if (_hand) // if there is already a hand,
+
if (_hand) // if there is already a hand,
 
delete _hand; // delete it before creating a new one
 
delete _hand; // delete it before creating a new one
 
}
 
}
  
 
+
void myAHController::init(int mode)
void control_AllegroHand::init(int mode)
+
 
{
 
{
 
   
 
   
// this property is read from the control_AllegroHand XDL file
+
// this property is read from the myAHController XDL file
 
// to determine if the hand we are using will be the right or the left
 
// to determine if the hand we are using will be the right or the left
 
const TCHAR* prop = NULL;
 
const TCHAR* prop = NULL;
 
prop = getProperty(_T("whichHand"));
 
prop = getProperty(_T("whichHand"));
 
// if using a right hand
 
// if using a right hand
if (prop && _tcsicmp(prop, _T("Right")) == 0)
+
if (prop && _tcsicmp(prop, _T("right")) == 0)
 
{
 
{
_is_left_hand = false; // used to tell left from right
+
_is_left_hand = false;         // used to tell left from right
 
_hand = bhCreateRightHand(); // create the right hand
 
_hand = bhCreateRightHand(); // create the right hand
printf("RIGHT Hand Created.");
 
 
}
 
}
 
// if using a left hand
 
// if using a left hand
Line 54: Line 51:
 
_is_left_hand = true;
 
_is_left_hand = true;
 
_hand = bhCreateLeftHand(); // create the left hand
 
_hand = bhCreateLeftHand(); // create the left hand
printf("LEFT Hand Created.");
 
 
}
 
}
 
assert(_hand); // if hand was not created, abort
 
assert(_hand); // if hand was not created, abort
_hand->SetTimeInterval(0.003); // control period is set (333Hz)
+
_hand->SetTimeInterval(0.003); // control period is set (333Hz)
 
   
 
   
 
_jdof = JDOF; // 16 DOF
 
_jdof = JDOF; // 16 DOF
 
   
 
   
_arrangeJointDevices(); // finds all hand motors and encoders
+
_arrangeJointDevices(); // finds all hand motors and encoders
 
   
 
   
_q.resize(_jdof); // array (16) holds current joint positions
+
_q.resize(_jdof);         // array (16) holds current joint positions
 
_qdot.resize(_jdof); // array (16) holds current joint velocities
 
_qdot.resize(_jdof); // array (16) holds current joint velocities
 
_torque.resize(_jdof); // array (16) holds current joint torques
 
_torque.resize(_jdof); // array (16) holds current joint torques
 
   
 
   
_q.zero(); // all positions, vel and torque set to zero
+
_q.zero();         // all positions, vel and torque set to zero
 
_qdot.zero();
 
_qdot.zero();
 
_torque.zero();
 
_torque.zero();
Line 74: Line 70:
 
_demo_q_des.zero(); // used to create motion sequences
 
_demo_q_des.zero(); // used to create motion sequences
 
   
 
   
memset(_x, 0, sizeof(_x[0])*4); // sets x, y and z position to (0,0,0)
+
memset(_x, 0, sizeof(_x[0])*4); // sets x, y and z position to (0,0,0)
memset(_y, 0, sizeof(_y[0])*4); // for all four fingers
+
memset(_y, 0, sizeof(_y[0])*4); // for all four fingers
 
memset(_z, 0, sizeof(_z[0])*4);
 
memset(_z, 0, sizeof(_z[0])*4);
 
   
 
   
 
}
 
}
 
+
void control_AllegroHand::_arrangeJointDevices()
+
void myAHController::_arrangeJointDevices()
 
{
 
{
printf("\nLooking for Motors and Encoders...\n\n");
 
 
// _jdof is 16.
 
// _jdof is 16.
 
for (int i=0; i<_jdof; i++)
 
for (int i=0; i<_jdof; i++)
Line 91: Line 86:
 
// find all 16 motors on hand (motor1, motor2, ..., motor16)
 
// find all 16 motors on hand (motor1, motor2, ..., motor16)
 
_stprintf(devname, _T("motor%d"), i + 1); // device name built and stored
 
_stprintf(devname, _T("motor%d"), i + 1); // device name built and stored
_motor[i] = findDevice(devname); // device located
+
_motor[i] = findDevice(devname); // device located
printf("found motor%d!\n", i + 1);
+
 
   
 
   
 
// find all 16 encoders on hand (enc1, enc2, ..., enc16)
 
// find all 16 encoders on hand (enc1, enc2, ..., enc16)
 
_stprintf(devname, _T("enc%d"), i + 1);
 
_stprintf(devname, _T("enc%d"), i + 1);
 
_enc[i] = findDevice(devname);
 
_enc[i] = findDevice(devname);
printf("found enc%d!\n\n", i + 1);
 
 
}
 
}
 
   
 
   
 
}
 
}
 
+
void control_AllegroHand::update(const rTime& t)
+
void myAHController::update(const rTime& t)
 
{
 
{
 
_cur_time = t; // controller is updated every control period
 
_cur_time = t; // controller is updated every control period
 
rControlAlgorithm::update(t);
 
rControlAlgorithm::update(t);
//printf("\n%f", _cur_time ); // for testing whether or not the controller is updating
 
// if it works, make sure to comment this out before running again.
 
 
}
 
}
 
+
void control_AllegroHand::_readDevices()
+
void myAHController::_readDevices()
 
{
 
{
 
// all 16 encoder pos. values are read and stored in _q[]
 
// all 16 encoder pos. values are read and stored in _q[]
Line 124: Line 115:
 
}
 
}
 
   
 
   
void control_AllegroHand::_writeDevices()
+
void myAHController::_writeDevices()
 
{
 
{
 
// all 16 motor _torque[] values are written to the motor device
 
// all 16 motor _torque[] values are written to the motor device
Line 137: Line 128:
 
}
 
}
 
}
 
}
 
+
void control_AllegroHand::_compute(const double& t)
+
void myAHController::_compute(const double& t)
 
{
 
{
// calculate control input pased on sensory data here
+
// Computes control inputs
 
}
 
}
 
+
int control_AllegroHand::command(const short& cmd, const int& arg)
+
int myAHController::command(const short& cmd, const int& arg)
 
{
 
{
 
// Handles user-defined commands according to cmd.
 
// Handles user-defined commands according to cmd.
 
// Further information can be retrieved from the second argument.
 
// Further information can be retrieved from the second argument.
 
+
 
// The variable cmd will be received from Allegro Application Studio
 
// The variable cmd will be received from Allegro Application Studio
 
// and will be used to envoke hand actions
 
// and will be used to envoke hand actions
 
return 0;
 
return 0;
 
}
 
}
 
+
 
rControlAlgorithm* CreateControlAlgorithm(rDC& rdc)
 
rControlAlgorithm* CreateControlAlgorithm(rDC& rdc)
 
{
 
{
return new control_AllegroHand(rdc);
+
return new myAHController(rdc);
 
}
 
}
  
Line 166: Line 157:
 
<div class="mw-collapsible-content">
 
<div class="mw-collapsible-content">
 
<syntaxhighlight lang="cpp">
 
<syntaxhighlight lang="cpp">
#ifndef __CONTROL_ALLEGROHAND_H__
 
#define __CONTROL_ALLEGROHAND_H__
 
  
 +
#ifndef __MY_AH_CONTROLLER_H__
 +
#define __MY_AH_CONTROLLER_H__
 +
 
#include <list>
 
#include <list>
 
#include "rControlAlgorithm/rControlAlgorithm.h"
 
#include "rControlAlgorithm/rControlAlgorithm.h"
 
#include "BHand/BHand.h"
 
#include "BHand/BHand.h"
 
+
#define JDOF 16
+
#define JDOF 16
 
+
// control_AllegroHand inherited from algorithm interface class
+
// myAHController inherited from algorithm interface class
class REXPORT control_AllegroHand : public rControlAlgorithmEx
+
class REXPORT myAHController : public rControlAlgorithmEx
 
{
 
{
 
public:
 
public:
control_AllegroHand(rDC rdc);
+
myAHController(rDC rdc);
~control_AllegroHand();
+
~myAHController();
 
+
 
virtual void init(int mode = 0);
 
virtual void init(int mode = 0);
 
virtual void update(const rTime& t);
 
virtual void update(const rTime& t);
 
virtual int  command(const short& cmd, const int& arg = 0);
 
virtual int  command(const short& cmd, const int& arg = 0);
 
+
 
private:
 
private:
 
virtual void _readDevices();
 
virtual void _readDevices();
 
virtual void _writeDevices();
 
virtual void _writeDevices();
 
+
 
virtual void _compute(const rTime& t);
 
virtual void _compute(const rTime& t);
 
+
 
void _arrangeJointDevices();
 
void _arrangeJointDevices();
 
+
 
+
 
private:
 
private:
rTime _cur_time;
+
+
// algorithm variables go here
BHand* _hand;
+
rTime _cur_time;   // current time in controller
bool         _is_left_hand;
+
 
+
BHand* _hand;   // Allegro Hand
rID _motor[16];
+
bool _is_left_hand;   // bool, left?
rID _enc[16];
+
 
+
rID _motor[16];   // motor array
dVector _q;
+
rID _enc[16];   // encoder array
dVector _qdot;
+
dVector _torque;
+
dVector _q;   // joint current position
 
+
dVector _qdot;   // joint current velocity
int _jdof;
+
dVector _torque;   // joint torque
 
+
double _x[4];
+
int _jdof;   // degrees of freedom
double _y[4];
+
double _z[4];
+
double _x[4];   // location of each (4) fingertips
 
+
double _y[4];   // in x, y, and z
 +
double _z[4];
 +
 +
int _demo_mode;   // bool, used later as flag to envoke user control
 +
rTime _demo_start_time;  // time at which the demo mode starts
 +
dVector _demo_q_des;   // desired position for position controller
 +
 
};
 
};
 
+
 
#endif
 
#endif
  
Line 228: Line 226:
 
<div class="mw-collapsible-content">
 
<div class="mw-collapsible-content">
 
<syntaxhighlight lang="cpp">
 
<syntaxhighlight lang="cpp">
#ifndef __CONTROL_ALLEGROHAND_CMD_H__
 
#define __CONTROL_ALLEGROHAND_CMD_H__
 
  
 +
#ifndef __MY_AH_CONTROLLER_CMD_H__
 +
#define __MY_AH_CONTROLLER_CMD_H__
 +
 
#include "rCommand/rCmdManipulator.h"
 
#include "rCommand/rCmdManipulator.h"
 
+
 
// These commands will be fed into command()
 
// These commands will be fed into command()
 
// and can be used to envoke certain actions
 
// and can be used to envoke certain actions
Line 241: Line 240:
 
#define BH_HOME (RCMD_GO_HOME)
 
#define BH_HOME (RCMD_GO_HOME)
 
// #define BH_ONE (RCMD_USER + 1)
 
// #define BH_ONE (RCMD_USER + 1)
 
+
 
#endif
 
#endif
  
Line 310: Line 309:
 
Let's add a bit of code to apply a small torque to all four (4) joints on the index finger and subsequently read the joint position of each and print it to the command window.  
 
Let's add a bit of code to apply a small torque to all four (4) joints on the index finger and subsequently read the joint position of each and print it to the command window.  
  
===control_AllegroHand.cpp===
+
===myAHController.h===
 
<syntaxhighlight lang="cpp">
 
<syntaxhighlight lang="cpp">
void control_AllegroHand::_compute(const double& t)
+
 
 +
#ifndef __MY_AH_CONTROLLER_H__
 +
#define __MY_AH_CONTROLLER_H__
 +
 +
#include <list>
 +
#include "rControlAlgorithm/rControlAlgorithm.h"
 +
#include "BHand/BHand.h"
 +
 +
#define JDOF 16
 +
 +
// myAHController inherited from algorithm interface class
 +
class REXPORT myAHController : public rControlAlgorithmEx
 +
{
 +
public:
 +
myAHController(rDC rdc);
 +
~myAHController();
 +
 +
virtual void init(int mode = 0);
 +
virtual void update(const rTime& t);
 +
virtual int  command(const short& cmd, const int& arg = 0);
 +
 +
private:
 +
virtual void _readDevices();
 +
virtual void _writeDevices();
 +
 +
virtual void _compute(const rTime& t);
 +
 +
void _arrangeJointDevices();
 +
 +
 +
private:
 +
 +
// algorithm variables go here
 +
rTime _cur_time;   // current time in controller
 +
 +
BHand* _hand;   // Allegro Hand
 +
bool _is_left_hand;   // bool, left?
 +
 +
rID _motor[16];   // motor array
 +
rID _enc[16];   // encoder array
 +
 +
dVector _q;   // joint current position
 +
dVector _qdot;   // joint current velocity
 +
dVector _torque;   // joint torque
 +
 +
int _jdof;   // degrees of freedom
 +
 +
double _x[4];   // location of each (4) fingertips
 +
double _y[4];   // in x, y, and z
 +
double _z[4];
 +
 +
int _demo_mode;   // bool, used later as flag to envoke user control
 +
rTime _demo_start_time;  // time at which the demo mode starts
 +
dVector _demo_q_des;   // desired position for position controller
 +
FILE* _fp;
 +
};
 +
 +
#endif
 +
 
 +
</syntaxhighlight>
 +
 
 +
<br>
 +
 
 +
===myAHController.cpp===
 +
<syntaxhighlight lang="cpp">
 +
 
 +
myAHController::myAHController(rDC rdc)
 +
:rControlAlgorithmEx(rdc)
 +
, _jdof(0)                              // everything is NULL to start
 +
, _hand(NULL)
 +
, _is_left_hand(false)
 +
, _demo_mode(true)   // will be used when
 +
, _demo_start_time(0)           // we make our own motion
 +
, _fp(NULL)
 +
{
 +
fopen_s(&fp, "C:\\myAHController.txt", "w");
 +
}
 +
 +
myAHController::~myAHController()
 +
{
 +
if (_hand) // if there is already a hand,
 +
delete _hand; // delete it before creating a new one
 +
 
 +
if (_fp)
 +
fclose(_fp);
 +
}
 +
 
 +
...
 +
 
 +
void myAHController::_compute(const double& t)
 
{
 
{
     
+
// Computes control inputs
 
         // Joints 0, 1, 2 and 3 are commanded at 0.1 N.m
 
         // Joints 0, 1, 2 and 3 are commanded at 0.1 N.m
 
for (int i=0; i<4; i++)
 
for (int i=0; i<4; i++)
Line 320: Line 408:
 
_torque[i] = 0.1;
 
_torque[i] = 0.1;
 
}
 
}
 
+
 
         // Joint positions 0, 1, 2 and 3 are printed
 
         // Joint positions 0, 1, 2 and 3 are printed
 
for (int i=0; i<4; i++)
 
for (int i=0; i<4; i++)
 
{
 
{
printf("%i: %f\t",i,_q[i]);
+
fprintf(_fp, "%i: %f\t",i,_q[i]);
 
}
 
}
printf("\n"); // next line
+
fprintf(_fp, "\n"); // next line
 
+
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
 
+
Compile and execute the shortcut in the Desktop.<br>
That was easy! We can now design any controller with a position input and a torque output.
+
It is necessary to execute the shortcut with Administrator Privilege.<br>
 +
You can see the file that has joint positions in C:\myAHController.txt file.<br>
 +
We can now design any controller with a position input and a torque output.
  
 
==PD Control==
 
==PD Control==

Latest revision as of 18:44, 30 April 2015

In the past 4 tutorials, we learned how to control the Allegro Hand using the included grasping and motions library. In this tutorials, we will take a step back and control the hand at a lower level. We will go over basic filtering of the encoder data and PD position control of the joints.

For this lesson, we must roll back our controller code to the point before we implemented any code to move the hand joints. It may be a better idea to start a new project with the following code. Remember, you configure the project according to the DLL project properties from tutorial 1. Your code should reflect the code developed in the three steps of tutorial 2:


myAHController.cpp

#include "myAHController.h"
#include "myAHControllerCmd.h"
 
 
myAHController::myAHController(rDC rdc) 
:rControlAlgorithmEx(rdc)
, _jdof(0)                              // everything is NULL to start
, _hand(NULL)
, _is_left_hand(false)
, _demo_mode(true)		  // will be used when
, _demo_start_time(0)	          // we make our own motion
{
}
 
myAHController::~myAHController()
{
	if (_hand)		// if there is already a hand,
		delete _hand;	// delete it before creating a new one
}
 
void myAHController::init(int mode)
{
 
	// this property is read from the myAHController XDL file
	// to determine if the hand we are using will be the right or the left
	const TCHAR* prop = NULL;
	prop = getProperty(_T("whichHand"));
	// if using a right hand
	if (prop && _tcsicmp(prop, _T("right")) == 0)
	{
		_is_left_hand = false;		        // used to tell left from right
		_hand = bhCreateRightHand();	// create the right hand
	}
	// if using a left hand
	else
	{
		_is_left_hand = true;
		_hand = bhCreateLeftHand();	// create the left hand
	}
	assert(_hand);				// if hand was not created, abort
	_hand->SetTimeInterval(0.003);	// control period is set (333Hz)
 
	_jdof = JDOF;				// 16 DOF
 
	_arrangeJointDevices();		// finds all hand motors and encoders
 
	_q.resize(_jdof);			        // array (16) holds current joint positions
	_qdot.resize(_jdof);			// array (16) holds current joint velocities	
	_torque.resize(_jdof);			// array (16) holds current joint torques
 
	_q.zero();				        // all positions, vel and torque set to zero
	_qdot.zero();
	_torque.zero();
 
	_demo_q_des.resize(_jdof);		// desired joint positions
	_demo_q_des.zero();			// used to create motion sequences
 
	memset(_x, 0, sizeof(_x[0])*4);	// sets x, y and z position to (0,0,0)
	memset(_y, 0, sizeof(_y[0])*4);	// for all four fingers
	memset(_z, 0, sizeof(_z[0])*4);
 
}
 
void myAHController::_arrangeJointDevices()
{
	// _jdof is 16.
	for (int i=0; i<_jdof; i++)
	{
		// oversited array intialized for storing the device name string
		TCHAR devname[32];
 
		// find all 16 motors on hand (motor1, motor2, ..., motor16)
		_stprintf(devname, _T("motor%d"), i + 1);	// device name built and stored
		_motor[i] = findDevice(devname);		// device located
 
		// find all 16 encoders on hand (enc1, enc2, ..., enc16)
		_stprintf(devname, _T("enc%d"), i + 1);
		_enc[i] = findDevice(devname);
	}
 
}
 
void myAHController::update(const rTime& t)
{
	_cur_time = t;			// controller is updated every control period
	rControlAlgorithm::update(t);
}
 
void myAHController::_readDevices()
{
	// all 16 encoder pos. values are read and stored in _q[]
	float val;
	for (int i=0; i<JDOF; i++)
	{
		if (_enc[i] != INVALID_RID)
		{
			readDeviceValue(_enc[i], &val, 4);
			_q[i] = (float)val;
		}
	}
}
 
void myAHController::_writeDevices()
{
	// all 16 motor _torque[] values are written to the motor device
	float val;
	for (int i=0; i<JDOF; i++)
	{
		val = (float)_torque[i];
		if (_motor[i] != INVALID_RID)
		{
			writeDeviceValue(_motor[i], &val, 4);
		}
	}
}
 
void myAHController::_compute(const double& t)
{
	// Computes control inputs
}
 
int myAHController::command(const short& cmd, const int& arg)
{
	// Handles user-defined commands according to cmd.
	// Further information can be retrieved from the second argument.
 
	// The variable cmd will be received from Allegro Application Studio
	// and will be used to envoke hand actions
	return 0;
}
 
rControlAlgorithm* CreateControlAlgorithm(rDC& rdc)
{
	 return new myAHController(rdc);
}


myAHController.h

#ifndef __MY_AH_CONTROLLER_H__
#define __MY_AH_CONTROLLER_H__
 
#include <list>
#include "rControlAlgorithm/rControlAlgorithm.h"
#include "BHand/BHand.h"
 
#define JDOF	16
 
// myAHController inherited from algorithm interface class
class REXPORT myAHController : public rControlAlgorithmEx
{
public:
	myAHController(rDC rdc);
	~myAHController();
 
	virtual void init(int mode = 0);
	virtual void update(const rTime& t);
	virtual int  command(const short& cmd, const int& arg = 0);
 
private:
	virtual void _readDevices();
	virtual void _writeDevices();
 
	virtual void _compute(const rTime& t);
 
	void _arrangeJointDevices();
 
 
private:
 
	// algorithm variables go here
	rTime		_cur_time;	   // current time in controller
 
	BHand*		_hand;		   // Allegro Hand
	bool		_is_left_hand;	   // bool, left?
 
	rID		_motor[16];	   // motor array
	rID		_enc[16];	   // encoder array
 
	dVector		_q;		   // joint current position
	dVector		_qdot;		   // joint current velocity
	dVector		_torque;	   // joint torque
 
	int		_jdof;		   // degrees of freedom
 
	double		_x[4];		   // location of each (4) fingertips
	double		_y[4];		   // in x, y, and z
	double		_z[4];
 
	int		_demo_mode;	   // bool, used later as flag to envoke user control
	rTime		_demo_start_time;  // time at which the demo mode starts
	dVector		_demo_q_des;	   // desired position for position controller
 
};
 
#endif


myAHControllerCmd.h

#ifndef __MY_AH_CONTROLLER_CMD_H__
#define __MY_AH_CONTROLLER_CMD_H__
 
#include "rCommand/rCmdManipulator.h"
 
// These commands will be fed into command()
// and can be used to envoke certain actions
// by the robot. Allegro Application Studio
// will use these to interface with the
// cotroller plug-in.
#define BH_NONE		(RCMD_USER + 0)
#define BH_HOME		(RCMD_GO_HOME)
// #define BH_ONE		(RCMD_USER + 1)
 
#endif


Contents

[edit] Check the code

Let's quickly compile the code above to make sure we copied everything correctly. It should compile with no errors.

Next, open up AHAS via your virtual Allegro Hand shortcut. None of the buttons should work anymore but you should see the command prompt indication that all motors and encoders have been found. These are all we need!

[edit] Reading and Writing

We have two functions, _readDevices() and _writeDevices(), that are called every control period. For the Allegro Hand controller, this means that the encoder values are accessed and motor commands are calculated and written at 333Hz, or once every 0.003 seconds.


When _readDevices() accessed the encoder data, it saves it to the array _q[]" which has 16 floating point entries (once for each joint). The joint positions in _q are in radians.

Similarly, when writing a torque command to the motors, "_writeDevices()" accesses the 16-long floating-point array _torque[]'. The torque values are in the unit Newton-meters.


Alike _readDevices() and "_writeDevices()", the function '_compute() is also called every control iteration. This is where we will implement are controller code, or the computation of motor torque based on joint positions.


Remember: The 16 joint torque commands and joint positions are stored in float arrays with 16 entries each and indexed as follows:

Finger Joint Index
1 1 0
1 2 1
1 3 2
1 4 3
2 1 4
2 2 5
2 3 6
2 4 7
3 1 8
3 2 9
3 3 10
3 4 11
4 1 12
4 2 13
4 3 14
4 4 15


Let's add a bit of code to apply a small torque to all four (4) joints on the index finger and subsequently read the joint position of each and print it to the command window.

[edit] myAHController.h

#ifndef __MY_AH_CONTROLLER_H__
#define __MY_AH_CONTROLLER_H__
 
#include <list>
#include "rControlAlgorithm/rControlAlgorithm.h"
#include "BHand/BHand.h"
 
#define JDOF	16
 
// myAHController inherited from algorithm interface class
class REXPORT myAHController : public rControlAlgorithmEx
{
public:
	myAHController(rDC rdc);
	~myAHController();
 
	virtual void init(int mode = 0);
	virtual void update(const rTime& t);
	virtual int  command(const short& cmd, const int& arg = 0);
 
private:
	virtual void _readDevices();
	virtual void _writeDevices();
 
	virtual void _compute(const rTime& t);
 
	void _arrangeJointDevices();
 
 
private:
 
	// algorithm variables go here
	rTime		_cur_time;	   // current time in controller
 
	BHand*		_hand;		   // Allegro Hand
	bool		_is_left_hand;	   // bool, left?
 
	rID		_motor[16];	   // motor array
	rID		_enc[16];	   // encoder array
 
	dVector		_q;		   // joint current position
	dVector		_qdot;		   // joint current velocity
	dVector		_torque;	   // joint torque
 
	int		_jdof;		   // degrees of freedom
 
	double		_x[4];		   // location of each (4) fingertips
	double		_y[4];		   // in x, y, and z
	double		_z[4];
 
	int		_demo_mode;	   // bool, used later as flag to envoke user control
	rTime		_demo_start_time;  // time at which the demo mode starts
	dVector		_demo_q_des;	   // desired position for position controller
	FILE* _fp; 
};
 
#endif


[edit] myAHController.cpp

myAHController::myAHController(rDC rdc) 
:rControlAlgorithmEx(rdc)
, _jdof(0)                              // everything is NULL to start
, _hand(NULL)
, _is_left_hand(false)
, _demo_mode(true)		  // will be used when
, _demo_start_time(0)	          // we make our own motion
, _fp(NULL)
{
	fopen_s(&fp, "C:\\myAHController.txt", "w");
}
 
myAHController::~myAHController()
{
	if (_hand)		// if there is already a hand,
		delete _hand;	// delete it before creating a new one
 
	if (_fp)
		fclose(_fp);
}
 
...
 
void myAHController::_compute(const double& t)
{
	// Computes control inputs
        // Joints 0, 1, 2 and 3 are commanded at 0.1 N.m
	for (int i=0; i<4; i++)
	{
		_torque[i] = 0.1;
	}
 
        // Joint positions 0, 1, 2 and 3 are printed
	for (int i=0; i<4; i++)
	{
		fprintf(_fp, "%i: %f\t",i,_q[i]);
	}
	fprintf(_fp, "\n"); // next line
}

Compile and execute the shortcut in the Desktop.
It is necessary to execute the shortcut with Administrator Privilege.
You can see the file that has joint positions in C:\myAHController.txt file.
We can now design any controller with a position input and a torque output.

[edit] PD Control

One of the simplest and most widely used control algorithms, Proportional-Derivative (PD) control can be easily implemented to control the position of a robotic joint.

To use PD control, we need to calculate the error between the joint's set, or desired, position and the joint's current position. For each joint, this error value and a gain value will comprise the proportional controller. Along with the current error, we will also calculate the error's rate of change from time-step to time-step. This will be calculated using the difference between the current and previous error values divided by the time-step.





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