Thread: populating matrices

hi all

im am having trouble defining my matrices i have defined them as follows

Code:

float Tx[4][4], Ty[4][4], Tz [4][4];
float Rx[4][4], Ry[4][4], Rz [4][4];

float d, theta;

then i have populated d and theta with variable data and try and do the following to populate matricies

Code:

Tx[][]= { {1, 0, 0,d}, {0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1} } ;
Rx[][]= { {1, 0, 0, 0}, {0, cos(theta), -sin(thera), 0}, {0, sin(theta), cos(theta), 0}, {0, 0, 0, 1} };

and i keep getting lots of syntax errors. is this posible or do i have to it element wise?

many thanks in advance.

jamie

here is the full code it might make what i said above make a little more sence.

Code:

int i;
float d, theta;

/*----- translational motion matices----*/
float Tx[4][4], Ty[4][4], Tz[4][4];

/*----- Rotational motion matices----*/
float Rx[4][4], Ry[4][4], Rz[4][4];

float result[4][4];

	for(i=1;i<index+1;i++){

		struct Joint *create=&Joints[i]; /*local pointer to make addressing quicker*/

		theta=(create->position)*PI/180;
		

		struct Section *temp=&Sections[i];
		d=temp->length;
		


		/*-------------------joint actuation------*/
		if(create->type=='r'){
			if(create->axis=='x'){
				Rx = {  {1, 0, 0, 0}, {0, cos(theta), -sin(theta), 0}, {0, sin(theta), cos(theta), 0}, {0, 0, 0, 1}  };
				mult_matrices(Rx, result, result);
			}
			if(create->axis=='y'){
				Ry[][4] = {  {cos(theta), 0, sin(theta), 0}, {0, 1, 0, 0}, {-sin(theta), 0, cos(theta), 0}, {0, 0, 0, 1} };
				mult_matrices(Ry, result, result);
			}
			if(create->axis=='z'){
				Rz[][4] = {  {cos(theta), -sin(theta), 0, 0}, {sin(theta), cos(theta), 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1} };
				printf("......  %f  ....\n",Rz[1][1]);
				 mult_matrices(Rz, result, result);
			}
		}

		if(create->type=='t'){
			if(create->axis=='x'){
				Tx[4][4] = {  {1, 0, 0, d}, {0, 1, 0, 0}, {0, 0, 1,0}, {0, 0, 0, 1}  };
				mult_matrices(Tx, result, result);	 
			}
			if(create->axis=='y'){
				Ty[4][4] = {  {1, 0, 0, 0}, {0, 1, 0, d }, {0, 0, 1,0}, {0, 0, 0, 1}  };
				mult_matrices(Ty, result, result);
			}
			if(create->axis=='z'){
				Tz[4][4] = {  {1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, d}, {0, 0, 0, 1}  };
				mult_matrices(Tz, result, result);
			}
		}
		
		/*----------------section translation-------*/
			 mult_matrices(Tz, result, result);

		/*----------Angular offset to next joint-------*/ 
	
			 if (i<3){
				 struct Joint *create2=&Joints[i+1];
				
				 if(create2->axis='x'){
						
		
			
				 }
			 }




	}
/*multiplication of all the matricies*/


}

it is part of a much bigger robotics simulation. the aim being to try and transfer between one cordinate frame and another, i think the problem is just the way i am trying to populate the matrices that is the problem. i have been trying to read about the subject but everyone seems to populate them when they define them which i can not do as d and theta change in real time.

thanks again

jamie

Try doing it this way

Code:

   double d = 0.5;
   double theta = 45.0;

   double Tx[4][4] = { 
      1.0, 0.0, 0,d, 
      0.0, 1.0, 0.0, 0.0, 
      0.0, 0.0, 1.0, 0.0, 
      0.0, 0.0, 0.0, 1.0
   };

   double Rx[4][4]= { 
      1.0, 0.0, 0.0, 0.0, 
      0.0, cos(theta), -sin(theta), 0.0, 
      0.0, sin(theta), cos(theta), 0.0, 
      0.0, 0.0, 0.0, 1.0 
   };

This should get rid of your compile errors and any warnings as well.

yeah thats how i was doing it befor, but theta and d change as the program runs as they are fetched from another structure and using this method the values in the matrix dont get updated.

thankyou for your time

ok thanks Kcpilot i have solved it now i think heres how if anyone is intersted

Code:

void Robot::Posiition(int index){

/*--------------------------------------forward kinematics---------------------------------------------------------*/

int i;
float d=9, theta=1;

/*----- translational motion matices----*/
double Tx[4][4] =	{	{1, 0, 0, d},
			{0, 1, 0, 0},
			{0, 0, 1, 0},
			{0, 0, 0, 1}  
		};
double Ty[4][4] =	{	{1, 0, 0, 0},
			{0, 1, 0, d},
			{0, 0, 1, 0},
			{0, 0, 0, 1}  
		};
double Tz[4][4] ={	{1, 0, 0, 0}, 
		{0, 1, 0, 0}, 
		{0, 0, 1, d}, 
		{0, 0, 0, 1}  
	            };

/*----- Rotational motion matices----*/
double Rx[4][4] =	{   {1, 0,			0,			 0},
		     {0, cos(theta),                    -sin(theta),                               0},
		     {0, sin(theta),                      cos(theta),	                 0},
		     {0, 0,			0,			 1} 
		};
double Ry[4][4]=	{  {cos(theta), 0, sin(theta), 0},
		    {0,              1,   0,              0},
		    {-sin(theta),0, cos(theta), 0}, 
		    {0,              0,	0,           1} 
		};
 double Rz[4][4] =	{  {cos(theta), -sin(theta), 0, 0},
		    {sin(theta), cos(theta),  0, 0},
		    {0,	      0,	          1,  0}, 
		    {0,	      0,	          0,  1} 
	                 };

 double result[4][4] = {	{1, 0, 0, 0},	//Initalised to identity maxtix equivalant to 1
			{0, 1, 0, 0},
			{0, 0, 1, 0},
			{0, 0, 0, 1},	 
		};

	for(i=1;i<index+1;i++){
		struct Joint *create=&Joints[i]; /*local pointer to make addressing quicker*/

		theta=(create->position)*PI/180;

		struct Section *temp=&Sections[i];
		d=temp->length;
		


		/*-----------------------------------Joint Actuation-----------------------------------*/

		/*---Rotational Joints---*/
		if(create->type=='r'){
			if(create->axis=='x'){
				Rx[1][1] = cos(theta);
				Rx[1][2] = -sin(theta);
				Rx[2][1] = sin(theta);
				Rx[2][2] = cos(theta);

				mult_matrices(Rx, result, result);
			
			}
			if(create->axis=='y'){

				Ry[0][0] = cos(theta);
				Ry[0][2] = sin(theta);
				Ry[2][0] = -sin(theta);
				Ry[2][2] = cos(theta);

				mult_matrices(Ry, result, result);
			
			}
			if(create->axis=='z'){
				
				Rz[0][0] = cos(theta);
				Rz[0][1] = -sin(theta);
				Rz[1][0] = sin(theta);
				Rz[1][1] = cos(theta);
				mult_matrices(Rz, result, result);
			 
			}
		/*---section Length translation to next joint-------*/

			Tz[2][3] = d;
			mult_matrices(Tz, result, result);
		}

		/*---Translational Joints---*/
		if(create->type=='t'){
			if(create->axis=='x'){

				Tx[0][3]=d;
				mult_matrices(Tx, result, result);
			
			}
			if(create->axis=='y'){
			
				Ty[1][3]=d;
				mult_matrices(Ty, result, result);
			
			}
			if(create->axis=='z'){
				
				Tz[2][3] = d;
				mult_matrices(Tz, result, result);
			
			}
		}
		
		

		/*----------Angular offset to next joint-------*/ 
	
		if (i<3){
			struct Joint *create2=&Joints[i+1];
				
			if(create2->axis='x'){
					
			
			}
		}

	}

}

appoliges for the indenting it all got changed when i copyed it in i have tried to tidy it up as best as possible