The following error occurred converting from sym to double: DOUBLE cannot convert the input expression into a double array.

Hello,

Who can help me solve the following error on matlab

syms q1; syms q2; syms q3; syms q4; syms q5; syms q6; syms qp1; syms qp2; syms qp3; syms qp4; syms qp5; syms qp6;
Q = [q1;q2;q3;q4;q5;q6]; Qp = [qp1;qp2;qp3;qp4;qp5;qp6];

Ri1 = T10(1:3,1:3); Pi1 = T10(1:3,4);
Ri2 = T21(1:3,1:3); Pi2 = T21(1:3,4);
Ri3 = T32(1:3,1:3); Pi3 = T32(1:3,4);
Ri4 = T43(1:3,1:3); Pi4 = T43(1:3,4);
Ri5 = T54(1:3,1:3); Pi5 = T54(1:3,4);
Ri6 = T65(1:3,1:3); Pi6 = T65(1:3,4);

Pi = [Pi1 Pi2 Pi3 Pi4 Pi5 Pi6];
Ri = [Ri1 Ri2 Ri3 Ri4 Ri5 Ri6];

P1 = T01(1:3,4); R1 = T01(1:3,1:3);
P2 = T12(1:3,4); R2 = T12(1:3,1:3);
P3 = T23(1:3,4); R3 = T23(1:3,1:3);
P4 = T34(1:3,4); R4 = T34(1:3,1:3);
P5 = T45(1:3,4); R5 = T45(1:3,1:3);
P6 = T56(1:3,4); R6 = T56(1:3,1:3);

P = [P1 P2 P3 P4 P5 P6];
R = [R1 R2 R3 R4 R5 R6];

Ww(:,1) = [0;0;0];
Vw(:,1) = [0;0;0];
k1 = 1;

for k = 2:7
   Ww(:,k) = (Ri(:,k1:k1+2)*Ww(:,(k-1))) + [0;0;Qp(k-1)];
   Vw(:,k) = Ri(:,k1:k1+2)*(Vw(:,k-1)+(cross(Ww(:,k-1),P(:,k-1))));
   k1 = k1 + 3;
end

And I have this problem

The following error occurred converting from sym to double:
DOUBLE cannot convert the input expression into a double array.