System linearization with Maple - does not evaluate to a module error

Question

I'm trying to apply the steps provided in this tutorial in order to linearize a system using Maple.

1. Create your system of non linear equations
2. Define your linearization points
3. Call the Linearize function and you are done.

I've tried with my system but it does not work. So I decided to try with the equations of the pendulum provided by the tutorial. Once the equations are written, I create the system with:

sys3 := [diff(x(t), t) = y(t), diff(theta(t), t) = phi(t), diff(y(t), t) = -(-3*cos(theta(t))*sin(theta(t))*g-2*u(t)+2*m*L*sin(theta(t))*phi(t)^2)/(-3*cos(theta(t))*m+2*M+2*m), diff(phi(t), t) = -(3*(-sin(theta(t))*g*M-sin(theta(t))*g*m-m*u(t)+m^2*L*sin(theta(t))*phi(t)^2))/((-3*cos(theta(t))*m+2*M+2*m)*m*L)]

set the list with the linearization points

lin_point3 := [phi(t) = 0, x(t) = 0, y(t) = 0, theta(t) = 0, u(t) = 0] 

But when I call the Linearize function and press enter the enter the output is different from the one in the tutorial.

 lin_model3 := Linearize(sys3, [u(t)], [phi(t), x(t), y(t), theta(t)], lin_point3)

When I press the PrintSystem(lin_model3) command I get a does not evaluate to a module error

How can I get this example working? Solution: Solved using Maple 18.