This is for controlling a double pendulum. Approximate solutions are fine. It would be hard to do this with numerical solutions in Maple because the simulation must be done with other software. I'm trying to solve a linear quadratic regulation problem with an infinite horizon. So, I am trying to minimise x(t) where the dynamics are dx/dt = Ax(t) + Bu(t) u(t) is a vector in R^2 representing the joint torques. The cost at time t is |x|+|u| and the optimal control signal is given by u(t) = B^T P x(t), where P is the solution to the equation S=0. The dynamics of the double pendulum impose some order on A and B. I have also tried the solve(.) command with those explicit A,B (there are 4 parameters instead of 8) but it still chugs. Thanks!