  A new approach to control design based on optimal control is proposed.
Instead of expensive computations of the value function for different penalties
on the states and inputs, we use a fixed value function and study combinations
of input and state penalty that are compatible with this value function. This
drastically simplifies the role of the Hamilton- Jacobi-Bellman equation, since
it is no longer a partial differential equation to be solved, but an algebraic
relationship between different terms of the cost. The paper illustrates this
idea in different examples, including H-infinity control and optimal control of
coupled oscillators.
