This paper proposes nonlinear optimal controller
and observer schemes based on a θ-D approximation approach
for surface-mounted permanent magnet synchronous motors
(PMSMs). By applying the θ-D method in both the controller
and observer designs, the unsolvable Hamilton–Jacobi–Bellman
equations are switched to an algebraic Riccati equation and statedependent
Lyapunov equations (SDLEs). Then, through selecting
the suitable coefficient matrices, the SDLEs become algebraic, so
the complex matrix operation technique, i.e., the Kronecker product
applied in the previous papers to solve the SDLEs is eliminated.
Moreover, the proposed technique not only solves the problem of
controlling the large initial states, but also avoids the excessive
online computations. By utilizing a more accurate approximation
method, the proposed control system achieves superior control performance
(e.g., faster transient response, more robustness under
the parameter uncertainties and load torque variations) compared
to the state-dependent Riccati equation-based control method and
conventional PI controlmethod. The proposed observer-based control
methodology is tested with an experimental setup of a PMSM
servo drive using a Texas Instruments TMS320F28335 DSP. Finally,
the experimental results are shown for proving the effectiveness
of the proposed control approac
