Model Error Compensator (MEC)
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The Model Error Compensator (MEC) is a compensation structure designed to enhance the robustness of existing control systems. The MEC suppresses the adverse effects of modeling errors and external disturbances on the input–output characteristics of a controlled plant. By attaching the MEC to an existing control system, the compensated plant behaves closely to the nominal model used in the original controller design, thereby preserving the intended control performance.
A key advantage of the MEC is its simplicity and broad applicability. It does not require an inverse model of the plant — unlike disturbance observer-based approaches — making it straightforward to apply to a wide range of systems, including:
Nonlinear systems
Systems with time delay
Non-minimum phase systems
MIMO (multi-input multi-output) systems
The MEC can also be combined with various control schemes such as model predictive control (MPC), PID control, and feedforward control, adding robustness without redesigning the existing controller.
The basic concept was first proposed in 2013 (Okajima et al., JCMSI, 2013), and has since been extended to address polytopic uncertainties, non-minimum phase plants with parallel feedforward compensation, and practical applications including vehicle control and welfare robotics.
For a comprehensive overview, see: H. Okajima, "Model Error Compensator for Adding Robustness toward Existing Control," Preprints of the IFAC World Congress, pp. 3998–4005, 2023. (PDF, Open Access)
Blog article (detailed explanation): Model Error Compensator (MEC): Enhance the Robustness of Existing Control Systems with Simple Compensation
