In this work, a method for controlling a nonlinear underactuated system using augmented sliding mode control (SMC) is proposed. SMC requires inversion of the input influence matrix to derive the desired control law. In under or over actuated systems this matrix is nonsquare therefore a true inverse does not exist. The proposed control approach demonstrated in this work involves introducing a transformation matrix mapping the systems input influence matrix to a transformed system that is square and thus invertible. The proposed approach is shown to control selectable states with proper choice of the transformation matrix yielding good control performance. The methodology is applied to an underactuated nonlinear fuel cell system to show its viability in a real world application. A sliding mode controller is derived for the full nonlinear system with a switching gain accounting for modeling errors and uncertainties. Simulation results indicate the viability of the proposed control law and demonstrate the robust nature of the control law in the presence of significant modeling errors while maintaining tracking stability. Finally, the augmented SMC is compared to a traditional linear control architecture illustrating the effectiveness and advantages in tracking performance and control effort over traditional methods.

Library of Congress Subject Headings

Sliding mode control; Fuel cells

Publication Date


Document Type


Department, Program, or Center

Mechanical Engineering (KGCOE)


Crassidis, Agamemnon

Advisor/Committee Member

Kolodziej, Jason

Advisor/Committee Member

Das, Tuhin


Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: TJ220.5 .D44 2009


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