IO linearization, stability, and control of an input non-affine thermoelectric system

We consider a novel control architecture for an input non-affine thermoelectric system, which is used to control the temperature of an object subject to unknown thermal disturbances. A key component in this architecture is given by an input-output linearizing feedback controller to deal with the nonlinear dynamics associated with the input. This enables us to use linear control techniques with the associated performance guarantees. Using a Lyapunov-based stability analysis we derive sufficient conditions for asymptotic stability in the nominal operating regime. To prevent instability outside the nominal operating regime, e.g. in the face of large disturbances where stability is inevitably compromised, we propose to saturate the control input by using state-dependent bounds. These bounds automatically trade-off performance and stability, thereby avoiding the need for complicated stability analysis per application, and as such, allowing the designer to focus on performance. The effectiveness of the nonlinear control approach is demonstrated through measurement results.