Virtually Euler-Lagrange form for feedback passivation of a wide range of non-Euler-Lagrange systems: Adaptive passivity-based control of hepatitis B disease

In this article, a novel technique of feedback passivation is developed for a wide range of non-Euler-Lagrange systems. The reason for this naming "Virtually Euler-Lagrange" is that it is adopted from the error dynamics of Euler-Lagrange systems. An adaptive passivity-based control strategy is proposed in virtually Euler-Lagrange form to treat hepatitis B virus infection. There are several remarkable differences between classic form of passivation and the proposed method, for example, specific and predefined template of storage function in virtually Euler-Lagrange form, which has positive definite auto-extracted form. So, it will be appropriate and time-saving for designing passivity-based control. On the contrary, the process of passivation and control design in conventional formulation is based on time-invariant input-affine systems; however, in virtually Euler-Lagrange form, the system can belong to a wider category. In this regard, two theorems have been proposed to expand the scope of passivity-based control design. Some control design conditions will be released as a result of using this new method. Furthermore, for the first time, passivity-based control has been implemented in the biological area. Control profile design, simulation results, and sensitivity analysis are carried out to evaluate capability of this control approach. Some main biological limitations are also considered, which make the proposed control more realistic.