Comments on “On-line optimal tracking control of continuous-time systems”

In this note, we discuss a previously published paper by Chou et al. [Chou JH, Hsieh CH, Sun JH. On-line optimal tracking control of continuous-time systems. Mechatronics 2004;14:587-97]. The method proposed by authors is based on a sequential on-line identification and optimal control idea. We show that the identification part is not correct in the suggested form and we modify the identification part by suggesting a version of recursive least-squares algorithm. In addition, the identifiability of an arbitrary system is questioned and a counter-example is given. Next, we show that the application of optimal control to the identified linear moving model is not based on any theoretical basis and we present reasons why the method will not work for general systems. In summary, it is shown that the combined on-line identification and control method will not work in general as claimed. Finally, we propose an alternative control method to be applied for dimensionally restricted systems.