Combined feedforward and error-based active disturbance rejection control for diesel particulate filter thermal...

In this paper, a novel control solution, which combines a feedforward control law and an error-based version of the active disturbance rejection control (ADRC) scheme, is proposed for the exhaust gas temperature control during the thermal regeneration process of a diesel particulate filter in the exhaust line of a diesel engine. Attributed to the complexity of the controlled upstream diesel oxidation catalyst (DOC), its thermodynamics is firstly captured and characterized by a set of linear models through identification modeling. Then, a novel error-based ADRC controller, in which the separated components in conventional ADRC such as the extended state observer (ESO) and the feedback compensator are restructured into a single, modularized control function block, is designed by applying the identified nominal DOC model. In order to further unburden the error-based ESO for better achievements, a combined feedforward compensator is well designed on the basis of the principle of energy balance. Thus a hybrid, 2-degree-of-freedom (2-DOF) controller is developed for better dynamic performance of the controlled DOC system. Its stability performance is also analyzed in the work. The robustness and advantages of the presented hybrid control scheme are finally validated and compared with a well-tuned regular PID-based controller by means of extensive simulation and experimental tests. The results show that the proposed hybrid controller is capable of providing more accurate and faster temperature response and is less sensitive to the variation of system parameters and external disturbances. Moreover, as the error-based ADRC in the hybrid scheme takes the reference tracking error as its direct input and is compatible with the regular PID controller in terms of input and output interfaces, it herein provides an appealing control scheme for existing applications as a substitute for the conventional PID-based controllers to achieve improved performance.