Actuator and controller scheduling in nonlinear transport-reaction processes

The objective of the present manuscript is to examine the performance improvement of a class of nonlinear transport processes subject to spatiotemporally varying disturbances through the employment of a comprehensive and systematic actuator activation and controller scheduling policy. To attain this objective, it is assumed that multiple groups of actuators are available with only one such actuator group being active over a time interval of fixed length while the remaining actuator groups are kept dormant. Using well-established enhanced controllability and performance improvement measures, the candidate actuator groups are first placed at locations that individually provide certain robustness with respect to an appropriately defined "worst" spatial distribution of disturbances. Once the multiple actuator groups are in place, a switching scheme that dictates the switching of a different actuator group at different time intervals, as well as the corresponding control signal supplied to it while being active, is developed. Embedded in the decision policy is the activation of actuators that lie spatially closer to the spatiotemporal disturbances, thereby improving the control authority of the actuators and enhancing the ability of the system to minimize the effects of this class of disturbances. Indeed, entering disturbances that excite different system modes at different time intervals are best handled by employing the actuators that have increased spatial controllability for the above disturbance modes while simultaneously satisfy certain performance measures. In this manner, the control system designed engages the actuators that are better suited to efficiently perform spatiotemporal disturbance compensation over the duration of certain time intervals. The proposed method is demonstrated through simulations using two typical quasi-linear highly dissipative partial differential equation examples. (C) 2008 Elsevier Ltd. All rights reserved.