Digital PID controller design for multivariable analogue systems with computational input-delay

Real-time random delay compensation with prediction-based digital redesign

“…The tuning parameter v can be tuned for different requirements [19,30,31]. For delay-free system, v can be simply set to 0.5 indicating that the digital signal will be shifted to the left by a half period so as to minimize A/D conversion error.…”

“…Compared with the previous method [31,32], the newly developed scheme is simplified, while ensuring that unity output feedback line is maintained so that the robustness for modeling error is enhanced. With the previous method, state feedback itself may not be able to achieve zero steady state error, therefore an external input gain is needed.…”

“…Local redesign involves finding a corresponding digital controller c(z) from its analog counterpart c(s) and the conversion is conducted within the scope of controller where input is the error e(t) and output is the control signal u(t); whereas global redesign involves finding a digital controller c(z) from its analog counterpart c(s), but the conversion is conducted from the perspective of the whole system where input is r(t) and output is the plant performance y(t). Global closed-loop redesign takes into account the closed-loop nature of the whole system and has been testified to be more suitable in circumstances with low sampling frequency [31,32].…”

“…Based on the previous works in offline control for fixed delay systems [31,32], this paper presents a simplified and improved methodology of providing online random delay compensation, and real-time physical experiments are conducted to testify its feasibility and correctness.…”

Digital controller design for Bouc–Wen model with high-order hysteretic nonlinearities through approximated scalar sign function

“…This OLM has the exact dynamics of the original nonlinear system at the operating points of interests and minimum modelling errors in the vicinity of those operating points on the trajectory. Then, at each operating point, a proportional integral (PI) controller combined with a state-feedback controller (Zhang, Shieh, and Dunn 2004a;Zhang Shieh, Liu, and Guo 2004b) is applied, through formulating the overall closed-loop design as a LQR optimal control problem. Such a scheme can optimally regulate the multivariable dynamics, regardless of system's stability, dimension and order, minimum phase and system coupling properties.…”