Tham khảo tài liệu 'adaptive control system part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Adaptive Control Systems 81 significant advances in adaptive and robust control in recent years control of systems with large-size uncertainty remains a difficult task. Not only are the control problems complicated so is the analysis of stability and performance. It is well known 12 14 that classical adaptive algorithms prior to 1980 were all based on the following set of standard assumptions or variations of them i An upper bound on the plant order is known. ii The plant is minimum phase. iii The sign of high frequency gain is known. iv The uncertain parameters are constant and the closed loop system is free from measurement noise and input output disturbances. Classical adaptive algorithms are known to suffer from various robustness problems 34 . A number of attempts have been made since 1980 to relax the assumptions above. A major breakthrough occurred in the mid-1980s 17 21 35 for adaptive control of LTV plants with sufficiently small in the mean parameter variations. Later attempts were made for a broader class of systems. Fast varying continuous-time plants were treated in 36 assuming knowledge of the structure of the parameter variations. By using the concept of polynomial differential integral operators the problem of model reference adaptive control was dealt with in 32 for a certain class of continuous-time plants with fast time-varying parameters. An interesting approach based on some internal self-excitation mechanism was considered in 7 for a general class of LTV discrete-time systems. The global boundedness of the state was proved. However it must be noted that the presence of such self-excitation signals in a closed loop system is often undesirable. In another research line a number of switching control algorithms have been proposed recently by several authors 2 6 8 20 23 24 31 thus significantly weakening the assumptions in i - iv . Both continuous and discrete linear time-invariant systems were considered. Research in this direction was originated
