A New Smith Predictor and Fuzzy Immune Control for Hybrid Networked Control Systems

Transcription

1 Proceeding of the International MultiConference of Engineer and Comuter Scientit 29 Vol II IMECS 29, March 8-2, 29, Hong Kong A New Smith Predictor and Fuzzy Immune Control for Hybrid Networked Control Sytem Du Feng, Du Wencai, Lei Zhi Abtract To aim at time-variant or uncertain delay in the hybrid ed control ytem (HNCS) of the wired and wirele, a well a Smith redictor model and real model of the controlled lant might be mimatch, a novel aroach i rooed that a new Smith redictor combined with fuzzy immune control for the HNCS. Becaue new Smith redictor hide redictor model of the delay into real data tranmiion rocee, further all delay no longer need to be meaured, identified or etimated on-line. It i alicable to ome occaion that delay are random, time-variant or uncertain, oibly large comared to one, even ten amling eriod, at the ame time, there are ome data droout in cloed loo. Baed on IEEE 82. b/g (WLAN) and CSMA/CD (Ethernet) reectively in the inner and outer cloed loo, the reult of imulation how validity of the control cheme, and indicate that ytem ha better dynamic erformance and robutne. Index Term Hybrid ed control ytem (HNCS), wirele ed control ytem (WNCS), delay, Smith redictor. I. INTRODUCTION A wirele ed control ytem (WNCS) i one in which a control loo i cloed via the wirele. The WNCS have many comelling alication, for examle, the wirele enor have found imortant alication in environmental monitoring, agriculture, building and indutrial automation, machine condition monitoring, intelligent tranortation ytem, health care, urveillance, and defene. On the other hand, there ha alo been an increaing trend for control ytem to utilize digital communication for exchanging information between enor and controller and/or controller and actuator a well a between ubytem or ytem that hare the ame communication due to flexibility and ignificant cot aving introduced by. The i a factor that hould not be neglected becaue of the ue of the communication hared by other alication, and communication delay and acket loe may occur []-[4]. Thee iue become more ignificant in wirele where there commonly exit the fading time varying throughut in the communication channel a Manucrit received December, 28. Du Feng i with the College of Information Science & Technology, Hainan Univerity, Haikou, CO China (hone: ; fax: ; dufeng488@ ina.com). Du Wencai i with the College of Information Science & Technology, Hainan Univerity, Haikou, CO China ( dufeng488@ yahoo.com.cn). Lei Zhi i with the Sichuan Univerity, Chengdu, CO 673 China ( dufeng488@hotmail.com). well a the contraint and uncertaintie, uch a, the limited energy, bandwidth, and comuting ower, channel fading, time varying caacity, out-of-equence data, tranmiion delay, acket loe, etc. There i an imerative need for new theory and algorithm for control, etimation and deciion making that take thee uncertaintie and contraint into conideration and addre interlay among communication, comuting and control. Thee roblem have timulated a trong reearch interet in the WNCS within the control community. Many of the reearch work baed on auming the delay i contant [5]-[7], or ditribution i known, or delay i horter than one amling eriod, delay through the introduction of buffer i larger than one amling eriod [8]. Baed on Smith redictor, but need to meaured on-line, identified or etimated delay[9]-[], etc. Thee overfull otulate might roduce imractical reult and might limit their alication. Although delay i an imortant factor that need to be conidered for control ytem imlemented over indutrial, it ha not been well defined or tudied by tandard organization defining rotocol [2]. The biology immune ytem i characterized by it trong robutne and elf-adatability even when encountering many diturbance and uncertain condition. It ha become a new reearch field a an intelligent information roce ytem after the neural and evolutionary comutation [3], and ha obtained ome reearch fruit [4], uch a attern recognition, robot control, adative control etc. Beide, fuzzy controller can realize any linear and nonlinear function. Therefore, baed on the immune feedback law, ome tudie [5]-[8] further rooed fuzzy immune control to advance the control erformance uch a robut and adative ability. In thi aer, a novel aroach i rooed that new Smith redictor combined with the fuzzy immune control for the hybrid ed control ytem (HNCS) of the wired and wirele. It enhance the ytem robutne and realize double Smith dynamic rediction comenation for the delay of the and controlled lant. Furthermore, the delay in the return ath can totally be eliminate, while remove the all delay in the forward ath from the loo. Therefore, the traffic on the return ath do not need to be cheduled, thereby allow utilizing the caacity of the communication channel more effectively than tatic or dynamic cheduling could, and imultaneouly increae ytem robutne when there are data droout in return ath. Where delay are allowed to be random, time-variant and uncertain, oibly large comared to one, even ten amling eriod and they are no need to be meaured, identified or etimated on line. Baed ISBN: IMECS 29

2 Proceeding of the International MultiConference of Engineer and Comuter Scientit 29 Vol II IMECS 29, March 8-2, 29, Hong Kong on IEEE 82. b/g (WLAN) in the inner cloed loo and CSMA/CD (Ethernet) in the outer cloed loo, the reult of imulation how validity of the control cheme, and indicate that ytem of the HNCS ha better dynamic erformance and robutne. Thi aer i organized for the four ection a follow: ection II analyze the Smith redictor and rooe a new Smith redictor for the WNCS and HNCS, and introduce the fuzzy immune control for the HNCS. The imulation i decribed in ection III, and concluion in ection IV. controller node C() II. PROBLEM DESCRIPTION A. Structure of the WNCS In the WNCS, the delay i rimary factor which influence on the ytem erformance. The tyical tructure of the WNCS i hown a fig.. wirele actuator end u e -τ ca recv u lant G () Where G m () i rediction model of the G (), the τ cm and τ cam are rediction value of the τ c and τ ca reectively. The cloed loo tranfer function of the ytem i given a follow y ()/ r () = Ce () G()/( + Ce () G() e ca ca c cam cm Ce () G () e + CG () ()) m When τ cam = τ ca, τ cm = τ c, G m () = G (), the rediction model can aroximate the true model, the above (2) i reduced to m (2) y() r() = C() e G ()( + C() G ()) (3) ca According to the (3), the fig.2 can be treated a fig.3. C() G () Fig. 3 Equivalent control ytem e -τ ca recv y e -τ c end y wirele enor node Fig. Structure of the WNCS. We aume that enor i time-driven; controller and actuator are event-driven, and the actuator and enor are co-located on the ame node. Where G () i controlled lant without delay, the C() i controller, the r and y are inut and outut of ytem reectively, the τ c and τ ca are delay, the τ c i from enor to controller, and the τ ca i from controller to actuator. The total delay (τ = τ c + τ ca ) i larger than one, even ten amling eriod. The cloed loo tranfer function i given by ca () () () ca c y r Ce G()( Ce () = + G() e ) () From the (), we can be een that e -τ ca and e -τ c have been contained in the denominator of the cloed loo tranfer function. They can degrade the erformance of the WNCS and even caue ytem intability. B. Smith Predictor for the WNCS The internal comenation loo i cloed around controller ide of wirele, the Smith redictor can be decribed a Fig.2. r G m () C() e -τ cm G m ()e -τ cam e -τ ca wirele e -τ c G () y Though Smith redictor can totally eliminate the delay τ c in the return ath, remove the delay τ ca in the forward ath from the cloed loo, when the rediction model can accurately aroximate the true model, and the delay can be totally comenated. However, the above-mentioned Smith redictor ha ome roblem: ) It i difficult to atify comlete comenation condition. Firt, becaue of uncertainty of wirele delay, it i hard to get the recie rediction model of the τ c and τ ca. Secondly, on account of the clock of node might be aynchronou [9], it i difficult to get the exact value of delay by meaurement on-line, identification or etimate. Thirdly, owing to delay reult in vacancy amling and multi-amling, the Smith redictor will bring error of comenation model. 2) Becaue delay τ ca occur in a roce that i controller tranmiion data to actuator, therefore it i imoible that data are truly redicted in the controller node beforehand, no matte method i adoted, and the rediction error of delay τ ca i alway exitent. 3) When delay large comared to one, even ten amling eriod, a lot of memory unit are required for toring old data, conume memory reource and increae calculation delay, horten life of the wirele node. 4) When the controlled lant include delay τ, the denominator of tranfer function in the (3) will contain exonent e -τ. Therefore, the tability of the WNCS hould be affected. C. New Smith Predictor for the WNCS We aim at exitent roblem of the fig.2, if the controlled lant with delay τ i know, a new Smith dynamic redictor i hown in Fig. 4. Where τ m i rediction value of the τ, thu the cloed loo tranfer function of the WNCS i given a follow Fig. 2 WNCS with Smith redictor ISBN: IMECS 29

3 Proceeding of the International MultiConference of Engineer and Comuter Scientit 29 Vol II IMECS 29, March 8-2, 29, Hong Kong ca y ()/ r () = Ce () G() e /( + CG () () + m ca m c Ce () ( G() e G () e ) e ) When τ m = τ, G m () = G (), the rediction model can accurately aroximate true model, above (4) i reduced to m Fig. 4 WNCS with new Smith redictor. (4) ca y() r() = C() e G () e ( + C() G ()) (5) A can be een from the (5), the effect of the delay have been comletely eliminated from the denominator of the (5). C() G m () According to the (5), the fig.4 can be treated a fig.5. C() G () e -τ ca wirele e -τ c G ()e -τ e -τ ca Fig. 5 Equivalent control ytem From the fig.4 to fig. 5 and the (5), we can ee ) New Smith redictor realize the double Smith dynamic rediction comenation on tructure for the delay of and dead time delay of the controlled lant. 2) The all delay of the forward ath are removed from the cloed loo and aear a gain block before the outut, and the time-variant uncertain delay in the return ath i totally eliminated from the ytem. Further, it can cancel effect of the delay and the dead time delay of the controlled lant for the ytem tability in the cloed loo, and it enhance the control quality. 3) Becaue the delay on the return ath can totally be eliminated, therefore the traffic on the return ath doe not need to be cheduled, and the outut ignal of the enor, whenever oible, can be tranmitted back to remote controller node on line. Thi allow utilizing the caacity of the communication channel more effectively than tatic or dynamic cheduling could. On the other hand, increae ytem robutne when there are data acket droout on the return ath of the WNCS. 4) The new Smith redictor i the real-time, on-line and dynamic redictor, and it doen t include the redictor model of all delay on actualization. Becaue the information flow aed through the delay which are true delay in the data tranmiion roce, therefore delay no longer need to be meaured, identified or etimated on line. Therefore it reduce the requirement of the clock ynchronization of the node. Furthermore, it avoid etimate error which are brought due to inaccurate model, and avoid node memory reource to be wated when the delay are identified or etimated. At the ame time, it avoid G m ()e -τ m e -τ comenation error, which are brought by delay owing to vacancy-amling and multi-amling. D. Structure of the HNCS The cacade control i a common control tructure in roce control ytem, ervomechanim and oition control of the robot etc [2]. The reaon for cacade control intead of ingle loo control i that it can give a much better comenation for diturbance, and ha fater reone [2]. Uually, a cacade control ytem conit of two control loo; an inner cloed loo i embedded within an outer cloed loo [22]. The hybrid ed control ytem (HNCS) with the cacade control tructure i hown in fig.6. outer-loo wired c e -τ g 2 e -τ 2 c2 c 2 e -τ ca2 g e -τ e -τ c e -τ c2 inner-loo wirele Fig. 6 Structure of the HNCS In the outer-loo, the r i inut of ytem, and y i outut of the controlled lant g ()e -τ. The τ c and τ c2 are delay reectively. The τ c i from enor to controller c (), and the τ c2 i from the c () to controller c 2 (). In the inner-loo, the y 2 i outut of the controlled lant g 2 ()e -τ 2. The τ c2 and τ ca2 are wirele delay reectively. The τ c2 i from enor to the c 2 (), and the τ ca2 i from the c 2 () to actuator, thi actuator i ued for imlementing control to the controlled lant g 2 ()e -τ 2. We aume that enor are time-driven; controller and actuator are event-driven. In the Fig.3, the cloed-loo tranfer function can be given by y () r () = c() e c() e g() e g() e (+ c e c e g e g e e + c2 ca c2 ca2 2 c () 2() 2() () ca 2 2 c 2 c2() e g2() e e ) From the (6), we can ee that all delay have been contained in the denominator. Their exitence will degrade ytem erformance and even caue ytem intability. E. HNCS with the New Smith Predictor By mean of the method from the Fig.4, the ytem of the fig.6 can be treated a fig.7. g g c + c g m c e -τ g 2 e -τ 2 c2 c 2 e -τ ca2 g e -τ e -τ c e -τ c2 g g e -τ g m e -τ m The cloed loo tranfer function of the Fig.7 i given by y 2 g e -τ y 2 Fig. 7 HNCS with new Smith redictor (6) ISBN: IMECS 29

4 Proceeding of the International MultiConference of Engineer and Comuter Scientit 29 Vol II IMECS 29, March 8-2, 29, Hong Kong c() e c() e g() e g() e y () ( + c2() g ()) = r () c () c () g () g () ( + c ( ) g ( )) c2 ca m ( A B ) (7) auxiliary cell T h i T h (k), imact of T on B i T (k), and all imetu that B cell received i Sk ( ) = T( k) T( k) () h c () e ( g () e g () e ) e A = ( + c ( ) g ( )) ca 2 2 c B = c () e c () e ( g () e g () e g () e g () e ) e ( c() g ()) c2 ca m c m + 2 When g m () = g (), g () = g 2 (), τ m = τ, τ = τ 2, c () = c 2 (), above (7) i reduced to y () c () e c () e g () e g () e = r() ( + c () g () + c () c () g () g ()) c2 ca (8) (9) () According to the Fig.7 and the (), we can ee ) The new Smith redictor can cancel effect from the τ c and τ c2, the τ c2 and τ ca2, the τ and τ 2 for ytem tability, and realize double Smith dynamic rediction comenation for the delay and the dead time delay of the controlled lant on tructure. 2) In the Fig.7, there are no τ cm and τ c, τ c and τ ca, and the delay no longer need to be meaured on-line, identified or etimated, allow delay to be random, time-variant or uncertain. If only atifie g m () = g (), g () = g 2 (), τ m = τ, τ = τ 2, c () = c 2 (), the Smith redictor i alway effective. 3) Becaue the node of the HNCS are all intelligent node, it i eay to be imlemented. 4) The c 2 () often adot P controller, and the c () can adot PID control, alo adot intelligent control trategy when the controlled lant i time-variant, or nonlinear, a well a the Smith redictor model might be imrecie. F. Fuzzy Immune Control A i known, immune i a ecial hyiological reaction in bioome, correonding antibody i roduced to reit attacking antigen, which i detroyed by hagocytoi or articular enzyme generated by antibody. Immune ytem i comoed of antibody and lymhocyte, which i made u of T cell (auxiliary cell T h and ureor cell T ) roduced by thymocyte and B cell created by marrow. When antigen invade organim and i digeted by urrounding cell, meage are ent to T h and T cell, and B cell i timulated to create more antibody o a to eliminate antigen. If quantity of antigen i large, much more auxiliary cell T h yield, but number of ureor cell T reduce, which reult in more B cell roduction; if antigen become le, number of T increae and that of T h decreae, which reult in decreae of B cell. Synergim between ureor mechanim and main feedback mechanim i realized via immune ytem quick reone to antigen and tabilizing immune ytem [23]. Baed on the immune feedback theory, auming the number of k th generation of antigen i ε(k), the outut of Where T h (k) = k ε(k), T (k) = k 2 f((k), Δ(k))ε(k). If number of antigen ε(k) i uoed to be equivalent to the error e(k), and overall imetu S(k) that B received i equivalent to u(k), following control cheme i gained uk ( ) = kek ( ) k2 f( uk ( ), Δuk ( )) ek ( ) = K( η f( uk ( ), Δuk ( ))) ek ( ) = k e( k) (2) Where K = k i control of reone eed, k =K (-ηf (u(k), Δu(k))) i roortional gain, the η = k 2 / k i ued to control the tabilization effect, and f(u(k),δu(k)) i a elected nonlinear function. In order to determine f (u(k),δu(k)), fuzzy control theory i utilized to acquire an aroximate function. Following control rule are defined to determine f (u(k), Δu(k)): ) If u(k) i P and Δu(k) i P then f (u(k), Δu(k)) i N. 2) If u(k) i P and Δu(k) i N then f (u(k), Δu(k)) i Z. 3) If u(k) i N and Δu(k) i P then f (u(k), Δu(k)) i Z. 4) If u(k) i N and Δu(k) i N then f (u(k), Δu(k)) i P. In the rule above, we ue fuzzy logical AND, OR oeration of Zadeh, adot common ued anti-fuzzy way of mom to obtain the outut f (u(k),δu(k)) of fuzzy controller, o a to contruct fuzzy immune PID controller. We can aure negative feedback when η f(u(k),δu(k)), that i, aure the ytem table, ηf(u(k),δu(k)) rereent oitive feedback control. If η = or f (u(k),δu(k)) =, the controller i jut a a regular linear PID controller. So outut of immune PID controller i uk ( ) = uk ( ) + k(( ek ( ) ek ( )) + kek i ( ) + k (() e k 2( e k ) + e( k 2)) d (3) While the k i regulated by fuzzy immune cheme, the k i and k d i modified online uing fuzzy control cheme to adat well to different e and error change rate ec. III. SIMULATION EXPERIMENT We elect the imulation oftware TrueTime.5 [24]. In the inner cloed loo, wirele adot IEEE 82.b/g (WLAN), data rate i 8, bit/, tranmit ower i 2. dbm, receiver ignal threhold i 48. dbm, ath lo exonent i 3.5, act timeout i.4, error coding threhold i.3, the ditance between node i 2 m, and maximum ignal reach i m. In the outer cloed loo, the wired adot CSMA/CD (Ethernet), and data rate i 8, bit/. There are ome data droout in the inner and outer cloed loo, and lo robability i.5 in outer cloed loo. The amling eriod of the enor are., and the reference ignal r adot quare wave ignal and it amlitude i from.5 to.5 in the outer cloed loo. In the inner cloed loo, we elect three elfame controlled lant2, lant4 and lant6. They are the firt-order lu dead time delay ytem a follow: ISBN: IMECS 29

5 Proceeding of the International MultiConference of Engineer and Comuter Scientit 29 Vol II IMECS 29, March 8-2, 29, Hong Kong P inner. () 6 inner ( 2) G e = e + (4) Their redictor model are given by m inner. () G 6 m inner e = e ( + 2) (5) In the outer cloed loo, alo elect three elfame controlled lant, lant3 and lant5, and they are the econd order lu dead time delay ytem a follow: outer.2 2 ( ) 77 outer ( 6 77) G e = e + + (6) Their redictor model are given by m outer.2 2 ( ) 77 m outer ( 6 77) G e = e + + (7) The HNCS and HNCS2 are comoed by the lant and lant2, lant3 and lant4, reectively, imultaneouly are imlemented control by new Smith redictor combined with fuzzy immune PID lu P control, and their outut are y and y3 reectively. The HNCS3 i comoed by the lant5 and lant6, imultaneouly i imlemented control by the fuzzy immune PID lu P control, and it outut i y5. In order to reearch ytem robutne, we change model arameter of the HNCS2, and make model arameter of Smith redictor and true controlled lant3 and lant4 are mimatch. Where true controlled lant4 in the inner cloed loo i changed from the (4) to the (7) a follow c inner.2 () 2 c inner (2 5) G e = e + (7) At the ame time, the controlled lant3 in the outer cloed loo i changed from the (6) to the (8) a follow c outer.3 2 ( ) 26 c outer ( 65 57) G e = e + + (8) But, the Smith redictor model arameter of true controlled lant3 and lant4 are alway unchanged to kee the (5) and (7) in entire imulation roce. Meanwhile, all tuned arameter of the controller comletely deend on the (4) and (6), where fuzzy immune controller arameter are K =.26, k i =.24, k d =.9, η =.68; and roortion gain of the P controller i k -inner = 2. In the imulation roce, data from the amling and control are encaulated in the ame data ackage for the wired or wirele tranmiion. The imulation reult i dilayed in fig.8 to fig.6. y, y3, y5 Fig. 8 y5 y3 - y time() Outut y, y3 and y5. The y and y3 are new Smith redictor combined with fuzzy immune lu P control (model arameter of true lant3 and lant4 with it Smith redictor are mimatching). The y5 i fuzzy immune lu P control. dca2 dc2 dc2 dc τca2 () τc2 () τc2 () τc ().2 time(). time() time (). time () Fig.2 Network delayτ ca2 i from controller2 to actuator2 5 time() τ Fig.9 Network delay c Fig. Network delay c2 i from enor to controller Fig. Network delayτ c2 i from enor2 to controller2 d τ Fig. 3 Data droout c i from controller to controller2 i from enor to controller time() Fig. 4 Data droout dc 2 i from controller to actuator 2 time() d Fig. 5 Data droout c2 i from enor2 to controller2 2 time() Fig. 6 Data droout dca2 i from controller2 to actuator2 ISBN: IMECS 29

6 Proceeding of the International MultiConference of Engineer and Comuter Scientit 29 Vol II IMECS 29, March 8-2, 29, Hong Kong From the fig.8 to fig.6, we can ee ) The delay τ c, τ c2 and τ ca2 are random, time-variant or uncertain, and τ c2 i time-variant. The maximum of the τ c, τ c2 and τ ca2 are reectively.38,.38 and.22, their all exceed ten amling eriod (one amling eriod i.). 2) In the outer cloed loo, the data acket droout d c maximum i 7, and the d c2 i 8. In the inner cloed loo, the d c2 maximum i, and the d ca2 i 2. However lot meage conume the bandwidth, but never arrive at the detination. 3) The y (thick dot line) and y3 (thick real line) i timely in tracking quare wave in the fig.8, and the overhoot i le, they comletely atifie erformance requirement. At the ame time, it alo indicate that ytem with new Smith redictor have tronger robutne although the true model arameter of the lant3 and lant4 are mimatching to comare with their Smith redictor model arameter. 4) The y5 give overhoot at.385, along with increae and fluctuation of the delay and data droout. Finally, reult in ytem intability after 3.5, therefore the y5 doen t atify requirement. Simulation reult how that new Smith redictor combined with fuzzy immune control i effective for the HNCS. III. CONCLUSION In order to overcome influence of delay, a novel aroach i rooed that new Smith redictor combined with fuzzy immune control for the HNCS. It tructure i imle, and ha tronger robutne. Therefore it will have wide engineering alication roect. REFERENCES [] J. Y. Wei, Stability analyi of decentralized ed control ytem, Proceeding of the 7th World Congre on Intelligent Control and Automation, June 25-27, 28, Chongqing, China, [2] X. L. Zhu and G. H. Yang, New reult on tability analyi of ed control ytem, 28 American Control Conference Wetin Seattle Hotel, Seattle, Wahington, USA. June -3, [3] W. Zhang, M. S. Branicky,S. M. Philli, Stability of ed control ytem, IEEE Control Syt. Magn., vol.2, No.2,.84 99, 2. [4] Y. Ge, Q. G Chen and M. Jiang, Z.A. Liu. Stability analyi of ed control ytem with data droout and tranmiion delay, Proceeding of the 7th World Congre on Intelligent Control and Automation, June 25-27, 28, Chongqing, China, [5] L. Dugy, E. I. Verriet, Stability and control of time-delay ytem, New York: Sringer, 998. [6] J.P. Richard, Time-delay ytem: an overview of ome recent advance and oen roblem, Automatica, vol. 39, no., , 23. [7] K. Watanabe, E. Nobuyama, A. Kojima, Recent advance in control of time delay ytem VA tutorial review, in Proc. IEEE Conf. Deciion and Control, 996, [8] Y. S. Xiong, L. Yu, J. M. Xu, Deign of liding mode redicting controller for control ytem, Electric Drive Automation, 25(4): 39 4, 23. [9] P. Chen, Y. Dong, S. Ji, The tudy of Smith rediction controller in NCS baed on time delay identification, 24 8th Conference on Control, Automation, Robotic and Viion Kunming. China, 6-9th, December, 24. [] K. B. Fite, J. E. Seich, M. Goldfarb, Tranarency and tability robutne in two-channel bilateral telemaniulation, ASME Journal of Dynamic Sytem, Meaurement t, and Control, 2. [] P. H. Bauer, M.L. Sichitiu, C. Lorand et al. Total delay comenation in LAN control ytem and imlication for cheduling, Proceeding of the American Control Conference Arlington, VA June 25-27, 2, [2] J. P. Thomee, Fieldbu technology in indutrial automation, Proc. IEEE, vol. 93, no. 6,. 73, Jun. 25. [3] S. Gutnikov, Y. Melnikov, A imle non-linear model of immune reone, Chao, Solution and Fractal, 23, 6: [4] D. G. Peng, H. Zhang, P. Yang, et al. A novel immune feedback controller and it alication for main tream temerature ytem, Proceeding of the IEEE International Conference on Automation and Logitic Augut 8-2, 27, Jinan, China, [5] J. L. Catro, M. Delgado, Fuzzy ytem with defuzzification are univeral aroximate, IEEE Tran. Syt., Man, Cybern., vol. 26,.49 52, 996. [6] Y. Ding, A nonlinear PID controller baed on fuzzy-tuned immune feedback law, Proc. of the 3th World Conference on Intelligent Control and Automation, , China, 2. [7] X. Gao, Y. Zhao, W. Guo, and X. Yu, Simulation and reearch of fuzzy immune adative PID control in coke oven temerature control ytem, Proc. of the 6th World Conference on Intelligent Control and Automation, , China, 26. [8] S. Wang, Y. Jiang and H.Yang, Chao otimization trategy on fuzzy immune- PID control of the turbine governing ytem, Proc. of the IEEE International Conference on Intelligent Robot and Sytem, , China, 26. [9] S. Johanneen, Time ynchronization in a local area, IEEE Control Syt. Mag., 24: 6 69, 24. [2] Jang P S and Jung S. Guidance and control of a mobile robot uing neural correction baed on a remotely located enor, Proceeding of the 26 IEEE/RSJ International Conference on Intelligent Robot and Sytem October 9-5, 26, Beijing, China, [2] Guo C G, Song Q and Cai W J. A neural aited cacade control ytem for air handling unit, IEEE Tranaction on Indutrial Electronic, Vol. 54, No., February 27, [22] Talaaz A, Shoohtari A N. Cloed-loo reure control baed on Smith redictor for ga ditribution. 27 Information, Deciion and Control, 27, [23] L. H. Fang, Z. Z. Wu, A. G. Wu, et al. Fuzzy immune elf-regulating PID control of ed control ytem, International Conference on Comutational Intelligence for Modeling Control and Automation, and International Conference on Intelligent Agent, Web Technologie and Internet Commerce (CIMCA-IAWTIC'6), 26. [24] O. L. Martin, H. K. Dan, C. Anton, TrueTime.5-reference manual, Deartment of Automatic Control, Lund Univerity, Sweden, January,27. ISBN: IMECS 29