On Maximal Permissiveness in Partially-Observed Discrete Event Systems: Verification and Synthesis Xiang Yin and StΓ©phane Lafortune EECS Department, University of Michigan 13th WODES, May 30-June 1, 2016 , Xiβan, China 0/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Introduction Control Engineering Perspective 2 3 π‘ 0 4 1 5 Plant G π π(π‘) β Ξ β π: πΉ π π(π‘) Supervisor β’ πΉ = πΉ π βͺ πΉ π£π = πΉ π βͺ πΉ π£π β β 2 E ; Disable events in πΉ π based on its observations β’ Supervisor: π: πΉ π β’ Closed-loop Behavior: π(π/π») 1/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Introduction β’ π» = (π, πΉ, π, π¦ 0 ) is a deterministic FSA - π is the finite set of states - πΉ is the finite set of events - π: π Γ πΉ β π is the partial transition function - π¦ 0 is the initial state β’ Safety specification automaton: π πΌ β π (π») 2/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Introduction β’ π» = (π, πΉ, π, π¦ 0 ) is a deterministic FSA - π is the finite set of states - πΉ is the finite set of events - π: π Γ πΉ β π is the partial transition function - π¦ 0 is the initial state β’ Safety specification automaton: π πΌ β π (π») β β 2 πΉ is We say that a supervisor π: πΉ π - Safe, if π(π/π») β π(πΌ) - Maximally Permissive , if for any safe supervisor πβ² , we have π(π/π») β π(πβ²/π») . 2/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Introduction β’ π» = (π, πΉ, π, π¦ 0 ) is a deterministic FSA - π is the finite set of states - πΉ is the finite set of events - π: π Γ πΉ β π is the partial transition function - π¦ 0 is the initial state β’ Safety specification automaton: π πΌ β π (π») β β 2 πΉ is We say that a supervisor π: πΉ π - Safe, if π(π/π») β π(πΌ) - Maximally Permissive , if for any safe supervisor πβ² , we have π(π/π») β π(πβ²/π») . π(πΌ) πππ¦ 1 πππ¦ 2 π(π») 2/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Literature Review β’ F. Lin, and W. M. Wonham. "On observability of discrete-event systems." Inform. Sci., 44.3 (1988): 173- 198. β’ R. Cieslak, et al. "Supervisory control of discrete-event processes with partial observations." IEEE Transactions on Automatic Control, 33.3 (1988): 249-260. - Supremal normal and controllable solution 3/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Literature Review β’ F. Lin, and W. M. Wonham. "On observability of discrete-event systems." Inform. Sci., 44.3 (1988): 173- 198. β’ R. Cieslak, et al. "Supervisory control of discrete-event processes with partial observations." IEEE Transactions on Automatic Control, 33.3 (1988): 249-260. β’ S. Takai, and T. Ushio. "Effective computation of an β π (π») -closed, controllable, and observable sublanguage arising in supervisory control." Sys. Cont. Let. 49.3 (2003): 191-200. β’ K. Cai, R. Zhang, and W. M. Wonham. "Relative observability of discrete-event Systems and its supremal sublanguages." IEEE Trans. Automatic Control, 60.3 (2015): 659-670. - Supremal normal and controllable solution - Solutions larger than supremal normal and controllable solution 3/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Literature Review β’ F. Lin, and W. M. Wonham. "On observability of discrete-event systems." Inform. Sci., 44.3 (1988): 173- 198. β’ R. Cieslak, et al. "Supervisory control of discrete-event processes with partial observations." IEEE Transactions on Automatic Control, 33.3 (1988): 249-260. β’ S. Takai, and T. Ushio. "Effective computation of an β π (π») -closed, controllable, and observable sublanguage arising in supervisory control." Sys. Cont. Let. 49.3 (2003): 191-200. β’ K. Cai, R. Zhang, and W. M. Wonham. "Relative observability of discrete-event Systems and its supremal sublanguages." IEEE Trans. Automatic Control, 60.3 (2015): 659-670. - Supremal normal and controllable solution - Solutions larger than supremal normal and controllable solution - These solutions are sound but not complete 3/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Literature Review β’ F. Lin, and W. M. Wonham. "On observability of discrete-event systems." Inform. Sci., 44.3 (1988): 173- 198. β’ R. Cieslak, et al. "Supervisory control of discrete-event processes with partial observations." IEEE Transactions on Automatic Control, 33.3 (1988): 249-260. β’ S. Takai, and T. Ushio. "Effective computation of an β π (π») -closed, controllable, and observable sublanguage arising in supervisory control." Sys. Cont. Let. 49.3 (2003): 191-200. β’ K. Cai, R. Zhang, and W. M. Wonham. "Relative observability of discrete-event Systems and its supremal sublanguages." IEEE Trans. Automatic Control, 60.3 (2015): 659-670. - Supremal normal and controllable solution - Solutions larger than supremal normal and controllable solution - These solutions are sound but not complete β’ N. Ben Hadj-Alouane, S. Lafortune, and F. Lin. "Centralized and distributed algorithms for on-line synthesis of maximal control policies under partial observation." Discrete Event Dynamic Systems 6.4 (1996): 379-427. β’ X. Yin and S. Lafortune. "Synthesis of Maximally Permissive Supervisors for Partially-Observed Discrete-Event Systems." IEEE Trans. Automatic Control, 61.5 (2016): 1239-1254. - Solutions are both sound and complete - A certain class of maximal policies 3/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Literature Review β’ F. Lin, and W. M. Wonham. "On observability of discrete-event systems." Inform. Sci., 44.3 (1988): 173- 198. β’ R. Cieslak, et al. "Supervisory control of discrete-event processes with partial observations." IEEE Transactions on Automatic Control, 33.3 (1988): 249-260. β’ S. Takai, and T. Ushio. "Effective computation of an β π (π») -closed, controllable, and observable sublanguage arising in supervisory control." Sys. Cont. Let. 49.3 (2003): 191-200. β’ K. Cai, R. Zhang, and W. M. Wonham. "Relative observability of discrete-event Systems and its supremal sublanguages." IEEE Trans. Automatic Control, 60.3 (2015): 659-670. - Supremal normal and controllable solution - Solutions larger than supremal normal and controllable solution - These solutions are sound but not complete β’ N. Ben Hadj-Alouane, S. Lafortune, and F. Lin. "Centralized and distributed algorithms for on-line synthesis of maximal control policies under partial observation." Discrete Event Dynamic Systems 6.4 (1996): 379-427. β’ X. Yin and S. Lafortune. "Synthesis of Maximally Permissive Supervisors for Partially-Observed Discrete-Event Systems." IEEE Trans. Automatic Control, 61.5 (2016): 1239-1254. - Solutions are both sound and complete - A certain class of maximal policies π(πΌ) πππ¦ 3/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Problem Formulation β’ Supervisor Verification Problem. β β , 2 πΉ , verify whether or not π π is maximal. Given a safe supervisor π π : πΉ π 4/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Problem Formulation β’ Supervisor Verification Problem. β β , 2 πΉ , verify whether or not π π is maximal. Given a safe supervisor π π : πΉ π β’ Supervisor Synthesis Problem. β β 2 πΉ , find a safe supervisor π Given a non-maximal safe supervisor π π : πΉ π such that π π π /π» β π π/π» . 4/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Problem Formulation β’ Supervisor Verification Problem. β β , 2 πΉ , verify whether or not π π is maximal. Given a safe supervisor π π : πΉ π β’ Supervisor Synthesis Problem. β β 2 πΉ , find a safe supervisor π Given a non-maximal safe supervisor π π : πΉ π such that π π π /π» β π π/π» . Motivation: Lower bound behavior π π β’ βπ«π· , the infimal controllable and observable super-language β’ π΄(π» πΊ /π―) = π΄ π Achieve both the lower bound and permissiveness β’ 4/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
Bipartite Transition System Information State : a set of states, π½ β 2 π β’ β’ BTS: A bipartite transition system T w.r.t. G is a 7-tuple π , β ππ π , πΉ, Ξ, π§ 0 π , π π π , β ππ ) π = (π π where π β π½ is the set of Y-states; - π π π β π½ Γ Ξ is the set of Z-states so that z = (π½ π¨ , Ξ π¨ ) ; - π π π : π π π Γ Ξ β Q π π represents the unobservable reach; - β ππ π : π π π Γ E β Q π π represents the observation transition; - β ππ 0 0 π π π 1 * + π π π π 3 1 4 3 0 , * + 4 π 2 π 1 π 1 π 2 *π 1 + *π 2 + 5 7 6 π 2 π 1 3,5 , *π 1 + 3,6 , *π 2 + πΌ πΊ πΉ π = π 1 , π 2 , πΉ π = *π, π+ 5/14 X.Yin & S.Lafortune (UMich) WODES 2016 May 2016
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