Resilient control design for distributed cyber-physical systems

• US 9,942,245 B2
• Filed: 06/27/2014
• Issued: 04/10/2018
• Est. Priority Date: 06/27/2014
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Ji, Kun
• Primary Examiner(s): Masinick, Michael D
• Application Number:
  US14/317,321
• Publication Number:
  US 20150378339A1
• Time in Patent Office: 1,383 Days
• CPC Class Codes: G05B 2219/14082 Sample input signal again to verify if signal is correct
• CPC Class Codes: H04L 63/1408 by monitoring network traffic monitoring network traffic per se H04L43/00

Abstract

A distributed cyber-physical system includes physical elements (15-1, 15-2, . . . , 15-n) disposed in a physical space (11). Controllers (13-1, 13-2, . . . , 13-n) are disposed in a cyber space (10). Each of the physical elements (15-1, 15-2, . . . , 15-n) corresponds to a corresponding controller (13-1, 13-2, . . . , 13-n). A cyber infrastructure (12) is disposed in the cyber space (10). The cyber infrastructure (12) manages a connection between the controllers (13-1, 13-2, . . . , 13-n) and the physical elements (15-1, 15-2, . . . , 15-n). Control loops (14) are established via the cyber infrastructure (12). Each of the control loops (14) includes a physical element and a corresponding controller. A resilient control agent (31) is configured to monitor each of the control loops (14), determine when one of the control loops (14) is experiencing an adverse condition, reduce a sampling frequency of the control loops (14) that are not experiencing the adverse condition, and increase a sampling frequency of the control loop (14) that is experiencing the adverse condition.

Claims

1. A method for controlling a distributed cyber-physical system comprising:

monitoring a plurality of control loops, each control loop controlling a corresponding physical element within a distributed cyber-physical system, wherein the monitoring comprises considering at least one performance interdependency between the physical element and at least one cyber element in the distributed cyber-physical system;

determining when one or more of the plurality of control loops experiences an adverse condition;

performing a cost function optimization to maintain a level of quality of service in the distributed cyber-physical system and calculating a sampling frequency for each of the one or more control loops as a function of the optimization;

reducing a sampling frequency of those of the plurality of control loops that are not experiencing the adverse condition; and

increasing a sampling frequency of those of the plurality of control loops that are experiencing the adverse condition.

2. The method of claim 1, wherein each control loop includes the corresponding physical element which is disposed within a physical space and a controller which is disposed in a cyber space.

3. The method of claim 1, wherein each of the plurality of control loops includes:

receiving a set point;

receiving a sensor signal from a sensor disposed in a physical space;

determining an extent to which the received set point aligns with the received sensor signal;

generating an actuator signal based on the determined extent of difference; and

driving an actuator disposed in the physical space based on the generated actuator signal.

4. The method of claim 1, wherein determining when one or more of the plurality of control loops experiences an adverse condition is provided based on prognostic information pertaining to either a cyber space or a physical space.

5. The method of claim 1, wherein reducing the sampling frequency includes reducing a number of times that sensor data is transmitted from a physical element within the distributed cyber-physical system to a corresponding controller disposed in a cyber space, per unit time and increasing sampling frequency includes increasing a number of times that sensor data is transmitted from a physical element within the distributed cyber-physical system to a corresponding controller disposed in a cyber space, per unit time.

6. The method of claim 1, wherein the adverse condition is a malicious computer attack.

7. The method of claim 1, wherein the adverse condition is a malfunction or failure of a physical element.

8. A distributed cyber-physical system comprising:

a plurality of physical elements disposed in a physical space;

a plurality of controllers disposed in a cyber space, wherein each of the plurality of physical elements corresponds to a corresponding controller of the plurality of controllers;

a cyber infrastructure, disposed in the cyber space, managing a connection between the plurality of controllers and the plurality of physical elements, wherein a plurality of control loops are established via the cyber infrastructure, each of the control loops comprising a physical element of the plurality of physical elements and a corresponding controller of the plurality of controllers; and

a resilient control agent configured to;

monitor each of the plurality of control loops, determine when one of the control loops is experiencing an adverse condition,

perform a cost function optimization to maintain a level of quality of service in the distributed cyber-physical system and calculate a sampling frequency for each of the one or more control loops as a function of the optimization;

reduce a sampling frequency of the control loops that are not experiencing the adverse condition, and

increase a sampling frequency of the control loop that is experiencing the adverse condition, wherein the determining of when one of the control loops is experiencing an adverse condition comprises considering at least one performance interdependency between at least one of the plurality of physical elements and at least one cyber element in the distributed cyber-physical.

9. The distributed cyber-physical system of claim 8, wherein the resilient control agent comprises:

an observation agent configured to obtain prognostic information of the cyber space;

a detection and diagnostic agent configured to determine a presence of an adverse condition;

a resilient decision making module configured to determine when and by how much to increase and reduce sampling frequencies; and

an execution agent configured to increase and reduce sampling frequencies in the control loops according to the determinations of the resilient decision making module.

10. The cyber-physical system of claim 8, wherein each of the plurality of controller is configured to:

receive a set point;

receive a sensor signal from a sensor disposed in a physical space;

determine an extent to which the received set point aligns with the received sensor signal;

generate an actuator signal based on the determined extent of difference; and

drive an actuator disposed in the physical space based on the generated actuator signal.

11. The cyber-physical system of claim 8, wherein the resilient control agent is configured to determine when one of the control loops is experiencing an adverse condition based on prognostic information pertaining to either a cyber space or a physical space.

12. The cyber-physical system of claim 8, wherein the resilient control agent is configured to reduce the sampling frequency by reducing a number of times that sensor data is transmitted from a physical element within the distributed cyber-physical system to a corresponding controller disposed in a cyber space, per unit time and increase the sampling frequency by increasing a number of times that sensor data is transmitted from a physical element within the distributed cyber-physical system to a corresponding controller disposed in a cyber space, per unit time.

13. The cyber-physical system of claim 8, wherein the adverse condition is a malicious computer attack.

14. The cyber-physical system of claim 8, wherein the adverse condition is a malfunction or failure of a physical element.

15. A computer system comprising:

a processor; and

a non-transitory, tangible, program storage medium, readable by the computer system, embodying a program of instructions executable by the processor to perform method steps for controlling a distributed cyber-physical system, the method comprising;

monitoring a plurality of control loops, each control loop controlling a corresponding physical element within a distributed cyber-physical system, wherein the monitoring comprises considering at least one performance interdependency between the physical element and at least one cyber element in the distributed cyber-physical system;

determining when one or more of the plurality of control loops experiences an adverse condition;

performing a cost function optimization to maintain a level of quality of service in the distributed cyber-physical system and calculating a sampling frequency for each of the one or more control loops as a function of the optimization;

reducing the sampling frequency of those of the plurality of control loops that are not experiencing the adverse condition; and

increasing the sampling frequency of those of the plurality of control loops that are experiencing the adverse condition.

16. The computer system of claim 15, wherein each control loop includes the corresponding physical element which is disposed within a physical space and a controller which is disposed in a cyber space.

17. The computer system of claim 15, wherein each of the plurality of control loops:

receives a set point;

receives a sensor signal from a sensor disposed in a physical space;

determines an extent to which the received set point aligns with the received sensor signal;

generates an actuator signal based on the determined extent of difference; and

drives an actuator disposed in the physical space based on the generated actuator signal.

18. The computer system of claim 15, wherein determining when one or more of the plurality of control loops experiences an adverse condition is provided based on prognostic information pertaining to either a cyber space or a physical space.

19. The computer system of claim 15, wherein reducing the sampling frequency includes reducing a number of times that sensor data is transmitted from a physical element within the distributed cyber-physical system to a corresponding controller disposed in a cyber space, per unit time and increasing sampling frequency includes increasing a number of times that sensor data is transmitted from a physical element within the distributed cyber-physical system to a corresponding controller disposed in a cyber space, per unit time.

20. The computer system of claim 15, wherein the adverse condition is a malicious computer attack or a malfunction or failure of a physical element.