WO2014102700A1

WO2014102700A1 - A method for performing impact analysis of change in a control application and a system therefor

Info

Publication number: WO2014102700A1
Application number: PCT/IB2013/061265
Authority: WO
Inventors: Alpana DUBEY; Aparajithan V; Raoul JETLEY
Original assignee: Abb Global Industries And Services Limited
Priority date: 2012-12-24
Filing date: 2013-12-23
Publication date: 2014-07-03

Abstract

The present invention is a method and a system for automatically performing impact analysis of change in one or more control parameters in a control application. The system comprises a computing unit, a slicing unit and a means of representation. The computing unit computes Program Dependence Graph (PDG) encompassing various data-flow and control dependencies of various segments on one or more control parameters in the control application. The slicing unit slices the control application which are impacted due to change in one or more control parameters into segments by program slicing technique. The means of representation provides for representation of impact caused at various levels due to change in one or more control parameters of a control application.

Description

A METHOD FOR PERFORMING IMPACT ANALYSIS OF CHANGE IN A CONTROL APPLICATION AND A SYSTEM THEREFOR

FIELD OF INVENTION

This invention for automated impact analysis is applicable to the field of process control and process automation applications and in particular relates to control applications where change in one or more control parameters occurs.

BACKGROUND

A control application manages, directs or regulates the behavior of other applications and control systems in the process control environment. The behavior of control application is affected by change in parameters within such control application. Such parameters which control the control application are known as control parameters. For instance, local variables, global variables, function blocks, functions or the like act as control parameters in a control application.

Segments of a control application are interlinked by control parameters in the control application. Thus various segments of the control application exhibit dependencies on one or more control parameters in the control application. Hence, change in one or more control parameters in control application has impact on various segments of control application. The process of determining various segments of control application that are impacted due to change in one or more control parameters in such control application is known as "impact analysis" or "change analysis".

The field of process control and automation involves application development, testing and maintenance phases. In these phases, one or more control parameters of a control application require to be changed due to a change request arising from control engineer. For instance, at the stage of application development, a change made in one or more control parameters has impact on various segments of control application that have dependencies on such one or more control parameters in control application. Similarly, at the maintenance stage, a change in one or more control parameters in control application has impact on the behaviour of other control system hardware in the same control environment. In such cases, impact analysis is crucial in order to know the impact of such change due to one or more control parameters on various segments of control application prior to bringing such change in actual control application. Presently, the computation of the dependencies of various segments in the control application on control parameters and the impact caused by change in such control parameters are being performed manually. The impact analysis performed manually is time consuming, tedious and less efficient in determining all segments of control application which have been impacted. In testing phase, any change in one or more control parameters in a control application requires all test cases to be run irrespective of whether such test cases are impacted or not. This results in reduced efficiency because of unnecessary testing of those segments which have had no impact by that particular change in control parameters. For efficient testing, it is necessary to run only those test cases which are impacted by the change in control parameter in control application.

Presently, program slicing technique is applied in general purpose applications for separating segments of such applications that are impacted due to change in parameters; but not applied in control applications. Control application, used to control, monitor and regulate the behavior of control systems, uses logic device design, which includes but is not limited to Instruction list (IL), Ladder Diagram (LD), Functional Block Diagram (FBD), Structured Text (ST) and Sequential Function Chart (SFC). Any change in the parameters of the control applications impacts the behaviour of the components of the control system. Such unforeseen changes in the parameters of the control applications render the control system unstable or less reliable. Hence, it is required to perform impact analysis of change in one or more control parameters, in a control application. Currently, impact analysis is performed manually wherein it is required to analyze the impact caused due to change in parameters of that particular control application or on other such control applications or part thereof. This approach is quite cumbersome, inefficient, less cost effective and error prone. Therefore there is a need for an invention to provide a solution for performing impact analysis automatically that improves efficiency, cost effectiveness and reduces likelihood of errors.

This invention is for automatically performing impact analysis of change in one or more control parameters in a control application and provides representation of various segments of control application which are impacted due to change in such control parameters. SUMMARY OF THE INVENTION

This invention for performing impact analysis is applicable to the field of process control and process automation applications and in particular relates to control applications where a change in one or more control parameters occurs. This invention is a method and a system for automatically performing impact analysis of change in one or more control parameters in a control application. It not only involves automatic computation of various dependencies of segments of a control application on one or more control parameters, but also provides representation of various segments that are impacted due to change in such control parameters.

This method eliminates tedious effort of manually performing the impact caused due to change in one or more control parameters and risk of missing out any dependencies of various segments of control application on one or more control parameters. It helps in reducing risk of impact caused by ripples and unanticipated modifications in one or more control parameters in control application.

The present invention operates in batch mode and in on-the-fly mode. The method involves computation of Program Dependence Graph (PDG) encompassing various control and data dependencies of segments of control application on control parameters. Program slicing technique computes slicing criterion based on the computed PDG and slices segments of control application that are impacted by change in one or more control parameters in control application. Further, it provides representation of segments that are impacted due to change in one or more control parameters in control application.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the following description of the preferred embodiments of the invention read in conjunction with the attached drawings, in which:

Fig. 1 shows the schematic representation of architecture of a system for performing impact analysis of change in one or more control parameters in a control application.

Fig. 2 shows the pictorial representation of segments of a control application involving an SFC and two FBDs, as an exemplary embodiment of the invention. Fig. 3 shows the representation of segments of the control application, and the highlighted segments depicting the segments that are impacted due to change in control parameter (cp) at segment S 1 in the control application.

The drawings are merely representative and are not intended to limit the scope of the appended claims.

DETAILED DESCRIPTION

The present invention is a method and system for automatically performing impact analysis of change in one or more control parameters in control application and giving a visual representation of various segments of control application that are impacted due to such change in one or more control parameters in control application. The invention is described herein after with reference to the accompanying drawings through non-exhaustive exemplary embodiment.

The present invention performs impact due to change in one or more control parameters of a control application and in particular to a control application. The control application includes but not limited to Ladder Design (LD), Function Block Diagram (FBD), Structured Text (ST), Function Block, Instruction List (IL), Sequential Function Chart (SFC) or a combination of these.

A schematic representation of architecture of a system for performing impact analysis of change in one or more control parameters in a control application is illustrated in Fig. 1. A control engineer 1 makes change 3 in one or more control parameters in a control application. A system 2 for performing impact analysis of such change in one or more control parameters in control application comprises of: a computing unit 4; a slicing unit 5 and a means of representation 6. The slicing unit 5 includes selecting unit. After changing one or more control parameters in a control application, computing unit 4 computes Program Dependence Graph (PDG) encompassing control and data dependencies of various segments of a control application on such one or more control parameters in control application. Next, the selecting unit selects the segments of the control application that are impacted by such change in one or more control parameters in control application. The slicing unit slices the control apphcationsthat is impacted due to change in one or more control parameters to obtain segments of the control application. The selecting and slicing to obtain segments of the control application that are impacted due to change in one or more parameters is performed by static program slicing technique based on already computed PDG. Further, a means of representation 6 provides a representation of impact at various levels caused due to change in one or more control parameters in control application. If impact due to such change is undesirable, then control application reverts to previous state of control application existing before such change was made. Otherwise, the control application remains unchanged after such changes in one or more control parameters in control application.

PDG encompasses control and data dependencies of various segments of a control application on one or more control parameters in control applications. PDG is derived from Control Flow Graph (CFG). CFG represents control flow order of segments in a control application. In computing CFG, control application defined in LD, ST and IL is converted into equivalent FBD blocks. CFG is obtained by generating the corresponding Abstract Syntax tree (AST) from the FBD equivalent blocks. CFG is created by traversing all possible paths in AST from a specific segment of the control application. But, the control application defined in SFC cannot be converted to its equivalent FBD and hence it is retained in the same form without conversion. SFCs inherently contain control flow information, which itself serves as CFG.

Control dependencies and data dependencies of segments in a control application on one or more control parameters due to change in such one or more control parameters in control application are defined by Control Dependence Graph (CDG) and Data-flow Dependence Graph (DDG) respectively. CDG is a combination of all control dependent edges in Control Flow Graph (CFG); whereas DDG is a combination of all data dependence edges between nodes of CFG. CDG and DDG are derived from Control Flow Graph (CFG) of a control application. DDG is computed by tracing relationships between all control parameters in a control application. There is data-flow dependence between segments of control application when one or more control parameters defined in one segment are used by another segment. A data-flow dependence edge between two nodes implies that the computation performed at a node pointed by an edge directly depends on value computed at another node. This means that a pointed node uses a control parameter defined at previous node. A control dependence edge between two nodes implies that the result of a conditional segment in a control application at a node pointed by an edge decides whether to execute another node or not. These CDG and DDG combine to constitute PDG. PDG consists of nodes and edges. Each of the segments of a control application determines nodes in PDG. The flow between these segments in a control application determines edges of PDG. The edges incident to a node in a PDG represent both data values on which the node's operations depend and control conditions on which execution of segments of control application depend. Edges in a PDG are constituted by Data-flow dependence edges and Control dependence edges. Thus, the computed PDG encompasses control and data dependencies of various segments of control application on one or more control parameters in the control application.

The impact of a change in the control parameter is computed using the static program slicing technique. The behavior of the original control application is preserved using the slicing technique because it separately slices the segment of the control application that is impacted due to such change in control parameter in control application. The program slicing technique is defined with respect to a slicing criterion <p, V>, where p is a specified segment in a control application and V defines the set of control parameters that are changed in a control application. Slicing of impacted segments is achieved by identifying segments of control application that are influenced by the given slicing criterion. Segments of a control application which are influenced by a slicing criterion constitute the forward slice. The present invention uses forward slicing for impact analysis of a change in a control application. A forward slice is computed based on the computed PDG obtained for a control application. Such forward slice is computed by traversing through nodes of PDG starting from the segment of control application specified by the slicing criteria. All the nodes that can be reached from that specified segment of the control application are included in the slice. Then the computed forward slice has those segments of control application that are impacted due to change in one or more control parameters in a control application.

Fig. 2 shows the pictorial representation of segments of a control application involving an SFC and two FBDs. This is described only as an exemplary embodiment of the invention. This control application consists of an SFC comprising of segments 21 through 27, including conditional segments 28 through 34. Segment 25 is interlinked to FBD1 35. Similarly, segment 23 is interlinked to FBD2 36. FBD1 35 contains logic devices LD1, LD2 and LD3. FBD1 35 contains logic devices LD4, LD5, LD6 and LD7. CFG has control flow order of various segments, including function blocks of a control application. When control parameter (cp) at segment SI 21 is changed, then the forward slice is computed with the forward slice criterion as <S 1 , cp>. On analysis of the impact caused due to change in the control parameter, FBD2 36 is included due to the data dependence of FBD2 36 on the control parameter. Segment S3 23 is also included in the forward slice due to the interlinking relationship of control parameter between FBD2 36 and segment S3 23. Hence, there is an impact on segments FBD2 36 and S3 23 due to the change in the control parameter. Similarly, due to data dependencies on the control parameter, the segments of control application included in the forward slice are SI 21, S3 23, S5 25, S6 26, S2 22 and two FBDs 35 and 36; and the conditional segment Tr6 31 is included in the same forward slice due to control dependence on control parameter.

Fig. 3 shows the representation of segments of control application. The highlighted parts are segments of control application that are impacted due to change corresponding to forward slicing criterion <S1, cp>. A change in the control parameter at specific segment SI 21 highlights segments S3 23, S5 25, S6 26 and S2 22 and conditional segment Tr6 31 and the two FBDs 35 and 36, that are impacted due to change in the control parameter in the control application.

A means for representation 6 provides representation of impact caused at various levels due to change in one or more control parameters in control application. The means of representation includes Graphical User interface, Human Machine Interface, textual highlighting display or any such similar means of representation that is capable of providing representation of impact analysis of change in one or more control parameters in control application. The representation of impact analysis includes graphical representation, highlighting of segments in control application by textual means, block level representation, logic device level representation or such other similar representations.

The present invention is capable of being operated in two modes namely the On-the-fly mode and Batch mode. On-the-fly mode applies in scenarios where there is single change in control parameter in control application. In this mode, impact analysis is performed for each change made. While the Batch mode applies in scenarios when there is series of changes in control parameters in control application. Here, the impact analysis is performed for a series of changes made in a single edit session. A series of changes [e_{1 ;} e₂, e₃, , e_n,] is performed on control parameters in control application, where each e; represents such change in control parameters. This results in corresponding control application version series [v_{1 ;} v₂, v_n ] after change is performed in control parameters in control application. For each change e; in control parameters in the control application, the computed impact analysis series is stored as [r_{1 ;} r₂, r_n]. The invention provides the user with the final impact as r_n for a series of changes performed on control parameters in control application.

Only certain features of the invention have been specifically illustrated and described herein, and many modifications and changes will occur to those skilled in the art. The invention is not restricted by the preferred embodiment described herein in the description. It is to be noted that the invention is explained by way of exemplary embodiment and is neither exhaustive nor limiting. Certain aspects of the invention that not been elaborated herein in the description are well understood by one skilled in the art. Also, the terms relating to singular form used herein in the description also include its plurality and vice versa, wherever applicable. Any relevant modification or variation, which is not described specifically in the specification are in fact to be construed of being well within the scope of the invention. The appended claims are intended to cover all such modifications and changes which fall within the spirit of the invention.

Thus, it will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.

Claims

WE CLAIM:

1. A method for performing impact analysis of a change in one or more control parameters in a control application, wherein the said method comprising the steps of: computing Program Dependence Graph (PDG) encompassing various control and data dependencies of various segments of the said control application on the said one or more control parameters in the said control application; and slicing the said control application that is impacted due to change in said one or more control parameters in the said control application, by program slicing technique based on the said computed PDG, to obtain one or more segments of the said control application.

2. The method as claimed in claim 1, wherein the said control application includes Ladder Design (LD), Function Block Diagram (FBD), Structured Text (ST), Instruction List (IL), Function Block, Sequential Function Chart (SFC) or a combination thereof.

3. The method as claimed in claim 1, wherein the said PDG is a combination of Control Dependence Graph (CDG) and Data-flow Dependence Graph (DDG) encompassing control dependencies and data-flow dependencies of various segments of the said control application on the said one or more control parameters in the said control application respectively.

4. The method as claimed in claim 1 , wherein the said slicing includes selecting one or more segments of the said control application that are impacted due to change in said one or more control parameters in the said control application by program slicing technique based on the said computed PDG.

5. The method as claimed in claim 1, wherein the said program slicing technique is a static slicing technique.

6. The method as claimed in claim 1 , wherein the said method operates in batch mode or in on-the-fly mode.

7. The method as claimed in claim 1, wherein the said method further provides representation of impact at various levels due to change in the said one or more control parameters in the said control application.

8. A system for performing impact analysis of change in one or more control parameters in a control application, wherein the said system comprises:

a computing unit for computing Program Dependence Graph (PDG) encompassing various control and data-flow dependencies of various segments of the said control application on the said one or more control parameters in the said control application; and

a slicing unit for slicing the said control application that is impacted due to change in said one or more control parameters in the said control application, by program slicing technique based on the said computed PDG to obtain one or more segments of the said control application.

9. The system as claimed in claim 8, wherein the said slicing unit includes selecting unit for selecting one or more segments of the said control application that are impacted due to change in said one or more control parameters in the said control application by program slicing technique based on the said computed PDG.

10. The system as claimed in claim 8, wherein the said system further comprises a suitable means of representation for representing impact at various levels due to change in the said one or more control parameters in the said control application.