GB2132796A

GB2132796A - Data logging system

Info

Publication number: GB2132796A
Application number: GB08233680A
Authority: GB
Inventors: Stephen Leofric Rhodes; David Charles Hawkins
Original assignee: Decca Ltd
Current assignee: Decca Ltd
Priority date: 1982-11-25
Filing date: 1982-11-25
Publication date: 1984-07-11

Abstract

A data logging system in which there are two data buses 3,3a each having one of a pair of units coupled to it. One unit of the pair is committed to a particular task and the other unit of the pair is non-committed and works asynchronously with the committed unit. For each committed unit there is a verification means which in the event of malfunctioning of the committed unit reassigns the tasks performed by that committed unit to the corresponding non-committed unit. The units may be tape recorders 5,5a, data stores 6,6a, computers 7,7a and displays 8,8a. <IMAGE>

Description

SPECIFICATION Data logging system This invention relates to data logging systems and particularly to a data logging system intended for use in conjunction with oil drilling equipment.

Data logging is a well-known auxiliary operation associated with drilling for oil and in other contexts.

It is customary to provide in data logging equipment an appropriate interface for the reception of data, a data bus and various operational units connected to the data bus. These operational units usually comprise data recording and playback devices, a data processor and a display. In the particular circumstances of oil derricks used on land, the data logging equipment is usually provided in a logging truck which can be used for as long as it is necessary or desirable at a particular site and then driven to another site.

It is usually necessary to provide continuous logging of the operations which the logging system is required to monitor. However, logging equipment is, as any other electrical equipment, liable to failure and it is accordingly desirable to provide a logging system which can continue to function adequately even in the event of failure of operational units within the system.

It is known in various circumstances, where data is being processed and component failure is possible or likely, to provide redundancy in the organisation of the operational unit of the system. This is normally provided by the duplication or multiplication of any particular unit in which failure is possible or likely and arranging that the units which are duplicated or multiplied perform simultaneously the same task or routine. Accordingly even if a particular unit fails, the overall operation of the system can continue.

There are however several disadvantages associated with the use of systems which include redundancy. One is that a system of this nature is inherently inefficient, to the extent that any particular unit is duplicated and the duplicated units perform the same task. Moreover, if duplicated units are connected to a common data bus they may individually perform adequately but become unsynchronised and in practice a redundant system requires a good deal of complexity to prevent malfunction arising from a synchronism of corresponding, redundant units.

The present invention is concerned with a data logging system which is organised partly in terms of hardware but partly in terms of software so as to provide the benefit of redundancy without some of the attendant disadvantages such as lack of efficiency. One intention behind the present invention is to provide a data logging system which in its preferred form can provide continuous logging or at least greatly extended effective operational life notwithstanding component failure than an ordinary logging system having no redundancy.

In one preferred form of the invention a data logging system comprises a data input, at least two data buses and at least two interface units for coupling data from the input to a respective one of the data buses. To each data bus is connected a multiplicity of data-handling units, including at least one recording unit, at least one computer unit and preferably including a display. For each unit thus coupled to one data bus there is a corresponding unit coupled to the other data bus. For reasons which will be apparent hereafter the data buses may be linked in a manner which will be more particularly described hereinafter.

An important feature of the present invention is the organisation of the operation of the various units. It is preferred that for each unit which is duplicated (one for each data bus) one is initially committed to performing a task directly associated with the data logging performed by the system. The other corresponding unit is not thus committed and preferably works asynchronously therewith, for example on low priority testing routines or such like.

Another important feature of the invention is that at least each of the initially committed units be subject to continuous verification by an appropriate verifying means.This may be implemented in any suitable manner having regard to the nature of the particular unit. For example, if the unit is a data recorder, data recorded by the recorder may be immediately replayed for comprison with the input data either fully or by means of parity checks, so as to provide verification that the particular unit is working correctly. The extent to which verification is provided is partly a matter of choice and partly a matter determined by the particular units used in the system.

A further important feature of the invention is that when the verification means or verification routine associated with a particular committed unit indicates that the respective non-committed unit is not functioning correctly, the system reassigns the respective non-committed unit to perform the tasks or routines formally performed by the respective committed unit. It may be desirable for this purpose that at any given time a pair of units, one initially committed and the other not, operated asynchronously, that is to say that one should be quiescent while the other is in operation and vice versa.

A further important feature of the present invention is that the two halves of a system should operate on a mirror image data base so that in any event there is no loss of data during, for example, the reassignment of non-committed units.

A more particular example of the present invention is illustrated in the accompanying drawing of which the single Figure illustrates schematically a data logging system.

In the example shown in the drawing, the data logging system has a data input 1 which feeds raw input data to two similar interfaces 2 and 2a. Each interface feeds a respective one of the data buses 3, 3a.

Connected to the data bus 3a are operational units 5 to 8, constituted in this example by a tape recorder 5, a data store 6, which may be some suitable form of high speed random access store, a data processor such as a computer 7 and a display 8.

Each operational unit 5 to 8 connected to the data bus 3 is matched by a similar unit 5a to 8a respectively.

There may be a link 4 (shown in ghost) between the data buses so as to enable, for example, verification information to pass from one data bus to another. Each computer may include control functions for the various other operational units connected to the respective data bus as well as routines for the processing of data originally supplied to the recorder 5 and transferred as necessary to the store 6.

In the normal operation of the system, the units 6 to 8 are committed in a sense that they provide the essential processing of data stored in recorder 5 so as to provide, usually, continuous monitoring of the raw input data and continuous display of the conditions represented by the raw input data. The data base provided by the recorders 5 and 5a are mirrored so that there is never any loss of raw input data. The units 6a to 8a are initially not committed to the ordinary processing of the data to provide the required display but instead are assigned to low level checking tasks.

It is important for the operation of the system that any particular pair of units, such as 6 and 6a work at different times, that is to say one is quiescent while the other is operational and vice versa.

Each of the aforementioned units has verification means, which may be constituted by hardware or at least partially by software according to preference and/or the nature of the unit. If a failure in one of the committed units should occur and the failure is detected by means of the verification means, the corresponding non-committed unit is reassigned to the performance not only of its previous task but also the performance of the tasks previously performed by the committed and now inoperative or faulty committed units.

CLAIMS: (Filed on 24/11/83) 1. A data logging system comprising a data input, at least two data buses and at least two interface units for coupling data from the input to a respective one of the data buses, a multiplicity of data handling units connected to each data bus, the said units including at least one recording unit and at least one computer unit, there being provided for each unit thus coupled to one data bus a corresponding unit coupled to the other data bus, one each of the pair of units thus correspondingly coupled being committed to performing a task directly associated with the data logging performed by the system and the other unit being arranged to work asynchronously therewith, there being provided verification means associated with each committed unit and arranged so that if the respective committed unit is not functioning, the respective non-committed unit is reassigned to perform the tasks or routines previously performed by the respective committed unit.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

bus 3 is matched by a similar unit 5a to 8a respectively.

There may be a link 4 (shown in ghost) between the data buses so as to enable, for example, verification information to pass from one data bus to another. Each computer may include control functions for the various other operational units connected to the respective data bus as well as routines for the processing of data originally supplied to the recorder 5 and transferred as necessary to the store 6.

In the normal operation of the system, the units 6 to 8 are committed in a sense that they provide the essential processing of data stored in recorder 5 so as to provide, usually, continuous monitoring of the raw input data and continuous display of the conditions represented by the raw input data. The data base provided by the recorders 5 and 5a are mirrored so that there is never any loss of raw input data. The units 6a to 8a are initially not committed to the ordinary processing of the data to provide the required display but instead are assigned to low level checking tasks.

It is important for the operation of the system that any particular pair of units, such as 6 and 6a work at different times, that is to say one is quiescent while the other is operational and vice versa.

Each of the aforementioned units has verification means, which may be constituted by hardware or at least partially by software according to preference and/or the nature of the unit. If a failure in one of the committed units should occur and the failure is detected by means of the verification means, the corresponding non-committed unit is reassigned to the performance not only of its previous task but also the performance of the tasks previously performed by the committed and now inoperative or faulty committed units.

CLAIMS: (Filed on 24/11/83)

1. A data logging system comprising a data input, at least two data buses and at least two interface units for coupling data from the input to a respective one of the data buses, a multiplicity of data handling units connected to each data bus, the said units including at least one recording unit and at least one computer unit, there being provided for each unit thus coupled to one data bus a corresponding unit coupled to the other data bus, one each of the pair of units thus correspondingly coupled being committed to performing a task directly associated with the data logging performed by the system and the other unit being arranged to work asynchronously therewith, there being provided verification means associated with each committed unit and arranged so that if the respective committed unit is not functioning, the respective non-committed unit is reassigned to perform the tasks or routines previously performed by the respective committed unit.