GB2206430A

GB2206430A - Dimensional control system

Info

Publication number: GB2206430A
Application number: GB08811987A
Authority: GB
Inventors: John James Bradley
Original assignee: TIKO
Current assignee: TIKO
Priority date: 1987-05-20
Filing date: 1988-05-20
Publication date: 1989-01-05
Also published as: IE60701B1; IE871314L; GB8811987D0

Abstract

A microcomputer-based dimensional-control system is provided for use with at least one theodolite forming a three- dimensional coordinate measurement arrangement. The system may be used for (a) establishing the orientation of a local co-ordinate system, (b) establishing parameters of the transformation matrix, (c) entering and storing co-ordinates in the local aystem and (d) transforming the local co-ordinates to the object co-ordinate system. o

Description

DIMENSIONAL CONTROL SYSTEM The present invention relates to a dimensional control system and in particular to measurement systems using twin high-accuracy electronic theodolites with associated computer facilities. Prior art systems are provided with the following alternative computer configuration.

In one type of system computer facilities are provided locally by a relocatable minicomputer. These may be unwieldy and difficult to transport in many industrial environments.

In another type of system computer facilities are provided locally by a hand-held data collection device together with a remote computer installation. The disadvantage here is that the hand-held device is not capable of realtime orientation and transformation computation.

The present invention provides a dimensional control system for use with at least one theodolite, and including means to establish the orientation of a local co-ordinate system, means to establish parameters of the transformation matrix, means to enter and store coordinates in the local system and means to transform said co-ordinates to the object co-ordinate system. Advantageously a reference tooling bar is provided for defining the local co-ordinate system. Multiple theodolites may be linked and defined simultaneously within the same local system. Preferably four options exist for the orientation procedure: - Resection bf theodolites from outside control - Orientation using tooling bar - Entry of known theodolite co-ordinates - Entry of known base length.

Advantageously, the means to establish the parameter of the transformation matrix allows the transformation of coordinates measured in the local system to the object system in real time. The transformation matrix may be computed from a set of control points by an efficient least squares method. A full report on the transformation parameters and computed deviations may be printed.

Preferably, the system includes means for detail measurement which allows the recording, computation and storage of points in the local system and their transformation in real time to the object system. Both local and object co-ordinates may be displayed together with probable error and join distance to previous point.

Advantageously the system includes a comprehensive editing facility means allowing easy correction and re-entry of data.

Preferably, the system includes one or more of the following features: - Means for setting out co-ordinate data in the object system from file with a theodolite autoprompt feature.

- Means for computation of join distances on selected axes.

- Means for computation of least squares line fit and distance of selected point from a line.

- Means for effecting a least squares plane fit and comparison of two planes - Means for effecting least squares circle and sphere fits.

The system accuracy is limited only by the accuracy of the theodolites and the relative geometry of the object and measuring system. For one-second theodolites, the accuracy of the system on a 10 metre baseline and a 10 metre working distance is of the order of 0.10 millimetres.

The system can be provided with a working capacity of a large number of points in the local and object systems.

The invention will hereinafter be more particularly described with reference to the following drawings which illustrate, by way of example only, certain aspects of the invention. In the drawings: Figure 1 is a program schematic of the system; Figure 2 is a flow chart of the program for entering a new job or a new setup; Figure 3 is a flow chart of the program for file handling procedure; Figure 4 is a flow chart of the program for data transfer; Figure 5 is a flow chart of the program for data input; Figure 6 is a flow chart of the orientation section of the data capture program; Figure 7 is a flow chart of the measurement section of the data capture program; Figure 8 is a flow chart of the mean points determination program; Figure 9 is a flow chart of the program for setting out; Figure 10 is a flow chart of the program for file comparison;; Figure 11 is a flow chart of the program for review database; Figure 12 is a flow chart of the program for transformation; wherein Figure 12a defines the steps involved in transformation and figure 12b is a subroutine whereby the points for transformation may be chosen, the scale re-set or the user return to non-transformed data; Figure 13 is a flow chart of the program for rotate axes; Figure 14 is a flow chart of the program for point nomination; Figure 15 is a flow chart of the program for distances; and Figure 16 is a flow chart of a sample program flow.

With general reference to the above drawings, the system basically is a three dimensional co-ordinate measurement system designed for the solution of measurement problems in diverse application areas, including - aircraft manufacture and maintenance - automobile manufacture - offshore platform fabrication - shipbuilding - cement kiln alignment - structural settlement and deformation determination - surface analysis of parabolic antennae - robot guidance and control - alignment of industrial plant machinery - integration into computer aided design and manufacturing systems. (CAD / CAM).

The system consists of electronic theodolites, distance meters, special survey accessories, hand-held computers, computer software and peripherals. Established survey methods of triangulation and optionally polar location are combined with on the spot data processing by the integration of high precision survey instrumentation with micro-computer technology. The system has significant advantages over mechanical co-ordinate measuring machines, orthogonal optical tooling equipment and photogrammetric techniques. However, the system may be combined with optical tooling instruments and techniques advantageously.

Advantages include: - large or small objects, components or structures may be measured.

- high precision instruments ensure the quality and accuracy of the results.

- the equipment is easily moved and rapidly set up.

- freedom of instrument positioning according to circumstance.

- polar and intersection methods may be selected or mixed according to accuracy requirements and prevailing access to an object.

- multiple determinations of points from independent instrument locations for improved accuracy.

- contact-free measurements of inaccessible objects, in hazardous areas or with touch sensitive objects.

- where accuracy requirements may be relaxed, polar measurements from a single theodolite allows for considerable increase in range, maximum equipment productivity and greater speed per point.

- automatic data transfer, processing and storage reduces human error sources and offers significant time savings.

- the system replaces the need for gauges and master patterns.

- facility for on the spot comparison of measured and design dimensions is provided.

The system offers potential benefits in a wide variety of applications and with considerable adaptability and ease of use.

The system is a compact and powerful measurement apparatus geared specifically towards high precision monitoring and industrial measurement. It uses standard, well proven, surveying methods of polar location (optional) and dual theodolite intersections to give quick and precise results.

The system is completely portable. It is not dependent on power supplies as it is totally battery powered. The system runs on a comparatively low cost microcomputer which is a rugged hand-held machine weighing approximately 1 Kilogram. As it is waterproof, dustproof and not easily damaged, it can be used in many working environments which would be totally unsuitable for conventional computers. In spite of its small size it has quite a large capacity, capable of holding many thousand co-ordinated points. As an alternative to cable link, telemetry links may be used in the system for communication between theodolites or between theodolite and total station.

The program is built on a measurement module which acquires measurement data directly from the theodolites.

These are converted into co-ordinates in real time. To do this it uses the flexible Kern ASB communication system or any other theodolite system. This ensures fast and accurate data transmission. In addition the program uses this system to keep the instrument operators informed through displaying messages on the theodolites. The polar location (where available) and theodolite intersection methods may be combined or used separately depending on the prevailing operating conditions and accuracy requirements.

The theodolite intersection method can give a precision in terms of a few microns / thou. The polar location method however is unlikely to give a precision of greater than 1 mm / 1 tenth of an inch, using currently available Electronic Distance Meters. A check on the measured data is provided if dual theodolites are used.

Measurement may be undertaken in metric units (Metres or millimetres) or imperial units (Feet or inches). The program is accurate to 3 decimal places of the selected units. The co-ordinates of the measured points are stored in nominated files holding up to 500 points each.

Measurements are stored in the form of raw data as observed angles, as well as in the form of calculated coordinates.

The program of the system comprises a master program made up of 6 main sections, as shown in Figure 1. These are; 1. New set up 2. File management 3. Data input 4. Data capture 5. Special functions 6. Data transfer The numerals shown in Figure 1 refer to the Figure numbers to which further detail is given on a particular section.

The menu options/functions for the master menu are; Data Input - Keyboard input of co-ordinates and job details.

Measurement - Theodolite Orientation and Measurement.

Special FNS - Standard additional functions.

Data Transfer - Input/Output with external devices.

New Set Up - Resetting for new job or theodolite positions.

File Handling - File Controller Figure 1 also shows the nature of the data or information which can be stored in the database.

With reference to the figures, the master menu options will now be described.

1. New set up This program may be used to set up a new job. Information concerning the job, such as theodolite type, client name etc may be entered. The flow chart for this program is shown in Figure 2.

2. File management This program controls handling of data files, eg file creation, re-naming, information exchange with peripheral computers etc. The program also includes the supervisor function whereby acceptable tolerance values for a job may be pre-set by a person in authority. The menu options/functions for this program, including the supervisor functions are; Find - Locate file in Directory.

Computer comms- Set external Computer Communication Parameters.

Terminal mode - Enter Terminal Mode to check interface.

Create - Create new data file.

Nominate - Nominate current co-ordinate files.

Output - Output selected file to external computer.

Input - Input file from external computer.

Rename - Rename file in directory.

Erase - Erase file from memory.

Code - Access Supervisor section.

SUPERVISOR Dz Tolerance - Indicates comparability of theodolite measurements.

Tolerance for - Check on Standard Error of mean Mean.

Comparison - File Comparison Check Vector Tolerance The flow chart for the file management program is shown in Figure 3.

3. Data-input This program specifies the entry of design control and detail co-ordinates, definition of point sequence and setting of adjustment parameters to account for atmospheric conditions. The pull-down menu for the program comprises; Job Params - Atmospheric conditions & selection of component.

Design Pts - Direct keyboard input of Design Co ordinates.

Control Pts - Direct keyboard input of Control Co-ordinates.

Detail Pts - Direct keyboard input of Detail Co ordinates.

Prompt file - Keyboard input of point name sequence.

Master Menu - Return to Master Menu.

The program flow chart of this program is shown in Figure 5.

4. Data capture This program comprises two steps, orientation and measurement. Orientation involves the determination of the spatial relationship between two theodolites. This defines the scale and orientation of the measurement axis system. It may be determined by a number of methods, the most precise being to observe two points, a known distance apart, and thereby deduce the spatial relationship. The pull-down menu for the program comprises the following options; Tooling Bar - Scale from observations to Calibration Bar.

Approx Base - Approximate Scale input directly.

Polars Only - Angles and Distances from a single Total Station.

Known Base - Distance between theodolites input directly.

Known Coords - Co-ordinates of theodolite positions input.

Master Menu - Return to Master Menu.

The orientation flow chart is shown in Figure 6.

Orientation may also be carried out by computing the angles of two theodolites to one another by reference to control points. This is useful in cases where the line of sight between the instruments is obscured. Following the orientation determination, point measurement commences, each point being observed by two theodolites simultaneously. The system then downloads the angles automatically, applies a simple check to see if both theodolites are pointing to the same place, and computes the co-ordinates. The next point may now be observed.

The pull-down menu for the program comprises the following options; Intersections - Point Co-ordination using dual theodolite intersections.

Angles & Dist - Point Co-ordination using angles and distance.

Site Analysis - Accesses appropriate analysis functions.

Master Menu - Return to Master Menu.

Figure 7 depicts the measurement program flow-chart.

5. Special functions This section of the program comprises five sub-sections, as follows; A. Transform B. Review database C. Mean points D. File comparison E. Setting out The pull-down menu for the special functions comprises the following options; Transform - Transformation computation and application.

Review Data - Review Database contents.

Mean Points - Computation of mean of points bearing same names.

Compare Files - Comparison of Design and Detail Files.

Setting Out - Computation of required data from Design Co-ords.

Master Menu - Return to Master Menu.

A. Transform. All the observed points are co-ordinated initially in the local co-ordinate system, based on the positions of the two theodolites. To change these to coordinates in a system based on the object observed a three dimensional transformation must be computed. A further sub-menu exists for the transformation option, as follows; Available prior to Transformation Parameter Computation.

Object Scale - Computation of parameters using control points.

Local Scale - As above but not computing a scale factor.

Input Params - Direct Input of Transformation Parameters.

Rotate Axes - Computation of Parameters from observed points.

Only Available after parameters computed.

Transf'm File - Transform selected points from file.

Scale Change - Change scale of object, for output only.

Reject - Revert to local system.

Master Menu - Return to Master Menu.

Two methods may be used for the transformation; The first method is to observe points with known object co-ordinates. At least three points with known object coordinates are observed. The local co-ordinates thereby computed are paired off with the relevant object coordinates. The transformation parameters that fit the two sets of co-ordinates together with the least discrepancy are computed by the system in a matter of seconds. These consist of three shifts, three rotations and an optional scale factor. The residuals are displayed. Interactive editing of the points used may take place, permitting the removal of any erroneous data revealed by the residuals. The flow chart for this section of the program is shown in Figure 12.In Figure 12a, a transformation is carried out, while in Figure 12b a subroutine is provided whereby the particular points for transformation may be chosen, the scale may be reset or the user may return to the local system.

The second method is to define the object axes. A number of points lying on an axis plane are observed. The equation of these points is computed in the local coordinate system and the residuals displayed. If the object is not vertical a second axis plane or object axis must then be defined. The option is then given to shift the origin of the system to a nominated point. Following this the relevant transformation parameters to bring the defined planes into coincidence with the axis planes are computed. The flow chart for this program is shown in Figure 13.

B. Review database This program permits the user to review any information contained in the computer database, including job parameters, control, design or measured angles or co-ordinates, transformation residuals etc. The pull-down menu comprises the following options; Detail File - Review Co-ordinates of Measured points.

Design File - Review Design Co-ordinates.

Control File - Review Control Co-ordinates.

Residuals - Review Transformation residuals.

Prompt File - Review Prompt File.

Parameters - Review Job and Transformation Parameters.

Orientation - Review Orientation Results.

Master Menu - Return to Master Menu.

Figure 11 details the flow chart for this program.

C. Mean points This module enhances the precision of the measurements through enabling the user to measure a point a number of times and then compute the mean. A single point may also be observed from two different set-ups and a mean computed. The standard error is retained for later reference. If it is outside a pre-set tolerance, interactive editing is permitted. Figure 8 depicts the flow chart for this program.

D. File comparison This module enables the user to compare points from two different files resident in the same co-ordinate system. (If not the transformation facility may be used). It is a very useful function for monitoring the deformation of an object or checking deviations from a standard. The discrepancies between the points are displayed and checked against a pre-set tolerance, enabling simple trapping of significant deviations. The flow chart for the file comparison function is shown in Figure 10.

E. Setting out Points from a nominated file may be set out using angles and distances computed by the system and displayed both on the computer screen and the theodolite display. This can be particularly useful in conjunction with the geometric analysis modules and the distances module (see below). Figure 9 shows the flow chart for the setting out program.

Two additional modules exist for use with other menu options and in particular for use with the special functions options. These are (a) Point Nomination and (b) Distances.

(a) Point Nomination This facility permits all points to be reviewed and particular points to be flagged or nominated for special treatment, eg for transformation using only nominated points, for data input, for data capture or distances. The following options exist in the pull-down menu for this feature; Input/Select - Accesses Data Input for selection of points.

Observe - Next points measured automatically nominated.

Compute - Activate Relevant Computations.

Printout - Printout all nominated points.

Cancel - Set Nominated points to 0.

Figure 14 depicts the flow-chart relevant to this option.

(b) Distances The distance between any two nominated points in each axis direction, in any axis plane and in three dimensions may be computed. In addition the vector constants are displayed and comments may be recorded. This can be very useful for checking the accuracy of construction, especially for critical distances. The system can measure points to an accuracy of a number of microns. However, distances of an accuracy less than 0.05mm are unlikely unless a special effort is made to ensure that the points being measured are very precisely and clearly targeted. The flow chart for the distances function is shown in Figure 15.

6. Data transfer The system has a well developed file handling section which enables data to be held in a well ordered manner.

Up to 5000 points may be held on the computer at any time.

In addition the data transfer section has been extensively developed, permitting the use of a portable battery powered disk drive in the workplace to transfer data. Coordinates may also be transferred from the system to a larger computer for more detailed analysis and/or storage.

To facilitate this communication parameters are redefinable, and a terminal capacity is included.

The system may be linked quite easily with other computers and computer systems, which it complements, and popular CAD/CAM systems. This is simplified by the standard type file handling routines, combined with the user definable communication parameters. Data may be stored on standard 3 1/2 inch floppy disks using a battery run disk drive.

This may then be stored for later reference or transferred to another embodiment of the present system. Any part of the database may be reviewed quickly and easily from within the program. Printouts may be taken as desired.

The pull-down menu for the data transfer function comprises the following options; Input - Input data from external Disk Drive.

Output - Output data to Printer or Disk Drive.

Parameters - Set communication parameters for selected device.

Other - Set Clock, Format Disk, Terminal Capability.

The flow chart for the program is shown in Figure 4.

The system also includes a site analysis menu the contents of which include: Distances - Computation of Distances between nominated points Lines - Least Square Linear Regression Planes - Least Square Plane fitting Circle - Least Square Circle fitting Measurement - Return to Measurement Menu.

This menu may be expanded to include special options developed for a particular client.

Also included is a measurement functions menu the contents of which include: Target Bar - For taking measurements using a Remote Target Bar.

Set-Up Check - For taking measurements to monitor set-up Measurement - Return to Measurement Menu.

The specific description has concentrated on the use of two theodolites, however the system may be operated also using only one theodolite. The theodolite is focused on control points from one known point and then focused at the same control points from a second known point. In this way distances and angles may be computed.

Claims

CLAIMS:

1. A dimensional control system for use with at least one theodolite, and including means to establish the orientation of a local co-ordinate system, means to establish parameters of the transformation matrix, means to enter and store co-ordinates in the local system and means to transform said co-ordinates to the object coordinate system.

2. A dimensional control system is claimed in Claim 1 in which a reference tooling bar is provided for defining the local co-ordinate system and multiple theodolites may be linked and defined simultaneously within the same local system.

3. A dimensional control system is claimed in claim 2 in which four options exist for the orientation procedure, namely means for the resection of theodolites from outside control; means for orientation using said tooling bar; means for entry of known theodolite co-ordinates; and means for entry of known base length.

4. A dimensional control system as claimed in any one of the preceding claims in which the means to establish the parameter of the transformation matrix allows the transformation of co-ordinates measured in the local system to the object system in real time.

5. A dimensional control system as claimed in any one of the preceding claims in which the transformation matrix is computed from a set of control points by an efficient least squares method.

6. A dimensional control system as claimed in any one of the preceding claims in which a full report on the transformation parameters and computed deviations is printed.

7. A dimensional control system as claimed in any one of the preceding claims in which the system includes means for detail measurement which allows the recording, computation and storage of points in the local system and their transformation in real time to the object system and in which both local and object co-ordinates are displayed together with probable error and join distance to previous point.

8. A dimensional control system as claimed in any one of the preceding claims in which the system includes a comprehensive editing facility means allowing easy correction and re-entry of data.

9. A dimensional control system as claimed in any one of the preceding claims in which the system includes one or more of the following features: - Means for setting out co-ordinate data in the object system from file with a theodolite autoprompt feature.

- Means for computation of join distances on selected axes.

10. A dimensional control system as claimed in any of the preceding claims which includes means for performing an axis rotation and for calculating transformation parameters to bring geometric shapes into coincidence.

11. A dimensional contro system which includes means for comparing two different sets of data resident in the same co-ordinate system to measure deformation.

12. A dimensional control system substantially as herein described with reference to and as shown in the accompanying drawings.