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The technical characteristics, advantages and applications of an automated optoelectronic measuring systems designed by Optoelectronic Measuring System Laboratory of Ufa State Aviation University are presented in this paper. The automated optoelectronic system "MARS" is designed for remote non-contact measurement of movement parameters: positions, linear and angular velocity as well as acceleration of fast objects. The systems represent a new computer-aided technologies of testing. The measuring systems was used for testing aerospace objects and spacecrafts for flying on Mars according International program. The systems can be also applied for research and development in aircraft building industry.
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The further development of science and engineering for study of outer space and remote planets, for example, Mars requires improvement of aerospace flying vehicle. In turn, for this purpose it is required to create new systems for testing and improvement of aerospace flying vehicle. The systems for measurement of movement parameters of high-speed aerospace objects are necessary to solve this problem.
Besides, during bench tests of a number of objects and materials subjected to shock exposure, it is necessary to have devices allowing determining of an object movement trajectory, its linear and angular speeds in three-dimensional space with high accuracy and reliability.
Thus, a knowledge level of expert determines reliability of used methods. And process of reconstruction takes long time and is very labour intensive.
Proceeding from above-stated, the urgency of a problem of reliable non-contact determination of object positions and speeds of objects in space during bench tests is clear.
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During test it is required to obtain linear and angular speed of aerospace object ( Fig. I ).
On fig. I one can see trajectory of aerospace object motion and the following speed vectors: linear Vz, angular Wx, around axis X, angular Wy, around axis Y.
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Figure 1. The trajectory of object movement in three-dimensional co-ordinates
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The following requirements are specified to measurements:
  1) high speed of response in connection with high linear speed and accelerations of object (up to 100 m/c) on acceleration distant ( 0,1 - 0,5 м ) with high loads (up to 1000 g and more);
  2) small measuring errors ( less than 0.5 %). Thus, it is necessary to bear in mind that measured objects have the small dimensions and weight (from tens kg);
  3) the object is exposed to high-frequency mechanical and acoustic vibrations.
During such test of fast moving object special rapid shootings of film is made. The rapid movie must be doing simultaneous from 2 - 3 angular directions. But those methods of measuring are not precise, demand chemical processing of film and photo materials. They can be evaluated only visually and demand much time.
To solve the above-stated problem it is reasonable to carry out optoelectronic measuring methods with electronic processing of signal, input and registration in computer.
Two coordinate systems of object and measuring systems are introduced: PRQ и XУZ. XУZ system is specified by orths, arranged along katets of triangle, which is formed by measuring systems ( position of measuring rulers ) and axis Z. PRQ system is formed by mutually perpendicular vectors P, R и Q.
The function measuring system is defined by the formula, describing the generation of vector array of angular speed in co-ordinate system XYZ:
    W[i,XYZ,1] =Wx = Wp*Px + Wr*Rx + Wq* Qx,
    W[i,xyz,2] = Wy =Wp*Py + Wr*Ry + Wq* Qy,    (1)
    W[i,xyz,3] = Wz = Wp*Pz + Wr*Rz + Wq* Qz,
where:
Wx, Wy, Wz - projection of angular speed vector W on axis X, Y and Z respectively (system XYZ );
Wp, Wr, Wq - projection of angular speed vector W on axis P, R and Q respectively ( system PRQ ) ;
Px, Py, Pz, Rx, Ry, Rz, Qx, Qy, Qz - projection of orth P, Q and R on axis X, Y and Z.
Projections of angular speed on measuring axes X and Y are defined :
                (| Wi|*(Yi - Yo))
W x i=--------------------------,      (2)
            __________________
         Ö( Xi - Xo)2 + ( Yi - Yo)2
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                (| Wi|*(Xi - Xo))
W y i=--------------------------,      (3)
            __________________
         Ö( Xi - Xo)2 + ( Yi - Yo)2
where
| Wi | - angular speed module;
X0, Y0 - indication of channels at initial state ( time moment t0 );
Xi, Yi - indication of channels for time period ti.
For realisation of this method it is necessary to use three systems of determination of three-dimensional co-ordinates of benchmark points. In the general case they can be replaced by nine single-channel measuring systems of one-dimensional co-ordinates. On condition that required rigidity of benchmark triangle at the moments of shock overloads be conserved, it is possible to manage with six single-channel systems. Even in this case the realisation of the above-stated method requires high expenses of the hardware.
For some particular problem statement it is possible to neglect translational motion of object along two axes of co-ordinates and to assume simplifications of the calculation formulas at the expense of neglect of some small components (for example owing to infinitesimal of object turn angles during measurement). Proceeding from the above-stated it is allowable to use 4 systems of determination of one-dimensional co-ordinates for three points of object. Thus the hardware expenses of method realisation are considerably reduced.
The principle of the developed measuring apparatus is based on a non-contact "shape from shading" method. During operation, the object edges are illuminated by light sources and there image is projected on a integrated photo-diode scanning array. The generated signals are filtered to eliminate noise; they are digitised and then processed by a computer. A small size and step of array pixels are provided to obtain position of object with a high accuracy.
The measuring range of the object parameters is defined by the optical system scale coefficient, distance from optoelectronic heads and to the object. The range can be broadened or narrowed during mounting the optic unit of system.
The measurement is done with the help of software, which also generates other display parameters and documents.
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Two variants of optoelectronic measuring system were designed to be able to measure a parameters of movement.
The measuring apparatus is built from five basic modules. They are the optoelectronic unit, including the light source, and o ptoelectronic head (OEH), electronic control module, the computer and the software. The measuring range of the system is determined by distance from light source and OEH, the OEH optic components.
The system configuration is selected to accommodate the measuring task to be performed. The optoelectronic unit may have various configuration, containing 1, 3 or more optoelectronic heads. The electronic control module has to be set accordingly. A continuous measurement of the object position points at discrete steps in time, maintaining a high scanning speed enables to determine an object movement trajectory.
Two variants of system were designed: first one - "MARS-1" system for measurement of linear speeds and accelerations (Fig. 2); second one - "MARS-2" system for linear and angular speeds (Fig. 3).
For measurement an object is placed on the platform or in a suitable position in the field of view of the measuring head. The OEH scans the object edges line by line in time according to a preselected program this can be done on-line through the user interface. The scanning speed can also be set. The scanning speed can also be set.
At start moment of run-up of pyrocartridges or jet engines the object data record to memory begins. The records is done at strictly specific time moments according to timer by all of the channels. So, mutual profiles of object position are made.
The measurements of the optoelectronic scanning head are transmitted to the electronic control module where noise is removed and an AD conversion is done to produce suitable signals for the computer; it performs the evaluation of the measurements and displays the information in a required form. For information processing a IBM PC compatible computer can be used.
The system software provides data input and scaling, their processing and objects movement parameters display in the required form. Besides, the testing results can be stored up in the data base.
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The automated optoelectronic system MARS-1 is used for non-contact measuring of high speed object movement parameters: position, speeds and accelerations.
The field of system application is automated stands for testing and optimisation of flying aerospace objects components and constructions. System may be used also for testing crushproof and vibration strength.
The MARS-1 system contains an out optoelectronic head with an illuminator, an electronic unit and IBM PC. Technical characteristics of MARS-1 system are shown in Table 1.
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Table 1. Technical characteristics
|
â„– |
Characteristics |
Measurement |
|
1 |
Range of measurement of velocity is, m/sec  |
From 0 to 100 * |
|
2 |
Range of measurement of acceleration is , m/sec2 Â |
From 0 to 10000* |
|
3 |
One measurement time, sec |
0,0001 |
|
4 |
Accuracy of measuring, % |
less than 0,1 |
*The measuring ranges can be broadened or narrowed during mounting the optic unit of system
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The automated optoelectronic system "MARS-2" is designed for remote non-contact measurement of movement parameters: positions, linear and angular velocity as well as acceleration of fast objects2.
The field of system application is automated stands for testing and optimisation of flying aerospace vehicle components and constructions. System may be also used for testing crushproof and vibration strength.
The system "MARS-2" contains three optoelectronic heads with light source, an electronic unit and IBM PC. Technical characteristics of MARS-2 system are shown in Table 2.
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Table 2. Technical characteristics of MARS-2 system
|
â„– |
Characteristics |
Measurement |
|
1 |
The quantity of channels of simultaneous measuring : 1 channel - for measuring linear velocity 2 channels - for measuring angular velocity  |
3 |
|
2 |
Range of measurement of acceleration is , m/sec2 Â |
From 0 to 10000* |
|
3 |
Range of measurement oflinear velocity is, m/sec |
From 0 to 100* |
|
4 |
Range of measurement of angular velocity, is deg/sec |
From 0 to 5* |
|
5 |
One measurement time, sec |
0,0001 |
*The measuring ranges can be broadened or narrowed during mounting the optic unit of system
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The main advantages of the apparatus are non-contact operations, high speed, high precision, multipurpose and wide range of applications, small overall dimensions and low weight.
The systems software provides data input and scaling, their processing and objects movement parameters display in the required forms ( Fig.4 ). Besides, the testing results can be stored up in the data base.
The computer systems with original software for automatic measurement of complex objects are designed for aerospace and aircraft building industry. The process of measurement is completely automated by computer control. The systems provide a high precision and production rate of non - contact measurements, it is reliable and handily. Their high precision and productivity allow to automates the realisation of scientific researches and experiments.
This optoelectronic systems "MARS-1" and "MARS-2" allow not only to carry out quickly and high-level measurements, but also enables to process the received data statically. They also allow to receive the data, keep and transmit data in a database with instant access to the information 1-2
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Figure 4. Form of results displaying of object trajectory movement in three-dimensional co-ordinates
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The reception of three-dimensional digital model of object in a combination to software of their processing gives huge opportunities for study of object, modelling of various situations with this object.
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1.The automated optoelectronic systems "MARS" is designed for remote non-contact measurement of movement parameters: positions, linear and angular velocity as well as acceleration of fast objects. The systems represent a new computer-aided technologies of testing.
2. This optoelectronic systems "MARS-1" and "MARS-2" was used for testing aerospace objects for flying on Mars according International program .
3.The systems can be applied also for research and development in aircraft building industry.
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1. V. I. Syriamkin, V. S. Titov, U. G. Yakoushenkov, R. M. Galiulin and others, Technical vision systems. Reference book, V.I.Syriamkin, V.S.Titov, eds., Radio and svyz, Tomsk, 1993.
2. Rav. M. Galiulin, Rish. M. Galiulin, J. M. Bakirov and others, "Optoelectronic systems for object geometric parameters and spacecrafts testing," in Proceedings of The Third China-Russia-Ukraine Symposium on Astronautical Science and Technology, Xi'an, China, 1994.
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Russian