Synchronized Multi
Abstract: This paper presents a multi-cylinder long stroke synchronization test a new method to replace the traditional process of a large number of absolute displacement measurement sensors, to achieve real-time detection, practice shows that the method of direct, reliable, and has significant technical and economic value and wide application prospects.
1 Introduction Hydraulic synchronous operation of the testing is very important, because this is the performance of the system of scientific assessment methods, but also on the development of early exposure to defective equipment, timely treatment, or improvement, improve quality, ensure reliability, an important practical and effective means. As the test is conducted in a simulated real working conditions, can maximize the design failed to take account of factors “adding” to the test, the technical and economic values can not be ignored.
Long stroke cylinders System wide, especially in large, very widely used in heavy equipment (such as large gate lifting equipment, marine engineering, engineering machinery, etc.). Equipment operation in a foreign load imbalance and random changes in the total state, so long stroke cylinders simultaneously demanding, or result in poor equipment performance, and even serious damage, collapse of the failure. On multi-cylinder long stroke, such as using the traditional method of detecting the absolute displacement, then the process must be a large number of displacement sensors, obviously not the economy, the installation is also very difficult, not suited to simulation tests and field testing needs. After years of research and practice, this paper uses the relative method, multi-cylinder long stroke simultaneously running online testing, current research and production practice to achieve good results, briefly described below.
2 test works Synchronization test system to connect sensors and synchronous cylinder arrangement of works shown in Figure 1. The relative displacement measurement system using short trip grating sensor for the detection device. Grating displacement sensor 7 and the sliding scale by the Length of 8 (first reading), with a fixed length and sliding scale is installed in the different cylinder piston rod, the system work, Length, and move the slider along with the piston rod. When two simultaneous movement cylinder piston rod, Length, and there is no relative motion between the sliding scale, the reading head does not signal output; when two cylinder piston rod is not synchronized, the Length and the relative motion between the slider , the reading head has displacement error signal output.
Figure 1 Run the process, for the protection of grating damage as cause of the accident Buzhi Yu, grating designed to protect the safety of the structure. Figure 1, one for the cylinder, the magnet 4, connecting plate 3 and the piston rod 2 fixed link, Length of 7 and the piston rod 9 fixed connection, as the magnet 4 and 5 generated magnetic board magnetic force, the slider 8 will 2 with the piston rod movement. When the accident that caused a larger relative displacement of two cylinder piston rod, the magnetic plate 5 (sliding scale) hit 6 iron block can not continue to move, and the magnet 4, connecting plate 3, the piston rod 2 by a fixed link will continue to Move led to magnetic board magnets 4 and 5 of the disengagement, the security protection of the grating.
In the test, running two-cylinder piston rod is the most consistent level of interest and the most fundamental problem, these methods can improve the long stroke cylinder synchronous multi-test system test requirements.
3 signal exchange Figure 2 is a signal transformation and block diagram of a computer test. Reading the first output of the displacement signal is sine wave, and the signal is weak, detection devices transform circuit according to the actual needs, should have the following basic signal processing functions: amplification of weak signal processing to improve the Resolution of the division circuit, distinguishing between grating is the opposite direction to the displacement of the debate circuit, real-time observation of the count display circuit, to improve system reliability and signal protection circuit such as the absolute zero potential. Is the grating signal processing discussed the technical points are as follows:
Figure 2 Segmentation and pulse forming circuit to argue:
Grating has a high groove density, if the system is 25 lines / mm, asking for a higher-resolution testing, using a small pitch, apparently technical difficulty and economically does not pay. To increase the use of electronic Subdivision Resolution is the most widely used method, commonly used four octave bridge, phase modulation, phase-locked frequency and other subdivision. The system uses four sub-harmonic direct method, it is by two-way grating sensor output signal 90 ° phase shift, through differential, followed by four 90 ° phase difference pulse signal, to achieve improve-resolution. For the 25 lines / mm grating available digital readout 10 m of the Resolution to meet the requirements of synchronization precision test.
In the synchronous system operation, two cylinder piston rod relative to the direction of movement is a change of zero for the discriminant direction of movement (symbol error), must use two-way grating sensor 90 ° phase difference output signal. Figure in S and C is the output of the phase difference of 90 ° of the two-way sine and cosine signals, when the bone when the foot to make a move, C advanced S / 2, S-signal pulse generated by the differential circuit with a high C signal level 1 in phase with the gate pulse output obtained; and S generated by inverting the pulse signal and low signal C 2 phase with the gate, the output low. Similarly, when the sliding scale to reverse the move, S advanced C / 2, and the gate 2 output pulse, and the gate 1 output low, and the door 1 or door 2, respectively, control the output pulse signal counter counts plus or minus pulse, the counter output state can accurately reflect the two-cylinder piston rod grating that is the direction of movement.
Absolute zero potential functional circuit: System during actual operation, interruption operation, shutdown, power failure, etc. is unavoidable, it will result in missing or erroneous measurement results. Fortunately, most of the grating were set to zero when the position marker to zero as in the work to provide the absolute zero point address the issue. To this end, should the appropriate circuits of absolute zero, ie zero pulse forming circuit. To meet the main grating different requirements and ensure the zero harmonic pulse and count pulse synchronous, can not directly use the original raster output zero signal as a zero pulse, but must be appropriately selected, after doubling the square wave signal with the original zero after conditioning The square wave phase, and to doubling the width of the same wave conditions as a strobe, pulse count this out as a zero pulse.
4 computer detecting
Grating sensors pick up the synchronization error signal, after amplification shaping, sub-contracting to other circuits into a pulse signal into the counter after 8253, the control logic running in the data register and shift register, and digital signal sent to the chip 8250 interface circuit, via RS-232 bus to communicate with the computer, composed of computer data automatically detects synchronization errors
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