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Selection of displacement sensor and rotary encoder of pipe bender.

Pipe bender is now widely used in electric power construction in our country, railway construction, boiler, Bridges, ships, furniture, home appliances and decoration profession, its process followed continues in the conduct of modern skills. Today we are talking about the selection of the displacement sensor and rotary encoder for the pipe bender.

1. Selection of displacement sensor.

In pipe bending machine measurement and control system, demand more applied to the displacement sensor, used to test the related displacement measurement, for example the Y axis feed practice trek displacement, hydraulic control between the tool and so on, thus the displacement sensor selection is particularly important. In the planning of this system, the hall type displacement sensor is selected first, and the hall sensor is briefly introduced.

In some kind of metal or semiconductor wafer two end by controlling the current I in a direction perpendicular to the wafer surface on a magnetic induction intensity for magnetic field B, and the direction of the magnetic field is perpendicular to the current general happen the potential U. Hall effect is caused by the effect of the magnetic field on the magnetic field of the motion charge, and the relationship between the hall potential U and the control current J and the magnetic induction intensity B is in the formula:

In order to improve the sensitivity of hall elements, the requirement is that the Ph is large and d is small. Because the Rh is much larger than the metal, the semiconductor manufacturing hall element is generally used. It can be seen from the above that the given hall element (i.e., Ph) must be modified to change the size of the output voltage, if the control current is maintained, and the size of the magnetic induction intensity B is changed. The hall displacement sensor changes the Lr by modifying the relative position of the permanent magnet and the hall element, and then completes the transformation between the displacement and the output voltage.

Ii. Selection of rotary encoder.

Pipe bending machine equipment, the rotational speed of rotary encoder is used for measurement of photoelectric rotary encoder through the photoelectric conversion, can be output shaft angular displacement, angular velocity and mechanical quantity for the corresponding electrical impulses to digital output (REP). It is divided into single output and dual output. The skill parameters have the first pulse number (dozens to thousands of each), and the power supply voltage. Single-channel output refers to the output of the rotary encoder is A set of pulses, and dual output rotary encoder output two group A/B pulse phase difference of 90 degrees, after the two groups of pulse not only can measure speed, will also be able to distinguish the direction of rotation. Encoder, such as signal principle to points can be divided into: incremental pulse encoder SPC and certainly pulse encoder: APC, both are generally applied to the speed control or bearing detecting element of the control system. Rotary encoder have A central shaft of light code disc, on which there are circular and dark scribed line, have read photoemission and acceptance of equipment, has four groups of sine wave signal is combined into A, B, C, D, each sine wave 90 degree phase difference (related to A frequency of 360 degrees), will reverse, C, D signal superimposed on A, B two phase, can strengthen safe signal; Another output of a Z phase pulse to represent zero reference.

Because A, B two phase difference of 90 degrees, but only through A phase in the former is still the B phase before, and to identify forward and rotary encoder, through the zero pulse, encoder zero refer to bits can be obtained. The encoder has 5 leads, 3 of which are pulse output lines, 1 is COM terminal, and 1 is the power line (OC gate output type). The power source of the encoder can be an external power source, or it can directly use PLC's DC24V power supply. The "-" end of the power supply is connected to the COM end of the encoder, and the "+" is connected to the power end of the encoder. Encoder of the COM port input COM port connection with PLC, A, B and Z two-phase pulse output line directly interface with the input end of the PLC, A and B to differ 90 degree pulse, Z # believe the rotary encoder A circle as long as A pulse, generally used for zero basis, to connect and to pay attention to the PLC input echo time. The rotary encoder also has a shielded wire, which is used to ground the shielded wire and improve anti-interference. Resolution - how much of a pass or dark line the encoder provides for each rotation of 360 degrees is called resolution, also known as resolution, or how many lines are directly called, usually between 5 and 10,000 lines per revolution. The incremental encoder of the incremental and positive rotary encoder is the direct use of the photoelectric transformation principle to output three square wave pulses A, B and Z phases. The pulse phase difference of A and B is 9O. When the incremental encoder rotates, it has corresponding pulse output, its counting origin is arbitrarily set, and it can achieve infinite accumulation and measurement. The encoder shaft will output a fixed pulse, and the number of pulses will be determined by the number of lines of the encoder grating. At the time of demand improvement resolution, it can be used to double frequency or replace the high resolution encoder by using A and B signals with A phase difference of 90 degrees. There are many grooves on the coder code plate, and each line is lined with two lines, four lines, eight lines and sixteen lines. Arranged so that, in each position of the encoder, after reading each of the scribed line, dark, get a set of zero power from 2 to 2 n - 1 to the power of only two hexadecimal code (gray code), it is called n a certain encoder. Such encoder is determined by the mechanical direction of the coder, and it is not affected by power failure or disturbance.

Encoder certainly caused by mechanical bearing resolution of each bearing only sex, it without memories, without looking for refer to the point, and don't always count, when demand know bearing, bearing what time to read it. In this way, the anti-disturbance characteristics of encoder and the reliability of data are greatly improved [12]. Because in the process of produce practice, considering the sure type encoder capital is far greater than the incremental encoder, so the CNC pipe bending machine control system chooses incremental rotary encoder, the resolution on the basis of production practice selected as the 3600 line, in order to satisfied the precision of the system minimum resolution plus or minus 0.1 °. The measurement and control system USES the HEDSS (Hyde) rotary encoder, ISC4406 series, and the output pulse is 3600P/R, 5L.