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Design of heating power control system for PET bottle blowing machine |
Join：2016-12-14 |
Using 32 bit LPC2292 embedded processor as the core controller, with one-way thyristor as the execution component, using the principle of phase trigger power and voltage phase compensation, the design of LPC2292 bottle blowing machine heating system based on PET. After continuous adjustment, the system can effectively achieve the control of linear tracking of heating power, and can control the stability of the multi-channel infrared lamp. In the design based on the trigger voltage phase, according to the power supply voltage sampling to detect, to compensate for the different trigger phase voltage, realize linear heating power tracking adjustment, this design has been applied to the control system of PET blowing machine bottle heating success. 1 Introduction PET (Polythyleneterephtha- Late, commonly known as polyester resin) bottle blowing machine is to preform polyester material blown into the bottle through certain technical means used in blowing machine, mineral water bottles, beverage bottles and a variety of bottled carbonated plastic hollow container. PET bottle blowing machine is generally composed of blank supply system, heating system, air system and other auxiliary system. In the blank into the mold and stretch before forming the heating temperature of billet plays a vital role, in order to prevent the bottle, appear white opaque, uneven phenomenon, so that products meet the technical requirements of each position of the thickness, the average temperature in 80 degrees to 120 degrees between the precise control. At present, the heating control mode of PET bottle blowing machine is mainly the AC voltage regulation and the AC power. AC voltage in each half cycle of thyristor opening phase control, can adjust the effective value of the output voltage. AC power to the cycle of alternating current as the basic unit, through the control of the thyristor to change the thyristor on-off cycle of the cycle, the average value of the output power can be easily adjusted. The proposed optimization scheme of the circuit topology, compared with zero phase trigger periodic wave triggered by the advantages and disadvantages, pointed out that the phasing trigger is difficult to achieve linear power regulation. The technology of fuzzy PID control, internal model control, random adaptive predictive control and variable coefficient PID control are used in the theoretical study, simulation and application of PET bottle blowing machine temperature control. But in practice because of the large amount of calculation, the online calculation is more difficult, and the external influence factors are more complex, it is difficult to meet the requirements of the actual process. According to the characteristics of PET bottle blowing machine heating system, based on the specific application of the product, with simple and practical design principles, using LPC2292 as the core controller, using phase trigger power and voltage compensation control of heating power, can adjust the output power stability is quasi heating process. 2 heating power control principle 2.1 PET bottle blowing machine system structure According to the requirement of PET blowing machine heating system, the structure of heating system is determined as shown in Figure 1. The upper computer communicates with the 14 power regulator through the Profibus bus, and each power regulator is composed of a 10 way infrared lamp tube, and the upper computer controls the output heating power of the lamp tube in each power regulator. The output power of the PC can set the value of the power regulator, control mode, bus switch, sensor and other parameters, while monitoring the output power, power regulator current voltage, over-current, over-voltage, over temperature alarm lamp abnormal information. 2.2 phase trigger principle In the initial design stage in theory analysis, comparative analysis of AC power and AC voltage regulating scheme, field operation showed the presence of infrared lamp flicker of AC power, this will affect the temperature stability, and AC voltage does not exist such problems, so based on product needs, choose the AC voltage to achieve linear heating power output tracking, at the same time, according to the experimental results of power quantization and voltage quantification, choose the better effect of voltage quantization. As shown in Figure 2 for the SCR control circuit diagram, the circuit through the regulation of a reverse parallel to the unidirectional SCR VT1, VT2 trigger angle of the filament control of the heating power, the input voltage is UAB. As shown in Figure 3 for the trigger angle of the UAB waveform, the input voltage effective value of UAB. The effective voltage of the lamp tube load is U0, the effective value of the current is I0, and the waveform can be got from the figure 3: Actual control, the heating power of P0 for the output, can be determined according to the input UAB and alpha. By formula (3) shows that due to the heating power output is a transcendental equation, it is difficult to get the analytical solution, even with analytical solution, but due to the external voltage is changed, the array will lead to the unusually large, this is one of the reasons for regulation of phase shifting triggering difficult to achieve, in order to obtain accurate trigger angle considering the influence of UAB and alpha on the output power of P0, the algorithm design is divided into two steps to achieve, first set the input voltage at the output power of PS, US, according to the formula (4) to calculate the precise quantification of the corresponding 1000 output trigger angle, will trigger the phase angle stored in the array S[], trigger angle quantization the model shown in Figure 4, then detect the actual output voltage, and comparing the set voltage US, a trigger angle compensation mechanism, the output power to obtain the practical trigger angle. This system will be AC voltage in half cycle strictly quantized into 1000 points, the average quantization accuracy can reach 1 s, can fully meet the design requirements, set the trigger time of Ti, unit s, when the Ti from 1000 s gradually reduced to 0 when the trigger angle is getting smaller, the corresponding output power change, when the trigger time point calculation satisfy the relation (4), save the corresponding trigger value. Will be substituted into the formula (4), to establish a relationship with the US table S alpha. |