Design Of Intelligent PE Electrofusion Welding Machine

The intelligence level of common electrofusion welding machines in the market is mostly relatively low,which is generally manifested in fixed output mode,cumbersome operation of external equipment,low efficiency and bulkiness.It is becoming more and more difficult to apply to the welding of more types of pipelines.To solve the above problems,the intelligent PE electrofusion welding machine designed in this paper is studied as follows:1)Research on the optimization method of welding quality: according to the welding mechanism and physical properties of material of the electrofusion pipe fittings,constructing and verifying the model of finite element thermal analysis;Considering the influence of ambient temperature,comparing with traditional welding parameters,combining with input power,interface temperature and thickness of melting layer,giving an optimal parameter configuration method based on constant temperature control;By analyzing the relationship between resistance and temperature in the axial distribution of heating resistance wire,obtaining the realization principle of calculating internal temperature through external resistance detection.2)Main circuit design of welding machine: comparing and analyzing the advantages and disadvantages of common circuit topologies.Determining that the welding machine adopts the two-stage structure of the front stage staggered parallel boost PFC topology and the rear stage half bridge LLC soft switch topology.Analyzing the working principle and related characteristics of the front and rear circuits respectively.Combining with the actual needs of the subject,calculating and designing the circuit parameters.Finally,Testing the 3KW prototype is on the spot.The test results show that the output voltage of the front stage PFC circuit is stable at387 V,the power factor is greater than 0.98,and the output of the rear stage LLC circuit is 35～45V adjustable.The whole process efficiency is more than 92%,the peak efficiency is 95.3%,and the performance all reach the expected index.3)Design of intelligent control system: firstly,determining that the hardware part is a two-level structure with digital chip STM32F103 as the main control core and analog chip UCC25600 for resonance control as the slave control core;Secondly,designing the output voltage control circuit and the sampling circuit of voltage,current and cold resistance;Then through the programming of the software part,realizing the intelligent functions such as human-computer interaction,output control and wireless communication;Then,based on the software and hardware platform and combined with the theoretical analysis results,constructing a fuzzy PID closed-loop temperature control strategy based on the indirect detection of resistance wire temperature,and obtaining the algorithm control rules by simulating the welding effect;Finally,testing the integrated control system and main converter circuit on site,and comparing the welding effects of pipe fittings before and after optimization by stripping experiment.The results show that the optimized temperature control method can ensure better welding quality.