Study On Temperature Control Of Steel Pipe Indution Heating Based On Iterative Learning Control

Induction heating technology is based on the principle of electromagnetic induction,heating the workpiece by eddy current effect generating heat internal source.It has become the main heating technology in metal heat treatment process with the characteristics of high efficiency,clean and fast heating.At present,Chinese medium frequency power supply equipment has been relatively close to international top level in high power,reliability,etc,but in high precision temperature control,there is still a large gap in high precision temperature control,compared with the international top level.It leads the product quality is not high,obviously in the high end forging and hot rolling production.The paper focuses on the temperature control steel pipe induction heating process.In particular,according to the steel pipe surface coating craft requirements of a novel material factory,steel pipe is heated to about 900? by induction heating,so that the anti-corrosion materials is bonded to the surface.The main research work and results of the paper are as follows:(1)Induction heating mechanism modeling: the steel pipe is divided into smaller ring units by each segment stratified,and the inner heat source of the steel pipe is formed by the eddy current.Then the thermodynamic model is established,mainly considering heat conduction,taking radiation as the disturbance.Taking the power supply as input,the surface temperature of each segment as output,the paper derives the state equation of the system.The results show that the system can be simplified to a linear time-varying system,which only input matrix is time-varying.(2)Model Tuning and verification: tuning parameters of the model parameters through experiments,the simulation results comparing with the actual results show that the model has a high accuracy,and provides a reliable basis for further control scheme.(3)Iterative learning control methods: in this paper,the iterative learning control is first introduced to the induction heating temperature control because of the repeatability of steel pipe coating craft and the special working condition that only the terminal temperature is measured.The quadratic-criterion-based terminal iterative learning control algorithm is studied for the constraint and unconstraint case.For the demand of variable target temperature,an improved iterative learning control is proposed.The cost of the algorithm is that the final error can't converge to zero,but the algorithm can ensure that the input signal is always true.Simulation experiments show that the algorithm converges very fast,exponentially.(4)Temperature control software prototype system development: aiming to the actual temperature control requirement of the steel pipe coating induction heating process,the temperature control software based on iterative learning algorithm is deveploped.