Research On The Fully Digital Control System Of A Dual-frequency Quenching Machine For Rollers

To enhance the stability of processing quality for rollers, a detailed description about the design and manufacture of the fully digital control system of a dual-frequency induction heating quenching machine has been given. The principle of the dual-frequency power supply has been researched in depth, and the intermediate frequency power supply's main controlling board is built on analogous and digital circuits with simple structure but strong ability of counteract interference. In terms of rectifying circuit, a digital dephasing technology has been introduced to enhance output voltage regulation's precision; In terms of inverting circuit, SCR parallel inverter is started by a swept-frequency circuit with separate and self-excitation based on PLL technology, which can solve the low starting success rate problem that usually happened in former circuit designs; In order to strengthen the circuit's working stability and compatibility with other machines, a double closed loop of PI regulator is designed. Instead of plugboard circuits, this main controlling board combines lots kinds of function to raise the working efficiency of the intermediate frequency power supply and improve its compatibility to other equipments.Then VVVF and servo motor have been put into use to improve quenching machine's electric-drive system, meanwhile, this thesis has introduced a S7-300 PLC hardware structure in remote stations, networking field equipments via PROFIBUS-DP. The controlling programming has realized the excitation-free of the manual/auto operation switch for the dual-frequency power supply, and planed each subsystem's division of labor as a whole. At last, a monitoring and control system is designed based on FameView configuration software which reflects the working status of electric devices and intelligent instruments on upper monitor, and records and analyzes various data indexes in practical operation of the system in forms of statistics report. Users can inquire fertile historical curves in database, then solidify optimal parameters, and consequently sum up and innovate quenching technique to raise product management efficiency.After repeated demonstration and debugging, the quenching machine with intellectual property right of our own has successfully gone into production, making the processing quality for rollers match the demand of modern production and economizing huge cost. The whole package of the machine has achieved on an advanced level in domestic industry.