| The overall precision forming of large components demands that the large isothermal die-forging presses have the capacity to drive stably under extremely low speed, the improving of the low-speed stability is based on precise mathematical models of the press drive system,but it is difficult to model because of complexity of the large press. This paper mainly studied on modeling, parameter identification and factor analysis of stability, the main research work is as follow:1. A multi-level segmented online modeling method is proposed. The press drive system has complex structure, many unknown parameters, and it’s difficult to model and identify parameters. The multi-level segmented online modeling method is proposed, the complex press drive system is divided into three sub-systems, and subsystems have simple structure, and only some of the unknown parameters, reducing the difficulty of modeling and parameter identification.2. A dynamic friction model of considering the oil film thickness is modeled. LuGre model is a comprehensive friction model, but it can’t explain the hysteresis and non-local memory caused by the film thickness changing.A new dynamic friction model is proposed on the basis of considering the impact of the oil film thickness,and parameters are identified with Particle Swarm Optimization(PSO).3. Load online modeling method based on system input/output data is proposed. The main stress method is used to model the forging forming load,and the parameter identification is done with PSO basing on system input/output data, experiment is used to verify the model.4. The low-speed dynamic characteristics of the press is alanysised. Basing on simulation model of press driving system, the friction, leakage, fluid bulk modulus, damping, material parameters and process parameters on low-speed are analysised,and the affecting law to increase press low-speed stability is discoverered,wich is useful to develop the stability study of presses. |
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