| Hydro-viscous drive is widely used in stepless speed regulation of fans and water pumps,soft start-up of scraper conveyors and belt conveyors.It has the characteristics of overload protection,small impact,high efficiency and high reliability,and plays an important role in energy saving of high-power equipment.Taking mine heavy scraper conveyor as an example,the dynamic characteristics and control strategies of electro-hydraulic coupling system of scraper conveyor based on hydro-viscous drive are theoretically analyzed and experimentally studied around the key technical problems of its controllable start transmission,such as torque characteristics,matching characteristics,control strategies and power balance.The purpose of study is achieving the heavy load start-up by using the peak torque and moment of inertia of the motor,improving start-up performance and multi-machine driving power balance.Aiming at the torque characteristics of controllable start transmission,a shear torque model of friction pairs under variable viscosity in pure oil film shear stage was established.The influences of flow field characteristics and variable flow rate on the shear torque of oil film in shear stage were analyzed.Based on the oil film pressure model and micro-convex peak contact pressure model in mixed friction stage,the torque characteristics of mixed friction stage were obtained.Torque balance equations of controllable start transmission were established combined with the torque characteristics of the drive motor and gear transmission.The transient torque characteristics of the hydro-viscous drive during the starting process were obtained,which provides a theoretical basis for the research of start-up matching characteristics and control strategy.In order to study the matching characteristics of the coupling system for controllable start transmission,the load characteristics of scraper conveyor under start-up condition were analyzed,and the influence of speed change on the start-up characteristics of scraper conveyor was revealed.According to the transient torque model of the start-up process of the controllable start transmission,the variation on the load torque under heavy-load start-up condition and the torque,oil film bearing capacity,oil film thickness and sliding power of the hydro-viscous drive were obtained.Based on the improved radar chart method,an evaluation system for matching the characteristics of controllable start transmission,driving motor and load was established.The matching schemes of four start-up speeds of scraper conveyor under different working conditions were evaluated quantitatively,and the optimal matching performance of S-type start-up under heavy-load condition was determined.In order to improve the start-up performance of scraper conveyor,a strategy based on S-type start-up was designed to control the oil pressure rise.Based on the torque model and analytic hierarchy process(AHP)of the start-up process of the controllable start transmission,the evaluation system of the start-up performance was established.The objective function of optimization design platform for soft start-up performance was established by using the joint simulation of MATLAB and Isight.The response surface equation of the objective function was obtained,and the influences of start-up time,load and moment of inertia on the start-up performance were revealed.The optimization model of start-up time was established by using the design of experiment and simulated annealing algorithm optimization,and the optimal start-up time was determined under different working conditions,and the start-up performance of scraper conveyor was optimized.In order to study the control strategy of heavy-duty scraper conveyor,the mathematical models of scraper conveyor,electro-hydraulic servo control system and hydro-viscous drive were established,and the control model of electro-hydraulic coupling system was obtained.A multi-physical simulation model of complex electro-hydraulic system was established by using AMESim and Simulink,and a fuzzy-PID control algorithm of controllable start transmission was designed.The dynamic characteristics of electro-hydraulic servo control system were analyzed.Through the analysis of the factors affecting the multi-machine drive power balance,the power balance control scheme was determined,and the start-up power balance performance was studied.The test platform of the hydro-viscous drive was developed,and the test box of controllable start transmission and the embedded intelligent controller were designed.The friction characteristics and dynamic torque characteristics of the friction pairs of the hydro-viscous drive were analyzed,and the soft start-up control strategies of the scraper conveyor were tested.The rationality of theoretical prediction model of friction pairs torque characteristics and the effectiveness of soft start-up control strategy were verified by experimental study. |
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