Note: Cross posted from sbmzhcn.
1 The principle of automatic control system for milling process overview
Automatic control of the ball grinding mill powder size of purpose is to control the ball mill, the possible to improve the quality of products of powder. Using the computer control system of the grinding technology can improve the productivity, improve the control accuracy.
1.1 The principle and operating characteristics of ball mill
Usually the ball within a ball. Wall lining has wavy manganese steel armor of cylinder. Cylinder side as raw materials imported and wind blowing on the other side of the import, export for gas mixture of powder. The motor and reducer cylinder rotate speed, turning device with centrifugal and polishing in under the action of forces, armor will ball and raw material up to a certain height. Then use gravity free fall. Raw materials are mainly ball shatter, but also affected by steel ball and armor between, between the extrusion and grinding. A good FenZi grinding materials, mixing system into the next procedure. For running after a ball. Noise signal, the population pressure difference and relationship between output (see figure 1)
When the ball when the increase in quantity. The increasing power of ball mill, but until the noise signals, basically is found by large slope down. With the increasing of quantity of ball mill, export differential pressure also slightly increased. When feed greater depth. Differential pressure is rising sharply.
According to the curves shown in figure 1 characteristics can be seen. The noise signal is ball mill can reflect the quantity of materials. In the ball speed constant, the ball is a certain period, by measuring the grinding machine, the noise signal can be directly within the ball mill detection of materials. Therefore, the stability of the grinding machine for shoes. Control air purging, make their relationship, it can control the equilibrium of the grinding mill.
1.2 Difficult to control the ball milling
1) from its existing mill run characteristics. Noise is a variation of parameters, it is significant for mill materials. But because the ball inside the operating conditions of complex and measurement methods have greater error. So the control scheme in composition may have some limitations.
2) the grinding mill control system is more people, more than the output variables and strong coupling, large inertia, large delay of time-varying system. Using common PID control force lacerates the relationship between the variables. Not only get better effect, but also is caused extremely easily system stability.
3) the grinding ball control, except for shoes, accused of parameters for air outside disturbance. Also, the grain size ball and the effect of water content.
2 Grinding process is sub
General grinding system operating first kind is to use of ball mill for export pressure difference control parameters, the second kind is to use manual operation. Depend on the experience, the operator control over two methods, the existing control precision grinding low volatility of particle size, quality and yield of grinding is difficult to control. The quality of products.
Two of the automatic control system
Control system is composed of two parts, hardware and software are introduced as follows:
2.1 control system software
The software is used to control strategy of human-simulated intelligent control scheme. It is based on the principle of intelligent control, imitation of man’s thinking on intelligent decoupling, ball mill in order to ensure the safe and reliable operation, the software is the core logic by intelligent controller and intelligent algorithm.
Intelligent design according to the logic is running the operation experience, according to the input error and its variation formulate corresponding control strategy, the principle is: (1) the noise signals according to the ball, adjusting control of disc feeder under shoes. Make quantity to achieve stability.
(2) adjust air control two loop baffle, its balance. Intelligent algorithm according to the ball mill system controller is the coupling, the controller can be divided into three sons, each loop circuits using intelligent algorithm based on the input, and the changes of choose corresponding algorithm and achieve the purpose of humanoid control.
2.2 control system of the hardware
Control system hardware consists of: PLC and computer, isolation and transducers, inverter, noise and transform device, flowmeter, electric baffle valves, electric butterfly valve, pressure transmitter such equipment. A new form of the control system can fully test the key parameters of grinding process, through these parameters to PI C and computer provide enough information to control system, comprehensive treatment, and to form a correct judgment, provide accurate control signal, make grinding system according to the requirements of control in advance to work.