| The shearer is the critical equipment of coal mine production, its work stability and reliability has great impact to ensure coal mining work. At present the shearer in domestic/abroad mainly adopts electric traction shearer, there are three traction motor speed regulation technologies as AC variable frequency speed regulation, switch reluctance speed regulation, and electromagnetic speed regulation. AC variable frequency speed regulation has advantages of good starting performance, high speed regulation accuracy, and strong reliability, nevertheless during application of shearer traction it shall be fitted by transformer, the system volume is great, and operation is complicated. When the switch reluctance speed regulation system is used for shearer, the start torque is great, conversion efficiency is high and control circuit is simple, but motor control needs position transducer, control algorithm is complicated, and operation noise is fairly great. Electromagnetic speed regulation system is the traction control system of shearer and adopts slip clutch to regulate rotation speed with advantages of small volume, simple control system, mature and reliable technology, and variable torque control, electromagnetic speed regulation shearer has apparent cost performance advantage, and is the new trend of shearer equipment development.Up to the present, most manufacturers adopt highly reliable industrial computer and PLC system to control shearer, PLC may realize simple functions, yet has poor expansibility. Operating system of industrial computer is mostly same as PC, could not perform optimization according to the control features and requirements of the shear, the frequency converter and its driver for traction part of the shearer are still relying heavily upon imports. Electromagnetic speed shear is a main type for shearer, PLC control is dominant in its control system, needs to be improved in aspects of HMI and communication function. This paper proposes an embedded system to substitute the industrial computer and PLC, proposes electromagnetic speed regulating motor to supersede switch magnetic resistance motor and explosion-proof asynchronous motor associated with inverter, so as to reduce the price of shearer, enhance operating performance, guaranteeing coal miner ’ s safety and the operation of normal tasks. In order to achieve such objectives, continuous time model was studied in this paper, dual closed loop control system structure and discrete digital controller were proposed, relay feedback theory that adjust operating parameters and fractional calculus were adopted, a nover fractional order controller with weight ratio operator was designed, speed prediction planning method for electromagnetic speed shearer was introduced to enhance system adaptability, the control system of the electromagnetic speed was implemented by adopting embedded software and hardware.It is pointed out in the introduction of this paper that theoretical and application research on shearer that indispensable equipment in the production of coal mine has profound significance. After comparing the advantages and disadvantages of three traction speed control technologies, this paper takes electromagnetic speed regulating motor as the object of research, further studies its control technology. Development situation of electric traction shearer at home and abroad in recent two decades is introduced in the research on current status and trend of shearer. At present, electric control technologies of foreign shearers are custom-bulit systems, with their respective characteristics and leading concept, while in China, after the development of several generations of electric control system, the system of industrial computer and PLC control is dominant, intelligent control system has been developed slowly. In aspect of embedded application of shearer, several papers have been published successively in recent years, DSP and ARM are mainstream controllers, their functions are generally auxiliary functions of the system, for example, alarm, communication, diagnosis, storage etc, while embedded system, as main unit of the system to execute the traction or cutting function of shearer, has not been used in China. Foucused on current status, this paper puts forward specific research objectives and research content, formulates research route.In the second chapter of the paper, this paper firstly analyzes special structure of electromagnetic AC speed regulating motor, further analyzes natural mechanical properties of electromagnetic speed regulation shearer, utilizes simulation test for the modeling and manual adjustment of natural characteristic curve, further studies the control model of electromagnetic speed regulation shearer from this start point. In traction work of electromagnetic speed regulation shearer, its loads have compound multiple characteristics, as a traction motor, electromagnetic speed regulating motor may adapt to coal mining traction characteristic well using variable torque method, through reasonable algorithm control, traction of electromagnetic speed regulation shearer may realize rapid and stable operation. In order to realize the design objectives, Its control method is improved to be adaptive to the applications of shearer, speed control system of closed loop speed control may achieve satisfactory effect. Power supply environment of the work surface under mine is poor, grid voltage often fluctuates, changes the operating current of motor armature, thus deteriorates speed control performance, solution of this problem is to introduce inner loop of current control, current disturbance is thus suppressed rapidly before it affects the speed whenver it appears, so as to keep stability of the load speed.In the automatic and industrial control field, the digital controller gradually substitutes the analog device controller by depending on its advantages as quick speed, high accuracy, and powerful logic computing capability, etc, the control rule is the approximate control on the basis of discrete sampling theory, in order to ensure that electromagnetic speed regulation shearer can better adapt to embedded system control, in the chapter 3 of this text, it is based on electromagnetic speed regulation continuous time system control architecture and mathematical model, to establish the discrete time digital controller and analyze the control performance thereof. On the basis of discrete control system theory, speed loop and current loop both adopt P1 control, to establish double closed loop discrete controller of electromagnetic speed regulation, to compare and analyze the performance via simulation test and continuous simulation controller. The traction motor of electromagnetic speed regulation shearer adopts double closed loop controller to improve system stability and dynamic response performance. Nevertheless, during actual engineering application, due to difference of motors and drifting of motor parameters with temperature, environment and time during operation, the model architecture parameter shall be timely regulated to maintain that it is always at optimal status. In engineering practice the ordinary tuning method includes Z-N critical proportional scale method and relay feedback test method, the critical proportional scale method is to create oscillation via externally added signal to determine the critical gains and critical cycles of control object, and then adopt empirical equation to calculate the optimal system parameter of the system, nevertheless this process needs to manually and repeatedly regulate the proportion and integration element. In this paper the relay feedback method is adopted to recognize the parameters of electromagnetic speed regulation shearer, and introduce in relay test in the periphery of stable operation point of system, to complete the detection during closed loop operation process without impacting normal operation process of shearer. The high precision A/D acquisition technology is adopted to improve recognition range of oscillation amplitude, the test time is fairly short without system shutdown and restart, and this is in favor of continuous update and operation of self-adaptive parameter shearer system. The cascade stage relay feedback setting architecture is established for double closed loop of electromagnetic speed regulation shearer to determine the test process, and deduce the critical gain and critical cycle mathematic formula of electromagnetic speed regulation shearer, to demonstrate the setting effect of relay feedback parameter via simulation. Only after the stable oscillation cycle of object under test is acquired, shall the relay feedback test accurately judge the system parameter, the test time is determined by stability of object under test. In order to shorten test time, the biased-relay feedback test is adopted to calculate the response time of offset hysteresis loop, to derive system architecture parameter via two times’ test at least, and improve system parameter recognition speed of electromagnetic speed regulation shearer.On the basis of studying general discrete digital PID double closed loop controller, fractional calculus theory is introduced in to renovate the architecture of internal and external loop PID, so that it can better adapt to mathematical model of electromagnetic speed regulation shearer. According to control characteristic of electromagnetic speed regulation shearer, the current loop adopts the general digital discrete PI controller, and the speed loop adopts fractional order PIλ controller, to derive the order of fractional order PIλ controller via cut off frequency and phase margin, the weighting ratio discretization operator is adopted to derive fractional order PIλ controller of electromagnetic speed regulation shearer. The simulation test shows that, electromagnetic speed regulation shearer fractional order PIλ controller has better response performance and tracking performance in contrast with general discrete digital PID controller.Affected by electromagnetic noise and other factors, traction speed of the shearer will also change instantaneously and slightly in the regulating period of closed loop in dual closed loop discrete model of the electromagnetic speed regulation shearer, these speed jitters will bring about mechanical shock and wearing to the shearer, also affect the stability of onboard equipment of electromagnetic speed regulation shearer. With respect to this problem, sampling period may be shortened, interpolation prediction and planning may be performed for control speed signal. The paper uses least square theory to analyze the stored data of certain length, uses minimum covariance to measure the change of fitting factor, simulation test of the measured data shows that, least square method may predict speed to certain degree when linear order is increased, however, since noise change rules are not considered, degree of prediction distortion is very high. Wiener filtering regards given data in two parts, namely, real signal and noise, establishes observation equation matrix to solve current data system transfer function, uses autocorrelative matrix of noise to break down historical data, so as to obtain the predicted speed. Through simulation test, Wiener filtering recovers and predicts noise and main signal, yet its tracking accuracy is not high. The constant gain α-β filter forecasts target position and speed in certain period quantity, selects state transition matrix and noise distribution matrix in the prediction according to characteristics of the object, gives extrapolated data prediction according to uniform motion principle. Simulation proves that, the effect of the constant gain α-β filter is very poor for electromagnetic speed regulation shearer, because the motion of electromagnetic speed regulation shearer could not be deemed at uniform speed during high speed sampling. The kalman filter prediction regards state transition matrix and gain matrix as variables, realizes linear regression of minimum variance via weighting comparison of the predicted value and true value, simulation test verifies accurate speed prediction and tracking by the kalman filter. T curve, S curve and trigonometric S curve are used for speed planning of electromagnetic speed regulation shearer, speed change rules are derived respectively, simulation test and on-load test prove that, acceleration control and speed control of trigonometric S curve are very favorable to reduce speed jitter.With respect to hardware design of electric control system for the electromagnetic speed regulation shearer, its main parts include communication management host, digital expansion, analog expansion and radio communication. AT91SAM9260 processor with ARM9 core is used for the design of communication management host and periphery circuits, STM32 chip with ARM CM3 core is used as main processor for the design of digital extension and analog extension module. STM32 ultra low power processor with ARM CM3 core realizes remote controller and remote control host of electromagnetic speed regulation shearer in 433 M frequency range. Communication management host of the electromagnetic speed regulation shearer adopts customized embedded Linux operating system. With respect to the peripherals required for electromagnetic speed regulation shearer, clipping and transplant are performed on AT91SAM9260 processor for BootStrap, U-boot, Linux core and root file system, primary boot image with BootStrap is used to initialize main processor, the function of U-boot is to initialize memory and Flash, boot operating system kernel from loading, Linux core realizes task scheduling, memory management and driver functions, obtains system image of individual parts by editing configuration file after cross compiling. In aspect of system communication, multi-interface Modbus server of three master stations and two slave stations is designed for electromagnetic speed regulation shearer, multithread programming technique is used to realize data exchange between the management host and slave modules. |
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