MODERNIZATION OF ÓÁØ-501ÀÊ
DRILLING DEVICE ELECTRIC DRIVES
Sergey Sechin, Alexandr Mischenko, Alexandr Alexeyev, Anatoliy Belitskiy
(JSC “Pluton", Zaporozhye)
tel/fax: /0612/ 62-20-37, E-mail: firstname.lastname@example.org
MM Money and Technologies Magazine – 2004 - ¹11. - p.28
Complete unit for electric drives control (ÓÊÓÏ)of drilling device ÓÁØ501-ÀÊ meant for hole drilling of gypsum bottom is described in the article. There is description of structural diagram of ÓÊÓÏ, functioning algorithm, ways of tasks solution, features of design.
Complete electric drive, frequency regulation, drilling device, master controller.
More and more heads of enterprises understand the necessity of technical re-equipment of existing technological units. Such re-equipment allows to increase labor productivity, to provide minimization of product cost, to decrease idle time of equipment, to simplify its control and to improve production standards. Upon that there is visible effect not only for big production enterprises but also for separate small objects.
Increase in volume of gypsum stone mining used in production of gypsum board panels and concrete has required from mining organization additional purchase of drilling device type ÓÁØ, applied upon development of gypsum mines. The order was placed at JSC “Krivorozhgormash". Customer required to produce device on the existing basis with maximum possibilities of drilling automation.
Customer required to produce device on the existing basis with maximum possibilities of drilling automation.
Electric equipment and automation means for ÓÁØ501-ÀÊ drilling device were made by JSC “Pluton” according to the contract with JSC “Krivorozhgormash”.
General Description of Modernization Object.
Drilling device is moving rubber-tired and consists of prime mover and semitrailer connected by hinge (drawing 1). Cabinet with power equipment, diesel motor, extruder, oil box, electric drives of oil stations, driver’s workplace and accumulator are placed on prime mover. Operators’ desk, hydraulic reservoirs and manipulators with fixed on them electric drives are attached to the semitrailer. Hole drilling of mine is made with auger-type or cylinder drill rods fixed on electric motor axes. Cutting crown made of hard alloy is fixed on the other end of the rod used for drilling. As a result of drilling there is hole (blasthole) with diameter up to 40 mm and depth up to 4.5 m.
| Drawing 1.
Moving drilling device
Experience of previous drilling device model operation allowed to understand its disadvantages that were worsening labor productivity, operational characteristics and machine reliability:
- non-regulated electric drive of drilling rod made impossible accurate selection of optimum frequency of crown rotation, and as a consequence, didn’t allow hole drilling with maximum productivity;
- manual control by crown pressing power to the drilling surface (forward pressure);
- unsatisfactory operation of drilling rod positioning system;
- full absence of automation, which required constant intense attention of the operator, affected his tiredness and increased possibility of emergencies;
necessity of the two operators working at the desk at the same time. for constant work, taking into consideration its intensive speed, the third operator was needed;
unsatisfactory operation of accumulator charge control system, especially upon its sufficient discharge and in conditions of line voltage fluctuations in wide range;
- unsatisfactory design of cabinets with electric equipment, which led to ingress of dust into them and regular failure of device operation;
big size of control desk worsened vision possibility upon drilling of vertical holes.
Elimination of indicated disadvantages was the main purpose of automation.
It required solution of the following tasks:
- to make electric drives of drilling device frequency-regulated in order to provide possibility of selection of optimal drilling speed;
- to provide electric control of forward pressure by crown pressing power to the drilling surface;
- to automate drilling process by optimization of settings of rotation frequency and drilling crown pressing power depending on drilling conditions;
- to automate accumulator battery charge process and to provide its rated modes;
- to introduce partial automation into drilling rod positioning process;
- to eliminate disadvantages of electric equipment and design found in the previous model.
End product of automation was complete unit for drilling device electric drives control (ÓÊÓÏ).
Hardware Support System.
When building ÓÊÓÏ electric equipment and components of world-leading foreign manufacturers were applied. The following equipment was applied in development:
- power commuting equipment of ABB production (contactors, automatic circuit-breakers),
- frequency converters of “transresch Antriebssysteme Berlin GmbH” production;;
- low-voltage commuting equipment RELPOL (relays);
- weidmueller installation units (plugs, terminal blocks, marking);
- belden cable and wiring products (connection cable);
- light-signaling and commuting units of Schneider Electric production (buttons, signaling lamps, switches);
- Rittal bearers and constructions (installation panels, cabinets).
JSC "Pluton" has more than 10-years experience of these products application, which shows that its application allows to reach high technical characteristics and operation reliability.
Structure of ÓÊÓÏ
After analysis of assigned tasks the decision was made that the structure of ÓÊÓÏ must consist of control desk CD, drawing 2 (located and fixed on semitrailer on manipulators foot) and control cabinet CC, drawing 3 (located and fixed on prime mover wing), connected by electric communications.
Control Desk CD
Control Cabinet CC
ÓÊÓÏ structure included the following functional systems:
- electric power supply, protection and commuting of power part;
- electric drives control;
- manipulators control;
- jacks and outriggers control;
- automatic and manual control of drilling process;
- charge and monitoring of accumulators;
- monitoring and control of outside elements;
- auxiliary power supply systems of ÓÊÓÏ.
Main units included in above mentioned systems and connections between them are given in structural diagrams, drawing 4.
Power circuit provided automatic phasing of voltage necessary for normal operation of ÓÊÓÏ, operation of compressor electric drives and oil pumping from power supply network, and also operation of electric drives of pumps and boring heads from frequency converters.
Manipulators control units were meant for control of hydraulic cylinders of jib, feeder, telescope, rotation unit, mover and additional turn.
Units of jacks and outriggers control were meant for control of jacks hydraulic cylinders of prime mover, semitrailer, apron and outriggers.
System of drilling process control included controller board and also group of control units and sensors connected with it. This group includes setter of forward force in manual drilling mode (setter of operating current in automatic drilling mode), buttons of feed direction control, switcher of drilling depth selection, drilling mode switcher, breaker of antijamming algorithm of rod and crown in hole.
Automatic charger provides two-circuit regulation of input parameters of charging rectifier. Outer circuit is meant for output voltage regulation at the level of 28V, inner circuit is for accumulator charge current limitation at the level of 25A. There is also monitoring of minimum voltage level in accumulator with light signal issue to the operator's desk.
Automation Tasks Solution
Selection of correct power circuit phase interlacing, creation of essentially new system of accumulator battery charge process control, and also elimination of existing drawbacks are the tasks that were solved on the basis of original circuit and design solutions.
All functions of drilling process automation were given to controller board (see drawing 4). And controller performed the following main tasks:
- control of electromagnet coils of manipulators hydraulic distributors, and unloading hydraulic distributor in accordance with control action;
- drilling process control;
- converting and scaling of information signals for their display at needle indicators.
Control process of drilling device manipulators was updated. In the previous model operators controlled hydraulic distributors by manual force to the hydraulic distributors valves. In developed ÓÊÓÏ there were 4 joystick type manual manipulators placed on operator’s desk for setting of control actions. Signals from joysticks contacts entered controller board for further processing. Commutation of hydraulic distributors electromagnet coils was performed by relay located on controller board, at the same time anti-swinging automatic system started operation and provided smooth start and stop of enabled manipulators. Thereby, hydraulic equipment control became more understandable, easier, and the main thing – sufficiently more accurate. Positioning process time reduced considerably.
Upon drilling controller performs functions of drilling mode selection, direction and forward force control, processing of signals from drilling depth sensors and current sensors.
In general drilling process provides the following. Drilling is performed until reaching of set depth of hole. After signal entry from hole depth sensor forward force reverse is done, rod automatically comes out of hole to the initial position, and corresponding light signal is sent to the operator’s desk. Electric drives of drilling head and oil station are disconnected if during some time after light signal there are no actions from operator.
Automation of drilling process provided adequate processing of two main modes: Standard drilling mode and jamming of rod and crown in hole mode. Upon standard drilling automatics functions consist in provision of maximum productivity at equipment operation rated mode support. Upon second situation many time is spent for unjamming and very often cutting crown remains in hole. When unjamming measures do not bring any results the rod itself is left in the hole, and operator continues working with reserve rod. Thus, jamming situation is followed by both material costs and degradation of operators’ labor productivity.
Creation process of algorithms of correct processing of two abovementioned situations was rather long. Difficulty was in selection of the most rational algorithm structure, and also in empirical selection of its parameters. The final variant of algorithm was formed directly on site, in mine bottom, and allowed maximum simulation of operator’s actions in standard and special situations.
Abovementioned two main drilling modes do not give full image of the tasks performed by controller. During startup and adjustment works we had to complete algorithm with new units. With this control system was becoming more convenient and understandable for operators. And otherwise, there were parts of algorithm developed specially according to insistent requirements of customers, but after testing they were not included into main program because of their inexpediency.
It became evident, that it was impossible to make complete automation of drilling process because of irregular structure of gypsum stone in mine. Automation of drilling start becomes complicated because of possibility of manipulator arrow sliding from bottom breast surface. Bottom breast is sufficiently uneven after explosion works and spoil heap.
For further automation of drilling process it is necessary to analyze many parameters: angle of arrow inclination, coefficient of static friction and sliding friction of sled with electric motor on arrow frame, crown dullness degree, drilling speed in the current moment of time, vibration level and many others.
In general, creation of control system operation algorithm was the most interesting, but also the most intensive stage in the process of ÓÊÓÏ creation.
For control of drilling device electric drives frequency converters (FC) VSI-7,5 CX4A2N0 of German company “transresch Antriebssysteme Berlin GmbH” production. These FC have all qualities of the most modern converting units: possibility of software and hardware configuration, complete diagnostics of all systems, storage of worst-case situations, availability of all necessary for converter and motor protections.
As mentioned above, ÓÊÓÏ structure includes two subsets of equipment for drilling process: right and left parts (see drawing 4). Each subset includes one FC with possibility of its connection from control desk to electric motors of oil station of drilling head. Thus, there is possibility of operation of one motor in subset from frequency converter, and other motor in the same subset from network, or both may operate from network.
Stabilization of electric motors rotation speed upon their connection to FC output is provided without feedback of rotation frequency. Upon manual drilling mode electric motor rotation speed control is performed from 10-positions rotation type controller with output signal proportional to rotation angle of its handle.
Selection of Hardware Implementation of Master Controller.
On attentive consideration of drilling device operation algorithms described in technical requirements it became evident that ÓÊÓÏ structure would require master controller. Three possible ways of controller hardware implementation were considered:
- single-board controller on the basis of units in the form of MicroPC (Advantech, Fastwell, Octagon Systems, Lippert);
- module type programmable logic controller (B&R, Simatic, Adam);
- self-development controller on the basis of one-chip micro controller (OCMC) produced by one of the leading manufacturers (Atmel, Microchip, Motorola, Scenix, Holtek).
Upon ways consideration we were taking into account technical characteristics of controllers, terms of their delivery, prospects of families development, availability of quality technical support, design and maintenance simplicity, price. Determining factors in controllers selection were:
- development presupposed low cost of equipment. This condition was practically unrealizable under application of purchased controller;
- it was necessary to provide storage temperature up to -40°Ñ, which was not acceptable for the majority of considered purchased controllers.
- JSC “Pluton” has sufficient experience in development and operation of controllers made on the basis of AVR OCMC produced by Atmel Company.
After detailed analysis of functions assigned to master controller and also with a glance at abovementioned we decided to perform this unit on the basis of AVR OCMC of Atmel production (AT90S8515-8PI). These controllers correspond to economy 8-Bit micro controllers built with application of extended RISC architecture of AVR. Performing one command during clock frequency period controllers have productivity of approximately 1MIPS per MHz, providing tenfold gain in code efficiency in comparison with traditional CISC micro controllers.
It is generally known that product design determines not only convenience in operation but also reliability. This development is not an exception.
Upon design development it was necessary to take into account requirements of GOST 24754-81 “Mine, standard electric equipment", GOST 24719 -81 “Mine electric equipment. Insulation, leakage paths, gaps, and also influence of mechanic external factors according to GOST 17516.1-90 for the group of mechanical version M18. Besides, it was necessary to consider increased dustiness and possibility of moisture ingress to the cabinets with electric equipment.
ÓÊÓÏ resistance to increased vibration was provided by accurate selection of components and also by special solutions of load-bearing constructs. Design department of JSC “Pluton” has sufficient experience in this type of works: majority of workers participated in design development of different FC for rolling stock.
We were working on solutions of ÓÊÓÏ fitting with pointer indicators resistant to vibration produced by leading foreign companies. Unfortunately, we had to admit that such units are not supplied to Ukraine nowadays. We came to this opinion after conversation with representatives of different companies at "Electrical Technology – 2003” exhibition (exhibition center “KievExpoPlaza”). That’s why we decided to apply equipment produced on the territory of CIS traditionally used in automotive-tractor units and electric rolling stock (see drawing 2).
Increased dustiness and possibility of rich moisture ingress required each cable input into cabinets through hermetical input and also special attention to design of cabinets and desks.
Design development was complicated by extreme saturation of control desk of control elements, signaling and indication (see drawing 2). Control location was necessary to perform taking into account their logic interconnection. In order to satisfy customer’s demand to make desk width no more than 500 mm we had to move some switchers to the side panel of the desk. As experience has shown, this solution appeared to be very convenient and understandable for operators. Besides, it allowed to reduce desk width to 350 mm which 1.42 times less than customer’s requirement.
ÓÊÓÏ supply was made in short terms. From the moment of contract signing to the delivery of developed and manufactured ÓÊÓÏ less than 4 months had passed. Intensive operation speed was complicated by introduction of considerable changes and improvements into technical specification and technical requirements on design phase.
Despite mentioned difficulties tasks of ÓÁØ-501ÀÊ drilling device automation were fulfilled. Owing to automation only one operator can control two drilling rods instead of two operators on non-automated device and at the same time total production per device increased for more than 25%, intensity and tension of operator’s labor sufficiently reduced. Wear of drilling device operation equipment also reduced.
22 months passed from startup of automated drilling device. During this time there were no failures in electric drive and automation operation and this fact confirms their reliability in operation, simplicity in operation and maintenance.
The best evidence of it is repeated offer from customer to develop and produce another device. At present time we are negotiating with customer to clarify technical characteristics of this device. We are planning to make it more “intellectual” by means of automation of additional units and mechanisms.
Published in MM Money and Technologies Magazine – 2004 - ¹11. - p.28