Microprocessor based autonomous control systemPresentation Transcript
INCARF Microprocessor Based Autonomous Control System of Longwall Coal Mining Shearer By: - Rajesh P. Barnwal , L.K. Bandyopadhyay, Gautam Banerjee et.al. Council of Scientific & Industrial Research E-mail: firstname.lastname@example.org
Microprocessor based autonomous Control System
A microprocessor based autonomous system has been developed at the Central Mining Research Institute, Dhanbad, INDIA under GAP project funded by Ministry of Coal, to control the load on the cutter motor while it is cutting coal face by controlling the haulage speed of the shearer loader.
To discuss the problem of shearer loader in smooth control of haulage speed in the coal face
To discuss about the intelligent control and circuitry employed in the developed system to solve the above problem
To discuss about the salient feature of the designed system
To discuss about the software developed for the above system
What is Shearer ?
The shearer loader is the versatile cutter-loader machine, which is a complex electromechanical system.
Presently majority of underground coal is mined all over the world by longwall mining system and the shearer loader is the most commonly used cutter-loader in this method of mining.
The productivity of a face depends primarily on the reliability and efficiency of this coal cutting and loading machine.
Operation of Shearer Operational Scene of Shearer Operation
Definition of the Problem
Field studies of the existing shearer installation reveal wide torque variations on the shearer motor due to variations in seam strength parameter, rock intrusions and faults encountered in coal seams which in turn results into current spikes.
Due to above problem, the machine had to be stopped frequently or its haulage speed slowed down manually by the operator to prevent it from being overloaded.
As a result the shearer motor becomes unduly stressed leading to rapid deterioration of winding insulation and premature failures.
At the same time, these uneven operations lead to excessive vibrations, reduce life of machine components, increased down time hours and reduce the production and productivity of the mine.
A power transducer and a chart recorder as shown below is used for continuous recording of voltage, current & Power-drawn by the Shearer at five different Longwall faces over a range of haulage speed available with the shearer.
Connection Diagram for Power Transducer and Chart Recorder Input from Gate Road Transformer Voltage (Volts) Power (Kw) Current (Amps) Gate End Box Power Transducer Shearer Chart Recorder
Shearer Specifications Specifications of the Shearer Seetalpur Colliery Moonidih Colliery Dhemomain Colliery VK-7 Incline Pathekhera Colliery Make ASL AB –16 ASL AB –16 EICKHOFF EDW 300/380 ASL AM 500 ASL AB -16 Motor Specification 550 V 150 KW 1440 rpm 1100 V 200 KW 1470 rpm 1050 V 380 KW 1470 rpm 1050 V 500 Hp 1470 rpm 550 V 200 KW 1470 rpm Drum Diameter (m) 1.47 1.4 1.6 1.65 1.2 Drum rpm 45 45 45 35 & 45 45 Average web depth (m) 0.4 0.6 0.55 0.4 0.5
Continuous Power Recording Fig.: Continuous recording of power at Seetalpur Colliery Haulage Speed: 5.18 m/min. Scale: 0 - 200 Kw Chart Speed: 3 m/hr Fig.: Continuous recording of power at VK7 Colliery. Haulage Speed: 2.5 m/min. Scale: 0 - 400 Kw Chart Speed: 6 m/hr
Cutting Power vs Loading Rate (Empirical Equation)
P av = A x L r 0.586
A = 1.1 x (ccs 0.908 /dcs 0.72 )
Where, L r - Loading & Cutting Rate (tonnes/ hr)
A – Seam Constant
ccs – Coal Compressive Strength (kg / cm 2 ) dcs – Depth of Coal Seam (m)
The designed system regulates the speed of the shearer based upon the analysis of the system parameters obtained from sensors and a programmed knowledge base leading to the development of an intelligent control and circuitry employed for this purpose.
The software is developed in assembly language on a 8-bit processor, which is meant for controlling different operating modes of the shearer.
The Variable Speed Drive for AC motor control are fabricated by commercial firms, which utilizes Double Edge Pulse Width Modulation (DEPWM) technique.
System Description T1 -Current Transducer for Cutter Motor T2 -Voltage Transducer for Cutter Motor T3 -Current Transducer for Haulage Motor T4 -Techo Sensor for RPM of Haulage Motor T5 -Sensor for O/p frequency of the Variable Speed AC Drive T6 -Sensor for O/p Voltage of the Variable Speed Drive Block Diagram of the Designed Control System MICROPROCESSOR REGULATED DC VOLTAGE SUPPLY CUTTER MOTOR CUTTING DRUM FIRING & TIMING CIRCUIT VARIABLE SPEED DRIVE DAC DISPLAY UNIT LOAD HAULAGE MOTOR T3 T5 T6 T4 T2 T1 12V 5V -12V 1100 V ADC
Block diagram of Laboratory Experimental Setup T1 -Current Transducer for Cutter Motor T2 -Voltage Transducer for Cutter Motor T3 -Current Transducer for Haulage Motor T4 -Techo Sensor for RPM of Haulage Motor T5 -Sensor for O/p frequency of the Variable Speed AC Drive T6 -Sensor for O/p Voltage of the Variable Speed Drive Block Diagram of the Developed Control System MICROPROCESSOR REGULATED DC VOLTAGE SUPPLY COMPUTER PC PRINTER FIRING & TIMING CIRCUIT VARIABLE SPEED DRIVE DISPLAY UNIT LOAD HAULAGE MOTOR T3 T5 T6 T4 12V 5V -12V 440 V ADC DAC PLOTTER
The software is developed in Assembly language in modular form.
All the basic functions to be performed by the microprocessor are developed in the form of subroutines
The software is developed taking into consideration of the different operations of the shearer so that in each of its operating modes the cutting motor is not overloaded.
Different operating modes of the Shearer:
Sumping Operation : To initiate the cut in the coal face.
Fleeting Operation : To move the shearer up and down the face without cutting.
Cutting Operation : To move the shearer up and down the face along with cutting.
Different Mode of Operation
Three mode of operation is provided in the system:
Modes Controlled By Available During Local/ Remote Operator Fleeting Operation Manual Mode Operator Sumping Operation Fleeting Operation, Cutting Operation Auto Mode Microprocessor Fleeting Operation, Cutting Operation
Auto Mode (System Software)
In the auto mode, the microprocessor takes the place of the operator.
It invokes the analog voltage signal continuously corresponding to the current drawn by the main cutting motor through a current transformer and signal conditioner.
The microprocessor will suitably control the speed of the haulage motor by the speed control algorithm.
Moreover, a maximum speed can be set for the haulage motor by software.
The Control Algorithm for the fleeting operation of the Shearer
CS - Control Signal to the Drive S - Small increment to CS CS2 - Max Control Signal to be given to arrive at the maximum fleeting speed FLIH -Full Load Current of the Haulage Motor during Fleeting IH - Actual Haulage Current IC - Cutter Motor Current V - Input voltage to the drive W - Input power of the haulage motor START MODE OF OPERATION LOCAL/ REMOTE MANUAL AUTO OPERATION SWITCH ON THE POWER CUTTING FLEETING 1 INPUT CONSTS. CS, S, CS2, FLIH CS = CS + S OUT CS TO DRIVE HAULAGE DELAY INPUT IH, IC, V, W OUTPUT IH, IC, V, W DISPLAY IS IH > FLIH IS CS > CS2 CS = CS - S NO YES YES NO
The Control Algorithm for the Cutting operation of the Shearer (Lab Experiment)
CS - Control Signal to the Drive S1 - Small increment in the CS S2 - Small decrement in the CS SSmin -Minimum Haulage Motor Speed SSmax -Maximum Haulage Motor Speed K, - Constants IHmax -Maximum Haulage Current IH - Haulage Motor Current V - Input Voltage to the Drive W - Input power of the Drive SS - Haulage Motor Speed SSAC -Estimated Haulage Motor Speed depending on the Random Number generated RAND -Random Number Generated CSH - Control Signal to stop the haulage motor SS - Difference between the estimated speed and actual speed S - Change in the control signal required to run the haulage motor in the estimated speed 1 INPUT CS, S1, S2, SSMIN, , SSMAX, IHMAX CS = CS + S1 OUTPUT CS TO DRIVE HAULAGE DELAY INPUT IH, V, W, SS OUTPUT IH, V, W, SS DISPLAY IS SS < SSMIN INPUT SS, RAND, IH IS IH > IHMAX IS SS < SSMIN IS SS > SSMAX CS = CS - S2 CAL K=RAND/SS CAL SSAC CAL SS=SSAC-SS CAL S = * SS CAL CS = CS + S OUT CS TO DRIVE DELAY INPUT IH, V, W, SS OUT TO COMPUTER OUT CSH STOP MOTOR NO YES YES YES NO NO NO YES
Flowchart The Control Algorithm for the Cutting operation of the Shearer (Actual Operation) CS - Control Signal to the Drive S1 - Small increment in the CS S2 - Small decrement in the CS SSmin -Minimum Haulage Motor Speed SSmax -Maximum Haulage Motor Speed IHmax -Maximum Haulage Current IH - Haulage Motor Current IC - Cutter Motor Current V - Input Voltage to the Drive W - Input power of the Drive SS - Haulage Motor Speed CSH - Control Signal to stop the haulage motor FLIH -Full load Haulage Motor Current FLIC -Full load Cutter Motor Current IC - Cutter motor current 1 CS = CS + S1 OUT CS TO DRIVE HAULAGE DELAY INPUT IH, IC, V, W, SS OUTPUT IH, IC, V, W DISPLAY IS IH > FLIH IS IH > IHMAX IS IC < FLIC IS SS < SSMAX OUT CSH NO YES YES YES NO NO CS = CS - S2 STOP MOTOR YES IS SS < SSMIN STOP MOTOR NO NO YES INPUT CONST. CS, S1, S2
Soft start of the haulage motor is accomplished to ensure gradual increase in cutting load to the main motor.
Manual start by the operator in the local/ remote mode by push button in case of failure of the microprocessor unit.
Smooth control of the acceleration/ deceleration of the motor
Stopping of the haulage motor can be accomplished by a single push button, whether it is in the local/ remote mode or auto mode.
The speed of the haulage motor will be controlled by the microprocessor both for forward and reverse rotation of the motor.
Salient Features Contd…
The control signal from the microprocessor to the drive is intrinsically safe.
All preset controls are easily accessible and the presets can be adjusted to suit a particular geomining condition.
Stabilized power supply for the microprocessor is obtained from the drive
The drive has a modular structure for ease in maintenance.
Reliability level of electronic and power semiconductor components is high. Moreover care will be taken to improve the overall reliability in design also.
The work has examined various aspects of the design and development of microprocessor based system to control the haulage speed of the shearer.
Efficient and modular assembly language programmes have been developed for microprocessor based control system design.
Encouraging results have been obtained from the investigations carried out at the laboratory.
It has been observed that microprocessor can effectively and intelligently control the thyristor and/ or power transistor based variable speed drives to optimise the speed of the shearer.
The findings of the present study would pave the way for the development of an autonomous control system for speed control of shearer loader.
Further conclusive studies are necessary in this direction to optimise the speed control system of the shearer in the field.