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Components of Positioning Control and Their Roles 3

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3.

Components of Positioning Control and Their Roles

Positioning control requires a number of components such as a positioning controller, servo
amplifier, servo motor and drive mechanism. This section describes the role of each
component.

Positioning Control

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Summary of Contents for MELSEC-F

Page 1: ...Positioning Control Training Manual ...

Page 2: ...r before connecting disconnecting units or opening any safety covers Never insert your hand or any other object into a moving part CAUTION Never change the wiring or configuration of demonstration euipment without permission or if you are unsure of how to configure a system correctly Such actions may cause failure malfunction injury or fire If a simulation unit such as an X Y table generates an ab...

Page 3: ...i Positioning Control Manual number JY992D89901 Manual revision A Date July 2000 Positioning Control ...

Page 4: ...Positioning Control ii ...

Page 5: ...dom 01707 278 695 Please tick the box of your choice What condition did the manual arrive in Good Minor damage Unusable Will you be using a folder to store the manual Yes No What do you think to the manual presentation Tidy Un friendly Are the explanations understandable Yes Not too bad Unusable Which explanation was most difficult to understand Are there any diagrams which are not clear Yes No If...

Page 6: ...Positioning Control iv ...

Page 7: ...equipment The following relevant manuals are available and should be referred to Manual Name Number FX 10GM FX E 20GM Hardware and Programming manual JY992D60401 FX 10GM Users Guide JY992D68401 FX2N 10GM FX2N 20GM Hardware and Programming manual JY992D77801 FX2N 10GM Users Guide JY992D77701 FX2N 20GM Users Guide JY992D77601 FX PCS VPS Win E Software Manual JY992D86801 FX2N 10GM FX2N 20GM Connectio...

Page 8: ...Positioning Control vi ...

Page 9: ...ontrol in accordance with command pulse 3 7 3 2 2 Deviation counter function 3 7 3 2 3 Servo lock function 3 7 3 2 4 Regenerative brake function 3 8 3 2 5 Dynamic brake function 3 8 3 3 Drive mechanism 3 9 3 3 1 Concept of drive system movement quantity 3 9 3 3 2 Setting the target position 3 11 4 Advanced Positioning 4 1 4 1 Interpolation control 4 1 4 2 Other controls 4 3 5 Actual Positioning 5 ...

Page 10: ...Positioning Control Contents viii ...

Page 11: ...oning by AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control The World of Positioning Control 1 ...

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Page 13: ...nvolves speed and precision As speed can be related to productivity it is an area of much development But when the machine speed increases a problem with the stop precision is often generated In order to solve this problem diversified grades of position controllers have been required and developed Improvement of the machine efficiency generates immeasurable added value including reduction of labou...

Page 14: ...ntative types their features and weak points Pneumatic Air source and high grade piping are required High torque is not available Multi point positioning is complex and very difficult to achieve Change in positioning is difficult Brake motor Positioning mechanism is simple Repeatability is poor Change in positioning is difficult When optical sensors or limit switches are used for stop Clutch brake...

Page 15: ...is good Maintenance is required for motor brushes It is not suitable for rotation at high speed General purpose inverter and general purpose motor Multi speed positioning is available using high speed counter High precision positioning is not available Large torque is not available at start Specialized inverter is required AC servo system Precision is good Maintenance is not required Positioning a...

Page 16: ...ounter When the pulse number reaches the preset value the moving part stops In this method because limit switches are not used the stop position can be easily changed Position control Pulse command method An AC servo motor which rotates in proportion to the input pulse number is used as the drive motor When the pulse number corresponding to the movement distance is input to the servo amplifier of ...

Page 17: ...mand is given the load size and the time delay since the stop command is given until speed reduction actually starts If the required stop precision is not satisfactory when stopping from the normal operation speed the most effective method to improve the stop precision is to reduce the operation speed However if the operation speed is simply reduced the machine efficiency may also be reduced In ac...

Page 18: ...d by one rotation of the motor The movement quantity per pulse is regarded as the minimum unit for the stop command However the coasting distance at stop is not eliminated Pulse command method In this method using a servo system the weak points described above are improved A pulse encoder is attached to the servo motor detecting the motor rotation quantity workpiece movement distance to continuous...

Page 19: ...ioning by AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control Positioning by AC Servo System 2 ...

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Page 21: ...tation pulses at a specified frequency The command pulse number is subtracted by the feedback pulse number and the speed command to drive the servo motor is made from the deviation accumulated pulse number When the accumulated pulse number becomes 0 the servo motor stops The servo motor is equipped with a built in encoder pulse generator dedicated to high speed response and suitable to positioning...

Page 22: ...ich the servo amplifier automatically detects the load inertia moment and adjusts the gain This is possible even if the load inertia moment is unknown Aspects described below are now incorperated to AC servo systems which offer marked improvements from previous products In FA work place a downsized AC servo system occupying less space is required Compact and light servo system In accordance with s...

Page 23: ... distance to the target position The flexibility to change the target position electrically and easily is an important requirement Several cases of positioning using an AC servo motor are systematically shown below Constant feed In the press shear process for cutting punching etc the processed material is positioned with high precision to produce a constant sized product Tapping In order to tap a ...

Page 24: ...order to hold the lifter stationery and prevent drop of the lifter by power interruption a servo motor with electromagnetic brake is used Cart travel control A servo motor is mounted in the travel cart as the drive source A mechanism such as rack and pinion is adopted to prevent slippage between the wheels and rails Carrier robot After the conveyor stops the 2 axis servo system and the arm lifting...

Page 25: ... AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control Components of Positioning Control and Their Roles 3 ...

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Page 27: ...1 3 Components of Positioning Control and Their Roles Positioning control requires a number of components such as a positioning controller servo amplifier servo motor and drive mechanism This section describes the role of each component Positioning Control ...

Page 28: ...d and the movement quantity in command pulses to the servo amplifier Transfers signals between the programmable controller Controls return to the zero point Improves the power factor and cuts noise Protects the power circuit Rectifies the AC power of the main circuit into the DC power in the converter and smooths it in the smoothing circuit When the DC power is converted into AC power in the inver...

Page 29: ...ary device The actuator moving part drive mechanism is equipped with speed reducer timing belt ball screw and limit switch Diversified auxiliary devices are also controlled in accordance with positioning The PLC or the positioning controller also controls auxiliary devices The auxiliary device operation completed signal is output to the PLC or the position controller Used to write programs to the ...

Page 30: ... 8 192 should be output to rotate the servo motor by 1 rotation The workpiece feed quantity is in proportion to the pulse number 3 1 2 Command pulse and feed speed When the servo motor encoder generates 8 192 pulses for one rotation the command pulse frequency speed 8 192 pulses s should be output to rotate the servo motor by 1 rotation per second Decrease the pulse frequency to rotate the servo m...

Page 31: ... parameters This operation pattern is effective during return to the zero point positioning and jog operation 3 1 4 Backlash correction function The positioning controller can output excessive pulses only when the movement direction is inverted so that the backlash of the mechanical system is corrected Parameter Acceleration time Actual acceleration time Parameter Deceleration time Actual decelera...

Page 32: ...ess Operation to return to the zero point The zero point return direction return speed deceleration time and creep speed are set by parameters in the positioning controller There are several zero point return methods For example when the forward end of the dog reaches the dog switch the motor resumes its creep speed At the first zero point signal after the dog reaches the backward end the deviatio...

Page 33: ...cumulated pulse quantity is almost constant During acceleration and deceleration the accumulated pulse quantity changes more dramatically When the accumulated pulse quantity becomes equivalent to or less than the specified quantity in position set value after command pulses have stopped the servo amplifier outputs the positioning completed signal The servo motor continues operation even after that...

Page 34: ... regenerative electric power of the servo amplifier 3 2 5 Dynamic brake function When a circuit inside the servo amplifier is disabled by a power interruption in the AC power of the main circuit or actuation of the protective circuit the terminals of the servo motor are short circuited via resistors the rotation energy is consumed as heat then the motor immediately stops without free run When the ...

Page 35: ...speed is Command pulse frequency from position controller c Either mm inch degree or pulse can be selected as the positioning command unit Accordingly when data such as the movement quantity per pulse positioning speed or the positioning address in accordance with the positioning command unit are set the pulse trains calculated inside the positioning controller are output for the target address an...

Page 36: ...ring quick feed should not exceed the maximum input pulse frequency of the servo amplifier a Maximum movement distance In each of the absolute and incremental methods the entire movement distance should not exceed the maximum pulse number of the positioning controller Movement quantity per rotation of motor Lead of ball screw mm rev Speed reduction ratio Number of rotations of motor Moving part sp...

Page 37: ...point is arbitrary 2 Incremental method In this method positioning is performed through specification of the movement direction and the movement quantity while the current stop position is regarded as the start point Address 100 Address 150 Address 100 Address 150 Address 150 Address 100 Address 300 300 Point C 150 Point B 100 Point A 0 Zero point Start point End point Movement quantity 100 300 Po...

Page 38: ...Positioning Control Components of Positioning Control and Their Roles 3 3 12 ...

Page 39: ...Positioning by AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control Advanced Positioning 4 ...

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Page 41: ...axis Speed Time Linear interpolation Linear interpolation controls two or more axes so that the start point and the end point target position are connected in the shortest way In this case the locus is linear Models applicable to 2 axis linear interpolation control FX 20GM E 20GM FX2N 20GM AD75P2 P3 AD75M2 M3 QD75P2 P4 QD75D2 D4 A171SH A172SH A173UH A273UH Models applicable to 3 or 4 axis linear i...

Page 42: ...s two or more axes so that the start point and the end point target position are connected with circular arc As there are innumerable number of arc locus connecting two points an auxiliary point the arc radius the center or the direction should be specified in addition to the start point and the end point to determine the circular arc Models applicable to 2 axis circular interpolation control FX 2...

Page 43: ...t starts from the start point it then continues at the specified speed until the stop command is input Applicable models FX 1PG FX2N 1PG AD75P1 P2 P3 AD75M1 M2 M3 QD75P1 P2 P3 QD75D1 D2 D3 A171SH A172SH A173UH A273UH Application examples Conveyor carrier unit roller feed crane etc Constant feed After start a workpiece moves by the specified constant quantity but the current value does not increase...

Page 44: ...ts The address for speed change can be determined in advance Applicable models FX2N 1PG FX 10GM FX 20GM E 20GM FX2N 10GM FX2N 10GM AD75P1 P2 P3 AD75M1 M2 M3 QD75P1 P2 P4 QD75D1 D2 D4 A171SH A172SH A173UH A273UH Application examples Conveyor carrier unit roller feed crane etc Constant speed control From the start point which is the current stop address positioning control is performed to the end po...

Page 45: ...ng executed positioning is controlled to the new end point address Applicable models A171SH A172SH A273UH Application examples Product follow up type application line and welding line Three dimensional interpolation control From the start point which is the current stop address 3 axis linear interpolation control and 3 axis circular interpolation control are performed to the end point address by w...

Page 46: ...Positioning Control Advanced Positioning 4 4 6 ...

Page 47: ... Positioning by AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control Actual Positioning 5 ...

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Page 49: ...n items required for the basic setup are as follows FX2N 20GM F2 422 CAB0 Communications cable FX 232AW C Converter FX 232 CAB 1 Communications cable Personal computer FX PCS VPS Win software 5 1 2 Comprehensive Set The demonstration items required for the comprehensive setup are as follows FX2N 20GM F2 422 CAB0 Communications cable FX 232AW C Converter FX 232 CAB 1 Communications cable Personal c...

Page 50: ...ence For this example we will use the basic setup of Personal computer and FX2N 20GM Let s draw the locus shown below driven by the X and Y axes simultaneously The output Y0 is added to imitate a pen or other end effector A Start point this point can be anywhere B 0 0 Zero point wait for 2 seconds C 80 100 Output Y0 turns ON wait for 2 seconds D 110 200 E 200 200 F 200 100 G 150 100 Output Y0 turn...

Page 51: ...mand to position C Here Y0 is turned on to mimic the use of an end effector tool This timer allows a tool to be activated or an operation executed This command is the start of a continuous steady path first using linear interpolation to position D To position E only the X axis need move For a smooth arc circular interpolation is used This example shows the start and end positions F as well as the ...

Page 52: ...the DRV Ret command for a DRVZ return to origin command Be sure to set up the plotter in accordance with the instructions and guidelines applicable to and supplied with your specific plotter Along with the Flow chart create a monitoring window similar to the one shown below All of the items on the monitoring window can be found under the insert tab on the main menu at the top of the screen Items i...

Page 53: ... from VPS copy these settings into your program The values for both the X and Y axes are the same for all parameters The system of units we will be using is both mechanical and motor so that the position can be controlled in mm deg 1 10 inch etc while the speed can be controlled by the number of pulses The system units should be set to mm and all other options left as default So that we can follow...

Page 54: ...settings do not require setting We do how ever need to reduce the Creep speed and the Zero return speed All of the parameter settings on this screen window can be left as their default values they are already optimized for our program If a plotter table is being used all of the above parameters will need to be checked before power ON or operation ...

Page 55: ...more space on the screen X axis and Y axis Monitor mode At first this window will be empty but as soon as you start your program the flow chart will appear and scroll through keeping the live instruction highlighted in red After minimizing the Sub task monitor window resize the Monitoring window and then the X axis and Y axis window Now you are ready to begin Firstly set the start point this can b...

Page 56: ...imilar to the one shown below the plot should be identical To run the program again set a new start position or let it start from where it is clean the plot area and press start If your plot does not look the same as the one above check your program against the one in section 5 2 1 If it does now is the time to experiment some more Try a new program perhaps include sub tasks and multiple flow char...

Page 57: ... 2 Positioning by AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control Product Line up 6 ...

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Page 59: ... controller FX 20GM FX2N 20GM Pulse output type for 2 axes Independent 2 axes or simultaneous 2 axes linear interpolation circular interpolation 2 axis position controller E 20GM Easy sequence function is provided Position controller can be used independently also 1 axis pulse output block FX2N 1PG FX sequence language Pulse output block for FX2N Series PLC Used as an extension block A Series 1 to...

Page 60: ...171UHCPU 512 I O points 4 axis control A172SHCPU 512 I O points 8 axis control A173UHCPU 2 048 I O points 32 axis control Servo amplifier 0 05 to 55 kw are dedicated to SSC net connection A273UH A3UCPU 2 048 I O points 32 axis control Servo amplifier 0 05 to 0 6 kw allow built in type also 0 05 to 55 kw are dedicated to SSC net connection Mechanical support language in motion controller Programmin...

Page 61: ... 2 axis position controller FX 20GM E 20GM FX2N 20GM FX1S FX1N Series PLC AD75P2 AD75M2 QD75P2 QD75D2 2 axis control 2 axis position controller FX 20GM E 20GM FX2N 20GM FX1S FX1N Series PLC AD75P2 AD75M2 QD75P2 QD75D2 3 axis control 3 axis position controller AD75P3 AD75M3 Combination of 1 axis position controller and 2 axis position controller For 1 axis control for 2 axis control Control of 4 ax...

Page 62: ... or less AD75P QD75P 1Mkp sec When the required command pulse is 1 Mpps or less AD75M A171SH A172SH A173UH A273UH Feedback pulse Feedback pulse To servo amplifier The position controller only outputs pulses and does not check feedback pulses Accordingly it is not confirmed whether or not rotation in accordance with command pulses is actually performed FX 10GM FX 20GM FX2N 1PG E 20GM FX2N 10GM FX2N...

Page 63: ...s available MR J2 J2S Series General purpose type in compact body easy to use Applicable to 50 w to 7 kw 100 VAC input type is offered as a series Real time auto tuning eliminates adjustment in setup Convenient test run function and diagnosis function are provided Applicable to low noise operation Setup software by personal computer is available MR H Series General purpose type of high performance...

Page 64: ...etermine the servo amplifier to be used in accordance with the servo motor model When the servo motor is determined in accordance with the purpose of use the rated torque and the inertia moment select a connectable servo amplifier while taking into account the responsibility and the extensibility 7kw or less Small capacity type servo amplifier MR J2 400w or less Extremely small capacity type servo...

Page 65: ...n and machine of low rigidity such as belt drive type because motor inertia moment is large Belt drive robot Mounter sawing machine X Y table food machine HC MF 8192P rev HC MFS 131072P rev 3000 50W to 750W Extremely small inertia and small capacity compatible with speed reducer Optimal to frequent operation directly connected to ball screw because motor inertia moment is small Inserter mounter bo...

Page 66: ... is restricted Robot Food processor Carrier unit Winder tension unit 2000 750W to 5kW Medium capacity HA LH 16384P rev 2000 11kW to 22kW Low inertia and large capacity Suitable to frequent positioning because motor inertia is low Press feeder injection molding unit Semiconductor manufacturing unit carrier line Press transfer unit Lifter automatic warehouse HA LF 16384P rev 2000 30kW to 55kW Large ...

Page 67: ...ing by AC Servo System 3 Components of Positioning Control and Their Roles 4 Advanced Positioning 5 Actual Positioning 6 Product Line up A Appendix A Tentative Selection of Motor Capacity Positioning Control Tentative Selection of Motor Capacity A ...

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Page 69: ...pacity at first while taking into account the following two points and determine the model The rated torque of the motor should be larger than the effective torque The load inertia moment should not exceed approximately 10 times of the inertia moment of the motor itself Positioning Control ...

Page 70: ...e calculation equation the torque during acceleration constant speed deceleration the cycle time and the machine load are as follows 1 The torque during acceleration is the torque required to reach the constant speed after startup and acceleration Torque during acceleration 2 Acceleration time Torque during constant speed 2 Constant speed time Torque during deceleration 2 Deceleration time Cycle t...

Page 71: ...d for deceleration and stop 4 How to obtain the cycle time The representative machine operation pattern consists of acceleration constant speed deceleration and rest The cycle time indicates the total time required for these actions Motor torque during constant speed Load torque TL TML Torque during deceleration Torque to decelerate load inertia moment Load torque TL Ta TMD ...

Page 72: ...on of the bearing A 1 2 Load inertia moment Difficulty to move a stationary object or difficulty to stop a moving object is called inertia moment As the inertia moment is larger the load is more difficult to move and stop In the servo motor the inertia moment gives considerable effect especially at the time of start and stop Accordingly calculate the load inertia moment then select a servo motor s...

Page 73: ...ed with this manual All examples and diagrams shown in this manual are intended as an aid to understanding the text not to guarantee operation Mitsubishi Electric will accept no responsibility for actual use of the product based on these illustrative examples Owing to the very great variety of possible applications users must satisfy themselves as to the suitability of each specific application ...

Page 74: ...MITSUBISHI DENKI BLDG MARUNOUCHI TOKYO 100 8310 TELEX J24532 CABLE MELCO TOKYO HIMEJI WORKS 840 CHIYODA CHO HIMEJI JAPAN JY992D89901A MEE0007 Effective July 2000 Specifications are subject to change without notice ...

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