51 Rod 431 Rotary This encoder has two output channels (U a1 and Ua2) which are Pulse Encoder phase shifted by 90°. The encoder has 1024 increments per revolution. Channel U a0 is a reference pulse which occurs once per revolution. When power is initially applied to the servomotor the drive will not know the exact position of the rotor. Rotor position can only be calculated within one revolution once the zero reference mark has been crossed the first time. Because synchronous servomotors must know rotor position within one revolution this encoder can only be used with 1PH7, 1PL6, and 1PH4 asynchronous servomotors. By comparing channel U a1 and Ua2 the drive can determine which direction the motor is running.
Transcript
51
Rod 431 Rotary This encoder has two output channels (Ua1 and Ua2) which arePulse Encoder phase shifted by 90°. The encoder has 1024 increments per
revolution. Channel Ua0 is a reference pulse which occurs onceper revolution. When power is initially applied to the servomotorthe drive will not know the exact position of the rotor. Rotorposition can only be calculated within one revolution once thezero reference mark has been crossed the first time. Becausesynchronous servomotors must know rotor position within onerevolution this encoder can only be used with 1PH7, 1PL6, and1PH4 asynchronous servomotors.
By comparing channel Ua1 and Ua2 the drive can determinewhich direction the motor is running.
52
ERN 1387/1381 The ERN 1387 encoder has four tracks and a reference pulse.Encoders A1 channel produces one sine signal per revolution and B1
channel produces one cosine signal. These signals are used todetermine exact rotor position from initial power up within onerevolution. After each revolution the calculated position isadjusted to the position indicated by the reference pulseposition, if necessary. This encoder is suitable for use with allSiemens synchronous and asynchronous motors.
The 1381 encoder is a two-channel device which does notproduce A1 and B1 signals. The 1381should be used only withasynchronous servomotors.
Tracks A and B on both encoders produce a sinewave output of2048 microperiods per revolution. Evaluation electronics withinthe MASTERDRIVE MC can increase the resolution to 16.8 x106 periods per revolution (ppr).
53
EQN 1325 Absolute- The EQN 1325 absolute value encoder is made up of twoValue Encoder sections. The outer ring is identical to the ERN 1387 and is used
to provide speed and direction information. Two outputchannels, A and B, produce 2048 periods per revolution.Channel B is offset from channel A by 180 degrees. The drivecan determine which direction the motor is running bycomparing channel A with channel B. A second feature of theEQN 1325 is the coded inner rings. These provide a uniquecode for 8192 positions. This unique code is sent to the drive viaan EnDat interface. The drive uses this unique code number todetermine rotor positon.
In addition, the encoder uses a mechanical gear sequence tocount up to 4096 revolutions and store them. As long as thedistance the application moves is less than 4096 revolutionsthere is no need to “home” the application as the absoluteposition is always known by the encoder count. As soon as itcounts 4096 revolutions the encoder starts counting again fromzero. These encoders are designed for use with synchronousand asynchronous servomotors.
54
Two-Pole Resolver A resolver is similar to an encoder, but instead of using aphotoelectric sensor a rotating transformer is employed. Theprimary is located on the rotor of the resolver. Two secondarywindings, arranged at right angles to each other, make up thestator. The amplitude of the sinewave induced into each statorwinding depends on the angular position of the rotor winding.Since the amplitude variations available at the stator windingsare 90° apart, one signal is called a sine signal and the other iscalled a cosine signal.
The sine signal and the cosine signal are both applied to theMASTERDRIVE MC. By comparing the two signals, theMASTERDRIVE MC can determine the angular position of therotor and its direction of rotation. Each revolution of the rotor isdivided into 4096 increments. Once the initial position of an axisis determined by finding a home position, exact position of anaxis will be tracked by the MASTERDRIVE MC over multiplerevolutions of the resolver. Two-pole resolvers are designed foruse with synchronous and asynchronous servomotors.
55
Pulse Width Modulation
Before discussing the MASTERDRIVE MC it is necessary toknow something about Pulse Width Modulation (PWM). Pulsewidth modulation is one type of technology used by AC drives,such as the MASTERDRIVE MC. PWM drives convert a fixedvoltage, fixed frequency into a variable voltage, variablefrequency output to control the speed of an AC motor. Pulsewidth modulation provides a more nearly sinusoidal currentoutput to control frequency and voltage supplied to an ACmotor than other technologies. PWM drives are more efficientand typically provide higher levels of performance than otherdrives. A basic PWM drive consists of a converter, control logic,and an inverter.
56
Converter The converter section consists of a either a fixed diode bridgerectifier or a thyristor bridge rectifier which converts the three-phase power supply to a DC voltage. The C1 capacitor(s)smooths the converted DC voltage by limiting current peaksand reducing harmonics. The rectified DC value isapproximately 1.35 times the line-to-line value of the supplyvoltage. For example, the rectified DC value is approximately650 VDC for a 480 VAC supply.
Control Logic Output voltage and frequency to the motor are controlled by theand Converter control logic and inverter section. The inverter section consists
of six switching devices. Various devices can be used such asthyristors, bipolar transistors, MOSFETS and IGBTs. Thefollowing schematic shows an inverter that utilizes IGBTs. Thecontrol logic uses a microprocessor to switch the IGBTs on andoff providing a variable voltage and frequency to the motor.
57
IGBTs IGBTs (insulated gate bipolar transistors) provide the highswitching speed necessary for PWM inverter operation. IGBTsare capable of switching on and off several thousand times asecond. An IGBT can turn on in less than 400 nanoseconds andoff in approximately 500 nanoseconds. An IGBT consists of agate, collector and an emitter. When the control circuit applies apositive voltage (typically +15 VDC) to the gate the IGBT willturn on. This is similar to closing a switch. Current will flowbetween the collector and emitter. An IGBT is turned off byremoving the positive voltage from the gate. During the off statethe IGBT gate voltage is normally held at a small negativevoltage (-15 VDC) to prevent the device from turning on.
Developing PWM There are several PWM techniques. It is beyond the scope ofWaveforms this book to describe them all in detail. The following text and
illustrations describe one method. An IGBT can be switched on,connecting the motor to the positive value of DC voltage (650VDC from the converter). Current flows in the motor. The IGBTis switched on for a short period of time, allowing only a smallamount of current to build up in the motor, and then switchedoff. The IGBT is switched on and left on for progressively longerperiods of time, allowing current to build up to higher levelsuntil current in the motor reaches a peak. The IGBT is thenswitched on for progressively shorter periods of time,decreasing current build up in the motor.
58
The negative half of the sine wave is generated by switching anIGBT connected to the negative value of the converted DCvoltage.
The voltage and frequency are controlled electronically bycircuitry within the AC drive. The fixed DC voltage (650 VDC) ismodulated, or clipped, with this method to provide a variablevoltage and frequency. At low output frequencies a low outputvoltage is required. The switching devices are turned on forshorter periods of time. Voltage and current build up in themotor is low. At high output frequencies a high voltage isrequired. The switching devices are turned on for longer periodsof time. Voltage and current build up in the motor increases.
59
Regeneration and Braking In the speed-torque chart there are four quadrants according todirection of rotation and direction of torque. Quadrant I isforward motoring or driving (CW). Quadrant III is reversemotoring or driving (CCW). Reverse motoring is achieved byreversing the direction of the rotating magnetic field.
The dynamics of certain loads, such as those associated withmany motion control applications, require four-quadrantoperation. Torque will always act to cause the rotor to runtowards synchronous speed. If the synchronous speed issuddenly reduced, negative torque is developed in the motor.This could occur, for example when a stop command is initiatedand the drive tries to slow down to bring the motor to a stop.The motor acts like a generator by converting mechanical powerfrom the shaft into electrical power which is returned to the ACDrive. This is known as regeneration, and helps slow the motor.A similar process occurs when coasting downhill in a car. Thecar’s engine will act as a brake. Braking occurs in quadrants IIand IV.
One method of dealing with negative torque and the current itproduces is controlled deceleration. Voltage and frequency isreduced gradually until the motor is at stop. This would besimilar to slowly removing your foot from the accelerator of acar. Many applications, however, require the motor to stopquicker, and the drive must be capable of handling the excessenergy produced by motor when this is done.
60
Braking Resistors Electrical energy returned to the drive from the motor duringregeneration can cause the DC link voltage to becomeexcessively high. Braking resistors are one method used tocontrol regeneration during a rapid deceleration. A brakingresistor is placed across the DC link, through an IGBT. Energyreturned by the motor is seen on the DC link. When the DC linkreaches a predetermined limit the control logic switches on theIGBT, completing the path from the negative to the positive DClink through the IGBT and resistor. Excess energy is dissipatedby the resistor, reducing bus voltage. When DC link voltage isreduced to a safe level the IGBT is switched off, removing theresistor from the DC link. This process allows the motor to actas a brake, slowing the connected load quickly.
61
Rectifier Regenerative Another method of dealing with excessive regeneration is withFront End a rectifier regenerative front end. Diodes in the converter
section are replaced with SCRs and a second regen bridge isadded. An SCR functions similarily to a dode rectifier, exceptthat it has a gate lead, which is used to turn the SCR on. Thisallows the control logic to control when the converter bridgeand regen bridge are turned on.
A simplified block diagram provides a clearer view of the regenprocess. When the servomotor needs motoring energy toaccelerate or maintain speed against the inertia of a load, theconverter bridge is turned on. When the motor is in theregenerative mode, it acts like a generator, supplying electricalenergy back to the DC link. When the DC link voltage reaches apredetermined level the motoring SCRs are switched off andthe regen (generating) SCRs are switched on. This allows theexcess energy to be returned to the AC line in the form of ACcurrent.
62
ACTIVE FRONT END An ACTIVE FRONT END (AFE) is another option available tocontrol regenerative voltage. With this option the diodes in theconverter bridge are replaced with IGBT modules and a CleanPower Filter. The IGBT, controlled by control logic, operates inboth motoring and regenerating modes. In addition, AFEprovides low stressing of the line supply. Harmonics areextremely low and the power returned is in the form ofsinusoidal current.
Review 51. The Rod 431 rotary pulse encoder can only be used
with ____________ servomotors.
2. The EQN 1325 absolute-value encoder can count up to____________ revolutions.
3. Braking occurs in quadrants ____________ and____________ .
4. ____________ ____________ ____________ is one typeof regenerative braking that uses IGBTs in the convertersection.
63
Siemens MASTERDRIVE MC Family
Siemens offers a broad range of AC drives, including theMICROMASTER, MIDIMASTER, and MASTERDRIVE families.The MASTERDRIVE family is further divided into vector control(VC) and motion control (MC). This section will focus on theMASTERDRIVE MC. These drives are specially designed forservo drive application. Drives are available from 0.55 kW to200 kW (0.75 HP to 270 HP). Selection and orderinginformation, as well as engineering information and dimensiondrawings, can be found in Part 1 of the General Motion ControlCatalog, available from your local Siemens sales representative.
The MASTERDRIVE MC family consists of Compact PLUS,Compact, and Chassis units.
MC Drive kW HPCompact PLUS 0.55 - 18.5 0.75 - 25
Compact 2.2 - 37 3 - 50Chassis 45 - 200 60 - 270
64
MASTERDRIVE MC Compact PLUS
Power Connections The following drawing is a layout illustration of a 4 kW CompactPLUS drive. X9, X100, X101, and X103 are control terminals foruser wiring. The main power supply (380 - 480 VAC) isconnected to X1. A feature of the drive is the X3 DC bus linkwhich allows for quick connection of one unit to another inmulti-drive configurations. Terminals are provided on X6 forbraking resistors and a precharge module. Programming is donewith the PMU keypad. The servomotor is connected to X2.Three slots (slot A, B, and C) are provided for option boards.
Programming and Acces is gained to the MASTERDRIVE MC for programmingOperating Sources operating parameters and motion profiles from the following
sources:
Operator Control Panel (OP1S)Parameterization Unit (PMU)Various Serial InterfacesPC Based Software (Simovis)
65
PMU and OP1S Parameters, such as ramp times, minimum and maximumfrequencies, and modes of operation are easily set. Thechangeover key (“P”) toggles the display between a parameternumber and the value of the parameter. The up and downpushbuttons scroll through parameters and are used to select aparameter value, once the “P” key sets the parameter. TheOP1S has a numbered key pad for direct entry. In the event of afailure the inverter switches off and a fault code appears in thedisplay. In addition the drive can be started, stopped, andreversed. The OP1S stores up to eight parameter sets.
Control Terminals The following schematic illustrates the control wiring of onecontrol board available for the Compact PLUS. The control unit(CU) is the “brains” of the drive. The control unit controls alldrive functions such as start, stop, acceleration, deceleration,motor voltage and frequency, monitoring, and other functions.
66
24 Volt Power Supply When the DC link is charged control voltage is supplied by aninternal source. In addition, a 24 volt power supply can beconnected to the drive. This enables parameterization andmonitoring of the unit even when the DC link voltage has beendischarged. The 24 VDC can be cascaded on AC - AC units viaterminals 33 and 34 of X100. X100 also provides a connectionto cascade a serial USS interface (RS485). Switch S1 is used toturn the USS interface on and off.
X101 Control Terminal There are four bidirectional digital inputs and outputs. These canbe programmed for various functions. Outputs, for example, canbe programmed to signal a run or stop condition. Inputs can beprogrammed as start/stop commands. There are two additionaldigital inputs, which can be used for high speed inputs with asampling time of 1 • s. There is one analog input and one analogoutput.
X103 Terminal An OP1S, PC, or other device can be connected to X103 serialport. An internal link to the USS RS485 interface makes itpossible to communicate with other devices which areconnected to the serial USS interface.
SAFE OFF SAFE OFF is a function that prevents unintended movement orrestarting of a drive after shutdown. This function is available asan option in Compact PLUS drives.
67
Rectifier Unit The rectifier unit can be used with one or more inverters.Rectifier units are available in 41, 120, and 230 amps. Mainpower is connected to X1. Rectified DC voltage (510 - 650 VDC)is supplied to connected inverters through X3. There are someadvantages to using one Compact PLUS rectifier unit to supplymultiple inverters:
• One drive in braking mode can regenerate energy via theDC link (X3) to supply energy to drives in motoring mode.
• Built-in braking chopper requiring only a resistor for excessregeneration.
• Less input line components. For example, main line torectifier as opposed to individual breakers and linerectifiers to each unit
Option Boards Up to three option boards can be installed in the Compact PLUSunit. The encoder board for the servomotor (closed-loop motioncontrol) must be plugged into slot C. An additional encoderboard for the controlled machine can be plugged into one of theother slots.
A B C
SBPSBR NP NPSBM
CBPCBC
SLB
EB1EB2
Preferred SlotPossible SlotNot Possible NP
Slot
Expansion Boards
SIMOLINK Board
Communication Boards
Encoder Boards
Option Boards
68
Encoder Boards The encoder board selected would depend on the encoder orresolver used with the servomotor or controlled machine. Amaximum of two encoder boards can be used with theCompact PLUS.
SBP The SBP is used to connect pulse encoders to thedrive. The SBP can also be used to monitor an externalencoder, such as might be connected to the drivenmachine.
SBR1 All normally available 2, 4, and 6-pole resolvers can beconnected to this option board.
SBR2 This encoder board is also used to connect a resolver.In addition, this board provides pulse-encodersimulation. This simply means that the SBR2generates 1024 pulses per resolver pole-pair.
SBM The SBM is used for sine/cosine encoders as well asabsolute value encoders.
Communication Boards There are a number of communication boards available for usewith the MASTERDRIVE MC. The CBP board is used to connectthe drive over the open field bus, PROFIBUS-DP. This protocolgives the MASTERDRIVE MC connection to all of Siemensautomation products for a totally integrated solution. Amaximum of two communication boards can be used.
SIMOLINK Board The SLB board is used for peer-to-peer communication withother drives via SIMOLINK. SIMOLINK is a high speed(11 mbaud) fiber optic ring bus that allows various data to bepassed from one drive to the next. When used withMASTERDRIVE MC, SIMOLINK provides the media forsynchronizing all MC drives on the ring. An application exampleof synchronized MASTERDRIVE MC drives used to controloffset printing can be found in the Applications section of thisbook.
69
Expansion Boards Expansion boards are used to expand the number of digital andanalog inputs and outputs. The EB1 board has three digitalinputs and four bidirectional digital I/O. Bidirectional I/O can beconfigured as a digital input or output. One of the analog inputsis used as a voltage or current reference input. Two of the analoginputs can also be configured as digital inputs.
The EB2 board has two digital inputs, one analog input, andone analog output. In addition, the EB2 has four relay contacts.Three of the contacts are normally open (NO) and one of thecontacts can be configured as normally open (NO) or normallyclosed (NC).
AC - AC (Converter) The terms AC - AC and DC - AC refers to methods ofconfiguring drives. AC - AC in the MASTERDRIVE MC familyrefers to a single drive, connected to an AC source, controllingan AC servomotor with an encoder or resolver.
I/O EB1 EB2
Digital Inputs 3 2BidirectionalDigital I/O
4 0
Analog Inputs 3 1Analog Outputs 2 1Relay Outputs 0 4Input for 24 V Power Supply
1 1
70
AC - AC Example The following example shows the concept of an AC - ACconfiguration. Three-phase power is applied to the drive throughthe main circuit breaker. A line contactor (Q1) connects/disconnects the system to/from the power supply. The linecontactor is controlled by an on/off switch connected to a 230VAC power supply. The 24 volt power supply, connected to X9,is required for maintaining communication and diagnosticswhen the supply voltage (380 - 480 VAC) is removed. An outputcontactor can be used to connect/disconnect the servomotorfrom the drive at U2, V2, and W2. Digital inputs/outputs areconfigured on X101. An OP1S operator panel can be connectedto X103. As an option, a capacitor module or brake resistor canbe added to absorb short-time energy peaks. A line filter can beincluded to further reduce RFI if local codes require.
71
DC - AC (Inverter) The MASTERDRIVE MC can also be configured so that one unitacts as a common DC bus (rectifier) for two or more ACinverters. In the following illustration, for example, one DC unit(rectifier) supplies DC power to two DC - AC units (inverters)through connector X3. The combined total output of theinverters must not be greater than the DC power supplied bythe rectifier unit. This is referred to as a common busarrangement. Multi-axis control is one situation where acommon bus arrangement would be used. This configurationallows for multiple axes to be connected to the same DC bus forsharing energy.
72
Common Bus Example The following drawing illustrates a multi-axis, common busUsing Compact PLUS setup. A single AC - AC can be used to further supply the DC
bus and 24 VDC control power of up to two additional DC - AC(inverter) units. This is due to an oversized input rectifier bridgeand internal power supply in the AC - AC unit. Multi-axissystems can be implemented in a compact and efficientmanner. If one axis is braked, the braking energy is fed back intothe DC link and made available to the other connected motors.Excess energy can further be reduced by means of an externalbraking resistor. In this example the “SAFE OFF” and capacitormodule options have been added.
73
MASTERDRIVE MC Compact and Chassis
The MASTERDRIVE MC compact and chassis drives have thesame features as the Compact PLUS. Drives are available asAC - AC and DC - AC. These drives can be configured for multi-axis control. Compact and chassis drives can be programmedand operated from the Operator Control Panel (OP1S),Parameterization Unit (PMU), and various serial interfaces.
Compact Drive The compact drive is available in four frame or enclosure sizes.The following drawing is a layout illustration of enclosure sizesA, B, and C. A larger enclosure is available for size D. The mainpower supply (380 - 480 VAC) is connected to X1. The DC link isavailable at X3. The servomotor is connected to X2.
74
Chassis Drive The chassis drive uses an open architecture for cabinetmounting. The following drawing illustrates enclosure sizes Eand F. A similar larger enclosure is available for size G.
Electronics Box The compact and chassis units have an electronics box forcontrol and option boards. There are up to six slots available formounting option boards in the electronics box. The slots aredesignated with the letters A to G. Slot B does not exist in thecompact and chassis units. An LBA (Local Bus Adapter) isrequired if mounting positions 2 or 3 are needed. In addition,adapter boards (ADB) are necessary for Slots D and E, and F andG when utilizing the half-size option boards.
75
CUMC Control Board The compact and chassis motion control drive uses the samemain control board (CUMC). The CUMC board is located in theelectronics box. Control wiring is the same for both drives.
X101 X101 is similar to the Compact PLUS. There are fourbidirectional digital inputs and outputs. These can beprogrammed for various functions. Outputs, for example, can beprogrammed to signal a run or stop condition. Inputs can beprogrammed as start/stop commands. There are two additionaldigital inputs, one analog input, and one analog output.
X103 X103 is two USS RS485 serial interfaces, which make itpossible to communicate with other connected serial devices.
X300 An OP1S or PC can be connected to X300 for programming.
76
Option Boards Up to six boards can be installed in the electronics box of thecompact and chassis units. The encoder board for closed-loopcontrol must be plugged into slot C. An additional encoderboard for the machine encoder can be plugged into one of theother slots. A maximum of two expansion boards, twocommunication boards, and two encoder boards can be used.
Maximum No. of Components in Electronics Box
A C F G D E
SBPSBR NP NP NP NP NPSBM
CBP NP NP
SLB
EB1EB2
Preferred SlotPossible SlotNot Possible NP
**Use Slot A or C with T100/T300
Mounting Position
Expansion Boards**
SIMOLINK Board
Communication Boards*
Encoder Boards
1CUMCCUR
3 2
Slots
Option Boards
* Use Slot G with T100/T300
77
Review 61. The maximum kW available in a Compact unit is
____________ kW.
2. The main power supply of a Compact PLUS isconnected to ____________ .
3. A 24 volt power supply can be cascaded on CompactPLUS AC - AC units from one drive to the next utilizingconnector X ____________ .
4. The preferred slot for the SBP encoder board is____________ .
5. The ____________ board is used to communicate withPROFIBUS-DP.
6. A single drive, that includes a rectifier and inverter inone unit, is referred to as a ____________ .
7. An ____________ is required if mounting positions 2 or3 are needed in the electronics box of a Compact orChassis unit.
78
Technology Options
Technology software is an option available with theMASTERDRIVE MC. Technology software can be divided intothree main categories:
• General Technology Functions
General technology functions include linear axis, rotaryaxis, and roll feeding.
• Positioning
Positioning includes point-to-point positioning or automaticpositioning which combines muliple point-to-point moves.
• Synchronous Operation
Synchronous operation involves the synchronizing of twoor more axes via electronics. Synchronous operationincludes electronic gears, cams, clutches, and so on.
79
Basic Function Software Some technology functions are readily available and can beimplemented at any time. These include cam control and brakecontrol.
Cam Controller A cam controller switches digital outputs on and off. With thisfunction external switching elements, such as pneumaticvalves, may be operated at defined points. Two cam controllersare available with the basic technology software. Each controllerhas two positioning cams, making a total of four cams whoseswitch-on and switch-off positions can be set independently ofeach other. Digital outputs from the MASTERDRIVE MC signalthe on/off position to the controlled equipment.
Brake Control Applying and releasing a brake can be effected by means ofexternal commands. However, with the brake control functionbuilt into the MASTERDRIVE MC braking can be fullyautomated without intervention by an external machine controlunit.
There are three ways to operate a brake:
• Relay Output on the EB1 Expansion Board
• Digital Output from the MASTERDRIVE MC to an ExternalRelay
• The Relay for Operating the Main Contactor in the Chassisand Compact Unit, when the Main Contactor is not used
80
Technology Software F01 The following position and synchronizing functions are softwareoptions that can be purchased with the MASTERDRIVE MC, orordered and enabled at a later date. They are part of thetechnology option software (F01) package.
Linear Axis Function The linear axis function is designed to traverse an object along aspecified range with fixed stops. A traversing car is an exampleof a linear axis.
Rotary Axis Function A turntable is an example of a rotary axis. The rotary axisfunction is designed to move an object the shortest distancearound a 360° path. Depending on where an object is, andwhere it must be moved to, the servomotor will turn the tableeither clockwise or counter clockwise.
Roll Feed This function works with a permanently rotating rotary axis andincorporates a cut-to-length function. A roll feeding into a cuttingmachine is one example.
81
Positioning The MASTERDRIVE MC drive has a positioning control systemcapable of executing a variety of positioning tasks such as:
• Setup - Manually jogging an axis into position withacceleration and speed determined by preset parameters
• Homing - Moving the axis to a predefined zero positionwith acceleration and speed determined by presetparameters
• Point-to-Point Positioning using Manula Data Input (MDI) -Moving the axis to either an absolute or relative position ata given speed and acceleration
• Roll Feed - Automatic cut-to-length feature useful forpresses, punching machines, and cross-cutters
• Automatic Mode - Automatic execution of completepositioning programs
Although the MASTERDRIVE MC may be operated in multiplemodes in a given application, understanding a basic applicationthat involves automatic mode and homing would be beneficialat this point. Since velocity versus time profiles are commonlyused to describe positioning applications, a simple example isprovided along with the explanation.
A velocity versus time profile provides a graphicalrepresentation of the velocity of an axis at any point in time.Velocity includes speed and direction. Speed in one direction isconsidered to be positive velocity and speed in the oppositedirection is considered to be negative velocity. Positive velocityis graphed above the time axis and negative velocity is graphedbelow the time axis.
82
In the following example the MASTERDRIVE MC controls thevertical movement of a drill. The drill will penetrate a compositematerial that has been moved into position.
The drilling sequence is:
Point A to B - From the home position, the drive is started andaccelerated to full speed. As the drill approached the workpieceit decelerates to 190 millimeters per second (mm/s).
Point B to C - The drill penetrates the hard top layer.
Point C to D - The drill is accelerated to 1000 mm/s to drillthrough the soft middle layer.
Point D to E - The drill is decelerated to drill through the hardbottom layer, then slows to zero at point E.
Point E to F - The drill is accelerated to -1500 mm/s (negativevelocity) while it is raised out of the workpiece and returned tothe home position at point F.
83
Electronic Cam The following illustration is representative of two sampleelectronic cam profiles available in the MASTERDRIVE MC.Electronic cam profiles are used to replace mechanical cams,and follow a specific cam pattern. The examples illustrate alinear axis coordinated with a rotary axis. Both axes arepositioned at a known reference position to run the cam profile.In this example the rotary axis is designated the master and thelinear axis is the slave. The slave axis (linear slider) will track themaster (black line on rotating cam). With the MASTERDRIVEMC, unlike a mechanical cam, the profile can be changed easily,almost “on the fly”. For example, sample profile 2 can replacesample profile 1.
Each angular position on the cam is assigned a position on theslider, creating a cam table like the following example.Mathematical interpolation is used to control the movebetween the points on the table. In sample profile 1, forexample, when the marker on the cam is 340° from the knowncam reference position, the slider marker is 20 mm from theknown slider reference position.
Electronic Gear Box The electronic gear box function can be used to replace amechanical gear box on a machine. In the following illustrationtwo axes are used to control the speed of two carousels. Onecarousel is the master and one is the slave. In this exampleempty paint cans are loaded onto the master carousel where afilling process is carried out. The cans are then transferred to theslave carousel where lids are applied.
In many applications such as this there must be a difference inspeed between the two processes. It may take longer, forexample, to fill the can than to apply the lid. With the electronicgear box function an electronic speed ratio exits between thetwo carousels. Increasing the speed of the slave carousel, forexample, will decrease the ratio. The ratio can be set anywherefrom ±32,767:32,767, allowing for precise gear ratioadjustments. It should also be noted that the speed of the entireprocess can be changed while maintaining a desired ratio. Forexample, once the process is running it may be desirable toincrease the process speed which will increase the production.
85
Electronic Clutch The electronic clutch function allows an axis to be engaged orEngage/Disengage disengaged without losing position synchronization. This is
particularly important when several parts of a complex machineare dependent on each other. In the following illustration, forexample, one axis controls an ejector. If a defective product isdetected the ejector is engaged for one cycle while the ejectorremoves the defective product. A second axis disengages(stops) the carousel for one cycle. At the end of the cycle theejector is disengaged and the carousel engaged.
If a missing object is detected on the infeed the electronicclutch disengages the slave axis for one cycle to allow the nextobject in line to be loaded into the slave axis. The clutch is thenengaged and the process is switched back to synchronousmode operation.
86
Print Mark Registration Print mark registration is used to compensate for creep, stretch,and thermal expansion of a printing operation. Registrationmarks are sensed within 1 • s, allowing for appropriatecompensation at each print roll and at the cutter. The slave’sposition is evaluated relative to the registration mark. Themotion control drives correct for any deviation. Without thiscorrection creep, accumulates with every revolution. This creepwould cause printing and cutting to be unsynchronized.
87
Cables
Power and encoder/resolver cables can be ordered by the meteror are available prefabricated with appropriate plugs andconnectors.
Power and encoder (feedback) cables have a maximumallowable length. Typically feedback cable length can be greaterthan power cable length (approximately 492 ft or 150 m). Thefollowing tables show the maximum power cable lengths.
Compact PLUS
Compact and Chassis
Output Unscreened Screened0.55 kW
Converters0.75 kW Inverters
328 ft (100 m) 229 ft (70 m)
1.1 kW - 18.5 kW 426 ft (130 m) 328 ft (100 m)
Output Unscreened Screenedup to 4 kW 164 ft (50 m) 114 ft (35 m)
5.5 kW 229 ft (70 m) 164 ft (50 m)7.5 kW 328 ft (100 m) 219 ft (67 m)11 kW 360 ft (110 m) 246 ft (75 m)15 kW 410 ft (125 m) 278 ft (85 m)
18.5 kW 442 ft (135 m) 295 ft (90 m)22 kW - 200 kW 492 ft (150 m) 328 ft (100 m)
88
Applications
There are any number of applications where motion control canbe utilized. The features and functions of the MASTERDRIVEMC product line provides appropriate solutions for theseapplication requirements. Choosing the right components canbe confusing and takes careful thought and planning. As youhave seen throughout this book there are a number ofservomotors, encoders, drives, and technology options to chosefrom. The following application examples, along with theselection flow chart in the next section, will help you in theplanning process. There are, of course, many applications otherthan the ones illustrated in this section appropriate for theMASTERDRIVE MC.
89
Offset Printing Offset printing traditionally uses a mechanical line shaft tosynchronize the different color print stations. The mechanicaldevices involved require high maintenace, and the system islimited in speed.
The mechanical line shaft system can be replaced withindividual servomotors which are precisely synchronizedthrough the MASTERDRIVE MC and SIMOLINK.Communication to higher level controls, such as a SIMATIC S7PLC, for evaluation of system status and drive setpoint signals,is accomplished with PROFIBUS-DP.
ApplicationRequirement
Web Handling with Synchronization
MASTERDRIVE MC Feature
Synchronization: Virtual Master, Real Master, Gear Box (Electronic Line Shaft)
MASTERDRIVE MC Solution/Benefit
Increased Accuracy and Production Print Speed. Flexibility to Add and Remove Print Stations with Minimum Downtime.
90
Bottle Filling Some bottle filling applications, such as cosmetics, require thedistance between the filling pipe and the liquid level in thebottle to be kept constant. In addition, the filling pump mustmaintain a constant flow. These two axes can be preciselysynchronized with the MASTERDRIVE MC.
In this application, the pump drive acts as the master and thefilling gantry acts as the slave. As the pump provides a constantflow of product, the filling gantry movement is synchronized,through a cam profile that corresponds to the bottle contour.This maintains a constant filling pipe to liquid distance.
ApplicationRequirement
2-Axis Synchronized Control
MASTERDRIVE MC Feature
Synchronization with Cam Profiling
MASTERDRIVE MC Solution/Benefit
Quick Cam Profile Change to Accommodate Bottle Contour Change. Increased Production for Multi-Product Line Runs.
91
Horizontal Bagging This application involves a continuous roll of foil for horizontalbagging. The sealing station handles the foil transport.Electronic line shaft and print mark registration ensure the foil issynchronized with the products being packaged. Electronic lineshafting also ensures the product feeder belt and the foil are incontinuous position synchronization. Print mark registration willaccelerate or decelerate the foil to make up for possible stretch.This ensures that printed labels on the foil will be correctlypositioned on the package.
The transverse sealing station must travel with the line in orderto achieve continuous packaging. This is accomplished with theMASTERDRIVE MC’s electronic line shaft and electronic camfunctions. The sealing station is accelerted with the electronicline shaft function to the speed of the product (x-axis). Theelectronic cam function closes the sealing jaws (y-axis) whilethe sealer moves across and simultaneously seals the package.
ApplicationRequirement
Continous Positioning and Synchronization.Continuous Packaging
MASTERDRIVE MC Feature
Print Mark RegistrationSynchronization: Electronic Line Shaft Control Including Cam Profile
MASTERDRIVE MC Solution/Benefit
Continous Adjustment to Compensate for Foil Stretch. Multi-Axis Coordination for Sealing and Bagging Sections.
92
Composite Drilling Positioning the x- and y-axis to locate the drilling tool can beaccomplished with the manual data input (MDI) mode. Once thedrilling tool has reached the desired location, the automaticfunction takes over and controls the movement of the z-axis.The following instruction set is an example of a drilling profile.
• Moving from A to B the drilling gantry rapidly traverses tojust in front of the board and starts to reduce the feedvelocity.
• At point B the drill reaches the reduced feed velocity todrill through a plastic laminate.
• Moving from B to C the drill slows to drill through thelaminate.
• Moving from C to D the drill increases to normal velocity todrill through core.
• Moving from D to E the drill reduces velocity to drillthrough bottom laminate.
• Moving from E to F the drill returns with increased velocity.
Application Requirement 3-Axis Positioning (Composite Drilling).MASTERDRIVE MC Feature
High Accuracy Drill Bit Placement and Optimized Drilling Speed to Improve Quality of Cut and Tool Life.
93
Cut to Length In Cut to Length applications, the purpose is to cut material to aRotary Knife/Sheater precise length. For a fixed cut length, and a knife circumference
of the same length, it is simply a matter of maintaining aconstant speed between the web and the knife. However, forproducts that require various cut lengths, the knife’scircumference would have to vary to match these new cutlengths. Since this would not be practical, the knife speed isoften profiled. By varying the knife speed various cut lengthscan be obtained. Furthermore, the rotary knife is accelerated sothat as the cutting edge comes into contact with the material itis traveling at the same velocity. This is done to avoid “ripping”the material.
To accomplish this task a Cam profile is often employed.Using the technology features of the MASTERDRIVES MC, anumber of cam profiles can be created to perform the neededcontoured movement that is synchronized with the material toperform the cut.
ApplicationRequirement
Variable Speed and Product Cut Lengths.
MASTERDRIVE MC Feature
Synchronization with Cam Profiling
MASTERDRIVE MC Solution/Benefit
Short Current Rise Time allows for High Dynamic Response. Multiple Cam Profiles Allow for Quick Changeover to Various Product Lengths.
94
Pick and Place Pick and Place applications involve the precise movement ofproduct from one location to another. Using the Point-to-Pointpositioning features (MDI mode) of the MASTERDRIVES MC,this precise movement can be realized. Typically the gripperclaw is “homed” to the starting location during initialization ofthe system. From that point, as product is sensed, the grippercloses on it and the Point-to-Point move is made. Once the finaldestination point is reached the gripper releases the productand the return move to home position is carried out. SIMOLINKis the perfect choice to coordinate these actions. It allows foreasily sending all of the appropriate status and control signalsfrom one axis drive to the next.
ApplicationRequirement
Pick and Place Positioning
MASTERDRIVE MC Feature
MDI Point-to-Point Positioning
MASTERDRIVE MC Solution/Benefit
High Accuracy Organization and Location of Product Packaging
95
Selection
The following flow diagram, along with Part 1 and Part 2 of theGeneral Motion Control Catalog, will help you select the rightequipment for your motion control system.
96
97
SIMODRIVE
In addition to the MASTERDRIVE MC, Siemens offers additionalgeneral motion control products. Two examples from theSIMODRIVE family of servodrives are described in the followingparagraphs.
POSMO A The SIMODRIVE POSMO A is an integrated motion controlsystem. POSMO consists of a motion control drive, servomotor,gearbox, and incremental position transducer in one unit.POSMO can be integrated into any PROFIBUS-DP environment.Its only requirement is 24 VDC and PROFIBUS for programmingand control. The unit can even act as a stand alone unit byprogramming it over PROFIBUS and utilizing two digital inputsto perform various position moves.
POSMO Data Degree of Protection IP54Voltage 24 VDC ±20%Power 62 WGear Drive 4.5:1 to 162:1
98
SIMODRIVE 611 Universal The SIMODRIVE 611 Universal is a closed-loop control plug-inunit. The 611 Universal is made up of an infeed module anda power module. The infeed module contains a completeelectronics power supply and is used to convert the incomingAC line (400 to 480 VAC) to DC. The power module houses the611 Universal and provides the output to the servomotor. The611 Universal will support 1 or 2 axis. Like the POSMO,the SIMODRIVE 611 Universal can be integrated intoany PROFIBUS -DP environment. This drive is rated from 3 - 250amps. It is designed for positioning tasks and can operate bothsinewave servomotors and linear motors.
Review 71. Which of the following is not part of the basic function
software?
a. Cam controllerb. Brake controlc. Electronic Clutch
2. The gear ratio of the electronic gear box function can beset anywhere from ± ____________ .
3. Registration marks are sensed within ____________ • swith the print mark registration function.
4. The maximum screened cable length of a 5.5 kWCompact unit is ____________ ft.
5. When selecting a motion control system the speed and____________ load cycles must be known.
99
Review Answers
Review 1 1) MASTERDRIVE; 2) linear, rotational; 3) h.
The final exam is intended to be a learning tool. The book maybe used during the exam. A tear-out answer sheet is provided.After completing the test, mail the answer sheet in for grading.A grade of 70% or better is passing. Upon successfulcompletion of the test a certificate will be issued.
Questions 1. ____________ is a twisting or turning force that causes an object to rotate.
a. Torque c. Inertiab. Friction d. Acceleration
2. Ideally it is desirable to have a ____________ ratiobetween the load and the motor.
a. 1:2 c. 2:1b. 1:1 d. 2:2
3. The torque required to accelerate a system with a totalinertia of 0.010 kgm2 from rest to 2500 RPM in 0.1seconds is ____________ Nm.
a. 7.85 c. 26.17b. 13.08 d. 32.56
4. ____________ is a Siemens PC program designed toaccelerate the process of calculating speed, torque,and inertia of a motion control system.
a. SIMOLINK c. SimoSizeb. PROFIBUS-DP d. POSMO
5. The maximum temperature rise of a motor with ClassF insulation, not including the margin for a hot spot,is ____________ K.
a. 80 c. 130b. 125 d. 105
101
6. A motor with an enclosure that protects against dustand water jets would be classified asIP ____________ .
a. 23 c. 68b. 55 d. 65
7. ____________ is a duty cycle which operates for anintermittent period without starting between cycles.
a. S1 c. S2b. S3 d. S4
8. Winding version ____________ is rated for 6000 RPM.
a. A c. Fb. G d. K
9. The range of rated torque of a 1PH7 motor is____________ Nm.
a. 22 - 1145 c. 370 - 1720b. 0.8 - 16.5 d. 34 - 78
10. The ____________ encoder has 8192 coded positionsand uses a mechanical gear sequence to count up to4096 revolutions.
a. Rod 431b. ERN 1381c. ERN 1387d. EQN 1325
11. ____________ is a method of braking which usesIGBTs in the converter section and provides sinusoidalregen current back to the incoming power supply.
a. ACTIVE FRONT ENDb. Rectifier Regenerative Front Endc. Pulsed Resistor Brakingd. Pulse Width Modulation
12. The maximum kW rating of a Compact PLUS dirveis ____________ kW.
a. 15 c. 18.5b. 22 d. 37
102
13. The Compact PLUS has ____________ programmablebi-directional inputs and outputs.
a. two c. fourb. three d. six
14. Up to ____________ option boards can be installed inthe Compact PLUS.
a. two c. fourb. three d. six
15. ____________ is an encoder board used for sine/cosine encoders as well as absolute value encoders.
a. SPB c. SBR1d. SBR2 d. SBM
16. ____________ refers to a system in which one rectifiersupplys DC power to multiple AC inverters.
a. Multi-Axis c. PROFIBUS-DPb. SIMOLINK d. Common Bus
17. ____________ is the preferred slot for an encoder boardin the Compact PLUS, Compact, and Chassis drives.
a. A c. Cb. B d. D
18. The Cam controller is part of the ____________ .
a. basic function softwareb. rotary axis functionc. linear axis functiond. Roll feed function
19. The maximum length of a screened cable used on a0.55 kW converter is ____________ meters.
a. 35 c. 65b. 50 d. 70
103
20. ____________ is a type of motion control drive that hasan integrated motion control drive, servomotor, gearbox, and incremental position transducer is one unit.
a. SIMODRIVE 611 Universalb. POSMOc. Compact PLUSd. PROFIBUS-DP
