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SRS Labs SIM960, Руководство по эксплуатации и обслуживанию

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2.1 PID Tuning Basics

2 – 3

www.thinkSRS.com

Stanford Research Systems

SIM960 Specifications

Control type
Proportional gain
Integral gain

Derivative gain
Offset
Bandwidth
Propagation delay
Noise (typical)
Parameter control
Parameter accuracy
Stability
Setpoint

External
Internal
Internal setpoint noise

Ramp

Amplifier output
Display resolution
Units
Operating temperature
Interface
Connectors

Power
Dimensions
Weight
Warranty

Manual
Control       

Output

P

ε

×

P

ε

×

+

−

×

 1

D

I

Offset
Control

Σ

Internal
Setpoint/Ramp
Generator

SP

M

Monitor Output
(rear panel BNC)

P

External
Setpoint
Input

Measure
Input

ε

 = SP 

− 

M

*

Output**
Selector

* Antiwindup circuitry (see text)
** Bumpless transfer when

 I

 is enabled

Output Buffer w/User 
Controlled Limits

Figure 2.1: The SIM960 block diagram.

process is noninverting, i.e. a small positive change at its input results
in a positive change at its output, then using positive

P

polarity will

ensure negative feedback in the loop. To see this, follow the e

ff

ect of a

small positive change at the process output. Since the process output
is connected to the

Measure

input of the SIM960, a small positive

change would cause a negative change to

ε

. The resulting change at

the controller

Output

would also be negative, as would be that of the

process output. Thus, the initial small positive change at the process
output is “corrected” by a negative change after going around the
feedback loop. As a general rule, if the process is noninverting, then
the

P

-polarity should be positive. If the process is inverting, negative

P

-polarity should be used.

Care should be taken in designing the process. The sensor should be
situated so that it is responsive to changes to the part of the system
under control. Placing the sensor too remotely can result in a time
delay which limits the quality of control. Also, the sensor should
primarily measure the system’s

response

to external changes, rather

than measure the changes directly. The latter can sometimes be used
to help the controller anticipate transients, but at the risk of sacrificing
accuracy in reaching the target setpoint.

Tuning a PID controller amounts to determining what the relative
contributions should be from each of the three types of control. The
simplest approach is to start with proportional control and add inte-

SIM960 Analog PID Controller

Содержание SIM960

Страница 1: ...ms Revision 2 3 October 10 2013 Distribution in the UK Ireland Lambda Photometrics Limited Lambda House Batford Mill Harpenden Herts AL5 5BZ United Kingdom E info lambdaphoto co uk W www lambdaphoto c...

Страница 2: ...returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this docu...

Страница 3: ...ning Basics 2 2 2 2 Ziegler Nichols Tuning 2 5 2 3 Anti Windup and Conditional Integration 2 7 2 4 Bumpless Transfer 2 8 3 Remote Operation 3 1 3 1 Index of Common Commands 3 2 3 2 Alphabetic List of...

Страница 4: ...ii Contents SIM960 Analog PID Controller...

Страница 5: ...ion of the SIM960 cannot lead to a con sequential failure of any interconnected equipment that could lead to loss of life or limb or property damage The illustrations charts and discussions shown in t...

Страница 6: ...ind on SRS Products Symbol Description Alternating current Caution risk of electric shock Frame or chassis terminal Caution refer to accompanying documents Earth ground terminal Battery Fuse On supply...

Страница 7: ...is manual are Front panel buttons are set as Button Adjust is shorthand for Adjust Adjust Front panel indicators are set as Overload Remote command names are set as IDN Literal text other than command...

Страница 8: ...Hz RTI Output Range 10 10 V Con guration Parameter control Digital Parameter accuracy 1 Stability 200 ppm C Display Resolution 4 digits Inputs Measure BNC 1 M 10 V range Ext Setpoint BNC 1 M 10 V rang...

Страница 9: ...1 General 1 2 1 2 Front Panel Operation 1 2 1 2 1 Inputs 1 4 1 2 2 Ramping 1 5 1 2 3 Connections 1 5 1 2 4 Bar displays 1 6 1 2 5 Restoring the default con guration 1 6 1 3 Rear Panel Monitoring 1 7...

Страница 10: ...pplications that do not use the I term Mathematically the behavior is Setpoint Measure 1 1 Output P I dt D d dt O set 1 2 where the three terms within the braces and O set can be indepen dently enable...

Страница 11: ...ent is indicated by its ash ing brightness Change the digit selection while Shift is high lighted There are two formats for the numeric display Exponential and xed decimal The format used for a partic...

Страница 12: ...setpoint can be supplied at the Setpoint BNC input When the internal setpoint is selected the BNC connector is disconnected from the SIM960 circuitry The Output BNC connector can be toggled between PI...

Страница 13: ...mp Start Stop again When the setpoint reaches the new pro grammed value the ramp automatically terminates and Internal stops blinking Note SP Ramp has no sign in the numerical display This is be cause...

Страница 14: ...ighted LEDs slightly separated roughly tracking the sine wave As the frequency is fur ther increased to well above the decay time inverse the two lighted LEDs no longer decay at all from their peak le...

Страница 15: ...SIM960 see Figure 1 2 Figure 1 2 The SIM960 rear panel 1 3 1 Error Monitor The upper BNC connector carries a bu ered copy of the P output of the error ampli er This output is always available even wh...

Страница 16: ...speci ed in Table 1 1 Direction Pin Signal Src Dest Description 1 SIGNAL GND MF SIM Ground reference for signal 2 STATUS SIM MF Status service request GND asserted 5 V idle 3 RTS MF SIM HW Handshake 5...

Страница 17: ...TXD directly to TD and similarly RTS RTS and CTS CTS In other words a null modem style cable is not needed To interface directly to the DB 9 male DTE RS 232 port typically found on contemporary perso...

Страница 18: ...LOW or PARI commands The maximum standard baud rate that the SIM960 supports is 38400 The minimum baud rate is 110 Above 38400 the SIM960 can be set to the following non RS 232 standard baud rates 625...

Страница 19: ...anced features of the SIM960 Analog PID Controller In This Chapter 2 1 PID Tuning Basics 2 2 2 2 Ziegler Nichols Tuning 2 5 2 2 1 Open loop tuning 2 5 2 2 2 Closed loop tuning 2 6 2 3 Anti Windup and...

Страница 20: ...cient D These signals as well as an O set are combined at a summing junction to produce the controller output see Eqn 1 2 Figure 2 1 shows a schematic representation of the SIM960 controller topology...

Страница 21: ...d to the Measure input of the SIM960 a small positive change would cause a negative change to The resulting change at the controller Outputwould also be negative as would be that of the process output...

Страница 22: ...utomatic reset for this reason Integral control simply integrates the error signal with respect to time Thus the controller output changes until the error has been reduced to zero near which point the...

Страница 23: ...ge in the control signal Call this time t 0 Record the process response in the Measure signal De ne the dimensionless process step response function h t Measure t Measure 0 Observe the point of maximu...

Страница 24: ...D mode with I and D both disabled Choose a value for Setpoint around the desired operating point and set P so some small value Slowly increase P until the process starts to oscillate Record this value...

Страница 25: ...e are a variety of anti windup strategies to mitigate this e ect A simple way to implement anti windup is to switch o the integrator whenever the output saturates This is not the same as resetting the...

Страница 26: ...utput level Were this not the case the integrator output would likely saturate while in manual mode and upon switching to PID Control mode the controller output would suddenly jump Bumpless transfer i...

Страница 27: ...Monitor commands 3 14 3 4 6 Display commands 3 16 3 4 7 Serial communication commands 3 17 3 4 8 Status commands 3 17 3 4 9 Interface commands 3 20 3 5 Status Model 3 25 3 5 1 Status Byte SB 3 26 3 5...

Страница 28: ...f 3 11 Integral Gain DERV f 3 11 Derivative Gain OFST f 3 11 Output O set Controller Con guration AMAN z 3 12 Output Manual Output PID Control INPT z 3 12 Input Internal External Setpoint SETP f 3 12...

Страница 29: ...3 18 Comm Error Status CESE i j 3 19 Comm Error Status Enable INCR i 3 19 Instrument condition register INSR i 3 19 Instrument status register INSE i j 3 19 Instrument status enable register ADSR i 3...

Страница 30: ...er ADSR i 3 19 A to D status register AMAN z 3 12 Output Manual Output PID Control APOL z 3 11 Controller Polarity B BAUD i 3 17 Baud Rate C CESE i j 3 19 Comm Error Status Enable CESR i 3 18 Comm Err...

Страница 31: ...Measure Input Monitor MOUT f 3 13 Manual Output O OCTL z 3 10 O set ON OFF OFST f 3 11 Output O set OMON i 3 15 Output Monitor P PARI z 3 17 Parity PCTL z 3 10 Proportional action ON OFF PSTA z 3 20 P...

Страница 32: ...3 6 Remote Operation TOKN z 3 24 Token Mode U ULIM f 3 13 Upper Output Limit W WAIT i 3 22 Wait SIM960 Analog PID Controller...

Страница 33: ...ace in a 32 byte Input Bu er Characters accumulate in the Input Bu er until a command terminator either CR or LF is received at which point the message is parsed and executed Query responses from the...

Страница 34: ...send or or as part of the command Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them with semi colons so long as the Input Bu er does not...

Страница 35: ...Each command is provided with a simple example illustrating its usage In these examples all data sent by the host computer to the SIM960 are set as straight teletype font while responses received the...

Страница 36: ...es the derivative control term DCTL OFF Example O set ON OFF OCTL z Set query the o set control to z OFF 0 ON 1 When ON the PID Control path includes the constant output o set OCTL Example ON Proporti...

Страница 37: ...5 105 INTG Example 1 5E 3 Derivative Gain DERV f Set query the derivative gain to f in V V s DERV may be set with 2 digits of resolution for 10 5 D 10 and with single digit resolution for 10 6 I 9 10...

Страница 38: ...e new value The allowed range is 10 000 SETP 10 000 SETP 1 234 Example Internal setpoint ramping ON OFF RAMP z Set query internal setpoint ramping to z OFF 0 ON 1 When ON the changes to the internal s...

Страница 39: ...el STRT START Example Manual Output MOUT f Set query the manual output value to f in volts The manual output can be set with millivolt resolution Note that setting MOUT does not modify whether the con...

Страница 40: ...es streaming of Setpoint data If i is speci ed then i measurements will be output at a rate of approximately two measurements per second If i is speci ed as 0 then measurements will be output inde nit...

Страница 41: ...peci ed then i measurements will be output at a rate of approximately half a second per measurement If i is speci ed as 0 then measurements will be output inde nitely The SOUT command can be used to s...

Страница 42: ...4 6 Display commands Select Field DISP z Set query the eld level to be displayed to z Allowed values of z are PRP 0 Proportional gain IGL 1 Integral gain DER 2 Derivative gain OFS 3 Output o set RTE...

Страница 43: ...ghout the transaction see the SIM900 manual discussion of the BAUD command for more examples BAUD 38800 Example Flow Control FLOW z Set query ow control to z NONE 0 RTS 1 XON 2 At power on the SIM960...

Страница 44: ...RE 5 Example 1 Standard Event Status ESR i Reads the Standard Event Status Register bit i Upon executing ESR the returned bit s of the ESR register are cleared GAIN 0 Example ESR 16 The binary value 1...

Страница 45: ...a ect the register INCR Example 16 Instrument status register INSR i Query the instrument status register bit i INSR Example 16 Instrument status enable register INSE i j Set query the instrument sta...

Страница 46: ...t to OFF PSTA Example OFF 3 4 9 Interface commands The Interface commands provide control over the interface between the SIM960 and the host computer Reset RST Reset the SIM960 to its default con gura...

Страница 47: ...pied to the Output Queue At power on CONS is set to OFF CONS ON Example Identify IDN Read the device identi cation string The identi cation string is formatted as Stanford Research Systems SIM960 s n...

Страница 48: ...ow the input bu er of the SIM960 see section 3 3 2 SETP 0 Example RATE 0 1 SETP 1 0 WAIT 5000 SMON 00 483159 Execution Error LEXE Query the last execution error code Valid codes are Value De nition 0...

Страница 49: ...ll parameter s 8 Parameter bu er over ow 9 Bad oating point 10 Bad integer 11 Bad integer token 12 Bad token value 13 Bad hex block 14 Unknown token IDN Example LCME 4 The error 4 Illegal set is due t...

Страница 50: ...nses to the TOKN query are ON and 0 At power on TOKN is set to OFF TOKN OFF Example Response Termination TERM z Set query the term sequence to z NONE 0 CR 1 LF 2 CRLF 3 LFCR 4 The term sequence is app...

Страница 51: ...RSTOP undef undef undef LLIMIT Instrument Status INSE INSR 7 6 5 4 3 2 1 0 INCR Figure 3 1 Status Register Model for the SIM960 Analog PID Con troller There are three categories of registers in the S...

Страница 52: ...e Input Bu er is empty and the command parser is idle Can be used to help synchronize SIM960 query responses ESB Event Status Bit Indicates whether one or more of the enabled events in the Standard Ev...

Страница 53: ...ommand that was successfully parsed Out of range parameters are an example The error code can be queried with LEXE CME Command Error Indicates a parser detected error The error code can be queried wit...

Страница 54: ...ushed and resets the command parser RTSH Unde ned for the SIM960 Command Error Indicates a parser detected error CTSH Unde ned for the SIM960 DCAS Device Clear Indicates the SIM960 received the Devic...

Страница 55: ...ed to indicate ramping is presently underway 3 5 8 Instrument Status INSR The Instrument Status Register consists of latching event ags that correspond one to one with the bits of the INCR see above U...

Страница 56: ...version Complete Indicates a new conversion result is available for EMON ADOUT Output Monitor Conversion Complete Indicates a new con version result is available for OMON While reading this register w...

Страница 57: ...s Chapter 4 1 Getting Ready 4 2 4 2 Performance Tests 4 2 4 2 1 Input Ampli er O set 4 2 4 2 2 A to D Converter test 4 2 4 2 3 Proportional Gain Accuracy 4 3 4 2 4 Derivative Gain Accuracy 4 4 4 2 5 I...

Страница 58: ...ld be taken not to constrict the ventillation holes in the SIM900 mainframe It should be located in a room with stable temperature preferably from 65 to 75 degrees F 4 2 Performance Tests The various...

Страница 59: ...displayed value is within 10 mV of 8 000 V Now disconnect the Output from the Measure input and ground the Measure input using a BNC grounding cap or 50 Ohm terminator Turn o I control using ICTL OFF...

Страница 60: ...rtional gain accuracy test Reset the SIM960 via the remote interface using RST Turn o the P gain control using PCTL OFF Turn on the D control using DCTL ON With the SR785 in swept sine mode and the so...

Страница 61: ...03 3 0 kHz 0 8488 5 104 100 kHz 0 6366 5 105 100 kHz 6 366 In each case the frequency response should be within 2 of the programmed gain value 4 2 6 Ramp Rate Accuracy To test the ramp rate wire the S...

Страница 62: ...e Output display at each level In each case the output display value should be within 5 mV of the programmed o set 4 2 8 Manual Output Accuracy Reset the SIM960 using RST Select Manual output using AM...

Страница 63: ...t schematics are included In This Chapter 5 1 Circuit Descriptions 5 2 5 1 1 Microcontroller 5 2 5 1 2 Front Panel Display 5 2 5 1 3 Input Ampli er 5 2 5 1 4 Proportional Integral Derivative 5 3 5 1 5...

Страница 64: ...based on a pattern from the controller Similarly U303 controls the eight lines from the LED cathodes using NPN open collectors Q309 through Q316 as output current bu ers 5 1 3 Input Ampli er The Meas...

Страница 65: ...nce zeroing the o set circuit U610 with U611 is equivalent to switching out the o set signal Note that R643 is placed in series with the feedback resistor R615 in order to roughly match the switch res...

Страница 66: ...d on to the output connector BNC without large start up transients Until switch U823 closes the SIM960 output is referenced to ground via R863 100k U820A provides a bu ered analog output of the P sign...

Страница 67: ...2 S403 S404 S405 2 00053 000 B3F 1052 D426 D447 D463 3 00425 060 RED S406 S407 S408 JP101 1 00302 010 6 PIN DIF CES U101 3 00903 124 MAX6348 JP103 1 00367 040 15 PIN D U102 3 01378 103 74HCU04 JP104 1...

Страница 68: ...505 Q802 3 00927 150 MMBT2907A U509 3 01364 120 OPA4277 Q801 3 01421 150 MMBT2222 U514 U512 3 01360 120 OPA228 R502 R507 R542 R547 4 01175 110 4 02K U601 3 01365 122 DG411DY R510 R533 R534 R819 4 0114...

Страница 69: ...age SIM960 Analog PID Controller Distribution in the UK Ireland Lambda Photometrics Limited Lambda House Batford Mill Harpenden Herts AL5 5BZ United Kingdom E info lambdaphoto co uk W www lambdaphoto...

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