FC 55 - Hydraulic Servo

 

The hydraulic servo function code defines startup, run-time, calibration, mode select, and failure mode specifications for the IMHSS03 Hydraulic Servo Module. This function code is used as an interface to the BRC-100 and HAC controllers. Individual block addresses are specified by this function code to provide position demand, calibration function and mode select parameters.

 

The function block has ten outputs. The outputs display valve position, module status, process control status, as well as the status of the components within the turbine control loop such as servo coil status and linear variable differential transformer (LVDT) status.

 

 

Outputs:

Blk

Type

Description

N

R

Percent or volts actuator position with quality

N+1

R

IMHSS03 D/A converter output with quality (expressed as % of span)

N+2

R

Servo 1 coil 1 output current in % or volts, with quality

N+3

R

Servo 1 coil 2 output current in % or volts, with quality

N+4

R

Servo 2 coil 1 output current in % or volts, with quality

N+5

R

Servo 2 coil 2 output current in % or volts, with quality

N+6

R

Module status

N+7

R

LVDT status

N+8

B

Module hardware status:

0 = good

1 = bad

N+9

B

Module communication and watchdog timer status:

0 = good

1 = bad

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

0

I

0 - 63

Module bus address of module

 

S2

N

0

I

0 - 5

Output device select:

0 = output 1 active servo output, output 2 unused

1 = output 1 unused, output 2 active servo output

2 = output 1 active servo, output 2 redundant servo output

3 = output 1 active servo, output 2 redundant servo at 20% standby

4 = output 1 active 4-20 mA I/H converter output

5 = output 1 active 20-160 mA I/H converter output

 

S3

N

0

I

0 - 4

LVDT select:

0 = input 1 LVDT, input 2 unused

1 = input 1 unused, input 2 LVDT

2 = input 1 primary LVDT, input 2 backup LVDT

3 = input 1 backup LVDT, input 2 primary LVDT

4 = input 1 LVDT I/H display only, input 2 4-20 mA contingency error monitor

 

S4

N

0

I

0 - 3

Output action on LVDT error:

0 = valve closes to 0% position:

0 V in servo mode

4 mA in 4-20 mA mode

20 mA in 20-160 mA mode

 

1 = valve opens to 100% position:

max V in servo mode

20 mA in 4-20 mA mode

160 mA in 20-160 mA mode

 

2 = valve remains at current position (I/H mode only)

 

3 = valve moves to null position (I/H mode only)

 

S5

N

1.0

R

0.0    or

0.4 - 15.0

LVDT frequency select in KHz:

0.0 = DC LVDT mode

 

S6

N

5

I

0 - 9998

Block address of the percent position demand

 

S7

N

5

I

0 - 9998

Block address of LVDT null check mode select:

0 = do not stop calibration at null point

1 = stop at null for primary LVDT

2 = stop at null for secondary LVDT

 

S8

N

6

I

0 - 9998

Block address of calibration stroke time select (in secs)

 

S9

N

6

I

0 - 9998

Block address of calibration cycles count (1.0 to 8.0)

 

S10

N

5

I

0 - 9998

Block address of calibration type select:

0 = full calibration. Record both 0% and 100% calibration values

1 = 0% calibration. Record only 0% LVDT value

2 = 100% calibration. Record only 100% LVDT value

 

S11

N

0

I

0 - 9998

Block address of calibrate mode enable:

0 to 1 transition = calibrate

 

S12

N

0

I

0 - 9998

Block address of calibrate GO/HOLD select:

0 = hold

1 = go

 

S13

N

0

I

0 - 9998

Block address of hard manual mode select:

0 = auto mode

1 = hard manual mode

 

S14

N

0

I

0 - 9998

Spare boolean block address parameter

 

S15

Y

0

I

0 - 3

Block output display units:

0 = output N in %, outputs N+2 to N+5 in %

1 = output N in volts, outputs N+2 to N+5 in %

2 = output N in %, outputs N+2 to N+5 in volts

3 = output N in volts, outputs N+2 to N+5 in volts

 

S16

Y

1

I

0 - 31

Demodulator gain constant: 0 = auto-tuning enabled

1 = 2.0                  12 = 36.3                 23 = 87.7

2 = 4.0                  13 = 40.0                 24 = 93.6

3 = 5.9                  14 = 44.0                 25 = 100.9

4 = 7.8                  15 = 48.8                 26 = 108.0

5 = 10.0                16 = 52.0                 27 = 118.0

6 = 11.8                17 = 54.9                 28 = 126.2

7 = 16.0                18 = 61.5                 29 = 132.0

8 = 21.1                19 = 64.2                 30 = 141.3

9 = 24.7                20 = 69.8                 31 = 152.0

10 = 28.3              21 = 72.0

11 = 32.0              22 = 78.6

 

S17

Y

1

I

0 - 31

Control gain proportional constant:

0 or 1 = 1.0             12 = 18.1                 23 = 43.8

2 = 2.0                     13 = 20.0                 24 = 43.8

3 = 2.9                     14 = 22.0                 25 = 50.4

4 = 3.9                     15 = 24.4                 26 = 54.0

5 = 5.0                     16 = 26.0                 27 = 59.4

6 = 5.9                     17 = 27.4                 28 = 63.1

7 = 8.0                     18 = 30.7                 29 = 66.0

8 = 10.5                   19 = 32.1                 30 = 70.6

9 = 12.3                   20 = 34.9                 31 = 76.0

10 = 14.1                 21 = 36.0

11 = 16.0                 22 = 39.3

 

S18

Y

-10.0

R

Full

LVDT 1 differential voltage at 0% actuator position

S19

Y

+10.0

R

Full

LVDT 1 differential voltage at 100% actuator position

S20

Y

-10.0

R

Full

LVDT 2 differential voltage at 0% actuator position

S21

Y

+10.0

R

Full

LVDT 2 differential voltage at 100% actuator position

S22

Y

5.0

R

0 - 100

Contingency deadband in %

S23

Y

0.0

R

Full

Spare real parameter

 

55.1  Explanation

 

55.1.1 Outputs

 

N

Percent actuator position with quality. This output displays actuator position read from the LVDT or position feedback device. Quality will be displayed as bad in the event of an A/D error, a bus transmission error, or an LVDT error (i.e., a primary or secondary error if using one LVDT, or error on both LVDTs when operating with redundant LVDTs). Otherwise, the quality will indicate good.

 

N+1

IMHSS03 D/A converter output. This output displays the D/A converter output value as a percent of span. This is the position demand signal feedback to generate an error signal. A hardware controller manipulates the error signal to produce the control output signal. This output value can be used as a guide to match to the BRC-100 position demand and bring the IMHSS03 module out of hard manual mode. Quality will be displayed as bad in the event of a D/A, A/D or bus transmission error. Otherwise, the quality will indicate good.

 

N+2

Servo 1, coil 1 control output. This output displays the IMHSS03 analog control output signal to servo valve 1, coil 1, expressed as a percent of span. Quality will be displayed as bad in the event of an A/D error, bus transmission error, shorted output, or opened output. The output is good quality otherwise.

NOTE: This output block will display a value of zero with good quality when defined as unused by S2.

 

N+3

Servo 1, coil 2 control output. This output displays the IMHSS03 analog control output signal to servo valve 1, coil 2, expressed as a percent of span. Quality will be displayed as bad in the event of an A/D error, bus transmission error, shorted output, or opened output. The output is good quality otherwise.

NOTE: This output block will display a value of zero with good quality when defined as unused by S2.

 

N+4

Servo 2, coil 1 control output. This output displays the IMHSS03 analog control output signal to servo valve 2, coil 1, expressed as a percent of span. Quality will be displayed as bad in the event of an A/D error, bus transmission error, shorted output, or opened output. The output is good quality otherwise.

NOTE: This output block will display a value of zero with good quality when defined as unused by S2

.

N+5

Servo 2, coil 2 control output. This output displays the IMHSS03 analog control output signal to servo valve 2, coil 2, expressed as a percent of span. Quality will be displayed as bad in the event of an A/D error, bus transmission error, shorted output, or opened output. The output is good quality otherwise.

NOTE: This output block will display a value of zero with good quality when defined as unused by S2.

 

N+6

Module status is converted into a real output as an integer with the bit map shown in Table 55-6.

 

 

 

Bits 0-1

Status of calibration or automatic tuning command.

 

0 = A calibration or automatic tuning is in process.

 

1 = The command has been correctly completed or the command has never been issued.

 

2 = An error has occurred during a calibration operation. It indicates one of three causes. The 100 percent voltage value was less than the zero percent voltage value for the LVDTs. An LVDT failure occurred during calibration. Refer to S17, S18, S19 and S20 for additional information on calibrationfailures.

 

3 = A demodulator gain auto-tune failure. If using redundant LVDTs, the LVDTs do not match and cannot be configured for redundant operation. The auto-tuning procedure has picked the best values for the primary LVDT as selected in S3. The backup LVDT is considered failed. Redundant LVDT operation is only available if the backup LVDT is replaced and the auto-tune procedure is performed again.

 

Bit 2

The servo outputs are bypassed (grounded) due to an I/O error that interferes with positioning. These errors include opened

and shorted LVDTs and DA errors.

Bit 3

Module mode. This output indicates the mode of the IMHSS03 module. A value of zero at this bit indicates automatic mode;

a one value indicates hard manual mode.

Bit 4

Contingency actuator positioning error. This bit is one if the measured actuator position deviates beyond an established

deadband from the position set point established in the IMHSS03 module. Otherwise, this bit value is zero.

Bit 5

A/D error. This bit value is one if the error is associated with the A/D converter on the IMHSS03 module. Otherwise, this bit

value is zero.

Bit 6

D/A error. This bit value is one if the error is associated with the D/A converter on the IMHSS03 module. Otherwise, this bit

value is zero.

Bit 7

DPRAM error. This bit value is one if a DPRAM error is detected on the IMHSS03 module. Otherwise, this bit value is zero.

 

 

N+7

LVDT status. The LVDT status is converted into a real output as an integer with the bit map shown in Table 55-7.

 

 

Bit 0

Active LVDT or position feedback device. This bit indicates which LVDT is being used to determine the percent actuator

position. A zero bit value indicates that input one is currently selected; a bit value of one indicates that input two is currently

selected. In the event of an error to both LVDTs in a redundant LVDT situation, this output will display the most recently

functioning LVDT.

 

Bit 1

LVDT 1 primary 1 status. This bit value will be one in the event of a primary failure of LVDT 1 (i.e., no signal present on either of the LVDT 1 secondary outputs). Otherwise, this bit value will be zero.

 

Bit 2

LVDT 1 secondary 1 status. This bit value will be one in the event of an LVDT 1 secondary 1 failure. Otherwise, this bit value will be zero.

 

Bit 3

LVDT 1 secondary 2 status. This bit value will be one in the event of an LVDT 1 secondary 2 failure. Otherwise, this bit value will be zero.

 

Bit 4

LVDT 2 primary status. This bit value will be one in the event of a primary failure of LVDT 2 (i.e., no signal present on either of the LVDT 2 secondary outputs). Otherwise, this bit value will be zero.

 

Bit 5

LVDT 2 secondary 1 status. This bit value will be one in the event of an LVDT 2 secondary 1 failure. Otherwise, this bit value will be zero.

 

Bit 6

LVDT 2 secondary 2 status. This bit value will be one in the event of an LVDT 2 secondary 2 failure. Otherwise, this bit value will be zero.

 

Bit 7

LVDT at null point. During calibration, this bit value is one when the 50 percent (null) valve position is reached for the selected LVDT or position feedback device. Otherwise, this bit value is zero. This bit is always a zero value during both turbine control and hard manual modes of operation.

 

 

N+8

Module hardware status. This output will display a one if the module has encountered a fatal error and stopped operation. Otherwise, a value of zero is displayed.

 

N+9

Module communication and watchdog timer status. This output will display a one if the communications between the module and the BRC-100 controller are lost. Otherwise, a value of zero is displayed.

 

 

 

55.1.2 Specifications

 

S1

Module bus address of the IMHSS03 Hydraulic Servo Module.

 

S2

Defines the type and configuration of turbine control valve which will be driven by the IMHSS03  module. There are six available options:

0 = One hydraulic servo valve connected to output 1. Servo 2 output currents (N+4 and N+5) will display a value of zero with good quality.

1 = One hydraulic servo valve connected to output 2. Servo 1 output currents (N+2 and N+3) will display a value of zero with good quality.

2 = Redundant hydraulic servo valves used, both with active control signals.

3 = Redundant hydraulic servo valves used, output 1 as primary and output 2 as secondary (20 percent standby signal).

4 = I/H converter mode (four to 20 milliamps) connected to output 1. Servo 2 output currents (N+4 and N+5) and servo 1 coil 2 output current (N+3) will display a value of zero with good quality.

5 = I/H converter mode (20 to 160 milliamps) connected to output 1. Servo 2 output currents (N+4 and N+5) and servo 1 coil 2 output current (N+3) will display a value of zero with good quality.

 

S3

Selects the position feedback input configuration to be used. Table 55-8 describes the available options.

 

 

 

S4

Defines the action to be taken in the event of total LVDT failure. Total LVDT failure is defined as a failure of one LVDT in a single LVDT configuration or both LVDTs in a redundant LVDT configuration.

If operating in the servo valve mode, this specification can be set to ground (outputs disabled) or output the maximum signal (100 percent) to the outputs in the event of a total LVDT failure.

 

NOTE: Control of the valve position is impossible without position feedback information.

 

The outputs are either grounded or driven to 100 percent to avoid large swings in the valve position due to control loss. The adjustment of the servo valve spool determines the speed in which the servo valve closes or opens. If 100 percent is selected, the outputs disabled light does not illuminate in the event of an error. If a total failure of the LVDT occurs, the output is driven based upon selection made in this specification. The options are as follows:

 

0 = Valve closes to a zero percent position. Grounded outputs in the servo valve mode are four milliamps in the four to 20 milliamp mode, or 20 milliamps in the 20 to 160 milliamp mode.

1 = Valve opens to 100 percent position. Outputs to maximum in the servo valve mode are 20 milliamps in the four to 20 milliamp mode, or 160 milliamps in the 20 to 160 milliamp mode.

2 = Valve remains at its current position. Control maintained. I/H mode only.

3 = Valve moves to a null position. I/H mode only.

 

In either mode, if the LVDT error is a failure of one secondary, the module can be calibrated to return to normal operation.

 

S5

LVDT frequency selected (in kilohertz) from 0.4 kilohertz to 15.0 kilohertz. If a DC LVDT is used, a value of zero must be entered for this specification.

 

S6

Block address of the percent position demand requested. Quality of the position demand block is ignored.

 

S7

Block address of the LVDT null mode selected. When this specification is set to one or two and calibration is enabled, the valve ramps to and holds at the LVDT null point for the primary or backup LVDT, respectively.

 

0 = Do not stop calibration at LVDT null point.

1 = Stop calibration operation at the null point of the primary LVDT.

2 = Stop calibration operation at the null point of the backup LVDT.

 

In servo valve mode, the LVDT null point is defined to be the valve position where the LVDT secondaries have equal voltage, usually close to a 50 percent valve position. In the I/H converter mode, the LVDT null point is the 50 percent output value (i.e., 12 milliamps for the four to 20 milliamp mode and 90 milliamps for the 20 to 160 milliamp mode).

 

S8

Block address of the calibration stroke time. This specification indicates the time in seconds for the valve to be driven from a zero percent actuator position to a 100 percent actuator position. Stroke times normally used for calibration are 30 seconds, 60 seconds, 35 minutes (2,100 seconds) and 70 minutes (4,200 seconds). Minimum stroke time is 30 seconds.

 

S9

Block address of the calibration cycles count. This specification determines the number of calibration cycles to be

performed during the calibration operation. The calibration operation can perform from one to eight cycles (1.0 to 8.0).

 

S10

Block address of the calibration type select. This specification selects whether a full calibration will be performed or only the 100 percent LVDT voltage or zero percent LVDT voltage will be recorded.

 

0 = Full calibration. Record both zero and 100 percent values.

1 = Zero percent calibration. Record only the zero percent LVDT value.

2 = 100 percent calibration. Record only the 100 percent LVDT value.

 

S11

Block address of the calibrate mode enable. A transition of this input block value from a zero to a one begins the calibration process.

0 = Do not calibrate or terminate calibration.

1 = Begin calibration (when tuned from a zero to a one).

 

S12

Block address of the calibrate GO/HOLD select.

0 = Hold. Pause calibration execution.

1 = Go. Execute calibration procedure.

 

S13

Block address of the hard manual mode select. Hard manual mode can be forced by setting this specification to a one. When this specification is reset to a zero, the module will return to automatic operation if the 0 - 9998 position demand (S6) equals IMHSS03 D/A output value (N+1).

 

S14

Spare boolean block address parameter.

 

S15

Selects whether the LVDT feedback (output block N) is displayed as a voltage or a percentage.

0 = Output N in percent, outputs N+2 to N+5 in percent

1 = Output N in volts, outputs N+2 to N+5 in percent

2 = Output N in percent, outputs N+2 to N+5 in volts

3 = Output N in volts, outputs N+2 to N+5 in volts

 

S16

Defines the demodulator gain constant used by the IMHSS03 module. This value can be zero or an integer from one to 31. If zero is selected, the IMHSS03 module automatically selects the optimal demodulator gain value based on the highest non-saturated demodulator gain value measured on the IMHSS03 module. If this option is selected, the optimal demodulator gain value is automatically written into S16. A non-zero number in this specification directs the IMHSS03 module to use the corresponding table value as the demodulator gain constant and the automatic tuning operation is not performed. Refer to the specifications table for the list of available gain constant values.

 

NOTE: If a change is made to the demodulator gain value, the proportional gain values must be adjusted (i.e., the user-selectable proportional gain values). Afterwards, an LVDT calibration must be performed.

 

S17

Defines the proportional gain constant used by the IMHSS03 module. The value shown in the specifications table is used as the proportional gain constant.

 

S18

LVDT differential voltage at zero percent actuator position for LVDT 1. This value is set by the operator or can be overwritten for both LVDTs automatically by performing a calibration operation.

 

S19

LVDT differential voltage at 100 percent actuator position for LVDT 1. This value is set by the operator or can be overwritten for both LVDTs automatically by performing a calibration operation.

 

S20

LVDT differential voltage at zero percent actuator position for LVDT 2. This value is set by the operator or can be overwritten for both LVDTs automatically by performing a calibration operation.

 

S21

LVDT differential voltage at 100 percent actuator position for LVDT 2. This value is set by the operator or can be overwritten for both LVDTs automatically by performing a calibration operation.

 

S22

Contingency deadband in percent. The contingency error bit indicates an error when the valve cannot be driven to the position demand plus or minus this contingency deadband.

 

S23

Spare real parameter.