PROACT DIGITAL SPEED CONTROL SYSTEM FOR MODELS I & II - Caterpillar

Introduction

Because of the variety of installations, plus system and component tolerances, the control must be tuned to each system for optimum performance.

This chapter contains information on control calibration. It includes initial prestart-up and start-up settings and adjustments.

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An improperly calibrated control could cause an engine overspeed or other damage to the engine. To prevent possible serious injury from an overspeeding engine, read this entire procedure before starting the engine.

Using the Hand Held Programmer

The Hand Held Programmer is a hand-held terminal, powered by the ProAct control. The terminal connects to the RS422 D connector port on the control. Firmly seat the connector on the terminal into J1. Control boxes are equipped with a cover which must be removed to access the J1 receptacle and the two other terminal strips.

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The hazardous environment specifications for the control are compromised when the cover is removed.

When power is applied to the terminal by plugging it into the control, it performs a power-up self-test. Upon successful completion of the self-test, the screen will remain blank. Press the "ID" key to display the part number and revision level of the software in the control. Refer to this number and revision level in any correspondence with Woodward Governor Company.

The screen on the programmer will display four lines of information, two lines from two different menus. This means that two menus can be accessed at the same time. Only one menu will accept changes at a time. This menu will be identified on the screen by a flashing initial character.

The set points or adjustments of the control are arranged in seven menus. You access the menus with the number 1 through 6 and 0 keys. The number keys are used only to enter a menu.

Step through Menu selected with Left and Right arrows.

All changes in the menu items are made with the Rabbit and Turtle Up and Down keys. The Rabbit Up and Down increases or decreases the set point rapidly. The Turtle up and down increases or decreases the set point slowly. All keys repeat when held down.

Changes recorded in the menus may be lost should the ProAct control be "powered down." Push the "SAVE" button to permanently record changes before leaving a menu.

Toggle between the upper two line menu display and the lower two-line menu display with the middle up/down arrow key.

An inactive menu may be removed from the display screen by pressing the minus (-) key. (This is the only function of the minus (-) key.)

The black square key will clear the error log from the programmer.

The ID key displays software part number, and revision. Use this information when contacting Woodward Governor Company or a Service Facility.

(Only the keys listed above are used. Other keys are not used.)

Figure 4-9. Hand Held Programmer

Proact Governor Menus

Menu 1 - Dynamics Settings

Menu 2 - Alternate Dynamics Settings

Menu 3 - Speed Reference Settings

Menu 4 - Limiter Settings

Menu 5 - Monitor Menu

Menu 6 - Configuration Set Points

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The Failsafe Function must be enabled during normal engine operation to prevent possible overspeed should the MPU signal be lost for any reason. The function is overridden to allow some slow cranking engines to start, and to test parts of the governor system without running the engine. Failure to enable the Failsafe Function could allow overspeed with resulting damage to equipment and possible personal injury or death.

Menu 0 - Error Menu

Configuration may be viewed at anytime. To change a menu entry engine speed on Menu 5 must read "0" and the Run/Stop switch must be open. The entry code must be increased from "0" to "49" before changes can be made to Menu 6.

Description of the ProAct Digital Speed Control Set Points

Menu 1 - Dynamics Menu

The four Gain set points and break points determine the actuator response to a change in speed or load. These settings can vary as a percent of existing load in nonlinear fuel systems. The adjustments are settings that affect the stability and transient performance of the engine. A large number will provide a faster response to an error between actual speed and reference speed. A small number will provide a slower response to an observed error in speed.

Gain becomes an important portion of the programming that determines the response and stability of an engine.

There are two sets of dynamics provided. Menu 1 sets the primary dynamics. Menu 2 provides a second set of dynamics for use with an alternate fuel or other conditions which require different control factors.

The set of dynamics being used is selected by the Alternate Dynamics contact input (open for normal dynamics and closed for alternate dynamics.)

The following descriptions apply to either set. See Figures 5-1, 5-2, 5-3, and 5-4.

The four Gain and Gain Breakpoint settings in Menus 1 and 2 provide different response scales to changes in load or speed depending upon the existing actuator position. This allows the ProAct control to be programmed to provide a response scale that matches the engine response over the no load to full load range.

Figure 5-1. Non-Linear Valve Power Curve

Gas Engine Setup

Change in the butterfly-valve position is not linear in comparison to engine power output. In naturally aspirated (non-turbocharged) engines, the position of the valve in comparison to engine output appears on a chart similar to Figure 5-1.

Turbo-charged engines distort this curve, particularly as turbo pressure builds to the point of operating the waste gate. A turbo-charged gas engine will likely have a butterfly position chart similar to Figure 5-3.

Note in both charts that valve position falls on a curve. The ProAct menu does not permit the construction of a curve. However, with four slope segments available, a rough approximation of the curve can be created. See Figure 5-4.

Diesel Engine Setup

Most Diesel engine fuel controls are nearly linear. The dynamics maps may still be used to accommodate nonlinear conditions caused by either the fuel system or by linkage between the actuator and the rack. For gain settings that are not used, set the associated Breakpoint at 100%.

Figure 5-2. Typical Transient Response Curves

Menu 1 Dynamics

Control Gain Programming Steps

1. Gain programming is needed whenever the gain of the engine and fuel system is non linear. This usually occurs in gas engine applications. A plot of the fuel system must be determined to properly adjust the gain of the control to match the gain of the system at all loads.

The plot reflects the actuator output, as seen in Menu 5, versus the engine load as load is varied from no load to full load.

Figure 5-3. Sample Engine Plot

TO CONSTRUCT A GAIN PLOT:

a. Set the Gain A breakpoint for 100%. This ensures that there won't be any confusion with other settings while plotting the system characteristics. Only Gain A, Stability, and Actuator compensation will be used.

b. Start the engine and obtain good control at no load using Gain A, Stability, and Actuator Compensation. Record these settings and the actuator output as displayed in Menu 5.

c. Step load the engine with as many load steps as are practical. At each load step Gain A may need to be varied to maintain engine stability. Do not change stability or actuator compensation after the first setting in Step b. Should it be necessary to change these settings to obtain good control repeat all previous steps until only Gain is changed at each load step. At each load step, record the actuator output that is displayed in Menu 5. Also record the engine load and Gain A at each point.

Figure 5-4. Linearized Engine Plot

The table on the next page aids in collecting the date for the Gain Plot.

Gain settings reflect the amount of slope as shown in Figure 5-3. Flat portions of the engine plot will require relatively small amounts of gain, steep portions of the plot will require larger gain numbers.

d. Create a plot of the system by plotting actuator output as a function of load. A typical result is shown in Figure 5-3.

The following table can be completed to aid in the construction of the plot. Use as many load steps as possible.

Figure 5-5. Example of Plot Created from GAIN Column

Figure 5-6. Example of Engine Plot Created from Actuator Output Column

2. Set Gain A to the value recorded in Step 1b. This should give you good control at no load.

3. Use the plot of the engine to determine the linearity of the fuel system. This curve should be linearized between inflection points as shown in Figure 5-4.

4. Set the Gain A Breakpoint for the actuator output at or slightly below the value at the first inflection point. The gain of the electronics is constant for actuator outputs less than the Gain A Breakpoint.

5. Set the Gain B Breakpoint at the point slightly above the first inflection point in the actuator output versus load plot.

6. Gain B should now be adjusted to obtain good control at the inflection point. Note: you may already have obtained the correct value in Step 1c.

7. Set the Gain C Breakpoint slightly below the next inflection point in the curve obtained in 1d.

8. Gain C should now be adjusted to obtain best control at this point. Note: the correct value for Gain C may already have been obtained in Step 1c for this load.

9. Gain D breakpoint is normally higher than the second inflection point. The gain of the control is constant after this point.

10. Gain D is adjusted for the best response at full load. This value may also have been determined in Step 1c.

11. A Gain curve from the engine plotted in Figure 5-7 would look similar to

Stability, Actuator Compensation, Gain Ratio, Window Width

12. Stability compensates for the lag time of the engine. It adjusts the time required for the control to return the speed to zero error after a disturbance. Stability is adjusted to prevent slow hunting and to minimize speed overshoot after a load disturbance.

13. Compensation compensates for the actuator and fuel system time constant.

14. Gain Ratio operates in conjunction with the Window Width and Gain adjustments by multiplying the Gain set point by the Gain Ratio when the speed error is greater than the Window Width. This makes the control dynamics fast enough to minimize engine speed overshoot on start-up and to reduce the magnitude of speed error when loads are changing. This allows a lower gain at steady state for better stability and reduced steady-state actuator movement. A low number will provide closer control and less stability.

15. Window Width is the magnitude (in ± rpm) of a speed error at which the control automatically switches to fast response. The control does not use the absolute value of speed error, but "anticipated" speed error to make this switch. This method provides for quick switching to the high gain value when an off speed occurs and early switching to the low gain value when recovering from the speed transient. This provides smoother switching than if the absolute speed error was used for the window. A lower number will provide closer control with less stability.

Menu 2 - Alternate Dynamics

Menu 2 should be programmed as was Menu 1 but with the alternate fuel or other operating condition expected. The four Gain settings and breakpoints may be exactly like those used in Menu 1. The Stability, Compensation, Gain Ratio and Gain Window will probably be quite different if different fuels are being used.

If the engine will not use the alternate operating condition the menu will not have to be programmed or it can be programmed identically with the Menu 1 to prevent unintentional change in the dynamics program.

Menu 3 - Speed Reference Setting And Response Menu

Speed adjustments are the settings that affect the speed reference. Descriptions of each menu item follow.

1. Rated Speed Reference sets the normal operating speed of the engine in RPM.

2. Idle Speed Reference sets the speed in RPM at which the engine is operated at start-up. It sometimes is used during cool down.

3. Raise Limit is the maximum speed reference setting in RPM. It is used to limit the Raise Speed command and Remote Reference to a maximum. It normally is set at the maximum rated engine speed.

4. Lower Limit is the minimum speed reference setting in RPM. It is used to limit the Lower Speed command and Remote Reference. It normally is set at the minimum operating speed of the engine.

Figure 5-7. Accel/Decel Example

5. Accel Time is the time required for the control to ramp the engine speed from Idle speed to Rated speed. The time is set from 0 to 500 seconds. The ramp is started whenever the Idle/Rated switch is closed.

6. Decel Time is the time required for the control to ramp the engine speed from Rated speed to Idle speed. The time is set from 0 to 500 seconds. The ramp is started whenever the Idle/Rated switch is opened.

NOTE: Actual engine deceleration may be slower than set by the Decel Time set point. This occurs when the Decel Time set point is faster than system inertias will allow the engine to come down in speed. This condition is indicated by the control actuator output going to the minimum fuel position. See Idle Droop below.

7. Raise Rate is the rate at which the speed reference is ramped when using the Raise command or when the Remote Speed Setting input is changed in the increase direction. The rate programmed is in RPM per minute. A step change in the remote input does not cause an immediate change in the reference, which is ramped to the new setting at the Raise Rate.

8. Lower Rate is the rate at which the speed reference is ramped when using the Lower Speed command or when the Remote Speed Setting input is changed in the decrease direction. The rate is set in RPM per minute. A step change in the remote input does not cause an immediate change in the reference, which is ramped to the new setting at the Lower Rate.

9. 20 mA Remote Reference is the engine speed desired when 20 mA is applied to the Remote Speed Reference input. The desired speed is set in RPM.

10. 4 mA Remote Reference is the engine speed desired when 4 mA is applied to the Remote Speed Reference input. The desired speed is set in RPM.

Figure 5-8. Droop Curve

11. Droop is set as the percent rated speed will be decreased from no load to full load. Droop will be included in the engine control schedule only when the droop/isochronous contact is open.

The percentage entered is based on 75° of actuator travel. If less than full travel is used droop percentage must be increased proportionally.

12. Idle Droop combined with the Idle Droop Breakpoit is used to limit speed undershoot when large decel rates are used from Rated to Idle

Idle Droop is based on the actuator output when it drops below the Idle Breakpoint setting. Dependencies on linkage make the Idle Droop percentage relative, so large droop settings may be required to achieve the desired results.

Figure 5-9. Idle Droop

13. Idle Droop Breakpoint is normally set equal to the actuator output obtained when the engine is unloaded and at low idle. When the output of the control drops below this setting or goes to minimum fuel during rapid engine deceleration, Idle Droop, described below, will raise the speed reference. This brings the engine back under control sooner and reduces speed undershoot. Speed undershoot may occur because the time required for the control to return to the new fuel setting is dependent on control dynamics and linkage adjustment.

Figure 5-10. Speed Switch Settings

14. Speed Switch A ON. Set the RPM that will turn on the Speed Switch.

15. Speed Switch A OFF. Set the RPM that will turn off the Speed Switch

16. Speed Switch B ON. Set the RPM that will turn on the Speed Switch.

17. Speed Switch B OFF. Set the RPM that will turn off the Speed Switch

18. Speed Switch C ON. Set the RPM that will turn on the Speed Switch.

19. Speed Switch C OFF. Set the RPM that will turn off the Speed Switch

The speed switch changes state at the selected speed position. Each switch allows 500 mA to sink to the negative of the power supply when closed.

Menu 4 - Fuel Limiters And Control Output Menu

Fuel limiters limit the actuator output from the control. Descriptions of each menu item follow.

1. Maximum Fuel Limit sets the maximum percent actuator output when rated speed is selected. If actuator linkage is correctly set so the actuator is providing the maximum position stop, 3° in advance of the butterfly valve maximum position, this item may be set at 100%. If the actuator must reach maximum before it reaches its maximum stop the entry must be below 100%. (Damage to the butterfly valve and possible jamming of the valve in the wide open position is possible if linkage is not designed to reach maximum actuator position at least 3° in advance of maximum butterfly valve position.) The Maximum limit may be used to limit the horsepower developed in the engine.

2. Transient Limit is used when the maximum fuel limit is controlling the output horsepower of the engine. The transient limit allows overfueling the engine by the amount tuned into the control. This allows the engine to accelerate to the rated load.

3. Transient time is the amount of time that the transient limit is allowed to operate.

4. Start Fuel Limit is a limit that is in place while the engine is starting. This limit helps reduce smoke on diesel engines and prevents overfueling during the start of gas engines. The limit is removed when the engine reaches Start Speed.

5. Start Ramp is a tunable ramp of the actuator output to ensure starting of cold engines. The control ramps the position of the actuator from the Start Fuel Limit open at a controlled rate until the engine starts. After the engine has started the fuel limits will be set by the Maximum Fuel Limit or the Torgue Limit, whichever is less.

6. Start Speed sets the speed in RPM that will remove the start-fuel limit from the control system. When Start Speed is obtained the speed ramps to idle or rated speed, depending upon the selection made. After start speed is attained, the control uses the Maximum Fuel and Torque limits.

Figure 5-11. Torque Limit Map

7. Minimum Torque Limit is the percent actuator output allowed when the engine speed is at or below the Lower Limit speed setting (Menu 3 Lower Limit set point). The torque limiter provides a value between Minimum Torque Limit and Breakpoint Torque Limit when engine speed is between these two settings. This sets the torque limit slope below the Breakpoint position.

8. Torque Limit Breakpoint (BP) is the engine speed at which the slope of the torque limiter output changes. The Torque Limit Breakpoint must be set between the Raise and Lower Limits described under Menu 3.

9. (BP) Torque Limit at Breakpoint is the percent actuator output at the engine speed set by the Torque Limit Breakpoint described above.

10. Maximum Torque Limit is the maximum percent actuator output when the engine speed is at the Raise Limit speed setting. The torque limiter provides a value between the Breakpoint Torque Limit and Maximum Torque Limit when engine speed is between these two settings. This sets the slope above the torque limit breakpoint setting.

Figure 5-11 illustrates the breakpoint and these adjustments.

Menu 5 - Display (Engine Monitor) Menu

Input and output values are displayed once when each item is selected.

Descriptions of each menu item follow:

1. Speed displays the current engine speed in rpm.

2. Speed Reference displays the current speed reference in rpm. Note that this may not be the current speed of the engine due to the effect of idle droop, fuel limiters, auxillary input, or droop.

3. Actuator Output displays the current percent of output. This is useful for setup of the control fuel limiters, torque limiter, idle droop, and gain breakpoint settings.

4. Aux Input displays the voltage on the Aux Input.

5. Remote Input displays the milliamps on the Remote Speed Setting Input. This is useful for testing and system calibration.

6. Actuator Current provides a readout of the current to the actuator.

7. Actuator Position provides the voltage reading from the position feedback.

8. Run/Stop Switch Status displays the status of the discrete input at terminal 23. Closed indicates 24 Vdc is applied to the input selecting the run position. Open selects minimum fuel or the stop position.

9. Idle/Rated Switch Status displays the status of discrete input at terminal 17. Closed indicates 24 Vdc is applied to the input selecting idle speed and the idle fuel limit is selected. Open indicates rated speed and the maximum fuel limit.

10. Raise Switch Status displays the status of discrete input at terminal 19. Closed indicates 24 Vdc is applied to the input selecting raise speed (or remote speed setting if the Lower switch is also closed).

11. Lower Switch Status displays the status of discrete input at terminal 18. Closed indicates 24 Vdc is applied to the input selecting lower speed (or remote speed setting if the Raise switch is also closed).

12. Alternate Dynamics Switch Status displays the status of discrete input at terminal 20. Closed indicates 24 Vdc is applied to the input selecting the Alternate Dynamics.

13. Remote Reference Switch Status displays the status of discrete input at terminal 21. Closed, this enables the remote speed setting at terminals 14 and 15 and disables the raise and lower switches.

14. Droop displays the status of the contacts at terminal 22. Open is droop, closed is in isochronous.

15. Diagnostic indicates the status of the diagnostics switch.

16. Speed Switch A indicates the on/off position of the switch.

17. Speed Switch B indicates the on/off position of the switch.

18. Speed Switch C indicates the on/off position of the switch.

19. Fault Lamp indicates the switch position at terminal 6. This switch is on when a fault has been detected. The system must be turned off and powered back up to extinguish the lamp or open the switch.

Menu 6 - Configuration Menu

1. Configuration Key is a code which you must enter before you can change any of the set points on the configuration menu. This helps prevent accidental modification of the set points. The code is factory set to "49". Use the Rabbit or Turtle keys to select the code. The code will be returned to "0" when the menu is exited.

2. Number of Gear Teeth is the number of teeth or holes in the gear or flywheel that drives the speed-sensing device. If the gear is running at camshaft speed (one-half engine speed) then you must enter one-half the number of teeth on the gear. The control requires the number of teeth seen by the MPU per engine revolution.

NOTE: Best control performance will be obtained when sensing speed from a gear rotating at full engine speed. Slower-speed gears (such as the camshaft) provide a lower sampling rate which reduces control response time.

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The number of gear teeth is used by the control to convert pulses from the speed-sensing device to engine rpm. To prevent possible serious injury from an overspeeding engine, make sure the control is properly programmed to convert the gear-tooth count into engine rpm. Improper conversion could cause engine overspeed.

3. Dynamics Map selects the mapping algorithm used to map dynamics as a function of engine speed. Figure 5-4 illustrates how dynamics vary as a function of engine speed for each map.

4. Failsafe Function. Use Rabbit or Turtle keys: Up to enable, Down to disable.

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The Failsafe function causes the ProAct control to issue a minimum fuel signal should the MPU signal fail. Should the function be disabled (to permit a fuel position while cranking or for test procedures) it must be enabled again to prevent overspeed should the signal fail while the engine is operating. Engine overspeed can damage equipment and cause personal injury or death.

Menu 0 Error Menu

1. Active Errors display errors that the control has detected that are still present. The error must be corrected before operation of the engine. Active errors can be cleared by toggling Run/Stop.

2. Logged Errors provides a means of recording errors that the control detects. The error log will be saved, even if power to the control is lost. To clear the erreor log press the "hot" key (square key).

3. Self Test Result displays the result of power up diagnostics performed on the microprocessor, data, and program memory. A successful test gives a result of 49. Contact Woodward Governor Company if the self test result is not 49.

Conclusion Of Test And Calibration Procedures

This completes the calibration instructions. Save the points by pressing the "SAVE" key on the Hand Held Programmer. Power down the control for about 10 seconds. Restore power and verify that all set points are as recorded.

Disconnect the Set Point Programmer from the control.

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TO PROTECT AGAINST POSSIBLE PERSONAL INJURY, LOSS OF LIFE, and/or PROPERTY DAMAGE WHEN STARTING THE ENGINE, BE PREPARED TO MAKE AN EMERGENCY SHUTDOWN to protect against runaway or overspeed should the mechanical-hydraulic governor(s), or electric control(s), the actuator(s), fuel control(s), the driving mechanism(s), the linkage(s), or the controlled device(s) fail.

Table 5-1. System Troubleshooting