WO2001027478A1 - Robust servo/hydraulic control system and method - Google Patents
Robust servo/hydraulic control system and method Download PDFInfo
- Publication number
- WO2001027478A1 WO2001027478A1 PCT/US2000/028408 US0028408W WO0127478A1 WO 2001027478 A1 WO2001027478 A1 WO 2001027478A1 US 0028408 W US0028408 W US 0028408W WO 0127478 A1 WO0127478 A1 WO 0127478A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- voltage
- duty cycle
- load
- temperature
- piston
- Prior art date
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
- F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
- F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
- F15B9/09—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor with electrical control means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
- F01L1/344—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
- F01L1/3442—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear using hydraulic chambers with variable volume to transmit the rotating force
- F01L2001/34423—Details relating to the hydraulic feeding circuit
- F01L2001/34426—Oil control valves
- F01L2001/3443—Solenoid driven oil control valves
Definitions
- the present invention relates to hydraulic control systems for use in automotive valve control devices.
- Control fluid viscosity can vary significantly with fluid temperature and age.
- Control fluid pressure can vary significantly during even one control cycle. Variations in fluid viscosity and pressure significantly affect dynamic hydraulic control performance. Accordingly, some attempt has been made to estimate control fluid viscosity and pressure and vary control gains in response thereto. For example, temperature and pressure have been measured or estimated and the temperature and age estimations used to estimate fluid viscosity, and the estimated viscosity and pressure used to vary control gains. Such complex sensing, estimating and processing yields some improvement in dynamic hydraulic control system performance.
- Hydraulic controls are typically difficult and time consuming to calibrate. This is especially true in application that involve a wide range of operating conditions, as in a cam phaser control. Conditions for the system can and do change with temperature changes. The temperature alters the oil viscosity, the resistance of the control valve and clearances for the engine. Furthermore, as temperature increases, the copper wire in the solenoid actuator heats up, thereby increasing electrical resistance.
- FIG. 2 A typical analog conventional control system is shown in FIG. 2.
- a control command Pd generated by controller for example as a predetermined function of such engine parameters as engine speed, load or intake pressure, and in accord with a desired phasing between the camshaft and crankshaft of a system to which the control function is applied, is provided to summing node 60.
- Sensed piston position signal Pa from sensor 36 is likewise applied in negated form to summing node 60, so to be subtracted from signal Pd to form a position error signal Pe, to be minimized in accord with the control function of FIG. 2.
- Signals Pd and Pa are also applied to slope generator 64 which, generates m, a rate of change of Pa over a predetermined period of time.
- the slope generator may measure the responsiveness of the actuator 62 to a change in commanded actuator position.
- Actuator 62 of FIG. 2 simply represents the hydraulic actuator controlled such as the a cam phaser piston in a cam phaser control system.
- the analog system compares an amount of change in the value CMD and a resulting amount of change in sensed actuator position Pa over a predetermined transient response period of time may be used to generate a transient response transfer function providing the responsiveness measure.
- the rate of reduction of any significant position error Pe in the system may indicate system responsiveness in accord with this invention.
- the slope generator 64 provides output signal m representing the time rate of change or other responsiveness measure of actuator 62, for use in adjusting control responsiveness in accord with this invention.
- the value m is provided to control blocks 66, 68, and 70 at which control gains Kp, Kd, and Ki are adjusted as predetermined functions of the value m.
- Such functions may be simple linear relationships between magnitude of m and control gain magnitude, wherein gain magnitude increases with increasing m and decreases with decreasing m. Further detail on such linear relationships would be provided through a conventional calibration process for a given system to provide appropriate and desirable control responsiveness adjustment.
- a conventional system such as described above is calibrated as a compromise among the different expected operating conditions. For example, controlling duty cycle controls the percentage of oil flow, not the actual cam phaser mechanism. Moreover, control is not a linear function. In addition, oil flow rate changes with operating conditions.
- Those skilled in the art can readily convert such analog controls into digital controls by providing appropriate sensors, processors and programs for replicating the analog control in digital form
- the digital form has the same drawbacks of compromised calibration and instability due to unexpected operating conditions
- the present invention continuously calibrates the control system to account for changes in oil temperature and variations in applied voltage Using a position, integral and deceleration control scheme, the integral and deceleration terms are selectively applied to improve the response of a cam phasing system
- the control valve is tested by reading the voltage and increasing duty cycle to find the current at which the control valve first begins to move The output is slowly increased until a response is observed More specifically, with the control valve in a hold position the duty cycle of the PWM is gradually increased until movement in the hydraulic device is observed This provides a threshold that corresponds to the initial temperature
- FIG 1 is a general illustration of the hydraulic control system hardware of the preferred embodiment in an automotive application
- FIG 2 is a block diagram of an analog control system
- FIG 3 is a graph showing variations in fluid flow vs duty cycle for the control valve for at different voltages and at the same temperature
- FIG 4 is a graph showing variations in fluid flow vs duty cycle for the same voltage and different oil temperatures
- FIGS 5A and 5B are a computer flow diagram illustrating a step by step procedure for carrying out the control function described in FIG 2 in accord with the preferred embodiment
- FIG 6 is a set of curves showing the duty cycles for hold, maximum phase direction and default direction
- a hydraulic control system is provided to control the position of a hydraulic actuator 12 such as a cam phaser piston, to provide for linear positioning thereof along a range of motion
- the piston 12 may move in this embodiment bi-directionally, wherein hydraulic fluid pressure is applied to a first side of the piston 12 fiom hydraulic fluid admitted through passage 14 to a first side of the piston, and may move in a reverse direction of motion from pressure applied by hydraulic fluid passing through a second passage 16
- the piston may move, as influenced by hydraulic pressure applied thereto, along a sleeve attached to a phasing device 10, wherein the phasing device may be of conventional design for varying the angular relationship between a crankshaft and camshaft as is generally understood m the art
- the piston 12 may be attached, such as via a conventional paired block configuration or a conventional helical spline configuration, to a toothed wheel (not shown), on which is disposed a chain linked to an engine crankshaft
- the phaser 10 may then be fixedly mechanically linked to a camshaft
- a four way solenoid operated control valve 18 admits a varying quantity of hydraulic fluid through respective first and second passages 14 and 16 to respective first and second sides of piston 12 to apply pressure to such sides
- the relative pressure applied to the first and second sides of piston 12 determines the steady state (hold) position of the piston Precise piston positioning along a continuum of positions withm the sleeve of phaser 10 is provided through precise control of the relative position of control valvel 8
- the valve 18 is a conventional solenoid control valve with a supply 32 and vent ports 30, 31 are connected, respectively, to a source of pressurized oil and to a reservoir Outlet ports 33, 34 are selectively coupled to the opposite sides of the cam phaser cylinder to drive
- the valve has vent ports 30, 31, a supply port 32, and cam phaser ports 33, 34
- its lands selectively connect the cam phaser ports 33, 34 to one of the vent ports 30, 31 or the supply port 32 In this manner fluid is respectively supplied and drained from opposite ends of the cam phaser piston 12
- the pulse width modulator (PWM) controller 20 applies a PWM voltage signal to the solenoid 22 to hold or move the solenoid and the spool 19 connected thereto
- PWM pulse width modulator
- a portion of the vented fluid is directed to the corresponding side of piston 12 to apply a hydraulic force thereto, to displace the piston away from its rest position in accord with the relative fluid pressure force applied across the piston
- the force applied to the piston may generally be expressed as hydraulic pressure
- PWM controller 20 receives position signals from the cam position sensoi 24 and the crankshaft sensor 26 By comparing the time differences in the received signals, the controller 20 determines the relative phase between the cam and the crankshaft
- the spool 19 is held, for a given duty cycle, substantially at a fixed position corresponding to the average current in the coil, as is generally understood in the solenoid control art
- the frequency of the PWM signal is set high enough that position of piston 12 is stable for a fixed PWM value
- FIG 3 shows the effects of voltage on a typical system
- the three plots show results of the same solenoid valve operated at the same temperature but at different voltages Level 1 is the highest voltage, Level 3 is the lowest and Level 2 is intermediate Levels 1 and 2
- the lowest point on each curve represents the duty cycle where the spool 19 holds the cam phaser piston 12 and the oil flow is zero oi only leakage
- the maximum oil flow occurs at the tops of the curves
- FIG 3 shows that, for a known temperature, one can predict the duty cycle that corresponds to the hold position for the spool and to the positions of maximum oil flow For example, consider the Level 1 voltage At a 35% duty cycle it holds its position At about 14% duty cycle the valve carries maximum flow m one direction (in the default/spring biased direction) and at about 50% duty cycle it carries maximum flow in the opposite direction
- FIG 4 the voltage is held constant and the results of oil flow at two different temperatures are shown Temperature 2 is higher than temperature 1 and the curves show that increased temperatures require higher duty cycles to achieve the same results as operation at lower temperatures
- FIG 4 also shows that the duty cycle can be used to calculate temperature
- the control system program described hereinafter uses this feature to calculate temperature After temperature is calculated, the various system gams (position and integral) are computed to provide dynamic adjustment for the system At the end of the program the supply voltage of the solenoid is read Then the calculated gams ate compensated to adjust for changes in voltage
- FIG 6 provides the duty cycle bands to determine the lower limits for 100%o oil flow
- the solid line curve shows the duty cycle for the hold position
- the bands for the maximum phase direction (against spring bias) and default direction (with spring bias) are shown
- controller 20 The operating characteristics of the valve as shown in the graphs is stored as data in the memory of the controller
- the data is provided from initial design criteria and is updated m the memory by measured values
- the control operations accomplished by controller 20 are carried out as a se ⁇ es of programmed steps by a processor (not shown) in controller 20
- That controller includes a processor with conventional components and accessories mcludmg a read only memory for storing operatmg system and application programs, a random access memory for holdmg data and an arithmetic logic unit for performing computation and logical operations
- One of the application programs is a se ⁇ es of operations as further shown m the flow chart of Figs 5 A and 5B
- the series of steps performed by the controller of the control system includes a first step 101, where the engine for the automobile is turned on The control system learns the offsets between the cam tooth wheel and a reference signal such as a non-hyphened phase cam or crank reference These offsets are learned at or above a given number of revolutions per minute so that the system is stabilized
- step 102 the software determines the amount of cam or crank drive noise m the system In any given system, thei e are inherent fluctuations These fluctuations are usually mmor and are not the result of changes in the operatmg conditions As such, the system learns these variations and uses these variations to establish a noise level Once the noise level is established, the software will ignore making changes if any changes are sensed withm the noise level In effect, this establishes a deadband for system changes In order to be recognized and adjusted, any changes must be greater than this deadband This step impioves the ability of the control system to hold the position and avoids the unwanted effect of a system trying to correct itself for what are, in effect, normal variations
- step 103 the algorithm learns the voltage compensated integral term for a controller
- the integral term is initialized to a low value
- the output duty cycle to the control valve is the integral term modified by the voltage correction
- the algorithm increases the integral term until the sensor 24 of the control system detects movement as seen in the cam phaser 10
- the integral term just prior to the initiation of movement becomes a starting term that is used in the control loop
- the integral term is used to compensate for voltage changes
- the integral term slows down the reaction time of the system This is desirable when the spool 9 is in a hold position
- the invention overcomes this problem by establishing certain windows in the operation foi usmg the integral term.
- Step 104 helps establish those windows
- the algorithm compares the previous setpoint to a desired setpoint If the new setpoint is not greater than the old setpoint by previously defined and stored hysteresis or background noise, then the algorithm uses the old setpoint This increases the stabilization, especially if the desired position is generated externally
- Step 105 prevents the system from exceeding either user-designed or physical limits The setpoint is compared to these limits and if the new setpoint exceeds the limits, it is appropriately adjusted to a lower value
- the next step is to determine the oil temperature using the voltage compensated integral term This is done in step 106 with the data shown in Fig 6
- the algorithm is designed so that the integral term is primarily used to keep the valve in a steady state hold position
- the hold position is represented in the valve profiles as the area on the oil flow curves that correspond to zero oil flow In other words, it corresponds to the minimum point of the curve shown in Figs 3 and 4
- the duty cycle changes with voltage and temperature Since the integral term is already compensated for voltage, any change in the integral term, i e , the hold position, represents a change in temperature
- step 107 calculates the duty cycle for which maximum flow from the control valve for the given hold position This takes into account changes in temperature and voltage Using the oil flow profiles shown in Fig 4, the algorithm predicts the required duty cycle at which the valve delivers its maximum oil flow The algorithm uses the integral term to determine the steady state hold position, i e , the position where zero oil flow occurs, which in turn is adjusted by a voltage correction term That voltage adjusted integral term is then used to calculate the duty cycles that represent the maximum oil flow
- the system calculates the velocity of the cam phasing movement in step 109 As shown in step 110, if the average velocity exceeds a referenced velocity while at maximum oil flow (found in step 108), then the program provides a velocity compensation factor That factor is the average velocity divided by the reference velocity.
- the servo gains and bands are adjusted by the velocity-compensation factor As velocity increases, proportional and integral gains decrease while derivative gain and the bands increase.
- the error from the setpoint and feedback readings are calculated and the direction of the error is determined (step 113 )
- positive servo factors are used to correct the direction and in step 115, further adjustments are made to the proportional gain to compensate for velocity.
- step 116 the program checks to see if the system's velocity and error are less than user- defined limits If so, it means that the system is not moving fast, the error is small and it is likely holding a position.
- the system only updates the integral term when holding a position This prevents the system from wind-up and unnecessary hunting
- step 117 the integral term is calculated and in step 118, the algorithm determines if the error is less than the defined limit to calculate the deceleration term
- the deceleration term is not used until the system approaches the setpoint It is primarily used as a brake
- the deceleration term is proportional to the kinetic energy of the system
- the kinetic energy is proportional to the square of velocity (V 2 )
- V 2 the square of velocity
- step 120 the individual gain terms are then combined, including the proportional, integral and deceleration terms.
- This total term is independent of voltage
- the control system separates out the voltage influences from the proportional, integral and deceleration terms This improves the robustness of the system It allows the system's voltage to change at any time without causing the proportional, integral and deceleration terms to chase and correct for voltage changes Because the system does not correct for voltage changes until this point in the program, it is a more stable system As a result, a steep change will produce the same proportional, integral and deceleration term values independent of voltage Accordingly, regardless of the voltage, the duty cycle of the system will be adjusted as needed at the valve in order to maintain the same oil flow In addition, voltage fluctuations can occur quickly and often, especially in an automotive environment If the voltage is not monitored and compensated, it could cause havoc with the ability to control the hydraulic system
- step 122 the system output is applied to the control valve and in step 123, the program is repeated beginning from step 105
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Abstract
Description
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Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00970891A EP1290350A1 (en) | 1999-10-14 | 2000-10-13 | Robust servo/hydraulic control system and method |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15939399P | 1999-10-14 | 1999-10-14 | |
US60/159,393 | 1999-10-14 |
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WO2001027478A1 true WO2001027478A1 (en) | 2001-04-19 |
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Application Number | Title | Priority Date | Filing Date |
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PCT/US2000/028408 WO2001027478A1 (en) | 1999-10-14 | 2000-10-13 | Robust servo/hydraulic control system and method |
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WO (1) | WO2001027478A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2416451A (en) * | 2004-07-16 | 2006-01-25 | Zeiss Carl Jena Gmbh | Method of detecting images of a sample using a laser-scanning miscroscope with linear scanning |
GB2416454A (en) * | 2004-07-16 | 2006-01-25 | Zeiss Carl Jena Gmbh | Method of detecting images of a sample using a laser-scanning miscroscope |
WO2008026043A3 (en) * | 2006-08-31 | 2008-05-02 | Toyota Motor Co Ltd | Variable valve timing system |
DE102006061104A1 (en) * | 2006-12-22 | 2008-06-26 | Schaeffler Kg | Method for determining a duty cycle for a valve of a camshaft adjuster |
WO2009011212A1 (en) * | 2007-07-18 | 2009-01-22 | Toyota Jidosha Kabushiki Kaisha | Variable valve train control device |
CN101881196A (en) * | 2009-05-05 | 2010-11-10 | 通用汽车环球科技运作公司 | Be used to control the method and system of cam phaser |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5937806A (en) * | 1998-03-13 | 1999-08-17 | General Motors Corporation | Closed-loop camshaft phaser control |
-
2000
- 2000-10-13 WO PCT/US2000/028408 patent/WO2001027478A1/en not_active Application Discontinuation
- 2000-10-13 EP EP00970891A patent/EP1290350A1/en not_active Withdrawn
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5937806A (en) * | 1998-03-13 | 1999-08-17 | General Motors Corporation | Closed-loop camshaft phaser control |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2416451A (en) * | 2004-07-16 | 2006-01-25 | Zeiss Carl Jena Gmbh | Method of detecting images of a sample using a laser-scanning miscroscope with linear scanning |
GB2416454A (en) * | 2004-07-16 | 2006-01-25 | Zeiss Carl Jena Gmbh | Method of detecting images of a sample using a laser-scanning miscroscope |
WO2008026043A3 (en) * | 2006-08-31 | 2008-05-02 | Toyota Motor Co Ltd | Variable valve timing system |
US7938088B2 (en) | 2006-08-31 | 2011-05-10 | Toyota Jidosha Kabushiki Kaisha | Variable valve timing system |
DE102006061104A1 (en) * | 2006-12-22 | 2008-06-26 | Schaeffler Kg | Method for determining a duty cycle for a valve of a camshaft adjuster |
WO2008077674A1 (en) * | 2006-12-22 | 2008-07-03 | Schaeffler Kg | Method for determining a scanning ratio for a valve for a camshaft adjuster |
US8360020B2 (en) | 2006-12-22 | 2013-01-29 | Schaeffler Technologies AG & Co. KG | Method for determining a scanning ratio for a valve for a camshaft adjuster |
WO2009011212A1 (en) * | 2007-07-18 | 2009-01-22 | Toyota Jidosha Kabushiki Kaisha | Variable valve train control device |
US8281757B2 (en) | 2007-07-18 | 2012-10-09 | Toyota Jidosha Kabushiki Kaisha | Variable valve train control device |
CN101881196A (en) * | 2009-05-05 | 2010-11-10 | 通用汽车环球科技运作公司 | Be used to control the method and system of cam phaser |
Also Published As
Publication number | Publication date |
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EP1290350A1 (en) | 2003-03-12 |
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