Abstract:
A servo control system comprising a hydraulic actuator, a position sensor and a hydraulic control valve. The hydraulic actuator is coupled to a gas controlled valve. The position sensor measures the position of the hydraulic actuator and sends the position of the actuator as an input to an engine control unit (ECU). The hydraulic control valve is coupled to a proportional solenoid coupled to the ECU. When the ECU senses the position of the hydraulic actuator and in response to a control input, the ECU commands the position of the hydraulic control valve by controlling the force of the proportional solenoid and the hydraulic fluid sent to the hydraulic actuator, actuating the hydraulic actuator to move to a desired position and actuate the gas controlled valve.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims one or more inventions which were disclosed in Provisional Application No. 61/021,482 filed Jan. 16, 2008, entitled “SERVO SYSTEM USING FEEDBACK”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention pertains to the field of servo systems. More particularly, the invention pertains to actuated servo systems using feedback. 
         [0004]    2. Description of Related Art 
         [0005]    In U.S. Pat. No. 6,883,320, a servomechanism for a valve controlling engine intake uses a proportional solenoid operating a hydraulic valve to power a hydraulic actuator, setting the position of the control valve. An engine sensor and electric controller provide input to the proportional solenoid. Feedback from the position of the control valve is applied to the hydraulic valve by a cam and a spring applying a force in opposition to the proportional solenoid. The mechanical feedback in US&#39;320 applies a direct force on the valve via the spring. 
       SUMMARY OF THE INVENTION 
       [0006]    A servo control system comprising a hydraulic actuator, a position sensor and a hydraulic control valve. The hydraulic actuator is coupled to a gas controlled valve. The position sensor measures the position of the hydraulic actuator and sends the position of the actuator as an input to an engine control unit (ECU). The hydraulic control valve is coupled to a proportional solenoid coupled to the ECU. When the ECU senses the position of the hydraulic actuator and in response to a control input, the ECU commands the position of the hydraulic control valve by controlling the force of the proportional solenoid and the hydraulic fluid sent to the hydraulic actuator, actuating the hydraulic actuator to move to a desired position and actuate the gas controlled valve. 
         [0007]    In an alternate embodiment, the hydraulic actuator may be coupled to a rack and a valve may be actuated through a pinion and a rotary shaft. The valve may be a butterfly or flapper valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0008]      FIG. 1  shows a schematic of a hydraulically actuated servo system using electrical feedback and rotary output. 
           [0009]      FIG. 2  shows a more detailed schematic of the control valve of  FIGS. 1 and 3 . 
           [0010]      FIG. 3  shows a schematic of a hydraulically actuated servo system for a poppet EGR valve. 
           [0011]      FIG. 4   a  shows a schematic of a control system in which a hydraulic actuator controls a gas operated poppet control valve with a hydraulic control valve in a stationary position.  FIG. 4   b  shows a schematic of a control system in which a hydraulic actuator controls a gas operated poppet control valve with a hydraulic control valve moving towards a first position.  FIG. 4   c  shows a schematic of a control system in which a hydraulic actuator controls a gas operated poppet control valve with a hydraulic control valve moving towards a second position. 
           [0012]      FIG. 5   a  shows a schematic of a control system in which a hydraulic actuator controls a rotary device with a hydraulic control valve in a closed position.  FIG. 5   b  shows a schematic of a control system in which a hydraulic actuator controls a rotary device with a hydraulic control valve in a mid position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIGS. 4   a  through  4   c  show schematics of a proportional position feedback hydraulic servo system.  FIG. 4   a  shows a schematic of a control system in which a hydraulic actuator controls a gas operated poppet control valve with a hydraulic control valve in a stationary position.  FIG. 4   b  shows a schematic of a control system in which a hydraulic actuator controls a gas operated poppet control valve with a hydraulic control valve moving towards a first position.  FIG. 4   c  shows a schematic of a control system in which a hydraulic actuator controls a gas operated poppet control valve with a hydraulic control valve moving towards a second position. 
         [0014]    Referring to  FIGS. 4   a  through  4   c  a double acting hydraulic actuator in fluid communication with a hydraulic control valve  28 . The hydraulic control valve  28  includes a spool  40  with a plurality of lands that is actuated by a proportional solenoid  38  on one side and a spring  33  on the opposite side. The proportional solenoid  38  is in communication with an engine control unit (ECU)  10 . The double acting hydraulic actuator  64  operates a gas operated poppet valve  37  such as a poppet wastegate valve or a poppet EGR valve. The gas operated poppet valve  37  shown in  FIGS. 4   a - 4   c  is shown by a three position valve in which hot gas flow from a source is blocked  37   c , restricted  37   b , or allowed  37   a  to flow to or from an exhaust gas component. The position of a piston  46  of the double acting hydraulic actuator  64  is monitored by a position sensor  56 . The position sensor  56  is in communication with the engine control unit (ECU)  10 . The position sensor  56  produces a feedback signal  51  in proportion to the hydraulic actuator position which gets sent to the ECU  10 . The ECU  10  uses the feedback signal  51 , other engine parameters, and a control input to generate a signal  53  that is sent to the proportional solenoid  38  to change the current, changing the position of the spool  40 , the hydraulic fluid sent to hydraulic actuator  64 , and the position of the gas operated poppet valve  37 . 
         [0015]    Referring to  FIG. 4   a , the position sensor  56  monitors the position of the piston  46  of the double acting hydraulic actuator  64  and sends a signal  22  to the ECU  10 . The ECU  10  uses the feedback signal  51  from the position sensor  56 , other engine parameters, and a control input and sends a signal  53  to the proportional solenoid  38 . In this case, the signal  53  sent from the ECU  10  did not alter the current being supplied to the proportional solenoid  38 . With the current remaining in a steady state, the spool  40  is not moved and remains in position, which happens to be in a middle position  40   b  as shown. In this position, the lands of the spool  40  block the flow of fluid to or from the chambers  52 ,  54  defined between the piston  46  and the housing  50  of the double acting hydraulic actuator  64 . Since fluid is prevented from flowing in or out of the chambers  52 ,  54  formed between the piston  46  and the housing  50  of the double acting hydraulic actuator  64 , the gas operated poppet valve  37  also remains in position, which happens to be a middle position  37   b , in which hot gas flow from a source is restricted from flowing to or from an exhaust gas component. If the force of the spring  33  on the spool  40  increases or decreases and the force on the spool  40  from the proportional solenoid  38  remains the same, the spool  40  will move accordingly. If the force of the proportional solenoid  38  on the spool  40  increases or decreases and the force on the spool  40  from the spring  33  remains the same, the spool will move accordingly. 
         [0016]    Referring to  FIG. 4   b , the position sensor  56  monitors the position of the piston  46  of the double acting hydraulic actuator  64  and sends a signal  51  to the ECU  10 . The ECU  10  uses the feedback signal  51  from the position sensor  56 , other engine parameters and a control input and sends a signal  53  to the proportional solenoid  38 . The signal  53  from the ECU  10  increases the current to the proportional solenoid  38 , increasing the force on the one end of the spool  40  to be greater than the spring  33  force on the opposite end of the spool  40 , moving the spool  40  towards the spring  33  (towards the right in the figure) towards a first position  40   a  until the spring force equals the force from the proportional solenoid  38 . Once the force of the spring equals the force of the proportional solenoid  38 , the spool  40  moves to an equilibrium position. If the force of the spring  33  on the spool  40  increases or decreases and the force on the spool  40  from the proportional solenoid  38  remains the same, the spool  40  will move accordingly. If the force of the proportional solenoid  38  on the spool  40  increases or decreases and the force on the spool  40  from the spring  33  remains the same, the spool will move accordingly. With the spool  40  moving towards the first position  40   a , fluid from a first chamber  52  formed between the piston  46  and the housing  50  of the double acting hydraulic actuator  64  receives fluid from a source  18  and the opposite second chamber  54  is exhausts fluid through the spool  40  to sump (not shown). By filling one chamber  52  and exhausting the other chamber  54  of the double acting hydraulic actuator  64 , the piston  46  moves towards the spring  35  (towards the right in the figure), against the force of the spring  35  on the gas operated poppet valve  37 , moving the poppet valve towards a first position  37   a  in which hot gas flow is allowed from the source to or from an exhaust gas component until the force of the spring  35  on the gas operated valve  37  equals the force of the fluid acting on the piston  46  of the double acting hydraulic actuator  64 . When the force of the spring  35  equals the force of the fluid acting on the piston  46  of the double acting hydraulic actuator  64 , the gas operated poppet valve  37  moves to an equilibrium position. If the force of the spring  35  on the gas operated poppet valve  37  increases or decreases and the force on the gas operated poppet valve  37  from the hydraulic actuator  64  remains the same, the gas operated poppet valve  37  will move accordingly. If the force of the hydraulic actuator  64  on the gas operated poppet valve  37  increases or decreases and the force on the gas operated poppet valve  37  from the spring  35  remains the same, the gas operated poppet valve  37  will move accordingly. 
         [0017]    Referring to  FIG. 4   c , the position sensor  56  monitors the position of the piston  46  of the double acting hydraulic actuator  64  and sends a signal  51  to the ECU  10 . The ECU  10  uses the feedback signal  22  from the position sensor  56 , other engine parameters, and a control input and sends a signal  53  to the proportional solenoid  38 . The signal  53  from the ECU  10  has decreases the current to the proportional solenoid  38 , decreasing the force on the one end of the spool  40  to be less than the spring  33  force on the opposite end of the spool  40 , moving the spool  40  towards the proportional solenoid  38  (towards the left in the figure) towards a second position  40   c  until the spring  33  force equals the force from the proportional solenoid  38 . Once the force of the spring  33  equals the force of the proportional solenoid  38 , the spool  40  moves to an equilibrium position. If the force of the spring  33  on the spool  40  increases or decreases and the force on the spool  40  from the proportional solenoid  38  remains the same, the spool  40  will move accordingly. If the force of the proportional solenoid  38  on the spool  40  increases or decreases and the force on the spool  40  from the spring  33  remains the same, the spool will move accordingly. With the spool  40  moving towards the second position  40   c , fluid from a second chamber  54  formed between the piston  46  and the housing  50  of the double acting hydraulic actuator  64  is receives fluid from a source  18  and the opposite first chamber  52  is exhausts fluid through the spool  40  to sump (not shown). By filling one chamber  54  and exhausting the other chamber  52  of the double acting hydraulic actuator  64 , the piston  46  moves towards the left in the figure, with the force of the spring  35  on the gas operated poppet valve  37 , moving the gas operated poppet valve towards a third position  37   c  in which hot gas flow is blocked from a source to or from an exhaust gas component until the force of the spring  35  on the gas operated valve  37  equals the force of the fluid acting on the piston  46  of the double acting hydraulic actuator  64 . When the force of the spring  25  equals the force of the fluid acting on the piston  46  of the double acting hydraulic actuator  64 , the gas operated poppet valve  37  moves to an equilibrium position. If the force of the spring  35  on the gas operated poppet valve  37  increases or decreases and the force on the gas operated poppet valve  37  from the hydraulic actuator  64  remains the same, the gas operated poppet valve  37  will move accordingly. If the force of the hydraulic actuator  64  on the gas operated poppet valve  37  increases or decreases and the force on the gas operated poppet valve  37  from the spring  35  remains the same, the gas operated poppet valve  37  will move accordingly. 
         [0018]    After the gas operated valve  37  is moved, the position sensor  56  monitors the position of the piston  46  of the double acting hydraulic cylinder and compares the position of the piston  46  to the control input sent to the ECU  10 . 
         [0019]    It should be noted that the gas operated valve  37  is shown in the middle position in  FIGS. 4   a - 4   c , and the arrow above the hydraulic actuator  64  indicates the direction in which the gas operated valve  37  is going to move. 
         [0020]      FIG. 3  shows an example of the servo system shown in  FIGS. 4   a - 4   c  in which the double acting hydraulic actuator  64  is operating a gas operated poppet valve  37 , such as an EGR valve sealed by poppet valves  42 .  FIG. 2  shows a more detailed schematic of the hydraulic control valve  40  used in  FIGS. 1 and 3 . The gas operated poppet valve  37  in this example would be the poppet valve  42 . 
         [0021]    The intake and the exhaust chambers  26 ,  36  of an EGR valve are sealed by poppet valves  42 . The position of the poppet valves  42  are controlled by a spring  44  and hydraulically biased piston  46  attached to the poppet valves  42  via a rod  48 . The spring  44  and the hydraulically biased piston  46  is received within a housing  50  and forms fluid chambers  52 ,  54  on either side of the piston  46  within the housing  50 . A position sensor  56  is present on the piston housing  50  and electrically sends signals regarding the piston  46  position to an ECU  10 . The ECU  10  then sends a signal  53  to a proportional solenoid  38  of a control valve  28 . The proportional solenoid  38  adjusts the spool  40  position. 
         [0022]    When the spool  40  is in the position shown in  FIG. 4   b , supply oil  18  flows as directed by the spool  40  to a first chamber  52  formed between the piston  46  and the housing  50 , and works in conjunction with the force of the spring  44 , opening the poppet valves  42  between the exhaust and the intake chambers  36 ,  26 . The position sensor  56  electronically provides feedback of piston  46  position to the ECU  10  that sends an appropriate signal to the proportional solenoid  38 . 
         [0023]    The proportional solenoid  38  shown is a variable force solenoid but a voice coil actuator or similar linear force motor may also be used. The control valve  28  may be located remotely as shown in  FIG. 3  or may be packaged within the EGR housing  50  in any orientation. 
         [0024]      FIG. 5   a  shows a schematic of a control system in which a hydraulic actuator controls a rotary device with a hydraulic control valve in a closed position.  FIG. 5   b  shows a schematic of a control system in which a hydraulic actuator controls a rotary device with a hydraulic control valve in a mid position. 
         [0025]    Referring to  FIGS. 5   a  and  5   b , the double acting hydraulic actuator  14  is connected to a rotary output shaft  12  that operates butterfly valve or a flapper valve  41  through a rack  34  and pinion  32  and is in fluid communication with a hydraulic control valve  28 . The hydraulic control valve  28  includes a spool  40  with a plurality of lands that is actuated by a proportional solenoid  38  on one side and a spring  33  on the opposite side. The proportional solenoid  38  is in communication with an engine control unit (ECU)  10 . The double acting hydraulic actuator  14  operates a flapper valve or butterfly valve  41  through a rack and pinion. The butterfly valve or flapper valve is indicated by reference number  41  shown in  FIGS. 5   a  and  5   b . The flapper and butterfly valve  41  have a closed position and an open position. The amount the flapper or butterfly valve  41  is open will vary and is not limited to the position shown in  FIG. 5   b . The position of a piston  14   a  of the double acting hydraulic actuator  14  is monitored by a position sensor  16 . The position sensor  16  is in communication with the engine control unit (ECU)  10 . The position sensor  16  produces a feedback signal  22  in proportion to the actuator position which gets sent to the ECU  10 . The ECU  10  uses the feedback signal  22 , other engine parameters, and a control input to generate a signal  24  that is sent to the proportional solenoid  38  to change the current, changing the position of the spool  40 , the hydraulic fluid sent to the hydraulic actuator  14  and the position of the butterfly or flapper valve  41 . 
         [0026]    Referring to  FIG. 5   a , the position sensor  16  monitors the position of the piston  14   a  of the double acting hydraulic actuator  14  and a sends a signal  22  to the ECU  10 . The ECU  10  uses the feedback signal  22  from the position sensor  16 , other engine parameters, and a control input and sends a signal  24  to the proportional solenoid  38 . The signal  24  from the ECU  10  decreases the current to the proportional solenoid  38 , decreasing the force on the one end of the spool  40  to be less than the spring  33  force on the opposite end of the spool  40 , moving the spool  40  towards the proportional solenoid  38  (towards the left in the figure) towards a second position  40   c  until the spring force equals the force from the proportional solenoid  38 . Once the force of the spring  33  equals the force of the proportional solenoid  38 , the spool  40  moves to an equilibrium position. If the force of the spring  33  on the spool  40  increases or decreases and the force on the spool  40  from the proportional solenoid  38  remains the same, the spool  40  will move accordingly. If the force of the proportional solenoid  38  on the spool  40  increases or decreases and the force on the spool  40  from the spring  33  remains the same, the spool will move accordingly. With the spool  40  in the second position  40   c , fluid from a second chamber  15   b  formed between the piston  14   a  and the housing  17  of the double acting hydraulic actuator  14  receives fluid from a source  18  and the opposite first chamber  15   a  is exhausts fluid through the spool  40  to sump (not shown). By filling one chamber  15   b  and exhausting the other chamber  15   a  of the double acting hydraulic actuator  14 , the rack  34  on the second shaft  31  and coupled to the piston  14   a  of the double acting hydraulic actuator is moved, and the pinion  32  meshed with the rack  34  and mounted to the rotary shaft  12  rotates, rotating the butterfly valve  41  mounted to the rotary shaft  31  to a closed position in which fluid is prevented from flowing to or form a source to an exhaust gas component. Once the spool  40  moves to an equilibrium position, the rack  34  on the second shaft  31  moves, rotating the pinion  32  and thus the butterfly valve  41  to an equivalent equilibrium position. 
         [0027]    Referring to  FIG. 5   b , the position sensor  16  monitors the position of the piston  14   a  of the double acting hydraulic actuator  14  and a sends a signal  22  to the ECU  10 . The ECU  10  uses the feedback signal  22  from the position sensor  16 , other engine parameters, and a control input and sends a signal  24  to the proportional solenoid  38 . In this case, the signal  24  sent from the ECU  10  did not alter the current being supplied to the proportional solenoid  38 . With the current remaining in a steady state, the spool  40  is not moved and remains in a middle position in which  40   b  as shown. In this position, the lands of the spool  40  blocks the flow of fluid to or from the chambers  15   a ,  15   b  defined between the piston  14   a  and the housing  17  of the double acting hydraulic actuator  14 . Since fluid is prevented from flowing in or out of the chambers  15   a ,  15   b  formed between the piston  14   a  and the housing  17  of the double acting hydraulic actuator  14 , the rack  34  and pinion  32  are not rotated by the double acting hydraulic actuator  14  and the butterfly or flapper valve remains in a middle position in which fluid may flow from a source to an exhaust gas component. 
         [0028]    After the butterfly valve or flapper valve  41  is moved, the position sensor  16  monitors the position of the piston  14   a  of the double acting hydraulic cylinder and compare the position of the piston  14   a  to the control input sent to the ECU  10 . 
         [0029]      FIGS. 1 and 2  show an example of the control system shown in  FIGS. 5   a - 5   b , with the double acting hydraulic actuator being coupled to a rotary device. Referring to  FIG. 1 , a cam  30  and pinion  32  are mounted on a rotary output shaft  12 . The pinion  32  meshes with a rack  34  on a second shaft  31 . The cam  30  on the rotary output shaft  12  contacts a position sensor  16 . The position sensor  16  is in communication with an engine control unit (ECU)  10 . At the end of the rack  34 , a piston  14   a  of a double acting actuator  14  is attached. The double acting actuator  14  is in fluid communication with a hydraulic control valve  28 .The hydraulic control valve  28  includes a proportional solenoid  38  in communication with the engine control unit  10  and in contact with a spool valve  40 . The proportional solenoid  38  of the hydraulic control valve  28  adjusts the position of the spool  40 , determining the flow of fluid to the double acting actuator  14 . 
         [0030]    Based on the movement of the cam  30 , the position sensor  16  sends a feedback signal  22  to an engine control unit (ECU)  10 . The ECU  10  then sends a signal  24  based on the feedback signal  22 , other engine parameters, and a control input to the proportional solenoid  38  of a hydraulic control valve  28 . The signal  24  may adjust the current supplied to the proportional solenoid  38  of a hydraulic control valve  28 . Depending on the adjustment to the current of the proportional solenoid  38  of the hydraulic control valve  28 , the spool  40  is moved as shown in  FIGS. 5   a - 5   b . If the current is increased or decreased, the spool  40  is moved by the solenoid  38  and the flow of fluid to the double acting hydraulic actuator  14  is adjusted. By adjusting the flow to the double acting hydraulic actuator  14 , the piston  14   a  of the double acting hydraulic actuator  14  is moved and thus the rack  34  in which the piston  14   a  is attached is also moved. By moving the rack  34  on the second shaft  31 , the pinion  32  and cam  30  on the rotary output shaft  12  are also moved. The rotation of the rotary output shaft rotates the position of the butterfly or flapper valve. The position of the cam  30  is measured by the position sensor  16 . 
         [0031]    The rotary output shaft  12  may be connected to a turbocharger wastegate, an EGR wastegate, a bypass valve, flapper valve, butterfly valve, or other modulated devices. The control valve  28  may be located remotely as shown in  FIG. 1  or may be packaged within the actor assembly  20  housing. 
         [0032]    The proportional solenoid  38  may be a variable force solenoid, a voice coil actuator or similar linear motor. 
         [0033]    Alternatively, the position sensor  16  may be mounted directly to the flapper or butterfly valve  41 . 
         [0034]    Other types of hydraulic actuators may also be used other the than the linear actuator shown. 
         [0035]    Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.