Digital servo valve system

• US 5,036,886 A
• Filed: 05/16/1990
• Issued: 08/06/1991
• Est. Priority Date: 12/12/1988
• Status: Expired due to Term

• Current Assignee: Victory Controls, LLC
• Original Assignee: Olsen Controls, Inc.
• Inventors: D'Angelo, Gary, Hamman, Eric, Sperbeck, Albert J., Olsen, Zenny
• Primary Examiner(s): Michalsky, Gerald A.
• Application Number:
  US07/524,637
• Time in Patent Office: 447 Days
• Field of Search: 137/625.65, 137/625.69, 251/129.11, 251/282
• US Class Current: 137/625.65
• CPC Class Codes: F15B 13/0402 for linearly sliding valves, e.g. spool valves
• CPC Class Codes: F15B 13/044 operated by electrically-controlled means, e.g. solenoids, torque-motors
• CPC Class Codes: F15B 2013/0412 with three positions
• CPC Class Codes: F15B 9/03 with electrical control means F15B9/07, F15B9/09, F15B9/17 take precedence
• CPC Class Codes: G05B 19/232 with speed feedback only
• CPC Class Codes: G05B 19/4142 characterised by the use of a microprocessor G05B19/4141 takes precedence
• CPC Class Codes: G05B 2219/31154 Actuator sensor bus, asi, intelligent actuator, motor, sensor
• CPC Class Codes: G05B 2219/31203 Purpose, identification of messages, programs, variables
• CPC Class Codes: G05B 2219/33119 Servo parameters in memory, configuration of control parameters
• CPC Class Codes: G05B 2219/33187 Serial transmission rs232c, rs422, rs485 communication link
• CPC Class Codes: G05B 2219/34215 Microprocessor
• CPC Class Codes: G05B 2219/35438 Joystick
• CPC Class Codes: G05B 2219/37313 Derive speed from position
• CPC Class Codes: G05B 2219/37536 Rate of change, derivative
• CPC Class Codes: G05B 2219/41022 Small gain for small movements, large gain for large movements
• CPC Class Codes: G05B 2219/41047 Recirculating ballnut, ballscrew, preloaded bearing
• CPC Class Codes: G05B 2219/41121 Eliminating oscillations, hunting motor, actuator
• CPC Class Codes: G05B 2219/41146 Kalman filter
• CPC Class Codes: G05B 2219/41156 Injection of vibration anti-stick, against static friction, dither, stiction
• CPC Class Codes: G05B 2219/41203 Lead-phase compensation, lag-phase compensation servo
• CPC Class Codes: G05B 2219/41218 : Posicast, break reference into two parts, better settling time
• CPC Class Codes: G05B 2219/41298 : Stepping motor and control valve and power cylinder and mechanical feedback
• CPC Class Codes: G05B 2219/41367 : Estimator, state observer, space state controller
• CPC Class Codes: G05B 2219/41406 : LQR linear quadratic regulator to calculate gain for several known variables
• CPC Class Codes: G05B 2219/42033 : Kind of servo controller
• CPC Class Codes: G05B 2219/42276 : Action, on power failure, close pilot valve entirely by return spring
• CPC Class Codes: G05B 2219/43048 : Step change in reference, soft start, smoothing reference
• CPC Class Codes: Y10T 137/86622 : Motor-operated
• CPC Class Codes: Y10T 137/8671 : With annular passage [e.g., spool]

Abstract

A novel digital servo valve system for use in displacing an actuator is capable of operating either in closed or open loop mode. The system includes a controller that compares computed values of actuator parameters with preselected parameter values and iteratively determines therefrom command signals for the servo valve. The servo valve is characterized by a ball screw mechanism that eliminates mechanical backlash and a torsion bar which increases radial and angular compliance. A servo valve provided according to the present invention also displays reduced flow forces using a simple, inexpensive valve body in combination with a uniquely configured displaceable spool.

Claims

1. A translation assembly for use in a servo valve, comprising:

a spool rotatable and translatable about a longitudinal axis;

a body having an interior cavity for receiving said spool;

a ball/screw means attached to said spool at a first end thereof for translating rotation received at an opposed second spool end into axial spool displacement,

said ball screw means comprising an inner member affixed to said spool at said second spool end;

an outer hollow member affixed to said body configured to receive said inner member;

said inner member having an outer surface and said hollow member having an opposed inner surface both configured to form a helical channel along said axis extending thereabout approximately 360 degrees;

a plurality of displaceable balls located in said channel, said balls configured to substantially conform to said channel; and

said ball screw means being connected to said spool by torsion bar means, disposed along said axis in an interior opening formed in said spool for providing, relative to said axis, displacement between said ball screw means and said spool.

2. A translation assembly as defined in claim 1 further characterized by said spool interior opening being substantially cylindrical, said spool comprising;

a plurality of longitudinally spaced substantially cylindrical lands,

a plurality of recessed regions adjacent to said lands, said recessed regions having at least one substantially curved end portion abutting an adjacent land.

3. A translation assembly as defined in claim 1 further characterized in that said body interior longitudinal cavity has a plurality of substantially cylindrical channels spaced therealong;

and

said spool being displaceable within said cavity along a longitudinal axis, said valve spool having a plurality of substantially cylindrical lands alternately spaced with a plurality of recessed regions, said recessed regions having at least one curved end portion.

4. A translation assembly as defined in claim 3 further characterized in that said recessed section plurality includes a central section and opposed side sections, said central section having opposed curved end portions and said side region having an increasing diameter conical portion extending away from said central recessed region.

5. The apparatus of claim 1 wherein said torsion bar means provides relative to said axis radial displacement between said ball screw means and said spool.

6. The apparatus of claim 1 wherein said torsion bar means provides relative to said axis angular displacement between said ball screw means and said spool.

7. The apparatus of claim 1 wherein said torsion bar means provides relative to said axis angular and radial displacement between said ball screw means and said spool.

8. A servo valve, comprising:

a spool, rotatable and translatable about a longitudinal axis;

a valve body having an interior cavity for receiving said spool;

rotary means positioned at a first end of said spool for providing rotation of said spool about said axis;

ball screw means attached to said spool at an opposed second end thereof for translating said rotation into displacement along said axis,

said ball screw means comprising an inner member affixed to said spool at said second spool end;

an outer hollow member affixed to said body configured to receive said inner member;

said inner member having an outer surface and said hollow member having an opposed inner surface both configured to form a helical channel along said axis extending thereabout approximately 360 degrees;

a plurality of displaceable balls located in said channel, said balls configured to substantially conform to said channel;

torsion bar means, disposed along said axis in an interior opening of said spool, having opposite ends affixed to said spool first end and said ball screw means, respectively, said torsion bar means for providing, relative to said axis, displacement between said ball screw means and said spool.

9. The servo valve of claim 8 wherein said helical channel and said balls have a clearance therebetween of approximately 0.0001 inch.

10. The apparatus of claim 8 wherein said spool inner opening has a diameter in excess of said torsion bar means diameter.

11. A translation assembly for use in a servo valve, comprising:

a spool rotatable and translatable about a longitudinal axis;

a body having an interior cavity for receiving said spool;

a ball/screw means attached to said spool at a first end thereof for translating rotation received at an opposed second spool end into axial spool displacement;

said spool having a substantially cylindrical interior opening and comprising,

a plurality of longitudinally spaced substantially cylindrical lands,

a plurality of recessed regions adjacent to said lands, said recessed regions having at least one substantially curved end portion abutting an adjacent land;

said recessed region plurality includes a central region and opposed side regions, said central region having said curved region at both ends thereof, said side region being defined by an increasing diameter conical portion meeting contiguously with an oppositely facing central curved region such that each conical portion widens from point proximate the meeting of said central and side regions and diametrically progresses in size along a length of said axis away from said central recessed region.