US 7,066,189 B2 · Predictive maintenance and initialization system for a digital servovalve

Abstract

Provided is a servovalve system for regulating fluid flowing within a fluid circuit. The servovalve system comprises a housing, a spool slidably disposed within the housing, a stepper motor operatively connected to the spool, and a controller and a position sensor electronically connected to the stepper motor. The controller generates driver signals representative of a desired amount of stepper motor rotation in order to cause the stepper motor to effectuate spool motion relative to the housing. The position sensor senses an actual amount of stepper motor rotation and generates a quantity of position signals representative thereof. The controller determines a signal ratio of the quantity of the position signals to the quantity of the driver signals and generates a diagnostic signal when the signal ratio reaches a threshold value representative of a predetermined level of mechanical resistance of spool motion relative to the housing.

Claims21

Dependent claims

A servovalve system for regulating fluid flowing within a fluid circuit, the servovalve system comprising:

a housing;
a spool slidably disposed within the housing;
a stepper motor operatively connected to the spool and being configured to move the spool relative to the housing in order to manipulate the flow of fluid within the fluid circuit;
a controller electronically connected to the stepper motor and configured to generate a quantity of driver signals, each one of the driver signals being representative of a desired amount of stepper motor rotation in order to effectuate incremental spool motion relative to the housing;
and
a position sensor electronically coupled to the stepper motor, the position sensor being configured to sense an actual amount of stepper motor rotation and generate a quantity of position signals representative thereof;
wherein the controller is operative to record the quantity of position signals corresponding to the quantity of driver signals, determine a signal ratio of the quantity of the position signals to the quantity of the driver signals, and generate a diagnostic signal when the signal ratio reaches a threshold value representative of a predetermined level of mechanical resistance of spool motion relative to the housing.

4 more elements

A method for initializing a servovalve system configured to regulate fluid flowing within a fluid circuit, the servovalve system having a servovalve assembly and a reversible stepper motor operatively connected thereto, the servovalve assembly including a housing and a spool moveably disposed therewithin, the servovalve system including at least one mechanical stop restricting motion of the spool relative to the housing, the stepper motor being operative to move the spool relative to the housing in order to manipulate the flow of fluid within the fluid circuit, the method comprising the steps of:

(a) generating a driver signal representative of a desired amount of stepper motor rotation;
(b) rotating the stepper motor in a first direction in response to the driver signal in order to effectuate incremental spool motion relative to the housing;
(c) sensing an actual amount of stepper motor rotation occurring in response to the driver signal;
(d) generating a quantity of position signals representative of the actual amount of stepper motor rotation indicating continuing spool motion;
(e) counting the quantity of position signals resulting from the actual amount of stepper motor rotation;
(f) repeating steps (a) through (e) until no position signals are generated in response to the driver signal in order to indicate that the spool is located at an initialization position;
(f) generating a predetermined quantity of driver signals to cause stepper motor rotation effective to move the spool from the initialization position to a null position such that the flow of fluid through the housing is blocked;
and
(g) rotating the stepper motor in a second direction reverse to that of the first direction in response to the predetermined quantity of driver signals in order to cause the spool to move to the null position.

6 more elements

Dependencies are inferred from the claim text.

Predictive maintenance and initialization system for a digital servovalve

Life of this patent

Predictive maintenance and initialization system for a digital servovalve

Life of this patent

Abstract

Claims21