Patent Description:
Patent literature <NUM> discloses an electromagnetic changeover valve used in a hydraulic system. The electromagnetic changeover valve is configured such that the position of the valve spool that moves in coordination with a moving core is displaced in the axial direction by sucking and moving the movable core to a fixed core by energizing and exciting the coil of a solenoid, thereby switching port connection, and switching the flow channel of the hydraulic circuit. The electromagnetic changeover valve is provided with a solenoid at one end of the valve spool. The valve spool is moved to a predetermined position along with the moving core in accordance with the condition of energization of the solenoid.

A switching mechanism embodied by an electromagnetic valve driven by a solenoid is used to switch the mode of a hydraulic actuator. The spool position of the electromagnetic valve may be shifted from a target position due, for example, to an external force exerted on the spool, which may make result in incomplete mode switching. A position sensor for sensing the spool position may be attached. However, this approach is disadvantageous from the perspective of size and weight reduction because the number of components is increased.

The electromagnetic valve disclosed in Patent Literature <NUM> is comprised of a combination of a large number of constituting elements. Since the configuration is complicated, it cannot be said that the requirement for size and weight reduction can be fully met.

The present invention addresses the above-described issue, and an illustrative purpose thereof is to provide a spool position estimation apparatus capable of estimating a spool position of an electromagnetic valve with a simple configuration.

A spool position estimation apparatus according to the present invention includes: a supplying unit that supplies a high-frequency signal to a solenoid for driving a spool of an electromagnetic valve; an acquisition unit that acquires electrical information related to the solenoid supplied with the high-frequency signal, and an estimation unit that estimates a position of the spool based on a result of comparison between the electrical information acquired by the acquisition unit and the high-frequency signal supplied from the supplying unit.

Optional combinations of the aforementioned and replacement of constituting elements or implementation of the present invention in the form of methods, apparatuses, programs, transitory or non-transitory recording mediums storing programs, systems, etc. may also be practiced as optional modes within the scope of the claims.

According to the present invention, it is possible to provide a spool position estimation apparatus capable of estimating the spool position of an electromagnetic valve with a simple configuration.

Embodiments will now be described by way of examples only, with reference to the accompanying drawings which are meant to be exemplary, not limiting and wherein like elements are numbered alike in several Figures in which:.

A summary of the present disclosure will be presented. For example, a switching mechanism embodied by an electromagnetic valve including a solenoid may be used to switch the mode of a hydraulic actuator. In a configuration in which the position of the movable part (e.g., moving core) of the solenoid is not sensed, whether the mode of the hydraulic actuator is actually switched or not is figured out from the behavior of the actuator. In this case, whether the mode is properly switched or not cannot be confirmed until the actuator is actually operated. Therefore, a latent failure mode may be induced.

A position sensor may be used to sense the spool position of the electromagnetic valve. For example, a position sensor such as a linear variable differential transformer (LVDT), a linear potentiometer, etc. may be added to the solenoid to measure the spool position and check whether the mode of the hydraulic actuator is switched properly. In this case, addition of a position sensor such as LVDT and a peripheral electronic circuit for sensing the spool position may make the structure complicated, increase the weight, and increase the size. Also, an increase in the number of components creates a concern that the hydraulic oil may be leaked, and the reliability and cost performance may be deteriorated.

We have devised a technology of sensing the spool position of an electromagnetic valve without using a position sensor such as LVDT from the perspective of improving the cost and failure rate by reducing the number of components and of improving the reliability. In this technology, a high-frequency signal is supplied to the solenoid for driving the spool of the electromagnetic valve. Electrical information related to the solenoid supplied with the high-frequency signal is acquired. The position of the spool is estimated based on a result of comparison between the acquired electrical information and the high-frequency signal supplied from the supplying unit. The spool moves in coordination with the movable part so that the spool position can be estimated from the position of the movable part. In this case, the spool position can be estimated with a simple configuration.

The high-frequency signal is superimposed on the driving voltage for driving the solenoid. The electrical information related to the solenoid may be the driving voltage and the driving current for driving the solenoid, the inverse electromotive force generated in the solenoid, etc. These electrical information items vary depending on the relative position between the solenoid coil and the movable part. Therefore, the spool position can be estimated by comparing the inverse electromotive force and the amplitude and phase of the current with the original high-frequency signal. Further, since the inverse electromotive force is substantially proportional to the moving speed of the spool, it is possible to know the condition of deterioration of the electromagnetic valve by referring to the variation of the inverse electromotive force. In further accordance with this technology, it is possible to estimate the moving speed of the movable part and so it is possible to estimate the mass and load of the driven body. The configuration of the present disclosure will be described in detail with reference to embodiments.

Hereinafter, the invention will be described based on preferred embodiments with reference to the accompanying drawings. In the embodiments and variations, identical or like constituting elements and members are represented by identical symbols and a duplicate description will be omitted. The dimension of members in the drawings are enlarged or reduced as appropriate to facilitate understanding. Those of the members that are not important in describing the embodiment are omitted from the drawings.

Terms including ordinal numbers (first, second, etc.) are used to explain various constituting elements, but the terms are used merely for the purpose of distinguishing one constituting element from the other constituting elements and shall not limit the constituting elements.

A position estimation apparatus <NUM> according to the first embodiment of the present invention will be described with reference to <FIG> and <FIG>. <FIG> schematically shows an actuator apparatus <NUM> provided with the position estimation apparatus <NUM>. The usage of the actuator apparatus <NUM> is not limited, and the actuator apparatus <NUM> can be used as any of a variety of power sources for generating a driving source by hydraulic pressure or pneumatic pressure. In the example of <FIG>, the actuator apparatus <NUM> is used as an apparatus for applying a driving force to at least one driven body <NUM> selected from a rudder surface of a tailplane of an airplane <NUM>, a movable plane of a main plane, and a landing gear that supports wheels for landing. The movable plane of the main plane is exemplified by an aileron 2a and a flap 2b of the main plane. The rudder surface of the tailplane is exemplified by a rudder 2c, an elevator 2d, etc. of the tailplane. The landing gear that supports the wheels for landing is exemplified by a main gear 2f provided in the main plane, a body landing gear <NUM> provided in the body, etc..

<FIG> is a block diagram showing an actuator apparatus <NUM>. The actuator apparatus <NUM> includes a position estimation apparatus <NUM> and a valve unit <NUM>. The valve unit <NUM> includes a driving unit <NUM>, an electromagnetic valve <NUM>, and a hydraulic actuator <NUM>. The electromagnetic valve <NUM> includes a solenoid <NUM> and a spool <NUM> and may be referred to as a solenoid valve. The hydraulic actuator <NUM> include a piston <NUM>.

The driving unit <NUM> functions as a driving circuit that outputs a driving voltage D0 to drive the solenoid <NUM> of the electromagnetic valve <NUM> based on a control signal CNT supplied from a superior control system. The driving voltage D0 may be an AC voltage or a DC voltage having an amplitude that varies in accordance with the control signal CNT. The driving voltage D0 according to the invention is a PWM voltage having a duty ratio that varies in accordance with the control signal CNT. A high-frequency signal Sh described later is superimposed on the driving voltage D0 to produce a driving voltage D1.

The solenoid <NUM> includes a coil <NUM> and a movable part <NUM>. The spool <NUM> is coupled to the movable part <NUM> via a shaft <NUM> and is moved in association with the movement of the movable part <NUM>. When the driving voltage D1 is supplied, a driving current flows in the coil <NUM> of the solenoid <NUM> in accordance with the driving voltage D1. As the driving current flows in the coil <NUM>, a magnetic field is generated inside the coil <NUM>. When the coil <NUM> generates a magnetic field, the movable part <NUM> moves in a direction (downward in the figure) that pushes out the spool <NUM> via the shaft <NUM> and moves in the opposite direction (upward in the figure) due to the biasing force of a spring (not shown) in the absence of the magnetic field. In other words, the position of the spool <NUM> (hereinafter, "spool position") changes in accordance with the driving voltage D1 in coordination with the position of the movable part <NUM>. The electromagnetic valve <NUM> controls the hydraulic actuator <NUM> by switching the channel of supplying hydraulic pressure in response to a change in the spool position. The hydraulic actuator <NUM> is controlled by the electromagnetic valve <NUM> to apply a hydraulic pressure to the piston <NUM> and drive the driven body <NUM> coupled to the piston <NUM>.

The position estimation apparatus <NUM> estimates the position of the spool of the electromagnetic valve <NUM>. The superior control system changes the control signal CNT in accordance with an estimation result Es from the position estimation apparatus <NUM>. When the amount of change of the spool position is insufficient, for example, the superior control system controls the driving unit <NUM> to increase the driving force of the solenoid <NUM>.

As shown in <FIG>, the position estimation apparatus <NUM> is provided with a supplying unit <NUM>, an acquisition unit <NUM>, and an estimation unit <NUM>. The supplying unit <NUM> supplies a high-frequency signal Sh to the solenoid <NUM> that drives the spool <NUM> of the electromagnetic valve <NUM>. The acquisition unit <NUM> acquires electrical information Je related to the solenoid <NUM> supplied with the high-frequency signal Sh. The estimation unit <NUM> estimates the position of the spool <NUM> by referring to a result of comparison between the electrical information Je acquired by the acquisition unit <NUM> and the high-frequency signal Sh supplied from the supplying unit <NUM>. The result of comparison between the electrical information Je and the high-frequency signal Sh is exemplified by an amplitude difference Cp described later.

<FIG> is a block diagram showing the estimation unit <NUM>. The functional blocks depicted in <FIG> and elsewhere are implemented in hardware exemplified by electronic devices or mechanical components such as a CPU of a computer, and in software such as a computer program. <FIG> depicts functional blocks implemented by the cooperation of these elements. Therefore, it will be understood by those skilled in the art that the functional blocks may be implemented in a variety of manners by a combination of hardware and software.

<FIG> is a block diagram showing the supplying unit <NUM>. The supplying unit <NUM> includes a signal generation unit <NUM> and a signal injection unit 20j. The signal generation unit <NUM> generates a source signal Gs originating the high-frequency signal Sh. The signal injection unit 20j amplifies the source signal Gs and superimposes the amplified signal on the driving voltage D0. The high-frequency signal Sh can have any of a variety of waveforms such as a sinusoidal wave, a rectangular wave, and a staircase wave that varies stepwise between three or more levels. The high-frequency signal Sh of this embodiment is a sinusoidal wave or a rectangular wave. The sinusoidal wave is not limited to a strictly sinusoidal wave and may encompass a waveform referred to a triangular wave or a trapezoidal wave.

<FIG> shows a waveform chart showing examples of the driving voltage D0, the high-frequency signal Sh, the driving voltage D1, and the current waveform Ic. The current waveform Ic is a current waveform of a driving current caused by the driving voltage D1 to flow in the coil <NUM> and is produced by the driving voltage D1. The driving voltage D0 is a PWM waveform having a high level and a low level, and the high-frequency signal Sh is a sinusoidal wave. The high level represents an ON period of the driving unit <NUM>, and the low level represents an OFF period of the driving unit <NUM>. The driving voltage D1 is superimposed on at least one of the high level and the low level of the driving voltage D0. The amplitude of the high-frequency signal Sh is configured to be smaller than the driving voltage D0. The frequency of the high-frequency signal Sh is set to a level that the solenoid <NUM> cannot respond to.

The high-frequency component of the current waveform Ic produced by the high-frequency signal Sh varies in accordance with the magnitude of the inductance of the coil <NUM>. For example, the amplitude of the high-frequency component of the current waveform Ic is large when the movable part <NUM> is distanced from the coil <NUM> and the inductance of the coil <NUM> is small (zone indicated A in <FIG>). The amplitude of the high-frequency component of the current waveform Ic is small when the movable part <NUM> is proximate to the coil <NUM> and the inductance of the coil <NUM> is large (zone indicated by B in <FIG>). Therefore, the position of the movable part <NUM> relative to the coil <NUM> (i.e., spool position) can be estimated by referring to the magnitude of the amplitude of the high-frequency component of the current waveform of the driving current Ic.

As shown in the example of <FIG>, it is desired that the repetition frequency of the PWM waveform be longer than the repetition frequency of the high-frequency signal Sh. By way of one example, the frequency of the high-frequency signal Sh may be <NUM> or higher when the frequency of the PWM waveform is <NUM>-<NUM>. The frequency of the high-frequency signal Sh is preferably twice the frequency of the PWM waveform or higher and, more preferably, four times the PWM frequency or higher and, still more preferably, ten times the PWM frequency or higher. If the frequency of the high-frequency signal Sh is excessively high, the operation of the estimation unit <NUM> may not be able to catchup, and a false operation may result. For this reason, the frequency of the high-frequency signal Sh may be <NUM> or lower.

The acquisition unit <NUM> in this example acquires, as the electrical information Je, the driving voltage D1 and the driving current Ic flowing in the coil <NUM>. Any of various current sensors like a direct-current current transformer (DCCT) and a current sense resistor can be employed as a sensor for sensing the driving current Ic. In the embodiment, a Hall element current sensor that converts a magnetic field produced around the driving current Ic into a voltage by utilizing Hall effect is used. This is advantageous in that an output proportional to the current ranging from a DC current to a high-frequency current can be obtained.

As shown in <FIG>, the estimation unit <NUM> includes a first reception unit 30a, a second reception unit 30b, a third reception unit 30c, a high-frequency component extraction unit 30e, an inverse electromotive force extraction unit 30f, an amplitude comparison unit <NUM>, and a position estimation unit 30j. The first reception unit 30a receives the high-frequency signal Sh from the supplying unit <NUM>. Of the electrical information Je acquired by the acquisition unit <NUM>, the second reception unit 30b receives the driving current Ic. Of the electrical information Je acquired by the acquisition unit <NUM>, the third reception unit 30c receives the driving voltage D1. The high-frequency component extraction unit 30e is a digital filter that extracts a frequency component Ih of the high-frequency signal Sh from the driving current Ic. By way of one example, the frequency component Ih can be extracted by using Fourier transform.

The inverse electromotive force extraction unit 30f extracts an inverse electromotive force Eb from the driving current Ic and the driving voltage D1. By way of one example, the inverse electromotive force Eb can be extracted through computation to obtain a difference between a result of multiplying the resistance value of the coil <NUM> by the driving current Ic (voltage drop) and the driving voltage D1. The amplitude comparison unit <NUM> compares the amplitude of the high-frequency signal Sh with the amplitude of the frequency component Ih and identifies an amplitude difference Cp therebetween. The amplitude comparison unit <NUM> can be configured by using a publicly known amplitude comparator. The position estimation unit 30j identifies the estimation result Es showing the spool position by referring to the amplitude difference Cp and using the correspondence relationship table 32d.

A storage unit <NUM> stores a correspondence relationship table 32d showing correspondence relationship between a position Ps of the spool <NUM> acquired in advance and the electrical information Je related to the solenoid <NUM> corresponding to the position Ps. The position Ps and the electrical information Je can be acquired in advance by an experiment, simulation, or a combination thereof. The storage unit <NUM> may be included in the estimation unit <NUM> or provided to be separate from the estimation unit <NUM> and connected to a publicly known information transmitting mechanism. One storage unit <NUM> may be provided in association with one position estimation apparatus <NUM>. Alternatively, one storage unit <NUM> may be provided in association with a plurality of position estimation apparatuses <NUM>.

The correspondence relationship table 32d will be described with reference to <FIG> schematically shows data in the correspondence relationship table 32d. Through our study, it has been discovered that there is certain correlation between the amplitude difference Cp and the position of the movable part <NUM> (spool position) since the inductance of the coil <NUM> varies and the amplitude of the driving current Ic responsive to the driving voltage D1 varies in accordance with the relative positions of the coil <NUM> and the movable part <NUM>.

The correspondence relationship table 32d of the embodiment shows correspondence relationship between the amplitude difference (Cp(<NUM>), Cp(<NUM>),. ) and the inverse electromotive force (Eb(<NUM>), Eb(<NUM>),. ) corresponding to the spool position (Ps(<NUM>), Ps(<NUM>),. ) measured in advance. The correspondence relationship table 32d can be generated based on measurement values determined by an experiment in advance. For example, a sensor for sensing the position of the spool <NUM> may be attached to the electromagnetic valve <NUM>, and the electromagnetic valve <NUM> may be activated to measure, while varying the spool position Ps, the amplitude difference Cp and the inverse electromotive force Eb corresponding to the spool position Ps.

The position estimation unit 30j refers to the correspondence relationship table 32d, using the amplitude difference Cp as a key, to determine the spool position Ps. In this example, the position estimation unit 30j also refers to the correspondence relationship table 32d, using the inverse electromotive force Eb as a key, to determine the spool position Ps. The position estimation unit 30j may output one of the spool position Ps identified from the amplitude difference Cp and the spool position Ps identified from the inverse electromotive force Eb as the estimation result Es or output both as the estimation result Es. In the embodiment, the position estimation unit 30j outputs an average of the spool position Ps identified from the amplitude difference Cp and the spool position Ps identified from the inverse electromotive force Eb as the estimation result Es. Since the spool position Ps is estimated based on a plurality of electrical information items, the estimation precision is high. Moreover, the inverse electromotive force Eb is substantially proportional to the moving speed of the movable part <NUM> so that the condition of deterioration of the electromagnetic valve <NUM>, the condition of load thereon, etc. can be known from the variation of the inverse electromotive force Eb.

Another example of the estimation unit <NUM>, which estimates the spool position Ps by using a position estimation model <NUM>, will be described with reference to <FIG>, <FIG>, and <FIG>. <FIG> is a block diagram showing another example of the estimation unit <NUM> and corresponds to <FIG>. <FIG> schematically shows a data set 32n of the position estimation model <NUM>. <FIG> schematically shows the position estimation model <NUM>. The position estimation unit 30j of <FIG> differs from the example of <FIG> in that the position estimation model <NUM> is used instead of the correspondence relationship table 32d to estimate the spool position Ps, and the other features are equal.

The position estimation model <NUM> is generated in advance by machine learning, based on the spool position Ps and the electrical information Je related to the solenoid <NUM> corresponding to the spool position Ps. In this example, a data set 32n, comprised of the spool position (Ps(<NUM>), Ps(<NUM>),. ), the amplitude difference (Cp(<NUM>), Cp(<NUM>),. ), the inverse electromotive force (Eb(<NUM>), Eb(<NUM>),. ), and the driving current (Ic(<NUM>), Ic(<NUM>),. ) acquired in advance, is defined as shown in <FIG>. The position estimation model <NUM> is generated through machine learning (supervised learning) by using the data set 32n as training data.

The position estimation model <NUM> can be generated by using a publicly known machine learning scheme such as a support vector machine, a neural network (including deep learning), a random forest, etc. The position estimation model <NUM> is stored in the storage unit <NUM>. The position estimation model <NUM> may be generated based on actual measurement values of the electromagnetic valve <NUM> or generated based on past actual measurement values collected for solenoid valves of the same type.

The position estimation unit 30j feeds, as shown in <FIG>, the amplitude difference Cp, the inverse electromotive force, the driving current Ic, which are newly acquired, to the position estimation model <NUM> as input data. The position estimation unit 30j obtains the spool position Ps as output data from the position estimation model <NUM>. The position estimation unit 30j outputs the spool position Ps obtained from the position estimation model <NUM> as the estimation result Es.

A description will be given of the feature of the position estimation apparatus <NUM> according to this embodiment configured as described above. The position estimation apparatus <NUM> includes the supplying unit <NUM> that supplies the high-frequency signal Sh to the solenoid <NUM> for driving the spool <NUM> of the electromagnetic valve <NUM>, the acquisition unit <NUM> that acquires the electrical information Je related to the solenoid <NUM> supplied with the high-frequency signal Sh, and the estimation unit <NUM> that estimates the position of the spool <NUM> based on the result of comparison between the electrical information Je acquired by the acquisition unit <NUM> and the high-frequency signal Sh supplied from the supplying unit <NUM>.

According to this configuration, the spool position of the electromagnetic valve can be estimated by using a simple configuration without using a position sensor. Therefore, the configuration is advantageous to reduce the size and weight. Further, the position is estimated based on a relative comparison result so that the impact from the variation of the high-frequency signal is canceled out, and the estimation precision is prevented from dropping. Still further, it is possible to estimate whether the mode of the hydraulic actuator is switched with high precision so that oversight of a latent failure mode can be prevented.

The position estimation apparatus <NUM> is provided with the storage unit <NUM> that stores information on the correspondence relationship between the position Ps of the spool <NUM> acquired in advance and the electrical information Je related to the solenoid <NUM> corresponding to the position Ps. The estimation unit <NUM> estimates the position Ps of the spool <NUM> by using the correspondence relationship information. In this case, the position is estimated by using the correspondence relationship information stored in advance so that high estimation precision is obtained.

The position estimation apparatus <NUM> is provided with the storage unit <NUM> that stores the position estimation model <NUM> generated by machine learning based on the position Ps of the spool <NUM> acquired in advance and the electrical information Je related to the solenoid <NUM> corresponding to the position Ps. The estimation unit <NUM> estimates the position Ps of the spool <NUM> by using the position estimation model <NUM>. In this case, estimation uses the position estimation model generated by machine learning in advance and so is advantageous to increase the speed of data processing and provides high estimation precision.

In this embodiment, the estimation unit <NUM> estimates the position Ps of the spool <NUM> based on the result of comparison between the frequency component Ch of the high-frequency signal Sh extracted by the digital filter from the electrical information Je and the high-frequency signal Sh. In this case, the position can be estimated based on the amplitude difference between the frequency component Ch and the high-frequency signal Sh. Therefore, the estimation precision is inhibited from dropping due to impact of environmental changes such as distortion in the waveform, temperature change, and time-dependent change.

In this embodiment, the high-frequency signal Sh is a sinusoidal wave or a rectangular wave. In this case, the wave is not easily affected by external random noise so that the estimation precision is inhibited from dropping due to external noise.

In this embodiment, the electrical information Je related to the solenoid <NUM> includes the inverse electromotive force Eb of the solenoid <NUM>. In this case, information on the moving speed of the movable part <NUM> can be extracted from the inverse electromotive force Eb so that the condition of deterioration of the electromagnetic valve <NUM> can be known by referring to the variation of the moving speed.

A description will now be given of a position control system <NUM> of the actuator apparatus <NUM> provided with the position estimation apparatus <NUM> of this embodiment. <FIG> is a block diagram showing the position control system <NUM> of the actuator apparatus <NUM>. The position control system <NUM> shown in <FIG> includes a first feedback loop <NUM> and a second feedback loop <NUM>. The first feedback loop <NUM> feeds back a position Pq of the piston <NUM> of the hydraulic actuator <NUM> of the actuator apparatus <NUM>. The second feedback loop <NUM> feeds back the estimation result Es of the spool position Ps of the electromagnetic valve <NUM>.

The first feedback loop <NUM> includes the hydraulic actuator <NUM>, an LVDT <NUM>, and a first error amplifier <NUM>. The LVDT <NUM> senses the position Pq of the piston <NUM>. The first error amplifier <NUM> amplifies a difference (piston position error) between a position instruction signal Acmd and the position Pq of the piston <NUM> and supplies a spool position instruction signal Pcmd to the driving unit <NUM>. The position instruction signal Acmd of the actuator is supplied from a superior control system. The first feedback loop <NUM> controls the position Pq of the piston <NUM> to follow the position instruction signal Acmd.

The second feedback loop <NUM> of the position control system <NUM> includes the position estimation apparatus <NUM>, the driving unit <NUM>, the electromagnetic valve <NUM>, and a second error amplifier <NUM>. The second error amplifier <NUM> amplifies a difference (spool position error) between the spool position instruction signal Pcmd and the estimation result Es and supplies the control signal CNT to the driving unit <NUM>. The driving unit <NUM> drives the electromagnetic valve <NUM> based on the control signal CNT. The electromagnetic valve <NUM> is driven by the driving unit <NUM> to drive the hydraulic actuator <NUM>. The second feedback loop <NUM> controls the estimation result Es to follow the instruction signal Pcmd.

A description will now be given of the second-fourth embodiments which do not fall within the scope of the claims. In the drawings and description of the second-fourth embodiments, constituting elements and members identical or equivalent to those of the first embodiment shall be denoted by the same reference numerals. Duplicative explanations are omitted appropriately and features different from those of the first embodiment will be highlighted.

The second embodiment of the present invention relates to the aircraft hydraulic actuator apparatus <NUM>. The actuator apparatus <NUM> includes the hydraulic actuator <NUM> for driving the driven body <NUM> of the airplane <NUM>, the electromagnetic valve <NUM> for controlling the hydraulic actuator <NUM>, the supplying unit <NUM> that supplies the high-frequency signal Sh to the solenoid <NUM> for driving the spool <NUM> of the electromagnetic valve <NUM>, the acquisition unit <NUM> that acquires the electrical information Je related to the solenoid <NUM> supplied with the high-frequency signal Sh, and the estimation unit <NUM> that estimates the position of the spool <NUM> based on the result of comparison between the electrical information Je acquired by the acquisition unit <NUM> and the high-frequency signal Sh supplied from the supplying unit <NUM>. The actuator apparatus <NUM> may be a system.

The second embodiment provides the same advantage and benefit as the first embodiment. The second embodiment also provides the aircraft hydraulic actuator apparatus with improved reliability since a position sensor is not necessary and the number of components is small.

The third embodiment of the present invention relates to a spool position estimation method S110 for the electromagnetic valve <NUM>. <FIG> is a flowchart showing an example of the position estimation method S110. The spool position estimation method S110 includes a step S112 of supplying the high-frequency signal Sh to the solenoid <NUM> for driving the spool <NUM> of the electromagnetic valve <NUM>, an acquisition step S114 of acquiring the electrical information Je related to the solenoid <NUM> supplied with the high-frequency signal Sh, and a step S116 of estimating the position of the spool <NUM> based on the result of comparison between the electrical information Je acquired in step S114 and the high-frequency signal Sh supplied.

The third embodiment provides the same advantage and benefit as the first embodiment.

The fourth embodiment of the present invention relates to a spool position estimation program (computer program) for an electromagnetic valve. The position estimation program according to this embodiment causes a computer to execute a process including: a step S112 of supplying the high-frequency signal Sh to the solenoid <NUM> for driving the spool <NUM> of the electromagnetic valve <NUM>, an acquisition step S114 of acquiring the electrical information Je related to the solenoid <NUM> supplied with the high-frequency signal Sh, and a step S116 of estimating the position of the spool <NUM> based on the result of comparison between the electrical information Je acquired in step S114 and the high-frequency signal Sh supplied.

The functions of the position estimation program according to this embodiment may be installed in a storage (not shown) of the position estimation apparatus <NUM> as an application program in which a plurality of modules corresponding to the functional blocks of the position estimation apparatus <NUM> are implemented. The position estimation program may be read into a main memory of a processor (e.g., a CPU) of a computer forming the estimation unit <NUM> of the position estimation apparatus <NUM>.

The fourth embodiment provides the same advantage and benefit as the first embodiment.

Claim 1:
A spool position estimation apparatus (<NUM>) comprising:
a supplying unit (<NUM>) that supplies a high-frequency signal (Sh) to a solenoid (<NUM>) for driving a spool (<NUM>) of an electromagnetic valve (<NUM>);
an acquisition unit (<NUM>) that acquires electrical information (Je) related to the solenoid (<NUM>) supplied with the high-frequency signal (Sh);
an estimation unit (<NUM>) that estimates a position of the spool (<NUM>) based on a result of comparison between the electrical information (Je) acquired by the acquisition unit (<NUM>) and the high-frequency signal (Sh) supplied from the supplying unit (<NUM>); characterized by
a driving unit (<NUM>) that outputs a driving PWM voltage (D0) on which the high-frequency signal (Sh) is superimposed to produce a driving voltage (D1) to drive the solenoid (<NUM>).