Electrically powered suspension system

An electrically powered suspension system 11 achieves vibration control of a vehicle without disturbing a vehicle behavior and impairing riding comfort even if an electric motor 31 of an electromagnetic actuator 13 generates excessive heat, wherein the electromagnetic actuator 13 includes the electric motor 31 generating a driving force for vibration damping and extension/contraction; a target damping force setting part 51 setting a target damping force; a target extension/contraction setting part 53 setting a target extension/contraction force; and a drive controller 49 performing the drive control of the electric motor 31 using a drive force based on the target damping force and target extension/contraction force by limiting the motor current not to exceed a current threshold that is an addition of a damping current threshold and extension/contraction current threshold, which thresholds are separately configured considering a priority of riding comfort and steering stability.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of foreign priority to Japanese Patent Application No. 2019-076547, filed on Apr. 12, 2019, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an electrically powered suspension system including an electromagnetic actuator. The electromagnetic actuator is disposed between a vehicle body and a wheel and includes an electric motor that generates a driving force used for vibration damping and extension/contraction.

BACKGROUND ART

A conventionally well-known electrically powered suspension system includes an electromagnetic actuator that is installed between a vehicle body and a wheel, and includes an electric motor generating a driving force used for vibration damping and extension/contraction (for example, see PTL 1). The electromagnetic actuator includes a ball screw mechanism in addition to the electric motor. The electromagnetic actuator operates to generate a driving force for the vibration damping and extension/contraction by converting rotary motion of the electric motor into linear motion of the ball screw mechanism.

Here, the driving force used for the vibration damping is called as a damping force. The damping force means a force directed to a different direction from a direction of a stroke speed of the electromagnetic actuator. On the other hand, the driving force used for the extension/contraction is called as an extension/contraction force. The extension/contraction force means a force generated regardless of the direction of the stroke speed.

In addition, another technique is known, to protect a motor mounted on the vehicle from damage by constantly monitoring a temperature of the motor and determining the motor current is in an excessive heat generation state and then limiting the motor current if the temperature of the motor exceeds a predetermined temperature (for example, see PTL 2).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Here, it is assumed that the electrically powered suspension system according to PTL 1 is provided with a motor protection technology according to PTL 2, to perform damping control of an electromagnetic actuator having an electric motor as a driving force source. In such a motor protection technology, the electric motor is assumed to be in an excessive heat generation state. And, a value of a drive current supplied to the electric motor is uniformly limited with a predetermined limitation threshold in order to protect the electric motor from damage.

In such a case of the excessive heat generation state, the damping force generated by the electromagnetic actuator becomes weaker than in a normal state. Then, the unsprung vibration becomes not sufficiently suppressed. As a result, the behavior of the vehicle may be disturbed.

Similarly, the extension/contraction force of the electromagnetic actuator is weakened in the excessive heat generation state as compared with the normal state. Then, for example, the vehicle may not be kept in a stable posture based on a skyhook control. This result in a possibility that riding comfort of the vehicle may be impaired.

The present invention is made in view of the above problems, and an object of the present invention is to provide an electrically powered suspension system capable of performing vibration control of a vehicle without disturbing a behavior of the vehicle and without impairing the riding comfort of the vehicle as much as possible even when the electric motor provided in the electromagnetic actuator is in an excessive heat generation state.

Solution to Problem

In order to achieve the above object, the present invention provides an electrically powered suspension system comprising: an electromagnetic actuator disposed between a vehicle body and a wheel and including an electric motor generating a driving force used for vibration damping and for extension/contraction; a damping force calculator calculating a target damping force that is a target value of the vibration damping used for the electromagnetic actuator; an extension/contraction force calculator calculating a target extension/contraction force that is a target value of the extension/contraction of the electromagnetic actuator; a drive controller that performs drive control of the electric motor using a target driving force based on the damping force calculated by the damping force calculator and the target extension/contraction force calculated by the extension/contraction force calculator, wherein the drive controller performs a drive control to limit a drive current for the electric motor so that a current correlation value correlated with the drive current for the electric motor does not exceed a predetermined current limitation threshold; and the current limitation threshold includes a damping current limitation threshold for acquiring a target driving force based on the target damping force and an extension/contraction current limitation threshold for acquiring a target driving force based on the target extension/contraction force; and the damping current limitation threshold and the extension/contraction current limitation threshold may be set separately.

Advantageous Effects of Invention

The present invention allows an electrically powered suspension system to perform vibration control of a vehicle without disturbing a behavior of the vehicle and without impairing riding comfort of the vehicle as much as possible even when the electric motor provided in the electromagnetic actuator is in an excessive heat generation state.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, description is given of an electrically powered suspension system according to an embodiment of the present invention in detail with reference to the drawings as appropriate.

In the drawings described below, members having functions common thereto are denoted by common reference numerals. Further, a size and shape of the member may be schematically represented by deformation or exaggeration for convenience of explanation.

<Basic Configuration Common to All Embodiments of the Present Invention>

First, description is given of a basic configuration common to all the electrically powered suspension systems11according to embodiments of the present invention with reference toFIGS. 1 and 2.

FIG. 1is a diagram showing the overall configuration of an electrically powered suspension system11according to one embodiment of the present invention.FIG. 2is a partially sectional view of an electromagnetic actuator13partially constituting the electrically powered suspension system11.

As shown inFIG. 1, the electrically powered suspension system11according to the embodiment of the present invention includes a plurality of electromagnetic actuators13provided for respective wheels10and one electronic control device (hereinbelow, referred to as “ECU”)15. The ECU15is connected with each of the plurality of the electromagnetic actuators13through a power supply line14(see a solid line inFIG. 1) supplying drive control power from the ECU15to each electromagnetic actuators13and a signal line16(see a broken line inFIG. 1) transmitting a rotation angle signal of the electric motor31(seeFIG. 2).

In the present embodiment, four of the electromagnetic actuators13are provided respectively to the wheels including front wheels (front right wheel, front left wheel) and rear wheels (rear right wheel, rear left wheel). The electromagnetic actuators13provided for each wheel are driven and controlled separately from each other in each synchronization with the extension/contraction for each wheel.

In the embodiment of the present invention, unless otherwise stated, each of the plurality of electromagnetic actuators13has a configuration common to each other. Therefore, all the plurality of electromagnetic actuators13are described by explaining a configuration of one electromagnetic actuator13.

As shown inFIG. 2, the electromagnetic actuator13includes a base housing17, an outer tube19, a ball bearing21, a ball screw shaft23, a plurality of balls25, a nut27, and an inner tube29.

The base housing17rotatably supports a base end portion of the ball screw shaft23around it with interposition of the ball bearing21. The outer tube19is provided on the base housing17and accommodates a ball screw mechanism18including the ball screw shaft23, the plurality of balls25, and the nut27. The plurality of balls25roll along a screw groove of the ball screw shaft23. The nut27is engaged with the ball screw shaft23with interposition of the plurality of balls25, and converts rotational motion of the ball screw shaft23into linear motion. The inner tube29connected to the nut27is integrated with the nut27and displaceable in an axial direction of the outer tube19.

As seen inFIG. 2, the electromagnetic actuator13includes the electric motor31, a pair of pulleys33, and a belt member35in order to transmit a rotational driving force to the ball screw shaft23. The electric motor31is provided on the base housing17so as to be arranged in parallel with the outer tube19. The pulleys33are respectively attached to a motor shaft31aof the electric motor31and the ball screw shaft23. The belt member35for transmitting the rotational driving force of the electric motor31to the ball screw shaft23is put round the pair of pulleys33.

The electric motor31is provided with a resolver37for detecting a rotation angle of the electric motor31. The rotation angle of the electric motor31detected by the resolver37is sent to the ECU15via the signal line16. The electric motor31is controlled in its rotational driving force by the ECU15in accordance with the drive control power to be supplied to each of the plurality of electromagnetic actuators13via the power supply line14.

According to this embodiment, as seen inFIG. 2, a dimension in the axial direction of the electromagnetic actuator13is shortened by employing a layout in which the motor shaft31aof the electric motor31and the ball screw shaft23are arranged substantially in parallel and connected with each other. However, another layout may be employed in which, for example, the motor shaft31aof the electric motor31and the ball screw shaft23are coaxially arranged and connected to each other.

As seen inFIG. 2, the electromagnetic actuator13according to this embodiment has a connecting portion39provided at a lower end of the base housing17. The connecting portion39is connected and fixed to an unsprung member (not shown) such as a lower arm and a knuckle provided on the wheel. On the other hand, an upper end portion29aof the inner tube29is connected and fixed to a sprung member (not shown) such as a strut tower portion provided on the vehicle body. In other words, the electromagnetic actuator13is arranged in parallel with a spring member (not shown) provided between the body and the wheel of the vehicle10. The sprung member is provided with a sprung acceleration sensor40(seeFIG. 3) detecting the acceleration of the vehicle body (sprung) along the stroke direction of the electromagnetic actuator13.

The electromagnetic actuator13configured as described above operates as follows. For example, it is assumed that momentum relating to upward vibration is inputted to the connecting portion39from a wheel of the vehicle10. In this case, the inner tube29and the nut27are about to together descend with respect to the outer tube19to which the momentum relating to the upward vibration has been applied. In response to the above momentum, the ball screw shaft23tries to rotate in a direction following the descending of the nut27. At this time, the rotational driving force of the electric motor31is generated in a direction preventing the nut27from descending. The rotational driving force of the electric motor31is transmitted to the ball screw shaft23via the belt member35.

In this way, the vibration transmitted from the wheel to the vehicle body is damped by applying a reaction force (damping force) that is against the momentum relating to the upward vibration to the ball screw shaft23.

<Configuration of Internal and Peripheral Parts of ECU15>

Next, an internal configuration and a peripheral configuration of the ECU15equipped in the electrically powered suspension system11is described with reference toFIGS. 3, 4A, 4B, 5A, and 5B.

FIG. 3is a diagram showing the internal configuration and peripheral configurations of the ECU15equipped in the electrically powered suspension system11.FIG. 4Ais a diagram conceptually illustrating an internal configuration of a driving force calculator47A according to the embodiment provided in the ECU15of the electrically powered suspension system11.FIG. 4Bis an explanatory diagram conceptually showing a damping force map describing a relationship between a stroke speed SV and a target damping force that changes accompanying with a change in the stroke speed SV.FIG. 5Ais an explanatory diagram conceptually illustrating a pre/post-limitation target value map61according to an embodiment that describes a relationship between forces before and after limitation of the target damping force and the target extension/contraction force when receiving a control current limitation command signal.FIG. 5Bis an explanatory diagram conceptually illustrating a pre/post-limitation target value map63according to a modification that describes a relationship between forces before and after limitation of the target damping force and the target extension/contraction force when receiving the control current limitation command signal.

The ECU15includes a microcomputer configured to perform various arithmetic processing. The ECU15has a drive control function of generating a driving force used for vibration damping of the vehicle by controlling driving of each of the plurality of electromagnetic actuators13, for example, based on a rotation angle of the electric motor31detected by the resolver37.

In order to achieve such a driving-control function, as seen inFIG. 3, the ECU15includes an information acquisition part43, a driving force calculator47, and a drive controller49.

In the present embodiment, the ECU15corresponds to the “drive control unit” described in CLAIMS of the present invention.

As shown inFIG. 3, the information acquisition part43acquires the rotation angle signal of the electric motor31detected by the resolver37as time-series information relating to a stroke position, and acquires information on a stroke velocity SV by time-differentiating the time-series information of the stroke position.

Further, as shown inFIG. 3, the information acquisition part43acquires information on the ECU temperature Te detected by an ECU temperature sensor44provided on, for example, a substrate of the ECU15, and information of the motor temperature Tm detected by a motor temperature sensor46provided on, for example, the housing of the electric motor31.

However, the information on the ECU temperature Te (including the information on an ambient temperature around the ECU15) is used by a driving force calculator47B according to a first modification described below. Further, the information on the motor temperature Tm (including information on the ambient temperature around the electric motor31) is used by a driving force calculator47C according to a second modification described below. Therefore, the information acquisition part43included in the electrically powered suspension system11according to the embodiment can omit the acquisition of the information on the ECU temperature Te and the motor temperature Tm.

Further, as shown inFIG. 3, the information acquisition part43acquires time-series information on sprung acceleration detected by a sprung acceleration sensor40; and information on a sprung speed BV by time-integrating the time-series information on the sprung acceleration.

Further, as shown inFIG. 3, the information acquisition part43acquires vehicle speed information detected by the vehicle speed sensor41, yaw rate information detected by the yaw rate sensor42, and information on a motor current supplied to the electric motor31to achieve the target driving force of the electromagnetic actuator13.

The above types of the information acquired through the information acquisition part43, such as the information on the stroke speed SV, the information on the ECU temperature and the motor temperature, the information on the sprung speed BV, the information on the vehicle speed, the information on the yaw rate, and the information on the motor current, are respectively sent to the driving force calculator47.

The driving force calculator47A of the embodiment, as shown inFIG. 4A, includes a target damping force setting part51, a target damping force limiting part52, a target extension/contraction force setting part53, a target extension/contraction force limiting part54, a state determination part55, and an adder57.

The driving force calculator47A of the embodiment basically works to calculate respectively a target damping force that is a target value of the vibration damping of the electromagnetic actuator13; and a target extension/contraction force that is a target value of the extension/contraction operation, and to calculate a target driving force necessary for the vibration damping and the extension/contraction of the electromagnetic actuator13so as to achieve the target damping force and target extension/contraction force calculated.

Here, the driving force calculator47A of the embodiment performs state determination on whether or not the electric motor31is in an excessive heat generation state based on information of a integrated motor current value Tint (detailed below) acquired by performing time-integration of time-series information on the motor current.

However, the state determination on whether or not the electric motor31is in the excessive heat generation state may be performed based on the information on the ECU temperature Te acquired in a predetermined cycle (detailed below as the driving force calculator47B according to the first modification), or performed based on the information on the motor temperature Tm acquired in a predetermined cycle (detailed below as the driving force calculator47C according to the second modification).

Furthermore, the state determination on whether or not the electric motor31is in the excessive heat generation state may be performed based on information on an ECU temperature integrated value Teint acquired by time-integrating the time series information relating to the ECU temperature Te acquired in a predetermined cycle; or based on information of a motor temperature integrated value Tmint acquired by time-integrating the time-series information on the motor temperature Tm acquired at a predetermined cycle.

Note that in the present specification, the driving force calculator47A of the embodiment, the driving force calculator47B according to the first modification, and the driving force calculator47C according to the second modification are collectively referred to as “driving force calculator47”.

The driving force calculator47of the present embodiment corresponds to a “current calculator” of Claims of the present invention.

More specifically, the target damping force setting part51provided in the driving force calculator47A of the embodiment configures a value of the target damping force responsive to the stroke speed SV based on the information on the stroke speed SV acquired via the information acquisition part43and a target damping force map51A (seeFIG. 4B) conceptually representing a relationship between the target damping force and the stroke speed in which the target damping force varies in response to variations of the stroke speed. The target damping force map51A stores in an actual implementation a target value of a damping force control current (a value of the target damping current) as a value corresponding to the value of the target damping force.

As seen inFIG. 4B, a domain of the stroke velocity SV of the target damping force map51includes a normal use region SV1and non-normal use regions SV2. The normal use region SV1is a velocity region in which a magnitude of the stroke velocity SV is equal to or smaller than a normal use velocity threshold SVTh (|SV|−SVTh≤0). During the regular running of the vehicle, most values of the stroke velocity SV converge into the normal use region SV1.

The normal use velocity threshold SVTh may be configured to an appropriate value by consulting an evaluation result acquired by evaluating a probability density function of the stroke velocity SV through experiments, simulations, and the like; and by considering that a predetermined distribution ratio is satisfied by a distribution ratio of the stroke velocity SV appearing respectively in the normal use region SV1and the non-normal use regions SV2.

As seen inFIG. 4B, a target damping force characteristic relating to the target damping force map51A in the normal use region SV1has a characteristic such that the target damping force directed toward a contraction direction increases substantially linearly as the stroke velocity SV increases toward an extension direction, whereas the target damping force directed toward the extension direction increases substantially linearly as the stroke velocity SV increases toward the contraction direction. This characteristic is made similar to a damping characteristic of a conventionally used hydraulic damper. Note that the corresponding target damping force is also zero when the stroke velocity SV is zero.

A target damping force characteristic of the non-normal use region SV2in the target damping force map51A, as seen inFIG. 4B, similarly to the target damping force characteristic of the normal use region SV1in the target damping force map51A, has a characteristic such that the target damping force directed toward the contraction direction increases substantially linearly as the stroke velocity SV increases toward the extension direction, whereas the target damping force directed toward the extension direction increases substantially linearly as the stroke velocity SV increases toward the contraction direction.

However, as seen inFIG. 4B, the target damping force characteristic in the non-normal use region SV2of the target damping force map51A is configured to have a gentle slope as compared with a slope of the target damping force characteristic in the normal use region SV1of the target damping force map51A.

On the other hand, the target extension/contraction force setting part53provided in the driving force calculator47A of the embodiment configures a value of the target extension/contraction force responsive to the sprung speed BV acquired by the information acquisition part43and a target extension/contraction force map53A (seeFIG. 4C) conceptually representing a relationship between the sprung speed BV and the target extension/contraction force that varies accompanying with variations of the sprung speed BV. Note that the target extension/contraction force map in an actual implementation stores a target value of an extension/contraction control current (a value of the target extension/contraction current) as a value corresponding to the target extension/contraction force.

As shown inFIG. 4C, the target extension/contraction force characteristic according to the target extension/contraction force map53A exhibits a characteristic in which the target extension/contraction force directed toward a contraction direction increases linearly as the sprung speed BV increases toward the extension direction, while the target extension/contraction force directed toward an extension direction linearly increases as the sprung speed BV increases toward the contraction direction.

Note that the target extension/contraction force characteristic according to the target extension/contraction force map53A may be acquired by performing experiments/simulations and the like for acquiring the target extension/contraction force responsive to the sprung speed BV in order to keep a posture of the vehicle10in a predetermined state; and configure an appropriate characteristic value acquired by the experiments/simulations, etc. as appropriate.

The state determination part55provided in the driving force calculator47A of the embodiment acquires the time-series information of the motor current via the information acquisition part43, and the information of the integrated motor current value Iint by time-integrating the time-series information of the motor current. A range (time length) to be subjected to the time-integration may be configured to an appropriate time length (for example, three to ten minutes retroactively) in consideration of a heat capacity, heat radiation characteristics, and the like of the electric motor31.

Further, the state determination part55performs a state determination on whether or not the integrated motor current value Iint exceeds a integrated current threshold Iint_th, that is, whether or not the electric motor31is in an excessive heat generation state, based on information such as the information of the integrated motor current value Iint acquired.

If the state determination result is that the integrated motor current value Iint exceeds the integrated current threshold Iint_th, that is, the electric motor31is in the excessive heat generation state, the state determination part55sends a control current limiting command signal indicating that the control current for achieving the driving force used for the damping and extension/contraction forces is to be limited respectively to the target damping force limiting part52and the target extension/contraction force limiting part54.

Upon receiving the control current limiting command signal that is sent from the state determination part55, the target damping force limiting part52calculates a value of a target damping force after limitation (target damping current) based on the value of the target damping force set by the target damping force setting part51and the pre/post-limitation target value maps61A (seeFIGS. 4A and 5A) according to the embodiment conceptually showing the relationship between values before and after target values of the damping force and the extension/contraction force are limited when the target damping force setting part51receives the control current limiting command signal. Note that the pre/post-limitation target value map61A stores actually a target value of the damping force control current (value of target damping current) as a value equivalent to the value of the target damping force after limitation.

On the other hand, the target extension/contraction force limiting part54, upon receiving the control current limiting command signal sent from the state determination part55, calculates a value of a target extension/contraction force after limitation (target extension/contraction current) based on the value of the target extension/contraction force set by the target extension/contraction force setting part53and the pre/post-limitation target value map61B (seeFIGS. 4A and 5A) according to the embodiment. Note that the pre/post-limitation target value map61stores actually a target value of the extension/contraction force control current (value of target extension/contraction current) as a value equivalent to the value of the target extension/contraction force after limitation.

Here, the pre/post-limitation target value map61A according to the embodiment, to which the target damping force limitation part52refers when calculating the value of the target damping force (target damping current) after limitation, and the pre/post-limitation target value map61B according to the embodiment, to which the target extension/contraction force limitation part54refers when calculating the value of the target extension/contraction force (target extension/contraction current) after limitation, may be configured as commonly accessible information, or may be configured as separate information.

The following description is given of an example in which the pre/post-limitation target value maps61A and61B (these are collectively referred to as “pre/post-limitation target value map61”) according to the embodiment are configured as commonly accessible information.

Further, the calculation of the target damping force after limitation calculated by the target damping force limitation part52and the calculation of the target extension/contraction force after limitation by the target extension/contraction force limitation part54are performed independently. As a result, a calculation result of the target damping force after limitation calculated by the target damping force limitation part52and a calculation result of the target extension/contraction force after limitation by the target extension/contraction force limitation part54have respectively independent values.

As shown inFIG. 4A, the adder57provided in the driving force calculator47A of the embodiment adds the target damping force after limitation calculated by the target damping force limitation part52and the target extension/contraction force after limitation calculated by the target extension/contraction force limitation part54to acquire the target driving force and further acquires a driving control signal for achieving the target driving force by calculation. The drive control signal, which is a calculation result acquired by the driving force calculator47A of the embodiment, is sent to the drive controller49.

The drive controller49performs drive control of each of the plurality of the electromagnetic actuators13separately by supplying a drive control power to the electric motor31provided in each of the plurality of electromagnetic actuators13in accordance with the drive control signal sent from the driving force calculator47A of the embodiment.

Note that generating the drive control power to be supplied to the electric motors31may use, for example, an inverter control circuit as appropriate.

Next, description is given of the pre/post-limitation target value map61according to the embodiment.

In the pre/post-limitation target value map61according to the embodiment, a domain TVB of pre-limitation target value (hereinbelow, sometimes abbreviated as “pre-limitation target value”) includes, as indicated on a horizontal axis ofFIG. 5A, the first pre-limitation target value TVb1, the second pre-limitation target value TVb2, and the third pre-limitation target value TVb3(where TVb1>TVb2>TVb3).

The domain TVB of the pre-limitation target value includes a first domain TVB-1from zero to a first pre-limitation target value TVb1; a second domain TVB-2from zero to a second pre-limitation target value TVb2; and a third domain TVb-3from zero to a third pre-limitation target value TVb3.

On the other hand, a value range TVA of a post-limitation target value includes a first post-limitation target value TVa1, a second post-limitation target value TVa2, and a third post-limitation target value TVa3configured as TVa1>TVa2>TVa3, as shown in a vertical axis ofFIG. 5A.

The value range TVA relating to the post-limitation target value includes a first value range TVA-1from zero to the first post-limitation target value TVa1, a second value range TVA-2from zero to the second post-limitation target value TVa2, and a third value range TVA-3from zero to the third post-limitation target value TVa3.

The domain TVB of the pre-limitation target value and the value range TVA of-the post-limitation target value are associated with each other via a predetermined function.

Note that the first to sixth domains TVB-1to TVB-6relating to the pre-limitation target values may be simply referred to as the domain TVB of the pre-limitation target value when there is no need to individually specify them.

Further, the first to three value ranges TVA-1to TVA-3relating to the post-limitation target value may be simply referred to as the value range TVA relating to the post-limitation target value when there is no need to individually specify them.

More specifically, the first to third domains TVB-1, TVB-2, and TVB-3(detailed below) of the pre-limitation target values are respectively associated with the first to third value ranges TVA-1, TVA-2, and TVA-3(detailed below) of the post-limitation target value via a predetermined (commonly configured) linear function F1along with a vertical axis ofFIG. 5A.

On the other hand, the fourth to sixth domains TVB-4, TVB-5, and TVB-6(detailed below) of the pre-limitation target values are associated respectively with the first to third post-limitation target values: fixed values TVa1, TVa2, and TVa3(TVa1>TVa2>TVa3) via respective many-to-one functions as shown in the vertical direction ofFIG. 5A.

The first domain TVB-1is a domain relating to the target values before limitation of the damping force and the extension/contraction force in the normal state in which the electric motor31is not in the excessive heat generation state.

The pre-limitation target values of the damping force and the extension/contraction force belonging to the first domain TVB-1can be mapped with one-to-one association to the post-limitation target values of the damping force and the extension/contraction force belonging to the first value range TVA-1using the predetermined linear function F1. For example, the first pre-limitation target value TVb1can be mapped to the first post-limitation target value TVa1.

The second domain TVB-2is a domain relating to the pre-limitation target value of the damping force at a time of abnormality when the electric motor31is in the excessive heat generation state.

At the time of abnormality, the pre-limitation target value of the damping force belonging to the second domain TVB-2is mapped with one-to-one association to the post-limitation target values of the damping force belonging to the second value range TVA-2via a predetermined linear function F1. For example, the second pre-limitation target value TVb2of the damping force is mapped to the second post-limitation target value TVa2of the damping force.

The second domain TVB-3is a domain relating to the pre-limitation target value of the damping force at a time of abnormality when the electric motor31is in the excessive heat generation state.

At the time of abnormality, the pre-limitation target value of the damping force belonging to the second domain TVB-3is mapped with one-to-one association to the post-limitation target values of the damping force belonging to the second value range TVA-3via a predetermined linear function F1. For example, the second pre-limitation target value TVb3of the damping force is mapped to the second post-limitation target value TVa3of the damping force.

Further, as shown on the horizontal axis ofFIG. 5A, the domain TVB of the pre-limitation target value includes the fourth domain TVB-4exceeding the first pre-limitation target value TVb1, and the fifth domain TVB-5exceeding the second pre-limitation target value TVb2, and the sixth domain TVB-6exceeding the third pre-limitation target value TVb3.

The fourth domain TVB-4is, similarly to the first domain TVB-1, a domain relating to the target values before limitation of the damping force and the extension/contraction force at the normal time when the electric motor31is not in the excessive heat generation state. However, the fourth domain TVB-4differs from the first domain TVB-1in that the fourth domain TVB-4occupies a domain relating to the pre-limitation target value having the larger target value than that of the first domain TVB-1. A combination of the first domain TVB-1and the fourth domain TVB-4is included by a domain relating to the target values before limitation of the damping force and the extension/contraction force in the normal time.

In the normal time, the target values before limitation of the damping force and the extension/contraction force that belong to the fourth domain TVB-4are mapped to the first post-limitation target value TVa1of the damping force and the extension/contraction force that are the fixed target value via the predetermined many-to-one function. The purpose of the above configuration is to limit the post-limitation target value to a levelled value irrespective of an increase in the pre-limitation target value in order to suppress an endless increase in the damping force and the extension/contraction force by setting the post-limitation target value to a fixed value: the first post-limitation target value TVa1in the fourth domain TVB-4having the larger pre-limitation target value than the first domain TVB-1.

The fifth domain TVB-5is, similarly to the second domain TVB-2, a domain relating to the pre-limitation target value of the damping force when the electric motor31is in an abnormal state in which an excessive heat is generated. However, the fifth domain TVB-5differs from the second domain TVB-2in that the fifth domain TVB-5occupies a domain relating to the pre-limitation target value having the larger target value than that of the second domain TVB-2in the domain relating to the pre-limitation target value. A combination of the second domain TVB-2and the fifth domain TVB-5is included by a domain relating to the target values before limitation of the damping force in the time of abnormality.

At the time of abnormality, the target values before limitation of the damping force belonging to the fifth domain TVB-5are mapped to the second post-limitation target value TVa2of the damping force that are the fixed value via the predetermined many-to-one function (see the solid line portion indicating the target damping force characteristic after limitation in the pre/post-limitation target value map61according to the embodiment shown inFIG. 4A). The purpose of the above configuration is to limit the post-limitation target value to a levelled value irrespective of an increase in the pre-limitation target value to suppress an endless increase in the damping force by setting the post-limitation target value to a fixed value: the second post-limitation target value TVa2, in the fifth domain TVB-5having the larger pre-limitation target value than the second domain TVB-2.

The sixth domain TVB-6is, similarly to the third domain TVB-3, a domain relating to the pre-limitation target value of the extension/contraction force when the electric motor31is in an abnormal state in which an excessive heat is generated. However, the sixth domain TVB-6differs from the third domain TVB-3in that the sixth domain TVB-6occupies a domain relating to the pre-limitation target value having the larger target value than that of the third domain TVB-3in the domain relating to the pre-limitation target value. A combination of the third domain TVB-3and the sixth domain TVB-6is included by a domain relating to the target values before limitation of the extension/contraction force in the time of abnormality.

At the time of abnormality, the target values before limitation of the extension/contraction force that belong to the sixth domain TVB-6are mapped to the third post-limitation target value TVa3of the extension/contraction force that are the fixed value via the predetermined many-to-one function (see the solid line portion indicating the target extension/contraction force characteristic after limitation in the pre/post-limitation target value map61according to the embodiment shown inFIG. 4A. The purpose of the above configuration is to limit the post-limitation target value to a levelled value irrespective of an increase in the pre-limitation target value to suppress an endless increase in the extension/contraction force by setting the post-limitation target value to a fixed value: the third post-limitation target value TVa3in the sixth domain TVB-6having the larger pre-limitation target value than the third domain TVB-3.

The pre/post-limitation target value map61according to the embodiment, as shown inFIGS. 4A and 5A, describes how the target values before limitation of the damping force and the extension/contraction force are mapped to the post-limitation target values of the damping force and the extension/contraction force in the normal state: when the electric motor31is not in the excessive heat generation state and in the abnormal state: when the electric motor31is in an excessive heat generation state.

That is, in the normal state, the pre-limitation target values of the damping force and the extension/contraction force belonging to the first domain TVB-1are mapped to the post-limitation target values of the damping force and the extension/contraction force belonging to the first value range TVA-1using the predetermined linear function F1; and the pre-limitation target values of the damping force and the extension/contraction force belonging to the fourth domain TVB-4are mapped to the fixed first post-limitation target values TVa1of the damping force and the extension/contraction force through a predetermined many-to-one function.

The operation at the time of abnormality, which is paired with the normal time, is described separately about the damping force and the extension/contraction force.

First, about the damping force at the time of abnormality, description is given of how the pre-limitation target value is mapped to the post-limitation target value.

At the time of abnormality, the pre-limitation target value of the damping force belonging to the second domain TVB-2is mapped to the post-limitation target value of the damping force belonging to the second value range TVA-2through the predetermined linear function F1, and the pre-limitation target value of the damping force belonging to the fifth domain TVB-5is mapped to the fixed post-limitation target value TVa2of the damping force through the predetermined many-to-one function.

Next, about the extension/contraction force at the time of abnormality, description is given of how the post-limitation target value is mapped to the pre-limitation target value.

At the time of abnormality, the pre-limitation target value of the extension/contraction force belonging to the third domain TVB-3is mapped to a post-limitation target value of the extension/contraction force belonging to the third value range TVA-3through a predetermined linear function F1; and the pre-limitation target value of the extension/contraction force belonging to the sixth domain TVB-6is mapped to a fixed post-limitation target value TVa3of the extension/contraction force through a predetermined many-to-one function.

In another aspect of view,FIG. 5Ashows that the pre/post-limitation target value map61according to the embodiment is configured so that the post-limitation target value of the extension/contraction force at the time of abnormality (extension/contraction current limitation threshold: the third post-limitation target value TVa3) is smaller than the post-limitation target value of the damping force at the time of the abnormality (damping current limitation threshold: the second post-limitation target value TVa2).

Next, description is given of the pre/post-limitation target value map63according to a modification with reference toFIG. 5B.

FIG. 5Bis an explanatory diagram of a pre/post-limitation target value map63according to a modification that conceptually illustrates a relationship between the target values before and after limitation of the damping force and the extension/contraction force when receiving the control current limiting command signal.

The pre/post-limitation target value map61according to the embodiment shown inFIG. 5Aand the pre/post-limitation target value map63according to the modification shown inFIG. 5Bhave many common characteristics.

Therefore, description is given of the pre/post-limitation target value map63according to the modification by focusing on differences between the pre/post-limitation target value map61according to the embodiment and the pre/post-limitation target value map63according to the modification and by describing mainly the differences.

In the pre/post-limitation target value map63according to the modification, a domain TVB of the pre-limitation target value has the eleventh pre-limitation target value TVb11, the twelfth pre-limitation target value TVb12, and the thirteenth pre-limitation target value TVb13respectively configured so that their values are as TVb11<TVb12<TVb13.

The domain TVB of the pre-limitation target value includes an eleventh domain TVB-11from zero to the eleventh pre-limitation target value TVb11, a twelfth domain TVB-12from zero to the twelfth pre-limitation target value TVb12, and a thirteenth domain TVB-13from zero to the thirteenth pre-limitation target value TVb13.

On the other hand, the value range TVA relating to the post-limitation target value has an eleventh post-limitation target value TVa11, a twelfth post-limitation target value TVa12, and a thirteenth post-limitation target value TVa13respectively configured so that their values are as TVa11>TVa12>TVa13, as indicated on the vertical axis inFIG. 5B.

The value range TVA relating to the post-limitation target value includes an eleventh value range TVA-11from zero to the eleventh post-limitation target value TVa11, a twelfth value range TVA-12from zero to the twelfth post-limitation target value TVa12, and a thirteenth value range TVA-13from zero to the thirteenth post-limitation target value TVa13.

The domain TVB of the pre-limitation target value and the range TVA of the post-limitation target value are associated with each other respectively through predetermined different functions F11, F12, and F13.

A difference of the pre/post-limitation target value map63according to the modification from the pre/post-limitation target value map61according to the embodiment is that the domain TVB of the pre-limitation target value and the value range TVA relating to the post-limitation target value are associated with each other respectively through the predetermined different functions F11, F12, and F13.

More specifically, the eleventh to thirteenth domains TVB-11, TVB-12, and TVB-13relating to the pre-limitation target value are mapped respectively to the eleventh to thirteenth value ranges TVA-11, TVA-12, and TVA-13of the post-limitation target value respectively through the different predetermined functions F11, F12, and F13along the vertical axis ofFIG. 5B.

The eleventh domain TVB-11is a domain relating to the pre-limitation target values of the damping force and the extension/contraction force at the normal time when the electric motor31is not in the excessive heat generation state.

The pre-limitation target values of the damping force and the extension/contraction force belonging to the eleventh domain TVB-11are mapped with one-to-one association to the post-limitation target values of the damping force and the extension/contraction force belonging to the eleventh value range TVA-11using the predetermined linear function F11. For example, the eleventh pre-limitation target value TVb11is mapped to the eleventh post-limitation target value TVa11.

The twelfth domain TVB-12is a domain relating to the pre-limitation target value of the damping force at the time of abnormality when the electric motor31is in the excessive heat generation state.

In the time of abnormality, the pre-limitation target value of the damping force belonging to the twelfth domain TVB-12is mapped through one-to-one association to the post-limitation target value of the damping force belonging to the twelfth value range TVA-12through the predetermined linear function F12.

The predetermined linear function F12is configured to have a gentler slope than the predetermined linear function F11. For example, the twelfth pre-limitation target value TVb12of the damping force is mapped to the twelfth post-limitation target value TVa12of the damping force, which TVa12is smaller than TVa11.

The thirteenth domain TVB-13is a domain relating to the pre-limitation target value of the extension/contraction force at the time of abnormality when the electric motor31is in the excessive heat generation state.

In the time of abnormality, the pre-limitation target value of the extension/contraction force belonging to the thirteenth domain TVB-13is mapped through one-to-one association to the post-limitation target value of the extension/contraction force belonging to the thirteenth value range TVA-13through the predetermined linear function F13.

The predetermined linear function F13is configured to have a gentler slope than the predetermined linear function F12. For example, the thirteenth pre-limitation target value TVb13of the extension/contraction force is mapped to the thirteenth post-limitation target value TVa13of the extension/contraction force, which TVa13is smaller than TVa12.

In short, the pre/post-limitation target value map63according to the modification differs from the pre/post-limitation target value map61in that slopes of the linear functions used to map the pre-limitation target value to the post-limitation target value are gentler (F11>F12>F13) as an operation mode of the electric motor31shifts from the damping and extension/contraction control in the normal time, through the damping control at the time of abnormality, and to the extension/contraction control at the time of abnormality in a region of the domain TVB of the pre-limitation target value in which pre-limitation target values at the respective operation modes are smaller than the respective pre-limitation target values TVb11, TVb12, and TVb13.

Note that, the pre/post-limitation target value map63according to the modification has the domains occupying a larger pre-limitation target value respectively than the eleventh domain TVB-11, the twelfth domain TVB-12, and the thirteenth domain TVB-13are mapped to respective fixed values (the eleventh post-limitation target value TVa11, the twelfth post-limitation target value TVa12, and the thirteenth post-limitation target value TVa13), to suppress an endless increase in the damping force and the extension/contraction force by setting the post-limitation target value to a fixed levelled value. This configuration is the same as the pre/post-limitation target value map61according to the embodiment.

Note that, the pre/post-limitation target value map63according to the modification may be configured to have domain portions having the larger pre-limitation target value respectively than the eleventh domain TVB-11, the twelfth domain TVB-12, and the thirteenth domain TVB-13mapped to a common fixed value (for example, the eleventh post-limitation target value TVa11) as the post-limitation target value, so that the post-limitation target values are levelled off irrespective of increases of the pre-limitation target values in the respective domains in order to suppress endless increases of the damping force and the extension/contraction force.

Note that the pre/post-limitation target value map63according to the modification has the post-limitation target value of the extension/contraction force at the time of abnormality (the extension/contraction current limitation threshold, i.e., the thirteenth post-limitation target value TVa13) set to a value smaller than the post-limitation target value of the damping force at the time of abnormality (the damping current limitation threshold, i.e., the twelfth post-limitation target value TVa12), similarly to the pre/post-limitation target value map61according to the embodiment.

<Operation of Electrically Powered Suspension System11According to Embodiment>

Next, description is given of an operation of the electrically powered suspension system11according to the embodiment of the present invention with reference toFIG. 6, which is a flowchart illustrating the operation of the electrically powered suspension system11according to the embodiment of the present invention.

In step S11: “Acquire stroke speed” shown inFIG. 6, the information acquisition part43of the ECU15receives a rotation angle signal of the electric motor31detected by the resolver37as time-series information on a stroke position, and time-differentiates this time-series information to acquire information on a stroke speed SV. The information on the stroke speed SV acquired in this manner is sent to the driving force calculator47.

In step S12: “Acquire sprung speed”, the information acquisition part43of the ECU15acquires time-series information on sprung acceleration detected by the sprung acceleration sensor40and time-integrates the time-series information on the sprung acceleration to acquire information on a sprung speed BV. The information on the sprung speed BV acquired in this way is sent to the driving force calculator47.

In step S13: “Calculate target damping force and target extension/contraction force”, the target damping force setting part51provided in the driving force calculator47of the ECU15determines a value of a target damping force responsive to the stroke speed SV based on the information on the stroke speed SV acquired in step S11and a target damping force map51A (seeFIG. 4B) conceptually representing a relationship (target damping force characteristic) between the stroke speed SV and a target damping force that varies responding to variations of the stroke speed SV.

Further, the target extension/contraction force setting part53provided in the driving force calculator47of the ECU15determines a value of the target extension/contraction force responsive to the sprung speed BV based on the information on the sprung speed BV acquired in step S12and a target extension/contraction force map conceptually representing a relationship (target extension/contraction force characteristics) between the sprung speed BV and the target extension/contraction force that varies in response to the variations of the sprung speed BV.

In step S14, the state determination part55included in the driving force calculator47of the ECU15, first calculates a integrated motor current value Iint by time-integrating time-series information on the motor current; next, performs a state determination as to whether or not the integrated motor current value Iint exceeds the integrated current threshold Iint_th, that is, whether or not the electric motor31is in the excessive heat generation state, on a basis of the information on the calculated integrated motor current value Iint, and the like.

When the state determination in step S14results in a determination that the electric motor31is not in the excessive heat generation state (“No” in step S14), the ECU15makes the processing flow jump to step S161.

On the other hand, when the state determination in step S14results in a determination that the electric motor31is in the excessive heat generation state (“Yes” in step S14), the state determination part55included in the driving force calculator47of the ECU15sends a setting-permission signal indicating a permission of the setting according to setting information on a control mode respectively to the target damping force limitation part52and the target extension/contraction force limitation part54.

In step S15, the target damping force limiting part52included in the driving force calculator47of the ECU15calculates a value of the post-limitation target damping force on a basis of the value of the target damping force set in the step S13and the pre/post-limitation target value map61according to the embodiment.

Further, the target extension/contraction force limiting part54included in the driving force calculator47of the ECU15calculates a post-limitation target value of the extension/contraction force on a basis of the value of the target extension/contraction force determined in step S13and the pre/post-limitation target value map61according to the embodiment.

In step S16: “Calculate driving force”, if the state determination in step S14results in the determination that the electric motor31is in the excessive heat generation state, the adder57included in the driving force calculator47of the ECU15calculates a target driving force by adding the post-limitation target damping force calculated by the target damping force limitation part52and the target extension/contraction force calculated by the target extension/contraction force limitation part54both in the step S15; and calculates a driving control signal for achieving the target driving force.

However, when the state determination in step S14results in the determination that the electric motor31is not in the excessive heat generation state, the adder57included in the driving force calculator47of the ECU15acquires a target driving force by adding the target damping force calculated by the target damping force setting part51and the target extension/contraction force calculated by the target extension/contraction force limitation part53both in the step S13; and calculates a drive control signal for achieving the target driving force.

In step S17, the drive controller49of the ECU15supplies drive control power to the electric motor31provided in each of the plurality of electromagnetic actuators13in accordance with the drive control signal calculated in the step S16, so as to perform the drive control of the plurality of electromagnetic actuators13.

<Internal Configuration of Driving Force Calculator According to First Modification>

Next, description is given of an internal configuration of a driving force calculator47B according to first modification included in the ECU15of the electrically powered suspension system11with reference toFIG. 7A.

FIG. 7Ais a block diagram conceptually illustrating the internal configuration of the driving force calculator47B according to a first modification included in the ECU15of the electrically powered suspension system11.

The driving force calculator47A of the embodiment illustrated inFIG. 4Aand the driving force calculator47B according to the first modification illustrated inFIG. 7Ahave many components common to both.

Accordingly, description is given, which is focused mainly on differences between the driving force calculator47A of the embodiment and the driving force calculator47B according to the first modification by focusing on them, which description substitutes for an explanation on the driving force calculator47B according to the first modification.

The driving force calculator47B according to the first modification differs from the driving force calculator47A of the embodiment in that the driving force calculator47B determines whether or not the electric motor31is in the excessive heat generation state on a basis of information such as ECU temperature Te, instead of the information of the integrated motor current value Iint (used in the embodiment) acquired by time-integrating the time-series information on the motor current.

The state determination part55included in the driving force calculator47B according to the first modification acquires the information on the ECU temperature Te through the information acquisition part43. The information on the ECU temperature Te, which varies every moment in response to a load state (drive current) of the electric motor31, may be acquired at a predetermined cycle and used as appropriate.

Further, the state determination part55performs a state determination of whether or not the ECU temperature value Te exceeds the ECU temperature threshold Te_th, that is, whether or not the electric motor31is in the excessive heat generation state.

If the state of the determination results in a determination that the ECU temperature Te exceeds the ECU temperature threshold Te_th, that is, the electric motor31is in the excessive heat generation, the state determination part55is sends a control current limiting command signal indicating to limit the control current for achieving the driving force relating to the damping force and the extension/contraction force, respectively to the target damping force limiting part52and the target extension/contraction force limiting part54.

The subsequent operation is the same as that of the driving force calculator47A of the embodiment.

<Internal Configuration of Driving Force Calculator of Second Modification>

Next, description is given of an internal configuration of a driving force calculator47C according to second modification provided in the ECU15of the electrically powered suspension system11with reference toFIG. 7B.

FIG. 7Bis a block diagram conceptually illustrating an internal configuration of the driving force calculator47C according to the second modification provided in the ECU15of the electrically powered suspension system11.

The driving force calculator47A of the embodiment illustrated inFIG. 4Aand the driving force calculator47C according to the second modification illustrated inFIG. 7Chave many components common to both.

Accordingly, a description is given, which is focused mainly on differences between the driving force calculator47A of the embodiment and the driving force calculator47C according to the second modification, and which description substitutes for an explanation on the driving force calculator47C according to the second modification.

The driving force calculator47C according to the second modification is different from the driving force calculator47A of the embodiment in that the driving force calculator47C performs a state determination of whether or not the electric motor31is in the excessive heat generation state on a basis of information such as a motor temperature Tm instead of the information of the integrated motor current value Iint (used in the embodiment) acquired by time-integrating the time-series information of the motor current.

The state determination part55included in the driving force calculator47C according to the second modification acquires the information on the motor temperature Tm via the information acquisition part43. The information on the motor temperature Tm, which varies every moment in response to a load state (drive current) of the electric motor31, may be acquired at a predetermined cycle and used as appropriate.

Further, the state determination part55performs a state determination of whether or not the motor temperature Tm exceeds the motor temperature threshold Tm_th, that is, whether or not the electric motor31is in the excessive heat generation state.

If the state of the determination results in a determination that the Motor temperature Tm exceeds the motor temperature threshold Tm_th, that is, the electric motor31is in the excessive heat generation, the state determination part55sends a control current limiting command signal indicating to limit the control current for achieving the driving force relating to the damping force and the extension/contraction force, respectively to the target damping force limiting part52and the target extension/contraction force limiting part54.

The subsequent operation is the same as that of the driving force calculator47A of the embodiment.

Next, description is given of features of the electrically powered suspension system11according to the embodiment (including an example, and modifications1and2) of the present invention.

The first feature is that the damping current limitation threshold and the extension/contraction current limitation threshold (when the electric motor31is in an excessive heat generation state) are configured individually in consideration of conditions such that they are different in priority on riding comfort and driving stability of the vehicle10and an energization time for the damping control and the extension/contraction control.

First, description is given of the priority regarding the riding comfort and the driving stability of the vehicle10.

The time of abnormality (when the electric motor31is in an excessive heat generation state) may be supposed to be, for example, a case in which requests frequently occur to generate the damping force and the extension/contraction force relating to the electrically powered suspension system11when the vehicle10is traveling on a rough unpaved road.

In the case described above, when the vehicle10is traveling on the rough unpaved road, it is a principle to give priority to the driving stability of the vehicle10more than the riding comfort thereof, because there is a higher demand for stabilizing a behavior of the vehicle10as compared with a case in which the vehicle10is traveling on a maintained and paved road. This means that the damping control mainly relating to a steering stability is performed with priority over the extension/contraction control mainly relating to the riding comfort of the vehicle10.

Next, description is given of a situation in which a difference occurs in the energization time for the damping control and the extension/contraction control.

Generally, a frequency of a vibration wave to be controlled by the damping control is prone to be higher than a frequency of a vibration wave to be controlled by the extension/contraction control. This results in a tendency in which an energization time for the damping control that is an energization time required for the damping control of the vibration wave in a predetermined unit cycle period is shorter than an energization time for the extension/contraction control of the vibration wave in a predetermined unit cycle (vibration wave to be controlled by damping control is subsided in a shorter time than vibration wave to be controlled by extension/contraction control).

Conversely, the frequency of the vibration wave to be controlled by the extension/contraction control tends to be lower than the frequency of the vibration wave to be controlled by the damping control. This results in a tendency in which the energization time for the extension/contraction control of the vibration wave in the predetermined unit cycle is longer than the energization time for the damping control that is the energization time required for the damping control of the vibration wave in the predetermined unit cycle period (vibration wave to be controlled by extension/contraction control needs a longer time than vibration wave to be controlled by damping control).

As described above, the energization time for the damping control of the vibration wave per unit cycle tends to be shorter (settled in a shorter time) than the energization time for the extension/contraction control of the vibration wave per unit cycle. That is, there is a substantial difference in the energization time for the damping control and the extension/contraction control of the vibration wave per unit cycle.

This means that a reasonable design is to assign different length of times respectively to the energization time for the damping control and the energization time for the extension/contraction control in the time of abnormality in which the electric motor31generates excessive heat, when considering the current limitation timing (operation limitation timing) for the damping control and the extension/contraction control.

Therefore, the electrically powered suspension system11according to the embodiment of the present invention is configured to have a configuration in which settings are separately assigned to the damping current limitation threshold and the extension/contraction current limitation threshold, considering the priority on the riding comfort and steering stability of the vehicle10, and a condition such as the substantial difference in the energization times for performing the damping control and the extension/contraction control.

Here, the damping current limitation threshold is a current limitation threshold that is a guide value for limiting the drive current (damping control current) of the electric motor31when performing the damping control at the time of abnormality. The damping current limitation threshold corresponds to the second post-limitation target value TVa2.

In addition, the extension/contraction current limitation threshold is a current limitation threshold that is a guide value for limiting the drive current (extension/contraction control current) of the electric motor31when performing the extension/contraction control at the time of abnormality. The extension/contraction current limitation threshold corresponds to the third post-limitation target value TVa3.

As shown inFIG. 5A, the second feature is that the extension/contraction current limitation threshold (third post-limitation target value TVa3) is set to a value smaller than the damping current limitation threshold (second post-limitation target value TVa2), that is, TVa3<TVa2.

As described above, the energization time for the extension/contraction control of the vibration wave per unit cycle tends to be longer than the energization time for the damping control of the vibration wave per unit cycle, which means that an amount of work (heat quantity) for the extension/contraction control of the vibration wave per unit cycle tends to be larger than an amount of work (heat quantity) for the damping control of the vibration wave per unit cycle.

This second feature allows to give priority to performing the current limitation of the extension/contraction control that involves the riding comfort of the vehicle10and tends to generate a larger amount of heat than the damping control, over the current limitation of the damping control, and at the same time, and to make the current limitation of the damping control (involving suppression of the unsprung vibration) difficult to start and thereby to achieve the vibration control of the vehicle10without disturbing a behavior of the vehicle10and without impairing the riding comfort of the vehicle10as much as possible even if the electric motor31provided in the electromagnetic actuator13is in an excessive heat generation state.

The electrically powered suspension system11according to the first aspect includes the electromagnetic actuator13including the electric motor31generating the driving force relating to the vibration damping and the extension/contraction; a driving force calculator (target current calculator)47calculating respectively a target damping current for generating a target driving force relating to the vibration damping and a target extension/contraction current for generating a target driving force relating to the extension/contraction; and a drive controller49performing the drive control of the electric motor using a drive current based on the target damping current and the target extension/contraction current.

The drive controller49performs the drive control of the electric motor31using the drive current of the electric motor31limited not to exceed a preconfigured current limitation threshold.

The current limitation threshold includes an damping current limitation threshold for the target damping current (second post-limitation target value TVa2) and the extension/contraction current limitation threshold for the target extension/contraction current (third post-limitation target value TVa3).

The damping current limitation threshold (second post-limitation target value TVa2) and the extension/contraction current limitation threshold (third post-limitation target value TVa3) are individually configured.

In the electrically powered suspension system11according to the first aspect, the drive controller49controls the electric motor31using the drive current limited so that the drive current of the electric motor31does not exceed a preset current limitation threshold. Drive control is performed.

In the embodiment of the present invention, properties for the drive current of the electric motor31corresponds respectively to the integrated motor current value Iint in the embodiment, the ECU temperature value Te in the first modification, and a motor temperature value Tm in the second modification.

In the above correspondence, properties for the current limitation threshold pre-configured to limit the drive current of the electric motor31corresponds respectively to the integrated current threshold Iint_th in the embodiment, the ECU temperature threshold Te_th in the first modification, the motor temperature threshold Tm_th in the second modification.

In other words, the electrically powered suspension system11according to the first aspect determines that the electric motor31is in an excessive heat generation state when the drive current of the electric motor31(integrated motor current value Iint in the embodiment, ECU temperature value Te in the first modification, motor temperature value Tm in the second modification) exceeds the preset current limitation threshold (integrated current threshold Iint_th in the embodiment, ECU threshold temperature Te_th in the first modification, motor temperature threshold Tm_th in the second modification).

The current limitation threshold includes the damping current limitation threshold for the target damping current (second post-limitation target value TVa2) and the extension/contraction current limitation threshold for the target extension/contraction current (third post-limitation target value TVa3). This configuration is based on a fact that the damping control and the extension/contraction control are simultaneously performed using the drive current acquired by adding the target damping current and the target extension/contraction current.

The damping current limitation threshold (second post-limitation target value TVa2) and the extension/contraction current limitation threshold (third post-limitation target value TVa3) are individually determined, for example, according to the priority on the riding comfort and steering stability of the vehicle10. This means, for example, that the damping control involving mainly the steering stability is performed with priority over the extension/contraction control mainly involving the riding comfort of the vehicle10.

The electrically powered suspension system11according to the first aspect performs the damping control mainly involving the steering stability with priority over the extension/contraction control mainly involving the riding comfort of the vehicle10when determining that the electric motor31is in the excessive heat generation state, and therefore is able to achieve the accurate vibration control of the vehicle10without disturbing the behavior of the vehicle10and without impairing the riding comfort of the vehicle10as much as possible even when the electric motor31provided in the electromagnetic actuator13is in the excessive heat generation state.

Further, the electrically powered suspension system11according to the second aspect is the electrically powered suspension system11according to the first aspect, wherein the extension/contraction current limitation threshold (the third post-limitation target value TVa3) is set to a value smaller than a damping current limitation threshold (the second post-limitation target value TVa2).

As described above, the energization time for the extension/contraction control of the vibration wave per unit cycle tends to be longer than the energization time for the damping control of the vibration wave per unit cycle. In other words, the amount of work (heat quantity) for the extension/contraction control of the vibration wave per unit cycle tends to be larger than the amount of work (heat quantity) for the damping control of the vibration wave per unit cycle.

The electrically powered suspension system11according to the second aspect is able to give priority to performing the current limitation of the extension/contraction control that involves the riding comfort of the vehicle10and tends to generate a larger amount of heat than the damping control over the current limitation of the damping control, and at the same time, to make the current limitation of the damping control (involving suppression of the unsprung vibration) difficult to start and thereby can achieve the accurate vibration control of the vehicle10without disturbing a behavior of the vehicle10and without impairing the riding comfort of the vehicle10as much as possible even if the electric motor31provided in the electromagnetic actuator13is in the excessive heat generation state.

The electrically powered suspension system11according to the third aspect is the electrically powered suspension system11according to the first or second aspects, wherein the damping current limitation threshold (the second post-limitation target value TVa2) and the extension/contraction current limitation threshold (the third post-limitation target values TVa3) each is set on a basis of the current correlation value correlating with the drive current of the electric motor31.

Here, the current correlation value correlated with the drive current of the electric motor31is a property that naturally includes the drive current itself of the electric motor31, and further comprehensively includes current correlation values that can give an accurate estimate about the heat generation state of the electric motor31, such as a current correlation value of the electric motor31converted from a temperature around a substrate of the ECU15that performs the drive control of the electromagnetic actuator13; and a current correlation value of the electric motor31converted from a temperature around a housing of the electric motor31.

The electrically powered suspension system11according to the third aspect may configure each of the damping current limitation threshold and the extension/contraction current limitation threshold on a basis of the current correlation values correlating with the driving current of the electric motor31, and therefore allows to clarify a configuration guideline of the damping current limitation threshold and the extension/contraction current limitation threshold to facilitate implementation of the present invention.

Further, an electrically powered suspension system11according to the fourth aspect is the electrically powered suspension system11including any one of the first to third aspects, and further includes an information acquisition part43that acquires information on a temperature Te of the ECU (drive control unit)15, wherein each of the damping current limitation threshold (the second post-limitation target value TVa2) and the extension/contraction current limitation threshold (the third post-limitation target value TVa3) is set on a basis of the temperature Te of the ECU15.

The electrically powered suspension system11according to the fourth aspect may configure each of the damping current limitation threshold and the extension/contraction current limitation threshold on a basis of the temperature Te of the ECU15, and therefore allows to make a clearer configuration guideline of the damping current limitation threshold and the extension/contraction current limitation threshold to facilitate implementation of the present invention more than the electrically powered suspension system11according to the third aspect.

Further, the electrically powered suspension system11according to the fifth aspect is the electrically powered suspension system11according to any one of the first to third aspects, and further including an information acquisition part43that acquires information on the temperature Tm of the electric motor31, wherein each of the damping current limitation threshold (the second post-limitation target value TVa2) and the extension/contraction current limitation threshold (the third post-limitation target value TVa3) is configured on a basis of the temperature Tm of the electric motor31.

The electrically powered suspension system11according to the fifth aspect may configure each of the damping current limitation threshold and the extension/contraction current limitation threshold on a basis of the temperature Tm of the electric motor31, and therefore allows to make a clearer configuration guideline of the damping current limitation threshold and the extension/contraction current limitation threshold to facilitate implementation of the present invention more than the electrically powered suspension system11according to the third aspect.

Further, the electrically powered suspension system11according to the sixth aspect is the electrically powered suspension system11including any of the first to third aspects, wherein the damping current limitation threshold (the second post-limitation target value TVa2) and the extension/contraction current limitation threshold (the third post-limitation target value TVa3) are independently configured in consideration of at least the priority on the riding comfort and the driving stability of the vehicle10.

This means that the damping control mainly relating to the steering stability is performed with priority over the extension/contraction control mainly relating to the riding comfort of the vehicle10.

The electrically powered suspension system11according to the sixth aspect performs the damping control mainly involving the steering stability with priority over the extension/contraction control mainly involving the riding comfort of the vehicle10when determining that the electric motor31is in the excessive heat generation state, and therefore is able to achieve the accurate vibration control of the vehicle10without disturbing the behavior of the vehicle10and without impairing the riding comfort of the vehicle10as much as possible even when the electric motor31provided in the electromagnetic actuator13is in the excessive heat generation state, similarly to the electrically powered suspension system11according to the first aspect.

OTHER EMBODIMENTS

The embodiment and the plurality of modifications described above show examples for implementations of the present invention. Therefore, the technical scope of the present invention should not be construed to be limited to these embodiment and modifications. The present invention can be implemented in various embodiments without departing from the gist or the main scope of the present invention.

In addition, the description is given of the embodiment of the extension/contraction control of the electromagnetic actuator13in the electrically powered suspension system11according to the embodiment of the present invention, by exemplifying the control performed using the skyhook control that suppresses the vertical vibration of the vehicle body on the basis of the sprung speed BV, but the present invention is not limited to this embodiment.

The present invention may be applied, for example, on a control for suppressing roll vibration of the vehicle body based on the roll angular velocity of the vehicle body and a control for suppressing pitch vibration of the vehicle body based on the pitch angular velocity of the vehicle body, as another embodiment of the extension/contraction control of the electromagnetic actuator13.

Further, the electrically powered suspension system11according to the embodiment is described in the embodiment that arranges the total of four electromagnetic actuators13on both the front wheels (front right wheel and front left wheel) and the rear wheels (rear right wheel and rear left wheel). However, the present invention is not limited to this specific embodiment. For example, the total of two electromagnetic actuators13may be arranged in either one of the front wheels and the rear wheels.

Finally, the electrically powered suspension system11according to the embodiment is described such that the drive controller49performs independent drive control of each of the plurality of electromagnetic actuators13. To be more specific, the drive controller49may perform independent drive control of each of the electromagnetic actuators13respectively provided in the four wheels for each of the wheels. Further, the drive controller49may performs independent drive control of the electromagnetic actuators13respectively provided for the four wheels, separately for the front wheels and for the rear wheels, or separately for the right wheels and the left wheels.