Control device for an electric suspension

Abstract

Control device for an electric suspension (27, 41, 51) arranged between a body (1) and a wheel (2, 3) of a vehicle and designed to adjust a thrust force of an electric actuator (6, 9) according to a thrust force instruction value output by a control unit, wherein at least one motion detection unit (18, 19, 20, 21, 22, 23, 24) is connected to the control unit, and the motion detection unit (18, 19, 20, 21, 22, 23, 24) is configured to detect a motion state of the vehicle, the control unit features: a calculation unit for calculating a required thrust force (28), which is designed to calculate a required thrust force instruction value from a detection value that has been detected with the motion detection unit (18, 19, 20, 21, 22, 23, 24), a frequency band determination unit (29, 30, 42, 54) which is designed to distribute the calculated value of the calculation unit for calculating a required thrust force (28) to a plurality of frequency bands, a limiter (31, 32, 43, 53) provided for each of the frequency bands to which the calculated value is distributed by the frequency band determination unit (29, 30, 42, 54), and a thrust instruction value calculation unit (33, 44, 45, 46, 54) configured to generate the thrust instruction value by combining an output value of the limiter (31, 32, 43, 53) for each frequency band, and wherein a limit value of the limiter (31, 32, 43, 53) is set in such a way that one value (Flmax) in a low frequency band, as one of the frequency bands, is smaller than a value (Fhmax) in a high frequency band, as another of the frequency bands.

Description

Background of the invention: Technical field

[0001] The present invention relates to a control device for an electric suspension, which is preferably used to absorb vibration of a vehicle such as an automobile or a rail vehicle. State of the art

[0002] In general, a suspension device is arranged between a vehicle body and a wheel in a vehicle such as an automobile. An electrical suspension device is known as such, which uses an electric actuator with a stator and a movable element, supported in such a way that they are linearly movable relative to each other (see JP 2010-279121 A).

[0003] This type of electric suspension device, according to current techniques, is designed to adjust the thrust force of the electric actuator according to a thrust force instruction value (a control signal) output by a controller (a control device). Further prior art is described in US 2009 / 0 224 502 A1, US 2011 / 0 025 000 A1, DE 60 2004 006 031 T2 and JP 2004-299 559 A. Summary of the invention

[0004] The electric suspension device should be designed to be small in size while maintaining the thrust of the electric actuator. On the other hand, there is a problem whereby increasing the current supplied to the electric actuator to ensure the thrust leads to an increase in its heating value.

[0005] The present invention was undertaken taking into account the problem described above in common techniques, and one object of the present invention is to provide a control device for an electrical suspension which is suitable for reducing the heating value of an electric actuator.

[0006] To solve the problem described above, the present invention provides a control device for an electric suspension arranged between a vehicle body and a wheel, configured to adjust the thrust force of an electric actuator according to a thrust force instruction value output by a control unit. At least one motion detection unit is connected to the control unit. The motion detection unit is configured to detect the vehicle's state of motion.The control unit includes a calculation unit for calculating a required thrust force, which is configured to calculate a required thrust force value from a detection value acquired by the motion detection unit; a frequency band determination unit, which is configured to output the calculated value of the calculation unit for calculating a required thrust force to a plurality of frequency bands; a limiter, which is provided for each of the frequency bands to which the calculated value is distributed by the frequency band determination unit; and a thrust instruction value calculation unit, which is configured to generate the thrust instruction value by combining an output value through the limiter for each frequency band.A limit value of the limiter is set in such a way that one value in a low-frequency band - one of the frequency bands - is smaller than a value in a high-frequency band - another frequency band.

[0007] According to the present invention, it is possible to reduce the heating value of the electric actuator. Brief description of the drawings Fig. Figure 1 is a perspective view showing a four-wheeled automobile on which a control device for an electric suspension according to a first embodiment of the present invention is applied; Fig. Figure 2 is a control block diagram showing the control device for an electric suspension according to the first embodiment; Fig. Figure 3 is a vertical cross-sectional view showing an electric actuator; Fig. 4 is an enlarged cross-sectional view, taken from a through in Fig. 3 arrows shown IV-IV indicate the direction; Fig. Figure 5 is a control block diagram showing a control device for an electric suspension according to a second embodiment; and Fig. Figure 6 is a control block diagram showing a control device for an electrical suspension according to a third embodiment. Detailed description of the preferred embodiment

[0008] The following description, with reference to the accompanying drawings, details a control device for an electric suspension according to embodiments of the present invention, based on an example in which the control device for an electric suspension is applied to an automobile, for example, a four-wheeled vehicle. The control device for an electric suspension according to the present invention can be used not only for automobiles, but also for rail vehicles, instead of a damper such as a yaw damper or a lateral dynamic damper.

[0009] Fig. Figures 1-4 show a first embodiment of the present invention. With reference to Fig. 1 are, for example, left and right front wheels 2 (only one of them is shown) and left and right rear wheels 3 (only one of them is shown) arranged under a vehicle body 1, which forms a body of the vehicle.

[0010] Electric suspension devices for a front wheel 4 (hereinafter referred to as "the suspension devices 4") are arranged between the vehicle body 1 and the left and right front wheels 2. Each suspension device 4 has a left or right suspension spring 5 (hereinafter referred to as "the spring 5") and a left or right electric actuator 6, which is arranged between the vehicle body 1 and the left or right front wheel 2, parallel to the spring 5.

[0011] Electric suspension devices for a rear wheel 7 (hereinafter referred to as "the suspension devices 7") are arranged between the vehicle body 1 and the left and right rear wheels 3. Each suspension device 7 has a left or right suspension spring 8 (hereinafter referred to as "the spring 8") and a left or right electric actuator 9, which is arranged between the vehicle body 1 and the left or right rear wheel 3, parallel to the spring 8.

[0012] Each suspension device 4, 7 is designed to adjust a thrust force of the electric actuator 6, 9 according to a thrust force instruction value issued by a controller 27, which will be described below.

[0013] Next, the electric actuator 6, 9, which forms each suspension device 4, 7, will be described. The present description is based on an example in which the electric actuator 6, 9 is formed by a linear motor. However, the present invention is not limited to this. The electric actuator can, for example, be formed by a rotary motor and a ball screw mechanism.

[0014] As in Fig. 3 and Fig. As shown in Figure 4, the electric actuator 6, 9 is designed as a linear motor and has a stator 10 and a moving element 15. Furthermore, a three-phase linear synchronous motor is formed by the stator 10 (an armature 12 of the stator 10) and the moving element 15 (permanent magnets 17 of the moving element 15).

[0015] The stator 10, which is located on a spring-loaded element (the vehicle body side) of the vehicle, generally comprises a housing 11 and the armature 12. The housing 11, for example, has a cylindrical shape with a base and includes a cylindrical section 11A extending in an axial direction (a vertical direction in Fig. 3) extends corresponding to a lifting direction and has a bottom section 11B which forms an end face (an upper end face in Fig. 3) of the cylinder section 11A is covered. The armature 12 is located at one end of the opening (a lower end in Fig. 2) of cylinder section 11A.

[0016] The armature 12 has a substantially cylindrical core 13, which is formed, for example, from a powder magnet core, a laminated electrical steel sheet, or a magnetic body piece, for example by cutting, and a plurality of coils 14A, 14B and 14C which are wound in a predetermined direction and contained in the core 13.

[0017] Each of the coils 14A, 14B, and 14C is arranged such that it faces an outer circumferential surface of the moving element (the permanent magnets 17 of the moving element 15), which will be described below. The coils 14A, 14B, and 14C are arranged, for example, in a circumferential direction of the core 13 at positions on an inner circumferential surface of the substantially cylindrical core 13, as shown in Fig. 4 shown, and are arranged at three positions in the axial direction of the substantially cylindrical core 13 in a spatially spaced relationship in the axial direction, as shown in Fig. Figure 3 shows that the number of coils 14A, 14B and 14C is not limited to that shown and can be determined in a suitable manner, for example according to a design description.

[0018] The three coils 14A, 14B, and 14C are arranged such that they have a phase difference relative to the adjacent coil in the axial direction, for example, an electrical angle of 120°. The connection method can be selected appropriately according to the voltage of a drive power source and the current specification.

[0019] The movable element 15, which is arranged on an unsprung element (the wheel side) of the vehicle, extends axially within the stator 10 and is mounted such that it is displaceable in the stroke direction (on the axial direction) within the stator 10, for example via a bearing (not shown). The movable element 15 generally comprises a yoke 16 and a plurality of permanent magnets 17.

[0020] The yoke 16, for example, is made of a magnetic body and has a cylindrical shape with a base. The yoke 16 has a cylindrical section 16A extending in the axial direction corresponding to the stroke direction and a base section 16B forming the other end (the lower end). Fig. 3) of the cylindrical section 16A is covered.

[0021] The multitude of ring-shaped permanent magnets 17, which function as a field system, are arranged such that they are aligned along the axial direction of an outer circumferential surface of the cylindrical section 16a of the yoke 16. In this case, the permanent magnets 17 arranged adjacent to each other in the axial direction, for example, have opposite polarities to each other. In the example shown, the field system is formed by the permanent magnets 17, but it can also be formed by coils.

[0022] When a relative displacement occurs between the stator 10 (the armature 12 of the stator 10) and the moving element 15 (the permanent magnet 17 of the moving element 15), an induced voltage arises corresponding to a change in the magnetic flux coupling the coils 14A, 14B, and 14C. In the event of a short circuit between the coils 14A, 14B, and 14C, a short-circuit current flows to generate a resistive force. This resistive force exhibits a linear range, where it increases with speed; a saturation range, where the increase in resistive force with speed becomes approximately zero or less than that in the linear range; or a decay range, where the resistive force decreases with speed and can be modified according to the design of the electrical actuator 6, 9 (the suspension device 4, 7).

[0023] If a required thrust force (a required control force) is less than a resistance force generated by short-circuiting the electrical actuator 6, 9, energy corresponding to the difference is reused by a power source 25, as will be described below. On the other hand, if it is necessary to provide a greater resistance force than that generated by the electrical actuator 6, 9, or if it is necessary to provide an auxiliary force (a thrust force opposite to the resistance force), a greater voltage than the induced voltage generated by the electrical actuator 6, 9 is supplied by the power source 25, thereby achieving the required thrust force (the required control force).In both cases, the suspension device 4, 7 is designed in such a way that a thrust force of the electric actuator 6, 9 is set according to a thrust force instruction value issued by the controller 27, which will be described below.

[0024] Next, with reference to Fig. Two different types of sensors 18-24, which are connected to the controller 27, are described.

[0025] A plurality of vertical acceleration sensors 18, attached to the vehicle body 1 and corresponding to a motion detection unit, detect a vertical vibration acceleration (a vertical acceleration) on the vehicle body 11, corresponding to the sprung side. In other words, each of the vertical acceleration sensors 18 detects a vertical motion state of the vehicle, as an acceleration of a vertical vibration when the vehicle is moving, and outputs a detection signal based on this to the controller 27, as will be described below. The vertical acceleration sensors 18 can, for example, be arranged at positions corresponding to the four wheels. Alternatively, as in the example shown, three vertical acceleration sensors 18 can all be arranged on the respective left and right front wheels 2 and any one of the left and right rear wheels 3.Alternatively, only one vertical acceleration sensor 18 can be arranged on the vehicle body 1, and a vertical acceleration can be estimated from values ​​of a lateral acceleration sensor 19 and a longitudinal acceleration sensor 20, which will be described below.

[0026] The lateral acceleration sensor (left-right acceleration sensor) 19, which is mounted on the vehicle body 1 and corresponds to the motion detection unit, detects an acceleration in a lateral direction of the vehicle (a left-right acceleration). More precisely, the lateral acceleration sensor 19 detects a state of motion of the vehicle in the lateral direction, as an acceleration of a lateral vibration when the vehicle is moving, and outputs a detection signal based on this to the controller 27, which will be described below.

[0027] A longitudinal acceleration sensor 20, mounted on the vehicle body 1 and corresponding to the motion detection unit, is, for example, located close to the lateral acceleration sensor 19 and detects acceleration in a longitudinal direction of the vehicle (a front-to-rear acceleration). More precisely, the longitudinal acceleration sensor 20 detects a state of motion of the vehicle in the longitudinal direction as an acceleration of a longitudinal vibration when the vehicle is moving and outputs a detection signal based on this to the controller 27, which will be described below.

[0028] A steering angle sensor 21, which is attached to the vehicle body 1 and corresponds to the motion detection unit, is formed, for example, by an angle sensor arranged on a steering wheel (not shown) and detects a steering angle of the steering wheel operated by the driver. More precisely, the steering angle sensor 21 detects a motion state of the vehicle as the steering angle of the steering wheel when the vehicle is moving and outputs a detection signal based on this to the controller 27, which will be described below.

[0029] A vehicle speed sensor 22, which is attached to the vehicle body 1 and corresponds to the motion detection unit, detects, for example, the vehicle's driving speed (a vehicle speed). More precisely, the vehicle speed sensor 22 detects a state of motion of the vehicle as a vehicle speed when the vehicle is moving and outputs a detection signal based on this to the controller 27, which will be described below.

[0030] A stroke sensor 23, which is attached to a suspension device 4, 7 and corresponds to the motion detection unit, detects, for example, a stroke (an extension or compression amount) of each suspension device 4, 7 (of the electric actuator 6, 9). More precisely, when the vehicle is moving, the stroke sensor 23 detects a motion state of the vehicle as a stroke of each of the suspension devices 4, 7 and outputs a detection signal based thereon to the controller 27 and a converter 26, as will be described below.

[0031] A temperature sensor 24, which is attached to each suspension device 4, 7 and corresponds to the motion detection unit, detects, for example, a temperature of the electric actuator 6, 9 of each of the suspension devices 4, 7. More precisely, the temperature sensor 24 detects a motion state of the vehicle as a temperature of the electric actuator 6, 9 when the vehicle is moving and outputs a signal based thereon to the controller 27, which will be described below.

[0032] Next, the power source 25 and the converter 26 for driving the electrical actuator 6, 9 are described.

[0033] The power source 25 provides power to the inverter 26 for driving the electric actuator 6, 9. The power source 25 can be, for example, a battery attached to the vehicle. More precisely, if the vehicle is, for example, a vehicle that uses an engine (an internal combustion engine) as its drive source, the power source 25 can be implemented by, for example, using a configuration for receiving a power supply from a power source specifically provided for the electrical suspension device or an AC generator, and temporarily storing the received power, for example, in a capacitor for the electric actuator 6, 9.

[0034] Alternatively, if the vehicle is a hybrid or electric vehicle, it is possible to receive power from a high-voltage traction battery attached to the vehicle. In this case, if the electric actuator 6, 9 outputs a large thrust force (a control force), this leads to a large voltage drop in the traction battery, which can, for example, reduce the vehicle's acceleration or affect the peripheral devices. To avoid this, the vehicle can be designed such that a capacitor is arranged between the traction battery and the inverter 26. Furthermore, if necessary, energy stored by the electric actuator 6, 9 can be supplied to the traction battery by regeneration. In this case, it is possible to increase the vehicle's range.

[0035] The inverter 26, which is connected to the electrical actuator 6, 9, drives the electronic actuator 6, 9 of each suspension device 4, 7 based on a control signal (a thrust force instruction value) from the controller 27 and power supplied by the power source 25. The inverter 26 is formed using a variety of switching elements (not shown), such as a transistor, a thyristor, and an insulated-gate bipolar transistor (IGBT). To cause the electrical actuator 6, 9 to exert a force, power is supplied to the electrical actuator 6, 9 from the power source 25 via the inverter 26. At the time of regeneration, power is fed back from the electrical actuator 6, 9 to the power source 25 via the inverter 26.

[0036] Next, the controller 27, which sets a thrust force (a control force) of the electric actuator 6, 9, will be described.

[0037] As in Fig. As shown in Figure 2, the controller 27, acting as a control unit (e.g., a microcomputer), is connected to the input side of the microcomputer, for example, to vertical acceleration sensors 18, lateral acceleration sensors 19, longitudinal acceleration sensors 20, steering angle sensors 21, vehicle speed sensors 22, lift sensors 23, and temperature sensors 24. Furthermore, the controller 27 is connected to the electrical actuators 6, 9 via the inverter 26 at its output side.

[0038] The controller 27 calculates a control force required to regulate ride comfort and vehicle position, i.e., a resistance force or thrust force of the electric actuator 6, 9, according to a specific control law, such as the Sky Hook theory, from various types of state sets (vehicle information) indicating the vehicle's state of motion, such as vertical acceleration, lateral acceleration, longitudinal acceleration, vehicle speed, steering angle, stroke of the electric actuator 6, 9, and the temperature of the vehicle body. The controller is then configured to output a control signal (a thrust force instruction value) corresponding to the calculation result to the inverter 26, thus enabling the output of the required control force of the electric actuator 6, 9.

[0039] Furthermore, the controller 27 monitors each suspension device 4, 7 based on a set of states (suspension information) that specifies the state of each suspension device 4, 7, such as the stroke and temperature of the electric actuator 6, 9. More precisely, the controller 27 is designed in such a way that if the controller 27 detects an abnormality of the suspension device 4, 7, the controller 27 can take measures such as stopping the electric actuator 6, 9 or reducing the control force and, if necessary, issue a warning to the driver.

[0040] The suspension device 4, 7, which uses the electric actuator 6, 9, can directly generate a control force (a thrust force) between the sprung side (the vehicle body side) and the unsprung side (the wheel side). Therefore, the suspension devices 4 and 7 can, for example based on the Sky Hook theory, implement a suspension characteristic in a highly efficient manner, thereby improving the vehicle's ride comfort and steering stability.

[0041] On the other hand, the electric actuator 6, 9, which uses the permanent magnets 17, generates, for example, a thrust force proportional to a current and produces a heat input (a copper loss) proportional to the square of the current. In other words, outputting twice the control force corresponds to generating four times the heat input. Therefore, a continuous output of a large thrust force leads to a temperature increase, and continuing to use the electric actuator 6, 9 at a high temperature can lead to insulation deterioration of the coils 14A, 14B, and 14C and irreversible flux losses of the permanent magnets 17. It is therefore important to determine a maximum permissible temperature in order to strictly control the temperature of the electric actuator 6, 9, for example, to prevent irreversible flux losses of the permanent magnets 17.

[0042] For example, when the vehicle is moving on a rough road surface (a bad road), a large steering force is immediately required. However, few road surfaces require a consistently large steering force, and in most cases, the steering force has a value that frequently alternates between zero, positive, and negative. In other words, when the vehicle is moving on a rough road surface, the electric actuator 6, 9 alternately outputs an extension force (a pushing force towards the extension side) and a compression force (a pushing force towards the compression side) according to the input of a road surface, thereby reducing the effective steering force and consequently also reducing the heating value. Furthermore, the actuator expands and contracts.The electric actuator 6, 9 (which has a stroke) compresses when the vehicle moves on a rough road surface, causing the phase of a current to shift according to the stroke, resulting in uniform heat generation.

[0043] On the other hand, if, for example, the electric actuator 6, 9 continuously outputs a constant force, such as during a uniform rotation, a current is continuously supplied for the duration of the constant force output, causing the heating value of the coils 14A, 14B, and 14C to increase. Specifically in this situation, the electric actuator 6, 9 may have a small stroke, and the current may be supplied unevenly, with only a specific phase, which locally increases the temperature (generating a lot of heat locally). This can, for example, lead to irreversible flux losses of the permanent magnets 17 and loosening and insulation deterioration of the coils 14A, 14B, and 14C.

[0044] On the other hand, one possible configuration involves controlling the electronic suspension device, while the control is divided into vehicle body position control to reduce roll and pitch movements, and vibration control to dampen vibrations. According to this configuration, it can be assumed that it is possible to reduce the amount of current supplied to the electric actuator by limiting the vehicle body position control, as required to correspondingly reduce temperature increases.

[0045] However, if a sudden steering input such as a slalom or a double lane change occurs after this design, limiting the vehicle's body steering control may make it difficult to adequately ensure steering stability. In other words, limiting the vehicle's body steering control may make it difficult to respond to high-frequency steering inputs.

[0046] Furthermore, in such a situation, where the electric actuator 6, 9 continues to output a constant force, e.g., during a constant rotation, when a road surface condition changes, the attitude control component is limited to ensuring a vibration control component, which can alter the movement of the vehicle body. In other words, an attitude control force can change under the influence of the vibration control component, and a roll angle can be affected, for example, in such a condition where the electric actuator 6, 9 continues to output a constant force, e.g., during a constant rotation, such as when an influence occurs due to a protrusion in a road surface.As a result, the roll angle can change depending on the road surface, for example, even during movement in the same constant rotation, which causes discomfort for the driver.

[0047] To solve these problems, the present embodiment is designed to control the electric actuator 6, 9, thus ensuring driving comfort and steering stability while reducing the heating value of the electric actuator 6, 9. As shown in Fig. As shown in Figure 2, the controller 27 therefore has, for example, a calculation unit for calculating a required thrust force 28, a low-frequency filter 29, a high-frequency filter 30, a low-frequency limiter 31, a high-frequency limiter 32, and an addition unit 33.

[0048] The calculation unit for determining the required thrust 28 of the controller 27 is an essential component of the present invention. This calculation unit calculates the required thrust 28 from measured values ​​acquired by the respective sensors 18-24. More precisely, the calculation unit calculates a required thrust value that corresponds to a thrust value that the electric actuator 6, 9 should output according to a specific control law, such as the Sky Hook theory, based on the measured values ​​(at least one of the measured values) from the respective sensors 18-24, which represent information about the vehicle. The specific control law can be any type of control, such as H-infinity control.

[0049] The required thrust value, calculated using the calculation unit for calculating a required thrust 28, corresponds to an ideal control force based on a control logic such as the Sky Hook theory and should be calculated taking heat generation and energy consumption into account. Therefore, the present invention is designed such that a required thrust, corresponding to a value calculated using the calculation unit for calculating a required thrust 28, is distributed across a plurality of frequency bands and is subject to an amplitude limit for each frequency band. Then, a combination (or addition) of the resulting values ​​is output to the inverter 26 as a thrust instruction value.

[0050] More precisely, a required thrust value, calculated by the thrust calculation unit 28, is distributed across a low-frequency band corresponding to a low-frequency movement, such as when the vehicle performs a constant rotation, and a high-frequency band corresponding to a high-frequency movement, such as when the vehicle performs a slalom or a double lane change. Therefore, the present invention is designed such that a required thrust value, calculated by the thrust calculation unit 28, is output in two directions at the output side of the thrust calculation unit 28 and is input to a low-frequency filter (a low-pass filter) 29 and a high-frequency filter (a high-pass filter) 30, which are arranged at the respective distribution destinations.

[0051] The low-frequency filter 29 and the high-frequency filter 30 form a frequency band determination unit, which is an essential component of the present invention. The controller 27 is configured to distribute a required thrust value, calculated with the required thrust value calculation unit 28, by transmitting the required thrust through the low-frequency filter 29 to the low-frequency band and by transmitting the required thrust through the high-frequency filter 30 to the high-frequency band. Limiters 31 and 32 are provided at the output sides of the low-frequency filter 29 and the high-frequency filter 30 of each frequency band.

[0052] More precisely, the low-frequency limiter 31, which limits an amplitude in the low-frequency band, is provided on the output side of the low-frequency filter 29. The high-frequency limiter 32, which limits an amplitude in the high-frequency band, is provided on the output side of the high-frequency filter 30. An output value of the low-frequency limiter 31 and an output value of the high-frequency limiter 32 are added by the addition unit 33 and output to the inverter 26 as a thrust instruction value. The addition unit 33 corresponds to a thrust instruction value calculation unit, which is an essential component of the present invention. In other words, the addition unit 33 combines (adds) output values ​​of the limiters 31 and 32 for each frequency band to generate a thrust instruction value.

[0053] A limit value (an upper limit value) of the low-frequency limiter 31 is smaller than a limit value (an upper limit value) of the high-frequency limiter 32. More precisely, the limit values ​​are set to satisfy the following equation 1, assuming that the limit value of the low-frequency limiter 31, corresponding to a limit value in the low-frequency band, is Flmax, and the limit value of the high-frequency limiter 32, corresponding to a limit value in the high-frequency band, is Fhmax. Flmax ≤ Fhmax (or Flmax) <Fhmax)

[0054] In this case, since the limit value Fhmax is large in the high-frequency band, the electric actuator 6, 9 can generate a large control force for a high-frequency movement resulting from a sudden steering input or an impulse response such as a slalom or a double lane change. As a result, it is possible to ensure driving comfort and steering stability.

[0055] On the other hand, since the limit value Flmax is small in the low-frequency band, the control force of the electric actuator 6, 9 for a low-frequency movement, such as performing a constant rotation, can be reduced. As a result, it is possible to prevent the electric actuator 6, 9 from constantly outputting a large thrust force, thereby reducing heat generation by the electric actuator 6, 9.

[0056] Additionally, if a high-frequency influence occurs, for example, due to a protrusion of a road surface, the electric actuator 6, 9 can, in such a state in which the electric actuator 6, 9 continuously outputs a constant force, as when performing a constant rotation, output a maximum control force F of the electric actuator 6, 9, from which the limit value Flmax of the low-frequency limiter 31 is subtracted, i.e., a control force corresponding to ΔF, as specified by the following equation 2, for a movement (a vibration) of the vehicle according to the protrusion. ΔF=F−Flmax

[0057] As a result, it is possible to implement steering in the opposite direction to the road surface's protrusion to ensure driving comfort. Furthermore, it is possible to maintain a constant roll angle using the low-frequency limiter 31 to prevent the driver from experiencing discomfort, regardless of any changes in the road surface (regardless of whether a high-frequency influence occurs, for example, due to a road surface protrusion).

[0058] Furthermore, the limit value Flmax of the low-frequency limiter 31 and the limit value Fhmax of the high-frequency limiter 32 are adjusted according to the temperature (heating value) of the electrical actuator 6, 9, which is detected by the temperature sensor 24. In a low-temperature condition, for example, the same value is set as the limit value Flmax of the low-frequency limiter 31 and the limit value Fhmax of the high-frequency limiter 32 (Flmax = Fhmax), thus enabling the electrical actuator 6, 9 to output the maximum control force F for both the high-frequency and the low-frequency bands.

[0059] On the other hand, if the temperature exceeds a predetermined first threshold, the limit value Flmax of the low-frequency limiter 31 is set lower than the limit value Fhmax of the high-frequency limiter 32 (Flmax < Fhmax), thus reducing heat generation resulting from a continuous output of a control force. Furthermore, both the limit value Flmax of the low-frequency limiter 31 and the limit value Fhmax of the high-frequency limiter 32 are reduced when the temperature of the electrical actuator 6, 9 approaches the temperature that leads to irreversible flux losses of the permanent magnets 17 and insulation degradation of the coils 14A, 14B, and 14C, for example, when the temperature exceeds a predetermined second threshold (the first threshold < the second threshold).As a result, it is possible to protect the electrical actuator 6, 9 against an increase in temperature without installing a new mechanism or the like.

[0060] Furthermore, the limit value Flmax of the low-frequency limiter 31 and the limit value Fhmax of the high-frequency limiter 32 are temporarily cleared, for example, when a vehicle stability control device such as ABS or ESC (an anti-skid device) is activated, for example, as a result of sudden braking. In other words, for example in the event of an emergency, the limit values ​​Flmax and Fhmax are temporarily cleared according to the vehicle's state of motion, thus ensuring vehicle stability in the event of an emergency.

[0061] The control device for an electric suspension according to the present embodiment is designed as described above. Its operation will also be described next.

[0062] For example, if the vehicle vibrates vertically due to a movement, a force in the lifting direction (the axial direction) is exerted on the suspension device 4, 7, which is located between the vehicle body 1 and the wheel (the front wheel 2 and the rear wheel 3) of the vehicle. This force generates a relative movement between the moving element 15 and the armature 12 of the electric actuator 6, 9. At this point, power is supplied to the coils 14A, 14B, and 14C, according to a control signal of a thrust force instruction value output by the controller 27. This allows the control force of the electric actuator 6, 9 to be adjusted to improve the vehicle's ride comfort and steering stability.

[0063] In this case, the calculation unit for determining a required thrust force 28 calculates a required thrust force value that corresponds to a lifting force that the electric actuator 6, 9 should output based on the measured values ​​of the respective sensors 18-24 according to a specific control law such as the Sky Hook theory. The required thrust force value, calculated by the calculation unit for determining a required thrust force 28, is fed to the low-frequency filter 29 and the high-frequency filter 30, and distributed to the low-frequency band by transmission through the low-frequency filter 29 and to the high-frequency band by transmission through the high-frequency filter 30.

[0064] After passing through the low-frequency filter 29, the output value of the low-frequency band is limited in amplitude by the low-frequency limiter 31. After passing through the high-frequency filter 30, the output value of the high-frequency band is limited in amplitude by the high-frequency limiter 32. The output values ​​of the low-frequency limiter 31 and the high-frequency limiter 32 are then added by the addition unit 33, and the added value is output as a thrust instruction value by the controller 27 to the inverter 26.

[0065] At this point, since the limit value Flmax of the low-frequency limiter 31 is smaller than the limit value Fhmax of the high-frequency limiter 32, it is possible to limit (reduce) the control force output by the electric actuator 6, 9 for a low-frequency movement, such as a constant rotation. Conversely, since the limit value Fhmax of the high-frequency limiter 32 is larger than the limit value Flmax of the low-frequency limiter 31, it is possible to output a control force with the electric actuator 6, 9 without limiting (reducing) it for a high-frequency movement resulting from a sudden steering input or impulse behavior such as a slalom or a double lane change.

[0066] According to the present embodiment, it is possible to reduce the heating value of the electric actuator 6, 9 while simultaneously ensuring driving comfort and steering stability.

[0067] More precisely, the controller 27 is designed to distribute a required thrust value, calculated by the calculation unit for calculating a required thrust 28 on the basis of detection values ​​of the respective sensors 18-24, to the low frequency band and the high frequency band by means of the low frequency filter 29 and the high frequency filter 30, to limit an amplitude by means of the low frequency limiter 31 and the high frequency limiter 32, and then to output a sum of these values ​​added by the addition unit 33 as a thrust instruction value.

[0068] Since the limit value Flmax of the low-frequency limiter 31 is set to a small value, it is possible to limit (reduce) any low-frequency control force (thrust force) output by the electric actuator 6, 9. Therefore, it is possible to reduce the heating value of the electric actuator 6, 9 to prevent insulation deterioration of the coils 14A, 14B, and 14C and irreversible flux losses of the permanent magnets 17. As a result, it is possible to use a permanent magnet with a lower retention force (magnetic force) than the permanent magnets 17 and a coil with a lower temperature characteristic than the coils 14A, 14B, and 14C, thus reducing the cost of the permanent magnets 17 and the coils 14A, 14B, and 14C.

[0069] Furthermore, since the limit value Fhmax of the high-frequency limiter 32 is large when a high-frequency control force is output by the electric actuator 6, 9, it is possible to output this control force without limitation (or, if at all, with a small limitation). As a result, it is possible to ensure driving comfort and steering stability.

[0070] According to the present embodiment, the controller 27 is configured to calculate a required thrust force value 28 from the measured values ​​of the respective sensors 18 and 24, using the calculation unit. More precisely, the controller 27 is configured such that the calculation unit uses sensor signals (measured values) from the respective sensors 18-24 for the calculation without dividing the control into position control and vibration control. As a result, a high control effect can be achieved. More precisely, for example,It is possible to increase the control effect compared to a configuration that calculates a signal from the sensors while dividing it into attitude control and vibration control, such as using a signal from the vertical acceleration sensor for vibration control and using lateral acceleration and vertical acceleration for attitude control.

[0071] According to the present embodiment, the controller 27 is configured to adjust the limit values ​​Flmax and Fhmax of the limiters 31 and 32 according to the temperature of the electric actuator 6, 9. Therefore, the limit values ​​Flmax and Fhmax are set to high values ​​when the temperature of the electric actuator 6, 9 is low, thus enabling maximum control force from the electric actuator 6, 9. As a result, driving comfort and steering stability are further improved. Conversely, the limit values ​​are set to low values ​​when the temperature of the electric actuator 6, 9 increases, thereby reducing the heating element of the electric actuator and preventing insulation deterioration of the coils and irreversible flux losses of the permanent magnets in a highly efficient manner.

[0072] According to the present embodiment, the controller 27 is configured to temporarily clear the limit values ​​Flmax and Fhmax of the limiters 31 and 32 according to the vehicle's operating condition. Therefore, in the event of an emergency such as sudden braking, it is possible to output maximum control force from the electric actuator 6, 9, regardless of whether it is operating in the high-frequency or low-frequency band. As a result, vehicle stability can be ensured in an emergency.

[0073] According to the present embodiment, the controller 27 is configured such that the high-frequency band corresponds to a high-frequency movement, such as a slalom or a double lane change of the vehicle, and the low-frequency band corresponds to a low-frequency movement, such as a constant rotation of the vehicle. Therefore, it is possible to reduce the control force of the electric actuator 6, 9 for a low-frequency movement, such as a constant rotation. As a result, it is possible to prevent the electric actuator 6, 9 from continuously outputting a large thrust force, thus reducing its heat generation. Conversely, it is possible to generate a large control force with the electric actuator 6, 9 for a high-frequency movement resulting from a sudden steering input and impulse response, such as a slalom or a double lane change.As a result, it is possible to ensure driving comfort and steering stability.

[0074] Next, show Fig. 5 a second embodiment of the present invention. The present invention is characterized in that the controller 27 is configured to extract a specific frequency band from a required thrust force value by means of a first filter, to limit an amplitude by means of a limiter, and to readjust a phase by means of a second filter, and then to generate a thrust force instruction value. In the following description of the present embodiment, features similar to those of the first embodiment described above are designated by the same reference numerals, and descriptions thereof are omitted.

[0075] For example, a controller 41 has a calculation unit for calculating a required thrust force 28, a first filter 42, a limiter 43, a first subtraction unit 44, a second filter 45, and a second reduction unit 46.

[0076] A thrust value calculated by the calculation unit for determining a required thrust 28 is distributed in two directions at the output of the calculation unit for determining a required thrust 28. One of these directions is input into the first filter 42, and the other is input into the second subtraction unit 46. The first filter 42 corresponds to the frequency band determination unit, which is an essential component of the present invention. The controller 41 is configured to input a required thrust value calculated by the calculation unit for determining a required thrust 28 into the first filter 42, and a predetermined frequency band is extracted from the required thrust value. The predetermined frequency band can, for example, be a low-frequency band corresponding to a low-frequency movement such as a constant rotation.

[0077] An output value X1 of the first filter 42 is distributed in two directions at the output side of the first filter 42. One of these is fed into the limiter 43, which limits the amplitude of a predetermined frequency band. The other is fed into the first subtraction unit 44. The first subtraction unit 44, together with the second filter 45 and the second subtraction unit 46, which is described below, forms the thrust instruction value calculation unit, which is an essential component of the present invention. The first subtraction unit 44 subtracts an output value X2 of the limiter 43 from the output value X1 of the first filter 42 to obtain a subtracted value ΔX.The controller 41 is then configured to adjust the phase of the subtracted value ΔX according to the required thrust value using the second filter 45, and then, using the second subtraction unit 46, to subtract the output value (the subtracted value ΔW with adjusted phase) of the second filter 45 from the required thrust value calculated by the required thrust value calculation unit 28, thereby forming a thrust instruction value. The second filter 45 adjusts the phase of the subtracted value ΔX according to the required thrust value and can, for example, be configured as the inverse filter of the first filter 42.

[0078] Assuming that a bound value (an upper bound value) of the limiter 43 is Xa, the limiter 43 will not function if the output value X1 of the first limiter 42, which is fed into the limiter 43, is a small value (magnitude of X1 ≤ Xa). More precisely, in this case, the relationship between the output value X1 of the first filter 42, which is fed into the first subtraction unit 44, and the output value X2 of the limiter 43 is X1 = X2, where the subtracted value ΔX, which is a difference between the output value X1 and the output value X2, becomes 0, as shown by the following equation 3. ΔX=X1−X2=0

[0079] In this case, the output value of the second filter 45, i.e., the subtracted ΔX with its phase adjusted by the second filter 45 according to the required thrust value, is also 0, with the required thrust value being output by the second subtraction unit 46 as a thrust instruction value without any modification being made to it. Therefore, it is possible to output the necessary thrust value to the inverter 26 as a thrust instruction value using the controller 41, without being affected by the first filter 42 and the limiter 43.

[0080] On the other hand, if the output value X1 of the first filter 42, which is fed into the limiter 43, is a large value (magnitude X1 > Xa), the second output value X2 is output by the first subtraction unit 44 as the subtracted value ΔX (= X1 - X2). The phase of this subtracted value ΔX is shifted under the influence of the first filter 42 and is therefore readjusted by the second filter 45. In other words, the second filter 45 adjusts the phase of the subtracted value ΔX according to the required thrust force. Then, the second subtraction unit 46 subtracts the subtracted value ΔX with its phase set by the required thrust force value, thereby outputting a difference (a subtraction value) between the required thrust force value and the subtracted value ΔX with its set phase as the thrust instruction value.

[0081] In this way, the second embodiment designed in this manner can also provide almost the same effect as the first embodiment described above. Specifically, according to the present embodiment, the controller 41 is configured to extract a specific frequency band from a required thrust force value, which is calculated by the computation unit for calculating a required thrust force 28, to limit the amplitude by means of the limiter 43, and to adjust the phase by means of the second filter 45, thereby generating a thrust force instruction value.

[0082] Therefore, in a case where the output value X1 of the first filter 42 is small (a movement of a given frequency band is small), it is possible to output a required thrust value, calculated using the calculation unit for calculating a required thrust 28, i.e., a required thrust value corresponding to an ideal control force based on a control logic such as the Sky Hook theory, to the inverter 26 without being influenced by the first filter 42, the limiter 43, and the second filter 45. Furthermore, in a case where the output value X1 of the first filter 42 If the movement within a given frequency band is large, the difference between the required thrust value and the subtracted value ΔX, with its phase set by the second filter 45, is output to the inverter 26 as a thrust instruction value. Therefore, in this case, it is also possible to reduce the influence of the first filter 42, i.e., any phase lead or delay caused by the first filter 42. As a result, it is possible to ensure driving comfort and steering stability in a highly efficient manner.

[0083] Next, show Fig. 6. A third embodiment of the invention. The present embodiment is characterized in that a controller is configured to convert a required thrust force value into a signal in the frequency domain FFT (Fast Fourier Transform), to limit the amplitude by means of a limiter, and then to generate a signal in the time period by conversion by inverse FFT as a thrust force instruction value. In the following description of the present embodiment, similar features to those of the first embodiment described above are designated by the same reference numerals, and descriptions thereof are omitted.

[0084] The controller 51, for example, has a calculation unit for calculating a required thrust force 28, an FFT unit 52, a limiter 53, and an inverse FFT unit 54.

[0085] A required thrust value calculated by the calculation unit 28 is entered into the FFT unit 52. The FFT unit 52 forms the frequency band determination unit, which is an essential component of the present invention. The FFT unit 52 is configured to convert a required thrust value, calculated by the calculation unit 28, into a signal in the frequency domain using FFT in order to distribute it across a plurality of frequency bands.

[0086] An output value Y of the FFT unit 52 is input into the limiter 53. This limiter 53 limits the amplitude of a signal (the output value Y) that is output by the FFT unit 52 for each frequency band. In this case, as in Fig. Figure 6 shows that the limit value L1 of a low-frequency band is set at a small value compared to the limit value Lh of a high-frequency band (Lh > Ll). Therefore, as shown in Fig. Figure 6 shows the output value Y of the FFT unit 52, which is input into the limiter 53, and is output by the limiter 53 as an output value Y'.

[0087] The output value Y' from the limiter 53 is input to the inverse FFT unit 54. The inverse FFT unit 54 forms the thrust instruction value calculation unit, which is an essential component of the present invention. The inverse FFT unit 54 converts the output value Y' of the limiter 51 into a time-domain signal using an inverse FFT to generate a thrust instruction value. The thrust instruction value is then output by the inverse FFT unit 54 to the inverter 26.

[0088] In this way, the third embodiment designed in this manner can provide almost the same effect as the first embodiment described above. Specifically, the controller 51 according to the present embodiment is designed such that the FFT unit 52 converts a required thrust force value into a signal in the frequency domain by means of FFT, the limiter 53 limits an amplitude, and the inverse FFT unit 54 performs an inverse FFT to convert it into a signal in the time domain, thereby generating a thrust force instruction value.

[0089] Therefore, it is possible to eliminate the influence of the filter (a leading and a delay of a phase) compared to the controller that uses the filter. Furthermore, the limiter 43 allows the limit value for each frequency band to be precisely set, making it possible to achieve both a reduction in the heating value of the electric actuator 6, 9 and to ensure driving comfort and steering stability with greater efficiency.

[0090] The embodiments described above were based on an example configured such that acceleration sensors 18-20, the steering angle sensor 21, the vehicle speed sensor 22, the lift sensor 23, and the temperature sensor 24 are used as the motion detection units. However, the present invention is not limited to this. The present invention can, for example, be configured such that a different motion detection unit, such as sensors for detecting, for example, the operating quantity of an accelerator and the state of a braking system, is used. In other words, the present invention can use any operating detection unit suitable for detecting a motion state of a vehicle, i.e., suitable for acquiring information indicating an operating state of the vehicle, as the motion detection unit, without specific limitations.

[0091] The present invention can, for example, use a GPS sensor that receives a GPS signal and detects the vehicle's state of motion, for example, by calculating road surface information (a vertical speed component), positional information, and altitude information based on the received signal. Furthermore, the present invention can use signals (information) from a preview sensor arranged in the vehicle and from a turn signal indicator. The present invention can also determine the vehicle's state of motion by predicting the vehicle's direction of movement and any disturbances caused by road surface information, vehicle speed information, and information from a turn signal indicator included in a vehicle navigation system.Furthermore, there is no restriction as to which motion detection unit should be used, and the present invention can be designed such that at least one motion detection unit is used.

[0092] The embodiments described above were based on an example configured such that the stator 10 of the electric actuator 6, 9 is attached to the vehicle body 1, which represents the sprung element of the vehicle, and the movable element 15 is attached to an axle, which represents the unsprung element of the vehicle. However, the present invention is not limited to this. The vehicle can, for example, be configured such that the stator is attached to the unsprung element of the vehicle, and the movable element is attached to the sprung element of the vehicle.

[0093] Furthermore, the respective embodiments described above were based on an example in which the electric actuator 6, 9 is a linear motor with a circular cross-section, i.e., the stator 10 and the movable element 15 are cylindrical. However, the present invention is not limited to this. The electric actuator 6, 9 can, for example, be formed by a linear motor with a shape other than circular, such as an I-shaped (flat plate-shaped), rectangular, or H-shaped cross-section. Furthermore, the electric actuator can be formed by a rotary motor and a ball screw mechanism instead of the linear motor.

[0094] According to the embodiments described above, it is possible to reduce the heating value of the electric actuator.

[0095] More precisely, the control unit is designed such that a required thrust force value, which is calculated by the calculation unit for calculating a required thrust force based on a detection value from the motion detection unit, is distributed across a multitude of frequency bands by the frequency band determination unit, an amplitude is limited by a limiter, and then a combination of these, which are combined by the thrust force instruction value calculation unit, is output as a thrust force instruction value.

[0096] In this way, the limiter thresholds are set such that the value in the low-frequency band is lower than in the high-frequency band. Therefore, when a low-frequency thrust force is output by the electric actuator, it is possible to limit (reduce) the thrust. Consequently, it is possible to reduce the heating value of the electric actuator, preventing the coils and permanent magnets that comprise it from suffering insulation degradation and irreversible flux losses. As a result, it is possible to use a permanent magnet with a lower retention force (magnetic force) and a coil with a lower temperature characteristic than the standard coils, thus reducing the cost of both the permanent magnets and the coils.

[0097] Furthermore, the limiter thresholds are set such that the value in the high-frequency band is higher than the value in the low-frequency band. Therefore, when a high-frequency control force is output by the electric actuator, it is possible to output this thrust force without limitation (or, if at all, with a very small limitation). As a result, it is possible to ensure driving comfort and steering stability.

[0098] According to one embodiment of the present invention, the controller is designed to adjust the threshold values ​​according to the temperature of the electric actuator. Therefore, when the temperature of the electric actuator is low, the threshold values ​​are set to high values, making it possible to output maximum thrust from the electric actuator. As a result, it is possible to further improve ride comfort and steering stability. Conversely, when the temperature of the electric actuator increases, the threshold values ​​are set to low values, thereby reducing the heating element of the electric actuator and preventing insulation deterioration of the coils and irreversible flux losses of the permanent magnets in a highly efficient manner.

[0099] According to one embodiment of the present invention, the controller is configured to temporarily reset the limiter thresholds based on the vehicle's operating condition. Therefore, in an emergency such as sudden braking, it is possible to output maximum thrust from the electric actuator, regardless of whether it is operating in the high-frequency or low-frequency band. As a result, operational stability can be ensured in an emergency.

[0100] According to one embodiment of the present invention, the controller is configured such that the high-frequency band corresponds to a high-frequency movement, such as a slalom or a double lane change of the vehicle, and the low-frequency band corresponds to a low-frequency movement, such as a constant rotation of the vehicle. Therefore, it is possible to reduce the thrust force of the electric actuator for a low-frequency movement such as a constant rotation. As a result, it is possible to prevent a large thrust force from being continuously output by the electric actuator, thereby reducing its heat generation. Conversely, it is possible to generate a large control force with the electric actuator for a high-frequency movement resulting from a sudden steering input and an environmental reaction, such as a slalom or a double lane change.As a result, it is possible to ensure driving comfort and steering stability.

[0101] According to one embodiment of the present invention, the controller is configured to distribute a required thrust value through the low-frequency filter and the high-frequency filter to the low-frequency band and the high-frequency band, to limit the respective amplitudes with the low-frequency limiter and the high-frequency limiter, and to add them together, thereby generating a thrust instruction value. Therefore, it is possible to achieve a simple structure using two filters and two limiters.

[0102] According to one embodiment of the present invention, the controller is configured to extract a specific frequency band from a required thrust value using the first filter, to limit the amplitude using the limiter, and to adjust the phase using the second filter, thereby generating a thrust instruction value. Therefore, it is possible to reduce the leading and lagging of the phase generated by the first filter.

[0103] According to one embodiment of the present invention, the controller is configured to convert a required thrust force value into a signal in the frequency domain using FFT, to limit the amplitude with the limiter, and to generate a signal in the time domain as a thrust force instruction value by conversion using an inverse FFT. Therefore, it is possible to eliminate the influence (phase lead and delay) of the filter, compared to a controller that uses the filter. Furthermore, it is possible to precisely set the limit values ​​for each frequency band, thus achieving both a reduction in the heating value of the electric actuator and ensuring driving comfort and steering stability in a highly efficient manner.

[0104] Although some exemplary embodiments of this invention have been described in detail above, the person skilled in the art will readily recognize that many modifications of these exemplary embodiments are possible without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are to be included within the scope of protection of this invention.

Claims

[1] Control device for an electric suspension (27, 41, 51) arranged between a body (1) and a wheel (2, 3) of a vehicle and designed to adjust a thrust force of an electric actuator (6, 9) according to a thrust force instruction value output by a control unit, wherein at least one motion detection unit (18, 19, 20, 21, 22, 23, 24) is connected to the control unit, and the motion detection unit (18, 19, 20, 21, 22, 23, 24) is configured to detect a motion state of the vehicle, the control unit features: a calculation unit for calculating a required thrust force (28), which is designed to calculate a required thrust force instruction value from a detection value that has been detected with the motion detection unit (18, 19, 20, 21, 22, 23, 24), a frequency band determination unit (29, 30, 42, 54) which is designed to distribute the calculated value of the calculation unit for calculating a required thrust force (28) to a plurality of frequency bands, a limiter (31, 32, 43, 53) provided for each of the frequency bands to which the calculated value is distributed by the frequency band determination unit (29, 30, 42, 54), and a thrust instruction value calculation unit (33, 44, 45, 46, 54) configured to generate the thrust instruction value by combining an output value of the limiter (31, 32, 43, 53) for each frequency band, and wherein a limit value of the limiter (31, 32, 43, 53) is set in such a way that one value (Flmax) in a low frequency band, as one of the frequency bands, is smaller than a value (Fhmax) in a high frequency band, as another of the frequency bands. [2] Control device for an electric suspension according to claim 1, wherein the limiter (31, 32, 43, 53) sets the limit value according to a temperature of the electric actuator (6, 9). [3] Control device for an electric suspension according to claim 1 or 2, wherein the control unit temporarily clears the limit value of the limiter (31, 32, 43, 53) according to the state of motion of the vehicle. [4] Control device for an electric suspension according to one of claims 1-3, wherein the high-frequency band, for example when the vehicle performs a slalom or a double lane change, corresponds to a high-frequency movement, and wherein the low-frequency band, for example when the vehicle performs a constant rotation, corresponds to a low-frequency movement. [5] Control device for an electric suspension according to one of claims 1-4, in which the frequency band determination unit (29, 30, 42, 54) is configured to distribute the calculated value of the calculation unit for calculating a required thrust force (28) through a low frequency filter (29) to the low frequency band and through a high frequency filter (30) to the high frequency band, wherein the limiter (31, 32, 43, 53) comprises a low-frequency limiter (31) that limits an amplitude in the low-frequency band, and a high-frequency limiter (32) that limits an amplitude in the high-frequency band, wherein the thrust instruction value calculation unit (33, 44, 45, 46, 54) generates the thrust instruction value by adding an output value of the low frequency limiter (31) and an output value of the high frequency limiter (32), and where the limit value (Flmax) of the low frequency limiter (31) is smaller than the limit value (Fhmax) of the high frequency limiter (32). [6] Control device for an electric suspension according to one of claims 1-4, in which the frequency band determination unit (29, 30, 42, 54) is designed to input the calculated value of the calculation unit for calculating a required thrust force (28) to a first filter (42) and to determine a specified frequency band using the first filter (42), where the limiter (31, 32, 43, 53) limits an amplitude in the specified frequency band, wherein the shear force instruction value calculation unit (33, 44, 45, 46, 54) determines a subtracted value (ΔX) by subtracting an output value (X2) of the limiter (31, 32, 43, 53) from an output value (X1) of a first filter (42), sets a phase of the subtracted value (ΔX) according to the calculated value of the calculation unit for calculating a required shear force (28) by means of a second filter (45), and subtracts the subtracted value (ΔX) with its set phase from the calculated value of the calculation unit for calculating a required shear force (28), thereby generating the shear force instruction value. [7] Control device for an electric suspension according to one of claims 1-4, in which the frequency band determination unit (29, 30, 42, 54) is configured to convert the calculated value of the calculation unit for calculating a required thrust force (28) into a signal in a frequency space by means of fast Fourier transform (FFT), and to distribute the converted signal to a multitude of frequency bands, where the limiter (31, 32, 43, 53) limits the amplitude of a signal that has been converted by FFT for each frequency band, and wherein the thrust instruction value calculation unit (33, 44, 45, 46, 54) converts an output value of the limiter (31, 32, 43, 53) into a signal in a period of time by inverse FFT to generate the thrust instruction value.

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