JP2025124308A - Suspension control device and suspension control method - Google Patents

Abstract

To provide a suspension control device and a suspension control method capable of switching the drive speed of an actuator according to the raising or lowering direction of a suspension device, and stabilizing inverter power supply voltage during turning and the like.SOLUTION: A suspension control device for controlling a suspension device equipped with an actuator that extends and contracts the overall length of the suspension device so as to enable vehicle height to be raised or lowered, comprises: an operation state detection unit that detects an operation state of a vehicle by a driver; a drive stroke calculation unit that calculates a target drive stroke amount of the suspension device on the basis of information acquired by the operation state detection unit; a drive speed determination unit that determines a target drive speed for extending and contracting the overall length of the suspension device; and an actuator control unit that controls the actuator at the target drive speed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a suspension control device and suspension control method that drives a suspension device that allows the vehicle height to be raised or lowered.

A known suspension system is a suspension device installed between the vehicle body and wheels, which includes a damping mechanism and an actuator powered by a motor arranged in parallel, with the actuator configured to drive a drive mechanism via the motor via a connecting section, the connecting section including a suspension device equipped with a clutch mechanism, and a control device that inputs information regarding the vehicle's running state and road surface conditions and outputs control commands to the clutch mechanism and the motor, and the control device outputs a control command to switch the clutch mechanism between engagement and disengagement depending on the vehicle's running state and road surface conditions.

With this type of suspension system, by switching between connecting and disconnecting the clutch mechanism, it is possible to select between a state in which the damping force of the fluid-based damping mechanism is applied to the suspension device, and a state in which the damping force of the fluid-based damping mechanism and the damping force of the actuator are simultaneously applied to the suspension device, thereby stabilizing the vehicle body posture with low power consumption.

JP 2022-64380 A

A commonly known method of controlling suspension systems that allows for raising and lowering vehicle height involves driving the suspension systems located on the outside of a turning vehicle in a direction that pushes the vehicle up, and the suspension systems located on the inside of a turning vehicle in a direction that pushes the vehicle down, in response to the roll rotation that occurs in the vehicle body during a turn. Hereinafter, in this specification, control of suspension systems that responds to such roll rotation that occurs in the vehicle body is referred to as reverse roll control.

In reverse roll control, the suspension device located on the outside of the turn consumes power to drive its actuator, controlling it so that its overall length increases. Meanwhile, the suspension device located on the inside of the turn is controlled so that its overall length decreases, with the motor attached to the actuator functioning as a generator to generate regenerative power. As a result, the actuator associated with the suspension device on the inside of the turn is controlled regeneratively, and the rotational energy applied to the motor is converted into electricity.

With conventional suspension control methods, if the motors associated with the suspension devices located on the outside and inside of a turn are driven at the same time and at the same rotation speed, as shown in Figure 9(a), the power generated by regenerative control may exceed the power consumed, as shown in Figure 9(b). In such cases, there is an issue where the inverter power supply voltage driving the motor rises above the specified upper protection voltage, as shown in Figure 9(c). When the inverter power supply voltage exceeds the upper protection voltage, the inverter's failsafe is activated, causing the vehicle's behavior during turns to deteriorate.

Furthermore, in order to adapt electrical circuits to such increases in inverter power supply voltage, components such as power cables and connectors must be enlarged for higher voltages, which poses the problem of higher manufacturing costs.

The present invention has been made to solve the above-mentioned problems, and aims to provide a suspension control device and suspension control method that can switch the actuator drive speed depending on the lifting direction of the suspension device, thereby stabilizing the inverter power supply voltage when the vehicle is cornering, etc.

A suspension control device that solves the above problem controls a suspension device equipped with an actuator that drives the suspension device to extend and retract its entire length so that the vehicle height can be raised and lowered. The suspension control device is characterized by comprising an operation state detection unit that detects the vehicle operation state by the driver, a drive stroke calculation unit that calculates a target drive stroke amount for the suspension device based on information acquired by the operation state detection unit, a drive speed determination unit that determines a target drive speed at which the suspension device extends and retracts its entire length, and an actuator control unit that controls the actuator at the target drive speed.

A suspension control method that solves the above problem controls a suspension device equipped with an actuator that drives the suspension device to extend and retract its entire length so that the vehicle height can be raised and lowered, and is characterized by comprising: an operation state detection process that detects the vehicle operation state by the driver; a drive stroke calculation process that calculates a target drive stroke of the suspension device based on information acquired by the operation state detection process; a drive speed determination process that determines a target drive speed at which the entire length of the suspension device is extended and retracted; and an actuator control process that controls the actuator at the target drive speed.

The suspension control device and suspension control method of the present invention can stabilize the inverter power supply voltage by switching the actuator drive speed depending on the lifting direction of the suspension device, improving the rate of change in reverse roll during reverse roll control, enabling control that tracks the driver's operating speed, and reducing the cost of components that make up the electrical circuit.

1 is a schematic diagram showing the configuration of a vehicle equipped with a suspension control device according to an embodiment of the present invention. 1 is a schematic diagram for explaining a suspension device according to an embodiment of the present invention; FIG. 2 is a schematic diagram showing the configuration of a drive speed determination unit according to the embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a power supply connected to an actuator control device according to an embodiment of the present invention. 3 is a flowchart showing a control example of the suspension control method according to the first embodiment of the present invention. 10 is a flowchart showing a control example of a suspension control method according to a second embodiment of the present invention. 10 is a flowchart showing a control example of a suspension control method according to a third embodiment of the present invention. 1A and 1B are diagrams showing the effect of controlling a suspension device using the suspension control method of the present invention, in which (a) is the drive stroke amount of the suspension device, (b) is the battery power consumption, and (c) is the inverter power supply voltage. 1A and 1B are diagrams showing the effect of controlling a suspension device using a conventional suspension control method, in which (a) is the drive stroke of the suspension device, (b) is the battery power consumption, and (c) is the inverter power supply voltage.

Embodiments of a suspension control device according to the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

Figure 1 is a schematic diagram showing the configuration of a vehicle equipped with a suspension control device according to an embodiment of the present invention, Figure 2 is a schematic diagram for explaining a suspension device according to an embodiment of the present invention, Figure 3 is a schematic diagram showing the configuration of a drive speed determination unit according to an embodiment of the present invention, and Figure 4 is a schematic diagram showing an example of a power supply connected to an actuator control device according to an embodiment of the present invention.

As shown in FIG. 1, a vehicle 1 equipped with a suspension control device according to an embodiment of the present invention has wheels 2 arranged at the front, rear, left, and right of the vehicle 1, and a suspension device 3. The wheels 2 are attached to the vehicle body via suspension arms so that they can move up and down.

First, we will explain the suspension device 3 related to the present invention.

As shown in Figure 2, the suspension device 3 is attached between each wheel 2 and the vehicle body to absorb vibrations and shocks input from the road surface and ensure driving stability. The suspension device 3 has a spring 4, a shock absorber 5, and an actuator 6.

Spring 4 is a compression coil spring that supports the vehicle weight and determines the amount of tilt of the vehicle body that occurs in the front, rear, left, and right directions while driving, depending on the spring's stiffness. Spring 4 expands and contracts in accordance with the unevenness of the road surface, keeping wheel 2 from leaving the road surface.

The shock absorber 5 suppresses the movement of the oscillating spring 4. The shock absorber 5 is positioned inside the spring 4 and concentric with it. In this embodiment, the shock absorber 5 may be configured to generate a damping force using hydraulic oil filled inside the shock absorber 5 and a piston that can move up and down within the hydraulic oil, as an example.

The actuator 6 adjusts the height of the vehicle body from the ground by expanding or contracting the entire length of the suspension device 3, thereby changing the distance between each wheel 2 and the vehicle body. The actuator 6 includes, for example, a drive device 7, a screw shaft 8, and a nut 9.

The drive unit 7 includes a motor 7a controlled by a signal from the actuator control unit 40 (described later), and a gear device that transmits the power of the motor 7a to the screw shaft 8.

The screw shaft 8 is positioned so that it connects to the axis of the shock absorber 5 and extends coaxially. As an example, the screw shaft 8 has a male thread, such as a trapezoidal thread, formed on its outer surface. Furthermore, the screw shaft 8 is supported by a rotation prevention mechanism so that it cannot rotate relative to the body of the actuator 6 but can move axially.

The nut 9 is arranged to surround the screw shaft 8. As an example, the nut 9 has an internal thread such as a trapezoidal thread formed on its inner surface that can be threaded with the external thread of the screw shaft 8. The nut 9 receives power from the motor 7a of the drive unit 7 via a gear device, causing it to rotate about its axis. The nut 9 is rotatably attached to the axis of the screw shaft 8 via a bearing or the like, and is attached so that it cannot move vertically relative to the vehicle body.

The suspension device 3 configured in this manner can extend and retract its overall length through the operations described below.

When a signal from the actuator control unit 40 rotates the motor 7a provided in the drive unit 7, the nut 9 rotates due to a gear device connected to the output shaft of the motor 7a. The screw shaft 8 that threads onto the nut 9 is supported non-rotatably by a rotation-prevention mechanism, and moves up and down in the axial direction according to the direction of rotation of the nut 9. The shock absorber 5 connected to the screw shaft 8 moves up and down together with the screw shaft 8, expanding and contracting the overall length of the suspension unit 3.

In the above description, the screw shaft 8 and nut 9 are threaded together using a trapezoidal screw or the like, but the configuration of the screw shaft 8 and nut 9 is not limited to this. They may also be configured as a ball screw, with multiple balls interposed between the screw groove of the screw shaft 8 and the screw groove of the nut 9 so that they can roll.

In addition, while the shock absorber 5 is connected to the threaded shaft 8 and the nut 9 is rotated to move the threaded shaft 8 up and down, thereby expanding and contracting the overall length of the suspension device 3, the structure for expanding and contracting the overall length of the suspension device 3 is not limited to this. For example, the shock absorber 5 may be connected to the nut 9 and the threaded shaft 8 may be rotated by the drive unit 7 to move the nut 9 up and down, thereby expanding and contracting the overall length of the suspension device 3. In this case, the nut 9 is supported by a rotation prevention mechanism so that it cannot rotate around its axis but can move axially along the threaded shaft 8, and the threaded shaft 8 is supported via a bearing or the like so that it can rotate around the axis of the nut 9 but cannot move vertically relative to the vehicle body.

Furthermore, the drive unit 7 has been described as having a gear device and transmitting power from the motor 7a to rotate the screw shaft 8 or the nut 9, but the structure for rotating the screw shaft 8 or the nut 9 is not limited to this, and the screw shaft 8 or the nut 9 may also be rotated directly by a hollow motor.

Next, we will explain the suspension control device that drives such a suspension device 3. As shown in Figure 1, the suspension control device according to this embodiment includes an operation state detection unit 10, a drive stroke calculation unit 20, a motion state detection unit 60, and a suspension control unit 100. The suspension control units 100 are installed corresponding to each of the suspension devices 3 installed on the front, rear, left, and right sides of the vehicle 1. Figure 1 shows only the components of the suspension control unit 100 corresponding to the suspension device 3 installed on the front left, and the other components of the suspension control unit 100 are not shown.

The operation state detection unit 10 detects information related to the operation state of the vehicle 1 by the driver. In this specification, the operation state of the vehicle 1 by the driver refers to, for example, predetermined actions by the driver, such as the steering angle of the steering wheel or the amount of depression of the accelerator pedal by the driver. The operation state detection unit 10 includes, for example, a steering wheel angle sensor and an accelerator stroke sensor. The operation state detection unit 10 outputs the detected signal to the drive stroke calculation unit 20.

The drive stroke calculation unit 20 calculates the amount of extension and contraction of the suspension devices 3 provided on the front, rear, left, and right sides of the vehicle 1 based on signals input from the operation state detection unit 10, the motion state detection unit 60, and the load measurement unit 50 (described later). Specific calculation methods will be described later. In this specification, the appropriate amount of extension and contraction of the suspension devices 3 calculated by the drive stroke calculation unit 20 is referred to as the target drive stroke amount. The drive stroke calculation unit 20 outputs the target drive stroke amount to the suspension control unit 100.

The motion state detection unit 60 detects the motion state of the vehicle 1 while it is moving. The motion state detection unit 60 includes, for example, a vehicle speed sensor that detects vehicle speed, an acceleration sensor that detects acceleration in the front, rear, left, and right directions of the vehicle body, and a yaw rate sensor that detects the yaw rate generated in the vehicle body. The motion state detection unit 60 outputs the detected information to the drive stroke calculation unit 20.

The suspension control unit 100 includes a drive speed determination unit 30, an actuator control unit 40, and a load measurement unit 50.

The drive speed determination unit 30 determines an appropriate drive speed when extending or retracting the overall length of the suspension unit 3. In this specification, the drive speed of the suspension unit 3 determined by the drive speed determination unit 30 is referred to as the target drive speed. As shown in FIG. 3, the drive speed determination unit 30 includes a drive direction determination device 31, a descending rotation speed calculation device 32, an ascending rotation speed calculation device 33, and a selector switch 34.

The drive direction determination device 31 determines the extension/contraction direction of the suspension unit 3, i.e., whether to operate in the contraction direction or extension direction, based on the target drive stroke amount input from the drive stroke calculation unit 20. The drive direction determination device 31 outputs the determination result regarding the extension/contraction direction of the suspension unit 3 to the selector switch 34.

The lowering rotation speed calculation device 32 calculates the motor rotation speed at which the motor 7a is driven in order to retract the suspension device 3 at an appropriate drive speed when lowering the vehicle height. The lowering rotation speed calculation device 32 may also calculate an appropriate motor rotation speed based on information detected by the load measurement unit 50 and the motion state detection unit 60. Specific calculation methods will be described later. In this specification, the motor rotation speed calculated by the lowering rotation speed calculation device 32 is referred to as the lowering motor rotation speed.

The increase rotation speed calculation device 33 calculates the motor rotation speed at which the motor 7a is driven in order to extend the suspension device 3 at an appropriate drive speed when raising the vehicle height. The increase rotation speed calculation device 33 may also calculate an appropriate motor rotation speed based on information detected by the load measurement unit 50 and the motion state detection unit 60. Specific calculation methods will be described later. In this specification, the motor rotation speed stored in the increase rotation speed calculation device 33 is referred to as the increase motor rotation speed.

The selector switch 34 outputs either the lowering motor rotation speed or the ascending motor rotation speed to the actuator control unit 40 based on the determination result of the extension/contraction direction by the drive direction determination device 31. In this specification, the motor rotation speed of the motor 7a output by the selector switch 34 is referred to as the target rotation speed. The target rotation speed is the motor rotation speed of the motor 7a that corresponds to the target drive speed of the suspension device 3.

The actuator control unit 40 controls the motor 7a to rotate at the target rotation speed based on the signal input from the drive stroke calculation unit 20 and the signal input from the selector switch 34 of the drive speed determination unit 30, and controls the suspension device 3 to expand or contract the target drive stroke amount at the target drive speed.

As shown in FIG. 4, the actuator control unit 40 is also connected to a power source for driving the actuator 6. It is preferable to have multiple power sources connected to the actuator control unit 40, such as a power source obtained by stepping down the DC voltage from the driving battery 41 using a DC/DC converter 42, and a power source from an auxiliary battery 43. By providing multiple power sources in this way, it is possible to supply power to the actuator 6 stably even when a large amount of power is consumed temporarily.

The actuator control unit 40 has an internal inverter circuit and controls the output voltage of the current supplied to the motor 7a from the driving battery 41 or auxiliary battery 43. Note that in this specification, the voltage related to the inverter circuit provided in the actuator control unit 40 is referred to as the inverter power supply voltage.

The load measurement unit 50 detects the load applied to each suspension device 3. This load detection is preferably performed by measuring the load applied to the actuator 6 using a sensor or the like. However, the method for detecting this load is not limited to this; the load applied to the suspension device 3 can be detected using various methods, such as a pressure sensor attached between the suspension device 3 and the vehicle body. The load measurement unit 50 outputs the detected load to the drive stroke calculation unit 20.

Next, a method for controlling the elevation and lowering of the suspension device 3 using the suspension control device of the present invention will be described based on the following embodiment.

[First embodiment]
5 is a flowchart showing a control example of the suspension control method according to the first embodiment. Hereinafter, this control method will be described using an example in which the vehicle 1 is turning.

In step S1, the operation state detection unit 10 detects the operation state of the vehicle 1 by the driver, such as the steering angle of the steering wheel and the amount of depression of the accelerator pedal by the driver. In this embodiment, the process in step S1 is defined as the operation state detection process.

In step S2, the drive stroke calculation unit 20 calculates the target drive stroke amount for each suspension device 3 located on the left and right sides of the vehicle 1 based on the driver's operation of the vehicle 1 detected in step S1. When the driver is steering the steering wheel and the vehicle 1 is turning, the target drive stroke amount is calculated so that the outside of the turning side of the vehicle body is raised and the inside of the turning side of the vehicle body is lowered, thereby controlling each suspension device 3 to perform reverse roll control.

Furthermore, in such a turning state, the target drive stroke amount of each suspension device 3 may be calculated in response to the acceleration or deceleration of the vehicle during turning based on the steering wheel angle detected in step S1 as well as the accelerator pedal depression amount. In this embodiment, the process in step S2 is defined as the drive stroke calculation process.

In step S3, the descent motor rotation speed calculation device 32 and the ascent motor rotation speed calculation device 33 calculate the descent motor rotation speed and the ascent motor rotation speed. In this embodiment, it is preferable that the ascent motor rotation speed is faster than the descent motor rotation speed. That is, it is preferable that the suspension device 3 be extended at a fast drive speed when raising the vehicle height, and that the suspension device 3 be retracted at a slow drive speed when lowering the vehicle height. Furthermore, the ascent motor rotation speed and the descent motor rotation speed may be fixed values. In this embodiment, the process in step S3 is defined as a rotation speed calculation process.

In step S4, the drive direction determination device 31 determines the extension/contraction direction of the suspension device 3 based on the target drive stroke amount calculated in step S2. When the vehicle 1 is turning, the target drive stroke amount for the outside of the turn is determined to be drive in the direction that extends the suspension device 3 in order to raise the vehicle body. Furthermore, the target drive stroke amount for the inside of the turn is determined to be drive in the direction that retracts the suspension device 3 in order to lower the vehicle body. In this embodiment, the process in step S4 is referred to as the drive direction determination process.

In step S5, based on the result of the determination in step S4, the selector switch 34 is switched to determine either the descent motor rotation speed or the ascent motor rotation speed as the target rotation speed. When the vehicle 1 is turning, the target rotation speed is determined so that the drive speed that extends the overall length of the suspension device is faster than the drive speed that shortens the overall length of the suspension device. In other words, the target rotation speeds corresponding to each suspension device 3 are determined so that the target rotation speed for the outside of the turn becomes the ascent motor rotation speed, and the target rotation speed for the inside of the turn becomes the descent motor rotation speed. In this embodiment, the process in step S5 is defined as the drive speed determination process.

In step S6, the actuator control unit 40 outputs a command value to the drive device 7 based on the target drive stroke amount calculated in step S2 and the target rotation speed determined in step S5, thereby operating the motor 7a. In this embodiment, the process in step 6 is defined as the actuator control process.

In this suspension control method according to the first embodiment, the motor 7a receives a signal from the actuator control unit 40 and rotates at the target rotation speed to drive the actuator 6. By driving the actuator 6, the suspension device 3 expands or contracts the target drive stroke amount at the target drive speed.

Second Embodiment
As explained above, the suspension control method according to the first embodiment determines the drive direction and target rotation speed of each suspension device 3 based on the driver's operation of the vehicle 1, such as the steering angle of the steering wheel and the amount of depression of the accelerator pedal, and controls the extension and contraction of the target drive stroke amount of each suspension device 3 at a target drive speed. Next, a suspension control method according to a second embodiment will be explained, which is different from the first embodiment.

Generally, the weight balance of a vehicle 1 varies from front to back and from side to side depending on the vehicle model. For example, the vehicle weight and weight balance vary greatly between a passenger car and a truck, and even for the same truck, the total vehicle weight and weight balance may differ depending on the load. When the weight balance of a vehicle 1 varies from front to back and from side to side, the magnitude of the roll direction rotation occurring in the vehicle body varies depending on the turning direction. For example, if the drive amount and drive speed of each suspension unit 3 driven when turning right are the same as the drive amount and drive speed of each suspension unit 3 driven when turning left, ride comfort may be adversely affected.

The suspension control method according to the second embodiment is a control method for solving the above-mentioned problems, and aims to provide a suspension control method that controls the extension and contraction of each suspension device 3 by a target drive stroke amount at a target drive speed based on the vehicle 1's front-rear and left-right weight balance as well as the vehicle 1's operating state by the driver, thereby enabling suitable vehicle control that does not cause the driver to feel uncomfortable. Note that steps that are the same as or similar to those in the first embodiment described above are assigned the same reference numerals and detailed descriptions are omitted.

Figure 6 is a flowchart showing an example of a suspension control method according to the second embodiment. Below, this control method will be explained using an example in which the vehicle 1 is turning.

Step S1 is the same as in the first embodiment.

In step S11, the load measurement unit 50 detects the loads applied to the front, rear, left, and right suspension devices 3. In this embodiment, the process in step S11 is defined as the load distribution detection process.

In step S21, the drive stroke calculation unit 20 calculates the target drive stroke amount for each suspension device 3 based on the driver's operation of the vehicle 1 detected in step S1, as well as the loads acting on the front, rear, left, and right suspension devices 3 of the vehicle 1 detected in step S11.

When the vehicle 1 is turning, the target drive stroke amount is calculated for each suspension device 3 so that the outside of the turning vehicle body is raised and the inside of the turning vehicle body is lowered.

In addition, the target drive stroke amount is calculated to provide an appropriate drive amount, such as increasing the drive amount for suspension devices 3 that are under a greater load, depending on the front-rear and left-right weight balance of the vehicle 1. In this embodiment, the process in step S21 is defined as a drive stroke calculation process, similar to the process in step S2.

In step S31, the descent rotation speed calculation device 32 and the ascent rotation speed calculation device 33 calculate the descent motor rotation speed and the ascent motor rotation speed based on the load detected in step S11.

In this embodiment, it is preferable that the rotational speed of the raising motor be faster than the rotational speed of the lowering motor. In other words, it is preferable that the suspension device 3 be extended at a high drive speed when raising the vehicle height, and that the suspension device 3 be retracted at a slow drive speed when lowering the vehicle height.

In addition, depending on the front-rear and left-right weight balance of the vehicle 1, the lowering motor rotation speed and the ascent motor rotation speed are calculated to achieve an appropriate suspension device 3 drive speed, such as by increasing the motor rotation speed to increase the drive speed for suspension devices 3 that are under a greater load. In this embodiment, the process in step S31 is defined as a rotation speed calculation process, similar to the process in step S3.

Steps S4 to S6 are the same as in the first embodiment.

In this suspension control method according to the second embodiment, the motor 7a receives a signal from the actuator control unit 40 and drives the actuator 6 by rotating at a target rotation speed according to the weight balance of the vehicle 1. By driving the actuator 6, the suspension device 3 expands or contracts the target drive stroke amount according to the target drive speed.

[Third embodiment]
As explained above, the suspension control method according to the second embodiment determines the drive direction and target rotation speed of each suspension device 3 according to the operation state of the vehicle 1 by the driver as well as the front-rear and left-right weight balance of the vehicle 1, and controls the extension and contraction of the target drive stroke amount of each suspension device 3 at the target drive speed. Next, a suspension control method according to the third embodiment will be explained, which is different from the first and second embodiments.

As described above, reverse roll control reduces the outward acceleration felt by the driver inside the vehicle when rolling in response to roll rotation of the vehicle body, improving ride comfort. However, when vehicle 1 accelerates, an upward force is generated at the front of the vehicle body, and when it decelerates, a downward force is generated, and such pitch rotation may also worsen ride comfort.

The suspension control method according to the third embodiment is a control method for solving the above-mentioned problems, and aims to provide a suspension control method that controls the extension and contraction of each suspension device 3 by a target drive stroke amount at a target drive speed based on the vehicle 1's operating state by the driver as well as the vehicle's motion state, such as acceleration and deceleration, thereby providing suitable vehicle control that does not cause discomfort to the driver. Note that steps that are the same as or similar to those in the first and second embodiments described above are designated by the same reference numerals and detailed descriptions are omitted.

Figure 7 is a flowchart showing an example of a suspension control method according to the third embodiment. Below, this control method will be explained using an example in which the vehicle 1 is turning while accelerating or decelerating.

Step S1 is the same as in the first embodiment.

In step S12, the motion state detection unit 60 detects the motion state, such as acceleration or deceleration, of the vehicle 1 while it is running. In this embodiment, the process in step S12 is defined as the motion state detection process.

In step S22, the drive stroke calculation unit 20 calculates the target drive stroke amount for each suspension device 3 based on the driver's operation of the vehicle 1 detected in step S1, as well as the vehicle's motion state, such as acceleration and deceleration, detected in step S12.

When the vehicle 1 is accelerating while turning, the target drive stroke amount is calculated for each suspension device 3 so that the outside of the turning vehicle body is raised and the inside of the turning vehicle body is lowered.

The target drive stroke amount of the front suspension unit 3 and the target drive stroke amount of the rear suspension unit 3 are also changed appropriately depending on the speed and acceleration of the vehicle 1 while it is traveling. For example, when the vehicle 1 is accelerating, a force is generated that causes the front of the vehicle 1 to lift up, so the target drive stroke amount is calculated to provide an appropriate drive amount, such as by increasing the drive amount of the rear suspension unit 3 compared to the front. In this embodiment, the process in step S22 is defined as a drive stroke calculation process, similar to the process in step S2.

In step S32, the descent rotation speed calculation device 32 and the ascent rotation speed calculation device 33 calculate the descent motor rotation speed and the ascent motor rotation speed based on the motion state of the traveling vehicle 1, such as acceleration and deceleration, detected in step S12.

In this embodiment, it is preferable that the rotational speed of the raising motor be faster than the rotational speed of the lowering motor. In other words, it is preferable that the suspension device 3 be extended at a high drive speed when raising the vehicle height, and that the suspension device 3 be retracted at a slow drive speed when lowering the vehicle height.

In addition, depending on the motion state of the vehicle 1 during travel, such as acceleration and deceleration, the lowering motor rotation speed and the ascending motor rotation speed are calculated to achieve an appropriate drive speed for the suspension device 3, such as by increasing the motor rotation speed to increase the drive speed for suspension devices 3 with larger drive amounts. In this embodiment, the process in step S32 is defined as a rotation speed calculation process, similar to the process in step S3.

Steps S4 to S6 are the same as in the first embodiment.

In this suspension control method according to the third embodiment, the motor 7a receives a signal from the actuator control unit 40 and drives the actuator 6 by rotating at a target rotation speed that corresponds to the motion state of the vehicle 1 while it is in motion. By driving the actuator 6, the suspension device 3 expands or contracts the target drive stroke amount according to the target drive speed.

Next, the relationship between the movement of the suspension device 3, which expands and contracts using the suspension control method of the present invention, and the inverter power supply voltage will be explained using an example of the vehicle 1 turning.

Figure 8 shows the effect of controlling a suspension device using the suspension control method of the present invention, where (a) shows the drive stroke of the suspension device, (b) shows battery power consumption, and (c) shows the inverter power supply voltage.

As described above, according to the suspension control method of this embodiment, the target drive speed is set so that the suspension unit 3 extends at a high drive speed when raising the vehicle height, and retracts at a slow drive speed when lowering the vehicle height. Therefore, as shown in Figure 8(a), the suspension unit 3 arranged on the side that raises the vehicle body is driven to reach the target drive stroke amount more quickly than the suspension unit 3 arranged on the side that lowers the vehicle body.

In addition, when raising the vehicle body, power is consumed to drive the actuator 6, and the suspension device 3 is controlled to extend its overall length, while when lowering the vehicle body, the suspension device 3 is controlled to shorten its overall length, causing the motor 7a provided on the actuator 6 to function as a generator and generate regenerative power.

For this reason, when the vehicle 1 is turning, the relationship between the power consumption and regenerative power of the suspension devices 3 on the outside and inside of the turn is as shown in Figure 8(b), where power consumption temporarily increases when the vehicle body rises, but thereafter power is gradually generated by regenerative control and stored in the auxiliary battery 43, etc.

This relationship between power consumption and regenerative power means that, unlike conventional suspension control methods, the regenerative power does not exceed the power consumption, and the inverter power supply voltage can be stabilized, as shown in Figure 8 (c).

As such, the suspension control method of the present invention can stabilize the inverter power supply voltage when the vehicle 1 is turning, thereby preventing deterioration in the behavior of the vehicle 1 while turning. Furthermore, because it is possible to prevent an increase in the inverter power supply voltage due to regenerative power from the suspension device 3, it is possible to reduce the size of power cables, connectors, etc., thereby reducing manufacturing costs.

Note that while the suspension control method according to the present invention has been described in terms of the second embodiment and the third embodiment, these control methods may be used independently or in combination. Furthermore, the suspension control device and suspension control method according to the present invention have been described as being installed in a vehicle 1 with a driver, such as a passenger car or truck, but this is not limiting and the device may also be applied to vehicles such as delivery robots that are operated from the outside without a driver inside. It is clear from the claims that such modified or improved forms are also within the technical scope of the present invention.

1 Vehicle, 3 Suspension device, 6 Actuator, 7a Motor, 10 Operation state detection unit, 11 Steering wheel angle sensor, 20 Drive stroke calculation unit, 30 Drive speed determination unit, 31 Drive direction determination device, 34 Changeover switch, 40 Actuator control unit, 50 Load measurement unit, 60 Motion state detection unit.

Claims (5)

1. A suspension control device for controlling a suspension device having an actuator that drives the suspension device to extend and retract an entire length of the suspension device so as to be able to raise and lower a vehicle height,
an operation state detection unit that detects an operation state of the vehicle by the driver;
a drive stroke calculation unit that calculates a target drive stroke amount of the suspension device based on information acquired by the operation state detection unit;
a drive speed determination unit that determines a target drive speed at which the entire length of the suspension device is extended or contracted;
an actuator control unit that controls the actuator at the target drive speed. 2. The suspension control device according to claim 1,
the actuator comprises a motor;
The suspension control device is characterized in that the drive speed determination unit determines a target rotation speed of the motor corresponding to the target drive speed. 3. The suspension control device according to claim 2,
the drive speed determination unit includes a drive direction determination device that determines a direction in which the vehicle height is raised or lowered;
A suspension control device comprising: a changeover switch that switches the target rotation speed based on the direction of raising or lowering the vehicle height determined by the drive direction determination device. 1. A suspension control method for controlling a suspension device having an actuator that drives the suspension device to extend and retract an entire length thereof so as to enable raising and lowering of a vehicle height, comprising:
an operation state detection step of detecting an operation state of the vehicle by the driver;
a drive stroke calculation step of calculating a target drive stroke of the suspension device based on the information acquired in the operation state detection step;
a drive speed determination step of determining a target drive speed at which the entire length of the suspension device is extended or contracted;
an actuator control step of controlling the actuator at the target drive speed. 5. The suspension control method according to claim 4,
a drive speed determining step of determining the target drive speed so that a drive speed that extends the overall length of the suspension device is faster than a drive speed that shortens the overall length of the suspension device;