Suspension control device and suspension control method

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

[Technical Field]

[0001] The present invention relates to a suspension control device and a suspension control method for driving a suspension device that enables raising and lowering of a vehicle height. [Background technology]

[0002] A known suspension system is a suspension device provided between the body and wheels of a vehicle, in which a damping mechanism and an actuator powered by a motor are provided in parallel, and the actuator is configured to drive a drive mechanism using the motor via a connecting section, and the connecting section is equipped with a suspension device having a clutch mechanism, and a control device that inputs information regarding the running state of the vehicle 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 between connecting and disconnecting the clutch mechanism depending on the running state of the vehicle and road surface conditions.

[0003] With such a 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 posture of the vehicle body with low power consumption. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-64380 Summary of the Invention [Problem to be solved by the invention]

[0005] A commonly known method of controlling suspension systems that enables raising and lowering vehicle height is to drive the suspension systems located on the outside of the turn in a direction that pushes the vehicle up and the suspension systems located on the inside of the turn 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.

[0006] In reverse roll control, the suspension unit on the outside of the turn consumes power to drive its actuator, controlling it to extend its overall length. Meanwhile, the suspension unit on the inside of the turn is controlled to shorten its overall length, with the motor attached to the actuator functioning as a generator to generate regenerative power. As a result, the actuator for the suspension unit on the inside of the turn is controlled regeneratively, and the rotational energy applied to the motor is converted into electricity.

[0007] In conventional suspension control methods, when the motors associated with the suspension devices located on the outside and inside of a turn are driven at the same rotation speed at the same time, as shown in Figure 9(a), the power generated by regenerative control can exceed the power consumed, as shown in Figure 9(b). In such cases, there is a problem that the inverter power supply voltage driving the motor can rise 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.

[0008] Furthermore, in order to adapt the electrical circuit to such an increase in inverter power supply voltage, components such as power cables and connectors must be enlarged for high voltages, which raises the problem of increased manufacturing costs.

[0009] The present invention has been made to solve the above-mentioned problems, and has as its object 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. [Means for solving the problem]

[0010] A suspension control device that solves the above problem is a suspension control device that controls a suspension device equipped with an actuator that drives the suspension device to extend and retract the entire length of the suspension device to enable the vehicle height to be raised and lowered, and is characterized by comprising: an operation state detection unit that detects the 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 and retracted; and an actuator control unit that controls the actuator at the target drive speed.

[0011] Furthermore, a suspension control method for solving the above-mentioned problems is a suspension control method for controlling 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, characterized in that it comprises an operation state detection step for detecting the vehicle operation state by the driver, a drive stroke calculation step for calculating a target drive stroke of the suspension device based on information acquired by the operation state detection step, a drive speed determination step for determining a target drive speed at which the entire length of the suspension device is extended and retracted, and an actuator control step for controlling the actuator at the target drive speed. [Effects of the Invention]

[0012] The suspension control device and suspension control method according to the present invention can stabilize the inverter power supply voltage by switching the actuator drive speed depending on the lifting and lowering direction of the suspension device, improve the rate of change in reverse roll during reverse roll control, enable control that follows the driver's operating speed, and reduce the cost of the components that make up the electrical circuit. [Brief explanation of the drawings]

[0013] [Figure 1] 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] 1 is a schematic diagram for explaining a suspension device according to an embodiment of the present invention; [Figure 3] FIG. 2 is a schematic diagram showing the configuration of a drive speed determination unit according to the embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram showing an example of a power supply connected to the actuator control device according to the embodiment of the present invention. [Figure 5] 3 is a flowchart showing a control example of the suspension control method according to the first embodiment of the present invention. [Figure 6] 10 is a flowchart showing a control example of a suspension control method according to a second embodiment of the present invention. [Figure 7] 10 is a flowchart showing a control example of a suspension control method according to a third embodiment of the present invention. [Figure 8] 1A and 1B are diagrams showing the effect of controlling a suspension device using the suspension control method of the present invention, where (a) is the drive stroke of the suspension device, (b) is the battery power consumption, and (c) is the inverter power supply voltage. [Figure 9] 1A and 1B are diagrams showing the effect of controlling a suspension device using a conventional suspension control method, where (a) is the drive stroke of the suspension device, (b) is the battery power consumption, and (c) is the inverter power supply voltage. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of a suspension control device according to the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention according to each claim, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0015] FIG. 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, FIG. 2 is a schematic diagram for explaining a suspension device according to an embodiment of the present invention, FIG. 3 is a schematic diagram showing the configuration of a drive speed determination unit according to an embodiment of the present invention, and FIG. 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.

[0016] 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 as to be movable up and down.

[0017] First, the suspension device 3 according to the present invention will be described.

[0018] 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 running stability. The suspension device 3 has a spring 4, a shock absorber 5, and an actuator 6.

[0019] The spring 4 is a compression coil spring that supports the weight of the vehicle 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 stiffness of the spring. The spring 4 expands and contracts in accordance with the unevenness of the road surface, keeping the wheel 2 from leaving the road surface.

[0020] The shock absorber 5 suppresses the movement of the oscillating spring 4. The shock absorber 5 is disposed inside the spring 4 and concentric with the spring 4. In this embodiment, the shock absorber 5 may have a structure that generates a damping force by hydraulic oil filled inside the shock absorber 5 and a piston that can move up and down within the hydraulic oil, for example.

[0021] The actuator 6 adjusts the height of the vehicle body from the ground by changing the distance between each wheel 2 and the vehicle body by expanding or contracting the entire length of the suspension device 3. The actuator 6 includes, for example, a drive device 7, a screw shaft 8, and a nut 9.

[0022] The driving device 7 has a motor 7 a controlled by a signal from an actuator control unit 40 (described later), and a gear device that transmits the power of the motor 7 a to the screw shaft 8.

[0023] The screw shaft 8 is arranged to connect with the axis of the shock absorber 5 and extend coaxially. As an example, a male thread such as a trapezoidal thread is formed on the outer surface of the screw shaft 8. The screw shaft 8 is supported by a rotation prevention mechanism so as to be non-rotatable but axially movable relative to the body of the actuator 6.

[0024] The nut 9 is disposed so as to surround the screw shaft 8. As an example, the nut 9 has an internal thread such as a trapezoidal thread formed on the inner surface thereof, which can be threadedly engaged 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, and rotates 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 as to be immovable in the vertical direction relative to the vehicle body.

[0025] The suspension device 3 configured in this manner can expand and contract its entire length by the operation described below.

[0026] When a signal from the actuator control unit 40 rotates the motor 7a provided in the drive unit 7, a gear device connected to the output shaft of the motor 7a rotates the nut 9. The screw shaft 8 that threads onto the nut 9 is supported non-rotatably by a rotation-preventing mechanism, and therefore moves up and down in the axial direction according to the rotation direction of the nut 9. The shock absorber 5 connected to the screw shaft 8 moves up and down together with the screw shaft 8, and the overall length of the suspension unit 3 is extended or contracted.

[0027] In the above description, the screw shaft 8 and the nut 9 are screwed together using a trapezoidal screw or the like, but the configuration of the screw shaft 8 and the nut 9 is not limited to this, and they may also be configured as a ball screw in which a number of balls are interposed between the screw groove of the screw shaft 8 and the screw groove of the nut 9 so as to be able to roll.

[0028] Furthermore, although the structure in which shock absorber 5 is connected to threaded shaft 8 and nut 9 is rotated to move threaded shaft 8 up and down, thereby expanding and contracting the overall length of suspension device 3, has been described, the structure for expanding and contracting the overall length of suspension device 3 is not limited to this. For example, a structure in which shock absorber 5 is connected to nut 9 and threaded shaft 8 is rotated by drive device 7 to move nut 9 up and down, thereby expanding and contracting the overall length of suspension device 3, may be used. In this case, nut 9 is supported by a rotation prevention mechanism so as to be non-rotatable about its axis but movable in the axial direction of threaded shaft 8, and threaded shaft 8 is supported via a bearing or the like so as to be rotatable about the axis of nut 9 but immovable in the vertical direction relative to the vehicle body.

[0029] Furthermore, the drive unit 7 has been described as having a structure in which it is equipped with a gear device and transmits the power of 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.

[0030] Next, a suspension control device that drives such a suspension device 3 will be described. As shown in Fig. 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 the respective suspension devices 3 installed on the front, rear, left and right sides of the vehicle 1. Fig. 1 shows only the components of the suspension control unit 100 corresponding to the suspension device 3 installed on the left front side, and the other components of the suspension control unit 100 are not shown.

[0031] 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 by the driver and 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.

[0032] The driving 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 below. The specific calculation method will be described later. In this specification, the appropriate amount of extension and contraction of the suspension device 3 calculated by the driving stroke calculation unit 20 is referred to as the target driving stroke amount. The driving stroke calculation unit 20 outputs the target driving stroke amount to the suspension control unit 100.

[0033] The motion state detection unit 60 detects the motion state of the vehicle 1 while it is running. The motion state detection unit 60 includes, for example, a vehicle speed sensor that detects the vehicle speed, an acceleration sensor that detects the acceleration in the front, rear, left and right directions of the vehicle body, a yaw rate sensor that detects the yaw rate generated in the vehicle body, etc. The motion state detection unit 60 outputs the detected information to the drive stroke calculation unit 20.

[0034] The suspension control unit 100 includes a drive speed determination unit 30, an actuator control unit 40, and a load measurement unit 50.

[0035] 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 a target drive speed. As shown in Figure 3, the drive speed determination unit 30 includes a drive direction determination unit 31, a descending rotation speed calculation unit 32, an ascending rotation speed calculation unit 33, and a selector switch 34.

[0036] The drive direction determination device 31 determines the extension / contraction direction, i.e., whether to operate the suspension device 3 in the contraction direction or the 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 device 3 to the changeover switch 34.

[0037] The lowering rotation speed calculation device 32 calculates the motor rotation speed for driving the motor 7a in order to shorten 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. A specific calculation method 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.

[0038] The increase rotation speed calculation device 33 calculates the motor rotation speed for driving the motor 7a 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. A specific calculation method 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.

[0039] The changeover 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 changeover 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.

[0040] The actuator control unit 40 rotates the motor 7a at a target rotation speed based on the signal input from the drive stroke calculation unit 20 and the signal input from the changeover switch 34 of the drive speed determination unit 30, and controls the suspension device 3 to expand or contract by the target drive stroke amount at the target drive speed.

[0041] 4, a power supply for driving the actuator 6 is connected to the actuator control unit 40. It is preferable to have multiple power supplies connected to the actuator control unit 40, such as a power supply obtained by stepping down the DC voltage from a driving battery 41 using a DC / DC converter 42, and a power supply from an auxiliary battery 43. By providing multiple power supplies in this way, it is possible to stably supply power to the actuator 6 even when a large amount of power is consumed temporarily.

[0042] 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 the auxiliary battery 43. 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.

[0043] The load measuring unit 50 detects the load acting on each suspension unit 3. The load is preferably detected by measuring the load acting on the actuator 6 using a sensor or the like. The method for detecting the load is not limited to this, and the load acting on the suspension unit 3 may be detected by various methods, such as a pressure sensor attached between the suspension unit 3 and the vehicle body. The load measuring unit 50 outputs the detected load to the drive stroke calculation unit 20.

[0044] Next, a method for controlling the elevation of the suspension device 3 using the suspension control device of the present invention will be described based on the following embodiment.

[0045] [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.

[0046] 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 driver relative to the steering wheel and the amount of depression of the driver on the accelerator pedal. In this embodiment, the process in step S1 is defined as an operation state detection process.

[0047] In step S2, the driving stroke calculation unit 20 calculates target driving stroke amounts for the suspension units 3 arranged on each of the left and right sides of the vehicle 1 based on the state of operation of the vehicle 1 by the driver detected in step S1. When the driver is steering the steering wheel and the vehicle 1 is turning, the target driving stroke amounts are 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, and the control of each suspension unit 3 becomes reverse roll control.

[0048] In addition, 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 angle of the steering wheel detected in step S1 as well as the depression amount of the accelerator pedal. In this embodiment, the process in step S2 is defined as a drive stroke calculation process.

[0049] 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 unit 3 is extended at a fast drive speed when raising the vehicle height, and that the suspension unit 3 is 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.

[0050] In step S4, the drive direction determination device 31 determines the extension / contraction direction of the suspension unit 3 based on the target drive stroke amount calculated in step 2. 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 unit 3 in order to raise the vehicle body. Also, the target drive stroke amount for the inside of the turn is determined to be drive in the direction that retracts the suspension unit 3 in order to lower the vehicle body. In this embodiment, the process in step S4 is referred to as a drive direction determination process.

[0051] In step S5, based on the result of the determination in step S4, the selector switch 34 is switched to determine either the lowering 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 a drive speed determination process.

[0052] 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, and operates the motor 7a. In this embodiment, the process in step 6 is defined as an actuator control process.

[0053] According to the suspension control method of 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. The suspension device 3 extends or contracts the target drive stroke amount at the target drive speed by driving the actuator 6.

[0054] [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 the second embodiment will be explained, which is different from the first embodiment.

[0055] 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 the same truck may have different total vehicle weight and weight balance depending on the load. When the weight balance of the 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, the ride comfort may deteriorate.

[0056] 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 can perform suitable vehicle control that does not cause discomfort to the driver by controlling the extension and contraction of each suspension device 3 by a target drive stroke amount at a target drive speed based on the operating state of the vehicle 1 by the driver as well as the front-rear and left-right weight balance of the vehicle 1. Note that steps that are the same as or similar to those in the first embodiment described above are given the same reference numerals and detailed explanations are omitted.

[0057] 6 is a flowchart showing a control example of the suspension control method according to the second embodiment. Hereinafter, this control method will be described using an example in which the vehicle 1 is turning.

[0058] The process of step S1 is the same as that in the first embodiment.

[0059] In step S11, the load measuring 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 a load distribution detection process.

[0060] In step S21, the drive stroke calculation unit 20 calculates the target drive stroke amount for each suspension device 3 based on the loads acting on the front, rear, left and right suspension devices 3 of the vehicle 1 detected in step S11, as well as the operating state of the vehicle 1 by the driver detected in step S1.

[0061] When the vehicle 1 is turning, a target drive stroke amount is calculated for each suspension device 3 so that the outer side of the turning vehicle body is raised and the inner side of the turning vehicle body is lowered.

[0062] Furthermore, the target drive stroke amount is calculated to provide an appropriate drive amount, such as increasing the drive amount for a suspension device 3 that is 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.

[0063] 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.

[0064] In this embodiment, it is preferable that the rotational speed of the raising motor is faster than the rotational speed of the lowering motor, i.e., it is preferable that the suspension unit 3 is extended at a high driving speed when raising the vehicle height, and that the suspension unit 3 is retracted at a low driving speed when lowering the vehicle height.

[0065] Furthermore, 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 provide an appropriate drive speed for the suspension device 3, such as by increasing the motor rotation speed to increase the drive speed for the suspension device 3 that is 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.

[0066] The processes from step S4 to step S6 are the same as those in the first embodiment.

[0067] According to the suspension control method of the second embodiment, the motor 7a receives a signal from the actuator control unit 40 and rotates at a target rotation speed according to the weight balance of the vehicle 1 to drive the actuator 6. The suspension device 3 extends or contracts the target drive stroke amount according to the target drive speed by driving the actuator 6.

[0068] [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. The suspension control method according to the third embodiment, which will be explained next, is a suspension control method that differs from the first and second embodiments.

[0069] Regarding the roll rotation occurring in the vehicle body, the reverse roll control as described above reduces the outward acceleration felt by the driver inside the vehicle, improving ride comfort. However, when the 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 deteriorate ride comfort.

[0070] 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 operation state of the vehicle 1 by the driver as well as the motion state, such as acceleration and deceleration, of the vehicle 1, thereby enabling 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 given the same reference numerals and detailed descriptions thereof will be omitted.

[0071] 7 is a flowchart showing a control example of the suspension control method according to the third embodiment. Hereinafter, this control method will be described taking as an example a state in which the vehicle 1 turns while accelerating or decelerating.

[0072] The process of step S1 is the same as that in the first embodiment.

[0073] In step S12, the motion state, such as acceleration or deceleration, of the traveling vehicle 1 is detected by the motion state detection unit 60. In this embodiment, the process in step S12 is defined as a motion state detection process.

[0074] In step S22, the drive stroke calculation unit 20 calculates the target drive stroke amount for each suspension device 3 based on the operation state of the vehicle 1 by the driver detected in step S1, as well as the motion state of the vehicle 1, such as acceleration and deceleration, detected in step S12.

[0075] When the vehicle 1 is turning while accelerating, the target drive stroke amount is calculated for each suspension device 3 so that the outer side of the turning vehicle body is raised and the inner side of the turning vehicle body is lowered.

[0076] Furthermore, the magnitudes of the target drive stroke amounts of the front suspension units 3 and the rear suspension units 3 are changed appropriately according to 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 amounts are calculated to provide appropriate drive amounts, such as by making the drive amounts of the rear suspension units 3 greater than those of 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.

[0077] In step S32, the descending rotation speed calculation device 32 and the ascending rotation speed calculation device 33 calculate the descending motor rotation speed and the ascending motor rotation speed based on the motion state of the traveling vehicle 1, such as acceleration / deceleration, detected in step S12.

[0078] In this embodiment, it is preferable that the rotational speed of the raising motor is faster than the rotational speed of the lowering motor, i.e., it is preferable that the suspension unit 3 is extended at a high driving speed when raising the vehicle height, and that the suspension unit 3 is retracted at a low driving speed when lowering the vehicle height.

[0079] Furthermore, depending on the motion state of the vehicle 1 during travel, such as acceleration and deceleration, the lowering motor rotation speed and the ascent motor rotation speed are calculated to provide an appropriate drive speed for the suspension device 3, such as by increasing the motor rotation speed to increase the drive speed for a suspension device 3 with a larger drive amount. In this embodiment, the process in step S32 is defined as a rotation speed calculation process, similar to the process in step S3.

[0080] The processes from step S4 to step S6 are the same as those in the first embodiment.

[0081] According to the suspension control method of the third embodiment, the motor 7a receives a signal from the actuator control unit 40 and rotates at a target rotation speed according to the motion state of the vehicle 1 while it is running, thereby driving the actuator 6. The suspension device 3 extends or contracts the target drive stroke amount according to the target drive speed by driving the actuator 6.

[0082] Next, the relationship between the inverter power supply voltage and the movement of the suspension device 3 that expands and contracts according to the suspension control method of the present invention will be described using an example in which the vehicle 1 is turning.

[0083] FIG. 8 is a diagram showing the effect of controlling a suspension device using the suspension control method of the present invention, where (a) is the drive stroke amount of the suspension device, (b) is the battery power consumption, and (c) is the inverter power supply voltage.

[0084] 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 earlier than the suspension unit 3 arranged on the side that lowers the vehicle body.

[0085] Furthermore, when the vehicle body is raised, power is consumed to drive the actuator 6, and the suspension device 3 is controlled to extend in overall length, while when the vehicle body is lowered, the suspension device 3 is controlled to shorten in overall length, and the motor 7a provided in the actuator 6 functions as a generator to generate regenerative power.

[0086] Therefore, when the vehicle 1 turns, the relationship between the power consumption and regenerative power of the suspension devices 3 provided on the outside and inside of the turn is such that, as shown in Figure 8(b), 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.

[0087] According to this relationship between power consumption and regenerative power, 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).

[0088] As described above, the suspension control method according to 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, since 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., and reduce manufacturing costs.

[0089] Although the suspension control method according to the present invention has been described in terms of the suspension control method according to the second embodiment and the suspension control method according to 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 in terms of being installed in a vehicle 1 in which a driver rides, such as a passenger car or truck, but are not limited to this. They may also be applied to vehicles such as delivery robots that are operated from the outside without a driver on board. It is clear from the claims that such modified or improved embodiments are also included within the technical scope of the present invention. [Explanation of symbols]

[0090] 1 vehicle, 3 suspension device, 6 actuator, 7a motor, 10 operation state detection unit, 11 steering 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

1. 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 thereof so as to enable raising and lowering of 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. 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. 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.

4. 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. 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;

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