Steering control system

Abstract

To provide a steering control device which can suppress lateral turning of a vehicle without interfering with steering of a steering wheel by a driver.SOLUTION: A steering control device 1 has a steering control device 1B. The steering control device 1B is configured to control a steering motor. The steering motor generates a torque to steer a steering wheel of a vehicle in which power transmission between a steering wheel and the steering motor is separated. When it is determined that there is a possibility that lateral turning of the vehicle occurs on the basis of the steering state of the steering wheel and the state of the vehicle, the steering control device 1B is configured to execute processing of making steering operation of the steering wheel dull on steering of the steering wheel.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a steering control device. [Background technology]

[0002] If a vehicle driver attempts to change the direction of travel by suddenly turning the steering wheel while the vehicle is in motion, there is a risk of the vehicle overturning. Overturning means the vehicle tips over sideways. Therefore, for example, the vehicle control device described in Patent Document 1 suppresses vehicle overturning by controlling the braking force of the wheels and the steering angle of the steering wheels when there is a risk of the vehicle overturning. The control of the steering angle is performed via an electric power steering device. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-24125 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The vehicle control device described in Patent Document 1 has the following concerns: When there is a risk of the vehicle overturning, the steering control performed by the electric power steering system to prevent overturning may interfere with the steering action of the steering wheels caused by the driver's steering wheel. [Means for solving the problem]

[0005] A steering control device capable of solving the above problems includes a steering control unit configured to control a steering motor that generates torque for steering the steering wheels of a vehicle, which are separated from the steering wheel in power transmission. The steering control unit is configured to perform a process to slow down the steering action of the steering wheels in response to steering the steering wheel when it is determined that there is a risk of the vehicle overturning, based on at least one of the steering state of the steering wheel and the state of the vehicle.

[0006] For example, if a driver attempts to change the direction of a vehicle by suddenly turning the steering wheel while the vehicle is in motion, there is a risk that the vehicle may overturn. According to the above configuration, when there is a risk of the vehicle overturning, the steering action of the steering wheels is slowed down in response to the steering wheel's input. Therefore, even when the steering wheel is turned sharply, the sharp turning of the steering wheels is suppressed. Consequently, the vehicle overturning can be suppressed. Furthermore, because the power transmission between the steering wheels and the steering wheel is separated, the vehicle overturning can be suppressed without interfering with the driver's steering of the steering wheel.

[0007] In the steering control device described above, the steering control unit may be configured to determine that there is a risk of the vehicle overturning when a predetermined rollover determination condition is met. In this case, the rollover determination condition may include the value of the current supplied to the steering motor being equal to or greater than a predetermined current threshold.

[0008] This configuration allows for the determination of whether a vehicle rollover is likely based on the value of the current supplied to the steering motor. The value of the steering motor's current reflects the force the steering wheels receive from the road surface, depending on the steering state of the steering wheel or the vehicle's behavior. Therefore, situations where a vehicle rollover is likely can be detected more quickly.

[0009] In the steering control device described above, the steering control unit may be configured to calculate a target angle of a shaft that rotates in conjunction with the steering operation of the steering wheel, according to the steering state of the steering wheel, and to perform feedback control to make the actual angle follow the calculated target angle. In this case, the steering control unit may be configured to limit the amount of change of the target angle per predetermined calculation period when it is determined that there is a risk of the vehicle overturning.

[0010] In this configuration, when there is a risk of the vehicle overturning, the amount of change in the target angle per predetermined calculation cycle is limited. As a result, the target angular velocity, which is the rate of change of the target angle over time, and consequently the actual angular velocity, which is the rate of change of the actual angle over time, become slower compared to when the amount of change in the target angle is not limited. In other words, the steering action of the steering wheels is slowed down in response to steering of the steering wheel. Therefore, even when the steering wheel is turned sharply, the sharp turning of the steering wheels is suppressed. Consequently, the overturning of the vehicle can be suppressed.

[0011] In the steering control device described above, the steering control unit may be configured to calculate a steering torque command value, which is a command value for the torque generated by the steering motor, by calculating a target angle of a shaft that rotates in conjunction with the steering operation of the steering wheel according to the steering state of the steering wheel, and performing feedback control to make the actual angle follow the calculated target angle. In this case, the steering control unit may be configured to limit the amount of change in the steering torque command value per predetermined calculation period when it is determined that there is a risk of the vehicle overturning.

[0012] In this configuration, when there is a risk of the vehicle overturning, the amount of change in the steering torque command value per defined calculation cycle is limited. As a result, the target angular velocity, which is the rate of change of the target angle over time, and consequently the actual angular velocity, which is the rate of change of the actual angle over time, become slower compared to when the amount of change in the steering torque command value is not limited. In other words, the steering action of the steering wheels is slowed down in response to steering wheel input. Therefore, even when the steering wheel is turned sharply, the sharp turning of the steering wheels is suppressed. Consequently, vehicle overturning can be suppressed.

[0013] In the steering control device described above, the steering control unit may be configured to calculate a target angle of a shaft that rotates in conjunction with the steering movement of the steering wheel, according to the steering state of the steering wheel, and to perform feedback control to make the actual angle follow the calculated target angle. In this case, the steering control unit may be configured to decrease the value of the feedback gain, which is a control parameter related to the responsiveness of the feedback control, when it is determined that there is a risk of the vehicle overturning.

[0014] In this configuration, when there is a risk of the vehicle rolling over, the value of the feedback gain is reduced. As a result, the responsiveness of the feedback control performed by the steering control unit decreases. In other words, the ability of the actual angle to follow the target angle decreases, so the steering action of the steering wheels becomes slower in response to steering wheel input. Therefore, for example, if the steering wheel is turned sharply, the sharp turning of the steering wheels is suppressed. As a result, vehicle rollover can be suppressed. [Effects of the Invention]

[0015] According to the present invention, it is possible to suppress the rollover of a vehicle without interfering with the steering wheel operation performed by the driver. [Brief explanation of the drawing]

[0016] [Figure 1]This is a diagram showing the configuration of a steering system on which the first embodiment of the steering control device is installed. [Figure 2] This is a block diagram of the reaction force control device and steering control device according to the first embodiment. [Figure 3] This is a block diagram of a pinion angle feedback control unit according to a second embodiment. [Modes for carrying out the invention]

[0017] The following describes a first embodiment of the steering control device. <Overall Structure> As shown in Figure 1, the steering control device 1 controls a steer-by-wire type steering system 2. The steering system 2 has a steering mechanism 3 and a steering mechanism 4. The steering mechanism 3 is the part of the mechanism that is steered by the driver via the steering wheel 5. The steering mechanism 4 is the part of the mechanism that steers the steering wheels 6 of the vehicle in response to the steering of the steering wheel 5. The steering control device 1 includes a reaction force control device 1A and a steering control device 1B. The reaction force control device 1A controls the steering mechanism 3. The reaction force control device 1A performs reaction force control. The steering control device 1B controls the steering mechanism 4. The steering control device 1B performs steering control. The steering control device 1B corresponds to the steering control unit.

[0018] The steering mechanism 3 includes a steering shaft 11, a reaction motor 12, and a reduction gear 13. The steering wheel 5 is rotatably connected to the steering shaft 11. The reaction motor 12 is the source of the steering reaction force applied to the steering shaft 11. The steering reaction force is a force in the opposite direction to the steering direction of the steering wheel 5. The reaction motor 12 is, for example, a three-phase brushless motor. The reduction gear 13 reduces the rotation of the reaction motor 12 and transmits the reduced rotation to the steering shaft 11.

[0019] The steering mechanism 4 includes a pinion shaft 21, a steering shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 also reciprocates the steering shaft 22. The pinion shaft 21 is positioned to intersect the steering shaft 22. The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22. Tie rods 25 are connected to both ends of the steering shaft 22 via rack ends 24, which are ball joints. The ends of the tie rods 25 are connected to knuckles (not shown) to which the steering wheels 6 are assembled.

[0020] The steering mechanism 4 comprises a steering motor 31, a transmission mechanism 32, and a conversion mechanism 33. The steering motor 31 is the source of the steering force applied to the steering shaft 22. The steering force is the force that causes the steering wheel 6 to turn. The steering motor 31 is, for example, a three-phase brushless motor. The transmission mechanism 32 is, for example, a belt drive mechanism. The transmission mechanism 32 transmits the rotation of the steering motor 31 to the conversion mechanism 33. The conversion mechanism 33 is, for example, a ball screw mechanism. The conversion mechanism 33 converts the rotation transmitted via the transmission mechanism 32 into axial motion of the steering shaft 22.

[0021] As the steering shaft 22 moves axially, the steering angle θ of the steering wheel 6 changes. w The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22, and therefore rotate in conjunction with the movement of the steering shaft 22. The pinion shaft 21 is a shaft or rotating body that rotates in conjunction with the steering action of the steering wheel 6.

[0022] The reaction force control device 1A controls the operation of the reaction force motor 12. The reaction force control device 1A has a processing circuit that includes one of the following three configurations A1, A2, and A3. A1. One or more processors that operate according to a computer program, which is software. A processor includes a CPU (central processing unit) and memory.

[0023] A2. One or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that perform at least some of the various processes. An ASIC includes a CPU and memory.

[0024] A3. Hardware circuit combining configurations A1 and A2. Memory is a medium readable by a computer that stores programs describing processes or instructions for the computer. In this embodiment, the computer is the CPU. Memory includes RAM (random access memory) and ROM (read-only memory). The CPU performs various controls by executing the programs stored in memory at predetermined calculation cycles.

[0025] The reaction force control device 1A acquires detection results from on-board sensors. The sensors include a vehicle speed sensor 41, a torque sensor 42, and a rotation angle sensor 43. The vehicle speed sensor 41 detects the vehicle speed V. The vehicle speed V is a state variable that reflects the vehicle's driving state. The torque sensor 42 is installed on the steering shaft 11. The torque sensor 42 is located on the steering wheel 5 side of the steering shaft 11 relative to the connection portion of the reduction gear 13. The torque sensor 42 detects the steering torque Th applied to the steering shaft 11. The steering torque Th is calculated based on the amount of twist of the torsion bar 42a installed on the steering shaft 11. The rotation angle sensor 43 is installed on the reaction motor 12. The rotation angle sensor 43 detects the rotation angle θ of the reaction motor 12. a It detects.

[0026] Steering torque Th, and the rotation angle θ of the reaction force motor 12. a For example, a positive value occurs when steering wheel 5 to the right, and a negative value occurs when steering wheel 5 to the left.

[0027] The reaction force control device 1A controls the operation of the reaction force motor 12 using the detection results of the vehicle speed sensor 41, the torque sensor 42, and the rotation angle sensor 43. The reaction force control device 1A controls the power supply to the reaction force motor 12 so that it generates a steering reaction force corresponding to the steering torque Th.

[0028] The steering control device 1B controls the operation of the steering motor 31. Similar to the reaction force control device 1A, the steering control device 1B has a processing circuit that includes one of the three configurations A1, A2, and A3 mentioned above.

[0029] The steering control device 1B acquires detection results from on-board sensors. The sensors include a rotation angle sensor 44 and a roll rate sensor 45. The rotation angle sensor 44 is provided on the steering motor 31. The rotation angle sensor 44 detects the rotation angle θ of the steering motor 31. b The rotation angle θ of the steering motor 31 is detected. b For example, this value is positive when the steering wheel 5 is turned to the right, and negative when the steering wheel 5 is turned to the left. The roll rate sensor 45 detects the roll rate RR. The roll rate RR is the rotational angular velocity around the roll axis. The roll axis is an axis that passes through the center of gravity of the vehicle and extends in the longitudinal direction of the vehicle.

[0030] The steering control device 1B controls the operation of the steering motor 31 using the detection result of the rotation angle sensor 44. The steering control device 1B controls the power supply to the steering motor 31 so that the steering wheels 6 are steered according to the steering state of the steering wheel 5.

[0031] <Configuration of reaction force control device 1A> Next, the configuration of the reaction force control device 1A will be described. As shown in Figure 2, the reaction force control device 1A includes a steering angle calculation unit 51, a reaction force torque command value calculation unit 52, and an energization control unit 53.

[0032] The steering angle calculation unit 51 calculates the rotation angle θ of the reaction motor 12 detected through the rotation angle sensor 43. aBased on this, the steering angle θ of the steering wheel 5 s is calculated. The reaction torque command value calculation unit 52 calculates a reaction torque command value T * based on the steering torque Th and the vehicle speed V. The reaction torque command value T * is the target value of the steering reaction force to be generated in the reaction motor 12. The steering reaction force is a torque in the direction opposite to the steering direction of the steering wheel 5. The larger the absolute value of the steering torque Th and the lower the vehicle speed V, the * larger the absolute value of the reaction torque command value T becomes.

[0033] The energization control unit 53 supplies power corresponding to the reaction torque command value T * to the reaction motor 12. Specifically, the energization control unit 53 calculates a current command value for the reaction motor 12 based on the reaction torque command value T * . The energization control unit 53 detects the value of the current I a generated in the power supply path through the current sensor 54 provided in the power supply path for the reaction motor 12. The value of the current I a is the value of the current supplied to the reaction motor 12. The energization control unit 53 obtains the deviation between the current command value and the value of the current I a and controls the power supply to the reaction motor 12 to eliminate the deviation. As a result, the reaction motor 12 generates a torque corresponding to the reaction torque command value T * .

[0034] <Configuration of the steering control device 1B> Next, the configuration of the steering control device 1B will be described. As shown in FIG. 2, the steering control device 1B includes a pinion angle calculation unit 61, a target pinion angle calculation unit 62, a pinion angle feedback control unit 63, and an energization control unit 64.

[0035] The pinion angle calculation unit 61 calculates the pinion angle θ b based on the rotation angle θ p of the steering motor 31 detected through the rotation angle sensor 43. The pinion angle θ pThis is the rotation angle of the pinion shaft 21, and corresponds to the actual angle of the pinion shaft 21. The steering motor 31 and the pinion shaft 21 are linked via the transmission mechanism 32, the conversion mechanism 33, and the steering shaft 22. Therefore, the rotation angle θ of the steering motor 31 b and pinion angle θ p There is a correlation between this and the rotation angle θ of the steering motor 31. b From the pinion angle θ p The pinion shaft 21 is meshed with the steering shaft 22. Therefore, the pinion angle θ can be determined. p There is also a correlation between this and the amount of movement of the steering shaft 22. That is, the pinion angle θ p The steering angle θ of the steering wheel 6. w This value reflects the situation.

[0036] The target pinion angle calculation unit 62 calculates the steering angle θ calculated by the steering angle calculation unit 51. s Based on the target pinion angle θ p * The target pinion angle θ is calculated. p * The pinion angle θ is p This is the target angle. The target pinion angle calculation unit 62 calculates the target pinion angle θ so that the steering angle ratio set according to the product specifications is realized. p * The rudder angle ratio is calculated as the steering angle θ. s The steering angle θ relative to this angle w It is the ratio of .

[0037] The target pinion angle calculation unit 62 sets the steering angle ratio according to the vehicle's driving conditions, such as the vehicle speed V, and sets the target pinion angle θ according to this set steering angle ratio. p * The target pinion angle calculation unit 62 calculates the steering angle θ as the vehicle speed V decreases. s The steering angle θ relative to this angle w The target pinion angle θ increases as much as possible. p * The target pinion angle calculation unit 62 calculates the steering angle θ as the vehicle speed V increases. s The steering angle θ relative to this anglew To make it smaller, the target pinion angle θ p * The target pinion angle calculation unit 62 calculates the steering angle θ in order to achieve the steering angle ratio set according to the vehicle's driving state. s The correction angle is calculated for the steering angle θ, and this calculated correction angle is used as the steering angle θ. s By adding this, the target pinion angle θ corresponds to the steering angle ratio. p * Perform the calculation.

[0038] Depending on the product specifications, the target pinion angle calculation unit 62 will calculate the target pinion angle θ such that the steering angle ratio is "1:1" regardless of the vehicle's driving conditions. p * You may also perform the calculation in this way.

[0039] The pinion angle feedback control unit 63 receives the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * , and the pinion angle θ calculated by the pinion angle calculation unit 61 p The pinion angle feedback control unit 63 takes in the pinion angle θ. p The target pinion angle θ p * To follow this, the pinion angle θ p Through feedback control, the steering torque command value T p * The steering torque command value T is calculated. p * This is a command value for the torque generated by the steering motor 31, and is the target value for the steering force.

[0040] The energization control unit 64 controls the steering torque command value T p * The power supply control unit 64 supplies power to the steering motor 31 according to the steering torque command value T. p * Based on this, the current command value for the steering motor 31 is calculated. The power supply control unit 64, through the current sensor 65 provided in the power supply path to the steering motor 31, receives the current I generated in the power supply path. bThe value of current I is detected. b The value of is the value of the current supplied to the steering motor 31. The energization control unit 64 controls the current command value and current I b The deviation from the value is calculated, and the power supply to the steering motor 31 is controlled to eliminate the deviation. As a result, the steering motor 31 controls the steering torque command value T p * It generates torque corresponding to the value.

[0041] <Regarding vehicle rollovers> Herein lies the following concern regarding the vehicle: If the driver of the vehicle attempts to change the direction of travel by suddenly turning the steering wheel 5 while the vehicle is in motion, there is a risk that the vehicle may roll over. Therefore, in this embodiment, in order to suppress the rolling over of the vehicle, the steering control device 1 is configured as follows.

[0042] <Rollover prevention treatment> As shown in Figure 2, the steering control device 1B has a differentiator 66 and a rollover determination unit 67.

[0043] The differentiator 66 receives the steering angle θ calculated by the steering angle calculation unit 51. s It takes in the steering angle θ. Differentiator 66 takes the steering angle θ s By differentiating, the steering angular velocity ω s Perform the calculation. The rollover determination unit 67 determines whether there is a risk of the vehicle rolling over. The rollover determination unit 67 uses the vehicle speed V detected through the vehicle speed sensor 41 and the current I detected through the current sensor 65 to determine whether there is a risk of the vehicle rolling over. b , the steering angular velocity ω calculated by the differentiator 66 s It takes in current I b This is the current supplied to the steering motor 31. The rollover detection unit 67 also takes in the roll rate RR detected through the roll rate sensor 45.

[0044] When the defined roll determination condition is satisfied, the roll determination unit 67 determines that there is a risk of the vehicle rolling over. The roll determination condition is a condition for determining whether there is a risk of the vehicle rolling over, and includes, for example, the following relational expressions (1) to (4). The roll determination unit 67 determines that there is a risk of the vehicle rolling over when all of the four relational expressions (1) to (4) are satisfied.

[0045] V≧V th …(1) However, "V th " is the vehicle speed threshold. The vehicle speed threshold V th is set based on the vehicle speed at which there is a risk of the vehicle rolling over. The higher the vehicle speed V, the higher the risk of the vehicle rolling over. Therefore, the vehicle speed threshold V th is set to a speed in the medium speed range or the high speed range. The medium speed range is, for example, a speed range of 40 km / h or more and less than 60 km / h. The high speed range is, for example, a speed range of 60 km / h or more.

[0046] I b ≧I bth …(2) However, "I bth " is the current threshold. The current threshold I bth is set based on, for example, the value of the current I b of the steering motor 31 when the steering wheel 5 is suddenly steered. The value of the current I b of the steering motor 31 also changes due to a difference occurring between the target pinion angle θ p * and the actual pinion angle θ p due to an external disturbance acting on the steered wheel 6 according to the road surface condition such as the road surface friction resistance. That is, the value of the current I b of the steering motor 31 reflects the actual road surface condition or the force received by the steered wheel 6 from the road surface. The current I b of the steering motor 31 is a state variable that reflects the steering state of the steering wheel 5 or the behavior of the vehicle.

[0047] ω s≧ω sth …(3) However, "ω sth " is the steering angular velocity threshold value. The angular velocity threshold value ω sth is the criterion for determining whether the steering wheel 5 is suddenly steered. The angular velocity threshold value ω sth is set based on, for example, the value of the steering angular velocity ω s when the steering wheel 5 is suddenly steered. The steering angular velocity ω s is a state variable that reflects the steering state of the steering wheel 5.

[0048] RR≧RR th …(4) However, "RR th " is the roll rate threshold value. The roll rate threshold value RR th is set based on the roll rate RR at which the vehicle is likely to roll over. The roll rate RR is a state variable that reflects the behavior of the vehicle.

[0049] When at least one of the four relational expressions (1) to (4) does not hold, the rollover determination unit 67 determines that there is no risk of the vehicle rolling over and sets the value of the determination flag F1 to "0". When all of the four relational expressions (1) to (4) hold, the rollover determination unit 67 determines that there is a risk of the vehicle rolling over and sets the value of the determination flag F1 to "1".

[0050] The target pinion angle calculation unit 62 takes in the value of the determination flag F1 set by the rollover determination unit 67. When the value of the determination flag F1 is "0", that is, when there is no risk of the vehicle rolling over, the target pinion angle θ s calculated according to the steering angle θ p * is set as the final target pinion angle θ p * to be used by the pinion angle feedback control unit 63.

[0051] The target pinion angle calculation unit 62 calculates the steering angle θ when the value of the judgment flag F1 is "1", that is, when there is a risk of the vehicle overturning. s The target pinion angle θ is calculated accordingly. p * A correction process is performed for the pinion angle θ used by the pinion angle feedback control unit 63. p * The target pinion angle calculation unit 62 calculates the steering angle θ s The target pinion angle θ is calculated accordingly. p * This process restricts the value to a minimum.

[0052] The target pinion angle calculation unit 62 performs a change amount guard process with respect to time. The change amount guard process is performed for a predetermined calculation period, for example, for one calculation period, the target pinion angle θ p * This process limits the amount of change to a predetermined limit value. The limit value is the target pinion angle θ per defined calculation period. p * This is a variable, and is a fixed value set based on, for example, computer simulations of vehicle rollovers or experiments using actual equipment.

[0053] The target pinion angle calculation unit 62 calculates the steering angle θ based on the limit value. s The target pinion angle θ is calculated accordingly. p * This limits the amount of change. Through this change amount guard function, the pinion angle feedback control unit 63 uses the final target pinion angle θ. p * The value of is the steering angle θ s The target pinion angle θ is calculated accordingly. p * It gradually increases toward the target pinion angle θ used by the pinion angle feedback control unit 63. Specifically, the final target pinion angle θ used by the pinion angle feedback control unit 63. p * The value of is the target pinion angle θ before the defined calculation cycle. p *Based on this, it increases by a limit value at each predetermined calculation cycle. In other words, the steering action of the steering wheel 6 becomes slower in response to the steering of the steering wheel 5. The target pinion angle θ after being limited based on the limit value. p * This is the corrected target pinion angle θ, which is adjusted to suppress vehicle rollover. p * That is the case.

[0054] The target pinion angle calculation unit 62 calculates the vehicle speed V and the current I of the steering motor 31. b The value of the steering angular velocity ω s Alternatively, the limit value may be changed depending on the roll rate RR. <Operation and Effects of the First Embodiment> The first embodiment provides the following functions and effects.

[0055] (1-1) If there is a risk of the vehicle overturning, the target pinion angle θ per predetermined calculation cycle, for example, per calculation cycle p * The amount of change is limited. Therefore, the target pinion angle θ p * Compared to the case where the amount of change is not limited, the steering angle θ with respect to the amount of steering wheel 5 is w The amount of change becomes smaller. In other words, even if the steering wheel 5 is turned more, the steering angle θ will change in proportion to the amount of steering wheel 5 is turned. w The target pinion angle θ does not change significantly. p * Compared to the case where the amount of change of the target pinion angle θ is not limited, p * The target pinion angular velocity, which is the rate of change over time, and consequently the pinion angle θ p The pinion angular velocity, which is the rate of change over time, slows down. In other words, even if the steering wheel 5 is turned sharply, the steering angle θ changes according to the steering speed of the steering wheel 5. wThe steering speed does not increase. Therefore, even if the steering wheel 5 is turned suddenly and sharply while the vehicle is in motion, the vehicle can be prevented from rolling over. In addition, because the power transmission between the steering wheels 6 and the steering wheel 5 is separated, the vehicle can be prevented from rolling over without interfering with the steering of the steering wheel 5 by the driver.

[0056] (1-2) The rollover determination unit 67 detects the current I through the current sensor 65. b Based on the value of current I, it is determined whether there is a risk of the vehicle overturning. b This is the current supplied to the steering motor 31. Current I of the steering motor 31 b The value reflects the actual road surface conditions. Also, the current I of the steering motor 31 b The value reflects the force that the steering wheels 6 receive from the road surface, depending on the steering state of the steering wheel 5 or the vehicle's behavior. Therefore, situations in which there is a risk of the vehicle rolling over can be detected more quickly.

[0057] <Second Embodiment> Next, a second embodiment of the steering control device will be described. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 and 2. Therefore, the same reference numerals are used for the same components and components as in the first embodiment, and their detailed descriptions are omitted.

[0058] This embodiment differs from the first embodiment in that it concerns the rollover suppression process, which is a process for suppressing vehicle rollover. In this embodiment, when there is a risk of vehicle rollover, the target pinion angle θ p * It is not the amount of change, but the steering torque command value T p * The amount of change is limited. The target pinion angle calculation unit 62 calculates the target pinion angle θ. p * You may choose not to perform the correction process for this.

[0059] As shown by the dashed line in Figure 1, the pinion angle feedback control unit 63 receives the value of the determination flag F1 set by the rollover determination unit 67. The pinion angle feedback control unit 63 determines the target pinion angle θ when the value of the determination flag F1 is "0", i.e., when there is no risk of the vehicle overturning. p * The steering torque command value T is calculated accordingly. p * The final steering torque command value T used by the energization control unit 64 is... p * Set it as follows.

[0060] The pinion angle feedback control unit 63, when the value of the determination flag F1 is "1", that is, when there is a risk of the vehicle overturning, determines the target pinion angle θ p * The steering torque command value T is calculated accordingly. p * A correction process is performed for the final steering torque command value T used by the energization control unit 64. p * The pinion angle feedback control unit 63 then sets the target pinion angle θ p * The steering torque command value T is calculated accordingly. p * This process restricts the value to a minimum.

[0061] The pinion angle feedback control unit 63 performs a change amount guard process with respect to time. The change amount guard process is performed on the steering torque command value T per predetermined calculation period, for example, per calculation period. p * This process limits the amount of change to a predetermined limit value. The limit value is the steering torque command value T per defined calculation cycle. p * This is a variable, and is a fixed value set based on, for example, computer simulations of vehicle rollovers or experiments using actual equipment.

[0062] The pinion angle feedback control unit 63 determines the target pinion angle θ based on the limit value. p * The steering torque command value T is calculated accordingly. p * This limits the amount of change. Through this change amount guard function, the final steering torque command value T used by the energization control unit 64 is limited. p * The target pinion angle θ is p * The steering torque command value T is calculated accordingly. p * It gradually increases toward. Specifically, the final steering torque command value T used by the energization control unit 64. p * This is the target pinion angle θ before a defined calculation cycle. p * Based on this, the value increases by a limit value at each predetermined calculation cycle. In other words, the steering action of the steering wheels 6 becomes slower in response to steering of the steering wheel 5. The steering torque command value T after being limited based on the limit value. p * This is the corrected steering torque command value T, which is adjusted to suppress vehicle rollover. p * That is the case.

[0063] The pinion angle feedback control unit 63 controls the vehicle speed V and the current I of the steering motor 31. b The value of the steering angular velocity ω s Alternatively, the limit value may be changed depending on the roll rate RR.

[0064] <Operation and Effects of the Second Embodiment> The second embodiment provides the following effects and benefits in addition to those described in section (1-2) of the first embodiment.

[0065] (2-1) If there is a risk of the vehicle overturning, the steering torque command value T per calculation cycle is set to a predetermined value. p * The amount of change is limited. Therefore, the steering torque command value T p *Compared to the case where the amount of change is not limited, the steering angle θ with respect to the amount of steering wheel 5 is w The amount of change becomes smaller. In other words, even if the steering wheel 5 is turned more, the steering angle θ will change in proportion to the amount of steering wheel 5 is turned. w The steering torque command value T does not change significantly. p * Compared to the case where the amount of change is not limited, the pinion angle θ p The pinion angular velocity, which is the rate of change over time, slows down. In other words, even if the steering wheel 5 is turned sharply, the steering angle θ changes according to the steering speed of the steering wheel 5. w The steering speed does not increase. Therefore, even if the steering wheel 5 is turned suddenly and sharply while the vehicle is in motion, the vehicle can be prevented from rolling over. In addition, because the power transmission between the steering wheels 6 and the steering wheel 5 is separated, the vehicle can be prevented from rolling over without interfering with the steering of the steering wheel 5 by the driver.

[0066] <Third Embodiment> Next, a second embodiment of the steering control device will be described. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 and 2. Therefore, the same reference numerals are used for the same components and components as in the first embodiment, and their detailed descriptions are omitted.

[0067] This embodiment differs from the first embodiment in that it concerns the rollover suppression process, which is a process for suppressing vehicle rollover. In this embodiment, when there is a risk of vehicle rollover, the target pinion angle θ p * Instead of changing the amount of change, the value of the feedback gain of the pinion angle feedback control unit 63 is changed. The target pinion angle calculation unit 62 calculates the target pinion angle θ p * You may choose not to perform the correction process for this.

[0068] As shown in Figure 3, the pinion angle feedback control unit 63 includes a subtractor 63A, a proportional control unit 63B, an integral control unit 63C, a differential control unit 63D, a damping control unit 63E, and an arithmetic unit 63F.

[0069] The subtractor 63A subtracts the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * The pinion angle θ is calculated by the pinion angle calculation unit 61. p It takes in the following. The subtractor 63A calculates the angular deviation Δθ. p The angle deviation Δθ is calculated. p The target pinion angle θ is p * and pinion angle θ p That is the difference.

[0070] The proportional control unit 63B calculates the angular deviation Δθ calculated by the subtractor 63A. p By performing a proportional operation on the angular deviation Δθ, p The first torque command value T is proportional to the value of the first torque command T. p1 The proportional control unit 63B calculates the proportional gain, for example, according to the vehicle's driving state. The vehicle's driving state is reflected, for example, in the vehicle speed V. The proportional control unit 63B calculates the angular deviation Δθ p By multiplying by a proportional gain, the first torque command value T is obtained. p1 Perform the calculation.

[0071] The integral control unit 63C calculates the angular deviation Δθ calculated by the subtractor 63A. p By performing an integral operation on the angular deviation Δθ, p The second torque command value T is proportional to the integral value of p2 The integral control unit 63C calculates the integral gain according to the vehicle's driving state, for example. The vehicle's driving state is reflected in the vehicle speed V, for example. The integral control unit 63C calculates the angular deviation Δθ p By integrating with respect to time and multiplying the integral value by the integral gain, the second torque command value T is obtained. p2 Perform the calculation.

[0072] The differential control unit 63D calculates the angular deviation Δθ calculated by the subtractor 63A. p By performing a differential operation on the angular deviation Δθ, p The third torque command value T is proportional to the derivative of p3 The differential control unit 63D calculates the differential gain, for example, according to the vehicle's driving state. The vehicle's driving state is reflected, for example, in the vehicle speed V. The differential control unit 63D calculates the angular deviation Δθ p By differentiating with respect to time and multiplying the derivative by the differential gain, the third torque command value T is obtained. p3 Perform the calculation.

[0073] Incidentally, the differential control unit 63D performs a differential operation on the angular velocity deviation, which is the difference between the target pinion angular velocity and the pinion angular velocity, thereby generating a third torque command value T that is proportional to the derivative of the angular velocity deviation. p3 The target pinion angular velocity is calculated by the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * It is obtained by differentiating. The pinion angular velocity is the pinion angle θ calculated by the pinion angle calculation unit 61. p It can be obtained by differentiating it.

[0074] The damping control unit 63E calculates the angular deviation Δθ calculated by the subtractor 63A. p Based on this, the fourth torque command value T p4 The fourth torque command value T is calculated. p4 This is a compensation value for compensating for the viscosity of the steering mechanism 4, and is a compensation value calculated to suppress the steering angular velocity of the steering wheel 6. The damping control unit 63E calculates the damping gain, for example, according to the vehicle's driving state. The vehicle's driving state is reflected, for example, in the vehicle speed V. The damping control unit 63E calculates the angular deviation Δθ, for example, by the subtractor 63A. p By multiplying this by the damping gain, the fourth torque command value T is obtained. p4 Perform the calculation.

[0075] Incidentally, the damping control unit 63E sets a fourth torque command value T based on the pinion angular velocity or target pinion angular velocity. p4 The calculation may be performed in such a way. The pinion angular velocity is calculated by the pinion angle θ calculated by the pinion angle calculation unit 61. p It is obtained by differentiating the following. The target pinion angular velocity is the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * It can be obtained by differentiating it.

[0076] The arithmetic unit 63F calculates the first torque command value T calculated by the proportional control unit 63B. p1 The second torque command value T is calculated by the integral control unit 63C. p2 The third torque command value T is calculated by the differential control unit 63D. p3 Then, the fourth torque command value T calculated by the damping control unit 63E p4 The arithmetic unit 63F takes in the first torque command value T p1 And the second torque command value T p2 And the third torque command value T p3 The two values ​​are added together, and the fourth torque command value T is calculated from the added value. p4 By subtracting this, the steering torque command value T p * Perform the calculation.

[0077] The pinion angle feedback control unit 63 sets the values ​​of the proportional gain, integral gain, differential gain, and damping gain according to the value of the determination flag F1 set by the rollover determination unit 67. Each gain is a feedback gain, which is a control parameter relating to the responsiveness of the feedback control performed by the pinion angle feedback control unit 63.

[0078] The proportional control unit 63B receives the value of the judgment flag F1. When the value of the judgment flag F1 is "0", that is, when there is no risk of the vehicle overturning, the proportional control unit 63B sets the proportional gain value to its initial value. The initial value is the proportional gain value calculated by the proportional control unit 63B according to the vehicle's driving state.

[0079] The proportional control unit 63B sets the proportional gain to a value smaller than the initial value when the value of the judgment flag F1 is "1", that is, when there is a risk of the vehicle overturning. The amount of reduction in the proportional gain is determined by the product specifications, etc.

[0080] The proportional control unit 63B calculates a first rollover suppression setting value by multiplying the initial value of the proportional gain by a first adjustment gain when the value of the judgment flag F1 is "1". The first adjustment gain is a value less than "1", for example, a value within the range of "0.1 to 0.9". The proportional control unit 63B receives the vehicle speed V and the current I of the steering motor 31. b The value of the steering angular velocity ω s Alternatively, the value of the first adjustment gain may be changed according to the roll rate RR.

[0081] The first rollover suppression setting value is smaller than the initial value of the proportional gain. When the value of the judgment flag F1 is "1", the proportional control unit 63B switches the value of the proportional gain from the initial value to the first rollover suppression setting value. The difference between the first rollover suppression setting value and the initial value is the decrease in proportional gain.

[0082] The integral control unit 63C receives the value of the judgment flag F1. When the value of the judgment flag F1 is "0", that is, when there is no risk of the vehicle overturning, the integral control unit 63C sets the value of the integral gain to its initial value. The initial value is the value of the integral gain calculated by the integral control unit 63C according to the vehicle's driving state.

[0083] The integral control unit 63C sets the integral gain to a value smaller than the initial value when the value of the judgment flag F1 is "1", that is, when there is a risk of the vehicle overturning. The amount of reduction in the integral gain is determined by the product specifications, etc.

[0084] The integral control unit 63C calculates a second rollover suppression setting value by multiplying the initial value of the integral gain by a second adjustment gain when the value of the judgment flag F1 is "1". The second adjustment gain is a value less than "1", for example, a value within the range of "0.1 to 0.9". The integral control unit 63C receives the vehicle speed V and the current I of the steering motor 31. b The value of the steering angular velocity ω s Alternatively, the value of the second adjustment gain may be changed according to the roll rate RR.

[0085] The second rollover suppression setting value is smaller than the initial value of the integral gain. When the value of the judgment flag F1 is "1", the integral control unit 63C switches the value of the integral gain from the initial value to the second rollover suppression setting value. The difference between the second rollover suppression setting value and the initial value is the amount of decrease in the integral gain.

[0086] The differential control unit 63D receives the value of the judgment flag F1. When the value of the judgment flag F1 is "0", that is, when there is no risk of the vehicle overturning, the differential control unit 63D sets the value of the differential gain to its initial value. The initial value is the value of the differential gain calculated by the differential control unit 63D according to the vehicle's driving state.

[0087] The differential control unit 63D sets the differential gain to a value smaller than its initial value when the value of the judgment flag F1 is "1", that is, when there is a risk of the vehicle overturning. The amount of reduction in the differential gain is determined by the product specifications, etc.

[0088] When the value of the determination flag F1 is "1", the differential control unit 63D calculates a third rollover suppression setting value by multiplying the initial value of the differential gain by a third adjustment gain. The third adjustment gain is a value less than "1", for example, a value within the range of "0.1 to 0.9". The differential control unit 63D receives the vehicle speed V and the current I of the steering motor 31. b The value of the steering angular velocity ω s Alternatively, the value of the third adjustment gain may be changed according to the roll rate RR.

[0089] The third rollover suppression setting value is smaller than the initial value of the differential gain. When the value of the judgment flag F1 is "1", the differential control unit 63D switches the value of the differential gain from the initial value to the third rollover suppression setting value. The difference between the third rollover suppression setting value and the initial value is the decrease in the differential gain.

[0090] The damping control unit 63E receives the value of the judgment flag F1. When the value of the judgment flag F1 is "0", that is, when there is no risk of the vehicle overturning, the damping control unit 63E sets the damping gain value to its initial value. The initial value is the damping gain value calculated by the damping control unit 63E according to the vehicle's driving state.

[0091] The damping control unit 63E sets the damping gain value to a value smaller than the initial value when the value of the judgment flag F1 is "1", that is, when there is a risk of the vehicle overturning. The amount of reduction in the damping gain value is determined by the product specifications, etc.

[0092] When the value of the determination flag F1 is "1", the damping control unit 63E calculates a fourth rollover suppression setting value by multiplying the initial value of the damping gain by a fourth adjustment gain. The fourth adjustment gain is a value less than "1", for example, a value within the range of "0.1 to 0.9". The damping control unit 63E receives the vehicle speed V and the current I of the steering motor 31. b The value of the steering angular velocity ω s Alternatively, the value of the fourth adjustment gain may be changed according to the roll rate RR.

[0093] The fourth rollover suppression setting value is smaller than the initial value of the damping gain. When the value of the determination flag F1 is "1", the damping control unit 63E switches the value of the damping gain from the initial value to the fourth rollover suppression setting value. The difference between the fourth rollover suppression setting value and the initial value is the amount of decrease in damping gain.

[0094] Therefore, when there is a risk of the vehicle overturning, the responsiveness of the feedback control performed by the pinion angle feedback control unit 63 decreases in proportion to the decrease in the values ​​of the proportional gain, integral gain, differential gain, and damping gain. In other words, when there is a risk of the vehicle overturning, the servo stiffness becomes lower by decreasing the value of each gain. As a result, the steering action of the steering wheels 6 becomes sluggish in response to the steering of the steering wheel 5.

[0095] <Operation and Effects of the Third Embodiment> The third embodiment provides the following effects and benefits in addition to those described in section (1-2) of the first embodiment.

[0096] (3-1) If there is a risk of the vehicle overturning, the value of the feedback gain of the pinion angle feedback control unit 63 is reduced. The feedback gain includes proportional gain, integral gain, differential gain, and damping gain. As a result, the responsiveness of the feedback control performed by the pinion angle feedback control unit 63 decreases. That is, the target pinion angle θ p * The pinion angle θ relative to this angle p The responsiveness of the steering wheel is reduced. Therefore, the rapid steering of the steering wheels 6 in response to sudden steering of the steering wheel 5 is suppressed. As a result, the rollover of the vehicle can be suppressed. In addition, since the power transmission between the steering wheels 6 and the steering wheel 5 is separated, the rollover of the vehicle can be suppressed without interference with the steering of the steering wheel 5 by the driver.

[0097] <Other Embodiments> Furthermore, each embodiment may be implemented with the following modifications. As shown in Figure 1, a ground load sensor 46 may be provided on the vehicle. The ground load sensor 46 is provided, for example, on the hub unit bearing incorporated into each wheel of the vehicle. The wheels include the steering wheels 6. The ground load sensor 46 detects the ground load F z It detects the ground load F. zThis is the force acting vertically on each wheel of the vehicle from the road surface. If the vehicle is equipped with a ground load sensor 46, the steering control device 1B may take in the ground load Fz detected through the ground load sensor 46 instead of the roll rate RR detected through the roll rate sensor 45. In this case, the rollover determination condition includes the following relation (5) instead of the relation (4) above. The rollover determination unit 67 determines that there is a risk of the vehicle rolling over when all four relation (1) to (3) and (5) are true.

[0098] F z ≥F zth …(5) However, "F zth This is the ground load threshold. Ground load threshold F zth The ground contact load F is considered to be the point at which there is a risk of the vehicle overturning. z It is set based on the following. If there is a risk of the vehicle overturning, the ground contact load F of either the left or right wheel relative to the direction of travel of the vehicle. z The ground load F of either the left or right wheel increases. z The ground load F decreases. z This is a state variable that reflects the state or behavior of the vehicle.

[0099] • In determining whether a vehicle is overturning, it is not necessarily required that all of the relational expressions (1) to (4), or relational expressions (1) to (3) and (5), be true. The overturning determination unit 67 may determine, for example, that there is a risk of the vehicle overturning when relational expressions (1) and (3), relational expressions (1) and (4), or relational expressions (1) and (5) are true.

[0100] The vehicle speed sensor 41 may be a wheel speed sensor. The steering control device 1 calculates the vehicle speed V based on the wheel speed detected through the wheel speed sensor and performs various controls using the calculated vehicle speed V.

[0101] - A configuration may be adopted in which the damping control unit 63E is omitted as the pinion angle feedback control unit 63. In this case, the calculator 63F receives the first torque command value T calculated by the proportional control unit 63B. p1 The second torque command value T is calculated by the integral control unit 63C. p2 The third torque command value T is calculated by the differential control unit 63D. p3 By adding these together, the steering torque command value T p * Perform the calculation. [Explanation of symbols]

[0102] 1... Steering control device 1B... Steering control device (steering control unit) 5… Steering wheel 6… Steering wheel 21…Pinion shaft 31... Steering motor

Claims

1. A steering control device having a steering control unit configured to control a steering motor that generates torque for steering the steering wheels of a vehicle, with power transmission separated from the steering wheel, The steering control unit is configured to perform a process to slow down the steering action of the steering wheels when it is determined, based on at least one of the steering state of the steering wheel and the state of the vehicle, that there is a risk of the vehicle overturning.

2. The steering control unit is configured to determine that there is a risk of the vehicle overturning when the predetermined overturning determination conditions are met. The steering control device according to claim 1, wherein the rollover determination condition includes that the value of the current supplied to the steering motor is equal to or greater than a predetermined current threshold.

3. The steering control unit is configured to calculate a target angle of the shaft that rotates in conjunction with the steering movement of the steering wheel, according to the steering state of the steering wheel, and to perform feedback control to make the actual angle follow the calculated target angle. The steering control device according to claim 1 or claim 2, wherein the steering control unit is configured to limit the amount of change in the target angle per predetermined calculation period when it is determined that there is a risk of the vehicle overturning.

4. The steering control unit is configured to calculate a steering torque command value, which is a command value for the torque generated by the steering motor, by calculating a target angle of the shaft that rotates in conjunction with the steering operation of the steering wheel according to the steering state of the steering wheel, and by performing feedback control to make the actual angle follow the calculated target angle. The steering control device according to claim 1 or 2, wherein the steering control unit is configured to limit the amount of change in the steering torque command value per predetermined calculation period when it is determined that there is a risk of the vehicle overturning.

5. The steering control unit is configured to calculate a target angle of the shaft that rotates in conjunction with the steering movement of the steering wheel, according to the steering state of the steering wheel, and to perform feedback control to make the actual angle follow the calculated target angle. The steering control device according to claim 1 or 2, wherein the steering control unit is configured to reduce the value of the feedback gain, which is a control parameter relating to the responsiveness of the feedback control, when it is determined that there is a risk of the vehicle overturning.

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