JP5026036B2 - Rollover control device for vehicle - Google Patents

Description

  According to the present invention, when a rollover sign is detected, the assist torque generated by driving an assist actuator that assists the steering torque is limited, and the rollover of the vehicle is avoided by relatively increasing the steering torque. The present invention relates to a control device.

  Generally, when a running vehicle turns sharply or enters a corner at an overspeed, a large lateral acceleration (centrifugal force) acts on the vehicle, and the vehicle tilts outward in the turning direction. At that time, if the lateral acceleration is excessive and it becomes difficult to return the vehicle tilt posture, rollover (rollover) is caused.

  For this reason, various techniques for avoiding rollover during turning have been proposed. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2005-104340) discloses a technique for avoiding rollover by using a braking system installed in a vehicle. That is, in this document, (1) when the vehicle speed, lateral acceleration, and roll rate during turning are equal to or higher than a reference value, control is performed to apply a braking force corresponding to the roll rate to the turning outer wheel to avoid rollover ( Roll rate control).

  (2) When the vehicle speed and lateral acceleration at the turn are equal to or higher than other reference values, control is performed to apply a braking force corresponding to the lateral acceleration to the turning outer wheel to avoid rollover (lateral acceleration control).

(3) When both roll rate control and lateral acceleration control are activated, a control amount obtained by weighting and adding each control amount calculated in roll rate control and lateral acceleration control is obtained, and rollover is avoided with the control amount. Control.
JP 2005-104340 A

  However, the technique disclosed in the above publication cannot be applied to a vehicle that is not equipped with a braking system.

  Further, when braking force is applied to the turning outer wheel during turning, there is a problem that the tire grip force of the turning outer wheel is reduced and the vehicle behavior is likely to become unstable.

  In view of the above circumstances, the present invention can be applied to a vehicle that is not equipped with a braking system, and also ensures a tire grip force when turning and avoids rollover in a state where the vehicle behavior is stabilized. An object of the present invention is to provide a vehicle rollover control device.

In order to achieve the above object, a rollover control device for a vehicle according to the present invention is based on at least a steering torque based on an assist actuator for assisting steering torque related to a steering wheel and a basic value of assist torque generated by driving the assist actuator. A basic assist torque setting means for setting a rollover, a rollover determination means for determining whether a rollover sign is detected based on a physical quantity indicating a lateral behavior acting on a vehicle and a physical quantity indicating a roll direction behavior, When a rollover sign is detected by the rollover determination means, an acceleration of the physical quantity indicating the roll direction behavior is obtained based on the physical quantity indicating the roll direction behavior, a rollover condition is determined based on the acceleration, and the rollover condition is determined. If over condition is satisfied, the roll direction behavior An assist correction coefficient setting means for setting an assist correction coefficient for correcting the assist torque in a direction to decrease the assist torque based on the physical quantity, and a target for setting the target value of the assist torque by correcting the basic value with the assist correction coefficient Assist torque setting means.

  According to the present invention, when a rollover sign is detected, the steering torque is increased and the steering reaction force is increased to avoid the rollover. Can be applied, and not only can excellent economic efficiency be obtained, but also can be incorporated into existing systems, so that high versatility can be obtained.

  In addition, compared to the conventional technique of avoiding rollover by braking the wheel, it is possible to secure a tire grip force during turning and avoid rollover in a state where the vehicle behavior is stabilized.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 shows a schematic diagram of a vehicle equipped with a rollover control device. Reference numeral 1 in FIG. 1 denotes an electric power steering device. A steering shaft 2 of the electric power steering device 1 is rotatably supported by a vehicle body frame (not shown) via a steering column 3, and one end of the steering shaft 2 is a driver's seat. The other end is extended to the engine room side. A steering wheel 4 is fixed to the end of the steering shaft 2 on the driver's seat side, and a pinion shaft 5 is connected to the end extending to the engine room side.

  A steering gear box 6 extending in the vehicle width direction is disposed in the engine room, and a rack shaft 8 is inserted into and supported by the steering gear box 6 so as to be reciprocally movable. A rack (not shown) formed on the rack shaft 8 is engaged with a pinion formed on the pinion shaft 5 to form a rack and pinion type steering gear mechanism. The left and right ends of the rack shaft 8 protrude from the end of the steering gear box 6, and a front knuckle 10 is connected to the end via a tie rod 9. The front knuckle 10 rotatably supports left and right wheels 11L and 11R as steering wheels, and is supported by a vehicle body frame via a king pin (not shown) so as to be steerable. Therefore, when the steering wheel 4 is operated and the steering shaft 2 and the pinion shaft 5 are rotated, the rack shaft 8 is moved in the left-right direction by the rotation of the pinion shaft 5, and the front knuckle 10 is moved by the movement to the king pin (not shown). ) And the left and right wheels 11L and 11R are steered in the left-right direction.

  An electric motor 13 as an assist actuator is connected to the pinion shaft 5 via an assist transmission mechanism 12, and the steering torque related to the steering wheel 4 is assisted by the electric motor 13. Further, a steering torque sensor 14 is connected to the steering shaft 2, and the steering torque applied to the steering wheel 4 is detected by the steering torque sensor 14.

  On the other hand, reference numeral 21 denotes a motor control unit (M_ECU) that controls the drive of the electric motor 13. On the input side of the M_ECU 21, a steering torque sensor 14 that detects the steering torque Tq applied to the steering wheel 4, a vehicle speed sensor 15 that detects the vehicle speed Vsp, and a lateral acceleration Gy that acts on the vehicle body as a physical quantity indicating lateral behavior. Are connected to a lateral acceleration sensor 16 for detecting the roll rate and a roll rate sensor 17 for detecting a roll rate φv acting on the vehicle body. In the present embodiment, the lateral acceleration Gy and the roll rate φv generated during the left turn are expressed as positive (+) values, and the lateral acceleration Gy and the roll rate φv generated during the right turn are expressed as negative (−) values.

  As shown in FIG. 2, the M_ECU 21 includes a motor control unit 22, a motor drive signal generation circuit 23, a motor drive circuit 24, and a current detection unit 25.

  The motor control unit 22 is mainly composed of a microcomputer, and has a nonvolatile storage means such as a well-known CPU, ROM, RAM, and EEPROM. This motor control unit 22 is in accordance with a program stored in the ROM, a rollover determination unit 22a as a rollover determination unit, an assist coefficient calculation unit 22b, a target assist current calculation unit 22c, and a feedback (F / B) control calculation unit. Each function of 22d is executed.

  The rollover determination unit 22a first reads the vehicle speed Vsp detected by the vehicle speed sensor 15. When the vehicle speed Vsp is equal to or higher than the set vehicle speed Va (for example, 40 [Km / h]), the lateral acceleration Gy detected by the lateral acceleration sensor 16 and the roll rate φv detected by the roll rate sensor 17 are read and this lateral acceleration Gy is read. And roll rate φv, it is determined whether or not there is a sign of occurrence of rollover. When the rollover determination unit 22a determines that there is a sign of the occurrence of rollover, the assist coefficient calculation unit 22b sets an assist correction coefficient iq for correcting a basic assist current Ip described later by map search based on the roll rate φv.

  The target assist current calculation unit 22c sets a target assist current P to be supplied to the electric motor 13. The map search is based on the steering torque Tq detected by the steering torque sensor 14 and the vehicle speed Vsp detected by the vehicle speed sensor 15. Thus, the basic assist current Ip that is the basic value of the assist torque is set, the basic assist current Ip is corrected by the assist correction coefficient iq, and the target assist that is the target value of the current (assist torque) supplied to the electric motor 13 is set. The current P is set.

  The F / B control calculation unit 22d calculates a difference ΔP between the target assist current P set by the target assist current calculation unit 22c and the motor current Is detected by the current detection unit 25, and based on the difference ΔP, this difference A control signal (feedback control signal) D such that ΔP converges to 0 is generated by a known proportional-integral control calculation or the like.

  The motor drive signal generation circuit 23 generates a motor drive signal corresponding to the control signal D output from the F / B control calculation unit 22d. The motor drive signal includes, for example, a pulse width modulation signal (PWM signal) having a duty ratio corresponding to the control signal D.

  The motor drive circuit 24 outputs a voltage corresponding to the motor drive signal to the electric motor 13. The current detection unit 25 detects a current (motor current) Is supplied to the electric motor 13 and outputs it to the F / B control calculation unit 22d.

  Specifically, the process in the rollover determination unit 22a described above is performed according to a rollover determination routine shown in FIG.

  In this routine, first, the vehicle speed Vsp detected by the vehicle speed sensor 15 is read in step S1, and it is checked in step S2 whether the vehicle speed Vsp is equal to or higher than a set vehicle speed Va (for example, 40 [Km / h]). When the vehicle speed Vsp does not reach the set vehicle speed Va (Vsp <Va), it is determined that there is no possibility of rollover, and the process jumps to step S12.

  When the vehicle speed Vsp is equal to or higher than the set vehicle speed Va (Vsp ≧ Va), it is determined that there is a possibility of rollover when an unreasonable steering operation is performed, and the process proceeds to step S3, where the lateral acceleration Gy and the roll rate φv And read.

  Next, in steps S4 and S5, it is determined whether or not there is a sign of rollover. That is, in step S4, the absolute value | Gy | of the lateral acceleration Gy is compared with a preset threshold value α. The threshold value α is a value that increases the possibility of a rollover after a predetermined time has elapsed after exceeding the threshold value α, and is obtained in advance based on experiments or the like.

  If the absolute value | Gy | of the lateral acceleration Gy exceeds the threshold value α (| Gy | ≧ α), the process proceeds to step S5. On the other hand, if the absolute value | Gy | of the lateral acceleration Gy is less than the threshold value α (| Gy | <α), there is no possibility of rollover even after a predetermined time has elapsed, and the process jumps to step S12.

  In step S5, the absolute value | φv | of the roll rate φv is compared with the threshold value β. Similarly to the threshold value α described above, this threshold value β is a value that increases the possibility of rollover after a predetermined time has elapsed after exceeding the threshold value β. ing.

  If the absolute value | φv | of the roll rate φv exceeds the threshold value β (| φv | ≧ β), the process proceeds to step S6. On the other hand, if the absolute value | φv | of the roll rate φv is less than the threshold value β (| φv | <β), there is no possibility of rollover even after a predetermined time has elapsed, and the process jumps to step S12.

  If it is determined in steps S4 and S5 that | Gy | ≧ α and | φv | ≧ β, the occurrence of rollover is predicted after a predetermined time has elapsed. Whether or not there is a possibility of rollover is examined in detail based on the roll angular acceleration φa indicating the change.

  First, in step S6, the roll rate φv is time-differentiated to calculate the roll angular acceleration φa, and in step S7, the absolute value | φa | of the roll angular acceleration φa is compared with a preset rollover determination threshold τ. To do. The rollover determination threshold value τ is a value that increases the probability that a rollover will occur after a predetermined time has elapsed, and is set in advance by experiments. The predetermined time is longer than a delay value Z described later.

  If the absolute value | φa | of the roll angular acceleration φa exceeds the rollover determination threshold value τ (| φa | ≧ τ), the process proceeds to step S8. If the absolute value | φa | of the roll angular acceleration φa is less than the rollover determination threshold τ (| φa | <τ), it is determined that the rollover condition is not satisfied, that is, there is no rollover, and the process jumps to step S12. To do.

  In step S8, the count value C of the delay timer is incremented (C ← C + 1). In step S9, the count value C of the delay timer is compared with a preset delay value Z. This delay value Z is set to about 1 to 2 [sec] for checking whether or not the state where the rollover condition is satisfied continues for a set time.

  When C <Z, the process proceeds to step S10, the current roll rate φv is read, and then the process returns to step S6. The roll rate φv is time-differentiated to calculate the roll angular acceleration φa.

  On the other hand, when C ≧ Z, it is determined that the rollover condition is satisfied, that is, the rollover sign has been detected, the process proceeds to step S11, the rollover flag Fro is set (Fro ← 1), and the routine is exited. If it is determined that the rollover condition is not satisfied and the process jumps from any of steps S2, S4, S5, and S7 to step S12, the rollover flag Fro is cleared (Fro ← 0), and the routine is exited.

  FIG. 6 shows the detection state of the lateral acceleration Gy, the roll rate φv, the roll angular acceleration φa, and the state of the rollover flag Fro due to the vehicle behavior. As shown in the figure, even if the absolute value | Gy | of the lateral acceleration Gy and the absolute value | φv | of the roll rate φv both exceed the threshold values α and β, the absolute value of the roll angular acceleration φa | φa | Does not exceed the threshold value τ, or even if the absolute value | φa | of the roll angular acceleration φa exceeds the threshold value τ, the state does not continue for the set time (delay value Z). In this case, it is determined that the rollover condition is not satisfied, and the rollover flag Fro is cleared. On the other hand, when the absolute value | φa | of the roll angular acceleration φa exceeds the threshold value τ and the state continues for the set time (delay value Z), it is determined that the rollover condition is satisfied, and the roll The over flag Fro is set.

  The threshold values α, β, and τ are different for each vehicle type. For example, in a high center of gravity vehicle such as a one-box vehicle, rollover is more likely to occur than in a low center of gravity vehicle such as a sports car. Therefore, it is set to a relatively low value.

  The value of the rollover flag Fro described above is read by the assist coefficient calculator 22b. Specifically, the processing in the assist coefficient calculator 22b is performed according to an assist correction coefficient setting routine shown in FIG. In this routine, first, the value of the rollover flag Fro is checked in step S21. If the rollover condition of Fro = 1 is satisfied, the process proceeds to step S22. If the rollover condition of Fro = 0 is not satisfied, the process proceeds to step S23.

  In step S22, based on the absolute value | φv | of the roll rate φv, the assist correction coefficient iq is set by referring to the assist correction coefficient table with interpolation calculation, and the routine is exited.

  FIG. 7 shows the characteristics of the assist correction coefficient table. As shown in the figure, the assist correction coefficient iq is set in the range of +1.0 to −1.0, and the assist correction coefficient iq is a value of +1.0 as the absolute value | φv | of the roll rate φv increases. Is set to a negative value in the range of 0> iq, and a dead zone is set in which the assist correction coefficient iq is fixed to +1.0 when the absolute value | φv | is between 0 and β. Has been. Therefore, in the range of +1.0> iq ≧ 0, the assist torque applied to the steering wheel 4 is in a reduced assist state. Further, in the range of 0> iq ≧ −1.0, the steering wheel 4 is in a reverse assist state in which an assist torque in a direction opposite to the steering direction is applied.

  The characteristics of the assist correction coefficient iq stored in the assist correction coefficient table differ for each vehicle type. For example, a high center of gravity vehicle such as a one-box vehicle is different from a low center of gravity vehicle such as a sports car. Since rollover is likely to occur, the inclination is gradually set larger and the dead zone (β) is gradually narrowed as the center of gravity increases.

  Incidentally, in step S22 described above, the assist correction coefficient iq is set based on the magnitude of the absolute value | φv | of the roll rate φv, but the absolute value of the integrated value of the roll rate φv after exceeding the dead zone (β). The assist correction coefficient iq may be set based on the value. By setting the assist correction coefficient iq based on the absolute value of the integral value of the roll rate φv, the lateral acceleration Gy is increased when the roll rate φv is constant, in addition to the case where a sudden rollover occurs. It is possible to effectively avoid rollover even under difficult driving conditions.

  In step S23, the assist correction coefficient iq is set to 1.0 (iq ← 1.0), and the routine is exited.

  The assist correction coefficient iq is read by the target assist current calculation unit 22c. Specifically, the processing in the target assist current calculation unit 22c is performed according to a target assist current setting routine shown in FIG. In this routine, first, in step S31, the steering torque Tq detected by the steering torque sensor 14 and the vehicle speed Vsp detected by the vehicle speed sensor 15 are read, and in step S32, the basic assist is based on the steering torque Tq and the vehicle speed Vsp. The basic assist current Ip is set with reference to the current map. The process in step S32 corresponds to basic assist torque setting means.

  As shown in FIG. 8, the basic assist current map is set to have such characteristics that the basic assist current Ip increases as the vehicle speed Vsp decreases or the steering torque Tq increases, and the steering torque Tq is near zero. Is set to a dead zone where the basic assist current Ip is zero. Therefore, in this basic assist current map, as the steering torque Tq increases, in other words, as the steering wheel 4 becomes heavier, the steering assist force increases and steering becomes easier.

  Next, the process proceeds to step S33, where the assist correction coefficient iq is read. In step S34, the basic assist current Ip is multiplied by the assist correction coefficient iq to set the target assist current P (P ← Ip · iq), and the routine is exited.

  The target assist current P obtained by the target assist current calculator 22c is read by the F / B control calculator 22d. The F / B control calculation unit 22d calculates a difference ΔP (ΔP ← P−Is) between the target assist current P and the motor current Is detected by the current detection unit 25 and supplied to the electric motor 13, and this difference ΔP. A control signal (feedback control signal) D that converges to 0 is generated by proportional-integral control or the like, and is output to the motor drive signal generation circuit 23. The motor drive signal generation circuit 23 generates a motor drive signal (for example, a PWM signal) corresponding to the control signal D output from the F / B control calculation unit 22 d and outputs the motor drive signal to the motor drive circuit 24.

  The motor drive circuit 24 supplies the electric motor 13 with a voltage having a magnitude and direction corresponding to the current flowing by the voltage according to the motor drive signal generated by the motor drive signal generation circuit 23. Then, the driving force of the electric motor 13 is transmitted to the pinion shaft 5 via the assist transmission mechanism 12.

  When the rollover condition is not satisfied (Fro = 0), since the assist correction coefficient iq is fixed to iq = 1.0, P = Ip, and the electric motor 13 is driven with a driving force corresponding to the target assist current P. The electric motor 13 assists the steering torque associated with the steering wheel 4 and reduces the driver's load during steering.

  On the other hand, for example, when the running vehicle suddenly turns or enters the corner at an overspeed, the rollover determination unit 22a satisfies the rollover condition and the rollover flag Fro is set (Fro ← 1). In the assist coefficient calculator 22b, an assist correction coefficient iq is set based on the absolute value | φv | of the roll rate φv. As shown in FIG. 7, when the absolute value | φv | of the roll rate φv exceeds the discomfort zone (β), the assist correction coefficient iq is set to a value that gradually decreases as the absolute value | φv | increases. > Iq is set to a negative value.

  The target assist current calculator 22c multiplies the basic assist current Ip by the assist correction coefficient iq to set the target assist current P, so that the assist torque applied to the steering wheel 4 as the absolute value | φv | of the roll rate φv increases. Decrease. As a result, the steering reaction force when the driver tries to steer the steering wheel 4 in the turning direction becomes relatively large, and rollover can be effectively avoided. Further, when the absolute value | φv | of the roll rate φv increases and the assist correction coefficient iq becomes 0> iq, the assist torque (reverse assist torque) in which the electric motor 13 is opposite to the steering direction with respect to the pinion shaft 5 is obtained. By providing the above, the steering reaction force related to the steering wheel 4 increases, and rollover can be reliably avoided by positively limiting the steering in the turning direction.

  As described above, in this embodiment, when the rollover determination unit 22a detects a rollover sign, the assist torque generated by driving the electric motor 13 is limited, and the steering reaction force is relatively increased. Even if the vehicle is not equipped with a braking system and the rollover cannot be avoided by the braking system, the vehicle with the electric power steering device 1 is installed. If there is, rollover can be easily avoided by applying this embodiment.

  Further, since rollover is avoided by steering by the electric power steering device 1, the tire of the turning outer wheel is compared with the case where the braking system is applied with braking force to the turning outer wheel during turning to avoid rollover. Since grip force can be secured, rollover can be avoided while the vehicle behavior is stabilized.

  The present invention is not limited to the above-described embodiment. For example, the system according to the present invention can be applied to a vehicle equipped with a braking system. By adopting this system in a vehicle equipped with a braking system, braking can be performed. Prior to the rollover avoiding operation by the system, the rollover can be avoided by steering. As a result, rollover can be avoided in stages by controlling different systems. The assist actuator is not limited to the electric motor 13 and may be a hydraulic motor.

Schematic of a vehicle with a rollover control device Circuit block diagram of motor control unit Flowchart showing rollover determination routine Flowchart showing an assist correction coefficient setting routine Flow chart showing a target assist current setting routine Time chart showing changes in absolute value of lateral acceleration, absolute value of roll rate, absolute value of roll angular acceleration, and rollover flag Explanatory drawing of assist correction coefficient table Illustration of basic assist current map

Explanation of symbols

1 ... Electric power steering device,
4 ... Steering wheel,
11L, 11R ... left and right wheels,
12 ... assist transmission mechanism,
13: Electric motor,
14: Steering torque sensor,
15 ... Vehicle speed sensor
16 ... Lateral acceleration sensor,
17 ... Roll rate sensor,
21 ... Motor control unit,
22 ... motor control unit,
22a ... Rollover determination unit,
22b ... assist coefficient calculation unit,
22c ... Target assist current calculation unit,
22d ... control operation part,
23 ... Motor drive signal generation circuit,
24 ... Motor drive circuit,
Gy ... Lateral acceleration,
φv: Roll rate,
φa: Roll angular acceleration,
α, β, τ ... threshold,
Ip: Basic assist current,
iq ... assist correction coefficient,
Is ... motor current,
P: Target assist current,
Tq: Steering torque,
Vsp ... Vehicle speed,
Z: Delay value

Claims (4)

An assist actuator for assisting steering torque related to the steering wheel;
Basic assist torque setting means for setting a basic value of assist torque generated by driving the assist actuator based on at least steering torque;
Rollover determining means for determining whether or not a sign of rollover has been detected based on a physical quantity indicating a lateral behavior acting on a vehicle and a physical quantity indicating a roll direction behavior;
When a rollover sign is detected by the rollover determining means, an acceleration of the physical quantity indicating the roll direction behavior is obtained based on the physical quantity indicating the roll direction behavior, a rollover condition is determined based on the acceleration, An assist correction coefficient setting means for setting an assist correction coefficient for correcting in a direction to decrease the assist torque based on a physical quantity indicating the roll direction behavior when a rollover condition is satisfied ;
A vehicle rollover control device comprising: a target assist torque setting unit that sets the target value of the assist torque by correcting the basic value with the assist correction coefficient. The assist correction coefficient setting means sets the assist correction coefficient that decreases as the absolute value of the physical quantity increases, based on the absolute value of the physical quantity indicating the roll direction behavior. Vehicle rollover control device. The maximum value of the assist correction coefficient is +1.0, the minimum value is -1.0,
The assist correction coefficient setting means sets the assist correction coefficient of a value gradually decreased from a value of +1.0 to a direction of −1.0 as the absolute value of the physical quantity indicating the roll direction behavior increases.
The vehicle rollover control device according to claim 2, wherein the target assist torque setting means sets the assist torque target value by multiplying the basic value by the assist correction coefficient. 4. The rollover control device for a vehicle according to claim 3, wherein when the absolute value of the physical quantity indicating the roll direction behavior is higher than a preset threshold value, the assist correction value is set to +1.0. .

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