JP2007045226A - Vehicle behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure vehicle steering stability even when variable control of roll rigidity is failed. <P>SOLUTION: The vehicle behavior control device is provided with roll rigidity variable control means 9, 10, 12 capable of variable-controlling the roll rigidity of a suspension; and steering characteristic variable control means 8, 12 capable of variable-controlling steering characteristic including damping characteristic of a steering system and power steering assist characteristic. When the roll rigidity is reduced by abnormality of the roll rigidity variable control means 9, 10, 12, the steering characteristic variable control means 8, 12 increase attenuation coefficient of the attenuation characteristic of the steering system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle behavior control device capable of variably controlling the roll rigidity of a vehicle.

The behavior of the vehicle is a composite such as yawing, rolling, and pitching, and an active stabilizer is known as a mechanism for actively variably controlling the rolling (the following [Patent Document 1]). The active stabilizer attaches an actuator to the stabilizer and variably controls the torsional rigidity of the stabilizer, thereby variably controlling the roll rigidity.
JP 2003-226127 A

  However, in the one described in [Patent Document 1], the roll rigidity of each of the front and rear wheels is changed according to the vehicle behavior state / failure state by the active stabilizer. However, if roll rigidity is reduced due to a failure, the roll resonance frequency is lowered to approach the steering resonance frequency, and it becomes easy for the combined vibration of the roll vibration and the steering vibration to occur, and there is a concern that the vehicle stability is lowered. . Therefore, an object of the present invention is to provide a vehicle behavior control device that can ensure vehicle maneuverability even when variable control of roll stiffness fails.

  The vehicle behavior control device according to claim 1 is a roll stiffness variable control means capable of variably controlling the roll stiffness of the suspension, and a steering characteristic capable of variably controlling steering characteristics including a steering steering system damping characteristic and power steering assist characteristic. And a variable control means, and when the roll stiffness is lowered due to an abnormality of the roll stiffness variable control means, the steering characteristic variable control means is characterized by increasing the damping coefficient of the damping characteristic of the steering system.

  According to a second aspect of the present invention, in the vehicle behavior control device according to the first aspect, when the roll rigidity on the rear wheel side becomes abnormal, the damping is less than when the roll rigidity is abnormal on the front and rear wheels. The characteristic is that the attenuation coefficient of the characteristic is further increased.

  According to a third aspect of the present invention, in the vehicle behavior control device according to the first or second aspect, when the roll stiffness on the rear wheel side becomes abnormal, the roll stiffness variable control amount on the front wheel side is reduced. It is said.

  According to a fourth aspect of the present invention, in the vehicle behavior control device according to the first or second aspect, when the roll rigidity on the front wheel side becomes abnormal, the variable control of the roll rigidity on the rear wheel side is not performed. It is said.

  According to the vehicle behavior control device of the first aspect, when the roll rigidity is lowered, the damping coefficient of the steering vibration is increased, thereby increasing the damping of the steering vibration and suppressing the combined vibration of the roll vibration and the steering vibration. Improve vehicle handling.

  According to the vehicle behavior control apparatus of the second aspect, when only the rear wheel roll stiffness variable control is abnormal (decrease in stiffness) and the front wheel roll stiffness variable control is continued, the vehicle tends to understeer. In this case, the yaw resonance frequency increases and approaches the steering resonance frequency, and a coupled vibration of the yaw vibration and the steering vibration is likely to occur. For this reason, when only the rear wheel becomes abnormal, the damping coefficient of the steering resonance is increased more than when the front and rear wheels become abnormal, and not only the combined vibration of the roll vibration and the steering vibration but also the yaw. Coupled vibration of vibration and steering vibration is also suppressed to improve vehicle maneuverability.

  According to the vehicle behavior control apparatus of the third aspect, when only the roll stiffness variable control of the rear wheel is abnormal (decrease in stiffness) and the roll stiffness variable control of the front wheel is continued, the vehicle tends to be understeered. At this time, if the roll rigidity on the front wheel side becomes too high by the roll rigidity variable control of the front wheel, the tendency to understeer becomes strong. Thus, when only the rear wheel becomes abnormal, the roll stiffness variable control amount of the front wheel is reduced (including stop), thereby preventing the understeer tendency from becoming too strong and improving the vehicle handling performance.

  According to the vehicle behavior control apparatus of the fourth aspect, when the roll rigidity on the front wheel side becomes abnormal (decrease in rigidity), the vehicle tends to oversteer. At this time, if the roll rigidity on the rear wheel side becomes too high by the roll rigidity variable control of the rear wheel, the oversteer tendency becomes strong. Therefore, when the front wheel becomes abnormal, the roll rigidity variable control of the rear wheel is not performed, so that the oversteer tendency is prevented from becoming too strong, and the vehicle stability is improved.

  Hereinafter, an embodiment of a vehicle behavior control device of the present invention will be described with reference to the drawings. FIG. 1 shows a vehicle configuration diagram in which the vehicle behavior control device of this embodiment is mounted. The vehicle 1 includes four wheels FR, FL, RR, and RL. The front wheels FR and FL are steering wheels, and the steering gear box 2 and the hub carrier 3 of each front wheel FR and FL are connected. A rack bar 2a is built in the gear box 2, and both ends of the rack bar 2a are connected to the hub carrier 3 described above via tie rods 2b.

  A steering shaft 4 in a steering column (not shown) is inserted into the gear box 2. A pinion gear at the front end of the steering shaft 4 meshes with the rack of the rack bar 2a to constitute a so-called rack and pinion 2c. A steering wheel 5 is attached to the other end of the steering shaft 4. In addition, a steering angle sensor 6 that detects a rotation angle (steering angle) of the steering shaft 4 and a steering torque sensor 7 that detects torque applied to the steering shaft 4 are also attached to the steering shaft 4.

  The steering gear box 2 of the present embodiment also incorporates a motor 8 of an electric power steering mechanism. By controlling the control amount of the motor 8, the assisting force of the power steering or the vibration of the steering system is controlled in the steering system. It is possible to add a damping torque that attenuates. The steering gear box 2 also includes a stroke sensor 2d that detects the stroke amount of the rack bar 2a.

  In the vehicle 1 of the present embodiment, the active stabilizer 9 is attached to the front wheels FR, FL and the rear wheels RR, RL. Both ends of each active stabilizer 9 are attached to each hub carrier 3 of the left and right wheels. The active stabilizer 9 is provided with an actuator 10 for variably controlling the roll rigidity at the center thereof. The structure of the active stabilizer is, for example, as described in JP-A-2005-88722. The active stabilizer 9 is configured to increase the rigidity by driving the actuator 10, and the roll rigidity is reduced when an abnormality occurs. By driving the actuator, the actuator 10 generates torque in the direction opposite to the torsional torque acting on the active stabilizer 9, thereby increasing the roll rigidity.

  Further, a wheel speed sensor 11 is attached to each wheel FR, FL, RR, RL. The sensors 2d, 6, 7, 11 and the actuators 8, 10 described above are connected to an ECU 12 that controls the vehicle behavior in an integrated manner. The ECU 12 is an electronic control unit including a CPU, a ROM, a RAM, an input / output unit, and the like. The ECU 12 receives output from each sensor and sends a control signal to each actuator. The ECU 12 can also diagnose the state of each actuator from the control signal of each actuator (for example, the actuator 10 or the motor 8) (can determine whether or not a failure has occurred). The stabilizer 9 is divided into two parts at the torsion bar portion, and is twisted by relative rotation by the actuator 10 to make the roll rigidity variable. By driving the actuator 10 so as to achieve the target rotation angle, a predetermined roll rigidity can be obtained. The actuator 10 has means for detecting an actual rotation angle, and when the deviation between the actual rotation angle and the target rotation angle becomes a predetermined value or more, it is determined as abnormal.

  The power steering mechanism will be briefly described. The power steering mechanism applies the assist torque for reducing the steering operation force of the driver to the steering system by the motor 8, but the motor 8 also has a role of applying a damping torque for reducing the steering vibration. Here, the assist torque amount is calculated based on the steering torque detected by the steering torque sensor 7 and the vehicle speed detected by the wheel speed sensor 11.

  At the same time, a damping torque amount for attenuating steering vibration is calculated based on the steering angular velocity and the vehicle speed of the steering wheel 5 detected by the steering angle sensor 6. The attenuation coefficient at this time is Cst. Further, as described above, when the active stabilizer 9 is in failure (during failure), the attenuation coefficient is increased, and the correction coefficient therefor is set to Ksc (Cst ← Cst × Ksc). If Ksc = 1, no correction is performed. The torque output from the motor 8 is the sum of the assist torque and the damping torque.

  Further, the steering resonance frequency, roll resonance frequency, and yaw resonance frequency will be briefly described. Normally, these resonance frequencies are arranged in the order of roll resonance frequency, steering resonance frequency, and yaw resonance frequency from the highest. Each resonance frequency is set so as to be as far as possible from each other so that mutual vibrations are coupled and resonances do not overlap.

  However, if the active stabilizer 9 breaks down, the roll resonance frequency (and the yaw resonance frequency when the yaw characteristics are also different) shifts, and the above-described coupled vibration is likely to occur. Therefore, in the present embodiment, the coupled vibration is suppressed by increasing the damping coefficient of the steering vibration that is likely to cause the coupled vibration, and the operability is improved.

  Next, a first embodiment of vibration suppression control by the above-described apparatus will be described. A flowchart of this control is shown in FIG. As shown in FIG. 2, it is first determined whether or not the active stabilizer 9 on the rear wheels RR and RL side has failed (step 200). If the rear wheel RR, RL side active stabilizer 9 has not failed, it is next determined whether or not the front wheel FR, FL side active stabilizer 9 has failed (step 205).

  If step 205 is negative and the active stabilizers 9 on both the front wheels FR and FL and the rear wheels RR and RL have not failed, Ksc = 1 is set (step 210), and Cst = Cst × Ksc (step) 215), the steering damping torque amount calculated based on the steering angular velocity and the vehicle speed is not corrected (the damping coefficient Cst is not corrected).

  On the other hand, when step 200 is affirmed, it is first determined whether or not the active stabilizer 9 on the front wheels FR, FL side has failed (step 220). When step 220 is affirmed and the active stabilizers 9 on both the front wheels FR and FL and the rear wheels RR and RL have failed, Ksc = Kscf (> 1) is set (step 225), and Cst = Cst × The steering damping torque amount calculated based on the steering angular velocity and the vehicle speed is corrected by Ksc (step 215) (the damping coefficient Cst is increased). Kscf is a correction coefficient when the active stabilizers 9 on both the front wheels FR, FL side and the rear wheels RR, RL are failing.

  As described above, when the active stabilizers 9 on both the front wheels FR, FL side and the rear wheels RR, RL are failing, the roll resonance frequency is lowered and approaches the steering resonance frequency. As a result, steering resonance and roll resonance are easily coupled. For this reason, the damping coefficient Cst is increased to increase the damping force of the steering vibration, and the steering vibration and the roll vibration are more effectively attenuated to improve the operability.

  On the other hand, if step 220 is negative, that is, if only the rear wheel RR, RL side active stabilizer 9 is failing, first, the control gain of the front wheel FR, FL side active stabilizer 9 is changed (step). 230). This gain change is performed so that the roll rigidity is lowered. If only the active stabilizer 9 on the rear wheels RR, RL fails and the roll rigidity on the rear wheels RR, RL decreases (in other words, if the roll rigidity on the front wheels FR, FL side increases), the vehicle tends to understeer. It becomes. At this time, if the roll rigidity on the front wheels FR, FL side becomes too high with respect to the roll rigidity of the rear wheel, the understeer tendency becomes too strong. Therefore, when only the active stabilizer 9 on the rear wheels RR and RL side fails, the roll stiffness on the front wheels FR and FL side is reduced (the roll stiffness variable control itself may be stopped), so that an understeer tendency is strong. Prevents becoming too much and improves vehicle handling.

  After step 230, Ksc = Kscrf (> Kscf) is set (step 235), and the damping torque amount calculated based on the steering angular speed and the vehicle speed is corrected by Cst = Cst × Ksc (step 215) (damping coefficient). Cst is increased). Kscrf is a correction coefficient when only the rear wheel RR, RL side active stabilizer 9 fails, and is larger than the above-described Kscf. That is, the damping coefficient Cst is increased so that the damping torque of the steering system is increased more than in the case of step 225 described above.

  Even when only the rear wheel RR, RL side active stabilizer 9 fails, the roll resonance frequency decreases (the amount of decrease is caused by the active stabilizers 9 on both the front wheels FR, FL side and the rear wheels RR, RL side failing). Less than if). As a result, the roll resonance frequency again approaches the steering resonance frequency. As a result, steering resonance and roll resonance tend to be easily coupled. For this reason, the damping coefficient Cst is increased to increase the damping force of the steering vibration, and the steering vibration and the roll vibration are more effectively attenuated to improve the operability.

  Further, when only the active stabilizer 9 on the rear wheels RR, RL side fails, the yaw resonance frequency increases and approaches the steering resonance frequency. As a result, yaw resonance also tends to be coupled with steering resonance. Therefore, here, the correction coefficient is set to Kscrf larger than the above-described Kscf, and the damping coefficient Cst is increased to obtain a larger steering damping force. By doing so, the three coupled resonances of the roll resonance, the steering resonance, and the yaw resonance are effectively attenuated to improve the operability.

  Finally, the case where step 205 is affirmed is a case where only the front wheel FR, FL side active stabilizer 9 has failed. In this case, the roll stiffness variable control of both the active stabilizers 9 on the rear wheels RR and RL side is not performed (step 240). When only the front wheel FR, FL side active stabilizer 9 fails and the roll rigidity on the front wheel FR, FL side is lowered, an oversteer tendency occurs. At this time, if the roll rigidity on the rear wheels RR, RL side becomes too high with respect to the roll rigidity of the front wheels, the oversteer tendency becomes too strong. Therefore, if only the front wheel FR, FL side active stabilizer 9 fails, the roll stiffness variable control of both the rear wheel RR, RL side active stabilizers 9 is not performed and the oversteer tendency becomes too strong. To improve vehicle handling.

  The first embodiment described above is an example in which the failure status of the active stabilizer 9 on the front wheels FR, FL side and the rear wheels RR, RL side is determined in detail, but more simply, the front wheels FR, FL side and the rear wheels RR, Control may be performed such that the steering damping coefficient Cst is changed (increased) only when both active stabilizers 9 on the RL side fail. FIG. 3 shows a flowchart in this case.

  In this case, first, it is determined whether or not the active stabilizers 9 on both the front wheels FR and FL and the rear wheels RR and RL have failed (step 300). When step 300 is denied and the active stabilizers 9 on both the front wheels FR, FL side and the rear wheels RR, RL have not failed (in this embodiment, only one active stabilizer 9 has failed) Is included in (step 310), Cst = Cst × Ksc (step 315), and the damping torque amount calculated based on the steering angular velocity and the vehicle speed is not corrected (the damping coefficient Cst is not corrected). ).

  If step 300 is affirmed and the active stabilizers 9 on both the front wheels FR and FL and the rear wheels RR and RL have failed, Ksc = Kscf (> 1) is set (step 325), and Cst = Cst × The amount of damping torque calculated based on the steering angular velocity and the vehicle speed is corrected by Ksc (step 315) (the damping coefficient Cst is increased). In this way, simple control is possible.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the actuator (motor 8) for applying the assist torque for power steering and the damping torque for damping the steering vibration is attached to the steering gear box 2, but the actuator is attached to the steering column side. It may be a system.

It is a vehicle block diagram carrying one Embodiment of the vehicle behavior control apparatus of this invention. 3 is a flowchart of steering damping torque correction control (first embodiment). 3 is a flowchart of steering damping torque correction control (first embodiment).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Steering gear box, 2a ... Rack bar, 2b ... Tie rod, 2c ... Rack and pinion, 2d ... Stroke sensor, 3 ... Hub carrier, 4 ... Steering shaft, 5 ... Steering wheel, 6 ... Steering angle sensor DESCRIPTION OF SYMBOLS 7 ... Steering torque sensor, 8 ... Motor (steering characteristic variable control means), 9 ... Active stabilizer (roll rigidity variable control means), 10 ... Actuator (roll rigidity variable control means), 11 ... Wheel speed sensor, 12 ... ECU (Roll stiffness variable control means, steering characteristic variable control means).

Claims (4)

Roll stiffness variable control means capable of variably controlling the roll stiffness of the suspension;
Steering characteristic variable control means capable of variably controlling steering characteristics including steering steering system damping characteristics and power steering assist characteristics,
The vehicle behavior control device according to claim 1, wherein when the roll stiffness is lowered due to an abnormality of the roll stiffness variable control means, the steering characteristic variable control means increases a damping coefficient of the damping characteristic of a steering system.   The damping coefficient of the damping characteristic is increased more greatly when the roll rigidity on the rear wheel side becomes abnormal than when the roll rigidity on both front and rear wheels becomes abnormal. Vehicle behavior control device.   3. The vehicle behavior control device according to claim 1, wherein when the roll rigidity on the rear wheel side becomes abnormal, the roll rigidity variable control amount on the front wheel side is reduced. The vehicle behavior control device according to claim 1 or 2, wherein when the roll rigidity on the front wheel side becomes abnormal, variable control of the roll rigidity on the rear wheel side is not performed.

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