JP3557907B2 - Power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power steering device that assists a driver's steering operation in a motor vehicle by hydraulic pressure of a hydraulic actuator or rotational force of an electric motor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an automobile, a power steering that applies an auxiliary steering torque different from the steering torque applied by a driver when operating a steering wheel of a driver and assists the steering torque of the driver to reduce a burden on the driver during the steering operation. Devices are known.
[0003]
As a means for applying the auxiliary steering torque, a hydraulic actuator or an electric motor (hereinafter referred to as a motor) is generally used, and the hydraulic torque of the hydraulic actuator or the rotation torque of the motor is applied as the auxiliary steering torque. . In particular, in the latter type of electric power steering device using a motor, since the magnitude of the rotational torque of the motor can be freely set independently of the steering operation of the driver, fine assistance suitable for the driver's feeling is provided. The steering torque can be controlled. For this reason, in recent years, as shown in, for example, Japanese Patent No. 2651762, development and commercialization of an electric power steering device have been advanced.
[0004]
[Problems to be solved by the invention]
By the way, in the above-described conventional power steering device, the magnitude of the auxiliary steering torque is controlled according to the magnitude of the steering torque of the driver and according to the vehicle speed. Specifically, when the driver's steering torque is small, or when the vehicle speed is low, a large auxiliary steering torque is applied to reduce the driver's steering burden, and conversely, when the driver's steering torque is large or when the vehicle speed is large. At times, control is performed such that assist by the auxiliary steering torque is reduced and a firm and responsive steering feeling is obtained.
[0005]
However, the need for assisting with the assisting steering torque is not limited to when the steering torque of the driver is low or when the vehicle speed is low. For example, in the case where there is an obstacle ahead in the traveling direction and the obstacle is to be avoided, a steering operation at a much higher speed than in a normal steering operation is required. It is. In particular, as the time until the vehicle reaches the obstacle (the time to allow collision) is shorter, faster steering is required, and it is desired that the assist by the assist steering torque is larger.
[0006]
However, in the conventional power steering apparatus, as described above, the setting is made exclusively in accordance with the driving state of the own vehicle such as the magnitude of the steering torque of the driver and the magnitude of the vehicle speed. There was no control according to the relationship with the outside. For this reason, even if an obstacle is found ahead of the traveling direction traveling at a high speed and the driver tries to avoid the obstacle, the auxiliary steering torque remains set to a small value, and the driver who performs the steering operation for avoiding the obstacle is set to a small value. The burden was heavy.
[0007]
The present invention has been made in view of such a problem, and sets the magnitude of the auxiliary steering torque in accordance with a margin for collision with an obstacle ahead in the traveling direction, thereby facilitating a steering operation for collision avoidance. An object of the present invention is to provide a power steering device that can be quickly operated.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the power steering device of the present invention (claim 1) , the steering wheel assist of the driver is assisted by calculating the auxiliary steering torque according to the magnitude of the steering torque at the time of steering the steering wheel of the driver. Also, an object existing ahead of the own vehicle is detected by the front object detecting means, and the relative position of the object with respect to the own vehicle is measured by the front object position measuring means based on the detected information, and the relative position and relative position of the measured object are measured. The time required until the host vehicle collides with the object is calculated as a margin time by the margin time calculation means based on the time change of the vehicle. Then, the control gain setting means sets a control gain for increasing the auxiliary steering torque when the margin time calculated by the margin time calculating means becomes equal to or less than a predetermined value .
[0009]
Preferably, the auxiliary steering torque is increased as the margin time is shortened (claim 2) .
As a result, the assist steering torque for assisting the driver to steer the steering wheel is adjusted to increase as the margin time is shorter, that is, as the urgency of collision avoidance is higher.
Further, it is preferable that the control gain setting means sets a control gain that increases the auxiliary steering torque as the steering angular velocity of the steering of the driver increases.
Further, it is preferable that the control gain setting means sets a control gain for increasing the auxiliary steering torque only when it is determined that there is a driver's intention to avoid an obstacle.
A path predicting means for calculating a predicted path of the host vehicle; and measuring a time change of a lateral shift amount of the predicted path with respect to the obstacle, and when the lateral shift amount is increasing, a driver's intention to avoid the obstacle. It is preferable to include a determination unit that determines that there is a condition (claim 5).
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIGS. 1 to 4 show a power steering apparatus according to an embodiment of the present invention. This power steering apparatus, like a conventional power steering apparatus, responds to the driver's steering torque and the vehicle speed of the host vehicle. If an obstacle is present ahead of the traveling direction while controlling the magnitude of the auxiliary steering torque, the driver controls the magnitude of the auxiliary steering torque according to the time to collision with the obstacle, and the driver avoids the collision. The steering operation can be performed easily and quickly.
[0011]
For this reason, as shown in FIG. 1, in the present power steering device, a steering torque sensor 1 that detects a steering torque _Td when a driver performs a steering operation on a steering wheel, and a vehicle speed sensor 2 that detects a vehicle speed V of the host vehicle, And an obstacle existing ahead in the traveling direction is detected, and when there is a possibility of collision with the detected obstacle, various times for calculating a time required until the collision as a collision margin time (margin time) are provided. An information detecting means is provided. The information detecting means includes a relative position of the front obstacle with respect to the own vehicle (front object position), that is, a distance d to the front obstacle and a yaw angle shift amount β of the front obstacle with respect to the center line of the own vehicle [hereinafter, forward Object position φ (d, β)], a front object detection sensor (front object detection means) 3 such as a laser radar or an ultrasonic sensor, and a steering wheel angle (steering angle) θ at the time of a driver's steering operation. Is the steering angle sensor 4 for detecting the steering angle.
[0012]
A control means 100 for controlling the power steering mechanism 10 based on the detection information of these sensors 1 to 4 is provided. The control means 100 controls the current value supplied to the DC motor 11 to The power steering mechanism 10 generates an auxiliary steering torque set based on the detection information items 1-4. That is, the present embodiment shows a case where the electric power steering apparatus of the present invention is configured by an electric power steering apparatus that assists the driver's steering operation with the rotation torque of the DC motor 11.
[0013]
As shown in FIG. 1, the power steering mechanism 10 includes a DC motor 11, a worm shaft 12a connected to an output shaft of the DC motor 11, and a worm wheel shaft 12b driven by meshing with the worm shaft 12a. And a pinion shaft 13 that meshes with a worm wheel shaft 12b and a tooth portion 14a of a rack shaft 14. With such a configuration, in the power steering mechanism 10, the rotational torque generated by the DC motor 11 is amplified in the speed reducer 12, and transmitted to the rack shaft 14 via the pinion shaft 13 as the auxiliary steering torque, so that the driver's steering can be performed. It is designed to assist the operation. The steering torque generated by the driver steering the steering wheel is transmitted to the rack shaft 14 via a steering shaft (not shown).
[0014]
Here, the internal configuration and functions of the control unit 100 will be described in detail. The control unit 100 includes, as its functional elements, a steering torque measuring unit 101, a vehicle speed measuring unit 102, a front object position measuring unit 103, and a steering angle measuring unit 104. The steering torque T _d , the vehicle speed V, the front object position φ (d, β), and the steering angle θ are measured based on the detection information of the sensors 1 to 4 described above.
[0015]
Further, a margin time calculation unit 105 and a steering angular velocity calculation unit 114 are provided, and the margin time calculation unit 105 determines a relative time based on a time change of the distance d to the front obstacle measured by the front object position measurement unit 103. The speed V _d (= Δd / Δt) is calculated, and from the distance d to the obstacle in front and the calculated relative speed V _d , if there is a possibility that the vehicle will collide with the detected obstacle, the collision until collision occurs The margin time t _C (= d / V _d ) is calculated. The steering angular velocity calculating means 114 calculates the steering angular velocity ω (= Δθ / Δt) based on the time change of the steering angle θ measured by the steering angle measuring means 104.
[0016]
Further, the control means 100 includes a motor current value calculation driving means 106. The motor current value calculation drive unit 106 will be described. The motor current value calculation drive unit 106 has a function of calculating a current value to be supplied to the DC motor 11 and supplying the calculated current to the DC motor 11 for driving. It comprises a motor current value calculation means 107, a motor current value correction means 108, and a motor drive means 111.
[0017]
First, the motor current value calculation means 107 calculates a current value to be supplied to the DC motor 11. The DC motor 11 generates a rotation torque _Tr proportional to the magnitude of the supplied current value, and the rotation torque _Tr is amplified and applied to the rack shaft 14 as the auxiliary steering torque T. . Therefore, the motor current value calculating unit 107, first, a basic value of the steering assist torque to be applied to the rack shaft 14 to set the (basic steering assist torque) T _0, depending on the magnitude of the basic assist steering torque T ₀ The calculated current value is calculated.
[0018]
The size of the basic assist steering torque T ₀ Here, as in the conventional electric power steering apparatus, and is set according to the steering torque T _d and the vehicle speed V. That is, when the steering torque _Td is small and the vehicle speed V is low, the driver's steering load is reduced by the large assist, and the assist is increased as the steering torque _Td increases and the vehicle speed V increases. the is the steering sense of firm response by reducing has become a set of basic assist steering torque T ₀ as obtained.
[0019]
Next, the motor current value correction means 108 adjusts (changes) the current value by multiplying the current value calculated by the motor current value calculation means 107 by appropriate control gains K ₁ and K ₂ . It has a function of appropriately controlling the magnitude of the applied auxiliary steering torque T (T = K ₁ × K ₂ × T ₀ ). Specifically, the motor current value correction means 108 is provided with two control gain setting means, a first control gain setting means 109 and a second control gain setting means 110. control gain setting means 109, depending on the collision tolerable time t _C to the preceding obstacles calculated by the margin time calculating means 105 is adapted to set the first gain K _1.
[0020]
Figure 2 illustrates an example of the setting map, when the collision tolerable time t _C is large, i.e., if the driver has enough time to avoid the obstacle, the gain K ₁ is 1. The current is set to 0, and a current corresponding to the normal steering torque _Td and the vehicle speed V is supplied to the DC motor 11. Then, when the time to collision t _C becomes equal to or less than a predetermined value t _C0 , the gain K ₁ is increased in accordance with the degree of decrease in the time to collision t _C , and the auxiliary steering torque T is increased. This enables the driver to perform quick steering operations.
[0021]
On the other hand, the latter second control gain setting means 110 is for setting the second gain K ₂ in accordance with the steering angular velocity ω of the driver. That is, when trying to avoid an obstacle in front, the higher the steering angular velocity ω at which the driver operates the steering wheel, the higher the urgency can be considered. Therefore, in such a high urgency, the DC motor The auxiliary steering torque T is increased by increasing the value of the current supplied to the motor 11 to enable the driver to perform a quick steering operation.
[0022]
FIG. 3 shows an example of a setting map of the gain K _2, and 1.0 the gain K ₂ when the steering angular velocity ω is 0, so that the gain K ₂ is also increased in response to an increase in the steering angular velocity ω It has become. However, when the steering angular velocity ω is equal to or more than the predetermined value ω ₀ , the magnitude of the gain K ₂ is maintained at the predetermined value k _0, and the steering operation of the driver is destabilized by applying an excessive auxiliary steering torque T. It is designed to prevent that.
[0023]
As described above, the motor current value correction means 108 sets the control gains K ₁ and K ₂ according to the time to collision t _C and the steering angular velocity ω, and sets the current values according to the basic auxiliary steering torque T ₀ to these values. The control gains K ₁ and K _{2 are} adjusted. However, these control gains K ₁ and K ₂ are set to assist the steering operation when the driver tries to avoid a forward obstacle. belongs to. Therefore, when the driver is not trying to perform the avoidance steering, the motor current value is not changed by the control gains K ₁ and K ₂ while respecting the driver's intention (that is, K ₁ = 1 and K ₂ = 1). To).
[0024]
Thus, the control gain setting means 109 and 110, both, there is an obstacle ahead, and, only when the driver is trying to avoid it, control in accordance with the collision tolerable time t _C and the steering angular velocity ω The change control of the motor current value is performed by the gains K ₁ and K ₂ . Then, when there is no obstacle ahead or when the driver does not try to avoid the obstacle even if it exists, the control gains K ₁ and K ₂ are held at 1.0. .
[0025]
The determination unit 112 determines whether the driver is trying to avoid an obstacle ahead. The determining unit 112 determines whether or not an obstacle exists in the traveling direction of the own vehicle by comparing the position of the obstacle ahead and the predicted course of the own vehicle. It is determined whether or not the driver is trying to avoid an obstacle based on a time change of the shift amount with respect to the object.
[0026]
First, as the position of the obstacle ahead, the measurement result of the forward object position measuring means 103 is used. The front object detection sensor 3 scans a predetermined angle range in front of the host vehicle, and detects a response time until the wave transmitted from the transmission unit is reflected by the obstacle and received by the reception unit. Therefore, the forward object position measuring means 103 calculates the distance d from the own vehicle to the obstacle from the response time, and calculates the yaw angle shift amount β of the obstacle with respect to the own vehicle center line from the receiving direction of the reflected wave. Thus, the positional relationship of the obstacle with respect to the own vehicle can be grasped.
[0027]
On the other hand, the predicted course of the own vehicle is calculated by the course predicting means 113. The vehicle speed V and the steering angle θ are input from the vehicle speed measurement unit 102 and the steering angle measurement unit 104 to the course prediction unit 113, and are calculated from the vehicle speed V, the steering angle θ, and the steering angle θ. The predicted course of the vehicle is calculated from the yaw rate. Note that the yaw rate may be detected by providing a separate yaw rate sensor instead of calculating from the steering angle θ.
[0028]
The determination of whether or not an obstacle is present in the traveling direction of the host vehicle and the determination of whether or not the driver is trying to avoid the obstacle by the determination means 112 are both performed by the prediction calculated by the course prediction means 113. This is performed based on the amount of lateral displacement of the obstacle ahead of the course.
First, it is determined whether or not an obstacle exists in the traveling direction of the host vehicle by comparing the amount of lateral displacement of the obstacle ahead of the predicted course with a predetermined amount (for example, the width of the road lane), and determining the amount of lateral deviation. In the following cases, it is determined that the obstacle exists in the traveling direction. On the other hand, whether or not the driver is trying to avoid an obstacle is determined by measuring the time change of the lateral deviation amount, and when the lateral deviation amount is increasing, that is, the predicted course of the own vehicle is moving away from the obstacle ahead. In such a case, it is determined that the driver is performing a steering operation to avoid an obstacle.
[0029]
Motor current value correcting unit 108, the determination unit 112 are present in the obstacle traveling direction, and, only when it is determined that they try to avoid it, according to the steering angular velocity ω and the collision tolerable time t _C described above The control for changing the control gains K ₁ and K ₂ (processing to set a value other than 1.0) is performed.
Thus, the current value calculated by the motor current value calculating means 107 and multiplied by the appropriate control gains K ₁ and K ₂ by the motor current value correcting means 108 is input to the motor driving means 111. The motor driving means 111 supplies a current corresponding to the input current value to the DC motor 11, and the rotational torque output from the DC motor 11 is amplified by the speed reducer 12, and the auxiliary steering torque T ( T = K ₁ × K ₂ × T ₀ ) is input to the rack axis. The motor driving means 111 is provided with a low-pass filter (not shown), which alleviates a sudden change in the current value accompanying the change control of the control gains K ₁ and K _{2 in} the motor current value correcting means 108, and reduces the auxiliary steering torque T. Sudden changes and unnatural fluctuations are prevented.
[0030]
Since the power steering device as one embodiment of the present invention is configured as described above, the auxiliary steering torque T to be generated in the power steering mechanism 10 is set, for example, according to the flow shown in FIG.
First, in this power steering apparatus, a steering torque measuring means 101, a vehicle speed measuring means 102, a front object position measuring means based on each detection information of a steering torque sensor 1, a vehicle speed sensor 2, a forward object detection sensor 3, and a steering angle sensor 4. 103, the steering angle measuring means 104 measures the steering torque T _d , the vehicle speed V, the forward object position φ (d, β), and the steering angle θ (step S10).
[0031]
Then, based on the measured steering torque _Td and the vehicle speed V, the motor current value calculation means 107 provides a large assist when the steering torque _Td is small and when the vehicle speed V is small, and the steering torque _Td is large. as the made, and as assist amount as the vehicle speed V increases is reduced, to set basic value of the steering assist torque (basic steering assist torque) T _0. Then, to calculate a current value to be supplied to the DC motor 11 in order to generate a rotational torque corresponding to the basic assist steering torque T ₀ (step S20).
[0032]
At this time, the judging means 111 compares the amount of lateral deviation of the forward obstacle from the predicted course calculated from the vehicle speed V and the steering angle θ with a predetermined amount, thereby detecting the presence of the obstacle in the traveling direction of the own vehicle. (Step S30), and when the lateral deviation amount is equal to or more than a predetermined amount, it is determined that an obstacle exists in the traveling direction, and further, the driver avoids the obstacle based on a temporal change in the lateral deviation amount. It is determined whether the user is trying to do so (step S40).
[0033]
If the amount of lateral displacement is increasing, it is determined that the driver is performing a steering operation to avoid the obstacle, and the margin time calculating means 105 determines the distance d to the obstacle and the relative speed _Vr . The collision margin time _Tc is calculated based on the above, and the steering angular velocity ω is calculated by the steering angular velocity calculating means 113 based on the time change of the steering angle θ (step S50).
[0034]
In response to this determination, the motor current value correction means 108 performs control for changing the control gains K ₁ and K _2. First, the first control gain setting means 109 sets the gain when the collision margin time t _C is large. K ₁ and may be set to 1.0, when it is less than the predetermined value t _C0 there is collision tolerable time t _C is gradually increasing the gain K ₁ according to the decrease of the collision tolerable time t _C. On the other hand, in the second control gain setting unit 110, the driver higher steering angular velocity omega of the handle, gradually increases the gain K ₂ in response to an increase in steering is regarded to have a high urgency angular velocity omega.
[0035]
Thus, when the driver performs a steering operation to avoid an obstacle in front of the host vehicle, the motor drive unit 111 sets these control gains K ₁ and K ₂ to a current value corresponding to the basic auxiliary steering torque T _0. Is supplied to the DC motor 11, and an auxiliary steering torque T (T = K ₁ × K ₂ × T ₀ ) corresponding to the collision allowance time t _C and the steering angular velocity ω is supplied from the power steering device 10. The output is output to the rack shaft 14 (variable assist control, step S60).
[0036]
As described above, according to the present power steering apparatus, when an obstacle is present ahead of the traveling direction and the driver performs a steering operation to avoid the obstacle, the auxiliary steering for assisting the driver's steering operation is performed. Since the control gain K ₁ of the torque T (T = K ₁ × K ₂ × T ₀ ) is increased, the driver receives the assist of the auxiliary steering torque T which increases with the increase of the control gain K _1. Therefore, there is an advantage that the steering operation for avoiding the collision can be easily performed. Then, the control gain K _1, so the collision tolerable time t _c is set to be shorter greater, the higher the degree of urgency of the collision avoidance, there is an advantage that enables more rapid avoidance steering.
[0037]
Further, there is an obstacle ahead in the traveling direction, in the case so as to avoid this, since so as to increase the control gain K ₂ in accordance with the steering angular velocity ω of the driver of the handle, the driver steep As the steering operation is required, more powerful assist can be obtained, and there is an advantage that the steering operation for avoiding a collision can be quickly performed.
[0038]
Further, in the present power steering apparatus, even when an obstacle is detected ahead, if the driver does not perform a steering operation for avoiding a collision, the control gain K according to the collision margin time _Tc and the steering angular velocity ω. _1, since the so adjustment of K ₂ is not carried out, with respect to the driver's intention, possible to prevent the giving uncomfortable feeling to the driver by the assist control based on erroneous detection information of the forward object detecting sensor 3 There is also an advantage that can be.
[0039]
Further, the power steering apparatus of the present invention can use the configuration of the conventional electric power steering apparatus as it is as the mechanical configuration, so that the above-described effects can be obtained at low cost, and the fail-safe can be applied to the conventional electric power steering apparatus. There is also an advantage that it can be performed by the same processing as described above.
It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the spirit of the present invention. For example, in the above-described embodiment, a case has been described in which the power steering device of the present invention is applied to an electric power steering device. However, the power steering device may be applied to a hydraulic power steering device. In this case, for example, it includes an electric motor in parallel with the hydraulic mechanism may be to control in accordance with the rotational torque collision tolerable time of the electric motor t _c and the steering angular velocity omega.
[0040]
【The invention's effect】
As described above in detail, according to the power steering device of the present invention (claim 1) , when an object is present ahead of the traveling direction, the margin time before the collision with the object is less than or equal to a predetermined value. At this time, since the control gain for increasing the auxiliary steering torque is set , the driver receives the assist of the auxiliary steering torque, the magnitude of which is appropriately adjusted by adjusting the control gain, and promptly causes a collision. There is an advantage that steering operation for avoidance can be performed.
Further, according to the power steering device of the present invention (claim 2), there is an advantage that the higher the urgency of collision avoidance, the more quickly the avoidance steering can be performed.
Further, according to the power steering device of the present invention (claim 3), the stronger the driver requires a steer steering operation, the stronger the assist can be obtained, and the faster the steering operation for avoiding a collision. There is an advantage that can be performed.
Further, according to the power steering apparatus of the present invention (claims 4 and 5), the driver's intention can be respected, and the driver can feel uncomfortable by assist control based on erroneous detection information of a forward object. There is an advantage that can be prevented.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration of a power steering device as one embodiment of the present invention.
It is a diagram illustrating a setting example of a control gain K ₁ according to this collision tolerable time power steering apparatus as an embodiment of the present invention; FIG.
3 is a diagram showing a setting example of a control gain K ₂ corresponding to the steering angular velocity according to the power steering apparatus as an embodiment of the present invention.
FIG. 4 is a flowchart showing a flow of processing of the power steering device as one embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 steering torque sensor 2 vehicle speed sensor 3 front object detection sensor (front object detection means)
Reference Signs List 4 steering angle sensor 10 power steering mechanism 11 DC motor 12 reduction gear 13 pinion shaft 14 rack shaft 100 control means 103 front object position measurement means 105 allowance time calculation means 106 motor current value calculation drive means 107 motor current value calculation means 108 motor current Value correction means 109 first control gain setting means (control gain setting means)
110 second control gain setting means 111 motor driving means 112 determination means 113 course prediction means

Claims (5)

A power steering device that calculates an auxiliary steering torque according to a magnitude of a steering torque at the time of steering of a driver's steering wheel, and assists a steering wheel of the driver with the auxiliary steering torque,
Forward object detection means for detecting an object in front of the vehicle,
Forward object position measurement means for measuring a relative position of the object with respect to the own vehicle based on the detection information of the front object detection means,
A margin time calculation unit that calculates a time required until the host vehicle collides with the object based on a relative position of the object measured by the front object position measurement unit and a time change of the relative position as a margin time,
When said margin time calculated by the time margin calculating means is equal to or less than a predetermined value, and wherein <br/> that a control gain setting means for setting a control gain that increases the auxiliary steering torque Power steering device. The control gain setting means increases the auxiliary steering torque as the margin time decreases.
The power steering device according to claim 1, wherein: The control gain setting means sets a control gain that increases the auxiliary steering torque as the steering angular velocity of the steering wheel of the driver increases.
The power steering device according to claim 1 or 2, wherein: The control gain setting means sets a control gain for increasing the auxiliary steering torque only when it is determined that there is a driver's intention to avoid an obstacle.
The power steering apparatus according to any one of claims 1 to 3, wherein Route prediction means for calculating a predicted route of the vehicle,
A determination unit that measures a temporal change in a lateral shift amount of the predicted course with respect to the obstacle and determines that the driver has an intention to avoid the obstacle when the lateral shift amount is increased.
The power steering apparatus according to claim 4, wherein:

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