CN103963837B - The control setup of apparatus for rear wheel steering - Google Patents

Abstract

The invention provides a control device for a rear wheel steering device. While maintaining the efficiency of the rear wheel steering device as much as possible, the consumption of the electric storage unit is effectively suppressed. In a vehicle (10) having an ARS actuator (400) and an ARS driving device (500) as a rear wheel steering device, an ECU (100) executes ARS power saving control. In this control, when the rear wheel rotation angle δr is larger than the reference rotation angle δrth, the rotation angle deviation Δδr which is the difference between the target rear wheel rotation angle δrtg and the rear wheel rotation angle δr is larger than the reference deviation Δδrth and the continuation time is taken as the time during which this state continues On the condition that Tlst exceeds the reference value Tlstth, the power supply to the ARS actuator (400) is cut off.

Description

Controls for rear wheel steering

This divisional application is a divisional application of an invention patent application with application number 200980161399.9 and an application date of September 11, 2009. The invention title of this invention patent application is "control device for rear wheel steering device".

technical field

The present invention relates to the technical field of a control device for a rear wheel steering device that controls various rear wheel steering devices such as ARS (Active Rear Steering, active rear steering system).

Background technique

A rear wheel steering device that prevents transmission of driving force from the rear wheel side has been proposed (for example, refer to Patent Document 1). According to the rear wheel steering device for vehicles disclosed in Patent Document 1, by arranging a drive force transmission from the actuator side to the rear wheel side but preventing the opposite direction The worm and gear mechanism for driving force transmission and the irreversible clutch mechanism can reliably prevent the rotation angle of the rear wheel from changing.

In addition, in a technical field different from that of the rear-wheel steering device, an electric power steering device that reduces and corrects a drive current of a motor near a rudder angle end has also been proposed (for example, refer to Patent Document 2).

Patent Document 1: Japanese Patent Document No. 2003-237614;

Patent Document 2: Japanese Patent Document No. 2007-269070.

Contents of the invention

The problem to be solved by the invention

In a vehicle, sometimes the physical load for steering the rear wheels changes due to, for example, changes in driving conditions. Especially in the corner range near the corner end, this physical load tends to become significantly larger. In such a rotation angle range in which the physical load at the time of rotation angle control becomes large, the load required for the drive unit, such as an actuator, which can apply a steering force to the rear wheels to cause the rear wheels to turn increases, so that electric power is supplied to the actuator. The consumption of various power storage units such as batteries increases.

Patent Document 1 contains no description based on the above point of view, and it is impossible to suppress the consumption of such an electric storage unit. In addition, regardless of whether the technology described in Patent Document 2 can be applied to the rear wheel steering device, if the driving current is only reduced near the corner end as disclosed in Patent Document 2, the range in which the steering angle can be controlled will be changed from The initial range is reduced, and the effectiveness of the rarely available rear-wheel steering can be significantly reduced. That is, in the prior art including the technology disclosed in the above-mentioned patent documents, there is a problem that it is practically difficult to suppress consumption of the electric storage unit while maintaining the performance of the rear wheel steering device as much as possible.

The present invention was made in view of the above problems, and the problem to be solved is to provide a control device for a rear wheel steering device that can effectively suppress consumption of an electric storage unit while maintaining the performance of the rear wheel steering device as much as possible.

means of solving problems

In order to solve the above problems, the first control device of the rear wheel steering device according to the present invention is characterized in that the rear wheel steering device includes: a steering force providing unit capable of controlling the rear wheels of the vehicle according to the power-on state. providing a steering force that causes the rear wheels to turn; and an energization unit that can control the energization state; the control device includes: a target rotation angle setting unit that sets the rear wheel a target rotation angle of the wheel; an actual rotation angle determination unit, the actual rotation angle determination unit determines the actual rotation angle of the rear wheel; and an energization control unit, based on the set target rotation angle and the determined actual rotation angle control the energization unit so that the steering force is provided, and when the determined actual rotation angle is greater than or equal to a reference rotation angle and the deviation is greater than or equal to a reference deviation, control the energization unit so that The power supply to the steering force supply unit is cut off.

The first control device of the rear wheel steering device that the present invention relates to is the device that controls the rear wheel steering device that includes the steering force providing unit and the power supply unit, and for example, one or more CPUs (Central Processing Unit, central processing unit) can be used. , MPU (MicroProcessingUnit, microprocessor), various processors or various controllers, or various storage devices such as ROM (ReadOnlyMemory, read-only memory), RAM (RandomAccessMemory, random access memory), cache or flash memory, etc. Various processing units such as single or multiple ECUs (Electronic Controlled Units), various computer systems such as various controllers or microcomputer devices, etc.

The steering force supply unit according to the present invention is, for example, a unit using a so-called direct-acting actuator that can directly or indirectly convert the rotational power of the rotating electric machine into reciprocating motion in the axial direction without any other means, and It is a unit that can provide steering force for turning the rear wheels according to at least the energized state. Here, "energized state" refers to the details of various energized ways to the steering force providing unit, for example, including whether to energize, the timing of energized, the driving voltage, the driving current, the driving power or the driving duty ratio, etc., the "energized state" ” is in particular controlled by the energization unit in the present invention. The energization unit includes, for example, a wire harness, a cable, a connector, a terminal, a switch circuit, an inverter circuit, a relay circuit, or a PWM control circuit that is connected to the steering force supply unit in various ways such as physical, mechanical, electrical, or magnetic. Single or multiple physical, mechanical, electrical or magnetic units of a circuit etc.

According to the control device of the rear wheel steering device involved in the present invention, the target rotation angle of the rear wheels is set by the target rotation angle setting unit, and the power supply control unit is based on the set target rotation angle and the actual rotation angle of the rear wheels determined by the determination unit. To control the electrification unit to provide proper steering force to the rear wheels. At this time, the actual control method of the energization control unit is not limited as long as the deviation is at least used as a reference information in control, but as a preferred mode, the deviation can be used as a parameter to make the actual rotation angle follow the target. Various feedback controls such as PID control of the rotation angle, or feedforward control based on pre-adapted control conditions.

In addition, the "determination" involved in the present invention is a concept including detection, calculation, derivation, identification, acquisition, or selection. As long as it can be determined as reference information from the aspect of control, the actual method can be various. For example, the determination unit may be a detection unit such as a rotation angle sensor, or the actual rotation angle equivalent value output by the sensor may be obtained as an electrical signal from a detection unit such as a rotation angle sensor. In addition, what is determined may be the actual rotation angle, or may be an equivalent value of the actual rotation angle whose correspondence relationship with the actual rotation angle has been predetermined.

However, the energization control unit controls the steering force supply unit through the energization unit based on the deviation between the target rotation angle and the actual rotation angle, and basically continues to supply power through the energization unit as long as there is a deviation between the target rotation angle and the actual rotation angle.

On the other hand, if the factors other than the actual turning angle are the same, the steering force required to steer the rear wheels increases as the actual turning angle increases, and in most cases, the steering force is at the corner end and near the corner end. to the maximum in the region. In such a relatively large corner range, it is not uncommon for the steering force for making the actual corner angle follow the target corner angle to exceed various physical, mechanical or electrical limitations or limits of the steering force providing unit.

In this case, even if the energization is continued, the deviation between the actual rotation angle and the target rotation angle may not be reduced to a practically beneficial level at all. That is, in such a situation, waste of electric power resources that are difficult to contribute to reaching the target corner will continue. Such waste of power resources can become a disadvantage beyond the actual advantage of rear wheel angle control.

Therefore, in the control device of the rear wheel steering device involved in the present invention, when the determined actual rotation angle is greater than or equal to the reference rotation angle, and the deviation between the target rotation angle and the actual rotation angle is greater than or equal to the reference deviation, the energization control unit controls the energization unit, to cut off the power supply to the steering force supply unit.

At this time, the practical way to cut off the power supply is not particularly limited as long as the power consumption in the steering force supply unit does not significantly exist (that is, the power consumption does not have to be zero), and it can be done by a relay circuit or the like. Cutting off the electrical connection with various power storage units such as batteries can also substantially cut off the power supply through control aspects such as setting the driving duty ratio to zero.

The "deviation between the target rotation angle and the actual rotation angle" in the present invention is a value obtained by subtracting the actual rotation angle from the target rotation angle, and "the deviation is greater than or equal to the reference deviation" refers to a state where the actual rotation angle is smaller than the reference deviation from the target rotation angle. In addition, in the practical control method, a plus or minus sign is sometimes added according to the steering direction of the rear wheels. In this case, strictly speaking, the size relationship between the target rotation angle and the actual rotation angle may be reversed, and of course, in such a case, a judgment can be made in consideration of the above-mentioned purpose and purpose.

Here, the "reference deviation" as a judgment reference value for such a deviation is preferably based on experiments, experience, theory, simulation, etc. in advance and considers the power waste suppression effect and the practical advantages of rear wheel steering (these may deviate from each other). ) to determine a fixed or variable value.

When the reference deviation is too small, the power supply can be cut off even when no special load is applied to the steering force supply unit, and conversely, when the reference deviation is too large, the control for cutting the power supply does not occur at a practically beneficial frequency. start. Therefore, the reference deviation is preferably set so that it can be reliably judged that when the actual steering angle follows the target steering angle, the actual steering force, etc. Corners create a state of saturation.

In addition, the "reference rotation angle" which is a judgment reference value related to the actual rotation angle is a fixed or variable value set in consideration of the point where the size of the rotation angle corresponds to the magnitude of the load of the steering force providing unit, as described above, For example, it may be a relatively large value near the corner end. It should be added that in a relatively small corner area smaller than the reference corner angle, even if a static deviation occurs for some reason, the load on the steering force providing unit itself does not become large, and power waste is hardly noticeable enough to become a practical problem.

However, various electric auxiliary devices that need to be supplied with power for driving are installed in the vehicle, and the amount of power that can be supplied to the steering force supply unit may be affected due to the increase or decrease in the operating conditions of these electric auxiliary devices. When the amount of power supplied to the steering force supply unit is limited due to the above reasons, it is also likely that it will be difficult to reach the target angle of rotation. The influence of the electric power supply to the unit on the electric storage unit becomes relatively large. Therefore, the reference rotation angle is not limited to a value near the corner end, and may be a variable value depending on the state of the electric storage unit at that point in time, for example.

The energization control unit may add a time element to a judgment element when judging whether or not to cut off the power supply. For example, if the deviation does not change within a fixed or variable time range (that is, a state where a so-called static deviation occurs), measures such as comparing the deviation with a reference deviation may be taken.

In this manner, according to the control device for the rear wheel steering device according to the present invention, it is possible to avoid unnecessary power consumption that may occur when, for example, an excessive static deviation occurs between the actual steering angle and the target steering angle. That is, as long as the rear-wheel steering device can fully exert its performance practically, the power consumption is not cut off, and the consumption of the electric storage unit can be effectively suppressed while maintaining the performance of the rear-wheel steering device as much as possible.

In one aspect of the first control device of the rear wheel steering device according to the present invention, the steering force providing means is an actuator whose reverse efficiency is smaller than the forward efficiency.

In the case where the reverse efficiency is equal to or greater than the forward efficiency, the actuator may be driven by the reverse driving force input from the rear wheels in response to the road surface input, and the power supply related to the energization control unit Interdiction control can be hampered quite a bit. However, according to the configuration in which an actuator whose reverse efficiency is smaller than the forward efficiency as described above, and preferably the reverse efficiency is zero or less, is provided as the steering force supply unit, there is no such concern, so it is very useful in practice. Reduce power consumption for rear wheel steering.

In another aspect of the first control device of the rear wheel steering device according to the present invention, when the deviation is smaller than a predetermined return deviation in the state where the power supply is cut off, the energization control means restarts the power supply. supply.

According to this method, in the state where the power supply is cut off, for example, in the process of resetting the target rotation angle, if the target rotation angle changes to the decreasing side (ie, the neutral side) so that the deviation between the target rotation angle and the actual rotation angle is smaller than the deviation for restoration (The same value as the reference deviation is not excluded, but it is preferable to set a value in a region smaller than the reference deviation in consideration of the hysteresis of the control, etc.), so that the power supply can be quickly restarted. Therefore, it is practically useful to keep the rear-wheel steering device in an operating state as much as possible while preventing an excessive load from being applied to the electric storage unit.

The offset for restoration may be zero. In this case, the state in which the deviation is smaller than the deviation for restoration refers to the state in which the target angle of rotation is smaller than the actual angle of rotation, which is equivalent to the state in which the target angle of rotation exceeds the actual angle of rotation (that is, the control direction of the actual angle of rotation decreases transitionally or temporarily toward the actual angle of rotation. side reversed state). As described above, if the fact that the target rotation angle becomes smaller than the actual rotation angle is used as the power supply restart condition, since the control direction of the rotation angle is the neutral side with a light load, it is possible to reliably prevent the power storage unit from being overcharged immediately after restarting. load, thus being effective as a safer measure.

In order to solve the above-mentioned problems, the second control device of the rear wheel steering device according to the present invention is characterized in that the rear wheel steering device includes: a steering force providing unit that can control the rear wheels of the vehicle according to the power-on state. providing a steering force that causes the rear wheels to turn; and an energization unit capable of controlling the energization state, the control device including: a target rotation angle setting unit that sets the rear wheel The target rotation angle of the wheel; the actual rotation angle determination unit, the actual rotation angle determination unit determines the actual rotation angle of the rear wheel; the power-on control unit, the power-on control unit is based on the set target rotation angle and the determined actual rotation angle deviation to control the energization unit so that the steering force is provided; and an actual rotation angle setting unit that, when the determined actual rotation angle is greater than or equal to a reference rotation angle and the deviation is greater than or equal to a reference deviation, the An actual rotation angle setting unit sets the set target rotation angle as an actual rotation angle specifying the deviation.

According to the second control device of the rear wheel steering device according to the present invention, different from the first control device of the rear wheel steering device, when the actual rotation angle is greater than or equal to the reference rotation angle, and the deviation is greater than or equal to the reference deviation, the actual rotation angle The setting unit sets the target rotation angle at this point in time as the actual rotation angle with a predetermined deviation. That is, according to the second rear-wheel steering apparatus related to the present invention, the deviation between the target angle of rotation and the actual angle of rotation is the deviation between the target angles of rotation, that is, zero (in addition, since the target angle of rotation is replaced by the actual angle of rotation with the specified deviation, so when determining When there is a deviation, the substituted actual rotation angle is used instead of the determined actual rotation angle).

Therefore, as an actual phenomenon, even if the rotation angle of the rear wheels does not follow the target rotation angle, it is considered that the rotation angle of the rear wheels follows the target rotation angle in terms of control. Therefore, the electric power taken out from the energization means (that is, the steering force supplied from the steering force supplying means) is a small value corresponding to the electric power at the time of target convergence, and waste of electric power resources can be preferably avoided.

In order to solve the above-mentioned problems, the third control device of the rear wheel steering device according to the present invention is characterized in that the rear wheel steering device includes: a steering force providing unit that can control the rear of the vehicle according to the power-on state. wheel to provide a steering force that causes the rear wheels to turn; and an energization unit that can control the energization state; the control device includes: a target rotation angle setting unit that sets the the target rotation angle of the rear wheels; the actual rotation angle determination unit, the actual rotation angle determination unit determines the actual rotation angle of the rear wheels; the power-on control unit, the power-on control unit is based on the set target rotation angle and the determined actual rotation angle a deviation to control the energization unit so that the steering force is provided; and a bias angle setting unit, when the determined actual rotational angle is greater than or equal to a reference rotational angle and the deviation is greater than or equal to a reference deviation, The offset angle setting unit sets an offset angle that should be added to the determined actual rotation angle according to the deviation; wherein the energization control unit is based on the deviation between the corrected rotation angle and the set target rotation angle to control the energizing unit, and the corrected rotation angle is a rotation angle obtained by adding the determined actual rotation angle and the set offset angle.

The third control device of the rear wheel steering device involved in the present invention is similar to the second control device of the above-mentioned rear wheel steering device. When the actual rotation angle is greater than or equal to the reference rotation angle and the deviation is greater than or equal to the reference deviation, set The unit sets the offset angle to be added to the actual rotation angle determined by the determination unit based on the deviation. That is, its performance is the same as that of the above-mentioned control device of the second rear wheel steering device, and the deviation between the target rotation angle and the determined actual rotation angle is eliminated in the control. Therefore, similarly to the second control device of the rear wheel steering device, waste of electric power resources can be well avoided.

In one aspect of the second or third control device of the rear wheel steering device according to the present invention, a reference deviation setting unit is further included, the reference deviation setting unit sets the base deviation.

According to this aspect, the reference deviation is set by the reference deviation setting means based on the state quantity of the vehicle. Here, the "state quantity of the vehicle" refers to a state quantity in the vehicle whose correspondence relationship with the load of the steering force providing unit is prescribed in advance based on experiments, experience, theory, simulation, etc., and by setting a reference deviation based on this state quantity, It can be judged more accurately whether or not the waste of electric power self-source occurs.

In this aspect, the predetermined state quantity of the vehicle may include at least one of the speed of the vehicle, the actual turning angle of the rear wheels, and the lateral acceleration of the vehicle.

The load required to steer the rear wheels decreases as the vehicle speed increases, increases as the actual steering angle increases, and increases as the lateral acceleration increases. That is, these are suitable as the state quantities of the vehicle described above, and if the reference deviation is set in consideration of these, it is possible to more accurately determine whether electric power resources are wasted.

In another mode of the third control device of the rear wheel steering device according to the present invention, when the set target steering angle increases, the bias angle setting unit adjusts the bias angle according to the increase amount. Make incremental corrections.

According to this aspect, when the target steering angle of the rear wheels increases (that is, when the steering operation is performed further toward the end of the steering angle), the offset angle is corrected to the increasing side according to the increase amount. Therefore, waste of electric power resources can be reliably suppressed.

In another aspect of the third control device of the rear wheel steering device according to the present invention, when the set target steering angle increases, the bias angle setting unit adjusts the The above offset angle is corrected for reduction.

According to this aspect, when the target steering angle of the rear wheels increases (that is, when the steering wheel is turned further toward the extreme side of the steering angle), the offset angle is corrected to decrease according to the state quantity of the vehicle. The load required for rear wheel steering may be reduced depending on the state quantity of the vehicle (as described above, for example, vehicle speed, cornering angle, lateral acceleration, etc. may be appropriately included). In this case, no waste of electric power resources occurs, and the actual turning angle can be made to further follow the target turning angle. Thus, as described above, by correcting the bias angle to the decreasing side, it is possible to obtain as much practical advantage related to rear wheel steering as possible.

In another form of the third control device of the rear wheel steering device according to the present invention, when the set target angle of rotation is smaller than the determined actual angle of rotation, the offset angle setting unit The offset angle is corrected for reduction.

According to this aspect, when the target angle of rotation is smaller than the determined actual angle of rotation (that is, when the target angle of rotation exceeds the actual angle of rotation in the direction opposite to the direction of the corner end), the set offset angle is corrected to decrease. In addition, as one of the preferred ways, such an offset angle is set to zero. Therefore, from the viewpoint of avoiding waste of electric power resources, the restriction imposed on the rear-wheel steering device can be eliminated as far as possible in advance, and the practical advantages related to rear-wheel steering can be obtained to the greatest extent.

In another aspect of the first, second, or third control device of the rear wheel steering device according to the present invention, the target rotation angle setting unit sets the target rotation angle based on a predetermined state amount in the vehicle or a driver's steering amount. the target corner.

According to this aspect, for example, the target steering angle is set based on various driver steering quantities such as steering torque, steering angle, or steering angular velocity, or various vehicle state quantities as described above. Therefore, the target steering angle can be reliably set, and the Optimum efficiency of the rear wheel steering. Said configuration, in such a structure capable of optimally driving the rear wheel steering device, has the practical advantage of avoiding waste of electric power resources, and at the same time can obtain very desirable effects.

These actions and other advantages of the present invention will become clearer through the embodiments described below.

Description of drawings

FIG. 1 is a schematic configuration diagram schematically showing the configuration of a vehicle according to a first embodiment of the present invention;

FIG. 2 is a schematic characteristic diagram showing changes in rear wheel rotation angle and ARS drive current with time in the vehicle of FIG. 1;

FIG. 3 is a flowchart of basic control executed in the vehicle of FIG. 1 .

Label description

FL, FR...wheels, 10...vehicle, 11...steering wheel, 12...upper steering shaft, 13...lower steering shaft, 14...pinion, 16...steering angle sensor , 17...Steering torque sensor, 18...Rotation angle sensor, 100...ECU, 200...EPS actuator, 300...EPS driving device, 400...ARS actuator, 410.. .Rear wheel steering stem, 500...ARS drive unit.

detailed description

Hereinafter, various embodiments of a control device for a rear wheel drive device according to the present invention will be described with reference to the drawings as appropriate.

<First Embodiment>

<Structure of Embodiment>

First, the configuration of a vehicle 10 according to a first embodiment of the present invention will be described with reference to FIG. 1 . Here, FIG. 1 is a schematic configuration diagram schematically showing a basic configuration of a vehicle 10 .

In FIG. 1 , a vehicle 10 has a pair of left and right front wheels FL and FR as steered wheels, and is configured to be able to travel in a desired direction by being steered by these front wheels. In addition, in the vehicle 10 , the pair of left and right rear wheels RL and RR are also steered wheels, and the turning motion of the vehicle is assisted by steering these rear wheels, thereby stabilizing the behavior of the vehicle. Vehicle 10 is an example of a “vehicle” according to the present invention including ECU 100 , EPS actuator 200 , EPS drive device 300 , ARS actuator 400 , and ARS drive device 500 .

ECU 100 is an electronic control unit including CPU, ROM, and RAM (not shown), configured to control the overall operation of vehicle 10 , and is an example of the "rear steering device control device" according to the present invention. ECU 100 is configured to execute ARS power saving control described later in accordance with a control program stored in ROM.

In addition, the ECU 100 is an integrated electronic control unit configured to function as an example of each of the "target rotation angle setting unit", the "actual rotation angle determination unit", and the "power supply control unit" according to the present invention. The related operations are all configured to be executed by ECU 100 . However, the physical structure, mechanical structure and electrical structure of these various units involved in the present invention are not limited thereto. For example, these various units can also be constituted as a plurality of ECUs, various processing units, various controllers or microcomputer devices. and other computer systems.

In the vehicle 10, the steering input (that is, as an example of the "driver's steering amount" according to the present invention) given from the driver via the steering wheel 11 is transmitted to the upper steering shaft 12, which is connected to the steering wheel. 11 is coaxially rotatably coupled so as to be rotatable in the same direction as the steering wheel 11 . The upper steering shaft 12 is coupled to the lower steering shaft 13 at its downstream end via a steering torque sensor 16 .

The steering torque sensor 16 is a sensor configured to detect a driver's steering torque MT supplied from the driver via the steering wheel 11 . The upper steering shaft 12 is connected to the lower steering shaft 13 via a not-shown torsion bar. Rings for detecting a rotational phase difference are fixed to both upstream and downstream ends of the torsion bar. The torsion bar has a structure that is twisted in its rotational direction according to the steering torque transmitted via the upstream portion of the upper steering shaft 12 (ie, driver steering torque MT) when the driver of the vehicle 10 operates the steering wheel 11, and It is configured so that the steering torque can be transmitted to the downstream portion while generating this torsion. Therefore, when the steering torque is transmitted, a rotational phase difference is generated between the aforementioned rings for detecting the rotational phase difference. The steering torque sensor 16 is configured to detect the rotational phase difference, convert the rotational phase difference into a steering torque, and output it as an electrical signal corresponding to the steering torque MT. In addition, the steering torque sensor 16 is electrically connected to the ECU 100 , and the detected steering torque MT is referenced by the ECU 100 at a fixed or irregular cycle.

The steering angle sensor 17 is an angle sensor configured to detect a steering angle MA indicating the amount of rotation of the upper steering shaft 12 . The steering angle sensor 17 is electrically connected to the ECU 100 , and the detected steering angle MA is referenced by the ECU 100 at a fixed or irregular cycle.

The rotation of the lower steering shaft 13 is transmitted to the rack and pinion mechanism. The rack and pinion mechanism is a steering force transmission mechanism that includes a pinion 14 connected to the downstream side end of the lower steering shaft 13, and a tooth formed with gear teeth meshing with the gear teeth of the pinion. bar 15. In this rack and pinion mechanism, the rotation of the pinion 14 is converted into the movement of the rack bar 15 in the horizontal direction in the drawing, and the steering force is passed through the tie rods and knuckles connected to both ends of the rack bar 15 (omitted). Reference numerals) are transmitted to each steering wheel. That is, a so-called rack and pinion steering system is implemented in the vehicle 10 .

The EPS actuator 200 has an EPS motor as a DC brushless motor including a rotor (not shown) as a rotating member to which permanent magnets are attached, and a stator as a stationary member surrounding the rotor. This EPS motor is configured such that a rotor is rotated by a rotating magnetic field formed in the EPS motor by energizing the stator through the EPS drive device 500 , thereby generating assist torque TA in the direction of rotation of the rotor.

On the other hand, a reduction gear (not shown) is fixed to a motor shaft serving as a rotation shaft of the EPS motor, and this reduction gear also meshes with the pinion gear 14 . Therefore, the assist torque TA generated by the EPS motor functions as assist torque for assisting the rotation of the pinion gear 14 . The pinion gear 14 is connected to the lower steering shaft 13 as described above, and the lower steering shaft 13 is connected to the upper steering shaft 12 . Accordingly, the driver's steering torque MT applied to the upper steering shaft 12 is appropriately assisted by the assist torque TA to be transmitted to the rack bar 15 , thereby reducing the driver's steering load.

The EPS drive device 300 is an electric drive circuit including a PWM circuit, a transistor circuit, an inverter, and the like configured to be able to energize a stator of an EPS motor. The EPS driving device 300 is electrically connected to a battery (not shown), and is configured to supply a driving voltage to the EPS motor by electric power supplied from the battery. In addition, EPS drive device 300 is electrically connected to ECU 100 , and its operation is controlled by ECU 100 .

The ARS actuator 400 is a known direct-acting actuator, and this direct-acting actuator has an ARS motor as a DC brushless motor and a conversion mechanism that converts the rotational motion of the ARS motor into the linear motion in the left and right directions shown in the figure, The DC brushless motor includes a rotor (not shown) as a rotating member to which permanent magnets are attached, and a stator as a stationary member surrounding the rotor. The ARS actuator 400 is an example of the "steering force providing means" according to the present invention. This ARS motor is configured such that a rotor rotates under the action of a rotating magnetic field formed in the ARS motor by energizing the stator via the ARS drive device 500 , thereby generating torque.

Here, the ARS actuator 400 is connected to the rear wheel steering rod 19 . The rear wheel steering lever 19 is configured to be driven in the left and right directions as shown in the drawing according to the steering force in the left and right directions shown in the figure generated as a result of the conversion of the rotational motion of the ARS motor into a linear motion, and has two positions in the left and right directions. The structure in which the ends are connected to the left and right rear wheels via a steering knuckle or the like. Therefore, through the ARS actuator 400, the rotation angles of the rear wheels RL and RR can be changed within the range of δrmax--δrmax (the plus and minus signs are attached for the convenience of control, indicating the right steering direction or the left steering direction).

A rotation angle sensor 18 capable of detecting a rear wheel rotation angle δr (δr is equal to the left and right sides) which is the rotation angle of each rear wheel is arranged on the rear wheel steering lever 19 . The rotation angle sensor 18 is electrically connected to the ECU 100 , and the detected rear wheel rotation angle δr is referenced by the ECU 100 at a fixed or irregular cycle.

The reverse efficiency of the ARS actuator 400 (i.e., the efficiency with which the ARS actuator is driven by providing reverse power from each rear wheel to the ARS actuator 400) is less than the forward efficiency (i.e., the Efficiency of being driven by supplying standard power to each rear wheel) and is less than or equal to zero. Therefore, the ARS actuator 400 is basically not driven by power input from the rear wheels caused by road surface disturbance, road surface input, or road surface friction.

The ARS drive device 500 is an electric drive circuit including a PWM circuit, a transistor circuit, and an inverter configured to energize the stator of the ARS motor, and is an example of the "energization unit" according to the present invention. The ARS driving device 500 is electrically connected to a battery (not shown), and is configured to supply a driving current Idars to the ARS motor using electric power supplied from the battery. In addition, the ARS drive device 500 is electrically connected to the ECU 100 , and its operation is controlled by the ECU 100 . In this way, in the vehicle 10 according to the present embodiment, the ARS actuator 400 and the ARS drive device 500 constitute an example of the "rear wheel drive device" according to the present invention.

<Operation of Embodiment>

<Control of ARS Actuator 400>

In vehicle 10 , the operating state of ARS actuator 400 is controlled by ECU 100 . First, the ECU 100 sets the target rear wheel angle δrtg (that is, the target rear wheel angle δrtg as the target value of the rear wheel angle) based on the steering angle MA detected by the steering angle sensor 17 and the vehicle speed V as the speed of the vehicle 10 An example of a target corner for ”). At this time, the ECU 100 refers to a target rear wheel rotation angle map stored in the ROM in advance with the steering angle MA and the vehicle speed V as parameters. In the target rear wheel angle map, one target rear wheel angle δrtg is associated with these parameters, and the ECU 100 is configured to selectively acquire the target rear wheel angle δrtg corresponding to the steering angle MA and the vehicle speed V at that point in time.

In addition, although not shown in FIG. 1 , various sensors necessary for vehicle behavior control are installed in the vehicle 10 , and the vehicle speed V is detected by a vehicle speed sensor as one of them. The vehicle speed sensor is electrically connected to the ECU 100 , and the detected vehicle speed V is referenced by the ECU 100 at a fixed or irregular cycle. In addition, similarly, the vehicle 10 has a lateral acceleration sensor capable of detecting the lateral acceleration Gy of the vehicle 10 .

After the target rear wheel rotation angle δrtg is set, the ECU 100 controls the ARS driving device in the form of the feedback rotation angle deviation Δδr (that is, an example of the "deviation between the set target rotation angle and the determined actual rotation angle" involved in the present invention) 500 , the rotation angle deviation Δδr is obtained by subtracting the rear wheel rotation angle δr detected by the rotation angle sensor 18 from the set target rear wheel rotation angle δrtg. By supplying the driving current Idars from the ARS driving device 500, the ARS motor of the ARS actuator 400 is driven, and the steering force that causes the rear wheels RL and RR to turn is supplied to the rear wheels RL and RR through the rear steering rod 19, so that each rear wheel driven.

<Details of ARS power saving control>

Next, problems in the actual control of the structure including the ARS actuator 400 and the ARS driving device 500 will be described with reference to FIG. 2 . Here, FIG. 2 is a schematic characteristic diagram showing an example of the course of changes with time of the rear wheel rotation angle δr and the ARS drive current Idars.

In FIG. 2 , the time course of the rear wheel rotation angle δr is shown with a solid line at the top, and the time course of the drive current Idars of the ARS actuator 400 is shown with a solid line at the bottom. Here, it is assumed that at time T0, the control of the rear wheel angle δr is started, and the rear wheel angle δr starts to follow the target rear wheel angle δrtg from the neutral position NTL in a steering direction (refer to the dotted line in the figure, the temporary The period is basically the same as the actual rotation angle δr).

However, since the steering force required for rear wheel steering varies depending on the running conditions of the vehicle 10 , it may exceed the load range of the ARS actuator 400 in some cases. In such a load range, the deviation between the target rear wheel rotation angle δrtg and the rear wheel rotation angle δr, that is, the rotation angle deviation Δδr is not eliminated but remains as a static deviation. FIG. 2 shows this situation, and in the time region from time T1 to time T2, such a phenomenon occurs.

On the other hand, since the driving current Idars is basically determined based on the rotational angle deviation Δδr, the value of the driving current Idars increases when the rotational angle deviation Δδr remains as a static deviation as described above. However, no matter how much power is obtained from the battery via the ARS drive device 500 , the rear wheel rotation angle δr does not change when the load required to steer the rear wheels exceeds the physical or electrical limit of the ARS actuator 400 as described above. As a result, a significant waste of power resources can result compared to the performance of an actual ARS actuator 400 . In this embodiment, such waste of power resources can be well avoided by ARS power saving control.

Here, details of the ARS power saving control will be described with reference to FIG. 3 . Here, FIG. 3 is a flowchart of the ARS power saving control.

In FIG. 3 , the ECU 100 determines whether or not the rear wheel rotation angle δr is larger than a reference rotation angle δrth (step S101 ). In Figure 3, the absolute value of the rear wheel rotation angle δr is used, but this is only because of the fact that the sign on the control is taken into account. Since there is basically no positive or negative area in the steering direction, conceptually Only compare the rear wheel rotation angle δr with the reference rotation angle δrth. Here, the reference rotation angle δrth defined for the rear wheel rotation angle δr is an appropriate value set in the vicinity of the approximate rotation angle end (ie, the aforementioned δrmax).

When the rear wheel rotation angle δr is less than or equal to the reference rotation angle δrth (step S101: No), the ECU 100 executes step S101 at a fixed cycle, and substantially puts the processing in a waiting state. On the other hand, when the rear wheel rotation angle δr is greater than the reference rotation angle δrth (step S101: Yes), the ECU 100 also determines whether the rotation angle deviation Δδr is greater than the reference deviation Δδrth, and whether the continuation time Tlst exceeds the reference value Tlstth, and the continuation time Tlst is the rotation angle deviation The time value for which the state in which Δδr is greater than the reference deviation Δδrth continues (step S102).

The continuation time Tlst has a built-in timer that starts counting from the time point when the rotation angle deviation Δδr exceeds the reference deviation Δδrth first, and performs cumulative counting as long as the state in which the rotation angle deviation Δδr exceeds the reference deviation Δδrth continues.

When the rotation angle deviation Δδr is less than or equal to the reference deviation Δδrth, or when the rotation angle deviation Δδr is greater than the reference deviation Δδrth but the continuation time Tlst has not exceeded the reference value Tlstth (step S102: No), the ECU 100 returns the process to step S101 and repeats a series of processes .

On the other hand, when the rotation angle deviation Δδr exceeds the reference deviation Δδrth, and this state continues for a period longer than the reference value Tlstth (step S102: Yes), that is, when it is judged that the rotation angle deviation Δδr is of such a degree that the power resource can be wasted When there is a static deviation, the ECU 100 controls the ARS drive device 500 to cut off the supply of the drive current Idars to the ARS actuator 400 (step S103 ).

When the supply of the driving current Idars is cut off, the ECU 100 judges whether the steering angle deviation Δδr is smaller than the threshold A, and whether the target rear wheel steering angle δrtg is smaller than the rear wheel steering angle δr, that is, it is judged that the target rear wheel steering angle δrtg is in the direction opposite to the direction of the corner end (i.e. , neutral direction) changes and crosses the rear wheel angle δr and whether the deviation Δδr is smaller than the threshold A (step S104 ).

When the steering angle deviation Δδr is greater than or equal to the threshold A, or the target rear wheel rotation angle δrtg is greater than or equal to the rear wheel rotation angle δr (step S104: No), the ECU 100 keeps the drive current cut off, and when the rotation angle deviation Δδr is smaller than the threshold A and the target rear wheel rotation angle When the rotation angle δrtg is smaller than the rear wheel rotation angle δr (step S104: Yes), the ECU 100 restarts the supply of the drive current Idars (step S105). After step S105 is executed, the process returns to step S101 to repeat a series of processes. ARS power saving control is performed as described above.

In step S104, two different judging conditions are set regarding the restoration of the driving current. The latter part of the judging condition, that is, whether the target rear wheel rotation angle δrtg is smaller than the rear wheel rotation angle δr, is nothing more than whether the rotation angle deviation Δδr is smaller than zero. Therefore, both zero and the threshold value A are values that can function as an example of the "variation for restoration" according to the present invention, and the same advantage can be obtained even if only one of the judgment conditions is used.

However, if both are used as a compound condition as in the present embodiment, it is basically possible to restart the power supply when the target rear wheel angle δrtg falls below the actual angle δr, and it is possible to prevent, for example, It is effective as a safety measure to restart the supply of the drive current when the amount of change is too large, the load required by the ARS actuator 400 does not decrease, or the like.

Thus, according to the ARS power-saving control according to the present embodiment, when the load required by the ARS actuator 400 is so high that the rotation angle deviation Δδr cannot be reduced, the supply of the drive current Idars to the ARS actuator 400 is cut off.

Here, in particular, the ARS actuator 400 is an actuator whose reverse efficiency is less than or equal to zero, and the rear wheel rotation angle δr is not changed by the reverse input from the rear wheels as steered wheels in a state where the supply of the drive current Idars is cut off. Return to neutral position NTL (exactly δr=0). Therefore, the advantage of the rear wheel steering provided by the ARS actuator 400 will not be hindered by the exchange of the power saving effect, and the limited power resource accumulated in the battery can be realized while maintaining the performance of the rear wheel steering as much as possible. use efficiently.

The reference deviation Δδrth referenced in step S102 may be an experimentally appropriate fixed value, or may be a variable value set each time based on the vehicle speed V, lateral acceleration Gy, and rear wheel angle δr at that point in time.

That is, the load required by the ARS actuator 400 when turning the rear wheels changes according to the state of the vehicle 10 . For example, in a high vehicle speed range, since the friction between the rear wheels and the road surface decreases, basically the load required for steering the rear wheels becomes smaller. In this case, the reference deviation Δδrth can be set relatively large, and the frequency at which the power supply is cut off can be reduced. The same applies to the rear wheel rotation angle δr and the lateral acceleration Gy. Since the larger the rear wheel rotation angle δr and the lateral acceleration Gy are, the greater the load, it is preferable to set the reference deviation Δδrth relatively small.

These various state quantities are an example of the "state quantity of the vehicle" involved in the present invention, and the corresponding relationship between each state quantity and the reference deviation Δδrth can be determined in advance based on experiments, experience, theory or simulation, etc., so that after maintaining as much as possible While maintaining the efficiency of the wheel drive, it is possible to reliably avoid wasting or depleting the battery.

<Second Embodiment>

In the first embodiment, power waste can be avoided by cutting off the power supply to the ARS actuator 400 , but the power saving effect can also be realized by other control methods. Next, the ARS power saving control according to the second embodiment will be described. Most of the ARS power saving control according to the second embodiment is the same as the ARS power saving control according to the first embodiment illustrated in FIG. 3 , and will be described here with reference to the existing FIG. 3 . The structure of the vehicle related to the second embodiment is assumed to be the same as that of the first embodiment.

In the ARS power-saving control according to the second embodiment, when the judgment condition in step S102 is satisfied (step S102: Yes), ECU 100 replaces the rear wheel rotation angle δr detected by rotation angle sensor 19 with the target at that point in time. The rear wheel rotation angle δrtg is set as the rear wheel rotation angle δr.

After the replacement processing of the rear wheel angle δr is completed, the ECU 100 continues the normal drive control of the ARS actuator 400 . That is, in this case, since the rotation angle deviation Δδr becomes zero, the ARS 400 is not provided with a driving force that wastes power resources, and the consumption of power resources stored in the battery can be reduced favorably.

<Third Embodiment>

The same effects as those of the second embodiment can also be achieved by other controls. Here, such ARS power saving control will be described as a third embodiment of the present invention. Most of the ARS power saving control according to the third embodiment is the same as the ARS power saving control according to the first embodiment illustrated in FIG. 3 , and will be described here with reference to the existing FIG. 3 . The structure of the vehicle related to the third embodiment is assumed to be the same as that of the first embodiment.

In the ARS power saving control according to the third embodiment, when the judgment condition in step S102 is satisfied (step S102: YES), ECU 100 sets an offset rotation angle δrofs corresponding to the rotation angle deviation Δδr at that point in time. The offset rotation angle δrofs is an example of the "offset angle" involved in the present invention. When the offset rotation angle δrofs is thus set, the ECU 100 adds the set offset rotation angle δrofs to the rear wheel rotation angle δr to update the rear wheel rotation angle δr. As a result, similar to the second embodiment, the rotation angle deviation Δδr becomes zero, and the power output from the battery is suppressed. The offset rotation angle δrofs does not necessarily have to be a value equivalent to the rotation angle deviation Δδr.

In the third embodiment, when the target rear wheel angle δrtg increases (that is, when a request for further steering operation toward the corner end is generated), the bias may also be increased according to the increase amount of the target rear wheel angle δrtg Turning angle δrofs. Thereby, the feedback control corresponding to the rotation angle deviation Δδr can always be in a convergent state, and it is possible to reliably avoid unnecessary output of electric power from the battery.

On the other hand, in the third embodiment, it is also possible to reduce (release) the offset rotation angle δrofs according to the situation. That is, as described above regarding the steering angle deviation Δδr, the load on the ARS actuator 400 side required for rear wheel steering increases according to the state quantities of the vehicle 10 (for example, the vehicle speed V, the rear wheel angle δr, and the lateral acceleration Gy). reduce. Using this, for example, the offset angle of rotation δrofs can also be reduced in the high vehicle speed range. At this time, the timing at which the offset rotation angle δrofs decreases may be made variable, and the speed at which the offset rotation angle δrofs decreases may also be made variable.

In addition, similarly, for example, when the target rear wheel angle δrtg is smaller than the rear wheel angle δr (for example, when the determination condition related to step S104 is satisfied), it may be determined that there is no need for power saving, and in this case , and the offset rotation angle δrofs can also be reduced and corrected. In this case, since the ARS actuator 400 can perform normal rear wheel steering control, it is preferable that the offset rotation angle δrof can also be set to zero.

The present invention is not limited to the above-described embodiments, and can be appropriately changed within the range not departing from the gist or concept of the invention that can be read from the claims and the specification as a whole, and the control device of the rear wheel steering device accompanying such a change is also included. Within the technical scope of the present invention.

Industrial availability

The present invention is applicable to the control of a rear wheel steering device capable of steering the rear wheels of a vehicle.

Claims (4)

1. a control setup for apparatus for rear wheel steering, is characterized in that,

Described apparatus for rear wheel steering comprises:

Steering effort providing unit, described steering effort providing unit can provide according to the trailing wheel of "on" position to vehicle the steering effort impelling described rear-axle steering; And

Energising unit, described energising unit can control described "on" position;

Described control setup comprises:

Target rotation angle setup unit, described target rotation angle setup unit sets the target rotation angle of described trailing wheel;

Actual rotational angle determining unit, described actual rotational angle determining unit determines the actual rotational angle of described trailing wheel;

Energising control unit, described energising control unit controls described energising unit based on the target rotation angle of setting with the deviation of the actual rotational angle determined, is provided to make described steering effort; And

Actual rotational angle setup unit, when the described actual rotational angle determined is more than or equal to benchmark corner and described deviation is more than or equal to datum drift, the target rotation angle of described setting is set as the actual rotational angle specifying described deviation by described actual rotational angle setup unit.

2. the control setup of apparatus for rear wheel steering as claimed in claim 1, it is characterized in that, described control setup also comprises datum drift setup unit, and described datum drift setup unit sets described datum drift according to the specified states amount in described vehicle.

3. the control setup of apparatus for rear wheel steering as claimed in claim 2, is characterized in that,

Specified states amount in described vehicle comprises at least one in the transverse acceleration of the speed of described vehicle, the actual rotational angle of described trailing wheel and described vehicle.

4. the control setup of apparatus for rear wheel steering as claimed in claim 1, is characterized in that,

Described target rotation angle setup unit sets described target rotation angle based on the specified states amount in described vehicle or chaufeur steering volume.