JP4127132B2 - Electric power steering device for vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus, and more particularly to an electric power steering apparatus.
[0002]
[Prior art]
As one of electric power steering devices for vehicles such as automobiles, for example, as described in Patent Document 1 below, an electric motor configured to gradually decrease the control current of the power steering device when the power supply voltage decreases. A power steering apparatus is conventionally known.
[0003]
According to such an electric power steering device, the steering assist torque is gradually reduced by gradually reducing the control current of the power steering device when the power supply voltage is lowered, so that the operation of the power steering device is stopped when the power supply voltage is lowered. Compared with the case where it is done, the steering feeling at the time of the fall of a power supply voltage can be improved.
[Patent Document 1]
JP 2000-198457 A
[0004]
[Problems to be solved by the invention]
However, in the conventional electric power steering apparatus as described above, since the entire control current of the power steering apparatus is gradually reduced when the power supply voltage is lowered, the steering assist torque is lowered when the power supply voltage is lowered. There is an inevitable problem that the force increases and the driver's steering burden increases, especially when other electric devices that require a large current are activated in a situation where the power supply voltage is lowered. Therefore, there is a problem that the steering assist torque rapidly decreases and the driver's steering burden increases rapidly without a gradual decrease in the control current.
[0005]
The present invention has been made in view of the above-described problems in the conventional electric power steering apparatus configured so that the control current of the power steering apparatus is gradually reduced when the power supply voltage is lowered. The main problem is that, in general, the target control current of the power steering device is calculated based on the sum of the basic assist control amount based on the steering torque and the auxiliary control amount for improving the steering feeling. In the power steering system, paying attention to the fact that these control amounts are uniformly reduced without being distinguished, control is performed while securing the basic assist control amount as much as possible when the power supply voltage drops or there is a risk. By reducing the current, the steering assist torque is reduced in a situation where the power supply voltage drops or is likely to be reduced. Cormorant it is to suppress the steering increase of the steering burden of the driver due to the increase of the reaction force.
[0006]
[Means for Solving the Problems]
According to the present invention, the main problem described above is the structure of claim 1, that is, the steering assist torque generating means for generating the steering assist torque according to the control current, the basic assist control amount based on the steering torque, and the steering feeling. And a control means for calculating a target control current based on the sum of the auxiliary control amount for improving the control and for controlling the control current supplied from the power source to the steering assist torque generating means based on the target control current. In the electric power steering apparatus, the control means determines whether or not there is a voltage drop or the risk of the power supply. When it is determined that there is a voltage drop or the risk of the power supply, the auxiliary means is more than the basic assist control amount. This is achieved by a vehicular electric power steering apparatus characterized by preferentially reducing the control amount.
[0007]
According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the control means increases the voltage drop amount of the power supply or the risk thereof. The reduction amount of the auxiliary control amount is configured to be increased (configuration of claim 2).
[0008]
According to the present invention, in order to effectively achieve the above main problems, in the configuration of claim 1 or 2, the control means is another electric motor driven by a current supplied from the power source. The apparatus is configured to determine that there is a risk of a voltage drop of the power supply when the possibility of operation of the apparatus is high.
[0009]
According to the present invention, in order to effectively achieve the above main problem, in the configuration of the above-described third aspect, the other electric device is the power source when a vehicle collides or there is a risk of the collision. It is comprised so that it may be a collision influence reduction apparatus driven by the electric current supplied more (structure of Claim 4).
[0010]
Further, according to the present invention, in order to effectively achieve the above main problems, in the configuration of the above-described claim 4, when there is a possibility of collision of the vehicle, the control means sets the time until the vehicle collision. It is determined that the shorter the shorter, the higher the possibility of the voltage drop of the power supply being higher, and the reduction amount of the auxiliary control amount is increased (configuration of claim 5).
[0011]
According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 4 or 5, the collision effect reducing device is configured to increase the tension of the seat belt. (Structure of claim 6).
[0012]
Further, according to the present invention, in order to effectively achieve the main problems described above, in the configurations of claims 1 to 6, the auxiliary control amount is a control amount that reduces the influence of steering inertia or a steering amount. It is comprised so that the control amount which reduces the influence of the frictional force at the time may be included (structure of Claim 7).
[0013]
According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 7, when the control means has a voltage drop of the power supply or there is a risk of the voltage drop, the power supply voltage The control amount for reducing the influence of the frictional force during the steering is prioritized and reduced over the control amount for reducing the influence of the inertia of the steering in accordance with the amount of reduction or the degree of fear thereof (claim). Configuration of Item 8).
[0014]
According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 7 or 8, the auxiliary control amount is a control amount that reduces the influence of steering inertia or a steering amount. A control amount for reducing the influence of the frictional force at the time of driving and a control amount for improving the damping property at the time of steering. It is comprised so that the control amount which improves attenuation | damping property may not be reduced (structure of Claim 9).
[0015]
[Action and effect of the invention]
According to the configuration of the first aspect, the target control current is calculated based on the sum of the basic assist control amount based on the steering torque and the auxiliary control amount for improving the steering feeling, and the power source is calculated based on the target control current. In a vehicular electric power steering apparatus in which a control current supplied to a steering assist torque generating means is controlled, it is determined whether or not there is a voltage drop or a risk of the power supply, and there is a risk of a voltage drop or a risk of the power supply. Since the auxiliary control amount is reduced in preference to the basic assist control amount, the basic assist control amount is prevented from lowering in a situation where there is a risk of power supply voltage drop or there is a risk of this. The necessary steering assist torque is generated as much as possible while suppressing the further decrease in the voltage of the driver, and the driver's steering burden due to the increase in the steering reaction force is reduced. It is possible to effectively suppress a large.
[0016]
Further, according to the configuration of the second aspect, the amount of decrease in the auxiliary control amount is increased as the amount of decrease in the voltage of the power source or the risk thereof is higher. As a result, the electric power consumed by the electric power steering device can be reduced, thereby reducing the power supply voltage while preventing the power supply voltage from dropping or suddenly deteriorating the steering feeling at the stage where the fear has occurred. Reduction can be effectively suppressed.
[0017]
Further, according to the configuration of the third aspect, since it is determined that there is a possibility that the voltage of the power supply is lowered when there is a high possibility that the other electric device driven by the current supplied from the power supply is activated. Due to the operation of the electric device, it is possible to effectively reduce the possibility that the power supply voltage temporarily decreases suddenly and the steering assist torque generated by the electric power steering device rapidly decreases.
[0018]
According to the fourth aspect of the present invention, the other electric device is a collision influence reducing device driven by a current supplied from a power source when the vehicle collides or when there is a possibility of the collision. Or, when there is a risk of this, it is possible to operate the collision impact reduction device reliably without excessively reducing the steering assist torque generated by the electric power steering device, and to effectively reduce the impact of the vehicle collision. it can.
[0019]
According to the fifth aspect of the present invention, when there is a possibility of a vehicle collision, it is determined that the shorter the time until the vehicle collision is, the higher the possibility of the voltage drop of the power supply is. Therefore, in a situation where there is a possibility of a vehicle collision but there is a certain amount of time until the vehicle collision, the steering feeling is prevented from deteriorating and the time until the vehicle collision occurs. Therefore, it is possible to effectively suppress a decrease in the power supply voltage in a situation where there is no longer enough margin and to reliably operate the collision effect reducing device.
[0020]
Further, according to the configuration of the above-mentioned claim 6, since the collision influence reducing device is a device that increases the tension of the seat belt, the tension of the seat belt is surely increased at the time of the vehicle collision or when there is a fear thereof, As a result, the occupant can be reliably and effectively protected during a vehicle collision.
[0021]
According to the seventh aspect of the present invention, the auxiliary control amount includes a control amount that reduces the influence of the inertia of the steering or a control amount that reduces the influence of the frictional force during the steering, and therefore corresponds to the basic assist control amount. The power consumption corresponding to the control amount for reducing the influence of the inertia of the steering or the control amount for reducing the influence of the friction force during the steering can be surely reduced while effectively suppressing the decrease in the steering assist torque. .
[0022]
Further, according to the configuration of the above-described eighth aspect, when there is a voltage drop or a risk of the power supply, the steering amount is more than the control amount that reduces the influence of the steering inertia according to the voltage drop amount or the degree of the voltage drop. The amount of control that reduces the influence of the frictional force is reduced with priority. In general, since the control amount that reduces the influence of the frictional force during steering is higher than the control amount that reduces the influence of the inertia of steering, the amount of steering is less than the control amount that reduces the influence of the frictional force during steering. Compared with the case where the control amount that reduces the influence of inertia is prioritized and reduced, it is possible to effectively suppress a decrease in the power supply voltage, and the control amount that reduces the influence of steering inertia and Compared with the case where both of the control amounts that reduce the influence of the frictional force are simultaneously reduced, it is possible to reduce the deterioration of the steering feeling due to the reduction of the auxiliary control amount.
[0023]
In general, the amount of control that improves the damping performance during steering is reduced in terms of the amount of basic assist control, the amount of control that reduces the influence of steering inertia, and the influence of frictional force during steering when viewed in the direction of steering assist torque. Since the direction of the control amount is opposite, the power consumption by the electric power steering device increases on the contrary if the control amount for improving the damping performance during steering is reduced.
[0024]
According to the configuration of claim 9, the auxiliary control amount is a control amount that reduces the influence of the inertia of the steering, or a control amount that reduces the influence of the frictional force during the steering, and a control amount that improves the attenuation during the steering. The amount of control that improves the attenuation during steering is not reduced even when there is a risk of power supply voltage drop or there is a risk, so the power supply voltage can be reduced by reducing the amount of control that improves the attenuation during steering. It is possible to reliably prevent the reduction.
[0025]
[Preferred embodiment of the problem solving means]
According to one preferred aspect of the present invention, in the configuration of claim 1, the control means is configured to reduce the auxiliary control amount in preference to the basic assist control amount by reducing only the auxiliary control amount. (Preferred embodiment 1).
[0026]
According to another preferred aspect of the present invention, in the configuration of claim 1, the control means makes the basic assist control amount larger by making the reduction amount of the auxiliary control amount larger than the reduction amount of the basic assist control amount. It is configured to reduce the auxiliary control amount with priority over (preferred aspect 2).
[0027]
According to another preferred aspect of the present invention, in the configuration of claim 1, when the control means determines that there is a possibility that the power supply voltage is lowered or there is a risk even if the auxiliary control amount is reduced to zero. The basic assist control amount is reduced (preferred aspect 3).
[0028]
According to another preferred embodiment of the present invention, in the configuration of claim 2, the auxiliary control amount includes a plurality of compensation amounts for improving the steering feeling for different purposes, and the control means is a power source. A plurality of compensation amounts are configured to be sequentially reduced according to their reduction priority as the voltage drop amount or the degree of fear thereof increases (Preferred aspect 4).
[0029]
According to another preferred embodiment of the present invention, in the configuration of claim 2, the auxiliary control amount includes a plurality of compensation amounts for improving the steering feeling for different purposes, and the control means is a power source. The amount of reduction of each compensation amount is increased as the voltage drop amount or the degree of fear thereof increases (preferred aspect 5).
[0030]
According to another preferred aspect of the present invention, in the configuration of claim 3, the control means determines that the possibility of the voltage drop of the power supply is higher as the possibility of operation of the other electric device is higher. (Preferred embodiment 6).
[0031]
According to another preferred aspect of the present invention, in the configuration of claim 8, the control means reduces the voltage of the power source even if the control amount for reducing the influence of the frictional force during steering is reduced to zero. Alternatively, by reducing the control amount that reduces the influence of the inertia of the steering when it is determined that there is a risk, the influence of the frictional force during the steering is reduced more than the control amount that reduces the influence of the inertia of the steering. The control amount is preferentially reduced (preferred aspect 7).
[0032]
According to another preferred aspect of the present invention, in the configuration of claim 8, the control means reduces the influence of the frictional force at the time of steering rather than the reduction amount of the control amount that reduces the influence of the steering inertia. By increasing the reduction amount of the control amount to be reduced, the control amount that reduces the influence of the frictional force during steering is prioritized and reduced over the control amount that reduces the influence of the steering inertia (preferably Aspect 8).
[0033]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in detail with reference to the accompanying drawings with respect to several preferred embodiments (hereinafter simply referred to as embodiments).
[0034]
First embodiment
FIG. 1 is a schematic configuration diagram showing a first embodiment of an electric power steering device according to the present invention applied to a vehicle equipped with a behavior control device of a braking force control type.
[0035]
In FIG. 1, 10 FL and 10 FR respectively indicate left and right front wheels that are driven wheels of the vehicle 12, and 10 RL and 10 RR respectively indicate left and right rear wheels that are drive wheels of the vehicle 12. The left and right front wheels 10FL and 10FR, which are also steered wheels, are steered via tie rods 18L and 18R by a rack and pinion type electric power steering unit 16 driven in response to the steering wheel 14 being steered by the driver. The
[0036]
In the illustrated embodiment, the electric power steering unit 16 is a rack coaxial type electric power steering device and is controlled by the electronic control unit 20. The electric power steering unit 16 includes an electric motor 22 and, for example, a ball screw type conversion mechanism 26 that converts the rotational torque of the electric motor 22 into a force in the reciprocating direction of the rack bar 24, and is supplied from the battery 28 to the electric motor 22. By generating an auxiliary turning force that drives the rack bar 24 relative to the housing 30 in accordance with the control current Ia, a steering assist torque that reduces the driver's steering burden is generated.
[0037]
The braking force of each wheel is controlled by controlling the braking pressure of the wheel cylinders 36FR, 36FL, 36RR, 36RL by the hydraulic circuit 34 of the braking device 32. Although not shown in the drawing, the hydraulic circuit 34 includes a reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in response to the depression operation of the brake pedal 38 by the driver. It is controlled by the master cylinder 40 and is controlled by the electronic control unit 42 as necessary. The oil pump of the hydraulic circuit 34 is driven by supplying a drive current from the battery 28 to an electric motor (not shown).
[0038]
The steering shaft 44 is provided with a steering angle sensor 46 for detecting the steering angle θ and a torque sensor 48 for detecting the steering torque Ts. The vehicle 12 has a vehicle speed sensor 50 for detecting the vehicle speed V, and a longitudinal acceleration for detecting the longitudinal acceleration Gx. A sensor 52, a lateral acceleration sensor 54 for detecting the lateral acceleration Gy, a yaw rate sensor 56 for detecting the yaw rate γ, and an SOC meter 58 for detecting the voltage Vp of the battery 28 are provided. The steering angle sensor 46, the torque sensor 48, the lateral acceleration sensor 54, and the yaw rate sensor 56 detect the steering angle θ, the steering torque Ts, the lateral acceleration Gy, and the yaw rate γ, respectively, with the vehicle's right turn direction being positive.
[0039]
As shown in the figure, a signal indicating the steering angle θ detected by the steering angle sensor 46, a signal indicating the steering torque Ts detected by the torque sensor 48, a signal indicating the vehicle speed V detected by the vehicle speed sensor 50, and an SOC meter 58 A signal indicating the detected voltage Vp of the battery 28 is input to the electronic control unit 20, and a signal indicating the longitudinal acceleration Gx and the lateral acceleration Gy respectively detected by the longitudinal acceleration sensor 52, the lateral acceleration sensor 54, and the yaw rate sensor 50 are obtained. And a signal indicating the yaw rate γ are input to the electronic control unit 42. Although not shown in detail in the figure, the electronic control devices 20 and 42 have, for example, a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. Includes component microcomputer.
[0040]
The electronic control unit 20 calculates the basic assist current Ib for reducing the driver's steering burden based on the steering torque Ts and the vehicle speed V according to the flowchart shown in FIG. 2, and calculates the differential value Tsd of the steering torque Ts, etc. Compensation current for improving steering feeling based on parameters (compensation current Ii for reducing the influence of steering inertia, compensation current If for reducing the influence of frictional force during steering, attenuation during steering Compensation current Id) for improving performance is calculated, and the sum (Ib + Ii + If + Id) of these currents is calculated as a target control current Ia in normal times, and the electric power steering unit 16 is controlled based on the target control current Ia.
[0041]
Further, according to the flowchart shown in FIG. 2, when the voltage Vp of the battery 28 detected by the SOC meter 58 becomes lower than the first reference value Vp1, the electronic control unit 20 performs the basic assist current Ib and the compensation currents Ii and Id. When the voltage Vp of the battery 28 becomes lower than the second reference value Vp2, the sum (Ib + Id) of the basic assist current Ib and the compensation current Id is calculated as the target control current Ia (Ib + Ii + Id). When it is calculated as Ia and the voltage Vp of the battery 28 becomes lower than the third reference value Vp3, the target control current Ia is the sum (Ibl + Id) of the basic assist current Ibl and the compensation current Id whose basic assist current Ib is reduced and corrected. As a result, it is possible to suppress the shortage of the steering assist torque that reduces the driver's steering burden, and to control the electric performance of the hydraulic circuit 34 such as an oil pump. Over reliable operation of the steering unit 16 other than the electric component is secured.
[0042]
On the other hand, the electronic control unit 42, based on the vehicle state quantity such as the lateral acceleration Gy that changes as the vehicle travels, spin state quantity SS indicating the degree of vehicle spin and drift out state quantity DS indicating the degree of vehicle drift out. When the vehicle behavior is determined to be deteriorated based on the spin state quantity SS and the drift-out state quantity DS, the behavior control for stabilizing the vehicle behavior based on the spin state quantity SS or the drift-out state quantity DS is performed. The target slip rate Rsti (i = fr, fl, rr, rl) of each wheel is calculated, and the braking force of each wheel is controlled so that the slip rate of each wheel becomes the target slip rate Rsti. Stabilize. Thus, the braking device 32 and the electronic control device 42 constitute a braking force control type behavior control device that works together to stabilize the behavior of the vehicle.
[0043]
In this case, when it is determined that the vehicle behavior is not deteriorated but may be deteriorated based on the spin state amount SS and the drift-out state amount DS, the electronic control unit 42 prior to executing the behavior control. However, when the hydraulic circuit 34 is provided with an accumulator for storing high-pressure oil, the oil pump has a predetermined lower limit for the pressure in the accumulator. It may be driven until the pressure becomes equal to or higher than a predetermined upper limit value when the pressure drops below the value.
[0044]
Next, the steering assist torque control in the illustrated first embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals. This also applies to other embodiments described later.
[0045]
First, at step 10, a signal indicating the steering torque Ts is read, and at step 20, the magnitude increases as the steering torque Ts increases, and the magnitude decreases as the vehicle speed V increases. Thus, based on the steering torque Ts and the vehicle speed V, a basic assist current Ia as a basic assist control amount for reducing the steering torque is calculated from a map corresponding to the graph shown in FIG.
[0046]
In step 30, various compensation currents are calculated as auxiliary control amounts for improving the steering feeling. Specifically, an inertia compensation current Ii for reducing the influence of the steering inertia is calculated from a map corresponding to the graph shown in FIG. 8 based on the differential value Tsd of the steering torque, and the time differential value of the steering angle θ is calculated. Based on a certain steering speed θd, a friction compensation current If for reducing the influence of the frictional force at the time of steering is calculated from a map corresponding to the graph shown in FIG. 9, and based on the steering speed θd, shown in FIG. From the map corresponding to the graph, a damping compensation current Id for improving the attenuation during steering is calculated.
[0047]
In step 50, it is determined whether or not the power supply voltage Vp of the battery 28 is less than a first reference value Vp1 (a positive constant). The target current Ia for the electric motor 22 of the power steering unit 16 is calculated as the sum of the basic assist current Ib, the inertia compensation current Ii, the friction compensation current If, and the damping compensation current Id.
[0048]
In step 70, it is determined whether or not the power supply voltage Vp is less than a second reference value Vp2 (a positive constant smaller than the first reference value Vp1). If a negative determination is made, step 70 is performed. At 80, the target current Ia is calculated as the sum of the basic assist current Ib, the inertia compensation current Ii, and the damping compensation current Id (the friction compensation current If is reduced to 0). move on.
[0049]
In step 90, it is determined whether or not the power supply voltage Vp is less than a third reference value Vp3 (a positive constant smaller than the second reference value Vp2). If a negative determination is made, step 90 is performed. At 100, the target current Ia is calculated as the sum of the basic assist current Ib and the damping compensation current Id (the inertia compensation current Ii and the friction compensation current If are reduced to 0). In this case, a value obtained by multiplying the basic assist current Ib by a reduction correction coefficient larger than 0 and smaller than 1 is used as the basic assist current Ibr after the reduction correction, and the target current Ia is the basic assist current Ibr and the compensation current Id after the reduction correction. (Inertia compensation current Ii and friction compensation current If are reduced to 0 and basic assist current Ib is also reduced).
[0050]
In step 150, the steering assist torque is controlled by supplying a control current to the electric motor 22 of the electric power steering unit 16 based on the target current Ia.
[0051]
Thus, according to the illustrated embodiment, the basic assist current Ia is calculated based on the steering torque Ts and the vehicle speed V so that the magnitude increases as the steering torque Ts increases and the magnitude decreases as the vehicle speed V increases. Then, various compensation currents as auxiliary control amounts for improving the steering feeling are calculated.
[0052]
When the power supply voltage Vp is determined to be equal to or higher than the first reference value Vp1, the target current Ia is calculated as the sum of the basic assist current Ib, the inertia compensation current Ii, the friction compensation current If, and the damping compensation current Id. However, if it is determined that the power supply voltage Vp is less than the first reference value Vp1 and greater than or equal to the second reference value Vp2, the friction compensation current If is reduced to 0, and the target current Ia becomes the basic assist current Ib. The sum of the inertia compensation current Ii and the damping compensation current Id is calculated.
[0053]
If it is determined that the power supply voltage Vp is less than the second reference value Vp2 and greater than or equal to the third reference value Vp3, the inertia compensation current Ii and the friction compensation current If are reduced to 0, and the target current Ia is basically set. When it is calculated as the sum of the assist current Ib and the damping compensation current Id and the power supply voltage Vp is determined to be less than the third reference value Vp3, the inertia compensation current Ii and the friction compensation current If are reduced to 0, The target current Ia is calculated as the sum of the basic assist current Ibr and the compensation current Id after the reduction correction.
[0054]
Therefore, according to the first embodiment shown in the drawing, when the power supply voltage Vp decreases, when the power supply voltage Vp is equal to or higher than the third reference value Vp3, the steering feeling is improved without reducing the basic assist current Ib. As a result, the power consumption due to the compensation current is reduced in a situation where the power supply voltage Vp is lowered, thereby effectively suppressing further reduction of the power supply voltage and steering. It is possible to reliably generate the steering assist torque necessary for reducing the torque and to reliably suppress the increase in the driver's steering burden due to the increase in the steering reaction force.
[0055]
Further, according to the first embodiment shown in the figure, since the types of compensation currents that are reduced as the power supply voltage Vp decreases are increased, the power consumption due to the compensation current increases as the power supply voltage Vp decreases. The reduction effect can be sequentially increased, and the sudden deterioration of the steering feeling due to the reduction of the compensation current can be suppressed.
[0056]
For example, the solid line in FIG. 15 shows an example of the relationship between the power supply voltage Vp and the control current I supplied to the electric motor 22 of the electric power steering unit 16 in the illustrated first embodiment. As can be seen from the solid line in FIG. 15, according to the first embodiment shown in the figure, the control current I is gradually increased as the power supply voltage Vp decreases while the basic assist current Ib is reliably secured even when the power supply voltage Vp decreases. It can be surely reduced.
[0057]
In particular, according to the first embodiment shown in the drawing, the reduction priority is set in descending order of the current values of the inertia compensation current Ii and the friction compensation current If among the compensation currents for improving the steering feeling, and the power supply voltage Vp As the degree of decrease is increased, the friction compensation current If is first reduced to 0, and then the inertia compensation current Ii is reduced to 0, so that the inertia compensation current Ii and the friction compensation current If are reduced in the reverse order. As a result, it is possible to effectively suppress a decrease in the power supply voltage and to reduce the compensation current as compared with the case where both the inertia compensation current Ii and the friction compensation current If are simultaneously reduced. Can be reduced.
[0058]
Second embodiment
FIG. 3 is a flowchart showing a steering assist torque control routine according to the second embodiment of the present invention, which is configured as a modification of the first embodiment described above. In FIG. 3, the same step number as that shown in FIG. 2 is assigned to the same step as that shown in FIG.
[0059]
As shown in FIG. 3, steps 10 to 30 and 150 are executed in the same manner as in the first embodiment described above. In step 120 executed after step 30, the power supply voltage Vp is set. Based on the map corresponding to the graph shown in FIG. 11, the basic assist current Ib and the correction coefficients Kb, Ki and Kf for the compensation currents Ii and If are calculated. In step 140, the target current Ia is calculated according to the following equation (1). Calculated.
Ia = Kb.Ib + Ki.Ii + Kf.If + Id (1)
[0060]
Thus, according to the second embodiment shown in the figure, the basic assist current Ib and the correction coefficients Kb, Ki, and Kf for the compensation currents Ii and If are calculated based on the power supply voltage Vp so as to decrease as the power supply voltage Vp decreases. Ia is calculated as the product of the basic assist current Ib, the compensation currents Ii and If and the correction coefficients Kb, Ki and Kf and the sum of the damping compensation currents Id, respectively, according to the above equation 1.
[0061]
Therefore, according to the second embodiment shown in the figure, as in the case of the first embodiment described above, when the power supply voltage Vp decreases, the basic assist current Ib is reduced when the power supply voltage Vp is equal to or higher than the third reference value Vp3. The compensation current If for improving the steering feeling without being reduced is reduced, so that the power consumption due to the compensation current is reduced in the situation where the power supply voltage Vp is lowered, thereby further reducing the power supply voltage. The steering assist torque necessary for reducing the steering torque can be reliably generated and the increase in the driver's steering burden due to the increase in the steering reaction force can be reliably suppressed while effectively suppressing the occurrence of the steering torque.
[0062]
In particular, according to the second embodiment shown in the drawing, not only the types of compensation currents that are reduced as the degree of decrease in the power supply voltage Vp increases, but also each compensation current decreases as the degree of decrease in the power supply voltage Vp increases. Since the amount is gradually increased, the power consumption reduction effect by the compensation current is gradually and smoothly increased as the degree of decrease of the power supply voltage Vp is increased, thereby more effectively compensating current than the case of the first embodiment described above. It is possible to suppress the sudden deterioration of the steering feeling due to the reduction of the above.
[0063]
For example, the broken line in FIG. 15 shows an example of the relationship between the power supply voltage Vp and the control current I supplied to the electric motor 22 of the electric power steering unit 16 in the illustrated second embodiment. As can be seen from the broken line in FIG. 15, according to the second embodiment shown in the figure, the control current I is gradually increased as the power supply voltage Vp decreases while the basic assist current Ib is reliably secured even when the power supply voltage Vp decreases. However, it can be reduced smoothly and surely.
[0064]
Third embodiment
FIG. 4 is a schematic configuration diagram showing a third embodiment of an electric power steering apparatus according to the present invention applied to a vehicle equipped with an electric seat belt apparatus. In FIG. 4, the same members as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.
[0065]
In the third embodiment, the vehicle 12 detects a front obstacle such as a preceding vehicle in front of the host vehicle using radio waves such as millimeter waves and laser light, and the relative distance Lre to the preceding vehicle. A radar sensor 60 for detecting the relative speed Vre is provided. Signals indicating the relative distance Lre and the relative speed Vre detected by the radar sensor 60 are input to the electronic control unit 42.
[0066]
Further, the vehicle 12 is provided with a motor type seat belt device 62 abbreviated as MSB (Motorized Seat Belt), and the seat belt device 62 is not shown in the figure by the battery 28 when a predetermined condition is satisfied. Is driven by supplying a drive current to the seat belt, and a seat belt (not shown) is wound to give a required tension thereto.
[0067]
The electronic control unit 42 determines whether or not there is a possibility that a front obstacle exists in front of the host vehicle and collides with the front obstacle based on a signal from the radar sensor 34 according to the flowchart shown in FIG. When there is a possibility of colliding with a front obstacle, a time Tc (= Lre / Vre) until the collision with the front obstacle is calculated based on the relative distance Lre to the front obstacle and the relative speed Vre of the vehicle with respect to the front obstacle. When the time Tc becomes equal to or less than a predetermined value, the seat belt device 62 is operated by supplying a driving current to the electric motor of the seat belt device 62, and whether or not there is a possibility of collision with a front obstacle is determined. And a signal indicating the time Tc until the collision with the front obstacle are output to the electronic control unit 20.
[0068]
In the third embodiment, as in the case of the first embodiment described above, the electronic control unit 20 is based on the steering torque Ts and the vehicle speed V according to the flowchart shown in FIG. Compensation current (inertia compensation current Ii, friction compensation current If, damping compensation) for calculating the basic assist current Ib for reducing the steering burden and improving the steering feeling based on parameters such as the differential value Tsd of the steering torque Ts The current Id) is calculated, and the sum (Ib + Ii + If + Id) of these currents is calculated as the target control current Ia in normal times, and the electric power steering unit 16 is controlled based on the target control current Ia.
[0069]
Further, when it is determined that the electronic control device 20 may collide with the front obstacle based on the signal input from the electronic control device 42 according to the flowchart shown in FIG. When the time Tc becomes smaller than the first reference value Tc1, the sum (Ib + Ii + Id) of the basic assist current Ib and the compensation currents Ii and Id is calculated as the target control current Ia, and the time Tc until the collision is the second reference value When it becomes smaller than Tc2, the sum (Ib + Id) of the basic assist current Ib and the compensation current Id is calculated as the target control current Ia. When the time Tc until the collision becomes smaller than the third reference value Tc3, the basic assist current Ib Is calculated as a target control current Ia by reducing the sum of the basic assist current Ibl and the compensation current Id (Ibl + Id), thereby reducing the steering burden on the driver. Reliable operation of the seat belt device 62 is ensured while suppressing the torque is insufficient.
[0070]
Next, a steering assist torque control routine in the third embodiment will be described with reference to the flowchart shown in FIG. In FIG. 5, the same steps as those shown in FIG. 2 are given step numbers obtained by adding 200 to the step numbers given in FIG.
[0071]
As shown in FIG. 5, steps 210 to 230, 260, 280, 300, 310, and 350 are steps 10 to 30, 60, 80, 100, 110, and 150 in the first embodiment described above, respectively. In step 240, which is executed in the same manner as in the case, and after step 230, it is determined whether or not there is a possibility of colliding with a front obstacle based on a signal input from the electronic control unit 42. If a negative determination is made, the process proceeds to step 260. If an affirmative determination is made, the process proceeds to step 250.
[0072]
In step 250, it is determined whether or not the time Tc until the collision with the forward obstacle is smaller than the first reference value Tc1 (positive constant). If negative determination is made, step 260 is executed. If an affirmative determination is made, the process proceeds to step 270.
[0073]
In step 270, it is determined whether or not the time Tc until the collision is less than the second reference value Tc2 (a positive constant smaller than the first reference value Tc1), and a negative determination is made. Sometimes step 280 is executed, and when an affirmative determination is made, the routine proceeds to step 290.
[0074]
In step 290, it is determined whether or not the time Tc until the collision is less than the third reference value Tc3 (a positive constant smaller than the second reference value Tc2), and a negative determination is made. Sometimes step 300 is executed, and when an affirmative determination is made, step 310 is executed.
[0075]
Thus, according to the illustrated third embodiment, whether or not there is a possibility of colliding with a front obstacle, that is, there is a possibility that the power supply voltage Vp is at least temporarily lowered by operating the seat belt device 62. When it is determined whether or not there is a possibility of collision with a forward obstacle, and it is determined that the time Tc until the collision is equal to or greater than the first reference value Tc1, the target current Ia is the basic assist current. Although calculated as the sum of Ib, inertia compensation current Ii, friction compensation current If, and damping compensation current Id, the time Tc until the collision is less than the first reference value Tc1 and greater than or equal to the second reference value Tc2. Is determined, the friction compensation current If is reduced to 0, and the target current Ia is calculated as the sum of the basic assist current Ib, the inertia compensation current Ii, and the damping compensation current Id.
[0076]
If it is determined that the time Tc until the collision is less than the second reference value Tc2 and greater than or equal to the third reference value Tc3, the inertia compensation current Ii and the friction compensation current If are reduced to 0, and the target current Ia Is calculated as the sum of the basic assist current Ib and the damping compensation current Id, and when it is determined that the time Tc until the collision is less than the third reference value Tc3, the inertia compensation current Ii and the friction compensation current If are 0. The target current Ia is calculated as the sum of the basic assist current Ibr and the compensation current Id after the reduction correction.
[0077]
Therefore, according to the third embodiment shown in the figure, when the risk of collision with a forward obstacle increases, the basic assist current Ib is reduced when the time Tc until the collision is equal to or greater than the third reference value Tc3. Since the compensation current If for improving the steering feeling is reduced, the power consumption due to the compensation current is reduced in a situation where there is a high possibility of colliding with a front obstacle. It is possible to reliably suppress the increase in the steering burden caused by the increase in the steering reaction force by securely generating the steering assist torque necessary for reducing the steering torque while effectively suppressing the decrease. it can.
[0078]
Further, according to the third embodiment shown in the figure, since the types of compensation currents that are reduced as the possibility of colliding with a front obstacle increases, the compensation currents increase as the degree of decrease in the power supply voltage Vp increases. The effect of reducing the power consumption can be increased sequentially, and the sudden deterioration of the steering feeling due to the reduction of the compensation current can be suppressed.
[0079]
For example, the solid line in FIG. 16 shows an example of the relationship between the time Tc until the collision and the control current I supplied to the electric motor 22 of the electric power steering unit 16 in the illustrated third embodiment. In FIG. 16, time points t1 to t3 indicate the time points at which the predicted time Tc until the vehicle collision is Tc1 to Tc3, respectively. As can be seen from the solid line in FIG. 16, according to the third embodiment shown in the figure, even if the possibility of colliding with the front obstacle increases, the basic assist current Ib can be ensured and the collision with the front obstacle can be ensured. As this increases, the control current I can be reliably reduced stepwise.
[0080]
In particular, according to the third embodiment shown in the drawing, as in the case of the first and second embodiments described above, among the compensation currents for improving the steering feeling, the inertia compensation current Ii and the friction compensation current If are currents. The order of reduction is set in descending order, and the friction compensation current If is first reduced to 0 and then the inertia compensation current Ii is reduced to 0 as the risk of collision with a front obstacle increases. Compared with the case where Ii and friction compensation current If are reduced in the reverse order, it is possible to effectively suppress a decrease in power supply voltage, and both inertia compensation current Ii and friction compensation current If are simultaneously reduced. Compared with the case where it does, the deterioration of the steering feeling resulting from the reduction of compensation current can be reduced.
[0081]
Fourth embodiment
FIG. 6 is a flowchart showing a steering assist torque control routine according to the fourth embodiment of the present invention, which is configured as a modification of the above-described third embodiment. In FIG. 6, the same steps as those shown in FIG. 3 are given step numbers obtained by adding 200 to the step numbers given in FIG. 3, and the steps shown in FIG. The same step number is assigned to the same step as the step number assigned in FIG.
[0082]
As shown in FIG. 6, steps 210 to 240, 260, and 340 are executed in the same manner as in the third embodiment described above, and when an affirmative determination is made in step 240, step 320 is executed. Based on the time Tc until the collision, correction coefficients Kb, Ki, and Kf for the basic assist current Ib and the compensation currents Ii and If are calculated from a map corresponding to the graph shown in FIG.
[0083]
Thus, according to the fourth embodiment shown in the figure, the correction coefficients Kb, Ki, and Kf for the basic assist current Ib and the compensation currents Ii and If are calculated based on the time Tc until the collision so that the time Tc until the collision becomes shorter. Then, the target current Ia is calculated as the product of the basic assist current Ib, the compensation currents Ii and If and the correction coefficients Kb, Ki and Kf and the sum of the damping compensation currents Id according to the above equation 1, respectively.
[0084]
Therefore, according to the fourth embodiment shown in the figure, as in the case of the third embodiment described above, when the risk of collision with a front obstacle increases, the time Tc until the collision is equal to or greater than the third reference value Tc3. In some cases, the compensation current If for improving the steering feeling is reduced without reducing the basic assist current Ib, and so on. A driver who is caused by an increase in the steering reaction force by reliably generating the steering assist torque necessary for reducing the steering torque while effectively reducing the power consumption and thereby further reducing the power supply voltage. The increase in steering burden can be reliably suppressed.
[0085]
In particular, according to the fourth embodiment shown in the drawing, not only the types of compensation currents that are reduced gradually increase as the possibility of colliding with a front obstacle increases, but also the possibility of collision with a front obstacle increases. As the amount of reduction of each compensation current is gradually increased, the power consumption reduction effect due to the compensation current is gradually and smoothly increased as the degree of decrease in the power supply voltage Vp is increased. It is possible to suppress the sudden deterioration of the steering feeling due to the reduction of the compensation current more effectively.
[0086]
For example, the broken line in FIG. 16 shows an example of the relationship between the power supply voltage Vp and the control current I supplied to the electric motor 22 of the electric power steering unit 16 in the illustrated fourth embodiment. As can be seen from the broken line in FIG. 16, according to the fourth embodiment shown in the figure, the power supply voltage Vp is lowered while the basic assist current Ib is reliably ensured even when the possibility of colliding with a front obstacle increases. As a result, the control current I can be reduced smoothly and reliably, not in steps.
[0087]
As can be seen from a comparison between FIG. 10 and FIGS. 7 to 9, in general, the damping compensation current Id, which is a control amount that improves the attenuation during steering, is determined by looking at the direction of the steering assist torque and the basic assist current Ib and the steering. Since the direction of the inertia compensation current Ii as the control amount for reducing the influence of the inertia and the direction of the friction compensation current If as the control amount for reducing the influence of the friction force during steering is opposite, the damping compensation current Id is reduced. Then, the power consumption by the electric power steering device increases.
[0088]
According to each of the illustrated embodiments, the damping compensation current Id is not reduced even when the power supply voltage Vp is lowered. For example, when the power supply voltage Vp is lowered, the damping current including the damping compensation current Id is reduced. It is possible to reliably prevent the power supply voltage from being lowered by reducing the compensation current Id.
[0089]
Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.
[0090]
For example, in each of the above-described embodiments, the inertia compensation current Ii, the friction compensation current If, and the damping compensation current Id are calculated as auxiliary control amounts for improving the steering feeling, and the friction compensation current If and the inertia compensation current Ii are calculated. However, the order of reduction may be reversed, and any one of these compensation currents Ii, If, and Id may be omitted.
[0091]
The first and second embodiments described above are embodiments when the power supply voltage Vp is lowered, and the third and fourth embodiments described above are embodiments when the power supply voltage Vp may be lowered. However, for example, the first embodiment may be combined with the third embodiment, and the second embodiment and the fourth embodiment may be combined. In the former case, step 240 in FIG. 2 is executed when the negative determination is made, and in the latter case, when the negative determination is made at step 240 of FIG. 6, the steps 120 and after of FIG. 3 are executed. Configured to be.
[0092]
In the second and fourth embodiments described above, the correction coefficients Kb, Ki, and Kf for the basic assist current Ib and the compensation currents Ii and If are maps corresponding to the graphs shown in FIGS. However, the maps for calculating the correction coefficients Kb, Ki, and Kf are not limited to these. For example, the maps corresponding to the graphs shown in FIGS. The compensation currents Ii and If may be simultaneously reduced by modification as shown in FIGS. 13 and 14, respectively, in which case the degree of reduction of the compensation current If is higher than the compensation current Ii. It is preferably set.
[0093]
In the third and fourth embodiments described above, whether or not there is a possibility that the power supply voltage Vp is at least temporarily lowered is determined whether or not there is a possibility of colliding with a front obstacle. However, the electric device that may at least temporarily reduce the power supply voltage Vp is not limited to the seat belt device 62. It may be a reduction device, or may be a device other than the collision influence reduction device such as the oil pump in the first and third embodiments described above.
[0094]
Further, in each of the above-described embodiments, the vehicle is a rear wheel drive vehicle, but the vehicle to which the present invention is applied may be a front wheel drive vehicle or a four wheel drive vehicle, and the steering assist torque is arbitrarily set. As long as it can be controlled, the power steering device may be of any construction known in the art.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first embodiment of an electric power steering device according to the present invention applied to a vehicle provided with a behavior control device of a braking force control type.
FIG. 2 is a flowchart showing a steering assist torque control routine in the first embodiment.
FIG. 3 is a flowchart showing a steering assist torque control routine according to a second embodiment of the present invention configured as a modification of the first embodiment.
FIG. 4 is a schematic configuration diagram showing a third embodiment of an electric power steering apparatus according to the present invention applied to a vehicle equipped with an electric seat belt device.
FIG. 5 is a flowchart showing a steering assist torque control routine in a third embodiment.
FIG. 6 is a flowchart showing a steering assist torque control routine according to a fourth embodiment of the present invention configured as a modification of the third embodiment.
FIG. 7 is a graph showing a relationship among steering torque Ts, vehicle speed V, and basic assist current Ia.
FIG. 8 is a graph showing a relationship between a differential value Tsd of steering torque and a compensation current Ii for reducing the influence of steering inertia.
FIG. 9 is a graph showing a relationship between a steering speed θd and a compensation current If for reducing the influence of frictional force during steering.
FIG. 10 is a graph showing a relationship between a steering speed θd and a compensation current Id for improving attenuation during steering.
FIG. 11 is a graph showing the relationship between the power supply voltage Vp and the basic assist current Ia and the correction coefficients Ka, Ki, and Kf for the compensation currents Ii and If in the second embodiment.
FIG. 12 is a graph showing a relationship between a time Tc until a collision and correction coefficients Ka, Ki, and Kf with respect to a basic assist current Ia and compensation currents Ii and If in the fourth embodiment.
FIG. 13 is a graph showing the relationship between the power supply voltage Vp, the basic assist current Ia, and the correction coefficients Ka, Ki, and Kf for the compensation currents Ii and If in the modification of the second embodiment.
FIG. 14 is a graph showing a relationship between a time Tc until a collision and correction coefficients Ka, Ki and Kf with respect to a basic assist current Ia and compensation currents Ii and If in a modified example of the fourth embodiment.
FIG. 15 shows an example of the relationship between the voltage Vp of the power source and the control current I supplied to the electric motor of the electric power steering device in the first embodiment (solid line) and the second embodiment (broken line). It is a graph which shows.
FIG. 16 shows the relationship between the time Tc until the collision and the control current I supplied to the electric motor of the electric power steering device in the third embodiment (solid line) and the fourth embodiment (broken line). It is a graph which shows an example.
[Explanation of symbols]
14 ... Steering wheel
16 ... Electric power steering unit
20 ... Electronic control unit
28 ... Battery
32 ... Brake device
42. Electronic control unit
46: Steering angle sensor
48 ... Torque sensor
50 ... Vehicle speed sensor
56 ... Yaw rate sensor
58 ... SOC meter

Claims (9)

Calculating a target control current based on a sum of a steering assist torque generating means for generating a steering assist torque according to the control current, and a basic assist control amount based on the steering torque and an auxiliary control amount for improving steering feeling; And a control means for controlling a control current supplied from the power source to the steering assist torque generating means based on the target control current. An electric power steering apparatus for a vehicle characterized by determining a fear and reducing the auxiliary control amount in preference to the basic assist control amount when it is determined that there is a risk of a voltage drop or the power supply. . 2. The electric power steering apparatus for a vehicle according to claim 1, wherein the control means increases the reduction amount of the auxiliary control amount as the amount of voltage drop of the power supply or the degree of fear thereof increases. 2. The control unit according to claim 1, wherein the control unit determines that there is a possibility of a voltage drop of the power source when there is a high possibility of operation of another electric device driven by a current supplied from the power source. 2. An electric power steering device for a vehicle according to 2. 4. The vehicle electric type according to claim 3, wherein the other electric device is a collision influence reducing device driven by a current supplied from the power source when a vehicle collides or there is a risk of the collision. Power steering device. When there is a possibility of a vehicle collision, the control means determines that the shorter the time until the vehicle collision is, the higher the possibility of the voltage drop of the power supply is, and increases the reduction amount of the auxiliary control amount. The electric power steering device for a vehicle according to claim 4, wherein the vehicle is an electric power steering device. 6. The vehicular electric power steering apparatus according to claim 4, wherein the collision influence reducing apparatus is an apparatus for increasing a tension of a seat belt. 7. The electric power steering for a vehicle according to claim 1, wherein the auxiliary control amount includes a control amount that reduces an influence of inertia of steering or a control amount that reduces an influence of frictional force at the time of steering. apparatus. When the power supply voltage drops or is at risk, the control means causes the friction during the steering to be less than the control amount that reduces the influence of the inertia of the steering according to the voltage drop amount of the power supply or the degree of the risk. 8. The electric power steering apparatus for a vehicle according to claim 7, wherein a control amount for reducing the influence of force is preferentially reduced. The auxiliary control amount includes a control amount that reduces the influence of steering inertia or a control amount that reduces the influence of frictional force during steering and a control amount that improves damping during steering. 9. The electric power steering apparatus for a vehicle according to claim 7 or 8, wherein a control amount for improving the attenuation during the steering is not reduced even when a voltage drop of the power supply or there is a risk of the voltage drop.

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