JP3863438B2 - Electric power steering control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering control device used by being incorporated in a vehicle such as an automobile.
[0002]
[Prior art]
An example of a schematic structure of the electric power steering control device is shown in FIG. The illustrated electric power steering control device includes a main sensor 1 a, a sub sensor 1 b, a motor 2, and a control unit 3.
[0003]
The motor 2 is for applying a steering assist force to the steering mechanism. In the steering mechanism section, when the steering wheel 4 is operated by the driver, the steering shaft 5 rotates, and this rotation is converted into an operation in the vehicle width direction by the steering gear 6 so that the direction of the pair of wheels 7 changes. It is configured to be. The driving of the motor 2 assists the rotation of the steering shaft 5 to reduce the burden on the driver's steering operation.
[0004]
The main sensor 1a and the sub sensor 1b detect the steering torque of the steering mechanism and output torque signals T1 and T2. As will be described later, the torque signal T1 is used to determine the steering assist force in the control unit 3, whereas the torque signal T2 is used to determine whether or not the main sensor 1a is normal. Is done.
[0005]
Conventionally, as shown in FIG. 6, the control unit 3 stores control data d that defines the relationship between the steering torque and the current flowing through the motor 2 (hereinafter referred to as “motor current”). The motor current is determined based on the control data d and the torque signal T1. The control data d is basically specified so that the motor current increases as the steering torque increases, and thus the burden on the steering operation of the driver can be appropriately reduced. However, the motor current value has an upper limit value i. The reason is to prevent the motor 2 from overheating due to a large value of current flowing through the motor 2.
[0006]
The control unit 3 also obtains a difference between the torque signals T1 and T2, and based on this, determines whether or not the main sensor 1a is normal. The main sensor 1a and the sub sensor 1b have the same characteristics. When these are normal, the torque signals T1 and T2 have the same or substantially the same value, and the difference between them is small. In this case, the control unit 3 determines that both the main sensor 1a and the sub sensor 1b are normal. On the other hand, a failure may occur in either the main sensor 1a or the sub sensor 1b due to deterioration over time. In such a case, if the control unit 3 determines the motor current based on the torque signal T1 as usual, a steering assist force larger than necessary may be applied to the steering mechanism unit. Such a situation is not preferable in terms of operability of the vehicle. Therefore, when the difference between the torque signals T1 and T2 becomes larger than a certain value, the control unit 3 determines that an abnormality has occurred in the main sensor 1a or the sub sensor 1b, and thereafter, the steering assist to the steering mechanism unit is performed. The grant of power was stopped.
[0007]
[Problems to be solved by the invention]
In the electric power steering control device described above, if it is determined that there is an abnormality in the main sensor 1a or the sub sensor 1b, the steering assist force by the motor 2 cannot be obtained at all thereafter. Therefore, the burden on the driver's steering operation is not reduced, resulting in inconvenience.
[0008]
The present invention has been conceived under such circumstances, and even if a failure or the like occurs in either the main sensor or the sub sensor for detecting the steering torque, the driver's An object of the present invention is to provide an electric power steering control device capable of continuously reducing the burden of steering operation.
[0009]
DISCLOSURE OF THE INVENTION
In order to solve the above problems, the present invention takes the following technical means.
[0010]
The electric power steering control device provided by the present invention includes a main sensor and a sub sensor that detect steering torque and output a steering torque signal based on the detected data, and a steering assist force to the steering mechanism. a motor for imparting stores a first control data for determining the steering assist force of the motor corresponding to the steering torque, and the signal outputted from the main sensor and sub sensor Electric power steering control, comprising: a control means for determining a steering assist force of the motor based on a signal from the main sensor and the first control data when the difference is within a certain range; The control means reduces the steering assist force for the same steering torque as compared with the first control data. 2 is stored, and when the difference between the signals output from the main sensor and the sub sensor is out of the predetermined range, the second control is used instead of the first control data. Is configured to determine the steering assist force of the motor , and the second control data is determined according to a difference between signals output from the main sensor and the sub sensor. It is characterized in that the contents are different .
[0011]
According to such a configuration, when a failure occurs in either the main sensor or the sub sensor, the control means uses the second control data instead of the first control data. The steering assist force of the motor is determined. Accordingly, it is possible to continuously apply the steering assist force to the steering mechanism even after the sensor has failed, and the burden on the steering operation of the driver can be reduced. In addition, since the second control data makes the steering assist force of the motor smaller than the first control data, the second control data is used when a failure occurs. In addition, it is possible to prevent a steering assisting force from being applied to the steering mechanism part more than necessary. Furthermore, the steering assist force can be determined more finely than when the contents of the second control data are always the same, and the burden on the driver's steering operation can be reduced more appropriately. .
[0014]
Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the drawings.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be specifically described with reference to the drawings.
[0016]
FIG. 2 shows a first embodiment of the present invention. In the present embodiment, elements that are the same as or similar to those in the prior art are assigned the same reference numerals as in the prior art.
[0017]
The electric power steering control device of the present embodiment has a control unit 30 having a configuration different from that of the control unit 3 of the conventional technique, and other configurations are the same as those of the conventional technique. It is the same. Therefore, the electric power steering control device of the present embodiment is configured such that the main sensor 1a, the sub sensor 1b, and the motor 2 are assembled to the steering mechanism portion of the vehicle having the configuration shown in FIG.
[0018]
As clearly shown in FIG. 2, the control unit 30 includes a storage unit 31, a signal comparison unit 32, an abnormality determination unit 33, and a steering assist force determination unit 34. The storage unit 31 stores first control data D1 and second control data D2 shown in FIG. Both the first control data D1 and the second control data D2 are data defining the relationship between the steering torque and the motor current, like the control data d of the prior art, and the steering torque increases. As the motor current increases, the motor current is set so as not to exceed a predetermined upper limit value i. The first control data D1 is data that allows an appropriate steering assist force to be applied to the steering mechanism section in a normal state. The second control data D2 corresponds to the data obtained by translating the first control data D1 by a predetermined value L in the horizontal axis direction of FIG. 3, and is the same as compared with the first control data D1. The motor current value with respect to the steering torque is set to be small.
[0019]
The signal comparison means 32 calculates the absolute value T3 of the difference between the torque signals T1 and T2. The abnormality determination means 33 determines whether or not the main sensor 1a and the sub sensor 1b are normal depending on whether or not the absolute value T3 is within a certain range. When both the main sensor 1a and the sub sensor 1b are normal, the values of the torque signals T1 and T2 are the same or substantially the same, and the absolute value T3 is within the predetermined range. In this case, the abnormality determination unit 33 determines that both the main sensor 1a and the sub sensor 1b are normal.
[0020]
On the other hand, when a failure occurs in the main sensor 1a or the sub sensor 1b due to deterioration with time or the like, the difference between the values of the torque signals T1 and T2 increases, and the absolute value T3 exceeds the predetermined range. In this case, the abnormality determination unit 33 determines that the main sensor 1a or the sub sensor 1b is abnormal.
[0021]
When the abnormality determination unit 33 determines that the main sensor 1a and the sub sensor 1b are both normal, the steering assist force determination unit 34 calculates the motor current based on the torque signal T1 and the first control data D1. decide. On the other hand, when the abnormality determination unit 33 determines that the main sensor 1a or the sub sensor 1b is abnormal, the steering assist force determination unit 34 determines that the motor is based on the torque signal T1 and the second control data D2. It is configured to determine the current.
[0022]
As described above, according to the electric power steering control device of the present embodiment, when both the main sensor 1a and the sub sensor 1b are normal, the motor is based on the torque signal T1 and the first control data D1. The current is determined, and when a failure occurs in the main sensor 1a or the sub sensor 1b, the motor current is determined by using the second control data D2 instead of the first control data D1. Therefore, it is possible to continue to apply the steering assist force to the steering mechanism even after a failure occurs in either the main sensor 1a or the sub sensor 1b, thereby reducing the driver's steering operation burden. Can do. Since the second control data D2 is used to make the steering assist force of the motor 2 smaller than the first control data D1, even if the torque signal T1 is abnormal, the steering mechanism section is more than necessary. It is possible to prevent a large steering assist force from being applied.
[0023]
FIG. 4 shows a second embodiment of the present invention. In the figure, the same or similar elements as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment.
[0024]
The control unit 30a included in the electric power steering control device of the present embodiment includes data changing means 120 that can change the content of the second control data D2 stored in the storage unit 31.
[0025]
When the absolute value T3 obtained by the signal comparison unit 32 exceeds a certain range, the data changing unit 120 determines that the main sensor 1a or the sub sensor 1b is abnormal when the abnormality determination unit 33 determines that the second sensor 1b is abnormal. The content of the control data D2 is changed to the content corresponding to the translation of the first control data D1 by the absolute value T3 in the horizontal axis direction of FIG. However, the data changing means 120 changes the contents of the second control data D2 only when the absolute value T3 becomes larger than the absolute value calculated so far. If a failure occurs in the main sensor 1a or the sub sensor 1b, even if the absolute value T3 subsequently decreases, the reliability of the value is low. Therefore, the control unit 30a is set to perform the control as described above, instead of changing the content of the second control data D2 every time the absolute value T3 changes.
[0026]
Also in the electric power steering control device of the present embodiment, after the failure of the main sensor 1a or the sub sensor 1b, the second control data D1 is used instead of the first control data D1 as in the first embodiment. Since the steering assist force of the motor 2 is determined using the control data D2, it is possible to continuously apply the steering assist force to the steering mechanism, and to reduce the burden on the steering operation of the driver. be able to. Since the content of the second control data D2 is changed as the absolute value T3 increases, the steering assist force of the motor 2 can be determined finely. Further, as shown in FIG. 5, when the torque signal T1 is the torque Ta and the motor current is set to the current i1 by the first control data D1, a failure has occurred in the main sensor 1a or the sub sensor 1b. Sometimes, when the torque signal T1 increases to the torque Tb and the absolute value T3 also increases by the same amount, the motor current determined by the second control data D2 remains the current i1. Therefore, in this case, it is possible to prevent the driver from feeling uncomfortable with the steering operation. Of course, even if a failure occurs in the sensor in a manner other than this, the second control data D2 makes the steering assist force of the motor 2 smaller than the first control data D1. A steering assist force larger than necessary is not applied to the steering mechanism.
[0027]
The present invention is not limited to the contents of the above-described embodiment. For example, a plurality of second control data D2 may be stored in the control unit 30 and selectively used. As the number of second control data D2 increases, the steering assist force can be determined more finely. The second control data D2 has the same steering torque compared to the first control data D1 by reducing the slope of the curved portion of the first control data D1 shown in FIG. The value of the motor current with respect to the signal may be set to be small, or the upper limit value i of the motor current may be set to be smaller than that of the first control data D1. The first and second control data D1 and D2 are not limited to the relationship between the steering torque and the motor current, and may be the relationship between the steering torque and the motor voltage.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of a schematic structure of an electric power steering control device.
FIG. 2 is a block diagram showing a schematic structure of the electric power steering control device according to the first embodiment of the present invention.
FIG. 3 is a graph defining a relationship between steering torque and motor current according to the first embodiment of the present invention.
FIG. 4 is a block diagram showing a schematic structure of an electric power steering control device according to a second embodiment of the present invention.
FIG. 5 is a graph defining the relationship between steering torque and motor current according to a second embodiment of the present invention.
FIG. 6 is a graph defining the relationship between conventional steering torque and motor current.
[Explanation of symbols]
1a Main sensor 1b Sub sensor 2 Motors 3, 30, 30a Control unit D1 First control data D2 Second control data

Claims (1)

The steering torque detected, and a main sensor and the sub sensor and a signal of the steering torque and outputs on the basis of this detection data, a motor for imparting a steering assist force to a steering mechanism, corresponding to the steering torque Storing the first control data for determining the steering assist force of the motor, and when the difference between the signals output from the main sensor and the sub sensor is within a certain range, An electric power steering control device comprising: a control means for determining a steering assist force of the motor based on a signal and the first control data;
The control means stores second control data for reducing a steering assist force for the same steering torque as compared with the first control data, and a signal output from the main sensor and the sub sensor. When the difference between the two is outside the predetermined range, the steering assist force of the motor is determined by using the second control data instead of the first control data. And
The electric power steering control device according to claim 2, wherein the second control data is configured to have different contents according to a difference between signals output from the main sensor and the sub sensor .

Images