KR102159339B1 - Motor Driven Power Steering System and method thereof - Google Patents

Abstract

The MDPS (Motor Driving Power Steering) system according to an embodiment of the present invention includes an MDPS motor unit that generates a motor torque to assist when steering a steering wheel under control of a driver, a steering angle sensor that detects a steering angle of the steering wheel, A control unit that controls the motor torque output from the MDPS motor unit in response to a boost curve based on a parameter, and a vertical load estimated based on the motor torque and the steering angle are monitored in real time to determine the road surface condition, and the determination result Is transmitted to the control unit, and after it is determined as a rough road as the change amount of the vertical load appears for a change duration longer than a preset threshold time, if the change amount continuously increases according to the change trend of the vertical load, low output torque The parameter and the high output torque parameters include an MDPS driving inertia maintenance unit that increases the low output area parameter and decreases the high output area parameter in proportion to the increase in the amount of change in the vertical load, and the control unit can adjust the parameter according to the determination result. have.

Description

MDPS system and its operation method {Motor Driven Power Steering System and method thereof}

The present invention relates to an MDPS system, and more particularly, to an MDPS system for controlling motor torque output during rough road driving.

In recent years, the electronic control unit (ECU) drives the motor according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering torque sensor, providing a light and comfortable steering sensation when driving at low speeds, and good directional stability along with a heavy steering sensation when driving at high speeds. It is a trend to use an electric steering device that provides optimal steering conditions to the driver by allowing rapid steering in emergency situations.

Such an electric steering device is usually EHPS (Electro-hydraulic Power Steering) or MDPS (Motor Driven Power Steering), and the dual MDPS system forms hydraulic pressure from a pump to assist power, unlike a hydraulic system. As a structure that assists steering power with rotational force, the worm-shaft connected to the motor generating the power rotates the worm wheel connected to the steering-shaft to assist the steering power ( assist).

When the driver travels on rough roads where the road surface is uneven, it is difficult for the vehicle to secure straight forward driving ability regardless of the driver's will, as a momentary impact is applied to the steering wheel.

Republic of Korea Patent Application Publication No. 10-2013-0054859

The present invention provides an MDPS system and an operating method thereof with improved straightness driving performance by controlling a motor torque in consideration of not only the vehicle speed but also the variation of the vertical load.

The MDPS (Motor Driving Power Steering) system according to an embodiment of the present invention includes an MDPS motor unit that generates a motor torque to assist when steering a steering wheel under control of a driver, a steering angle sensor that detects a steering angle of the steering wheel, A control unit that controls the motor torque output from the MDPS motor unit in response to a boost curve based on a parameter, and a vertical load estimated based on the motor torque and the steering angle are monitored in real time to determine the road surface condition, and the determination result Is transmitted to the control unit, and after it is determined as a rough road as the change amount of the vertical load appears for a change duration longer than a preset threshold time, if the change amount continuously increases according to the change trend of the vertical load, low output torque The parameter and the high output torque parameters include an MDPS driving inertia maintenance unit that increases the low output area parameter and decreases the high output area parameter in proportion to the increase in the amount of change in the vertical load, and the control unit can adjust the parameter according to the determination result. have.

In an embodiment, the MDPS driving inertia maintenance unit is a motor torque estimating unit that estimates the motor torque based on a current value of the MDPS motor unit, and a vertical load weight that estimates the vertical load based on the motor torque and the steering angle. It may include a rough road determination unit that monitors the government and the vertical load in real time and detects a time change amount of the vertical load to determine the road surface condition.

In an embodiment, the current value of the MDPS motor unit may be any one of two-phase currents obtained by converting a three-phase current flowing when the MDPS motor unit is driven.

In an embodiment, the rough road determination unit may transmit a variation of the vertical load, a variation duration, and a trend of variation estimated by differentiating the vertical load to the controller as a result of the determination.

The operation method of the MDPS system according to another embodiment of the present invention is a sensing step of generating a motor torque to assist when steering a steering wheel according to a driver's control in the MDPS motor unit, and sensing a steering angle of the steering wheel by a steering angle sensor. , MDPS driving inertia maintenance unit monitors the vertical load estimated based on the motor torque and the steering angle in real time to determine the road surface condition, and transmits the determination result to the control unit. After it is determined as a rough road as the amount of change in the vertical load appears over time, if the amount of change continuously increases according to the change trend of the vertical load, both the low output torque parameter and the high output torque parameter are proportional to the increase amount of the vertical load change amount. An adjustment step of increasing a low power region parameter and reducing a high power region parameter, and an output step of adjusting and outputting the motor torque output from the MDPS motor unit in response to a boost curve based on the parameter in the control unit. .

In an embodiment, the adjusting step may include estimating a motor torque by multiplying any one of two-phase currents obtained by converting the three-phase current flowing when the MDPS motor unit is driven by a motor torque constant.

In an embodiment, the adjusting step may include the step of determining the road surface condition by detecting a time change amount of the vertical load while monitoring the vertical load in real time by the rough road determination unit.

In an embodiment, the adjusting step may include determining the boost curve based on a change amount of the vertical load, a change duration time, and a change trend estimated by differentiating the vertical load by a rough road determination unit. .

According to the MDPS system and its operation method of the present invention, by reflecting and outputting a change amount of a vertical load to a motor torque in real time, straight traveling performance can be secured even when driving on rough roads, and the driver's stability can be further improved.

1 is a block diagram showing the MDPS system of the present invention.
2 is a graph showing a boost curve according to the MDPS system of the present invention.
3 is a flowchart showing a method of operating the MDPS system of the present invention.

Specific structural or functional descriptions of the embodiments according to the concept of the present invention disclosed in the present specification are exemplified only for the purpose of describing the embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention are It may be implemented in various forms and is not limited to the embodiments described herein.

Since the embodiments according to the concept of the present invention can apply various changes and have various forms, the embodiments will be illustrated in the drawings and described in detail in the present specification. However, this is not intended to limit the embodiments according to the concept of the present invention to specific disclosed forms, and includes all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

Terms such as first or second may be used to describe various elements, but the elements should not be limited by the terms. The terms are only for the purpose of distinguishing one component from other components, for example, without departing from the scope of the rights according to the concept of the present invention, the first component may be referred to as the second component, and similarly The second component may also be referred to as a first component.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle. Other expressions describing the relationship between components, such as "between" and "just between" or "adjacent to" and "directly adjacent to" should be interpreted as well.

The terms used in this specification are used only to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present specification, terms such as "comprise" or "have" are intended to designate the presence of a set feature, number, step, action, component, part, or combination thereof, but one or more other features or numbers It is to be understood that the possibility of addition or presence of, steps, actions, components, parts, or combinations thereof is not preliminarily excluded.

Unless otherwise defined, all terms used herein including technical or scientific terms have the same as those generally understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this specification. Does not.

Hereinafter, the present invention will be described in detail by describing a preferred embodiment of the present invention with reference to the accompanying drawings.

1 is a block diagram showing the MDPS system of the present invention, Figure 2 is a graph showing a boost curve according to the MDPS system of the present invention.

Referring to FIG. 1, the MDPS (Motor Driven Power Steering) system according to the present invention may include a steering angle sensor (SAS) 10, a controller 20, and an MDPS driving inertia maintenance unit.

The steering angle sensor 10 may detect a steering angle caused by rotation of a steering wheel according to a driver's control.

The MDPS motor unit 30 may generate motor torque to assist when steering the steering wheel under the control of the driver.

The MDPS driving inertia maintenance unit is capable of determining the road surface condition according to the vertical load estimated based on the motor torque and the steering angle, and transmitting the determination result to the control unit 20, the rough road determining unit 40, the vertical load estimating unit ( 50), may include a motor torque estimating unit 60.

The motor torque estimating unit 60 is capable of estimating the motor torque through the current value flowing through the MDPS motor unit 30, sensing a three-phase current flowing when the MDPS motor unit 30 is driven, and converting it into a two-phase current. , One of them can be multiplied by the motor torque constant to estimate the motor torque.

For example, the motor torque estimating unit 60 may convert a three-phase current into a D-axis/Q-axis current (two-phase current), calculate a Q-axis current, and multiply the motor torque constant to estimate the motor torque.

The vertical load estimating unit 50 estimates the vertical load of the wheel by using the motor torque and steering angle of the MDPS motor unit 30 measured by the motor torque measurement unit 60, and calculates the estimated vertical load value as a rough road determination unit ( 40).

At this time, the vertical load is the friction force applied when the wheel rotates according to the weight of the vehicle or the road surface condition, and the larger the vertical load, the more motor torque is required when trying to rotate the same steering angle. It is proportional, and the value may vary depending on the weight of the vehicle or the condition of the road surface.

For example, the vertical load on rough roads where the road surface condition is not uniformly distributed with stones, gravel, and soil has a larger value than the vertical load of a general road with a uniform road surface, such as an asphalt road, and the amount of change is also variable. will be.

In particular, when the vehicle is traveling on rough roads such as off-road, it is difficult for the driver to safely drive because it is difficult to maintain straight-line driving and driving inertia.

The rough road determination unit 40 may monitor the vertical load calculated through the vertical load estimating unit 50 in real time to determine the road surface condition, and may detect a change in the vertical load to determine the road surface condition.

For example, by detecting the amount of change in the vertical load estimated by differentiating the vertical load, the size of the change amount, the change duration time, and the trend of the change are determined to determine the state of the road surface, and the state of the road surface is transferred to the controller 20 in real time. Transmission so that the variable control of the MDPS motor unit 30 can be performed.

The controller 20 is capable of controlling each component of the MDPS system, and can calculate the motor torque according to the driving environment with respect to the driver's input torque, and can drive straight through the parameters corresponding to the vertical load and the road surface condition. It is possible to variably control the MDPS motor unit 30 to maintain.

That is, the control unit 20 may determine a boost curve, which is a parameter for calculating an output torque for an input torque according to a driving environment (vehicle speed), and the MDPS motor unit 30 in response to the boost curve based on the parameter The motor torque output from can be controlled.

The control unit 20 extracts parameters in real time according to the change data of the vertical load input from the rough road determination unit 40 and desensitizes the motor torque output from the MDPS motor unit 30 according to the boost curve to maintain straight-line driving. You can do it.

In particular, a factor that determines the current boost curve parameter is limited only to the vehicle speed, and a variation factor of the vertical load can be added to this to generate motor torque to further improve the driver's stability.

Referring to FIG. 2, six parameters (p0, p1, p2, p3, p4, p5) can be defined according to the vehicle speed to configure the boost curve. The horizontal axis is the input of the boost curve, and the vertical axis is the boost curve. Is the output of.

The parameters of p0 to p5 shown on the left side of the vertical axis indicate the tendency of the curve, and p0 and p1 are parameters in the low output torque region, which rarely generate output torque to the input torque, and p2, p3, p4, and p5 are high output. As a parameter of the torque area, the degree of output torque generated for the input torque is large.

The controller 20 may determine values of parameters p0 to p5, which are factors for determining a curve, according to a determination result of a change amount, a duration time, a change trend, etc. of the vertical load input from the MDPS driving inertia maintenance unit.

For example, under the condition of changing the vertical load that is judged to be a rough road, the steering output of the steering wheel can be rapidly reduced by changing the tendency of the boost curve from the black curve shown in the graph to the red curve, even at the same vehicle speed. It can improve the running straightness and inertia of.

In order to change the above-described tendency, the mechanism for determining the factors p0 to p5, which is the factor that determines the curve, will be described in more detail. The MDPS system first applies the amount of change according to the time of the vertical load right after the vehicle enters the rough road. If it persists, it can be judged as a rough road.

After judging as a rough road, first, for the parameters (p0, p1) of the low-output torque region of the boost curve, first multiply the time change amount of the vertical load and the duration time, that is, the value of p0 in proportion to the change of the change in the pure vertical load. After that, it is possible to increase the value of p1, which is a slope value that determines an area for activating the low output torque.

In addition, in the MDPS system, in the parameters of the high output torque range (p2 to p5), it is difficult to apply a large amount of input torque by steering the steering wheel when the driver enters the rough road, so parameters p2 to p5 After maintaining the existing boost curve (black curve), it is possible to control p2 to p5 according to changes in rough road conditions.

If the amount of change continues to increase according to the change of vertical load after it is judged as a rough road, the condition of the road surface becomes more severe. Therefore, both the low output torque parameter and the high output torque parameter increase in proportion to the increase in the vertical load change amount. , The high power area parameter can be reduced.

However, if the change trend of the vertical load hardly changes after it is determined as a rough road, it is possible to maintain the boost curve set at the initial entry (the parameter of the increased low power region).

When off the rough road, the variation of the vertical load approaches zero, making it almost impossible to detect, so the MDPS system can output the motor torque in response to the corresponding boost curve by setting it as a parameter for driving a general road surface condition.

At this time, whether or not the vehicle has entered the normal road surface state can immediately output the motor torque of the normal road surface state when the amount of change falls within a preset range without considering the duration of the change of the vertical load.

3 is a flow chart showing a method of operating the MDPS system of the present invention.

Referring to FIG. 3, the MDPS system may turn on the steering inertia maintenance device during rough road driving according to the driver's manipulation (S10).

The steering inertia holding device may have the same configuration as the MDPS traveling inertia holding unit shown in FIG. 1.

When a motor torque is generated according to the driver's steering wheel steering and the steering angle is sensed (S20 and S30), the MDPS system may estimate a vertical load based on the motor torque and the steering angle (S40).

The vertical load is a friction force applied when a wheel rotates according to the weight of the vehicle or the road surface condition, and the value may vary depending on the weight of the vehicle or the road surface condition.

The MDPS system can monitor the vertical load in real time, observe the change, and determine the road surface condition (S50).

That is, it is possible to observe the variation of the vertical load, the change duration, and the trend of the change estimated by differentiating the vertical load.

For example, the vertical load on rough roads where the road surface condition is not uniformly distributed with stones, gravel, and soil will have a larger value than the vertical load of a general road with a uniform road surface, such as an asphalt road, and the amount of change will also change. .

The MDPS system can output by adjusting the motor torque based on the change data of the vertical load.

That is, since the parameters are adjusted according to the road surface condition and the boost curve varies according to the parameters, the MDPS system outputs the motor torque in response to the changed boost curve.

For example, when driving on rough roads, the motor torque output from the MDPS motor unit may be desensitized according to the adjusted boost curve to maintain straight-line driving.

As described above, according to the MDPS system and its operation method of the present invention, by reflecting the amount of change in the vertical load to the motor torque in real time and outputting it, it is possible to secure straight travel even when driving on rough roads, and to further improve the driver's stability. .

Although the present invention has been described with reference to an embodiment shown in the drawings, it is only exemplary, and those of ordinary skill in the art will appreciate that various modifications and other equivalent embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the attached registration claims.

10: steering angle sensor 20: control unit
30: MDPS motor unit 40: rough road determination unit
50: vertical load estimation unit 60: motor torque estimation unit
100: MDPS system 200: driving inertia maintenance unit

Claims (8)

MDPS motor unit for generating a motor torque for assisting when steering the steering wheel under the control of the driver;
A steering angle sensor that senses a steering angle of the steering wheel;
A control unit for controlling the motor torque output from the MDPS motor unit in response to a boost curve based on a parameter; And
By monitoring the vertical load estimated based on the motor torque and the steering angle in real time to determine the road surface condition, and transmitting the determination result to the control unit,
After it is determined as a rough road as the change amount of the vertical load appears during the change duration longer than the preset threshold time, if the change amount continuously increases according to the change trend of the vertical load, both the low output torque parameter and the high output torque parameter An MDPS driving inertia maintaining unit for increasing the low power area parameter and decreasing the high power area parameter in proportion to the increase amount of the vertical load variation;
The control unit MDPS system, characterized in that for adjusting the parameter according to the determination result. The method of claim 1,
The MDPS driving inertia maintenance unit,
A motor torque estimation unit estimating the motor torque based on the current value of the MDPS motor unit;
A vertical load estimation unit estimating the vertical load based on the motor torque and the steering angle; And
MDPS system comprising a rough road determination unit for determining the road surface condition by detecting a time change amount of the vertical load while monitoring the vertical load in real time. The method of claim 2,
The current value of the MDPS motor unit is,
MDPS system, characterized in that any one of the two-phase current converted from the three-phase current flowing when driving the MDPS motor unit. The method of claim 2,
The rough road determination unit,
The MDPS system, characterized in that transmitting the vertical load variation, variation duration, and variation trend estimated by differentiating the vertical load to the controller as a result of the determination. A sensing step of generating a motor torque to assist when steering a steering wheel in accordance with a driver's control in the MDPS motor unit, and sensing a steering angle of the steering wheel by a steering angle sensor;
The MDPS driving inertia maintenance unit monitors the vertical load estimated based on the motor torque and the steering angle in real time to determine the road surface condition, and transmits the determination result to the control unit,
After it is determined as a rough road as the change amount of the vertical load appears during the change duration longer than the preset threshold time, if the change amount continuously increases according to the change trend of the vertical load, both the low output torque parameter and the high output torque parameter An adjustment step of increasing the low-output area parameter and decreasing the high-output area parameter in proportion to the increase in the vertical load change amount; And
An output step of adjusting and outputting the motor torque output from the MDPS motor unit in response to a boost curve based on the parameter in the control unit
MDPS operation method comprising a. The method of claim 5,
The adjustment step,
And estimating a motor torque by multiplying any one of two-phase currents obtained by converting the three-phase current flowing when the MDPS motor unit is driven by a motor torque constant. The method of claim 5,
The adjustment step,
And determining the road surface condition by detecting a time change amount of the vertical load while monitoring the vertical load in real time in a rough road determination unit. The method of claim 5,
The adjustment step,
And determining the boost curve based on a variation of the vertical load, a variation duration, and a trend of variation estimated by differentiating the vertical load by the rough road determination unit.

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