KR102628125B1 - Rack force compensation logic and method in sbw system - Google Patents

Abstract

Surrounding environmental conditions (changes in friction between the ground and tires) are estimated to have changed in road conditions using devices around the vehicle (wiper operation, rain detection, headlight operation) rather than the change in tire friction and the corresponding vehicle dynamics calculation method. A rack thrust control compensation logic and method in an SBW system that compensates for thrust are provided. In the SBW system, the rack thrust compensation logic includes an OR operation unit that performs an OR operation on rain or snow detection information, wiper operation status information, and vehicle ambient illuminance change information to output an environmental change detection signal; an AND operation unit for performing an AND operation on the environmental change detection signal and road surface condition change data from the OR operation unit and outputting an SBW column motor operation control signal; and a control unit that generates a steering reaction force signal for controlling the SWB column motor according to the SBW column motor operation control signal from the AND operation unit.

Description

Rack thrust compensation logic and method in SBW system {RACK FORCE COMPENSATION LOGIC AND METHOD IN SBW SYSTEM}

The present invention relates to an SBW system, and more specifically, to a logic and method for compensating rack thrust in an SBW system.

In general, a power-assisted steering system for reducing the driver's steering force when steering a car is a hydraulic power steering system (HPS: Hydraulic Power) that assists the driver's steering force using hydraulic pressure generated by a hydraulic pump. Steering System) and an electric steering system (MDPS: Motor Driven Power Steering System, hereinafter referred to as 'MDPS') that assist the driver's steering force by using the driving torque of an electric motor are known.

Among these, MDPS performs a steering assistance function according to the driver's steering wheel operation, and the output of the electric motor for steering assistance can be controlled according to the driving conditions of the vehicle, providing improved steering performance and steering feel compared to the hydraulic steering system. do.

Accordingly, MDPS, which can change and control the steering assistance force generated by motor output according to driving conditions, is widely applied to recently released vehicles.

MDPS is a steering angle sensor that detects the steering angle (column input angle) according to steering wheel operation, a torque sensor that detects the steering torque (steering wheel torque, column torque) input through the steering wheel, a vehicle speed sensor that detects vehicle speed, and a wheel speed sensor that detects the steering angle (column input angle) according to steering wheel operation. It can be configured to include sensors such as a sensor, engine speed sensor, and yaw rate sensor, a controller (MDPS ECU), and a steering motor (MDPS motor).

In this configuration, the controller receives steering input information such as steering angle, steering angle speed (angular speed value taken from the derivative signal of the steering angle signal), and steering torque from the sensors to control the driving and output of the steering motor and vehicle status information (vehicle speed, wheel speed, engine speed, yaw rate, etc.).

At this time, the controller controls the driving force (motor output) of the steering motor according to the vehicle speed to generate adjusted auxiliary torque for steering assistance. At low speeds, the motor output is increased to enable the driver to lightly operate the steering wheel. , At high speeds, the motor output is reduced so that the steering wheel can be operated heavily, thereby ensuring the driving stability of the vehicle.

If the steering wheel is too light when driving the vehicle at high speeds, even a slight steering wheel operation can lead to a dangerous situation, resulting in loss of driving stability. Therefore, the steering assistance characteristics are changed depending on the vehicle speed, making the steering wheel more heavy when driving straight at high speeds. It ensures stable steering wheel operation by assisting.

Typically, the output of a steering motor that assists the driver's steering force is achieved by the controller controlling the motor current applied to the steering motor (assist control current amount control).

At this time, the controller basically calculates the amount of current corresponding to the output value (steering system output torque, that is, steering motor output torque) determined based on the steering input information and vehicle status information as tuned and applies it to the steering motor. It generates force to assist the driver's steering force through motor drive.

In the above-mentioned steering system, the components for transmitting the driver's steering force applied through the steering wheel and the steering assistance force generated according to the steering force include a steering column installed at the lower part of the steering wheel and a rotational force transmitted from the steering column. It includes a gearbox that changes the direction of the tire by converting it into straight-line force, and a universal joint to transmit the rotational force transmitted to the steering column to the gearbox.

Here, the gearbox includes a pinion gear that receives rotational force from the universal joint, and a rack bar with a rack on which the pinion gear meshes. When the pinion gear rotates, the rack bar moves straight left and right by the rack. At this time, the force exerted by the left and right straight movement of the rack bar is transmitted to the tire through the tie rod and ball joint, changing the direction of the tire.

Meanwhile, rack force is an important value for steering performance. In order to measure this rack force, a sensor must be attached to the steering gear, which is difficult in terms of cost, layout, and durability, so multiple estimators are used. It is important to accurately predict rack thrust.

Conventionally, the SBW system uses compensation control by estimating the lag tracking change due to the change in tire friction in the surrounding environment (change in friction between the ground and the tire) using a vehicle dynamics model.

Currently, the majority of the steering reaction force provided to drivers in SBW (Steer-By-Wire) systems uses vehicle dynamics modeling to design and estimate mathematical modeling of rack thrust. This estimation technique has many limitations in providing a sense of steering reaction force based on changes in rack thrust according to road environmental conditions. For example, since an accurate estimator (mathematical function) for the estimation technique must be designed to suit the situation, there is an estimator that estimates the change in lag thrust on slippery road surfaces such as snow and rain, and an estimator that estimates lag thrust changes on slightly moist road surfaces such as driving in a tunnel. An estimator is needed in various situations, such as an estimator to estimate thrust changes. To estimate this, there are too many non-linear elements in the dynamic relationship between tires and the road surface, and it also requires reliability of the estimated function and a high-performance MCU (Micro Controller Unit) to calculate it.

Publication Patent No. 10-2017-0065795 {Publication date: June 14, 2017}

The present invention was devised to solve the above-described conventional problems, and is based on the surrounding environmental conditions (changes in friction between the ground and the tires), rather than calculating the friction of the tires and the resulting vehicle dynamics, rather than calculating the vehicle's dynamics (wiper operation, rain detection). The purpose is to provide a rack thrust control compensation logic and method in an SBW system that compensates for rack thrust by estimating that road conditions have changed using headlight operation).

In the SBW system, the rack thrust compensation logic includes an OR operation unit that performs an OR operation on rain or snow detection information, wiper operation status information, and vehicle ambient illuminance change information to output an environmental change detection signal; an AND operation unit for performing an AND operation on the environmental change detection signal and road surface condition change data from the OR operation unit and outputting an SBW column motor operation control signal; and a control unit that generates a steering reaction force signal for controlling the SWB column motor according to the SBW column motor operation control signal from the AND operation unit.

In the SBW system, the rack thrust compensation logic includes a rain sensor that detects rain or snow and outputs a high level signal as the rain or snow detection information; An illumination sensor that detects a change in illumination around the vehicle and outputs a high level signal as information on the change in illumination around the vehicle; and an auxiliary device having a wiper driving unit that drives a wiper, wherein when the wiper driven by the wiper driving unit operates for more than a certain period of time, a high level signal is input to the OR operation unit, and the OR operation unit inputs the lane When output from a sensor, the illuminance sensor, or the wiper driver is input, and at least one of them is at a high level, a high level signal can be output to the AND operator.

The constant time may be 3 seconds. In the SBW system, the rack thrust compensation logic may further include a camera that captures an image of the road surface in front of the vehicle to obtain the road surface condition change data. The road surface condition change data may be at a high level indicating that the road surface condition in front of the vehicle has changed when the brightness of the road surface image in front of the vehicle is greater than the average brightness of the area around the vehicle.

The rack thrust compensation method in the SBW system includes (i) ORing rain or snow detection information, wiper operation status information, and vehicle ambient illuminance change information to output an environmental change detection signal; (ii) performing an AND operation on the environmental change detection signal and the road surface condition change data and outputting an SBW column motor operation control signal; and (iii) generating a steering reaction force signal for controlling the SWB column motor according to the SBW column motor operation control signal.

Step (i) includes (i-1) detecting rain or snow and outputting a high level signal as the rain or snow detection information; (i-2) detecting a change in illuminance around the vehicle and outputting a high level signal as illuminance change information around the vehicle; and (i-3) outputting a high level signal when the wiper operates for more than a certain period of time.

The constant time may be 3 seconds. Step (ii) may include capturing an image of the road surface in front of the vehicle using a camera to obtain the road surface condition change data. The road surface condition change data may be at a high level indicating that the road surface condition in front of the vehicle has changed when the brightness of the road surface image in front of the vehicle is greater than the average brightness of the area around the vehicle.

The present invention deviates from the rack thrust estimation technique of SBW, which is a design of many technologies, and uses a driver's behavior and vehicle awareness sensor according to changes in road conditions to detect changes in the road surface and surrounding environment on which the vehicle is currently driving. Provides an algorithm design recognized by the Controller Unit.

The existing method of estimating the relationship between tires and the road surface using a relationship equation using vehicle dynamics modeling or mathematical modeling of the steering system (tires) is complicated in terms of accuracy and algorithm design, so we boldly break away from this and create a method that simply responds to the driver's driving environment. Using behavior and sensors mounted on the vehicle, we intend to use the road surface condition of the currently driving vehicle as an input value for the SBW rack thrust change recognition algorithm.

This SBW rack thrust change recognition/judgment algorithm output is used to compensate for the generation (reproduction) of the steering reaction force of the SBW column, allowing the driver to know that steering slimness is occurring on rainy or snowy roads, and on roads such as tunnels or underground parking lots. We want to devise a rack thrust compensation algorithm so that you can feel the friction between the tire and the ground under any given condition. Furthermore, we design an algorithm that compensates for the generation (reproduction) of steering reaction force due to changes in rack thrust even in special situations such as puddles and sinkholes using camera image processing technology.

The present invention is more intuitive for road surface changes and does not require computational processing of advanced rack thrust and vehicle dynamics estimation techniques, so it can be implemented without an immediate response or high-performance MCU.

Figure 1 is a diagram showing the configuration of an SBW system according to the present invention.
Figure 2 is a block diagram showing the configuration of rack thrust compensation logic in the SBW system according to the present invention.
FIG. 3 is a diagram illustrating the process of transmitting a state change by the camera shown in FIG. 2.
FIG. 4 is a diagram illustrating a steering reaction force reproduction control process using the rack thrust compensation logic shown in FIG. 2.
Figure 5 is a rack thrust gradient according to an embodiment of the present invention.
Figure 6 is a graph comparing a normal road surface and a changed road surface according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of the rack thrust compensation logic and method in the SBW system according to the present invention will be described with reference to the attached drawings. In this process, the thickness of lines or sizes of components shown in the drawing may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

In addition, the following examples do not limit the scope of the present invention, but are provided merely as examples, and there may be various embodiments implemented through the technical idea of the present invention.

Figure 1 is a diagram showing the configuration of an SBW system according to the present invention.

Figure 2 is a block diagram showing the configuration of rack thrust compensation logic in the SBW system according to the present invention.

Referring to Figures 1 and 2, the rack thrust compensation logic in the SBW system according to the present invention includes an auxiliary device 100, an OR operation unit 200, a camera 300, an AND operation unit 400, and a control unit 500. Includes.

The auxiliary device 100 includes a rain sensor 110, an illumination sensor 120, and a wiper driver 130.

The rain sensor 110 detects rain or snow and outputs a high level signal as rain or snow detection information.

The illuminance sensor 120 detects a change in illuminance around the vehicle and outputs a high level signal as illuminance change information around the vehicle.

The illuminance sensor 120 detects night and day information according to light and tunnels and entrances and exits of tunnels, and transmits the detected information to the OR calculation unit 200. The illuminance sensor 120 confirms that the illuminance has suddenly decreased upon entering the tunnel within 1 second, allowing the user to quickly confirm that the tunnel has been entered. Conversely, the illuminance sensor 120 confirms that the illuminance has suddenly increased within 1 second to confirm that the tunnel has been exited. You can check it quickly.

The wiper driving unit 130 drives a wiper (not shown). The wiper driving unit 130 recognizes the driving of the wiper and the rotational speed of the wire step by step, senses the external environment, and then transmits the sensing information to the OR calculation unit 200. Depending on the rotation speed of the wiper, it is possible to obtain information about the amount of precipitation per hour or the extent to which the driver's field of vision is secured due to the amount of precipitation.

The auxiliary device 100 is a variety of devices and sensors installed in the vehicle to provide the driver's convenience. It is not installed separately to measure the rack thrust value, and existing devices and sensors are used, so the rack thrust value is measured. Since no device for extraction is required, installation costs can be reduced, maintenance costs are reduced, and efficiency is improved.

In addition, the auxiliary device 100 is composed of a combination of the rain sensor 110, the illuminance sensor 120, and the wiper driving unit 130, so that it is more precise and reasonable than deriving an environmental change detection signal with a single auxiliary device. A change detection signal can be derived.

The OR operation unit 200 performs an OR operation on rain or snow detection information, wiper operation status information, and illumination change information around the vehicle and outputs an environmental change detection signal.

When the wiper driven by the wiper driver 130 operates for more than a certain period of time, a high level signal is input to the OR operation unit 200. It is preferable that the above constant time is 3 seconds.

The camera 300 acquires road surface condition change data by capturing an image of the road surface in front of the vehicle.

FIG. 3 is a diagram illustrating the process of transmitting a state change by the camera shown in FIG. 2. Referring to FIG. 3, the road surface condition change data is a high level indicating that the road surface condition in front of the vehicle has changed when the brightness of the road surface image in front of the vehicle is greater than the average brightness of the area around the vehicle.

The AND operator 400 performs an AND operation on the environmental change detection signal and the road surface condition change data from the OR operator 200 and outputs an SBW column motor operation control signal. The OR operator 200 receives the output from the rain sensor 110, the illuminance sensor 120, or the wiper driver 130, and when at least one of them is high level, sends a high level signal to the AND operator. Prints as (400).

The control unit 500 generates a steering reaction force signal for controlling the SWB column motor 20 according to the SBW column motor operation control signal from the AND operation unit 400.

In this case, the control unit 500 controls the driving force (motor output) of the SWB column motor 20 according to the SBW column motor operation control signal to generate adjusted auxiliary torque for steering assistance. At low speeds, the driver The motor output is increased to assist with light operation of the steering wheel, and the motor output is reduced to enable heavy operation of the steering wheel at high speeds to ensure the driving stability of the vehicle. At this time, based on normal road surface conditions, the motor output is further increased to +20%, preferably +10 to +30% in case of snow and rain, and -20%, preferably -10 to -30% in case of concrete and gravel. so that it can be printed.

FIG. 4 is a diagram illustrating a steering reaction force reproduction control process using the rack thrust compensation logic shown in FIG. 2. Figure 5 is a rack thrust gradient according to an embodiment of the present invention.

Figure 6 is a graph comparing a normal road surface and a changed road surface according to an embodiment of the present invention.

In Figure 6, A is the driver's SBW column steering reaction force generation (reproduction) performance curve in a normal road surface condition in clear weather, clear weather, and asphalt road surface conditions, and B is a road surface change state in ice, rainwater, parking lot road surface conditions, etc. This is the driver's SBW column steering reaction force generation (reproduction) performance curve.

One embodiment of the present invention described above is merely illustrative, and those skilled in the art will be able to appreciate that various modifications and other equivalent embodiments are possible. . Therefore, it will be understood that the present invention is not limited to the forms mentioned in the detailed description above. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the attached patent claims. In addition, the present invention should be understood to include all modifications, equivalents and substitutes within the spirit and scope of the present invention as defined by the appended claims.

10: Steering wheel
20: SWB column motor
100: Auxiliary device
110: rain sensor
120: Illuminance sensor
130: Wiper driving part
200: OR operation unit
300: Camera
400: AND operation unit
500: Control unit

Claims (10)

an OR operation unit that performs an OR operation on rain or snow detection information, wiper operation status information, and illumination change information around the vehicle to output an environmental change detection signal;
an AND operation unit for performing an AND operation on the environmental change detection signal and road surface condition change data from the OR operation unit and outputting an SBW column motor operation control signal; and
Rack thrust compensation logic in an SBW system including a control unit that generates a steering reaction force signal for controlling the SWB column motor according to the SBW column motor operation control signal from the AND operation unit.
The method of claim 1, further comprising: a rain sensor that detects rain or snow and outputs a high level signal as the rain or snow detection information;
An illumination sensor that detects a change in illumination around the vehicle and outputs a high level signal as information on the change in illumination around the vehicle; and
It further includes an auxiliary device having a wiper driving unit that drives the wiper,
When the wiper driven by the wiper driving unit operates for more than a certain period of time, a high level signal is input to the OR operation unit,
Rack thrust compensation logic in an SBW system wherein the OR operator receives output from the rain sensor, the illuminance sensor, or the wiper driver, and outputs a high level signal to the AND operator when at least one of them is high level.
delete The rack thrust compensation logic according to claim 1, further comprising a camera for acquiring road surface condition change data by capturing an image of the road surface in front of the vehicle.
The rack thrust compensation logic of claim 4, wherein the road surface condition change data is a high level indicating that the road surface condition in front of the vehicle has changed when the brightness of the road surface image in front of the vehicle is greater than the average brightness of the area around the vehicle.
(i) performing an OR operation on rain or snow detection information, wiper operation status information, and illumination change information around the vehicle to output an environmental change detection signal;
(ii) performing an AND operation on the environmental change detection signal and the road surface condition change data and outputting an SBW column motor operation control signal; and
(iii) A rack thrust compensation method in an SBW system including the step of generating a steering reaction force signal for controlling the SWB column motor according to the SBW column motor operation control signal.
The method of claim 6, wherein step (i) is
(i-1) detecting rain or snow and outputting a high level signal as the rain or snow detection information;
(i-2) detecting a change in illuminance around the vehicle and outputting a high level signal as illuminance change information around the vehicle; and
(i-3) A rack thrust compensation method in an SBW system including outputting a high level signal when the wiper operates for a certain period of time or more.
delete The rack thrust compensation method according to claim 6, wherein step (ii) includes acquiring the road surface condition change data by capturing an image of the road surface in front of the vehicle using a camera.
The rack thrust compensation method according to claim 9, wherein the road surface condition change data is at a high level indicating that the road surface condition in front of the vehicle has changed when the brightness of the road surface image in front of the vehicle is greater than the average brightness of the area around the vehicle.

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