US-12617457-B2 - Device for and method of compensating for disturbance in rack force

US12617457B2US 12617457 B2US12617457 B2US 12617457B2US-12617457-B2

Abstract

Disclosed is a device for compensating for a disturbance in a rack force. The device includes a memory that stores instructions, and processors that determine an optimally estimated value of a rack force for minimizing an error representing a difference between an actual value of the rack force and an estimated value of the rack force, extract a specific frequency component from the optimally estimated value of the rack force, and compensate for the extracted specific frequency component to the actual value of the rack force to remove a disturbance reflected in the actual value of the rack force.

Inventors

Ji Sung KIM

Assignees

HYUNDAI MOBIS CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20230327
Priority Date: 20221005

Claims (11)

1 . A device for compensating for a disturbance in a rack force, the device comprising: a memory configured to store one or more instructions; and one or more processors configured to execute the one or more instructions to: determine an optimally estimated value of a rack force for minimizing an error calculated as a difference between an actual value of the rack force and an estimated value of the rack force, wherein the one or more processors are configured to determine the optimally estimated value by iteratively adjusting one or more parameters of an estimated rack force model using a gradient-based optimization algorithm to minimize said error; extract a specific frequency component from the optimally estimated value of the rack force; and compensate for the extracted specific frequency component to the actual value of the rack force to remove a disturbance reflected in the actual value of the rack force.
2 . The device of claim 1 , wherein the one or more processors are further configured to execute an optimization algorithm to minimize the error and determine the optimally estimated value of the rack force.
3 . The device of claim 2 , wherein the one or more processors are further configured to: define an objective function based on the error; and apply the optimization algorithm to a gradient of the objective function to determine the optimally estimated value of the rack force.
4 . The device of claim 1 , wherein the optimally estimated value of the rack force includes a linear component and a vibration component, and wherein the specific frequency component is the vibration component included in the optimally estimated value of the rack force.
5 . The device of claim 4 , wherein the one or more processors are further configured to: subtract the vibration component from the actual value of the rack force to remove the disturbance from the actual value of the rack force.
6 . A method of compensating for a disturbance in a rack force, the method comprising: determining, by a processor, an error calculated as a difference between an actual value of a rack force and an estimated value of the rack force; determining, by the processor, an optimally estimated value of the rack force for minimizing the error, wherein determining the optimally estimated value comprises iteratively adjusting one or more parameters of an estimated rack force model using a gradient-based optimization algorithm to minimize said error; and removing, by the processor, a disturbance reflected in the actual value of the rack force based on subtracting a specific frequency component included in the optimally estimated value of the rack force from the actual value of the rack force.
7 . The method of claim 6 , wherein determining the optimally estimated value of the rack force further comprises: executing an optimization algorithm to minimize the error and determine the optimally estimated value of the rack force.
8 . The method of claim 7 , wherein determining the optimally estimated value of the rack force further comprises: defining an objective function based on the error, and applying the optimization algorithm to a gradient of the objective function to determine the optimally estimated value of the rack force.
9 . The method of claim 6 , wherein the optimally estimated value of the rack force includes a linear component and a vibration component, and wherein the specific frequency component is the vibration component included in the optimally estimated value of the rack force.
10 . The method of claim 9 , further comprising: subtracting the vibration component from the actual value of the rack force to remove the disturbance from the actual value of the rack force.
11 . A steer-by-wire system comprising: a steering wheel; a reaction-force actuator connected to the steering wheel and configured to apply a reaction torque to the steering wheel; a steering actuator connected to steered wheels and configured to steer the steered wheels; a sensor configured to detect a rack force applied to a rack bar connected to the steered wheels; and a device for compensating for a disturbance in the rack force, the device comprising: a memory configured to store one or more instructions; and one or more processors configured to execute the one or more instructions to: determine an optimally estimated value of the rack force for minimizing an error calculated as a difference between an actual value of the rack force and an estimated value of the rack force, wherein the one or more processors are configured to determine the optimally estimated value by iteratively adjusting one or more parameters of an estimated rack force model using a gradient-based optimization algorithm to minimize said error; extract a specific frequency component from the optimally estimated value of the rack force; and compensate for the extracted specific frequency component to the actual value of the rack force to remove a disturbance reflected in the actual value of the rack force, wherein a controller is configured to control the reaction-force actuator based on the compensated rack force to apply the reaction torque to the steering wheel.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit under 35 USC § 119(a) of Korean Patent Application No. 10-2022-0126971, filed on Oct. 5, 2022, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. BACKGROUND 1. Field The present disclosure relates to a device for and a method of compensating for a disturbance in a rack force, the device and the method being capable of minimizing a delay in acquiring an estimated value of a rack force, and removing a disturbance reflected in the estimated value of the rack force. 2. Description of Related Art Power steering systems have been developed and used to assist a driver in operating a steering wheel in driving a vehicle. The power steering systems are categorized into a hydraulic steering system that uses a hydraulic force, a motor-driven hydraulic steering system that uses the hydraulic force and an electromotive force of a motor at the same time, a motor-driven steering system that uses only the electromotive force of the motor, and the like. In recent years, steer-by-wire (SBW) systems have been developed and used. In SBW systems, a mechanical connection, such as a steering column, a universal joint, or a pinion shaft, between a steering wheel and a vehicle wheel is removed, and vehicle steering is performed by controlling driving of the motor connected to a rack bar using an electrical signal. In SBW systems, a rotational signal of the steering wheel is received through an electronic control unit (ECU), and a steering assistant motor (hereinafter referred to as a “steering motor”) connected to the drive wheel is operated based on the received rotational signal, thereby steering the vehicle. SBW systems do not have a mechanical connection structure of an existing steering system. Thus, SBW systems have the advantage of increasing the degree of layout design freedom varying with a configuration of a steering system, improving fuel efficiency, removing a disturbance input in the reverse direction from the vehicle wheel, and the like. For control in the traverse direction of the vehicle and control of the degree of a feeling of steering, it is very important to recognize a transverse force (a force transferred to a rack bar=a rack force) on an inner surface of a tire because the transverse force exerts a great influence on the control of the degree of the feeling of steering, as well as the control of the vehicle. In SBW systems, there is a need to measure or estimate the rack force and to notify the driver of information on a road surface. Accordingly, in SBW systems, a transverse force of a front wheel that is steered is estimated and measured. For example, the rack force may be estimated by estimating the transverse force through a vehicle dynamics model, or using a steering system model. In the case of a value of the rack force that is estimated in this manner, due to various causes, such as a mechanism of the SBW system and a state of a road surface, a specific frequency signal may be amplified or a disturbance may occur. A steering-wheel reaction force is determined by the estimated value of the rack force, and thus the disturbance decreases the degree of a feeling of steering that the driver experiences. Accordingly, a filter, such as a low pass filter, a notch filter, or a Kalman filter is used in order to remove the disturbance from the estimated value of the rack force. SUMMARY This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. In one general aspect, a device for compensating for a disturbance in a rack force is provided. The device includes a memory that stores instructions, and processors that determine an optimally estimated value of a rack force for minimizing an error representing a difference between an actual value of the rack force and an estimated value of the rack force, extract a specific frequency component from the optimally estimated value of the rack force, and compensate for the extracted specific frequency component to the actual value of the rack force to remove a disturbance reflected in the actual value of the rack force. The processors may execute an optimization algorithm to minimize the error and determine the optimally estimated value of the rack force. The processors may define an objective function based on the error, and apply the optimization algorithm to a gradient of the objective function to determine the optimally estimated value of the rack force. The optimally estimated value of the rack force may include a linear component and a vibration component, and the specific frequency component may be the vibration component included in th