EPS zero calibration system and calibration method

Abstract

The invention relates to an EPS zero calibration system and calibration method. The system comprises a vehicle positioning device, a computer with a calibration program, an OBD system and a steering wheel positioner. The method comprises the steps that at an independent calibration station, a computer is used for being connected with an OBD, the positioning device is controlled to make a vehicle go straight, after the steering wheel positioner confirms that the direction is centered, a calibration program is operated, an instruction is sent to the EPS controller through the OBD, calibration is started after handshake verification, a corner value is read and set to be a zero point, calibration succeeds after success, and if not, it is prompted that calibration is not completed. If the calibration is successful, the fault code is cleared and the instrument lamp is extinguished. The method is suitable for new vehicle calibration or re-calibration.

Description

Technical Field

[0001] The invention relates to an EPS zero position calibration system and a calibration method, belonging to the technical field of automobiles. Background Art

[0002] Steering performance is one of the decisive factors for vehicle operation stability and driving safety. The vehicle needs to be able to maintain straight driving during driving. Generally, when the steering wheel is straightened, that is, the steering wheel angle is 0°, the vehicle should maintain straight driving. At this time, the left and right wheels of the vehicle are symmetrical, and the meshing point of the steering rack is at the midpoint of the effective travel of the rack, that is, at zero position. However, during the assembly process of the vehicle, there is no accurate and effective means to align the steering wheel angle of 0° with the midpoint of the effective travel of the steering rack. Therefore, it is necessary to calibrate the steering wheel angle zero position to ensure the symmetry of the left and right steering of the steering wheel.

[0003] At the beginning of the project, two calibration methods were developed according to different configurations of vehicle models. The zero-position self-learning calibration method was used for vehicles equipped with corner sensors, and the diagnostic instrument was used to calibrate the vehicles without corner sensors. The two calibration methods had different operating methods, and on-site workers complained significantly. In addition, EPS zero-position learning often failed due to improper operation or missed operation, which required engineers or supplier technicians to manually troubleshoot and calibrate offline, which was time-consuming and labor-intensive. Summary of the invention

[0004] The purpose of the present invention is to propose a system and a calibration method for EPS zero position calibration in view of the problems in the prior art, which has the characteristics of simple operation, fast production cycle, accurate calibration, etc. The calibration program is integrated with other existing vehicle controller calibration programs, and there is no need to develop dedicated calibration software.

[0005] The first aspect of the present invention provides a zero position calibration system for EPS, which is independent of the four-wheel alignment system and includes: a vehicle positioning device, a computer device storing a calibration program, an on-board diagnostic system OBD, and a steering wheel positioning device; The vehicle positioning device is provided with two groups of cylinders for adjusting the vehicle body to a straight-line driving state and maintaining it. The opening and closing of the cylinders can be controlled by operating the calibration software on the computer equipment. When adjusting the vehicle through the cylinders, in order to avoid excessive force applied by the cylinders on the tires, which may cause deformation of the wheels and steering system components and cause calibration deviations, the vehicle positioning device arranges a roller group parallel to the longitudinal plane of the wheel under the wheel, which also avoids sliding wear on the tire.

[0006] The computer device storing the calibration program stores the EPS zero position calibration program. The computer device is connected to the on-board diagnostic system OBD through an adapter cable to achieve communication with the vehicle CAN network. The EPS calibration program is integrated with other controller calibration programs into a version of software. The software automatically executes the calibration routines one by one in a predetermined order, and can also execute the calibration routines for EPS separately. After executing the EPS calibration routine, the computer device receives EPS feedback information. If the calibration is successful, the display screen of the computer device displays "calibration successful". If it fails, it displays "calibration incomplete". After the calibration is completed, the computer device sends a clear fault code instruction. After executing the calibration routine, the computer device stores the relevant message in a specific location in the computer for calling, reading and analysis.

[0007] The steering wheel positioning device includes a steering wheel adjustment gauge and a steering wheel fixing bracket, which are used to adjust the steering wheel to the center position and fix the steering wheel; after the vehicle completes the four-wheel alignment, it moves to the calibration station, the worker straightens the steering wheel and places the steering wheel adjustment gauge on the top of the three-spoke steering wheel, and two claws extend from the bottom of the steering wheel adjustment gauge, respectively clamping under the left and right spokes of the steering wheel to ensure that the steering wheel fixing device is directly above the steering wheel and maintains it; so as to accurately calibrate the steering wheel position. A signal transmitting device is arranged on the steering wheel positioning device, which communicates with the computer device storing the calibration program in real time, and displays the position status of the steering wheel through the red and green status bar on the computer interface. When the status bar displays green, the steering wheel is in the center position. At this time, the steering wheel is fixed with the steering wheel fixing bracket to prevent the steering wheel from rotating during the calibration process and ensure the accuracy of zero position calibration.

[0008] Furthermore, the vehicle positioning system includes an adjustment cylinder and a roller group arranged on the plane of the test bench. The adjustment cylinder is divided into two groups, front and rear, distributed on the inner side of the left and right wheels of the front and rear axles of the vehicle, and the cylinder spacing can be adjusted according to the wheelbase and track of different models. The roller group is arranged on both sides of the adjustment cylinder, and is composed of a number of rollers arranged in parallel, and the rolling direction of the roller is perpendicular to the forward direction of the vehicle. The vehicle positioning device is controlled by a switch integrated in the calibration software. After the vehicle completes the four-wheel alignment, it moves to the calibration station. The worker controls the cylinder to open through the switch on the calibration software to adjust the vehicle to a straight driving state. The roller group is arranged under the tire to avoid deformation of the tire and steering gear tie rod due to excessive cylinder force, thereby ensuring calibration accuracy.

[0009] Furthermore, the computer device is connected to the on-board diagnostic system (OBD) through an adapter cable. When the calibration software executes the EPS zero-position calibration routine, a start calibration instruction is issued, which is converted into a corresponding instruction signal according to the communication protocol by the on-board diagnostic system (OBD) and sent to the EPS controller. The EPS controller responds to the instruction and performs handshake interaction with the computer device. After the key decryption is successful, the EPS controller determines whether the conditions for starting the calibration are met. The calibration result is sent by the EPS controller in the form of a message. The computer device parses the message into a Chinese pop-up window "calibration successful" or "calibration incomplete". After the EPS calibration is successful, the fault code clearing instruction is executed to clear the "EPS zero position uncalibrated" fault, and the instrument fault light is turned off; if the calibration is unsuccessful, the fault clearing instruction is not executed, and the instrument fault light remains on. The calibration process is stored in a predetermined location in the computer in the form of a message, and the reason for the unsuccessful calibration can be analyzed by querying the message.

[0010] In a second aspect of the present invention, an EPS zero position calibration method is proposed based on the EPS zero position calibration system, which can be applied to the first calibration of a newly launched vehicle, or the secondary calibration of a required vehicle, and includes the following steps: After the vehicle completes the four-wheel alignment at the first station, the vehicle moves to the second station for calibration; Operate the calibration program on the computer device to open the cylinder to adjust the vehicle to a straight-line driving state, and connect the computer device to the on-board diagnostic system OBD; Place the steering caliper on the steering wheel and center and fix the steering wheel adjustment value; The computer device is operated to send a start calibration instruction, execute a calibration routine, calibrate the position of the steering wheel at this time as the zero point of the steering angle and store it in the controller.

[0011] Furthermore, the EPS zero position calibration routine includes the following processes: the computer issues a calibration start instruction, and the on-board diagnostic system (OBD) converts the signal into a corresponding instruction signal according to the communication protocol and sends it to the EPS controller; the EPS control responds to the instruction, and performs handshake interaction with the computer. After the key decryption is successful, the EPS controller determines whether the calibration start condition is met; if the calibration condition is met, the EPS control reads the angle value of the angle sensor, and calibrates the direction position corresponding to the angle value as the angle zero point; the EPS controller feeds back the calibration result, and the computer device parses the received message into a Chinese pop-up window "calibration successful"; executes the fault code clearing instruction, clears the "EPS zero position uncalibrated" fault, and the instrument fault light goes out; if the calibration condition is not met, or any fault occurs during the calibration process, resulting in the calibration failure, "calibration is not completed" is displayed, and the instrument fault light remains. The calibration process is stored in a predetermined location in the computer in the form of a message to support subsequent analysis of the calibration process.

[0012] Furthermore, the conditions for starting calibration include the following: power state IGN on; vehicle speed is lower than a threshold; voltage is within the CAN communication voltage range; keep the steering wheel in a centered position, and keep the steering wheel position fixed during the calibration process; in particular, when the vehicle speed signal times out or is invalid, it is assumed that the judgment conditions of the relevant message meet the conditions for executing the calibration routine. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present application will be further described below in conjunction with the accompanying drawings; Figure 1 This is a simplified on-site diagram of the EPS zero calibration system; Figure 2 Basic flow chart for EPS zero calibration; Figure 3 Repeat the Zero Calibration Flowchart for the EPS. DETAILED DESCRIPTION

[0014] Example 1 To ensure the symmetry of left and right steering, when the vehicle is driving in a straight line, the meshing point of the steering rack should be located at the midpoint of the effective length of the rack, and the steering wheel should also be in the center position, that is, the steering wheel angle should be 0°. To achieve this state, this example provides an EPS zero position calibration system and calibration method.

[0015] In this example, the four-wheel alignment and EPS calibration are carried out in two stations, SP01 and SP02. Figure 1 As shown in the figure, the EPS zero position calibration and the calibration of other controllers are integrated into the SP02 station, which simplifies the operation of the four-wheel alignment SP01 station, effectively avoids the problems of wrong operation and missed operation, and improves the production rhythm of the inspection line.

[0016] Specifically, before zero-position calibration, the vehicle must complete four-wheel alignment at the SP01 station. For the vehicle involved in this example, the four-wheel alignment is mainly to adjust the front wheel alignment parameters according to the standard. Four-wheel alignment is an important guarantee for vehicle driving stability and reliability, and is also the basic prerequisite for zero-position calibration of EPS. Zero-position calibration after completing four-wheel alignment can ensure that when the steering wheel is turned to the zero position of the corner, the vehicle is in a straight-line driving state to prevent the vehicle from running off the track. At the same time, zero-position calibration also has an important impact on steering return performance and steering assistance.

[0017] The EPS zero-position calibration system provided in this example mainly includes a vehicle positioning device, a steering wheel positioning device, a computer device storing a calibration program, and an on-board diagnostic system (OBD). After the vehicle travels to the calibration station SP02, the computer is operated to open the two sets of adjustment cylinders on the vehicle positioning device. The two sets of cylinders are respectively located on the inner sides of the left and right wheels of the front and rear axles. The cylinders are opened to support the inner sides of the wheels to adjust the vehicle body to a straight-line driving state and maintain it, while ensuring the symmetry of the front left and right wheels of the vehicle. In order to avoid deformation of the tire and steering rod caused by excessive cylinder force during the support process, which affects the calibration accuracy, a roller group is added to the vehicle positioning device. The roller group is located under the tire to avoid sliding friction between the tire and the plane of the vehicle positioning device stand, thereby reducing the force deformation of the tire and the steering rod. Exemplarily, the cylinder on the vehicle positioning device can be adjusted according to different wheelbases and track widths to meet the calibration requirements of different models.

[0018] Specifically, the steering wheel positioning device includes a steering wheel adjustment caliper and a steering wheel fixing bracket. After the vehicle is adjusted to a straight-line driving state by the vehicle positioning device, the steering wheel is adjusted to a centered position by the steering wheel positioning device. Exemplarily, the steering wheel adjustment caliper is placed at the top of a three-spoke steering wheel, and two claws extend from the bottom of the caliper to clamp the bottom of the left and right spokes of the steering wheel, respectively, to ensure that the steering wheel adjustment caliper is directly above and maintained relative to the steering wheel. A signal transmitting device is arranged on the steering wheel adjustment caliper, which communicates with the computer device storing the calibration program in real time, and displays the position status of the steering wheel through a red and green status bar on the computer interface. When the status bar displays green, the steering wheel is in a centered position. At this time, the steering wheel is fixed by the steering wheel fixing bracket to prevent the steering wheel from rotating during the calibration process, thereby ensuring the accuracy of zero-position calibration.

[0019] Specifically, the EPS zero position calibration program and the calibration programs of other controllers are integrated into the same calibration software and stored in a computer device at the production line. To facilitate the operation of the production line workers, the calibration routines in the calibration software are executed in a predetermined order after the calibration starts, and no operation is required during this process. The computer device is connected to the on-board diagnostic system (OBD) through a communication bus to achieve communication with the EPS controller.

[0020] Specifically, after completing the four-wheel alignment and the above-mentioned body and steering wheel position adjustment, the calibration process begins, such as Figure 2As shown, the production line worker operates the computer to send a calibration start command, which is converted into a corresponding command signal according to the communication protocol through the on-board diagnostic system (OBD) and sent to the EPS controller. The EPS controller responds to the command and interacts with the computer by handshake. After the key decryption is successful, the EPS control determines whether the calibration start conditions are met. If the calibration start conditions are met, the EPS controller reads the steering angle value of the steering angle sensor in this state, and calibrates the steering wheel position corresponding to this steering angle value as the steering angle zero point, and feeds back the calibration result to the computer. The computer interprets the received message as a Chinese pop-up window "Calibration successful", executes the clear fault code command, clears the "EPS zero position uncalibrated" fault, and the instrument steering fault light goes out; if any fault occurs during the calibration process and causes the calibration to fail, it will display "Calibration not completed", and the uncalibrated fault code is not clear, the instrument fault light remains, and other subsequent calibration routines continue to be executed. All processes of the calibration routine formulated by the calibration software are stored in the predetermined location of the computer in the form of messages, and the calibration process can be analyzed and determined based on the message data later.

[0021] More specifically, the conditions for starting the EPS calibration include the power state IGN on; the vehicle speed is lower than the threshold; the voltage is within the CAN communication voltage range; in particular, when the vehicle speed signal is timed out or invalid, the judgment conditions of the default related message meet the conditions for executing the calibration routine. Exemplarily, the effective vehicle speed range during the calibration process is 0km / h to 5km / h, and the preset voltage range is 7V to 16V.

[0022] The EPS zero-position calibration system and calibration method provided in this example have been tested on the production line and successfully mass-produced. They can be used for the first calibration of new vehicles off the production line, and can also be used for secondary calibration of vehicles in need. If the vehicle has a replacement of the front axle or the steering gear, the four-wheel alignment and the steering gear need to be readjusted and calibrated. Specifically, when performing a secondary calibration of the steering gear, the computer can be operated to execute the EPS zero-position calibration routine alone without executing other calibration routines. Optional, such as Figure 3 As shown, when performing the secondary zero calibration, you can choose to directly overwrite the previous calibration result or execute a clear instruction first and then recalibrate. In the calibration method provided in this example, you can choose to directly overwrite the previous calibration result.

[0023] The examples described above are several implementation methods of the present application. In addition to these examples, the present application has other implementation methods. All technical solutions that adopt equivalent replacement or equivalent transformation form fall within the protection scope of the present application.

Claims

1. A zero position calibration system for EPS, characterized in that: The system is independent of the four-wheel alignment system, and includes: a vehicle alignment device, a computer device storing a calibration program, an on-board diagnostic system OBD, and a steering wheel alignment device; The vehicle positioning device is provided with two groups of cylinders for adjusting the vehicle body to a straight-line driving state and maintaining it, and the opening and closing of the cylinders can be controlled by operating the calibration software on the computer device; the vehicle positioning device is provided with roller groups parallel to the longitudinal plane of the wheels under the wheels; The computer device storing the calibration program stores the EPS zero position calibration program, and the computer device is connected to the on-board diagnostic system OBD through an adapter cable to achieve communication with the vehicle CAN network; The steering wheel positioning device includes a steering wheel adjustment caliper and a steering wheel fixing bracket, which are used to adjust the steering wheel to a centered position and fix the steering wheel; the steering wheel adjustment caliper is placed at the top of a three-spoke steering wheel, and two claws extend from the bottom of the steering wheel adjustment caliper, respectively clamping under the left and right spokes of the steering wheel; a signal transmitting device is arranged on the steering wheel positioning device, which communicates with the computer device storing the calibration program in real time, and displays the position status of the steering wheel through a red and green status bar on the computer interface.

2. The zero position calibration system of EPS according to claim 1, characterized in that: The adjustment cylinders are divided into two groups, front and rear, which are distributed on the inner sides of the left and right wheels of the front and rear axles of the vehicle, and the cylinder spacing can be adjusted according to the wheelbase and track of different models; the roller group is arranged on both sides of the adjustment cylinder, and is composed of a number of rollers arranged in parallel, and the rolling direction of the rollers is perpendicular to the forward direction of the vehicle; the vehicle positioning device is controlled by a switch integrated in the calibration software. After the vehicle completes the four-wheel alignment, it moves to the calibration station. The worker controls the cylinder to open through the switch on the calibration software to adjust the vehicle to a straight driving state. The roller group is arranged under the tire.

3. An EPS zero-position calibration method adapted to the EPS zero-position calibration system of claim 1, which can be applied to the first calibration of a newly rolled-off vehicle, or to the secondary calibration of a vehicle in need, characterized in that: After the vehicle completes the four-wheel alignment at the first station, the vehicle moves to the second station for calibration; Connect the computer to the on-board diagnostic system OBD, operate the computer calibration program to open the cylinder on the vehicle positioning device, and adjust the vehicle to a straight-line driving state; Place the steering wheel positioning device on the steering wheel, adjust the steering wheel to the center position, and fix the steering wheel; The computer device is operated to send a start calibration instruction, execute the EPS zero position calibration routine, calibrate the position of the steering wheel at this time as the zero point of the steering angle and store it in the controller.

4. The EPS zero position calibration method according to claim 3, characterized in that: The EPS zero-position calibration routine includes the following processes: the computer sends a start calibration command, which is converted into a corresponding command signal according to the communication protocol through the on-board diagnostic system OBD and sent to the EPS controller. The EPS responds to the command and shakes hands with the computer. After successful decryption with the key, it determines whether the start calibration conditions are met. If the conditions are met, the steering angle value of the steering angle sensor is read, and the steering wheel position corresponding to this steering angle value is calibrated as the steering angle zero position. The EPS controller feeds back the calibration result, and the computer parses the received message as a Chinese pop-up window indicating successful calibration. At the same time, a command to clear the EPS zero-position uncalibrated fault code is sent, and the instrument fault light goes out. If the calibration conditions are not met, or any fault occurs during the calibration process and the calibration is not completed, the calibration is not completed and the instrument fault light remains on.

5. The EPS zero position calibration method according to claim 3, characterized in that: EPS responds to the calibration command and determines whether the conditions for starting calibration are met, including: power status IGN on; vehicle speed is lower than the threshold; voltage is within the CAN communication voltage range; keep the steering wheel in the center position and keep the steering wheel position fixed during the calibration process.

6. The EPS zero position calibration method according to claim 5, characterized in that: When the vehicle speed signal times out or is invalid, it is assumed that the judgment condition of the relevant message meets the condition for executing the calibration routine.

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