An electric power steering system for a converted vehicle and a control method thereof

Abstract

The application discloses a kind of retrofit electric power steering systems and its control method, including control module ECU, torque sensor, the steering and torque size of steering wheel detected by the torque sensor are sent to control module ECU, the system also includes vehicle speed simulation module, the output of the vehicle speed module is connected control module ECU;Vehicle speed simulation module outputs vehicle speed signal to control module ECU;Control module ECU controls the operation of electric power steering system and provides assistance power.The application can be characterized by different voltage signals by the mode of knob switch according to the demand of user, then different vehicle speed signal values EPS are sent by CPU, so as to realize the purpose that the steering assistance of user can be independently adjusted, and is suitable for the modification of electric power steering system that retrofit vehicle cannot directly modify VCU, to avoid large changes to ECU.

Description

Technical Field

[0001] This invention relates to the field of electric power steering, for vehicle modification to add electric power steering, and particularly to an electric power steering system for modified vehicles and its control method. Background Technology

[0002] Electric power steering (EPS) represents the future direction of automotive steering systems. This system provides steering assistance directly through an electric motor, eliminating the need for the power steering pump, hoses, hydraulic fluid, transmission belt, and pulley mounted on the engine—all essential components of hydraulic power steering. This saves energy and protects the environment. Furthermore, it offers advantages such as simple adjustment, flexible assembly, and the ability to provide steering assistance in various conditions. With these strengths, EPS, as a new steering technology, is poised to challenge the well-established hydraulic steering system, which has been around for over 50 years.

[0003] When the driver steers, the torque sensor detects the steering wheel's direction and torque magnitude, sending a voltage signal to the electronic control unit (ECU). Based on the torque voltage signal, steering direction, and vehicle speed detected by the torque sensor, the ECU sends a command to the motor controller, causing the motor to output a corresponding amount and direction of steering assist torque, thus generating auxiliary power. When the car is not steering, the ECU does not send a command to the motor controller, and the motor does not operate.

[0004] While the vehicle's design doesn't require speed-sensitive power steering, drivers often desire the ability to manually switch between different modes to adjust steering wheel weight for a superior driving experience. Directly integrating an electric power steering system doesn't meet this design requirement. Adding a VCU (Variable Adjustable Controller Unit) during aftermarket modification would require significant alterations, and since the VCU is a core component, OEMs generally prohibit unauthorized modifications. This prevents the possibility of retrofitting with an electric power steering system, thus failing to satisfy users' demands for variable power steering. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an electric power steering system and control method for modified vehicles, applicable to modified vehicles, so that the electric power steering of the modified vehicles can be adjusted.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an adjustable electric power steering system, comprising a control module ECU and a torque sensor, wherein the torque sensor sends the detected steering wheel direction and torque magnitude to the control module ECU; the system further comprises a vehicle speed simulation module, the output of which is connected to the control module ECU; the vehicle speed simulation module outputs a vehicle speed signal to the control module ECU; and the control module ECU controls the power steering motor of the electric power steering system to provide power assistance.

[0007] The vehicle speed simulation module includes a rotary switch, a central processing unit (CPU), and a CAN module. The rotary switch is connected to the CPU, and the CPU outputs different vehicle speed simulation signals to the control module (ECU) through the CAN module based on the voltage signal input from the rotary switch.

[0008] The vehicle's IG power supply module is connected to the input terminal of the power circuit after passing through the anti-reverse diode. The input terminal of the power circuit is connected to the CPU to supply power to the CPU.

[0009] The input terminal of the central controller CPU is connected to the fault signal acquisition module, and the output terminal of the central controller CPU is connected to the fault indicator light, which is used to drive the illumination state of the fault indicator light according to the fault signal.

[0010] The fault signal acquisition module includes a voltage signal acquisition module, through which the central processing unit (CPU) acquires the voltage signal of the IG power supply module.

[0011] The fault signal acquisition module includes a rotary switch fault monitoring module, whose output is connected to the input of the central controller CPU, and is used to determine whether the rotary switch is faulty based on the acquired rotary switch signal.

[0012] The central processing unit (CPU) monitors the CAN module to determine its operating status.

[0013] The central processing unit (CPU) is connected to the fault signal output terminal of the EPS control module (ECU) to obtain the EPS fault signal. If the received status signal indicates that the current EPS is not running normally or that the EPS is faulty, it is determined to be an EPS fault. The fault LED lights up until the status signal shows that the EPS is normal, and then the fault LED lights off.

[0014] When the central controller CPU determines that the speed control knob is faulty, it sends a vehicle speed signal via the CAN module that corresponds to the preset minimum assist speed.

[0015] When the central controller CPU detects an undervoltage fault in the power supply, it sends a signal value corresponding to the maximum assist speed provided by the EPS to the control module ECU via the CAN module.

[0016] A control method for an electric power steering system in a modified vehicle, the control method comprising: after the system is installed on the modified vehicle, the control module ECU outputs corresponding power assistance based on the collected torque signal and vehicle speed simulation signal.

[0017] The advantages of this invention are: the circuit structure is simple, and the corresponding vehicle speed signal can be represented by different voltage signals through a knob switch according to the user's needs. Then, the CPU sends different vehicle speed signals to the EPS, thereby realizing the user's goal of self-adjusting steering assistance. It is suitable for the modification of electric power steering systems in modified vehicles where the VCU cannot be directly modified, avoiding major modifications to the ECU, meeting more of the vehicle's needs for EPS, and adding the function of EPS to adjust the steering wheel weight. Attached Figure Description

[0018] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0019] Figure 1 A schematic diagram showing the connection structure between the vehicle's IG wiring harness and the present invention and EPS-ECU;

[0020] Figure 2 This is the main flowchart of the software of the present invention;

[0021] Figure 3 This is a hardware block diagram of the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments.

[0023] The purpose of this invention is to enable vehicles that cannot provide vehicle speed signals to the electric power steering system, or vehicles equipped with electric power steering systems that do not require speed-sensitive power steering but desire adjustable steering wheel force, to use electric power steering systems or meet the specific requirements of electric power steering systems. The technical solution is as follows: a vehicle speed simulation module is used to simulate and send vehicle speed to the EPS. This application designs a CAN-BOX for the vehicle speed simulation module to achieve this purpose. The speed-adjustable CAN-BOX simulates vehicle speed and sends it to the EPS to achieve this purpose. The solution includes: providing vehicle speed signals to the vehicle controller (VCU) instead of the traditional vehicle speed signal provided to the electric power steering system control module (ECU); an LED fault light that reflects the operating status of the speed-adjustable CAN-BOX at any time; and a 5-speed adjustment knob that can change the preset vehicle speed.

[0024] Providing vehicle speed signals specifically includes: pre-setting the vehicle speed communication protocol between the vehicle and the desired electric power steering system (hereinafter referred to as EPS) in the speed control CAN-BOX; adjusting the knob installed on the housing of the speed control CAN-BOX to send different vehicle speed signals to the EPS instead of the VCU; and the EPS providing different steering assistance after receiving the vehicle speed signal.

[0025] Adjusting the speed control knob to change the preset vehicle speed includes: when the preset vehicle speed is reached, the corresponding desired vehicle speed is set for different gears of the speed control knob, and the speed control CAN-BOX sends different vehicle speed signals to the EPS by recognizing the current gear of the driver's adjustment knob.

[0026] The LED fault lights that indicate the operating status of the speed control CAN-BOX specifically include: to prevent the speed control CAN-BOX from failing, which could lead to abnormal EPS operation and sudden changes in steering wheel force, the fault LED lights will illuminate to remind the driver if any condition is missing, incorrect, or if the EPS operating status reports an error.

[0027] The necessary conditions for the normal operation of the speed control CAN-BOX and the current operating status of the EPS include: The operating voltage of the speed control CAN-BOX: It can operate normally within a voltage range of 8-16V. Under a voltage range of 6-8V, the speed control CAN-BOX enters a failure mode and sends a preset specific vehicle speed signal to the EPS. Below 6V or above 16V, the speed control CAN-BOX stops sending vehicle speed signals to the EPS. The status of the signal line connecting the speed control CAN-BOX and the EPS: As it replaces the VCU in sending the EPS vehicle speed signal, communication between the CAN-BOX and the EPS must remain normal at all times. The status of the speed control knob: Monitor whether the knob is damaged and whether it is rotated to the correct position (not between two gears). The EPS status bit: The operating status flag bit sent externally by the EPS to ensure that the EPS is operating normally.

[0028] like Figure 3 The diagram shows the CAN-BOX schematic. The IG power supply outputs 12V via a reverse protection diode, which is then converted to 5V by a power supply circuit (DC-CDC step-down module) to power the CPU. The rotary switch is a five-position switch, with different voltage outputs corresponding to different positions. The input of the rotary switch is connected to a +5V power supply, and the negative terminal is grounded. Thus, each rotation of the rotary switch to a specific position outputs a voltage to the CPU's input. The CPU outputs different vehicle speed signals via the CAN module based on the input voltage. The CPU's output is connected to the ECU (Electronic Control Unit) via the CAN module, receiving the signal through CAN communication. An indicator light (LED) is connected to the CPU's output. The LED's illumination indicates whether the speed control CAN-BOX is malfunctioning, providing a warning. The fault signal acquisition includes a voltage acquisition module that collects the 12V power signal from the IG power supply and the output voltage signal from the rotary switch. Based on the acquired voltage, the CPU can determine an undervoltage fault. The voltage signal from the rotary switch indicates whether the switch is faulty or between two positions. The output of this voltage acquisition module is connected to the CPU's input. The CPU's input is also connected to the fault signal output of the EPS control module (ECU) to receive fault signals from the EPS. When the EPS detects a fault, it outputs a fault signal to other modules. This application directly connects to its output, allowing it to acquire the fault signal and issue an indicator light warning. Since the CPU is connected to the CAN module, it can obtain the CAN module's communication and connectivity status through various methods such as a heartbeat mechanism, thereby determining whether the CAN module is faulty and providing a warning.

[0029] This embodiment primarily replaces the vehicle's VCU in sending vehicle speed signals to the EPS. The speed control CAN-BOX is connected to the ECU via a signal harness, and the specific communication method is CAN protocol communication. Figure 1 As shown, the vehicle's IG serves as the power supply harness for the speed control CAN-BOX, connecting to both the speed control CAN-BOX and the EPS-ECU. When the vehicle is started, the speed control CAN-BOX and EPS begin working together simultaneously.

[0030] like Figure 2As shown, after the speed control CAN-BOX starts operating, it immediately confirms the current knob position so that it can quickly send the accurate desired vehicle speed signal to the EPS-ECU via its internal CAN communication circuit module, enabling the EPS to provide steering assistance at the desired level. Subsequently, every 20ms, the speed control CAN-BOX will confirm the speed control knob position again. When it detects a change in the speed control knob position, and confirms the same result 25 times consecutively (500ms), the CAN communication circuit module begins sending a new desired vehicle speed signal.

[0031] To ensure driving safety while the vehicle is in motion, this invention pre-sets countermeasures for possible malfunctions during operation.

[0032] In case of a power supply voltage undervoltage fault, the speed control CAN-BOX checks the power supply voltage (vehicle IG) every 20ms during operation. If the voltage drops below 8V, it's considered an undervoltage fault. The vehicle speed signal is immediately adjusted to 0km / h, the maximum assist provided by the EPS. Simultaneously, a fault LED on the housing illuminates to alert the driver of a steering system malfunction, allowing them to safely maneuver the vehicle for inspection. However, if the power supply voltage drops below 6V, rendering the speed control CAN-BOX completely inoperable, the EPS fault strategy must be relied upon. When the power supply voltage is between 6V and 8V, it's continuously checked every 20ms. If the voltage is consistently above 10V for more than five consecutive times (100ms), the undervoltage fault is considered resolved. The vehicle speed signal is then restored to the desired speed corresponding to the selected speed control knob, and the fault LED turns off, indicating the fault has been resolved.

[0033] A malfunction in the speed control knob, such as accidental detachment or insufficient adjustment leaving it stuck between two gears, will trigger a system check every 20ms during CAN-BOX operation. If any of the five preset speed control knobs remains unclear or incorrect for more than 25 consecutive times (500ms), it is considered a speed control knob malfunction. The vehicle speed signal will be adjusted to 40km / h (the preset minimum power assist) to prevent a sudden decrease in steering wheel light due to a malfunction, which could lead to excessive steering angle and potential danger. A malfunction LED will illuminate to alert the driver of the steering system failure. Once the malfunction is resolved, the vehicle must be restarted. The vehicle speed signal will then be sent back to the desired speed corresponding to the selected speed control knob, and the malfunction LED will turn off, indicating the malfunction has been resolved.

[0034] In case of a CAN communication failure, the CAN-BOX checks the CAN bus status every 100ms during operation. If an abnormality is detected, such as an open or short circuit in the CAN communication harness, or a bus that is off or busy, it is determined to be a CAN communication failure. The fault LED illuminates to alert the driver that the steering system is malfunctioning. At this time, the CAN-BOX can no longer provide a vehicle speed signal to the EPS, relying instead on the EPS's own fault response strategy. If the CAN bus is detected to be back to normal, CAN communication is immediately restored, the vehicle speed signal is sent back to the desired speed corresponding to the selected speed control knob, and the fault LED turns off, indicating that the fault has been resolved.

[0035] In the event of an EPS (Electric Power Steering) malfunction, assuming normal CAN communication, the system receives status signals sent by the EPS. If the received status signal indicates that the EPS is malfunctioning or has a fault, it is determined to be an EPS malfunction, and the fault LED illuminates to alert the driver that the steering system is faulty. The fault LED will turn off once the status signal indicates that the EPS is normal, indicating that the fault has been resolved.

[0036] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. An electric power steering system for a modified vehicle, characterized in that: The system includes a control module (ECU), a torque sensor, and a vehicle speed simulation module. The torque sensor sends the detected steering wheel direction and torque magnitude to the control module (ECU). The output of the vehicle speed simulation module is connected to the control module (ECU) to simulate the vehicle speed signal of the modified vehicle and send it to the control module (ECU). The vehicle speed simulation module outputs a vehicle speed signal to the control module (ECU). The control module (ECU) controls the operation of the electric power steering system's power steering motor to provide power assistance. The vehicle speed simulation module includes a rotary switch, a central processing unit (CPU), and a CAN module. The rotary switch is connected to the CPU, and the CPU outputs different vehicle speed simulation signals to the control module (ECU) through the CAN module based on the voltage signal input from the rotary switch.

2. The electric power steering system for a modified vehicle as described in claim 1, characterized in that: The vehicle's IG power supply module is connected to the input terminal of the power circuit after passing through the anti-reverse diode. The input terminal of the power circuit is connected to the central processing unit (CPU) to supply power to the CPU.

3. The electric power steering system for a modified vehicle as described in any one of claims 1-2, characterized in that: The input terminal of the central processing unit (CPU) is connected to the fault signal acquisition module, and the output terminal of the CPU is connected to the fault indicator light, which is used to drive the illumination state of the fault indicator light according to the fault signal.

4. The electric power steering system for a modified vehicle as described in claim 3, characterized in that: The fault signal acquisition module includes a voltage signal acquisition module, through which the central processing unit (CPU) acquires the voltage signal of the IG power supply module.

5. The electric power steering system for a modified vehicle as described in claim 3, characterized in that: The fault signal acquisition module includes a rotary switch fault monitoring module, whose output is connected to the input of the central processing unit (CPU) and is used to determine whether the rotary switch is faulty based on the acquired rotary switch signal.

6. The electric power steering system for a modified vehicle as described in claim 3, characterized in that: The central processing unit (CPU) monitors the CAN module to determine its operating status.

7. The electric power steering system for a modified vehicle as described in claim 3, characterized in that: The central processing unit (CPU) is connected to the fault signal output terminal of the EPS control module (ECU) to acquire the fault signal of the EPS.

8. A control method for an electric power steering system of a modified vehicle as described in any one of claims 1-7, characterized in that: The control method includes: after the system is installed on the modified vehicle, the control module ECU outputs corresponding power assist based on the collected torque signal and vehicle speed simulation signal.

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