A return control method of an electric power steering system based on return speed control

Abstract

The application discloses a kind of based on the electric power steering system return control method of speed control, by hand off return state judging module, return time determination module, return speed determination module and return compensation torque determination module composition.Hand off return state judging module is judged according to steering wheel torque, steering wheel angle and rotational speed signal, when simultaneously satisfying the following conditions, it is judged as hand off return state.The application is determined by hand off time steering wheel angle and vehicle speed return time determination module by design, more satisfies driver expectation, by the judgment of driver holding return / hand off return and the correction of return speed thereby, so that the return performance under each working condition is more in line with driver expectation.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, and in particular to a return-center control method for an electric power steering system based on return-center speed control. Background Technology

[0002] In recent years, electric power steering (EPS) systems have been widely used in automobiles. For steering, consumers are more concerned about the quality of the steering when the car returns to center.

[0003] Invention patent CN108860294A discloses an active return-to-center control method and system for an electric power steering system. Addressing the issues of inaccurate return-to-center status judgment and hand force fluctuations during active return-to-center control in electric power steering systems with steering wheel angle signals, this invention provides a reliable active return-to-center control method and system that does not rely on return-to-center status judgment and can ensure reasonable steering wheel return. However, this control method cannot control the return-to-center speed during the return-to-center process, and the return-to-center effect is not easily in line with the driver's expectations.

[0004] Invention patent CN108516012A discloses an electric power steering system that achieves active self-centering based on an ideal angular velocity model, which is based on vehicle speed V and steering angle θ. s The ideal return-to-center angular velocity model formed by parameters such as ω makes the actual angular velocity ω of the steering wheel during the return-to-center process... s With ideal positive angular velocity ω s -r enables real-time tracking control of the target, taking into account both the actual turning angle θ. s It also takes into account the actual angular velocity ω s This allows the EPS system to have the ability to actively return to center, bringing the steering wheel back to the center position for left and right turns at an appropriate angular speed. However, this control method requires a large number of parameters to be matched when designing the return speed curve, and it does not take into account the return speed design when the driver holds the steering wheel to return to center, so the return effect is difficult to fully meet the driver's expectations. Summary of the Invention

[0005] In response to the above situation, this invention adopts a different approach from previous electric power steering system return-to-center control methods, proposing a high-quality return-to-center control method for electric power steering systems based on return-to-center speed control.

[0006] After judging based on the current return-to-center status, based on the current vehicle speed V x and steering wheel angle δ swThe desired return-to-center time is determined, and then the return-to-center process is set based on the steering wheel position when the steering wheel is released and the desired return-to-center time. This is the relationship curve between the steering wheel angle and the desired return-to-center speed, which satisfies the bathtub curve relationship. Considering that the driver may hold the steering wheel to return to center during normal driving, the desired return-to-center speed is corrected based on the steering wheel torque and speed to obtain the desired return-to-center speed when the driver holds the steering wheel to return to center / releases it. After determining the desired return-to-center speed, it is integrated to determine the desired steering wheel position. By tracking this position, the return-to-center compensation torque can be calculated, so that the steering wheel returns to the center position at the desired speed.

[0007] The purpose of this invention is to solve the problem that the current electric power steering (EPS) vehicles have difficulty controlling and adjusting the return-to-center speed, and that this control does not easily meet the driver's expectations. To address these issues, this invention proposes a high-quality return-to-center control method for EPS systems based on return-to-center speed control. This method solves the problem that existing strategies cannot directly control and adjust the return-to-center speed, thereby improving the vehicle's return-to-center quality.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A return-to-center control method for an electric power steering system based on return-to-center speed control comprises a release-and-return-to-center state determination module, a return-to-center time determination module, a return-to-center speed determination module, and a return-to-center compensation torque determination module. The specific method includes the following steps:

[0010] Step 1: The steering wheel release and return-to-center state judgment module determines whether the steering wheel is in the release and return-to-center state based on the steering wheel torque, steering wheel angle, and speed.

[0011] Step 2: The return-to-center time determination module determines the desired return-to-center time based on the steering wheel position when the steering wheel is released.

[0012] Step 3: The return-to-center speed determination module sets the return-to-center process based on the steering wheel position when the steering wheel is released and the desired return-to-center time;

[0013] Step 4: After determining the desired return speed, the return compensation torque determination module integrates the desired steering wheel position and calculates the return compensation torque to track this position, so that the steering wheel returns to the center position at the desired speed.

[0014] As a further technical solution of the present invention: In step 1, when the following conditions are met simultaneously, it is determined to be a state of letting go and returning to center: (1) the steering wheel angle and speed are opposite, that is, the steering wheel is in a state of returning to center; (2) the steering wheel torque is less than a certain threshold value, that is, the driver lets go and releases the steering wheel; (3) the steering wheel angle is greater than a certain threshold value, that is, the vehicle is not in the center area.

[0015] As a further technical solution of the present invention: In step 1, when any of the following conditions are met, it is determined to be a driver-active steering state: (1) the steering wheel angle and speed are both less than a certain threshold value, that is, the steering wheel returns to the center area; (2) the steering wheel torque is greater than a certain threshold value, that is, the driver actively turns the steering wheel.

[0016] As a further technical solution of the present invention: the active steering state includes active outward steering and active inward steering.

[0017] As a further technical solution of the present invention: In step 2, at the same vehicle speed, the return time increases as the turning angle increases; at the same turning angle, the return time decreases as the vehicle speed increases; when the vehicle speed is zero, the return time is infinite, that is, it does not return to center.

[0018] As a further technical solution of the present invention: the steering wheel position when releasing the steering wheel and the expected return time satisfy the bathtub curve relationship, as shown in equation (1):

[0019]

[0020] In the formula: It is the expected return speed when the driver completely lets go; It refers to the position of the steering wheel when you let go; t tar It is the expected time to return to positive. It is the maximum speed during the return-to-center process, and its value is

[0021] At the same time, the desired return speed is corrected according to the steering wheel torque and speed, as shown in equation (2):

[0022]

[0023] In the formula: It is the final expected rate of return to positive; T sw_low T sw_h igh This is the steering wheel torque threshold value. When the steering wheel torque is less than T... sw_low It is assumed that the driver has completely let go of the steering wheel when the steering wheel torque is greater than T. sw_h igh One side assumes the driver is actively steering, while the other side assumes the driver is holding the steering wheel.

[0024] As a further technical solution of the present invention: In step 4, after the driver releases the steering wheel or holds the steering wheel, the steering wheel is controlled to return to the center position at an appropriate speed. It only works when the driver releases the steering wheel or holds the steering wheel. It does not work when the driver actively turns or actively returns to center. At this time, the compensation torque is zero.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention solves the problem that the existing electric power steering system's return-to-center control strategy cannot directly control and adjust the return-to-center speed, thereby improving the vehicle's return-to-center quality.

[0027] 2. This invention designs a return-to-center time determination module, which determines the return-to-center time based on the steering wheel angle and vehicle speed at the moment of releasing the steering wheel, thus better meeting the driver's expectations. By judging whether the driver is holding the steering wheel while returning to center or releasing it while returning to center, and thus correcting the return-to-center speed accordingly, the return-to-center performance under various working conditions is more in line with the driver's expectations. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the return-center control implementation scheme of the electric power steering system based on return-center speed control as described in this invention.

[0029] Figure 2 This is the alignment time characteristic curve described in this invention.

[0030] Figure 3 This is the self-alignment speed characteristic curve described in this invention.

[0031] Figure 4 This is a diagram of the calculation architecture for the aligning compensation torque described in this invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Reference Figure 1-4 A return-to-center control method for an electric power steering system based on return-to-center speed control is disclosed, comprising a release-to-center state judgment module, a return-to-center time determination module, a return-to-center speed determination module, and a return-to-center compensation torque determination module. The release-to-center state judgment module judges the state based on steering wheel torque, steering wheel angle, and speed signals. When the following conditions are simultaneously met, the system is judged to be in a release-to-center state. The return-to-center time determination module determines the desired return-to-center time based on the steering wheel angle at that moment. The return-to-center speed determination module sets the return-to-center process based on the steering wheel position at the time of release and the desired return-to-center time. The return-to-center compensation torque determination module, after determining the desired return-to-center speed, integrates it to determine the desired steering wheel position. The return-to-center compensation torque is calculated by tracking this position, allowing the steering wheel to return to the center position at the desired speed. The symbol parameters used in this invention are explained in Table 1 below.

[0034] Table 1: Symbol Parameter Description Table

[0035]

[0036]

[0037] Step 1: Determine whether the steering wheel is in the "release and return to center" state based on the steering wheel torque, steering wheel angle, and speed. If yes, proceed to the following steps; otherwise, skip the following steps, and the return-to-center compensation torque will be zero.

[0038] Step 2: Determine the desired return-to-center time based on the position of the steering wheel when releasing the steering wheel;

[0039] Step 3: Set the return-to-center process based on the steering wheel position when the driver releases the steering wheel and the expected return-to-center time, i.e., the relationship curve between the steering wheel angle and the expected return-to-center speed; based on the real-time steering wheel angle, find the set curve to obtain the expected return-to-center speed when the driver completely releases the steering wheel; correct the expected return-to-center speed based on the steering wheel torque and speed to obtain the expected return-to-center speed when the driver holds the steering wheel to return to center / releases the steering wheel.

[0040] Step 4: After determining the desired return speed, integrate it to determine the desired steering wheel position. By tracking this position, the return compensation torque can be calculated, so that the steering wheel returns to the center position at the desired speed.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0042] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment have been appropriately combined to form other embodiments that are easy for those skilled in the art to understand.

Claims

1. A method for return-to-center control of an electric power steering system based on return-to-center speed control, characterized in that, It consists of a release-and-return state determination module, a return-to-center time determination module, a return-to-center speed determination module, and a return-to-center compensation torque determination module. The specific method includes the following steps: Step 1: The steering wheel release and return-to-center state judgment module determines whether the steering wheel is in the release and return-to-center state based on the steering wheel torque, steering wheel angle, and speed. Step 2: The return-to-center time determination module determines the desired return-to-center time based on the steering wheel position when the steering wheel is released. Step 3: The return-to-center speed determination module sets the return-to-center process based on the steering wheel position when the steering wheel is released and the desired return-to-center time; Step 4: After determining the desired return speed, the return compensation torque determination module integrates the return speed to determine the desired steering wheel position. The return compensation torque is calculated with the goal of tracking this position, so that the steering wheel returns to the center position at the desired speed. The steering wheel position at the moment of release and the expected return time satisfy the bathtub curve relationship, as shown in equation (1): （1） In the formula: It is the expected return speed when the driver completely lets go; This refers to the position of the steering wheel when you let go of the steering wheel; It is the expected time to return to positive. It is the maximum speed during the return-to-center process, and its value is ; It refers to the steering wheel angle; At the same time, the desired return speed is corrected according to the steering wheel torque and rotation speed, as shown in equation (2): （2） In the formula: It is the final expected rate of return to positive territory; , It is the steering wheel torque threshold value. It is the steering wheel angular velocity, when the steering wheel torque is less than... It is assumed that the driver has completely let go of the steering wheel when the steering wheel torque is greater than 100%. One side assumes the driver is actively steering, while the other side assumes the driver is holding the steering wheel.

2. The method for return-to-center control of an electric power steering system based on return-to-center speed control according to claim 1, characterized in that, In step 1, the vehicle is judged to be in the "release and return to center" state when the following conditions are met simultaneously: (1) The steering wheel angle and speed are opposite, that is, the steering wheel is in the "return to center" state; (2) The steering wheel torque is less than a certain threshold value, that is, the driver releases the steering wheel; (3) The steering wheel angle is greater than a certain threshold value, that is, the vehicle is not in the center area.

3. The method for return-to-center control of an electric power steering system based on return-to-center speed control according to claim 2, characterized in that, In step 1, the driver is judged to be in an active steering state when any of the following conditions are met: (1) The steering wheel angle and speed are both less than a certain threshold value, that is, the steering wheel returns to the center area; (2) The steering wheel torque is greater than a certain threshold value, that is, the driver actively turns the steering wheel.

4. The method for return-to-center control of an electric power steering system based on return-to-center speed control according to claim 3, characterized in that, The active steering states include active outward steering and active inward steering.

5. The method for return-to-center control of an electric power steering system based on return-to-center speed control according to claim 1, characterized in that, In step 2, at the same vehicle speed, the return time increases as the turning angle increases; at the same turning angle, the return time decreases as the vehicle speed increases; when the vehicle speed is zero, the return time is infinite, that is, it does not return to center.

6. The method for return-to-center control of an electric power steering system based on return-to-center speed control according to claim 1, characterized in that, In step 4, after the driver releases the steering wheel or holds the steering wheel, the steering wheel is controlled to return to the center position at an appropriate speed. This only works when the driver releases the steering wheel or holds the steering wheel. It does not work when the driver actively turns or actively returns to center, at which time the compensation torque is zero.

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