Steering gear, control method and device for a steering gear

Abstract

The application provides a kind of steering gear, the control method and device of steering gear.The steering gear includes motor and torque output end, the driving current input to any time motor is not greater than the upper limit of driving current at this time, torque output end is used to output the power-assisted torque that the size of driving current is positively correlated to drive the steering of the wheel of vehicle, the method includes: in the case where the rotation angle of the steering wheel of vehicle is not less than the limiting angle and the steering wheel rotates towards the direction of increasing rotation angle, determine the hand torque for driving the rotation of the steering wheel;If the hand torque at any time is greater than hand torque threshold, then set the limiting reference current value as the upper limit of driving current;If the hand torque at any time is not greater than hand torque threshold, then reduce the upper limit of driving current, and the upper limit of driving current after reduction is less than the limiting reference current value.The method can limit the rotation angle of the steering wheel within the allowable range of rotation angle soft limiting function, and effectively avoid various security risks.

Description

Technical Field

[0001] This invention relates to the field of vehicles, and more particularly to a steering gear, a steering gear control method, and a device. Background Technology

[0002] Modern vehicles typically have a steering system, which the driver controls by turning the steering wheel. To allow the driver to easily steer with minimal effort, modern vehicles usually employ a steering assist mechanism to power the steering wheel.

[0003] Current steering systems typically limit wheel steering angle to 360°. To protect the steering system and reduce vehicle safety hazards (excessive wheel steering angle leads to excessive interference between the steering and suspension systems, causing wheel shimmy, excessive tire wear, interference during braking, and deterioration of steady-state steering characteristics), current steering gears usually have a soft-limit function: when the steering wheel angle does not exceed the limit angle, the upper limit of the steering gear's drive current is set to a reference current (e.g., 10A); when the angle exceeds the limit angle and continues to turn, a smaller soft-limit current threshold (e.g., 3A) is forcibly set as the upper limit of the drive current, thereby limiting the steering gear's output of a smaller assist torque.

[0004] However, after the aforementioned soft steering angle limit function is activated: if the driver turns the steering wheel beyond the limit angle while the vehicle is moving, the soft steering angle limit function may fail, leading to tire-steering tie rod interference, increased vehicle roll, damage to steering mechanical components, and even causing the driver to lose confidence in steering control, posing a significant safety hazard. If the driver turns the steering wheel beyond the limit angle when the vehicle is stationary (i.e., not moving), although the soft steering angle limit function is effective, the sudden reduction in the upper limit of the drive current may cause the deformation and rebound force of mechanical components such as the steering system and suspension to exceed the power assist torque, resulting in a sudden increase in steering wheel force or even a rebound that causes the steering wheel to buckle, also posing a safety hazard. Summary of the Invention

[0005] In view of this, the present invention provides a steering gear, a steering gear control method and device to overcome the shortcomings of related technologies.

[0006] Specifically, the present invention is achieved through the following technical solution:

[0007] According to a first aspect of the present invention, a control method for a steering gear is provided, the steering gear including a motor and a torque output terminal, wherein the drive current input to the motor at any given time is not greater than the upper limit of the drive current at that time, and the torque output terminal is used to output an assist torque positively correlated with the magnitude of the drive current to drive the wheels of a vehicle to steer, the method comprising:

[0008] When the steering wheel of the vehicle rotates at an angle not less than a limit angle and the steering wheel is rotated in a direction that increases the rotation angle, the hand torque for driving the steering wheel to rotate is determined.

[0009] If the hand torque at any moment is greater than the hand torque threshold, then the limit reference current value is set to the upper limit of the drive current;

[0010] If the hand torque at any given time is not greater than the hand torque threshold, then the upper limit of the driving current is reduced, and the reduced upper limit of the driving current is less than the limit reference current value.

[0011] Optionally, determining the hand torque required to drive the steering wheel to rotate includes:

[0012] The hand torque is determined multiple times at fixed intervals; or,

[0013] The hand torque is determined multiple times at intervals that are negatively correlated with the rotational speed of the steering wheel.

[0014] Optionally, determining the hand torque required to drive the steering wheel to rotate includes:

[0015] In the case where the steering gear also includes a torque input terminal connected to the steering wheel, the hand torque detected and transmitted by a first sensor to the torque input terminal is received; or,

[0016] The hand torque is received by a second sensor that detects and transmits the torque for the steering wheel or its connected rotating device.

[0017] Optionally, determining the hand torque threshold includes:

[0018] Determine the preset hand torque threshold; or,

[0019] The hand torque value corresponding to the current driver's identity information is determined as the hand torque threshold.

[0020] Optionally, determining the limit reference current value includes:

[0021] Determine the preset limit reference current value; or,

[0022] The current value corresponding to the current state of the vehicle is determined as the limit reference current value, wherein the current value corresponding to the stationary state is greater than the current value corresponding to the driving state.

[0023] Optionally, reducing the upper limit of the drive current includes:

[0024] The upper limit of the drive current is reduced according to the preset first step length; or,

[0025] The upper limit of the drive current is reduced according to the second step size corresponding to the current state of the vehicle, wherein the second step size corresponding to the stationary state is smaller than the second step size corresponding to the driving state.

[0026] Optionally, in two consecutive reductions of the upper limit of the drive current, the reduction magnitude of the previous reduction is not equal to the reduction magnitude of the subsequent reduction.

[0027] Optionally, the motor is a DC motor, and reducing the upper limit of the drive current includes:

[0028] If the hand torque is still not greater than the hand torque threshold when the upper limit of the drive current is reduced to zero, the current direction corresponding to the upper limit of the drive current is reversed to control the DC motor to reverse.

[0029] Optional, also includes:

[0030] When the steering wheel rotation angle is less than the limit angle, the preset non-limit reference current value is set as the upper limit of the drive current; or,

[0031] When the rotation angle of the steering wheel is not less than the limit angle and the steering wheel is rotated in a direction that reduces the rotation angle, the limit reference current value is set to the upper limit of the drive current.

[0032] Optional, also includes:

[0033] The driving current at any given moment is determined based on the hand torque, and the magnitude of the driving current is positively correlated with the magnitude of the hand torque; and / or,

[0034] The driving current at any given moment is determined based on the vehicle speed, and the magnitude of the driving current is negatively correlated with the vehicle speed.

[0035] According to a second aspect of the present invention, a control device for a steering gear is provided, the steering gear including a motor and a torque output terminal, wherein the drive current input to the motor at any given time is not greater than the upper limit of the drive current at that time, and the torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the wheels of a vehicle to steer, the device comprising:

[0036] A hand torque determining unit is used to determine the hand torque for driving the steering wheel to rotate when the rotation angle of the steering wheel of the vehicle is not less than the limit angle and the steering wheel is rotated in the direction that increases the rotation angle.

[0037] The first setting unit is configured to set the limit reference current value to the upper limit of the driving current if the hand torque at any time is greater than the hand torque threshold.

[0038] The upper limit reduction unit is used to reduce the upper limit of the driving current if the hand torque at any time is not greater than the hand torque threshold, and the reduced upper limit of the driving current is less than the limit reference current value.

[0039] According to a third aspect of the present invention, a steering gear is provided, the steering gear including a motor controller, a motor, and a torque output terminal, wherein the drive current input to the motor at any given time is not greater than the upper limit of the drive current at that time, the torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the wheels of the vehicle to steer, and the motor controller is used to:

[0040] When the steering wheel of the vehicle rotates at an angle not less than a limit angle and the steering wheel is rotated in a direction that increases the rotation angle, the hand torque for driving the steering wheel to rotate is determined.

[0041] If the hand torque at any moment is greater than the hand torque threshold, then the limit reference current value is set to the upper limit of the drive current;

[0042] If the hand torque at any given time is not greater than the hand torque threshold, then the upper limit of the driving current is reduced, and the reduced upper limit of the driving current is less than the limit reference current value.

[0043] According to a fourth aspect of the invention, a vehicle is provided which is equipped with a steering system as described in the third aspect above.

[0044] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0045] This solution abandons the open-loop control scheme in related technologies that, under the condition that "the steering wheel rotation angle is not less than the limit angle and the steering wheel is rotating in the direction that increases the rotation angle" (hereinafter referred to as the soft limit start condition), fixes the upper limit of the drive current below the soft limit current threshold. Instead, it introduces the concept of "hand torque threshold" and corresponding control logic into the corner soft limit function to achieve closed-loop control of the upper limit of the drive current, thereby effectively limiting the steering wheel rotation angle within the allowable range of the corner soft limit function. Specifically, when the soft limit start condition is met, the hand torque is determined and the upper limit of the drive current is adjusted accordingly: if the hand torque at any moment is greater than the hand torque threshold, the limit reference current value is set to the upper limit of the drive current (i.e., the upper limit of the drive current is adjusted to the limit reference current value); if the hand torque at any moment is not greater than the hand torque threshold, the upper limit of the drive current is reduced, and the reduced upper limit of the drive current is less than the limit reference current value (i.e., the upper limit of the drive current is adjusted to be less than the limit reference current value).

[0046] It is understandable that, since the drive current input to the motor at any given time is not greater than the upper limit of the drive current at that time, and the torque output terminal is used to output the assist torque that is positively correlated with the magnitude of the drive current, after adjusting the upper limit of the drive current using the aforementioned control logic when the soft limit start condition is met, the assist torque output by the steering gear is also adjusted accordingly.

[0047] If the driver turns the steering wheel while the vehicle is stationary (i.e., the vehicle is stationary when the aforementioned soft-limit activation conditions are met), the large sliding friction between the tires and the ground (resistance torque is high) results in a large hand torque on the steering wheel. This hand torque exceeds the hand torque threshold, activating the angle soft-limit function. The upper limit of the drive current is adjusted to a larger limit reference current value, causing the steering gear to output a larger assist torque (i.e., the limiting effect is weaker), thus gradually reducing the hand torque output by the user. This process avoids rebound due to the deformation and springback force of mechanical components exceeding the assist torque, improving safety; it also allows the hand torque to gradually decrease until rotation stops, effectively limiting the steering wheel's rotation angle within the allowable range of the angle soft-limit function.

[0048] If the driver turns the steering wheel while the vehicle is in motion (i.e., the vehicle is in motion when the aforementioned soft limit activation conditions are met), the steering wheel experiences a smaller hand torque because there is less rolling friction between the tires and the ground (resistance torque is lower at this time). As a result, the hand torque does not exceed the hand torque threshold, ensuring that the corner soft limit function remains effective. The upper limit of the drive current will be adjusted to be less than the limit reference current value, resulting in a smaller power assist torque output by the steering gear (i.e., a stronger limit at this time). This effectively avoids various safety hazards caused by the failure of the corner soft limit function during vehicle operation.

[0049] In summary, this solution ensures the effectiveness of the steering angle soft limit function whether the vehicle is stationary or in motion. It not only limits the steering wheel rotation angle within the allowable range of the steering angle soft limit function, but also effectively avoids various safety hazards, demonstrating significant improvement. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0051] Figure 1 This is a flowchart illustrating a steering gear control method according to an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of the structure of a vehicle steering system according to an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram of the structure of a steering gear according to an embodiment of the present invention;

[0054] Figure 4 This is a schematic diagram illustrating the force analysis of a steering wheel according to an embodiment of the present invention;

[0055] Figure 5 This is a schematic diagram illustrating the adjustment process of the upper limit of the drive current according to an embodiment of the present invention;

[0056] Figure 6 This is a schematic diagram of another steering gear structure shown in an embodiment of the present invention;

[0057] Figure 7 This is a block diagram of a steering gear control device shown in an embodiment of the present invention. Detailed Implementation

[0058] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present invention.

[0059] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0060] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0061] The embodiments of the steering system control method of the present invention will now be described in detail with reference to the accompanying drawings.

[0062] Current steering systems have a soft-limit function for steering angle. Specifically, when the steering wheel angle does not exceed the limit angle, the upper limit of the steering system's drive current is set to a reference current (e.g., 10A); when the steering angle exceeds the limit angle and continues to turn, a smaller soft-limit current threshold (e.g., 3A) is forcibly set as the upper limit of the drive current, thereby limiting the steering system to output a smaller assist torque.

[0063] The inventors discovered that the control logic of the aforementioned corner soft limit function has some defects, which leads to safety hazards and is prone to causing safety accidents:

[0064] If the soft steering angle limit function is activated while the vehicle is in motion, on the one hand, there is a small rolling friction between the tires and the ground, meaning the steering resistance torque is small; on the other hand, the drive current is less than the limit current threshold, which leads to a decrease in the power assist torque and a relative increase in the hand torque. These factors result in the power assist torque still being greater than the steering resistance torque, allowing the driver to continue turning the steering wheel, thus increasing the steering angle (exceeding the limit angle), meaning the soft steering angle limit function is ineffective. This failure may lead to tire-steering tie rod interference, increased vehicle roll, damage to steering mechanical components, and even further, a loss of driver confidence in steering control, posing a significant safety hazard.

[0065] If the steering wheel cornering soft limit function is activated when the vehicle is not moving (i.e., turning the steering wheel while the vehicle is stationary), there is significant sliding friction between the tires and the ground, resulting in a large steering resistance torque. Furthermore, the drive current is lower than the limit current threshold, leading to a decrease in power assist torque and a relative increase in manual steering effort. These factors cause the power assist torque to remain less than the steering resistance torque, preventing the driver from continuing to turn the steering wheel; thus, the steering wheel cornering soft limit function is effective. However, suddenly lowering the upper limit of the drive current will cause a sudden decrease in the drive current, resulting in the deformation and rebound force of the steering system and suspension components exceeding the power assist torque. This causes a sudden increase in steering wheel effort, potentially leading to a rebound and even a steering wheel jerk, posing a safety hazard.

[0066] The reason for this is that the aforementioned control logic is an open-loop control that fixes the upper limit of the drive current below the soft-limit current threshold, resulting in poor performance. When the vehicle is moving (i.e., in motion), turning the steering wheel beyond the limit angle weakens the soft-limit strength of the steering gear, making the increase in steering wheel weight less noticeable. This makes it easy for the driver to exceed the soft-limit angle when turning the steering wheel, causing the soft-limit function to fail. Conversely, when the vehicle is stationary (i.e., stopped in place), turning the steering wheel beyond the limit angle weakens the soft-limit strength of the steering gear. Although the steering wheel weight increases significantly at this time, the drive current of the steering gear decreases drastically, easily causing the steering system to generate a momentary rebound force, resulting in the steering wheel rebounding and hitting the driver.

[0067] To address the aforementioned deficiencies and their causes, this solution proposes a steering gear control method. By introducing the concept of a "hand torque threshold" and corresponding control logic into the steering angle soft-limit function, closed-loop control of the upper limit of the drive current is achieved. This limits the steering wheel rotation angle within the allowable range of the steering angle soft-limit function, effectively avoiding the aforementioned safety hazards and improving the driving safety of vehicles equipped with steering gears. The method is described in detail below with reference to the accompanying drawings.

[0068] Figure 1This is a flowchart illustrating a control method for a steering gear according to an embodiment of the present invention. The steering gear of the present invention includes a motor and a torque output terminal. At any given time, the drive current input to the motor does not exceed the upper limit of the drive current at that time. The torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the vehicle wheels to steer. This method can be applied to the motor controller of the steering gear, specifically including the following steps 102-104b.

[0069] Step 102: When the steering wheel of the vehicle rotates at an angle not less than the limit angle and the steering wheel is rotated in the direction that increases the rotation angle, determine the hand torque that drives the steering wheel to rotate.

[0070] The steering gear described in this invention is installed on a vehicle and participates in the vehicle's steering system (i.e., is part of the steering system). It assists the driver in adjusting the direction of the wheels and reduces the force required to turn the steering wheel. The vehicle may have at least one wheel, but embodiments of this invention do not limit the wheel to which the steering gear provides assistance. For example, if the vehicle has four tires, the steering gear can be used to assist the steering of two of the front wheels, or it can be used to assist the steering of two of the rear wheels, which will not be elaborated further.

[0071] The steering gear described is an electric steering gear, meaning it is driven by electricity. This steering gear includes a motor and a torque output terminal. The motor rotates under the drive current, driving the torque output terminal to rotate and output a power assist torque to the outside, thereby providing steering assistance to the wheels. The torque generated by the motor is positively correlated with the magnitude of the drive current (i.e., the larger the drive current, the larger the torque). Therefore, the power assist torque output by the torque output terminal is also positively correlated with the magnitude of the drive current.

[0072] In addition, the steering gear has an adjustable parameter for the upper limit of the drive current, which controls the magnitude and direction of the drive current input to the motor. Specifically, the drive current input to the motor at any given time will not exceed the upper limit of the drive current at that time. This method controls the drive current by adjusting the magnitude of the upper limit of the drive current, thereby controlling the strength of the steering gear.

[0073] For example, the vehicle's steering system can be seen in... Figure 2As shown in the figure, the steering system includes a steering wheel 1, a steering column 2, a steering gear 3 (with a steering rocker arm), a steering tie rod 4, a steering knuckle arm 5, a left trapezoidal arm 6, a tie rod 7, and a right trapezoidal arm 8 (the wheels are not shown). Adjacent structures are mechanically connected to each other, thus collectively forming the steering system. Taking the steering gear 3 as a typical example of an electric recirculating ball power steering system, its internal structure can be found in [reference needed]. Figure 3 As shown in the figure, the steering gear 3 includes a steering input shaft (i.e., the torque input end) 301, a TAS (Torque Angle Sensor) sensor 302, a worm gear mechanism 303, a ball screw mechanism 304, a steering rocker arm 305, a motor controller 306, and a motor 307.

[0074] The vehicle described in this invention, in terms of its functional form, can be a pickup truck, sedan, SUV (Sport Utility Vehicle), campervan, or truck, etc.; in terms of its power form, it can be a gasoline-powered vehicle or a new energy vehicle (such as a hybrid vehicle, pure electric vehicle, hydrogen fuel cell vehicle, methanol fuel cell vehicle, etc.), and this invention does not limit its specific form. However, it should be noted that the vehicle should at least have a steering wheel, a steering system, and wheels, so that the steering gear installed on it can provide power steering for the wheels.

[0075] As previously stated, the steering gear control method described in this specification can be applied to the steering gear's motor controller, meaning the controller serves as the execution entity of the method. Specifically, the motor controller can be mounted on the steering gear itself, meaning the control logic of this solution is implemented by the motor controller mounted on the steering gear. Figure 3 The motor controller 306 shown can be used to implement the control logic of this solution. Alternatively, given that the steering gear is mounted on a vehicle and the level of intelligence in vehicles currently being produced is increasing, the motor controller can also be a controller installed on the vehicle, that is, a controller installed on the vehicle (mounted outside the steering gear) to implement the control logic of this solution. For example, in terms of form, the controller can be an on-board ECU (Electronic Control Unit), MCU (Microcontroller Unit), or VCU (Vehicle Control Unit), etc.; in terms of function, the controller can be the vehicle's own steering controller or chassis controller, etc., which will not be elaborated further.

[0076] The aforementioned steering system has a corresponding steering link, and each force-bearing point in the link will perform a corresponding movement. For ease of understanding of the embodiments described below, ... Figure 2Taking any force point P on the steering link of the steering gear 3 from the torque output end to the wheel as an example, the force analysis of several forces involved in the movement of this point is performed. As part of the steering system, the steering wheel is mechanically connected to other structures. The rotation of the steering wheel will cause the various structures in the steering system to move separately (such as the rotation of the steering column 2, the translation of the steering tie rod 4, and the torsion of the tires).

[0077] The force exerted by the driver's hands on the steering wheel along the tangential direction is called hand force (i.e., steering wheel force). Figure 4 The F shown 手 The torque exerted by the steering wheel on the steering wheel is called hand torque. It should be noted that... Figure 4 The F shown 手 This is for illustrative purposes only and does not imply that point P is actually subjected to the force F. 手 In fact, the force applied directly to the steering wheel along the tangent of its circular shape drives its rotation. This hand force causes the steering gear to output a power assist torque through its torque output terminal. This power assist torque acts at the point of application P, such as F. 助 As shown. With F 助 In the opposite direction, the point of force P is also subject to resistance F. 阻 This resistance can include the frictional forces of the steering system (sliding or rolling friction at various structural contact points, sliding or rolling friction between the wheel surface and the ground, etc.), the rotational resistance exerted on the vehicle by obstacles in the direction of rotation, etc., which will not be elaborated further. Among them, F 助 With F 手 In the same direction and its magnitude is the same as F 手 The magnitudes of are positively correlated, while F 助 With F 阻 The directions are opposite. According to the laws of physics: F 助 With F 阻 The difference is used to drive the wheels to steer (i.e., to provide steering power, similar to F). 助 -F 阻 =m 轮 *a 轮 Therefore, if F 助 ≤F 阻 If the wheel does not turn, the wheel will not rotate; in F 助 >F 阻 The wheels will only turn when the time is right.

[0078] After the vehicle is started (e.g., the vehicle's infotainment system is powered on), the sensors can detect rotation information such as the steering wheel's rotation direction and angle, and provide this information to the aforementioned motor controller. Based on this, the motor controller can determine whether the steering wheel's rotation angle is less than a limit angle, and whether the steering wheel is rotating in the direction that increases the rotation angle (i.e., whether the steering wheel's rotation direction is the direction that increases the rotation angle, or whether the rotation angle continues to increase), in order to determine whether the aforementioned soft limit start condition (i.e., the condition that "the steering wheel's rotation angle is not less than the limit angle and the steering wheel is rotating in the direction that increases the rotation angle") is met.

[0079] For example, let's assume that when the steering wheel is not turned, the wheels face directly forward and there is no deflection; in this case, the rotation angle is zero. If the steering wheel is turned counterclockwise to the left, the rotation angle is negative; conversely, if the steering wheel is turned clockwise to the right, the rotation angle is positive. The steering wheel's limiting angle range is [-a, +b], where a is the limiting angle for counterclockwise rotation and b is the limiting angle for clockwise rotation. a and b can be the same, such as a = b = 150°; or a and b can be different, such as a = 120° and b = 150°, etc.

[0080] Of course, given that the steering gear described in this solution has a soft angle limit function, the motor controller can perform the aforementioned judgment when this function is enabled. This function can be enabled by default when the vehicle leaves the factory, or it can be set by the user through the vehicle's infotainment system, etc., which will not be elaborated further. In addition, the sensor can detect and provide the aforementioned rotation information in real time, or it can detect and provide the aforementioned rotation information periodically. After receiving the rotation information at each moment, the motor controller can start performing the aforementioned judgment.

[0081] If the aforementioned soft-limit start condition is met, the hand torque driving the steering wheel can be further determined, i.e., the magnitude (e.g., how many N·m) and direction (e.g., clockwise or counterclockwise) of the torque can be determined. It is understood that if the aforementioned soft-limit start condition is met, it indicates that the steering wheel is currently turning in a direction that increases the rotation angle. For example, if the steering wheel is turning counterclockwise and a = 150°, the current rotation angle is 160° and it is still turning counterclockwise.

[0082] In one embodiment, the motor controller can determine the hand torque required to rotate the steering wheel in various ways. For example, if the steering gear also includes a torque input terminal connected to the steering wheel, the motor controller can receive the hand torque detected and transmitted by a first sensor at the torque input terminal. Since the detected hand torque is used for comparison with a hand torque threshold set for the steering gear, detecting the hand torque at the torque input terminal mounted on the steering gear itself helps improve the accuracy of subsequent comparisons and avoids the adverse effects of the mechanical connection between the steering wheel and the steering gear on the accuracy of hand torque detection. The first sensor can be part of the steering gear (i.e., mounted inside the steering gear, as part of the steering gear), such as... Figure 3 The TAS sensor 302 shown is part of the steering gear 3. This method enables a more streamlined detection system, which helps to miniaturize the steering gear. Alternatively, the first sensor may not be part of the steering gear (e.g., it may be mounted externally to the steering gear and operate independently of it), and this invention does not limit this.

[0083] For example, the hand torque can also be detected by a second sensor on the steering wheel or its connected rotating components and sent to the motor controller; correspondingly, the motor controller only needs to receive the hand torque detected and sent by the second sensor. This method allows steering systems whose own torque is difficult or inconvenient to detect to also apply the control scheme of this invention, thus helping to expand the applicability of this solution.

[0084] Furthermore, either the first sensor or the second sensor mentioned above can be any suitable type of sensor. For example, strain gauge, magnetoelectric, fiber optic, photoelectric, and other types can be selected, and the present invention does not limit this.

[0085] In one embodiment, the motor controller can determine the hand torque in various ways. For example, the hand torque can be acquired multiple times at fixed intervals, i.e., periodically acquired at fixed step sizes. It is understood that the shorter the interval, the more frequently the hand torque is acquired, resulting in a higher frequency of subsequent judgments and adjustments, and better real-time adjustment of the drive current upper limit. However, the computational load of the corresponding processing is also greater. Therefore, the aforementioned interval can be reasonably set according to the actual situation. For example, the hand torque detected by the sensor can be acquired every 5ms or 10ms.

[0086] For example, the motor controller can also determine the steering wheel speed in real time and acquire the hand torque multiple times at intervals negatively correlated with that speed. In other words, during the rotation process after the aforementioned soft-limit start condition is met, the faster the steering wheel rotates, the higher the frequency at which the motor controller acquires the hand torque; conversely, the slower the steering wheel rotates, the lower the frequency at which the motor controller acquires the hand torque. In this way, the frequency of acquiring the hand torque can be adjusted specifically according to the steering wheel rotation speed (this frequency should not be higher than the sampling frequency of the aforementioned sensor detection) to ensure that the adjustment process for the upper limit of the drive current has good real-time performance regardless of whether the steering wheel rotates fast or slow.

[0087] Since the acquired hand torque needs to be compared with a hand torque threshold, the motor controller can predetermine the steering mechanism or temporarily determine the hand torque threshold after acquiring the hand torque. In one embodiment, a preset hand torque threshold can be directly determined, such as setting the hand torque threshold to 10 N·m in advance. The motor controller can then directly determine 10 N·m as the hand torque threshold, a method that is simple and efficient. Of course, to maximize the effectiveness of the aforementioned hand torque threshold, the preset hand torque threshold can be obtained through surveys, experiments, or statistical analysis of historical hand torque information from existing drivers turning the steering wheel.

[0088] In another embodiment, the corresponding hand torque threshold can also be determined based on the driver's identity. For example, the hand torque value corresponding to the current driver's identity information can be determined as the hand torque threshold. For instance, the vehicle manufacturer, maintenance personnel, or user can pre-set different second hand torque values ​​for men and women (e.g., the second hand torque value for men is greater than that for women), and save them in the steering gear's local storage space (or in the vehicle's storage space other than the steering gear). After the current driver sits in the driver's seat, the vehicle can identify the driver's gender (i.e., identity information) through the intelligent cockpit system, and then, when determining the hand torque threshold subsequently, the aforementioned saved hand torque value corresponding to that gender can be directly determined as the hand torque threshold. Furthermore, the aforementioned hand torque threshold can also be set specifically for each driver, which will not be elaborated further. In this way, the hand torque threshold used when actually adjusting the upper limit of the drive current can be strongly correlated with the current driver's identity, thereby helping to improve the current driver's driving experience.

[0089] It should be noted that, due to the existence of the aforementioned soft limit start condition, the hand torque obtained and the determined hand torque threshold obtained by the aforementioned method can only include the magnitude of the torque, without considering its direction. After obtaining the hand torque at any given time and determining the hand torque threshold through the aforementioned method, the hand torques can be compared: if the hand torque at any given time is greater than the hand torque threshold, then proceed to step 104a; otherwise, if the hand torque at any given time is not greater than (i.e., less than or equal to) the hand torque threshold, then proceed to step 104b.

[0090] Step 104a: If the hand torque at any moment is greater than the hand torque threshold, then the limit reference current value is set to the upper limit of the drive current.

[0091] If the hand torque at any given moment exceeds the hand torque threshold, it indicates that the driver is applying excessive force, and a larger drive current should be allowed to be input to the steering gear. Therefore, the limit reference current value can be set as the upper limit of the drive current. As mentioned earlier, the upper limit of the drive current in this invention is an adjustable variable. Therefore, setting the limit reference current value as the upper limit of the drive current means setting the current value of this variable as the limit reference current value to reduce the soft limit strength at this time. Of course, if the current value is the limit reference current value, no update is needed; conversely, if the current value is not equal to the limit reference current value, the current value needs to be updated to the limit reference current value.

[0092] Before setting the upper limit of the drive current, the limit reference current value needs to be determined. In one embodiment, the motor controller can directly determine a preset limit reference current value. For example, the limit reference current value can be preset to 2A, so the motor controller can directly determine 2A as the limit reference current value. This method is simple and efficient. Of course, to ensure that the steering gear can work properly, the current can be preset according to parameters such as the type, brand, and model of the steering gear, such as setting it to the rated current value recorded on the steering gear's nameplate.

[0093] In another embodiment, the current value corresponding to the current state of the vehicle can be determined as the limit reference current value, wherein the current value corresponding to the stationary state is greater than the current value corresponding to the driving state. As mentioned above, the current state of the vehicle at any of the aforementioned moments may be a stationary state (i.e., the vehicle remains stationary when the driver turns the steering wheel beyond the limit angle) or a driving state (i.e., the driver turns the steering wheel beyond the limit angle while the vehicle is in motion). Therefore, if the vehicle is currently stationary, the larger current value corresponding to the stationary state can be determined as the limit reference current value; conversely, if the vehicle is in a driving state, the smaller current value corresponding to the driving state can be determined as the limit reference current value. In this way, the soft limit strength in the stationary state can be reduced, and the soft limit strength in the driving state can be increased. For example, the limit reference current value can be 2A or 5A, etc., and the present invention does not limit it.

[0094] Step 104b: If the hand torque at any time is not greater than the hand torque threshold, then reduce the upper limit of the driving current. The reduced upper limit of the driving current is less than the limit reference current value.

[0095] If the hand torque at any given moment is not greater than the hand torque threshold, it indicates that the driver is applying relatively little force, and a smaller drive current should be supplied to the steering gear. Therefore, the upper limit of the drive current can be lowered, that is, the current value of this adjustable variable, the upper limit of the drive current, can be adjusted (or updated) to be smaller, i.e., the current value can be updated with a smaller current value than the current value (e.g., updating the upper limit of the drive current from 8A to 6A). This will control the drive current of the motor to not exceed the (updated) upper limit for a period of time, thereby improving the soft limit strength during this period.

[0096] In one embodiment, the motor controller can reduce the upper limit of the drive current in various ways. For example, the upper limit of the drive current can be reduced according to a preset first step length, that is, the upper limit is further reduced by a fixed amount each time based on the current value of the upper limit of the drive current. For example, if the aforementioned drive current is 2A and the upper limit of the drive current is equal to 2A at time T0 when the soft limit start condition is exactly met, the first step length can be 10%. Then, each time it is determined that the hand torque at this time is not greater than the hand torque threshold, the upper limit of the drive current is reduced by 0.2A based on the current value of the upper limit of the drive current.

[0097] For example, assuming the aforementioned drive current is 2A and the upper limit of the drive current is equal to 2A at time T0 when the soft-limit start condition is exactly met, if the motor controller determines at time T1, 5ms later, that the current hand torque is not greater than the hand torque threshold (e.g., 10 N·m), it can reduce the current value of the upper limit of the drive current by a step size of 10%, that is, update the current value from 2A to 1.8A. Further, if the motor controller determines at time T2, 5ms later, that the current hand torque is still not greater than 10 N·m, it can continue to reduce the current value of the upper limit of the drive current by a step size of 10%, that is, update the current value from 1.8A to 1.6A. ... until the current value of the upper limit of the drive current is updated to 0, if the current hand torque is still not greater than 10 N·m, the current value of the upper limit of the drive current can be set to -0.2, that is, the drive current is reversed. Of course, if at any time it is determined that the hand torque is greater than 10 N·m, the upper limit of the drive current can be restored to 2A.

[0098] In one embodiment, the motor can be a DC motor, and therefore the drive current input to the motor can be divided into a forward circuit (driving the motor to rotate in the forward direction) and a reverse circuit (driving the motor to rotate in the reverse direction). Therefore, if the hand torque is still not greater than the hand torque threshold when the upper limit of the drive current is reduced to zero, the current direction corresponding to the upper limit of the drive current can be reversed to control the DC motor to rotate in reverse. This method can further significantly enhance the soft-limit strength.

[0099] like Figure 5 As shown, after the steering wheel rotation angle θ exceeds the limit angle θs, if the steering wheel continues to rotate in the direction of increasing θ, the current value of the upper limit of the drive current can be continuously decreased from the limit reference current value Imax according to the first step described above, until it crosses zero, and then increased in the opposite direction. Of course, if it is determined at some point that the hand torque is greater than the hand torque threshold, the current value of the upper limit of the drive current can be restored to the aforementioned Imax.

[0100] For example, the upper limit of the drive current can be reduced according to the second step size corresponding to the current state of the vehicle, wherein the second step size corresponding to the stationary state is smaller than the second step size corresponding to the driving state. As mentioned above, the current state of the vehicle at any given moment may be either stationary or driving, and different second step sizes can be preset for the stationary and driving states respectively. Thus, in the subsequent process of reducing the upper limit of the drive current, if the vehicle is currently stationary, the upper limit can be reduced according to the smaller second step size (e.g., 5%) corresponding to the stationary state; conversely, if the vehicle is driving, the upper limit can be reduced according to the larger second step size (e.g., 20%) corresponding to the driving state. In this way, the steering gear can exhibit different soft limit adjustment strengths when the vehicle is in different states: the soft limit adjustment strength in the driving state is greater than the soft limit adjustment strength in the stationary state, thereby effectively avoiding more serious safety risks that may occur in the driving state.

[0101] In addition, the size of the first step length and the second step length determines the extent to which the current value of the upper limit of the drive current decreases each time, thus determining the soft limit feel. Therefore, the first step length and the second step length can be flexibly set according to the actual situation.

[0102] As mentioned earlier, if the motor's torque threshold remains below the hand torque threshold for an extended period when the soft-limit start condition is met, the motor controller needs to reduce the upper limit of the drive current multiple times. During two consecutive reductions of the upper limit of the drive current, the reduction magnitude of the previous reduction can be equal to the reduction magnitude of the subsequent reduction (e.g., a 10% reduction each time in the aforementioned embodiment) to achieve a near-linear soft-limit feel. Alternatively, the reduction magnitude of the previous reduction can be different from the reduction magnitude of the subsequent reduction to achieve a more flexible and diverse soft-limit feel. For example, the reduction magnitude of the previous reduction can be less than the reduction magnitude of the subsequent reduction (e.g., a 5% reduction the first time, a 10% reduction the second time, a 20% reduction the third time, and a 30% reduction the fourth time, etc.). Furthermore, the reduction magnitude of the previous reduction can also be greater than the reduction magnitude of the subsequent reduction (e.g., a 40% reduction the first time, a 20% reduction the second time, a 10% reduction the third time, and a 5% reduction the fourth time, etc.), which will not be elaborated further. The above reduction magnitudes can be flexibly set according to actual needs, and this invention does not impose any limitations on this.

[0103] This concludes the explanation of how to adjust the upper limit of the drive current when the aforementioned soft-limit start-up conditions are met. In fact, the upper limit of the drive current can also be adjusted even when the soft-limit start-up conditions are not met to achieve a better soft-limit effect.

[0104] In one embodiment, when the steering wheel rotation angle is less than the limit angle, a preset non-limit reference current value can be set as the upper limit of the drive current, that is, the current value of the upper limit of the drive current is updated to the aforementioned non-limit reference current value (the specific update method is similar to the update process of the limit reference current value). The non-limit reference current value can be the same as the aforementioned limit reference current value (e.g., both are 2A); of course, they can also be different, and this invention does not limit this.

[0105] In another embodiment, when the steering wheel rotation angle is not less than the limit angle and the steering wheel is rotating in the direction that reduces the rotation angle, the limit reference current value can be set as the upper limit of the drive current. For example, in the aforementioned case of a = 150°, if the steering wheel starts to rotate clockwise after rotating counterclockwise to 160°, the current value of the upper limit of the drive current can be directly set as the aforementioned limit reference current value, without further explanation.

[0106] It should be noted that at any given moment, regardless of the specific upper limit of the drive current set, the value of the motor's drive current will always be less than that upper limit (the reverse direction mentioned above should also be considered as less than that upper limit). This allows for effective control of the drive current, and consequently, strong control of the soft-limit rotation angle.

[0107] In one embodiment, the motor controller can also determine the drive current at any given moment based on the hand torque, the magnitude of which is positively correlated with the hand torque. A larger hand torque results in a larger drive current (and thus a larger power assist torque output by the steering gear), thereby amplifying the hand torque applied by the user and helping the driver to steer the vehicle with less hand force – this is the meaning of "power assist." Alternatively, the drive current can be determined based on the vehicle speed at any given moment, the magnitude of which is negatively correlated with the vehicle speed. A higher vehicle speed results in a smaller drive current (and thus a smaller power assist torque output by the steering gear), requiring the driver to apply greater hand force to turn the steering wheel at high speeds. This avoids large steering errors caused by small steering wheel movements at high speeds, improving user control and driving safety.

[0108] This solution abandons the open-loop control scheme in related technologies that fixes the upper limit of the drive current below the soft limit current threshold when the soft limit start condition is met. Instead, it introduces the concept of a "hand torque threshold" and corresponding control logic into the corner soft limit function to achieve closed-loop control of the upper limit of the drive current, thereby effectively limiting the steering wheel rotation angle within the allowable range of the corner soft limit function. Specifically, when the soft limit start condition is met, the hand torque is determined and the upper limit of the drive current is adjusted accordingly: if the hand torque at any moment is greater than the hand torque threshold, the limit reference current value is set to the upper limit of the drive current (i.e., the upper limit of the drive current is adjusted to the limit reference current value); if the hand torque at any moment is not greater than the hand torque threshold, the upper limit of the drive current is reduced, and the reduced upper limit of the drive current is less than the limit reference current value (i.e., the upper limit of the drive current is adjusted to be less than the limit reference current value).

[0109] It is understandable that, since the drive current input to the motor at any given time is not greater than the upper limit of the drive current at that time, and the torque output terminal is used to output the assist torque that is positively correlated with the magnitude of the drive current, after adjusting the upper limit of the drive current using the aforementioned control logic when the soft limit start condition is met, the assist torque output by the steering gear is also adjusted accordingly.

[0110] If the driver turns the steering wheel while the vehicle is stationary (i.e., the vehicle is stationary when the aforementioned soft-limit activation conditions are met), the large sliding friction between the tires and the ground (resistance torque is high) results in a large hand torque on the steering wheel. This hand torque exceeds the hand torque threshold, activating the soft-limit function. The upper limit of the drive current is adjusted to a larger limit reference current value, causing the steering gear to output a larger assist torque (i.e., the limiting effect is weaker), thus gradually reducing the hand torque output by the user. This process prevents the steering wheel from rebounding due to deformation of mechanical components exceeding the assist torque, improving safety; it also allows the hand torque to gradually decrease until the steering wheel stops turning, effectively limiting the steering wheel's rotation angle within the allowable range of the soft-limit function.

[0111] If the driver turns the steering wheel while the vehicle is in motion (i.e., the vehicle is in motion when the aforementioned soft limit activation conditions are met), the steering wheel experiences a smaller hand torque because there is less rolling friction between the tires and the ground (resistance torque is lower at this time). Consequently, the hand torque does not exceed the hand torque threshold, ensuring the soft limit function remains effective. The upper limit of the drive current will be adjusted to be less than the limit reference current value, resulting in a smaller power assist torque output from the steering gear (i.e., a stronger limit at this time). This effectively avoids various safety hazards that may result from the failure of the soft limit function during vehicle operation.

[0112] In summary, this solution ensures the effectiveness of the steering angle soft limit function whether the vehicle is stationary or in motion. It not only effectively limits the steering wheel rotation angle within the allowable range of the steering angle soft limit function, but also effectively avoids various safety hazards, demonstrating significant improvement.

[0113] Figure 6 This is a schematic structural diagram of a motor controller according to an embodiment of the present invention. Please refer to it. Figure 6 At the hardware level, the device includes a processor 601, a network interface 602, memory 603, non-volatile memory 604, and an internal bus 605, and may also include other hardware required for business operations. One or more embodiments of the present invention can be implemented in software, for example, the processor 601 reads the corresponding computer program from the non-volatile memory 604 into memory 603 and then runs it. Of course, in addition to software implementation, one or more embodiments of the present invention do not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0114] Figure 7 This invention illustrates a block diagram of a steering gear control device according to an embodiment of the invention. Please refer to... Figure 7 This device can be applied to, for example Figure 6 The motor controller shown is used to implement the technical solution described in this invention. The steering gear includes a motor and a torque output terminal. At any given time, the drive current input to the motor does not exceed the upper limit of the drive current at that time. The torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the vehicle wheels to steer. This device includes:

[0115] The hand torque determining unit 701 is used to determine the hand torque for driving the steering wheel to rotate when the rotation angle of the steering wheel of the vehicle is not less than the limit angle and the steering wheel is rotated in the direction that increases the rotation angle.

[0116] The first setting unit 702 is used to set the limit reference current value to the upper limit of the driving current if the hand torque is greater than the hand torque threshold at any time.

[0117] The upper limit reduction unit 703 is used to reduce the upper limit of the driving current if the hand torque at any time is not greater than the hand torque threshold, and the reduced upper limit of the driving current is less than the limit reference current value.

[0118] Optionally, the hand torque determining unit 701 is specifically used for:

[0119] The hand torque is determined multiple times at fixed intervals; or,

[0120] The hand torque is determined multiple times based on an interval that is negatively correlated with the rotational speed of the steering wheel.

[0121] Optionally, the hand torque determining unit 701 is specifically used for:

[0122] In the case where the steering gear also includes a torque input terminal connected to the steering wheel, the hand torque detected and transmitted by a first sensor to the torque input terminal is received; or,

[0123] The hand torque is received by a second sensor that detects and transmits the torque for the steering wheel or its connected rotating device.

[0124] Optionally, the first setting unit 702 is specifically used for:

[0125] Determine the preset hand torque threshold; or,

[0126] The hand torque value corresponding to the current driver's identity information is determined as the hand torque threshold.

[0127] Optionally, the first setting unit 702 is specifically used for:

[0128] Determine the preset limit reference current value; or,

[0129] The current value corresponding to the current state of the vehicle is determined as the limit reference current value, wherein the current value corresponding to the stationary state is greater than the current value corresponding to the driving state.

[0130] Optionally, the upper limit reduction unit 703 is specifically used for:

[0131] The upper limit of the drive current is reduced according to the preset first step length; or,

[0132] The upper limit of the drive current is reduced according to the second step size corresponding to the current state of the vehicle, wherein the second step size corresponding to the stationary state is smaller than the second step size corresponding to the driving state.

[0133] Optionally, in two consecutive reductions of the upper limit of the drive current, the reduction magnitude of the previous reduction is not equal to the reduction magnitude of the subsequent reduction.

[0134] Optionally, the motor is a DC motor, and the upper limit reduction unit 703 is specifically used for:

[0135] If the hand torque is still not greater than the hand torque threshold when the upper limit of the drive current is reduced to zero, the current direction corresponding to the upper limit of the drive current is reversed to control the DC motor to reverse.

[0136] Optional, also includes:

[0137] The second setting unit 704 is used to set a preset non-limit reference current value as the upper limit of the drive current when the rotation angle of the steering wheel is less than the limit angle; or...

[0138] The third setting unit 705 is used to set the limit reference current value to the upper limit of the driving current when the rotation angle of the steering wheel is not less than the limit angle and the steering wheel is rotated in the direction of reducing the rotation angle.

[0139] Optional, also includes:

[0140] The first current determining unit 706 is configured to determine the driving current at any given time based on the hand torque, wherein the magnitude of the driving current is positively correlated with the magnitude of the hand torque; and / or,

[0141] The second current determination unit 707 is used to determine the driving current at any given time based on the vehicle speed, wherein the magnitude of the driving current is negatively correlated with the vehicle speed.

[0142] This invention also proposes a steering gear, which includes a motor controller, a motor, and a torque output terminal. At any given time, the drive current input to the motor does not exceed the upper limit of the drive current at that time. The torque output terminal is used to output a power assist torque that is positively correlated with the magnitude of the drive current to drive the vehicle wheels to steer. The motor controller is used for:

[0143] When the steering wheel of the vehicle rotates at an angle not less than a limit angle and the steering wheel is rotated in a direction that increases the rotation angle, the hand torque for driving the steering wheel to rotate is determined.

[0144] If the hand torque at any moment is greater than the hand torque threshold, then the limit reference current value is set to the upper limit of the drive current;

[0145] If the hand torque at any given time is not greater than the hand torque threshold, then the upper limit of the driving current is reduced, and the reduced upper limit of the driving current is less than the limit reference current value.

[0146] This invention also proposes a vehicle on which a steering system as described in any of the foregoing embodiments is installed.

[0147] While this invention contains numerous specific details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather are primarily intended to describe features of specific embodiments of particular inventions. Certain features described in the multiple embodiments of this invention may also be implemented in combination in a single embodiment. On the other hand, various features described in a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Furthermore, while features may function in certain combinations as described above and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and a claimed combination may refer to a sub-combination or a variation of a sub-combination.

[0148] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0149] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings are not necessarily shown in a specific order or sequence to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a steering gear, characterized in that, The steering gear includes a motor and a torque output terminal. The motor is a DC motor, and the drive current input to the motor at any given time does not exceed the upper limit of the drive current at that time. The torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the vehicle wheels to steer. The method includes: When the steering wheel of the vehicle rotates at an angle not less than a limit angle and the steering wheel is rotated in a direction that increases the rotation angle, the hand torque for driving the steering wheel to rotate is determined. If the hand torque at any moment is greater than the hand torque threshold, then the limit reference current value corresponding to the current state of the vehicle is set as the upper limit of the driving current, wherein the limit reference current value corresponding to the stationary state is greater than the limit reference current value corresponding to the driving state. If the hand torque at any given moment is not greater than the hand torque threshold, then the upper limit of the drive current is reduced, including: if the hand torque is still not greater than the hand torque threshold when the upper limit of the drive current is reduced to zero, then the current direction corresponding to the upper limit of the drive current is reversed to control the DC motor to reverse, wherein the reduced upper limit of the drive current is less than the limit reference current value.

2. The method according to claim 1, characterized in that, Determining the hand torque that drives the steering wheel to rotate includes: The hand torque is determined multiple times at fixed intervals; or, The hand torque is determined multiple times based on an interval that is negatively correlated with the rotational speed of the steering wheel.

3. The method according to claim 1, characterized in that, Determining the hand torque that drives the steering wheel to rotate includes: In the case where the steering gear also includes a torque input terminal connected to the steering wheel, the hand torque detected and transmitted by a first sensor to the torque input terminal is received; or, The hand torque is received by a second sensor that detects and transmits the torque for the steering wheel or its connected rotating device.

4. The method according to claim 1, characterized in that, Determining the hand torque threshold includes: Determine the preset hand torque threshold; or, The hand torque value corresponding to the current driver's identity information is determined as the hand torque threshold.

5. The method according to claim 1, characterized in that, The reduction of the upper limit of the drive current includes: The upper limit of the drive current is reduced according to the preset first step length; or, The upper limit of the drive current is reduced according to the second step size corresponding to the current state of the vehicle, wherein the second step size corresponding to the stationary state is smaller than the second step size corresponding to the driving state.

6. The method according to claim 1, characterized in that, In two consecutive reductions of the upper limit of the drive current, the reduction magnitude of the previous reduction is not equal to the reduction magnitude of the subsequent reduction.

7. The method according to claim 1, characterized in that, Also includes: When the rotation angle of the steering wheel is less than the limit angle, the preset non-limit reference current value is set as the upper limit of the drive current. or, When the rotation angle of the steering wheel is not less than the limit angle and the steering wheel is rotated in a direction that reduces the rotation angle, the limit reference current value is set to the upper limit of the drive current.

8. The method according to claim 1, characterized in that, Also includes: The driving current at any given moment is determined based on the hand torque, and the magnitude of the driving current is positively correlated with the magnitude of the hand torque. And / or, The driving current at any given moment is determined based on the vehicle speed, and the magnitude of the driving current is negatively correlated with the vehicle speed.

9. A steering gear control device, characterized in that, The steering gear includes a motor and a torque output terminal. The motor is a DC motor, and the drive current input to the motor at any given time does not exceed the upper limit of the drive current at that time. The torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the vehicle wheels to steer. The device includes: A hand torque determining unit is used to determine the hand torque for driving the steering wheel to rotate when the rotation angle of the steering wheel of the vehicle is not less than the limit angle and the steering wheel is rotated in the direction that increases the rotation angle. The first setting unit is configured to set the limit reference current value corresponding to the current state of the vehicle to the upper limit of the driving current if the hand torque at any time is greater than the hand torque threshold, wherein the limit reference current value corresponding to the stationary state is greater than the limit reference current value corresponding to the driving state. The upper limit reduction unit is used to reduce the upper limit of the drive current if the hand torque at any time is not greater than the hand torque threshold. The upper limit includes: if the hand torque is still not greater than the hand torque threshold when the upper limit of the drive current is reduced to zero, the current direction corresponding to the upper limit of the drive current is reversed to control the DC motor to reverse. The reduced upper limit of the drive current is less than the limit reference current value.

10. A steering system, characterized in that, The steering system includes a motor controller, a motor, and a torque output terminal. The motor is a DC motor, and the drive current input to the motor at any given time does not exceed the upper limit of the drive current at that time. The torque output terminal is used to output an assist torque that is positively correlated with the magnitude of the drive current to drive the vehicle wheels to steer. The motor controller is used for: When the steering wheel of the vehicle rotates at an angle not less than a limit angle and the steering wheel is rotated in a direction that increases the rotation angle, the hand torque for driving the steering wheel to rotate is determined. If the hand torque at any moment is greater than the hand torque threshold, then the limit reference current value corresponding to the current state of the vehicle is set as the upper limit of the driving current, wherein the limit reference current value corresponding to the stationary state is greater than the limit reference current value corresponding to the driving state. If the hand torque at any given moment is not greater than the hand torque threshold, then the upper limit of the drive current is reduced, including: if the hand torque is still not greater than the hand torque threshold when the upper limit of the drive current is reduced to zero, then the current direction corresponding to the upper limit of the drive current is reversed to control the DC motor to reverse, wherein the reduced upper limit of the drive current is less than the limit reference current value.

11. A vehicle, characterized in that, It is equipped with the steering gear as described in claim 10.

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