A steering wheel hand-off detection method, system, device, and medium

Abstract

The application discloses a steering wheel hand-off detection method, system, device and medium. The method comprises the following steps: considering the inertia effect and damping effect of a steering wheel, a dynamic model of an automobile steering system is established; a torsion bar torque and a steering wheel rotation angle are obtained; a driver hand torque is observed through a driver hand torque observer; a state equation of the automobile steering system is established by taking the driver hand torque as a state variable and combining the dynamic model of the automobile steering system; the driver hand torque observer is established according to the state equation of the automobile steering system and a super-spiral sliding mode control algorithm; and the hand-off detection result is obtained by comparing the observed driver hand torque with a torque threshold value and a time threshold value. The application considers the inertia effect and damping effect of the steering wheel, reduces the influence of the interference torque on the observation result, can obtain more accurate driver hand torque, and effectively suppresses the chattering phenomenon of the traditional sliding mode observer by using the observer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile safe driving, in particular to a steering wheel hand-off detection method, system, device and medium. BACKGROUND

[0002] The Society of Automotive Engineers (SAE) divides the automation level of vehicles into five stages, and only when the vehicle reaches the highest automation level, the human driver is no longer needed to operate the vehicle. At present, the automatic driving technology popularized by various automobile manufacturers is generally at the L2 stage, which belongs to the automation level of assisted driving, and the main driver and person responsible for driving is the driver. In the working condition of intelligent assisted driving of the vehicle, the driver's hands should not leave the steering wheel. In order to avoid the potential risks caused by the driver leaving the steering wheel due to special reasons or bad habits, it is of great significance to develop an accurate and timely steering wheel hand-off detection function.

[0003] Steering wheel hand-off detection is a key technology to ensure driving safety, which needs to correctly identify the state of the driver's hands operating the steering wheel, so as to issue a sound, light or other warning to the driver, exit the assisted driving function or even force the vehicle to stop on the roadside when a specific condition is met. When an emergency occurs, the driver actively controls the steering wheel, and the system needs to identify the driver's control intention in time and return the control right to the driver.

[0004] There are three main steering wheel solutions in the industry: (1) integrating sensors such as capacitive sensors and pressure sensors in the steering wheel to directly detect whether the driver's hands are on the steering wheel. This solution requires additional sensors, which is difficult to calibrate and is easily disturbed; (2) relying on computer vision algorithms to detect, locate and track the driver's hands. This solution has higher accuracy, but also has higher cost and difficulty, and also faces the problem of personal privacy security. (3) comparing the steering wheel torque with a preset standard value to detect the driver's hand-off state. This solution requires a high torque sensor for the steering system, and is easily affected by driving habits and external environment, resulting in a high misjudgment rate.

[0005] In the patent application JP2017-206071A of Toyota Motor Corporation, a method for obtaining the hand torque of the driver on the steering wheel is proposed. The method calculates the inertial torque and damping torque of the steering wheel and steering column through the steering wheel angle sensor in the steering system, obtains the torsion bar torque through the torque sensor, and adds the three torques to obtain the hand torque of the driver. This method requires additional steering wheel angle sensors, and has high requirements for the real-time and synchronization of the sensors. The calculation process lacks a feedback adjustment mechanism, and the hand torque of the driver obtained by this method used for steering wheel hand-off detection will result in low reliability. SUMMARY

[0006] To address at least one of the problems existing in the prior art, this invention provides a method, system, device, and medium for detecting steering wheel hands-off. It uses a driver's hand torque observer to estimate the driver's hand torque to determine the driver's steering wheel operation state, without requiring additional sensors, and its accuracy is higher than that of general hands-off detection methods based on torque sensors.

[0007] To achieve the objective of this invention, a method for detecting steering wheel hand-off issues is provided, comprising the following steps:

[0008] Considering the inertial and damping effects of the steering wheel, a dynamic model of the car steering system is established.

[0009] Obtain the torsion bar torque and steering wheel angle:

[0010] The driver's hand torque is observed by a driver's hand torque observer. The driver's hand torque is used as a state variable. The state equation of the vehicle steering system is established by combining the dynamic model of the vehicle steering system. The driver's hand torque observer is established based on the state equation of the vehicle steering system and the super-helical sliding mode control algorithm.

[0011] The torque threshold and time threshold are compared with the observed driver's hand torque to obtain the hand-off detection result.

[0012] Furthermore, when establishing the dynamic model of the vehicle steering system, a column-type power steering system (CEPS) is taken as the research object, and dynamic models of the steering column and torque sensor are established separately. During driving, when the driver turns the steering wheel, it inputs an angle to the input shaft of the torsion bar, and the torsion bar generates torque due to the difference in angles. The steering system determines how to output the assist torque based on the torque signal and the vehicle speed signal. The steering dynamic model of the CEPS system specifically includes:

[0013] Steering column:

[0014] Torque sensor: K(θ) sw -θ e ) = T tb (2)

[0015] Among them, J sw It is the moment of inertia of the steering wheel, B sw K is the steering wheel damping coefficient, K is the torsion bar stiffness, and θ is the steering wheel damping coefficient. sw It is the steering wheel angle (torque bar input shaft angle), θ e It is the pinion rotation angle (torsion bar output shaft rotation angle), T d It is the driver's hand torque, T tbIt is the output value of the torque sensor (torsion bar torque).

[0016] Furthermore, in obtaining the torsion bar torque and steering wheel angle, a combination of a TOS sensor and an angle encoder is used to obtain the torsion bar torque and the power steering motor angle respectively, and then the steering wheel angle is calculated through the transmission ratio between the motor angle and the steering wheel angle; or, the torsion bar torque and steering wheel angle are obtained simultaneously through a TAS sensor.

[0017] Compared to conventional sliding mode observer algorithms, the super-spiral sliding mode observer significantly suppresses chattering in the observation results. Furthermore, the driver's hand torque observer design incorporates the inertial and damping effects of the steering wheel, effectively reducing the impact of interfering torques on the driver's hand torque observation.

[0018] The hands-off detection process incorporates two calibrated parameters: a torque threshold and a time threshold. The specific process involves comparing the observed driver's hand torque with the torque threshold in each detection cycle. If the driver's hand torque is greater than the torque threshold, a preset value is added to the counter. When the counter reaches its maximum value, it indicates that the duration has reached the hands-off detection time threshold, and the driver is determined to have both hands on the steering wheel. If the driver's hand torque is less than the torque threshold, a preset value is subtracted from the counter in each counting cycle. When the counter reaches its minimum value, it indicates that the duration has reached the hands-off detection time threshold, and the driver is determined to have both hands off the steering wheel. Otherwise, the determination result is the same as the previous cycle.

[0019] Torque thresholds can be calibrated experimentally. Due to factors such as road surface roughness, torque sensor zero-point drift, and residual friction, the torque sensor output may deviate from zero even when the driver's hands are off the steering wheel. Therefore, it is necessary to calibrate the corresponding torque thresholds under different vehicle speeds, loads, and road conditions. This allows for the accurate differentiation of the driver's hand-operated steering wheel state by comparing the observed relationship between the driver's hand torque and the torque threshold under different operating conditions.

[0020] The time threshold can be calibrated based on regulations or driving experience: for example, the time threshold used by the hands-off detection function to identify when the steering wheel switches from "hands off" to "hands on" or from "hands on" to "hands off" under different driving conditions can be set to different values.

[0021] The counter has the following characteristics: In each counting cycle, the preset value incremented by the counter should be greater than the preset value decremented. This is because hands-off detection requires rapid identification when the driver takes over the steering wheel; however, to avoid false positives when the driver's hands leave the steering wheel, the driver's hand force must remain below the torque threshold for a sufficiently long period before "hands off" is confirmed. Confidence can be calculated based on the counter value at the current moment. The closer the count value is to the maximum value, the higher the confidence level for "holding" the steering wheel, and vice versa.

[0022] The present invention provides a steering wheel hands-off detection system, comprising the following modules:

[0023] The dynamics model building module is used to build dynamics models of the vehicle steering system;

[0024] The sensor signal acquisition module is used to acquire the torsion bar torque and steering wheel angle.

[0025] The driver hand torque observer module is used to observe the driver hand torque through the driver hand torque observer. The driver hand torque is used as a state variable. The state equation of the vehicle steering system is established by combining the dynamic model of the vehicle steering system. The driver hand torque observer is established based on the state equation of the vehicle steering system and the super-helical sliding mode control algorithm.

[0026] The hands-off detection module compares the torque threshold and time threshold with the observed driver's hand torque to obtain the hands-off detection result.

[0027] The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the aforementioned steering wheel hands-off detection method.

[0028] The present invention provides a computer-readable storage medium storing a computer program, characterized in that the computer program, when executed by a processor, implements the aforementioned steering wheel hands-off detection method.

[0029] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0030] 1) When establishing the dynamic model, the inertial effect and damping effect of the steering wheel were considered, which reduced the influence of the interference torque on the observation results and obtained a more accurate driver's hand torque.

[0031] 2) Establish a super-helical sliding mode observer to observe the driver's hand torque. This observer has good robustness and can effectively suppress the chattering phenomenon of traditional sliding mode observers.

[0032] 3) In the process of determining the hand-off detection, the torque threshold and time threshold can be based on experimental calibration, so as to adapt to different working conditions and reduce the possibility of misjudgment in the hand-off detection. Attached Figure Description

[0033] Figure 1 This is a simplified structural diagram of the CEPS steering system in an embodiment of the present invention.

[0034] Figure 2 This is a simplified schematic diagram of the steering column and torque sensor model in an embodiment of the present invention.

[0035] Figure 3 This is a structural block diagram of the superspiral sliding mode observer in an embodiment of the present invention. This represents the operation of taking the absolute value and then the square root, x represents the multiplication operation, and S represents the differentiation of the input data. This indicates the integration operation.

[0036] Figure 4 This is a flowchart of the hand-removal detection and judgment logic in an embodiment of the present invention.

[0037] Figure 5 This is a comparison chart of the torsion bar torque obtained from the actual vehicle test and the observed driver's hand torque in the embodiments of the present invention.

[0038] Figure 6 This is a comparison chart of the actual steering wheel operation detection state and the hands-free detection results obtained from the real vehicle test in this embodiment of the invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer and more explicit, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0040] This invention provides a method for detecting steering wheel release based on estimating driver hand torque using a superspiral sliding mode observer, comprising the following steps:

[0041] Step 1: Considering the inertial and damping effects of the steering wheel, establish a dynamic model of the car steering system. Based on this mathematical model, a super-helical sliding mode observer will be designed.

[0042] Dynamic models of the steering column and torque sensor are established, taking the column-type power steering system (CEPS) as the research object. For example... Figure 1As shown, in the CEPS system, when the driver turns the steering wheel, it inputs an angle to the input shaft of the torsion bar. The torsion bar generates torque due to the difference in the upper and lower angles. The torque sensor calculates the torsion bar torque using the Hall effect. Combined with the vehicle speed signal, the ECU can determine the magnitude of the output assist torque and control the motor to output the corresponding torque. The torque output by the motor is amplified by the reducer and applied to the output shaft. The pinion on the output shaft drives the rack to move, thereby realizing the steering function of the car.

[0043] The CEPS system is further simplified to a steering column and torque sensor model, such as Figure 2 As shown, the mathematical equations, i.e., the dynamic model of the car steering system, are established as follows:

[0044] Steering column:

[0045] Torque sensor: K(θ) sw -θ e ) = T tb (2)

[0046] Among them, J sw It is the moment of inertia of the steering wheel, B sw K is the steering wheel damping coefficient, K is the torsion bar stiffness, and θ is the steering wheel damping coefficient. sw It is the steering wheel angle (torque bar input shaft angle), θ e It is the pinion rotation angle (torsion bar output shaft rotation angle), T d It is the driver's hand torque, T tb It is the output value of the torque sensor (torsion bar torque). The inertial torque represents the inertial effect caused by the steering wheel. The damping torque represents the damping effect caused by the steering wheel. J sw B sw K can be obtained by consulting relevant information about CEPS products or through testing.

[0047] When the steering wheel is stationary or the speed is very low, the torque value T detected by the torque sensor is... tb Equal to the driver's hand torque T d However, when the steering wheel is in a significant dynamic state, the difference between the two cannot be ignored. Therefore, an observer is designed based on formulas (1) and (2).

[0048] Step 2: Obtain relevant sensor signals: Obtain the torsion bar torque and power steering motor angle from the torque sensor and power steering motor angle encoder in the CEPS system, respectively, and calculate the steering wheel angle based on the transmission ratio between the power steering motor and the steering wheel; utilize the built-in sensors in the CEPS system.

[0049] In some embodiments of the present invention, a combination of a TOS sensor and an angle encoder can be used to acquire the torsion bar torque and the power steering motor angle, respectively, and then the steering wheel angle can be calculated using the transmission ratio between the motor angle and the steering wheel angle; alternatively, only a TAS sensor can be used to acquire both the torsion bar torque and the steering wheel angle simultaneously. In other words, a suitable sensor solution can be selected to acquire the required signals based on existing equipment conditions or cost considerations.

[0050] Step 3: The driver's hand torque is observed using a driver's hand torque observer. The driver's hand torque is used as a state variable. The state equation of the vehicle steering system is established by combining the dynamic model of the vehicle steering system. Based on the state equation of the vehicle steering system and the super-spiral sliding mode control algorithm, the driver's hand torque observer is established.

[0051] Driver's hand torque T d The unknown input in the dynamic model of the vehicle steering system is treated as a state variable. Based on the state equation of the CEPS steering system and the super-torsion sliding mode control algorithm, a driver's hand torque observer is established. In some embodiments of the present invention, the stability of the observer is verified according to Lyapunov's second method, and the range of values ​​of the observer parameters (including c (constant), γ (constant), g (feedback gain coefficient), and coefficients k1 and k2) that meet the requirements are determined to ensure that the driver's hand torque observer can accurately observe the driver's hand torque.

[0052] The structural block diagram of the driver's hand torque observer is as follows: Figure 3 As shown, the driver's hand torque observer is a superhelical sliding mode observer. The specific design method of the superhelical sliding mode observer is as follows:

[0053] Driver's hand torque T d Treat it as a state variable, while also taking into account the sampling period T of the torque sensor. s The sampling period T is relatively small, and is generally considered to be small. s Driver's hand torque T d No change, therefore it is considered Based on the dynamic model of the vehicle steering system, the state equation of the CEPS steering system can be expressed by the following formula:

[0054]

[0055] Where t is time and ω is the angular velocity of the steering wheel.

[0056] The driver's hand torque observer based on the super-twisting sliding mode algorithm is designed as follows:

[0057]

[0058] Where U is the superspiral sliding mode control law, P is a function of U, representing the compensation amount for the observed steering wheel speed, and g is the feedback gain coefficient. This is an estimated value for the steering wheel angle. This is an estimated value for the angular velocity of the steering wheel. This is an estimate of the driver's hand torque. It is the derivative of the angular velocity of the steering wheel. It is an estimate of the derivative of the steering wheel angle.

[0059] Let the steering wheel angle estimation error be e1, the steering wheel speed estimation error be e2, and the driver's hand torque estimation error be e3, then we have:

[0060]

[0061] The sliding surface is designed as follows:

[0062]

[0063] Where c is a constant, and in some embodiments of the present invention, c>0 can be taken.

[0064] Since the solution for s=0 is:

[0065]

[0066] By setting s = 0, we can guarantee that the errors e1 and e2 will decrease exponentially to near 0. The larger c is, the faster the error converges.

[0067] To ensure that the system moves towards s=0 during sliding mode motion, it is necessary to analyze the derivative of s and then select an appropriate control law u.

[0068]

[0069] The function P can be designed as:

[0070]

[0071] Where γ is a constant.

[0072] but:

[0073]

[0074] When the system moves to the sliding surface, it satisfies At this point:

[0075]

[0076] For the above equation, since J sw To ensure that the estimation error of the driver's hand torque can quickly approach 0, we can set:

[0077]

[0078] The approach law of the superspiral sliding mode algorithm can generally be expressed as:

[0079]

[0080] in, The variable v is a discontinuous differential term introduced in the superspiral sliding mode algorithm. v is an auxiliary control variable, an intermediate variable introduced without actual physical meaning. The role of v is to help the system slide stably on the sliding surface and further suppress the effects of external disturbances and unmodeled dynamics. The introduction of v is equivalent to adding an integral term to the control law, making the superspiral sliding mode control law somewhat similar to a proportional-integral (PI) controller, which can significantly reduce high-frequency jitter in the control input.

[0081] Where k1 and k2 are design parameters and are greater than zero, and d is the bounded disturbance of the system. Based on the above analysis, we can obtain:

[0082]

[0083] Here, δ represents the upper limit of the absolute value of the bounded perturbation, which can take a value greater than |d|.

[0084] Based on the above analysis, the following approach rate is selected:

[0085]

[0086] Combining equations (9) and (12), the control law can be determined as follows:

[0087]

[0088] To verify the stability of the observer and determine the range of values ​​for k1 and k2, the Lyapunov function is chosen as follows:

[0089]

[0090] set up:

[0091]

[0092] but:

[0093]

[0094] in:

[0095]

[0096] Substituting the perturbation boundary condition, i.e., formula (13), into the equation, we get:

[0097]

[0098] in:

[0099]

[0100] In order to To ensure the system's global asymptotic stability, Q must be greater than 0; that is, the gain must satisfy the following condition:

[0101]

[0102] As can be seen from the above formula, when the coefficients k1 and k2 are chosen to be relatively large numbers, the stability of the system can be guaranteed.

[0103] Compared to conventional sliding mode observer algorithms, the super-spiral sliding mode observer significantly suppresses chattering in the observation results. Furthermore, the driver's hand torque observer design incorporates the inertial and damping effects of the steering wheel, effectively reducing the impact of interfering torques on the driver's hand torque observation.

[0104] This invention treats the driver's hand torque, which is an unknown input, as a state variable, and uses the torsion bar torque and steering wheel angle as input variables to establish a super-helical sliding mode observer. The observer parameters are adjusted to ensure the observer is stable and the observation error can converge to 0, thereby observing the accurate driver's hand torque.

[0105] Step 4: Hands-off detection judgment: Compare the torque threshold and time threshold with the observed driver's hand torque to obtain the hands-off detection result.

[0106] The flowchart of the hand-drop detection and judgment logic is as follows: Figure 4 As shown, two calibration parameters are introduced: a torque threshold and a time threshold. If the driver's hand torque observed by the driver's hand torque observer is less than the torque threshold, and the duration of the driver's hand torque being less than the torque threshold is greater than the time threshold, then it is considered that the driver's hands have left the steering wheel, and a "hands off" signal is output. If the observed driver's hand torque is greater than the torque threshold, and the duration of the driver's hand torque being greater than the torque threshold is greater than the time threshold, then it is considered that the driver's hands are gripping the steering wheel, and a "gripping" signal is output. Otherwise, the original hands-off detection result remains unchanged.

[0107] In some embodiments of the present invention, in step 4, the torque threshold can be calibrated experimentally. Due to factors such as road surface bumps, zero-point drift of the torque sensor, and residual friction of the torque sensor, the output of the torque sensor may deviate from zero even when the driver's hands are off the steering wheel. Therefore, in some embodiments of the present invention, the corresponding torque threshold is calibrated through experimental testing under different vehicle speeds, loads, and road conditions, forming a torque threshold calibration table. The torque threshold under corresponding operating conditions can then be easily confirmed by looking up the table. This allows for the accurate differentiation of the driver's hand-operated steering wheel state under different operating conditions by comparing the observed relationship between the driver's hand torque and the torque threshold.

[0108] In other embodiments, after obtaining the torque threshold under different vehicle speeds, loads, and road conditions through experimental testing and calibration, a mathematical relationship between information such as vehicle speed, load, and road conditions and the torque threshold can be established based on the calibrated different vehicle speeds, loads, road conditions and the corresponding torque threshold. Subsequently, the torque threshold under the corresponding working conditions can be obtained through this mathematical relationship.

[0109] In some embodiments of the present invention, in step 4, the time threshold can be calibrated based on regulations or driving experience. For example, under different driving conditions, when the steering wheel switches from "hands off" to "grip" or from "grip" to "hands off," the time threshold for the hands-off detection function can be set to different values. Furthermore, under the same conditions, the time threshold for the steering wheel switching from "hands off" to "grip" should be less than the time threshold for switching from "grip" to "hands off." The time thresholds at different vehicle speeds can be obtained experimentally, forming a time threshold calibration table, which can then be directly used to determine the time threshold. In other embodiments, a mathematical relationship between vehicle speed and time threshold can be established based on the calibrated different vehicle speeds and time thresholds, and this mathematical relationship can be used to calculate and determine the time threshold.

[0110] In this step, the observed driver's hand torque and torque threshold are compared in each detection cycle. If the driver's hand torque is greater than the torque threshold, the counter value is incremented by a preset value. When the counter value reaches its maximum, it means the duration has reached the time threshold for determining whether the driver is holding the steering wheel, and the driver is determined to have both hands on the steering wheel. If the driver's hand torque is less than the torque threshold, the counter is decremented by a preset value in each detection cycle. When the counter value reaches its minimum, it means the duration has reached the time threshold for determining whether the driver is taking their hands off the steering wheel, and the driver is determined to have both hands off the steering wheel. Otherwise, the determination result is the same as the previous detection cycle.

[0111] The preset value increment of the counter should be greater than the preset value decremented each time. This is because hands-off detection requires rapid identification when the driver takes over the steering wheel. When the driver's hands leave the steering wheel, to avoid false positives, the result is only confirmed when the duration of the driver's hand torque being less than the torque threshold reaches a time threshold. Furthermore, the confidence level can be calculated based on the current counter value; the closer the count value is to 50, the higher the confidence level for "holding" the steering wheel, and vice versa.

[0112] In some embodiments of the present invention, a detection cycle is set to 0.02s. When the steering wheel switches from a "hands-free" to a "grip" state, the "grip" state needs to be identified after 0.2s (time threshold). When the observed driver's hand torque is greater than the torque threshold, the counter adds a preset value (set to 5) to each detection cycle. After 10 detection cycles, the counter reaches its maximum value (set to 50), that is, when the counter reaches its maximum value after 0.2s, it can be determined that the driver is gripping the steering wheel with both hands. Similarly, if the steering wheel switches from a "grip" to a "hands-free" state, the "hands-free" state needs to be identified after 2s (time threshold). When the driver's hand torque is less than the torque threshold, the counter subtracts a preset value (set to 0.5) from each detection cycle. After 100 cycles, when the counter reaches its minimum value (set to 0), that is, when the counter reaches its minimum value after 2s, it can be determined that the driver has taken both hands off the steering wheel.

[0113] Step 5: Real vehicle test.

[0114] To evaluate the performance of the hands-off detection (HOD) for steering wheels, in some embodiments of the present invention, a real-vehicle test condition is set as follows: the vehicle travels in a straight line on a non-perfectly flat road surface, and the driver repeatedly grips and releases the steering wheel in 5-second cycles until the experiment ends. Figure 5 It can be seen that when the driver holds the steering wheel, the observed driver's hand torque is close to the torsion bar torque detected by the torque observer; when the driver releases the steering wheel, the torsion bar torque fluctuates significantly due to factors such as road surface interference, but the observed driver's hand torque is almost zero. Therefore, the method proposed in this invention has good robustness.

[0115] like Figure 6 As shown, when the driver switches the steering wheel from "grip" to "ungrip", the hands-off detection will output "ungrip" in 2 seconds. This is to avoid misjudging the situation as "ungrip" as much as possible. When the driver switches the steering wheel from "ungrip" to "grip", the hands-off detection will output "grip" almost immediately. This is to be able to identify the driver's intention to take over in an emergency and return control of the steering wheel to the driver.

[0116] In some embodiments of the present invention, a steering wheel hands-off detection system is provided to implement the steering wheel hands-off detection method provided in the foregoing embodiments. The system includes the following modules:

[0117] The dynamics model building module is used to build dynamics models of the vehicle steering system;

[0118] The sensor signal acquisition module is used to acquire the torsion bar torque and steering wheel angle.

[0119] The driver hand torque observer module is used to observe the driver hand torque through the driver hand torque observer. The driver hand torque is used as a state variable. The state equation of the vehicle steering system is established by combining the dynamic model of the vehicle steering system. The driver hand torque observer is established based on the state equation of the vehicle steering system and the super-helical sliding mode control algorithm.

[0120] The hands-off detection module compares the torque threshold and time threshold with the observed driver's hand torque to obtain the hands-off detection result.

[0121] It also includes a torque threshold confirmation module and a time threshold confirmation module. The torque threshold confirmation module is used to obtain the torque threshold, and the time threshold confirmation module is used to obtain the time threshold.

[0122] In some embodiments of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steering wheel hands-off detection method provided in the foregoing embodiments.

[0123] In some embodiments of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program that, when executed by a processor, implements the steering wheel hands-off detection method provided in the foregoing embodiments.

[0124] This invention takes a CEPS system equipped with a torque sensor as the research object. It uses a super-spiral sliding mode observer to accurately observe the driver's hand torque, and based on the driver's hand torque information, combined with torque and time thresholds, determines whether the driver's steering wheel operation is "hands off" or "holding". Compared with existing technologies, this invention does not incur additional hardware costs; the modeling considers the influence of the steering wheel's inertial and damping effects on hands-off detection; furthermore, the method of using a super-spiral sliding mode observer to observe the driver's hand torque has strong robustness and suppresses the chattering phenomenon of general sliding mode observers; moreover, the torque and time thresholds can be calibrated experimentally to reduce the influence of interference torque on hands-off detection.

[0125] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in this invention may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A steering wheel hand-off detection method, characterized by, The method comprises the following steps: A dynamic model of the automobile steering system is established by considering the inertial effect and damping effect of the steering wheel; The torque of the torsion bar and the steering wheel rotation angle are obtained: The driver hand torque is observed by a driver hand torque observer, wherein the driver hand torque is taken as a state variable, the state equation of the automobile steering system is established in combination with the dynamic model of the automobile steering system, and the driver hand torque observer is established according to the state equation of the automobile steering system and the super-spiral sliding mode control algorithm; The torque threshold and the time threshold are compared with the observed driver hand torque to obtain a hand-off detection result; The stability of the observer is verified according to the second Lyapunov method, and the value range of the required observer parameters is obtained to ensure that the observer can accurately observe the driver hand torque; The driver hand torque is considered as a state variable, and The state equation of the automobile steering system is established as The driver hand torque observer based on the super-spiral sliding mode algorithm is represented as: wherein is a super-twisting sliding mode control law, is a function of represents a compensation of the steering wheel angular velocity observation, is a feedback gain coefficient, is an estimation of the steering wheel angle, is an angular velocity of the steering wheel rotation, is an estimation of the steering wheel angular velocity, is an estimation of the driver hand torque, , is a derivative of the steering wheel angular velocity, , is an estimation of the derivative of the steering wheel angle, is a torsion bar torque, is time, is a moment of inertia of the steering wheel, is a steering wheel damping coefficient;​​ In the formula, the function is: The super-spiral sliding mode control law is represented as: For the above equation, in order to guarantee that the estimation error of the driver hand torque can quickly tend to 0, let: , wherein , is a design parameter and is greater than zero, and: wherein is a sliding surface, is a constant, represents an upper bound of the absolute value of the bounded disturbance; The comparison of the torque threshold and the time threshold with the observed driver hand torque to obtain the hand-off detection result comprises: If the observed driver hand torque is less than the torque threshold and the holding time of the state is greater than the time threshold, it is considered that the driver's hands are off the steering wheel, and this is a hand-off state; if the observed driver hand torque is greater than the torque threshold and the holding time of the state is greater than the time threshold, this is a non-hand-off state.

2. The steering wheel hands off detection method of claim 1, wherein A column type power steering system is taken as the research object, and dynamic models of the steering column and the torque sensor are established: Steering column: Torque sensor: wherein is the moment of inertia of the steering wheel, is the steering wheel damping coefficient, is the torsion bar stiffness, is the steering wheel rotation angle, is the torsion bar output shaft rotation angle, is the driver hand torque, is the torsion bar torque, represents the inertial torque caused by the inertial effect of the steering wheel, represents the damping torque caused by the damping effect of the steering wheel.

3. The steering wheel hands off detection method of claim 1, wherein In the step of obtaining the torque of the torsion bar and the steering wheel rotation angle, a combination of a TOS sensor and an angle encoder is used to obtain the torque of the torsion bar and the rotation angle of the power motor respectively, and the rotation angle of the steering wheel is calculated through the transmission ratio of the motor rotation angle and the steering wheel rotation angle; or the torque of the torsion bar and the rotation angle of the steering wheel are obtained simultaneously through a TAS sensor.

4. The steering wheel hands off detection method of claim 1, wherein In each detection period, the observed driver hand torque and the torque threshold are compared, if the driver hand torque is greater than the torque threshold, the counter value is added by a preset value, when the counter value reaches the maximum value, it means that the duration reaches the time threshold of the holding judgment, and it is judged that the driver's hands hold the steering wheel; if the driver hand torque is less than the torque threshold, the counter is reduced by a preset value in each detection period, when the counter value reaches the minimum value, it means that the duration reaches the time threshold of the hand-off judgment, and it is judged that the driver's hands are off the steering wheel, otherwise, the judgment result is the same as that of the last period.

5. A steering wheel let go detection system characterized by, The system for implementing the method of any one of claims 1-4 comprises the following modules: A dynamic model establishment module for establishing the dynamic model of the automobile steering system; A sensor signal acquisition module for obtaining the torque of the torsion bar and the steering wheel rotation angle: A driver hand torque observer observation module for observing the driver hand torque by the driver hand torque observer, wherein the driver hand torque is taken as a state variable, the state equation of the automobile steering system is established in combination with the dynamic model of the automobile steering system, and the driver hand torque observer is established according to the state equation of the automobile steering system and the super-spiral sliding mode control algorithm; A hand-off detection module is configured to compare the torque threshold and the time threshold with the observed driver hand torque to obtain a hand-off detection result.

6. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The computer program is executed by the processor to implement the steering wheel hand-off detection method in any one of claims 1 to 4.

7. A computer-readable storage medium storing a computer program, wherein the computer program comprises the following steps of: receiving a request for a resource from a client; determining whether the client is authorized to access the resource; and if the client is authorized to access the resource, providing the resource to the client. The computer program is executed by the processor to implement the steering wheel hand-off detection method in any one of claims 1 to 4.

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