Control method and system for recirculating ball type electric power steering

Abstract

This application discloses a control method and system for a recirculating ball type electric power steering system, relating to the field of automotive steering control technology. The method includes constructing and storing a power steering mapping model, a safety threshold model, and a signal transfer function model; acquiring the values ​​of each influencing parameter in real time, and determining whether the values ​​of each influencing parameter meet the numerical range limits of the safety threshold model; if the limits are met, a single-control mode is executed: the first control loop confirms the target power steering current value based on the power steering mapping model and the values ​​of each influencing parameter, and then outputs it; the second control loop analyzes and obtains the control deviation rate corresponding to each control node in the first control loop under the conditions of each influencing parameter value; if the limits are not met, a dual-control mode is executed: the first control loop and the second control loop output the first power steering current value and the second power steering current value respectively, and then select the first or second power steering current value as the target power steering current value. This scheme significantly improves the accuracy of power steering.

Description

Technical Field

[0001] This application belongs to the field of automotive steering control technology, specifically relating to a control method and system for a recirculating ball type electric power steering system. Background Technology

[0002] Compared to rack and pinion steering systems, recirculating ball steering systems rely more on rolling friction, resulting in higher transmission efficiency and easier, more comfortable handling. Currently, recirculating ball steering systems are typically integrated with torque sensors, power steering motors, and electronic control units (ECUs) to form electronic power steering (EPS) systems.

[0003] To achieve the highest level of functional safety and meet the requirements of the ISO 26262 international standard "Functional Safety of Road Vehicles," and to prevent complete power steering failure due to a single point of failure in the control loop, current automotive EPS systems mostly use two independent control loops, typically including two CPUs or MCU microcontrollers. This safety redundancy design ensures driver safety. While ensuring safety and reliability, improving the accuracy and responsiveness of EPS control has become the current research and development direction and key technical problem to be solved for recirculating ball electric power steering systems. Summary of the Invention

[0004] To address the challenge of improving the control precision and responsiveness of recirculating ball electric power steering systems in practical applications while ensuring safety and reliability, this application aims to propose a control method for recirculating ball electric power steering systems. This method accurately and predictively determines the driver's steering intentions and responds accordingly by collecting data on the steering column rotation angle, vehicle status, and the driver's personalized driving preferences. By flexibly configuring two control loops to identify different steering assist needs, it ensures precise steering assist control while automatically performing fault self-diagnosis and selecting the control loop most suitable for the steering requirements, thereby improving the precision and responsiveness of steering control. To further implement this steering system control method, this application also aims to propose a recirculating ball electric power steering system, the specific scheme of which is as follows:

[0005] A control method for a recirculating ball type electric power steering system, based on two independently configured control loops, includes:

[0006] Construct and store an assist mapping model that reflects the correspondence between the target assist current value and each influencing parameter or their combination;

[0007] The numerical ranges corresponding to specific influencing parameters or combinations thereof that do not affect driving safety after power steering failure are analyzed and stored as a safety threshold model.

[0008] Based on the control logic and control parameters of each control node in the control loop, a signal transfer function model of the control loop is constructed.

[0009] Real-time monitoring and acquisition of the values ​​of each influencing parameter, and determination of whether the values ​​of each influencing parameter meet the numerical range limits of the above-mentioned safety threshold model:

[0010] If the constraints are met, then single-control mode will be executed:

[0011] The first control loop determines the target assist current value based on the assist mapping model and the real-time acquired values ​​of various influencing parameters, and then outputs it to the assist motor.

[0012] The second control loop acquires the values ​​of each influencing parameter and the feedback data signals of each control node in the first control loop in response to the above-mentioned influencing parameters. Based on the signal transfer function model, it acquires the deviation rate between the actual feedback signal and the theoretical response signal of each control node in the first control loop, and stores the values ​​of each influencing parameter and the control deviation rate corresponding to each control node in association.

[0013] If the constraints are not met, then dual-control mode will be executed:

[0014] The first control loop and the second control loop acquire the values ​​of each influencing parameter and, based on the aforementioned assist mapping model, respectively confirm the output of the first assist current value and the second assist current value.

[0015] Compare the difference between the first assist current value and the second assist current value. If the difference exceeds a set threshold, select the smaller current value as the target assist current value and output it to the assist motor. If the difference does not exceed the set threshold, select either the first assist current value or the second assist current value as the target assist current value or take the average of the two as the target assist current value.

[0016] The influencing parameters include one or more combinations of vehicle status data, personnel status data, and environmental status data.

[0017] By employing the above technical solution, the values ​​of various influencing parameters are fully considered when performing steering assist control. It is pre-determined whether steering failure will affect driving safety. Under the premise of not affecting driving safety, one control loop is selected for steering assist control, while the other control loop is used to verify the accuracy of steering control. This determines whether the control loop implementing steering assist has any faults and obtains the control deviation of each control node under the current influencing parameters, which helps to improve the accuracy of steering assist. Furthermore, since the target assist current value is directly obtained by combining the monitored influencing parameter values ​​with the assist mapping model, the response speed of steering assist can be significantly improved.

[0018] Furthermore, the vehicle status data includes steering wheel torque magnitude and rate of change, steering wheel angle and angular rate, steering increment and steering accumulation, vehicle speed and vehicle acceleration.

[0019] Personnel status data includes driver head posture and steering wheel grip posture data;

[0020] Environmental condition data includes road and route data, temperature, and wind speed data.

[0021] Through the above technical solutions, when the automotive EPS provides steering assistance, it will not only adjust the magnitude of the assist current based on vehicle status data, but also revise the assist magnitude based on factors such as the environmental conditions in which the vehicle is located, such as crosswind compensation, to make the steering assistance magnitude more precise.

[0022] Furthermore, the control method also includes:

[0023] Acquire and associate the impact parameter data corresponding to each turn of the vehicle;

[0024] Based on the correlation analysis method, the influence parameters related to vehicle steering actions are obtained and stored as steering prediction parameters. A steering intention determination model is then constructed based on the above steering prediction parameters.

[0025] Based on the real-time acquired steering prediction parameters and the steering intention determination model, a steering probability is generated for the vehicle to turn within a set future time period. This steering probability is then compared with a steering determination threshold.

[0026] If the above-mentioned steering probability exceeds the steering judgment threshold, then based on the current values ​​of each influencing parameter and their rate of change, the value range of each influencing parameter in the future set time period is calculated. Based on the above-mentioned value range, the corresponding target assist current value is found in the self-assistance mapping model to form the target assist current prediction range, which is temporarily associated and stored as the pre-assistance mapping model.

[0027] In the single-control mode, the values ​​of each influencing parameter are acquired in real time, and the corresponding target assist current value is found and output based on the above pre-assist mapping model.

[0028] The above technical solution can predict vehicle steering needs in advance and simplify the power steering mapping model based on the predicted influence parameters, making it more scenario-specific. When the steering wheel torque exceeds the set value, the corresponding target power steering current value can be found more quickly and accurately in the simplified pre-power steering mapping model, shortening the power steering response time and improving the accuracy of electric power steering response.

[0029] Furthermore, the control method also includes:

[0030] The percentage of times the first control loop and the second control loop output the target assist current value and obtain the control deviation rate were statistically analyzed.

[0031] The execution actions of the first and second control loops are automatically swapped based on a set period.

[0032] The control deviation rate of each control node in the first and second control loops is associated and stored under the conditions of each influencing parameter value during each turn.

[0033] The proportion of times the control deviation rate of each control node in the first and second control loops does not exceed the first threshold is defined and stored as the control stability rate.

[0034] If the above control stability rate exceeds the set value, the first alarm message will be output.

[0035] Through the above technical solution, the functions performed by the first control loop and the second control loop are automatically switched without affecting driving safety. This allows for the statistical analysis of the control deviation rate of each control node in the two control loops under different influencing parameters. In practical applications, if the control deviation rate of a certain control node deviates from the normal range too many times, it indicates that there is a potential fault. Therefore, the first warning message is output to provide timely warning of potential faults and ensure the control accuracy of the power assist.

[0036] Furthermore, the single-control mode also includes:

[0037] Determine whether the control deviation rate corresponding to each control node in the first and second control loops exceeds the second threshold. If it exceeds the second threshold, then:

[0038] Mark the control node and its corresponding control loop as a suspected fault node and suspected fault loop, and output a second alarm message;

[0039] A non-faulty circuit is selected to obtain the target boost current value.

[0040] With the above technical solution, if the control deviation rate of a certain control node in a certain control loop is too large, it indicates that there is a suspected fault. Therefore, a second alarm message is output. At the same time, in the single control mode, another control loop is selected as the loop for outputting the target boost current value to ensure the accuracy of the output result.

[0041] Furthermore, the single-control mode also includes:

[0042] Based on the control stability rates of each control node in the first and second control loops under different influence parameter values, a preferred mapping model is constructed and stored to reflect the correspondence between the control stability of the first and second control loops and the values ​​of each influence parameter or their combination.

[0043] Based on the real-time acquired impact parameter data and the optimal mapping model, a control loop with a higher control stability under the current impact parameter values ​​is selected to acquire and output the target assist current value.

[0044] Through the above technical solution, in single-control mode, the system can select the control loop with higher control stability to output the target assist current value according to the different values ​​of each influencing parameter, which helps to improve the accuracy of steering assist control.

[0045] To implement the aforementioned control method for a recirculating ball electric power steering system, this application also proposes a control system for a recirculating ball electric power steering system, comprising:

[0046] The data storage unit includes a model storage subunit and a parameter data storage subunit, which are respectively configured to store the assist mapping model, the safety threshold model, the signal transfer function model, and the values ​​of each influencing parameter obtained in real time, as well as the control deviation rate corresponding to each control node in the control loop under the condition of each influencing parameter value;

[0047] The data acquisition unit is configured to collect the influencing parameters, including vehicle status data, personnel status data, and environmental status data.

[0048] The control mode selection unit is configured to obtain the values ​​of each influencing parameter based on real-time monitoring, determine whether the values ​​of each influencing parameter meet the numerical range limit of the above-mentioned safety threshold model, and determine whether the control mode is a single control mode or a dual control mode based on the determination result.

[0049] The power assist control unit, including a first control loop and a second control loop, selects the unit's output to perform the following actions according to the control mode:

[0050] The target assist current value is determined based on the aforementioned assist mapping model and in conjunction with the real-time acquired values ​​of various influencing parameters; or

[0051] The values ​​of each influencing parameter and the feedback data signals of each control node in the first control loop in response to the above-mentioned influencing parameters are obtained. Based on the signal transfer function model, the deviation rate between the actual feedback signal and the theoretical response signal of each control node in the first control loop is obtained. The values ​​of each influencing parameter and the control deviation rate corresponding to each control node are associated and stored.

[0052] The assist output unit is connected to the control mode selection unit. When the control mode is single control mode, it directly outputs the target assist current value.

[0053] When the control mode is dual control mode, the difference between the first assist current value and the second assist current value output by the first control loop and the second control loop is compared. If the difference exceeds the set threshold, the smaller current value is selected as the target assist current value and output. If the difference does not exceed the set threshold, either the first assist current value or the second assist current value is selected as the target assist current value or the average of the two is taken as the target assist current value.

[0054] Furthermore, the system also includes:

[0055] The potential fault warning unit is configured to count the proportion of times the control deviation rate corresponding to each control node in the first control loop and the second control loop does not exceed a first threshold, define and store it as the control stability rate, and output the first alarm information if the control stability rate exceeds the set value.

[0056] The fault alarm unit is configured to determine whether the control deviation rate corresponding to each control node in the first control loop and the second control loop exceeds a second threshold. If it exceeds the second threshold, the control node and its control loop are marked as suspected fault nodes and suspected fault loops, and the second alarm information is output.

[0057] Through the above technical solution, the system can detect faults in the control loop when the vehicle is turning, ensuring the control accuracy of the two control loops.

[0058] Furthermore, the model storage subunit also stores a preferred mapping model;

[0059] The control mode selection unit includes:

[0060] The control loop switching subunit is configured to statistically analyze the percentage of times the first control loop and the second control loop output the target assist current value and obtain the control deviation rate in the single control mode, and automatically switch the execution actions of the first control loop and the second control loop based on a set period.

[0061] The optimal selection subunit is configured to select a control loop with a higher control stability under the current influence parameter value condition based on the real-time acquired influence parameter data and the optimal mapping model, in order to acquire and output the target boost current value.

[0062] Through the above technical solution, when the vehicle is turning, the system will select different control loops for steering control based on different influencing parameter conditions, thereby improving the accuracy of steering control.

[0063] Furthermore, the model storage subunit also stores a steering intention determination model;

[0064] The system also includes:

[0065] The steering probability generation unit is configured to generate the steering probability of the vehicle turning within a set time period in the future based on the steering prediction parameters acquired in real time and the steering intention determination model.

[0066] The pre-assist mapping model generation unit is configured to receive and compare the above steering probability with a steering judgment threshold: if the above steering probability exceeds the steering judgment threshold, then calculate the value range of each influencing parameter in the future set time period based on the current values ​​of each influencing parameter and their rate of change, find the corresponding target assist current value in the self-assist mapping model based on the above value range to form the target assist current prediction range, and temporarily associate and store it as a pre-assist mapping model.

[0067] The assist output unit is data-connected to the pre-assist mapping model generation unit. When the control mode is single control mode, it acquires the values ​​of each influencing parameter in real time and finds the corresponding target assist current value based on the pre-assist mapping model.

[0068] The above technical solution can predict the vehicle's steering probability based on the driver's actions or other influencing parameters, and optimize the power assist mapping model in advance based on the prediction results to improve the system's power assist response speed when steering occurs.

[0069] This application includes at least one of the following beneficial effects:

[0070] (1) By setting a safety threshold model, the values ​​of various influencing parameters are fully considered when performing steering assist control. It is determined in advance whether steering failure will affect driving safety. Under the premise of not affecting driving safety, one control loop is selected for steering assist control, and the other control loop is used to verify the accuracy of steering control. This can ensure the accuracy of the output results of the control loop and improve the accuracy of steering assist.

[0071] (2) By evaluating the control stability of the two control loops, different control loops can be selected under different influence parameter conditions to generate the target assist current value, which can improve the accuracy of the target assist current value.

[0072] (3) By setting a steering intention determination model, the steering action of the vehicle can be predicted based on the obtained influence parameter data, and the power assist mapping model can be optimized in advance. The optimized power assist mapping model can significantly improve the response speed of the system steering assist. Attached Figure Description

[0073] Figure 1This is a flowchart illustrating the control method of this application;

[0074] Figure 2 A schematic diagram illustrating a method for generating target boost current values ​​based on a pre-boost mapping model;

[0075] Figure 3 This is a schematic diagram of the functional module structure of the system in this application.

[0076] Reference numerals: 100, Data storage unit; 110, Model storage subunit; 111, Assist mapping model; 112, Safety threshold model; 113, Signal transfer function model; 114, Optimal mapping model; 115, Steering intention determination model; 116, Pre-assist mapping model; 120, Parameter data storage subunit; 200, Data acquisition unit; 300, Control mode selection unit; 310, Control loop switching subunit; 320, Optimal selection subunit; 400, Assist control unit; 500, Assist output unit; 600, Potential fault warning unit; 700, Fault warning unit; 800, Steering probability generation unit; 900, Pre-assist mapping model generation unit. Detailed Implementation

[0077] The embodiments of this application are described in detail below, and examples of the embodiments are shown in the accompanying drawings.

[0078] In the description of this specification, the references to "certain embodiments," "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples" refer to specific features, structures, materials, or characteristics described in connection with the described embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0079] A control method for a recirculating ball type electric power steering system, based on two independently configured control loops, such as... Figure 1 As shown, the main steps include the following:

[0080] S100, Construct and store an assist mapping model 111 to reflect the correspondence between the target assist current value and each influencing parameter or their combination;

[0081] S200, analyze and confirm the numerical range of specific influencing parameters or combinations thereof that do not affect driving safety after power assist failure, and store them as a safety threshold model 112.

[0082] S300, based on the control logic and control parameters of each control node in the control loop, constructs the signal transfer function model 113 of the control loop;

[0083] S400: Real-time monitoring and acquisition of the values ​​of each influencing parameter, and determination of whether the values ​​of each influencing parameter meet the numerical range limits of the aforementioned safety threshold model 112:

[0084] S410, if the constraints are met, then execute the single-control mode:

[0085] S4101, the first control loop confirms the target assist current value based on the assist mapping model 111 and the real-time acquired values ​​of various influencing parameters, and then outputs a corresponding size of drive current to the assist motor.

[0086] S4102, the second control loop acquires the values ​​of each influencing parameter and the feedback data signals of each control node in the first control loop in response to the above-mentioned influencing parameters. Based on the signal transfer function model 113, it acquires the deviation rate between the actual feedback signal and the theoretical response signal of each control node in the first control loop, and stores the values ​​of each influencing parameter and the control deviation rate corresponding to each control node in association.

[0087] If the S420 does not meet the requirements, it will execute the dual-control mode:

[0088] S4201, the first control loop and the second control loop acquire the values ​​of each influencing parameter and confirm the output of the first assist current value and the second assist current value according to the assist mapping model 111 respectively.

[0089] S4202, compare the difference between the first assist current value and the second assist current value:

[0090] If the above difference exceeds the set threshold, the smaller current value will be selected as the target assist current value and output to the assist motor.

[0091] If the above difference does not exceed the set threshold, then either the first assist current value or the second assist current value is selected as the target assist current value, or the average of the two is taken as the target assist current value.

[0092] The steps S100-S300 above are model building steps. In specific implementations, the steps can be executed in the above order, or one or more steps can be selectively executed according to actual needs.

[0093] The control nodes in step S300 include signal input / output nodes in the control loop and nodes that convert and process signals, such as torque sensors, signal filtering modules, and signal amplification modules in the control loop.

[0094] The deviation rate in step S4102 refers to the deviation between the actual feedback signal and the theoretical response signal of each control node. For example, if the theoretical response signal is 3.5V and the actual feedback signal is 2.5V, the deviation rate is 28.6%. The control deviation rate of each control node under the associated stored values ​​of each influencing parameter is the above-mentioned deviation rate.

[0095] In step S100, the influencing parameters include one or more combinations of vehicle state data, occupant state data, and environmental state data. Specifically, vehicle state data includes steering wheel torque magnitude and rate of change, steering wheel angle and rate of change, steering increment and steering accumulation, vehicle speed, and vehicle acceleration. Occupant state data includes driver head posture and steering wheel grip posture data. Environmental state data includes road conditions and route data, temperature, and wind speed data, etc.

[0096] In one embodiment, the power steering mapping model 111 is configured as a three-dimensional data table reflecting the correspondence between the basic target power steering current value and vehicle speed and steering wheel torque. To improve the accuracy of power steering, in this embodiment, the power steering mapping model 111 is configured as a multi-dimensional data table, which includes not only the correspondence between the target power steering current value and vehicle speed and steering wheel torque, but also the correspondence between it and influencing parameters such as steering wheel angular rate, torque change rate, steering accumulation, vehicle acceleration (including left and right lateral acceleration), and ambient wind speed. For example, based on the calculated steering wheel speed, an additional suppression current opposite to the direction of rotation is added to prevent the steering wheel from over-centering or becoming unstable at high speeds, thus improving stability. For example, in strong crosswind environments, more steering assistance is provided when turning into the wind based on the measured ambient wind speed. The above technical solution enables the vehicle's EPS to adjust the power steering current value not only according to vehicle status data, but also to revise the power steering magnitude based on factors such as the vehicle's environmental conditions, making the power steering magnitude more accurate.

[0097] In step S200 above, the safety threshold model 112 is also stored as a multi-dimensional data table. This multi-dimensional data table stores the numerical ranges of specific influencing parameters that do not affect driving safety. These specific influencing parameters mainly include vehicle speed, vehicle acceleration, steering wheel torque, and steering wheel angle. For example, when the vehicle speed is in the range of 0-5 km / h and the steering wheel torque is in the range of ±5 Nm, it is considered that even if the power steering fails, it will not affect driving safety. It should be noted that in practical applications, the basis for determining whether power steering failure affects driving safety is not based on the numerical range of a single specific influencing parameter, but rather on a comprehensive judgment of the numerical ranges of multiple specific influencing parameters. For example, when the vehicle speed exceeds 100 km / h, even if other specific influencing parameters are within safe ranges, it will still be judged that power steering failure will affect driving safety. The different combinations of the numerical ranges of the aforementioned specific influencing parameters form the safety threshold model 112.

[0098] In step S300, the signal transfer function model 113 is constructed based on the control circuit or logic program of the control loop. For example, the torque signal detected by the torque sensor will be amplified by an amplifier circuit and output to the ECU. When the output signal value of the torque sensor is obtained, the magnitude of the output signal value of the amplifier circuit can be calculated according to the amplification factor of the amplifier circuit. Thus, based on the control logic and control parameters of each control node in the control loop, the signal transfer function model 113 of the control loop can be constructed. When the signal input to the control loop (such as the torque signal output by the torque sensor) is known, the theoretical response signal of each control node in the control loop can be known based on the above signal transfer function model 113.

[0099] In this embodiment of the application, the control method further includes:

[0100] S4301, Statistically calculate the percentage of times the first control loop and the second control loop output the target assist current value and obtain the control deviation rate, respectively. For example, in 10 minutes of driving record data, the vehicle performed steering assist control a total of 20 times in single-control mode, of which the first control loop output the target assist current value 10 times, and the second control loop output the target assist current value the remaining 10 times.

[0101] S4302 automatically swaps the execution actions of the first and second control loops based on a set period. For example, after the first control loop completes the acquisition and output of the target assist current value twice, the system automatically switches to the second control loop to perform the acquisition and output of the assist current value. This periodic switching method can reduce the probability of a decrease in control accuracy due to prolonged high-load operation of the control loop.

[0102] S4303, associated storage of the control deviation rate corresponding to each control node in the first and second control loops under the numerical conditions of each influencing parameter during each turn.

[0103] S4304: The proportion of times the control deviation rate corresponding to each control node in the first and second control loops does not exceed a first threshold is statistically analyzed and defined as the control stability rate. If the control stability rate exceeds a set value, a first warning message is output. For example, if the first threshold is set to 10%, and if two out of ten actual feedback signals from a certain control node exceed the theoretical response signal by more than 10%, the control stability rate is 80%, meaning the control stability coefficient of that control node under the current influencing parameter values ​​is 0.8. The first warning message is output by the ECU to the vehicle-to-everything (V2X) system to alert the driver to potential faults in the electric power steering (EPS) system.

[0104] The above technical solution automatically switches the functions performed by the first and second control loops without affecting driving safety. This allows for the statistical analysis of the control deviation rate of each control node in the two control loops under different influencing parameters. In practical applications, if the control deviation rate of a certain control node deviates from the normal range too frequently, it indicates a potential fault. Therefore, a first warning message is output to promptly warn of potential faults and ensure the accuracy of the power steering adjustment.

[0105] In this embodiment of the application, the single-control mode further includes:

[0106] S4103, determine whether the control deviation rate corresponding to each control node in the first control loop and the second control loop exceeds the second threshold; if it exceeds the second threshold, then:

[0107] The control node and its control loop are marked as suspected fault nodes and suspected fault loops, and a second alarm message is output. Non-faulty loops are selected to obtain the target assist current value.

[0108] The aforementioned second threshold is a deviation amplitude value. If the control deviation rate of a certain control node in a certain control loop is too large, it indicates that there is a suspected fault. Therefore, a second alarm message is output. At the same time, in the single control mode, another control loop is selected as the loop for outputting the target assist current value to ensure the accuracy of the output result.

[0109] Typically, the two control loops in an automotive electric power steering system are configured as two independent hardware circuits. Due to differences in the manufacturing and soldering processes of the circuit components, these different hardware circuits have varying probabilities of being affected by environmental factors after a period of use. For example, if the solder joints of components on the circuit board of the first control loop are loose, the control stability of the first control loop will significantly decrease on bumpy roads (the impact of this defect is less noticeable on smooth roads because the solder joints remain in contact with the pads). To address this issue, in the embodiments of this application, the single-control mode further includes:

[0110] S4104, based on the pre-stored control stability rates of each control node in the first and second control loops under different influence parameter values, constructs and stores an optimal mapping model 114 to reflect the correspondence between the control stability of the first and second control loops and the values ​​of each influence parameter or their combination. Based on the real-time acquired influence parameter data and according to the optimal mapping model 114, the control loop with the higher control stability rate under the current influence parameter values ​​is selected to acquire and output the target assist current value.

[0111] The aforementioned optimal mapping model 114 is configured as a multi-dimensional data table to store which influencing parameter values ​​or combinations thereof prefer to use the first control loop or the second control loop, thereby improving control accuracy. Based on the above technical solution, in single control mode, the system can select the control loop with higher control stability based on the different values ​​of each influencing parameter to output the target assist current value, which helps to improve the accuracy of steering assist control.

[0112] In this embodiment, because influencing parameters such as environmental state data are introduced as the basis for determining the target assist current value, the assist mapping model 111 contains a large number of data relationships. In order to shorten the electric assist response time, in this embodiment, before outputting the target assist current value, such as... Figure 2 As shown, the control method further includes:

[0113] S500 acquires and associates the data of the influencing parameters corresponding to each steering of the vehicle, that is, the data of each influencing parameter collected when the steering wheel torque is greater than the set value.

[0114] S510: Based on correlation analysis, obtain the influencing parameters closely related to the vehicle's steering action, store them as steering prediction parameters, and construct a steering intention determination model 115 based on the aforementioned steering prediction parameters. In practical applications, for example, if the driver's head turns to the left or right at a set angle and the vehicle acceleration and road conditions satisfy a specific relationship, it indicates that the driver is preparing to turn.

[0115] S520, based on the real-time acquired steering prediction parameters and the steering intention determination model 115, a steering probability of the vehicle turning within a future set time period is generated, and the above steering probability is compared with a steering determination threshold:

[0116] If the aforementioned steering probability exceeds the steering determination threshold, then based on the current values ​​of each influencing parameter and their rate of change, the numerical range of each influencing parameter in the future set time period is calculated. Based on the aforementioned numerical range, the corresponding target assist current value is found in the self-assistance mapping model 111, and combined with the values ​​of each influencing parameter to form the target assist current prediction range, which is temporarily associated and stored as the pre-assistance mapping model 116. The core of the aforementioned pre-assistance mapping model 116 is a series of data correspondences, but its number is significantly reduced compared to the assist mapping model 111.

[0117] S530, in the single control mode, the values ​​of each influencing parameter are acquired in real time and the corresponding target assist current value is found and output based on the above-mentioned pre-assist mapping model 116.

[0118] The above technical solution can predict the vehicle's steering needs in advance based on data such as the driver's own actions or changes in the vehicle's driving state. The power assist mapping model 111 can be simplified in advance based on the predicted influence parameter values ​​to make it more scenario-specific. For example, the data correspondence in the power assist mapping model 111 that matches the current road conditions can be directly retrieved to form a new mapping model. Later, when the steering wheel torque is detected to exceed the set value, the corresponding target power assist current value can be found more quickly and accurately in the simplified pre-power assist mapping model 116, shortening the power assist response time and improving the accuracy of electric power assist response.

[0119] To implement the aforementioned control method for a recirculating ball electric power steering system, this application also discloses a control system for a recirculating ball electric power steering system, such as... Figure 3 As shown, it mainly includes: a data storage unit 100, a data acquisition unit 200, a control mode selection unit 300, a power assist control unit 400, and a power assist output unit 500.

[0120] The data storage unit 100 includes a model storage subunit 110 and a parameter data storage subunit 120, which are respectively configured to store the power assist mapping model 111, the safety threshold model 112, the signal transfer function model 113, and the values ​​of each influencing parameter obtained in real time, as well as the control deviation rate corresponding to each control node in the control loop under the condition of each influencing parameter value. In practical applications, the above data storage unit 100 is configured as a dedicated vehicle-mounted storage chip.

[0121] The data acquisition unit 200 is configured to collect the influencing parameters, including vehicle status data, personnel status data, and environmental status data. In terms of hardware configuration, the data acquisition unit 200 varies depending on the influencing parameters to be collected. Steering wheel torque is collected by a torque sensor mounted on the steering column; vehicle status data can be directly obtained from the vehicle's infotainment system data port; personnel status data, such as driver head posture data, can be obtained by an image acquisition device located in the driver's cab combined with image recognition software; and environmental status data is detected and acquired by various sensors mounted on the vehicle body, such as rain / fog sensors and lidar.

[0122] The control mode selection unit 300 is configured to obtain the values ​​of each influencing parameter based on real-time monitoring, determine whether the values ​​of each influencing parameter meet the numerical range limit of the above-mentioned safety threshold model 112, and determine whether the control mode is a single control mode or a dual control mode based on the determination result.

[0123] The power assist control unit 400 is data-connected to the control mode selection unit 300, and includes a first control loop and a second control loop. Based on the output of the control mode selection unit 300, it performs the following actions:

[0124] a. Based on the aforementioned assist mapping model 111 and combined with the real-time acquired values ​​of various influencing parameters, confirm the target assist current value; or

[0125] b. Obtain the values ​​of each influencing parameter and the feedback data signals of each control node in the first control loop in response to the above-mentioned influencing parameters. Based on the signal transfer function model 113, obtain the deviation rate between the actual feedback signal and the theoretical response signal of each control node in the first control loop, and store the values ​​of each influencing parameter and the control deviation rate corresponding to each control node in association.

[0126] The assist output unit 500 is data-connected to the control mode selection unit 300. When the control mode is single control mode, it directly outputs the target assist current value obtained from any one control loop. When the control mode is dual control mode, it compares the difference between the first assist current value and the second assist current value output by the first control loop and the second control loop, respectively. If the difference exceeds a set threshold, the smaller current value is selected as the target assist current value and output. If the difference does not exceed the set threshold, either the first assist current value or the second assist current value is selected as the target assist current value, or the average of the two is taken as the target assist current value.

[0127] To ensure the control accuracy of the two control loops, the optimized system further includes a potential fault early warning unit 600 and a fault alarm unit 700. The potential fault early warning unit 600 is configured to statistically analyze the proportion of times the control deviation rate corresponding to each control node in the first and second control loops does not exceed a first threshold, defining and storing this as a control stability rate. If the control stability rate exceeds a set value, a first alarm message is output. The fault alarm unit 700 is configured to determine whether the control deviation rate corresponding to each control node in the first and second control loops exceeds a second threshold. If it exceeds the second threshold, the control node and its corresponding control loop are marked as a suspected fault node and a suspected fault loop, and a second alarm message is output.

[0128] It should be noted that the aforementioned control mode selection unit 300, power assist control unit 400, and power assist output unit 500 are all stored in the logic processing chip of the electronic control unit in the form of program modules.

[0129] In this embodiment of the application, the model storage subunit 110 also stores the optimal mapping model 114 and the turning intention determination model 115.

[0130] The control mode selection unit 300 includes a control loop switching subunit 310 and an optimal selection subunit 320. The control loop switching subunit 310 is configured to statistically analyze the percentage of times the first and second control loops output the target assist current value and acquire the control deviation rate in single-control mode, and automatically switch the execution actions of the first and second control loops based on a set period. The optimal selection subunit 320 is configured to select the control loop with higher control stability under the current influence parameter values, based on the real-time acquired influence parameter data and the optimal mapping model 114, to acquire and output the target assist current value.

[0131] Based on the steering intention determination model 115 described above, the recirculating ball electric power steering control system disclosed in this application embodiment also includes a steering probability generation unit 800 and a pre-assist mapping model 116 generation unit.

[0132] The steering probability generation unit 800 is configured to generate a steering probability for the vehicle to turn within a future set time period based on the real-time acquired steering prediction parameters and the steering intention determination model 115. The pre-assist mapping model 116 generation unit is configured to receive and compare the steering probability with a steering determination threshold. If the steering probability exceeds the steering determination threshold, it calculates the numerical range of each influencing parameter in the future set time period based on the current values ​​and rates of change of each influencing parameter. Based on this numerical range, it searches for the corresponding target assist current value in the pre-assist mapping model 111 to form a target assist current prediction range, which is temporarily associated and stored as the pre-assist mapping model 116. The aforementioned assist output unit 500 is data-connected to the pre-assist mapping model 116 generation unit. When the control mode is single-control mode, it acquires the values ​​of each influencing parameter in real time and searches for and outputs the corresponding target assist current value based on the pre-assist mapping model 116.

[0133] The configuration of the above system functional modules can predict the vehicle's steering probability based on the driver's actions or other influencing parameters, and optimize the power assist mapping model 111 in advance based on the prediction results to improve the system's power assist response speed when steering occurs.

[0134] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A control method for a recirculating ball type electric power steering system, based on two independently configured control loops, characterized in that, include: Construct and store an assist mapping model to reflect the correspondence between the target assist current value and each influencing parameter or their combination (111); The numerical ranges corresponding to specific impact parameters or combinations thereof that do not affect driving safety after power assist failure are analyzed and stored as a safety threshold model (112). Based on the control logic and control parameters of each control node in the control loop, a signal transfer function model of the control loop is constructed (113); Real-time monitoring and acquisition of the values ​​of each influencing parameter, and determination of whether the values ​​of each influencing parameter meet the numerical range limits of the above-mentioned safety threshold model (112): If the constraints are met, then single-control mode will be executed: The first control loop outputs the target assist current value after confirming it based on the assist mapping model (111) and the real-time acquired values ​​of various influencing parameters. The second control loop acquires the values ​​of each influencing parameter and the feedback data signals of each control node in the first control loop in response to the above influencing parameters. Based on the signal transfer function model (113), it acquires the deviation rate between the actual feedback signal and the theoretical response signal of each control node in the first control loop, and stores the values ​​of each influencing parameter and the control deviation rate corresponding to each control node in association. If the constraints are not met, then dual-control mode will be executed: The first control loop and the second control loop acquire the values ​​of each influencing parameter and, according to the assist mapping model (111), respectively confirm the output of the first assist current value and the second assist current value; Compare the difference between the first assist current value and the second assist current value. If the difference exceeds a set threshold, select the smaller current value as the target assist current value and output it to the assist motor. If the difference does not exceed the set threshold, select either the first assist current value or the second assist current value as the target assist current value or take the average of the two as the target assist current value. The influencing parameters include one or more combinations of vehicle status data, personnel status data, and environmental status data.

2. The control method for a recirculating ball type electric power steering system according to claim 1, characterized in that, The vehicle status data includes steering wheel torque magnitude and rate of change, steering wheel angle and angular rate, steering increment and steering accumulation, vehicle speed and vehicle acceleration. Personnel status data includes driver head posture and steering wheel grip posture data; Environmental condition data includes road and route data, temperature, and wind speed data.

3. The control method for a recirculating ball type electric power steering system according to claim 1, characterized in that, The control method further includes: Acquire and associate the impact parameter data corresponding to each turn of the vehicle; Based on the correlation analysis method, the influence parameters related to vehicle steering action are obtained and stored as steering prediction parameters. Then, a steering intention determination model is constructed based on the above steering prediction parameters (115). Based on the real-time acquired steering prediction parameters and the steering intention determination model (115), a steering probability of the vehicle turning within a set future time period is generated, and the above steering probability is compared with a steering determination threshold: If the above-mentioned steering probability exceeds the steering judgment threshold, then based on the current values ​​of each influencing parameter and their rate of change, the numerical range of each influencing parameter in the future set period is calculated, and the corresponding target assist current value is found in the self-assistance mapping model (111) based on the above-mentioned numerical range to form the target assist current prediction range, and temporarily associated and stored as the pre-assistance mapping model (116). In the single-control mode, the values ​​of each influencing parameter are acquired in real time, and the corresponding target assist current value is found and output based on the above pre-assist mapping model (116).

4. The control method for a recirculating ball type electric power steering system according to claim 2, characterized in that, The control method further includes: The percentage of times the first control loop and the second control loop output the target assist current value and obtain the control deviation rate were statistically analyzed. The execution actions of the first and second control loops are automatically swapped based on a set period. The control deviation rate of each control node in the first and second control loops is associated and stored under the conditions of each influencing parameter value during each turn. The proportion of times the control deviation rate corresponding to each control node in the first and second control loops does not exceed the first threshold is defined and stored as the control stability rate. If the above control stability rate exceeds the set value, the first alarm message will be output.

5. The control method for a recirculating ball type electric power steering system according to claim 4, characterized in that, The single-control mode also includes: Determine whether the control deviation rate corresponding to each control node in the first and second control loops exceeds the second threshold. If it exceeds the second threshold, then: Mark the control node and its corresponding control loop as a suspected fault node and suspected fault loop, and output a second alarm message; A non-faulty circuit is selected to obtain the target boost current value.

6. The control method for a recirculating ball type electric power steering system according to claim 5, characterized in that, The single-control mode also includes: Based on the control stability rates of each control node in the first and second control loops under different influence parameter values, a preferred mapping model (114) is constructed and stored to reflect the correspondence between the control stability of the first and second control loops and the values ​​of each influence parameter or their combination. Based on the real-time acquired influence parameter data and the optimal mapping model (114), a control loop with a higher control stability under the current influence parameter value is selected to acquire and output the target assist current value.

7. A recirculating ball type electric power steering control system, characterized in that, The method for controlling a recirculating ball-type electric power steering system as described in any one of claims 1-6 includes: The data storage unit (100) includes a model storage subunit (110) and a parameter data storage subunit (120), which are respectively configured to store the assist mapping model (111), the safety threshold model (112), the signal transfer function model (113), and the values ​​of each influencing parameter obtained by real-time monitoring, and the control deviation rate corresponding to each control node in the control loop under the condition of each influencing parameter value; The data acquisition unit (200) is configured to collect the influencing parameters, including vehicle status data, personnel status data and environmental status data; The control mode selection unit (300) is configured to obtain the values ​​of each influencing parameter based on real-time monitoring, determine whether the values ​​of each influencing parameter meet the numerical range limit of the above-mentioned safety threshold model (112), and determine whether the control mode is a single control mode or a dual control mode based on the determination result. The power assist control unit (400), including a first control loop and a second control loop, performs the following actions based on the output of the control mode selection unit (300): Based on the aforementioned assist mapping model (111) and combined with the real-time acquired values ​​of various influencing parameters, the target assist current value is confirmed; or The values ​​of each influencing parameter and the feedback data signals of each control node in the first control loop in response to the above influencing parameters are obtained. Based on the signal transfer function model (113), the deviation rate between the actual feedback signal and the theoretical response signal of each control node in the first control loop is obtained. The values ​​of each influencing parameter and the control deviation rate corresponding to each control node are associated and stored. The assist output unit (500) is connected to the control mode selection unit (300) for data connection. When the control mode is single control mode, it directly outputs the target assist current value. When the control mode is dual control mode, the difference between the first assist current value and the second assist current value output by the first control loop and the second control loop is compared. If the difference exceeds the set threshold, the smaller current value is selected as the target assist current value and output. If the difference does not exceed the set threshold, either the first assist current value or the second assist current value is selected as the target assist current value or the average of the two is taken as the target assist current value.

8. The recirculating ball type electric power steering control system according to claim 7, characterized in that, The system also includes: The potential fault warning unit (600) is configured to count the proportion of times the control deviation rate corresponding to each control node in the first control loop and the second control loop does not exceed the first threshold, define and store it as the control stability rate, and output the first alarm information if the control stability rate exceeds the set value. The fault alarm unit (700) is configured to determine whether the control deviation rate corresponding to each control node in the first control loop and the second control loop exceeds the second threshold. If it exceeds the second threshold, the control node and its control loop are marked as suspected fault nodes and suspected fault loops, and the second alarm information is output.

9. The recirculating ball type electric power steering control system according to claim 7, characterized in that, The model storage subunit (110) also stores the optimal mapping model (114); The control mode selection unit (300) includes: The control loop switching subunit (310) is configured to statistically analyze the percentage of times the first control loop and the second control loop output the target assist current value and obtain the control deviation rate in the single control mode, and automatically switch the execution actions of the first control loop and the second control loop based on a set period. The optimal selection subunit (320) is configured to select a control loop with a higher control stability under the current influence parameter value condition based on the real-time acquired influence parameter data and the optimal mapping model (114) to acquire and output the target assist current value.

10. The recirculating ball type electric power steering control system according to claim 7, characterized in that, The model storage subunit (110) also stores a steering intention determination model (115); The system also includes: The steering probability generation unit (800) is configured to generate the steering probability of the vehicle turning in a future set time period based on the steering prediction parameters acquired in real time and the steering intention determination model (115). The pre-assist mapping model (116) generation unit is configured to receive and compare the above steering probability with a steering judgment threshold: if the above steering probability exceeds the steering judgment threshold, then calculate the value range of each influencing parameter in the future set time period based on the current value of each influencing parameter and its rate of change, and find the corresponding target assist current value in the self-assist mapping model (111) based on the above value range to form the target assist current prediction range, and temporarily associate and store it as the pre-assist mapping model (116); The assist output unit (500) is connected to the pre-assist mapping model (116) generation unit. When the control mode is single control mode, the values ​​of each influencing parameter are obtained in real time and the target assist current value corresponding to the above pre-assist mapping model (116) is found and output.

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