Electric power steering system and deviation compensation method thereof

Abstract

The present invention relates to the field of automotive control. An embodiment thereof provides a method for compensating for vehicle deviation in an electric power steering system, comprising: determining a pseudo-compensation current for a power steering motor based on a desired rack force; and correcting the pseudo-compensation current to obtain an actual compensation current, wherein the correction is related to a historical sequence of the actual compensation current. Also provided are an electric power steering system and a vehicle incorporating the same. The embodiments provided by the present invention enhance the applicability of electric power steering systems and the driver's driving experience.

Description

Technical Field

[0001] The present invention relates to the field of automobile control, and in particular to a deviation compensation method of an electric power steering system, an electric power steering system, and a vehicle comprising the electric power steering system. Background Art

[0002] When the vehicle is traveling straight, the driver applies a certain amount of force to keep it within its lane. However, if the vehicle deviates due to inherent factors (such as suspension misalignment or wheel alignment) or natural factors (such as crosswinds or sloping roads), the driver must exert a relatively large amount of force to maintain the vehicle's straight course. In these situations, the EPS provides a corresponding compensating torque to reduce driver fatigue and alleviate manual effort.

[0003] Currently, the identification of straight-line deviation conditions is complex. If yaw rate and lateral acceleration signals are used, some vehicles lack corresponding signals on the bus. Furthermore, adding sensors or controllers related to yaw rate and lateral acceleration signals would increase vehicle costs. Currently, the driver feels a noticeable and strong sensation when the PDC (Pedal Deviation Compensation) function is engaged and disengaged. The PDC compensation torque is sluggish and lacks real-time compensation. The PDC compensation current is not adjustable, making it difficult to match specific vehicles. Excessive PDC compensation torque affects driving safety. Currently, the PDC compensation current can be updated in real time within an IG cycle, and the last learned value can be memorized after disengaging compensation. However, the PDC compensation current is reset to zero after power is removed. This causes the PDC compensation torque to change from zero in the next IG cycle, resulting in delayed PDC compensation.

[0004] EWMA: Exponentially Weighted Moving-Average, exponentially weighted moving average.

[0005] ESP: Electric Power Steering, electric power steering system. Summary of the Invention

[0006] In view of this, the present invention aims to provide an electric power steering system and a deviation compensation method thereof, so as to at least partially solve the above problems.

[0007] In a first aspect of the present invention, a method for compensating for deviation of an electric power steering system is provided, comprising determining a pseudo-compensation current of a power steering motor based on a rack force to be compensated, the method further comprising:

[0008] The actual compensation current is obtained by correcting the simulated compensation current, and the correction is related to the historical sequence of the actual compensation current.

[0009] Preferably, determining the quasi-compensation current of the power assist motor based on the rack force to be compensated includes:

[0010] The rack force estimation module uses the driver's hand force signal and the power steering signal of the electric power steering system as input to estimate the rack force required for the vehicle to move straight;

[0011] The rack force required for the vehicle to move straight is used as input, and the pseudo-compensation current of the power assist motor required for the vehicle to move straight is calculated based on the conversion correspondence between the rack force and the current.

[0012] Preferably, the correcting the proposed compensation current to obtain the actual compensation current includes:

[0013] The proposed compensation current and the N historical actual compensation currents in the selected historical sequence are assigned corresponding weight values; and a weighted sum of the proposed compensation current and the N historical actual compensation currents based on the corresponding weight values ​​is used as the actual compensation current.

[0014] Preferably, the weight value is updated within each determination period of the actual compensation current.

[0015] Preferably, N=1, the historical actual compensation current is the actual compensation current at the moment before the determination moment of the intended compensation current, and the difference between the determination moment and the previous moment depends on the determination period of the actual compensation current; the sum of the weight values ​​is 1, and the value range of the weight value of the intended compensation current is [0, 1].

[0016] Preferably, the step of correcting the proposed compensation current to obtain the actual compensation current further includes:

[0017] Determining whether an actual compensation current obtained by weighted summation is greater than a preset maximum threshold value of the actual compensation current;

[0018] The preset maximum threshold is used as the actual compensation current.

[0019] Preferably, the step of correcting the proposed compensation current to obtain the actual compensation current further includes:

[0020] Determining that the actual compensation current obtained by weighted summation is not greater than a preset maximum value of the actual compensation current;

[0021] Determining whether a change slope of the actual compensation current obtained by the weighted sum and the actual compensation current at the previous moment is greater than a preset maximum slope threshold;

[0022] The actual compensation current is determined based on the actual compensation current at the previous moment and the preset maximum slope threshold.

[0023] Preferably, the method further includes: storing the actual compensation current when the KL15 power supply is powered off; the stored actual compensation current will be read out as the initial value of the actual compensation current when the KL15 power supply is powered on next time and the deviation compensation is in an activated state.

[0024] In the third aspect of the present invention, an electric power steering system is also provided, including: a current calculation module, used to determine the quasi-compensation current of the power steering motor based on the rack force to be compensated; and a current correction module, used to correct the quasi-compensation current to obtain the actual compensation current, and the correction is related to the historical sequence of the actual compensation current.

[0025] Preferably, the current correction module includes: an EWMA current determination submodule, which is used to obtain an EWMA compensation current calculation value based on the EWMA model by using the input simulated compensation current and the N historical actual compensation currents in the selected historical sequence; and a current limiting submodule, which is used to limit the maximum value and / or change slope of the EWMA compensation current calculation value.

[0026] In a third aspect of the present invention, a vehicle is further provided, comprising the aforementioned electric power steering system.

[0027] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, wherein instructions are stored in the storage medium. When the instructions are executed on a computer, the computer executes the aforementioned deviation compensation method for the electric power steering system.

[0028] The technical solution provided by the present invention has the following beneficial effects: improving the applicability of EPS products and the driving experience of drivers.

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 1 is a flow chart of a method for compensating for deviation of an electric power steering system provided by one embodiment of the present invention;

[0032] Figure 2 Schematic diagram of the relationship between input and output based on the EWMA algorithm provided by one embodiment of the present invention;

[0033] Figure 3This is a schematic diagram of the current magnitude after limiting correction based on the actual compensation current provided by an embodiment of the present invention;

[0034] Figure 4 This is a control strategy diagram of a deviation compensation method for an electric power steering system provided by one embodiment of the present invention;

[0035] Figure 5 This is a flowchart of an implementation method of a deviation compensation method for an electric power steering system provided by one embodiment of the present invention;

[0036] Figure 6 It is a structural schematic diagram of functional modules in an electric power steering system provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0038] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0039] Figure 1 FIG. 1 is a flow chart of a method for compensating a deviation of an electric power steering system provided by an embodiment of the present invention. Figure 1 A method for compensating deviation of an electric power steering system, comprising:

[0040] S1, determines the quasi-compensation current of the power-assisted motor based on the rack force that needs to be compensated; during the operation of the electric power steering system, it is necessary to determine whether the vehicle is in a straight-ahead deviation state through the hand force signal, the steering wheel angle signal, and the vehicle speed signal. When the vehicle is in a straight-ahead deviation state, the PDC (deviation compensation) function is activated. At this time, a deviation compensation current will be generated according to the current driving conditions, and superimposed with the basic power-assisted current to obtain the final EPS motor power-assisted current, and then the power-assisted motor is driven by the driving circuit to achieve compensation for the rack force of the basic steering system, thereby realizing the deviation compensation function. However, the deviation compensation achieved by this step has many problems mentioned in the background technology.

[0041] S2, correcting the proposed compensation current to obtain an actual compensation current, wherein the correction is related to a historical sequence of the actual compensation current.

[0042] This step corrects the quasi-compensation current obtained in step S1 by using the historical sequence of the actual compensation current. This correction method mainly filters, smoothes, limits or calculates the quasi-compensation current so that the compensation current acting on the motor overcomes the aforementioned defects.

[0043] Through the above implementation, various problems of deviation compensation in the prior art can be solved, and various problems such as excessive or large changes or uneven actual compensation current in deviation compensation can be avoided.

[0044] In one embodiment of the present invention, the pseudo-compensation current of the power-assist motor is determined based on the rack force required for compensation, including: using the driver's hand force signal and the power-assist signal of the electric power steering system as input, estimating the rack force required for the vehicle to go straight through a rack force estimation module; using the rack force required for the vehicle to go straight as input, calculating the pseudo-compensation current of the power-assist motor required when the vehicle goes straight through the corresponding relationship between the rack force and the current. Through this embodiment, it is possible to use the hand force signal, the steering wheel angle signal, and the vehicle speed signal to identify the problem of the vehicle going straight, and use the method of estimating the rack force to estimate the rack force required for the vehicle to go straight; using the rack force required for going straight, calculate the compensation current corresponding to the power assistance that the motor needs to provide when the vehicle goes straight. The rack force estimation module and the corresponding relationship between the rack force and the current can be obtained based on existing technologies and will not be described in detail here.

[0045] In one embodiment of the present invention, the actual compensation current is obtained after the proposed compensation current is corrected, including: assigning corresponding weight values ​​to the proposed compensation current and the N historical actual compensation currents in the selected historical sequence; and taking the weighted sum of the proposed compensation current and the N historical actual compensation currents based on the corresponding weight values ​​as the actual compensation current. The weight set for the proposed compensation current is a0, and the weights of the N historical actual compensation currents are set to a1 to a2, respectively. n , after weighted summation of the proposed compensation current and N historical actual compensation currents, the calculated result is used as the actual compensation current. n Equal weight values ​​can make the calculated actual compensation current smooth and without hysteresis.

[0046] In one embodiment of the present invention, the weight value is updated within each determination period of the actual compensation current. In this embodiment, the following steps are used to update the weight value a. For a system with a fixed time step T between sample values, that is, the determination period of the actual compensation current is T. a is calculated and stored by the following steps: a = exp(-T / τ). In the formula, τ can be called a learning constant, which has the same time unit as T. Through the above determination method, the weight value a can be updated. And by changing the learning constant, the deviation compensation method can be adapted to different vehicle conditions.

[0047] In one embodiment of the present invention, N = 1, the historical actual compensation current is the actual compensation current at the moment before the determination of the proposed compensation current, and the difference between the determination moment and the previous moment depends on the determination period of the actual compensation current. The sum of the weight values ​​is 1, and the weight values ​​of the proposed compensation currents range from [0, 1]. In this embodiment, the EWMA algorithm is preferably used to achieve real-time calculation of the deviation compensation current.

[0048] The EWMA algorithm formula is as follows: y(t) = a*x(t) + (1-a)*y(t-1);

[0049] Where y(t) is the output, defined as the PDC compensation current required to maintain the vehicle's straight-line motion at time t; x(t) is the input, or the simulated compensation current, defined as the motor-assisted current required for the vehicle to maintain straight-line motion at time t; y(t-1) is the actual compensation current at the previous moment; and a and 1-a are both weights. Figure 2 This is a schematic diagram of the relationship between input and output based on the EWMA algorithm provided by one embodiment of the present invention, such as Figure 2 As shown, when the intended compensation current is maintained near 1.4A rms (ampere effective value), the actual compensation current corrected by this embodiment does not surge to 1.4A rms. Instead, it increases smoothly to 1.4A rms and ultimately matches the intended compensation current. This embodiment uses only one filter to smooth the compensation current, which has the advantages of simple calculation and good real-time performance.

[0050] In one embodiment of the present invention, the method of modifying the simulated compensation current to obtain the actual compensation current further includes: determining whether the actual compensation current obtained by weighted summation is greater than a preset maximum threshold of the actual compensation current; and using the preset maximum threshold as the actual compensation current. This embodiment limits the maximum value of the actual PDC compensation current, preventing uncontrollable PDC compensation torque and any threat to driver safety, thereby achieving a safe design for the deviation compensation function.

[0051] In one embodiment of the present invention, the actual compensation current obtained after modifying the simulated compensation current further includes: determining that the actual compensation current obtained by weighted summation is not greater than a preset maximum value of the actual compensation current; determining that the slope of change between the actual compensation current obtained by weighted summation and the actual compensation current at the previous moment is greater than a preset maximum slope threshold; and determining the actual compensation current based on the actual compensation current at the previous moment and the preset maximum slope threshold. The PDC current change limiting module in this embodiment limits the change in the actual compensation current of the PDC to a certain range, preventing sudden changes in the current and avoiding discomfort to the driver when entering and exiting the PDC function. Figure 3This is a schematic diagram of the current magnitude after limiting correction based on the actual compensation current provided by an embodiment of the present invention, such as Figure 3 As shown, the magnitude of the corrected actual compensation current is limited to the range of -6A rms to +6A rms, and its change slope is also within a certain range, thereby preventing sudden changes in the compensation current.

[0052] In one embodiment of the present invention, the method further includes storing the actual compensation current when the KL15 power supply is powered off; the stored actual compensation current is read out as the initial value of the actual compensation current when the KL15 power supply is next powered on and the runout compensation function is activated. This embodiment stores the current actual compensation current value of the PDC in a non-volatile storage device after the KL15 power supply is powered off. This allows the actual compensation current value of the PDC before the KL15 power supply is powered off to be directly used for continued calculation when the KL15 power supply is powered on again and the PDC function is activated, thereby providing the PDC compensation current in a timely manner. Figure 4 FIG. 1 is a control strategy diagram of a deviation compensation method for an electric power steering system provided by an embodiment of the present invention, such as Figure 4 As shown, after it is determined that KL15 is powered off, the value of the PDC compensation current is stored in a non-volatile storage device.

[0053] In order to facilitate understanding and implementation by those skilled in the art, the implementation process of the method is illustrated with the help of the accompanying drawings. Figure 5 FIG. 1 is a flowchart of an implementation method of an electric power steering system deviation compensation method provided by an embodiment of the present invention, as shown in FIG. Figure 5 As shown, the specific implementation steps are as follows:

[0054] ① Using the driver's hand force signal and the EPS motor assist signal as input, the rack force estimation module estimates the rack force required for the vehicle to move straight.

[0055] ② Using the rack force when the vehicle is moving straight as input, the rack force to current conversion module calculates the assist current required by the EPS motor when the vehicle is moving straight;

[0056] ③ Using the assist current provided by the EPS motor when the vehicle is traveling straight as input, the PDC compensation current, y(t), is calculated by the PDC-EWMA current calculation module.

[0057] ④ Using the calculated PDC compensation current as input, the final PDC current (Iq*) is obtained through the PDC current limiting module;

[0058] ⑤ Using the PDC current (Iq*) as input, the EPS assist current calculation module adds the final PDC current to the total motor assist current (Iq).

[0059] Figure 6 FIG. 1 is a schematic diagram of a structure of a functional module in an electric power steering system provided by an embodiment of the present invention. Figure 6 In one embodiment of the present invention, an electric power steering system is further provided, comprising: a current calculation module for determining a pseudo-compensation current of a power steering motor based on a rack force to be compensated; and a current correction module for correcting the pseudo-compensation current to obtain an actual compensation current, wherein the correction is related to a historical sequence of the actual compensation current.

[0060] In one embodiment of the present invention, the current correction module includes: an EWMA current determination submodule, which is used to obtain an EWMA compensation current calculation value based on the EWMA model by using the input simulated compensation current and N historical actual compensation currents in the selected historical sequence; and a current limiting submodule, which is used to limit the maximum value and / or change slope of the EWMA compensation current calculation value.

[0061] The specific definitions of the various functional modules in the aforementioned electric power steering system can be found in the aforementioned definitions of the deviation compensation method for the electric power steering system and will not be repeated here. Each module in the aforementioned device can be implemented in whole or in part via software, hardware, or a combination thereof. Each of the aforementioned modules can be embedded in or independent of a processor in a computer device in hardware form, or stored in a computer device memory in software form, so that the processor can call and execute the corresponding operations of each module.

[0062] In an embodiment provided by the present invention, a deviation compensation device for an electric power steering system is also provided, comprising: at least one processor; a memory connected to the at least one processor; wherein the memory stores instructions that can be executed by the at least one processor, and the at least one processor implements the following steps by executing the instructions stored in the memory: determining the quasi-compensation current of the power-assist motor based on the rack force to be compensated, and correcting the quasi-compensation current to obtain an actual compensation current, wherein the correction is related to the historical sequence of the actual compensation current.

[0063] The control module or processor herein has the functions of numerical calculation and logical operation, and at least has a central processing unit (CPU) with data processing capabilities, random access memory (RAM), read-only memory (ROM), multiple I / O ports, and an interrupt system. The control module or control device herein can be, for example, a single-chip microcomputer, chip, PLC, or processor, and other commonly used hardware.

[0064] The deviation compensation device can be a standalone piece of hardware, with multiple pins connected to various intelligent driving systems. It receives torque compensation signals from these systems and, through an internal correction mechanism, outputs the actual compensation current. Alternatively, the deviation compensation device can be an ECU within an existing electric power steering system, with the deviation compensation function implemented as a subfunction of that ECU. The device takes the form of a piece of software code within the hardware operating environment of the existing ECU controller.

[0065] In one embodiment of the present invention, a vehicle is provided, comprising the aforementioned electric power steering system. The vehicle equipped with the aforementioned electric power steering system can effectively correct the vehicle's deviation compensation current, thereby improving the driver's driving experience.

[0066] In one embodiment of the present invention, a computer-readable storage medium is further provided. The storage medium stores instructions that, when executed on a computer, enable the computer to execute the aforementioned deviation compensation method for the electric power steering system.

[0067] The embodiments provided in the present invention are applicable to all types of EPS currently on the market, such as C-EPS, DP-EPS, P-EPS, R-EPS, etc., and achieve the following beneficial effects through the aforementioned different embodiments:

[0068] ① Use hand force signals, steering wheel angle signals, and vehicle speed signals to identify vehicle deviation from straight lines;

[0069] ② Use the rack force estimation method to estimate the rack force required for the vehicle to move straight; use the rack force required for straight movement to calculate the assist current that the motor needs to provide when the vehicle moves straight;

[0070] ③ Use EWMA algorithm to calculate PDC compensation current, PDC compensation is soft and has no hysteresis;

[0071] ④ Create a calibration module: Set the learning constant τ in the EWMA algorithm as the calibration value to adjust the speed of the deviation compensation current change to facilitate matching different vehicles;

[0072] ⑤ Create a calibration module: Set the limit value of the running deviation compensation current change slope and the maximum limit value of the running deviation compensation current as calibration values. This is used to adjust the rising and falling speeds of the running deviation compensation current and the maximum current that the running deviation compensation can provide.

[0073] ⑥ By limiting the maximum value of the PDC compensation current, it avoids the impact of excessive PDC compensation current on driving safety;

[0074] ⑦ By limiting the slope of the PDC compensation current, the driver is prevented from feeling uncomfortable when the PDC function enters and exits.

[0075] ⑧ The PDC compensation current is stored in NVM after KL15 is powered off, which solves the problem that the PDC compensation current is cleared after power off and cannot be provided in time after power is turned on and the PDC function is activated again.

[0076] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0077] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0078] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0079] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0080] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0081] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0082] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0083] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0084] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for compensating a deviation of an electric power steering system, comprising determining a pseudo-compensation current of a power steering motor based on a rack force to be compensated, characterized in that: The deviation compensation method further includes: Correcting the proposed compensation current to obtain an actual compensation current, wherein the correction is related to a historical sequence of the actual compensation current; The correcting the proposed compensation current to obtain the actual compensation current includes: Assigning corresponding weight values ​​to the proposed compensation current and the N historical actual compensation currents selected in the historical sequence; Taking a weighted sum of the proposed compensation current and the N historical actual compensation currents based on corresponding weight values ​​as the actual compensation current; N=1, the historical actual compensation current is the actual compensation current at the moment before the determination moment of the proposed compensation current, and the difference between the determination moment and the previous moment depends on the determination period of the actual compensation current; the sum of the weight values ​​is 1, and the weight value of the proposed compensation current is in the range of [0, 1]; The weight value is updated within each determination period of the actual compensation current, and a is calculated and stored by the following steps: a=exp(-T / τ), where a is the weight value, T is the determination period of the actual compensation current, and τ is a learning constant, which has the same time unit as T, and the learning constant τ is set to a calibration value.

2. The deviation compensation method according to claim 1, characterized in that: The quasi-compensation current of the power assist motor is determined based on the rack force to be compensated, including: The rack force estimation module uses the driver's hand force signal and the power steering signal of the electric power steering system as input to estimate the rack force required for the vehicle to move straight; The rack force required for the vehicle to move straight is used as input, and the pseudo-compensation current of the power assist motor required for the vehicle to move straight is calculated based on the conversion correspondence between the rack force and the current.

3. The deviation compensation method according to claim 1, characterized in that: The correcting the proposed compensation current to obtain the actual compensation current further includes: Determining whether an actual compensation current obtained by weighted summation is greater than a preset maximum threshold value of the actual compensation current; The preset maximum threshold is used as the actual compensation current.

4. The deviation compensation method according to claim 1, characterized in that: The correcting the proposed compensation current to obtain the actual compensation current further includes: Determining that an actual compensation current obtained by weighted summation is not greater than a preset maximum threshold value of the actual compensation current; Determining whether a change slope of the actual compensation current obtained by the weighted sum and the actual compensation current at the previous moment is greater than a preset maximum slope threshold; The actual compensation current is determined based on the actual compensation current at the previous moment and the preset maximum slope threshold.

5. The deviation compensation method according to any one of claims 1 to 4, characterized in that: The method further comprises: The actual compensation current when the KL15 power supply is powered off is stored; the stored actual compensation current will be read out as the initial value of the actual compensation current when the KL15 power supply is powered on next time and the deviation compensation is in an activated state.

6. An electric power steering system, characterized in that: include: A current calculation module, configured to determine a pseudo-compensation current of the power assist motor based on the rack force to be compensated; as well as a current correction module, configured to correct the proposed compensation current to obtain an actual compensation current, wherein the correction is related to a historical sequence of the actual compensation current; The correcting the proposed compensation current to obtain the actual compensation current includes: Assigning corresponding weight values ​​to the proposed compensation current and the N historical actual compensation currents selected in the historical sequence; Taking a weighted sum of the proposed compensation current and the N historical actual compensation currents based on corresponding weight values ​​as the actual compensation current; N=1, the historical actual compensation current is the actual compensation current at the moment before the determination moment of the proposed compensation current, and the difference between the determination moment and the previous moment depends on the determination period of the actual compensation current; the sum of the weight values ​​is 1, and the weight value of the proposed compensation current is in the range of [0, 1]; The weight value is updated within each determination period of the actual compensation current, and a is calculated and stored by the following steps: a=exp(-T / τ), where a is the weight value, T is the determination period of the actual compensation current, and τ is a learning constant, which has the same time unit as T, and the learning constant τ is set to a calibration value.

7. The electric power steering system according to claim 6, characterized in that: The current correction module includes: An EWMA current determination submodule is configured to obtain an EWMA compensation current calculation value based on an EWMA model by using the input proposed compensation current and the N historical actual compensation currents selected in the historical sequence; and The current limiting submodule is used to limit the maximum value and / or change slope of the EWMA compensation current calculation value.

8. A vehicle, characterized in that: The vehicle includes the electric power steering system according to claim 6 or 7.

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