Control system and method for a steering device for rear wheels of a vehicle

Abstract

The present application relates to a control system and method for a steering device of a rear wheel of a vehicle, the system comprising: a first magnet mounted to a steering application mechanism; a second magnet mounted to a rotor of a motor; a first magnetic sensor detecting a first magnetic field intensity of the first magnet and a change speed thereof to generate a first detection value of a linear displacement; a second magnetic sensor detecting a second magnetic field intensity of the second magnet and a change speed thereof to generate a detection value of a rotational displacement; and a control unit acquiring the first detection value of the linear displacement from the first magnetic sensor, acquiring the detection value of the rotational displacement from the second magnetic sensor, determining a second detection value of the linear displacement based on the detection value of the rotational displacement, determining an output value of the linear displacement based on the first detection value and the second detection value of the linear displacement to represent a steering angle of the rear wheel of the vehicle, and controlling an energization state of the rotor of the motor based on an offset distance of the output value of the linear displacement with respect to a reference zero position. The system and method of the present application are accurate and safe.

Description

Technical Field

[0001] This application relates to the technical field of steering mechanisms for the rear wheels of vehicles, and more specifically, to control systems and methods for steering mechanisms for the rear wheels of vehicles. Background Technology

[0002] With the development of modern vehicle technology and the improvement of road conditions, the requirements for vehicle comfort, handling, and safety are becoming increasingly higher. To improve vehicle cornering agility, straight-line stability, and comfort, rear-wheel steering technology has been applied to vehicles. In other words, by utilizing rear-wheel steering technology, when the vehicle is at low speed or understeer, the rear wheels rotate in the opposite direction to the front wheels to reduce the turning radius and improve vehicle agility. Conversely, when the vehicle is oversteering, especially at high speeds and prone to drifting, the rear wheels rotate in the same direction as the front wheels to facilitate smooth lane changes.

[0003] In existing technologies, rear-wheel steering technology is mainly achieved through a steering device for the rear wheels of a vehicle. This steering device mainly includes: a motor, which includes a rotor that can rotate at a torque applied speed when energized to perform rotational displacement; a steering application mechanism that can convert the rotational displacement of the rotor into linear displacement at a certain transmission ratio for steering the rear wheels of the vehicle; a motor position sensor that can generate a detection value of rotational displacement, and can calculate a detection value of linear displacement by multiplying the detection value of rotational displacement by the transmission ratio, which represents the steering angle of the rear wheels of the vehicle; and an ECU for RWS control, which can control the energization state of the rotor based on the detection value of linear displacement, i.e., control the motor assist.

[0004] However, by detecting the rotor's rotational displacement using a single motor position sensor, it is difficult to improve the detection accuracy near the zero point of the linear displacement of the steering mechanism, which corresponds to the initial state of the vehicle's rear wheels returning to center. This makes it difficult to reduce the error in each time the vehicle's rear wheels return to center. Moreover, if the motor position sensor malfunctions, the steering rear wheels will have difficulty returning to center, and the angled driving of the vehicle's rear wheels can easily lead to steering collision accidents. Summary of the Invention

[0005] One object of this application is to provide a control system and method for a steering device for the rear wheels of a vehicle, which can flexibly, accurately and safely achieve steering of the rear wheels of the vehicle.

[0006] According to one aspect of this application, a control system for a steering device for the rear wheels of a vehicle is provided, the steering device comprising: a motor rotor configured to perform rotational displacement in an energized state; and a steering application mechanism configured to convert the rotational displacement into linear displacement for steering the rear wheels of the vehicle; the control system comprising: a first magnet configured to be mounted to the steering application mechanism; a second magnet configured to be mounted to the motor rotor; a first magnetic sensor configured to detect a first magnetic field strength and its rate of change of the first magnet to generate a first detection value of the linear displacement; and a second magnetic sensor configured to... The system is configured to detect the strength of a second magnetic field of a second magnet and its rate of change to generate a detected value of the rotational displacement; and a control unit configured to: acquire a first detected value of the linear displacement from a first magnetic sensor; acquire the detected value of the rotational displacement from a second magnetic sensor and determine a second detected value of the linear displacement based on the detected value of the rotational displacement; determine an output value of the linear displacement based on the first and second detected values ​​of the linear displacement to represent the steering angle of the rear wheels of the vehicle; and control the energizing state of the motor rotor based on the offset distance of the output value of the linear displacement relative to a reference zero position.

[0007] Optionally, determining the output value of the linear displacement based on the first and second detection values ​​of the linear displacement includes: when the absolute value of the first detection value of the linear displacement is less than or equal to a first threshold, using the first detection value of the linear displacement as the output value of the linear displacement, and determining the first threshold based on the detection sensitivity of the first magnetic sensor.

[0008] Optionally, determining the output value of the linear displacement based on the first and second detection values ​​of the linear displacement further includes: when the absolute value of the first detection value of the linear displacement is greater than a first threshold and the absolute value of the second detection value of the linear displacement is greater than or equal to a second threshold, using the second detection value of the linear displacement as the output value of the linear displacement, and determining the second threshold based on the detection sensitivity of the first magnetic sensor and the detection sensitivity of the second magnetic sensor.

[0009] Optionally, determining the output value of the linear displacement based on the first and second detection values ​​of the linear displacement further includes: when the absolute value of the first detection value of the linear displacement is greater than a first threshold, the absolute value of the second detection value of the linear displacement is less than a second threshold, and the absolute value of the first detection value of the linear displacement is greater than the sum of the absolute value of the second detection value of the linear displacement and the tolerance, the second detection value of the linear displacement is used as the output value of the linear displacement, and the tolerance is determined based on the detection sensitivity of the second magnetic sensor.

[0010] Optionally, determining the output value of the linear displacement based on the first and second detected values ​​of the linear displacement further includes: when the absolute value of the first detected value of the linear displacement is greater than a first threshold, the absolute value of the second detected value of the linear displacement is less than a second threshold, and the absolute value of the first detected value of the linear displacement is less than or equal to the sum of the absolute value of the second detected value of the linear displacement and the tolerance, the output value of the linear displacement is calculated based on the following formula:

[0011]

[0012] Among them, y out The output value represents the linear displacement, k1 represents the first coefficient, and y tK The first detected value represents the linear displacement, k2 represents the second coefficient, and y motor The second detection value represents the linear displacement.

[0013] Optionally, the control system further includes a Kalman filter for adjusting the first magnetic field strength using a Kalman filtering algorithm to generate a first detected value of the linear displacement based on the first magnetic field strength filtered by the Kalman filter.

[0014] Optionally, the first and second coefficients are determined using the Mamdani fuzzy logic algorithm based on the covariance of the first magnetic field strength filtered by Kalman and the second detected value of the linear displacement.

[0015] Optionally, the smaller the covariance of the first magnetic field strength filtered by Kalman, the larger the first coefficient, and the larger the second detected value of the linear displacement, the larger the second coefficient.

[0016] Optionally, the control unit is configured to: when it is determined that the first magnetic sensor is faulty and the first detection value of the linear displacement cannot be obtained from the first magnetic sensor, control the energizing state of the motor rotor using the second detection value of the linear displacement as the output value of the linear displacement until the output value of the linear displacement becomes unbiased relative to the reference zero position; when it is determined that the second magnetic sensor is faulty and the detection value of the rotational displacement cannot be obtained from the second magnetic sensor, control the energizing state of the motor rotor using the first detection value of the linear displacement as the output value of the linear displacement until the output value of the linear displacement becomes unbiased relative to the reference zero position; and / or when it is determined that both the first magnetic sensor and the second magnetic sensor are faulty, cause the rear wheels of the vehicle to be locked in a steering configuration so that they cannot be steered.

[0017] Optionally, according to another aspect of this application, a control method for a steering device for the rear wheels of a vehicle is provided, optionally executed using the control system for the steering device for the rear wheels of a vehicle described above. The steering device includes: a motor rotor configured to perform rotational displacement in an energized state; and a steering application mechanism configured to convert the rotational displacement into linear displacement for steering the rear wheels of the vehicle. The control method is characterized by comprising: detecting the strength and rate of change of a first magnetic field of a first magnet mounted to the steering application mechanism using a first magnetic sensor to generate a first detection value of the linear displacement; detecting the strength and rate of change of a second magnetic field of a second magnet mounted to the motor rotor using a second magnetic sensor to generate a detection value of the rotational displacement; determining a second detection value of the linear displacement based on the detection value of the rotational displacement; determining an output value of the linear displacement based on the first and second detection values ​​of the linear displacement to represent the steering angle of the rear wheels of the vehicle; and controlling the energized state of the motor rotor based on the offset distance of the output value of the linear displacement relative to a reference zero position.

[0018] The control system and method for a vehicle rear wheel steering device provided in this application, based on the use of a second magnetic sensor that directly detects the rotational displacement of the motor rotor, further adds a first magnetic sensor for directly detecting the linear displacement of the steering application mechanism. At the same time, the two magnetic sensors are used in combination under different conditions to provide the control unit with a more reliable and accurate linear displacement output value, so as to enable the vehicle rear wheels to be steered more accurately to the desired steering angle.

[0019] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which form part of this specification, illustrate embodiments of this application and, together with the specification, serve to explain the principles of this application.

[0021] Figure 1 This is a schematic block diagram of a vehicle rear wheel steering device and a control system for a vehicle rear wheel steering device according to one embodiment of this application.

[0022] Figure 2 yes Figure 1 Another schematic block diagram of the steering mechanism for the rear wheels of a vehicle and the control system for the steering mechanism for the rear wheels of a vehicle.

[0023] Figure 3 This is a flowchart of a control method for a steering device for the rear wheels of a vehicle according to one embodiment of this application.

[0024] Figure 4 This is another flowchart of a control method for a steering device for the rear wheels of a vehicle according to one embodiment of this application. Detailed Implementation

[0025] Various exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this application.

[0026] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0027] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0029] It should also be noted that the various variables and their values ​​described herein are converted in various devices and units in the form of signals or data to communicate the magnitudes of the various variables and their values ​​between the various devices and units. Therefore, for the sake of brevity, the variables and their values ​​will be referred to directly without mentioning the signals or data that represent them.

[0030] Figure 1 and Figure 2The diagram schematically illustrates a rear-wheel steering system for a vehicle, primarily comprising: a motor, which may include a rotor 10, which may include, for example, a rotating shaft; the rotor 10 being capable of rotating at a speed applied by torque when energized to perform rotational displacement; a steering application mechanism associated with the motor's motion, which may include a multi-stage transmission mechanism 12 and an actuator 14 associated with the multi-stage transmission mechanism 12; on the one hand, the multi-stage transmission mechanism 12 is capable of converting the rotational displacement of the rotor 10 into linear displacement at a certain transmission ratio K; on the other hand, the actuator 14 is capable of transmitting the linear displacement from the multi-stage transmission mechanism 12 to the rear axle steering knuckle for steering the rear wheels of the vehicle; and an RWS (Rear Wheel Steering) control ECU (Electronic Control Unit) 16, which is typically integrated with the motor. 16 is configured to receive signals from other ECUs in the vehicle (including signals regarding power supply, steering wheel angle, vehicle speed, yaw rate, lateral acceleration, longitudinal acceleration, wheel speeds of the front and rear wheels, and braking status, etc.) to determine control commands based on these signals. The control commands are used to control the energization state of rotor 10, i.e., control the motor assist, so that rotor 10 performs a rotational displacement of a desired number of rotations / rotation angle, thereby causing the steering application mechanism to perform a linear displacement of a desired stroke, and further causing the rear wheels of the vehicle to perform a steering angle of a desired direction. The housing 18 preferably houses the motor, steering application mechanism, RWS control ECU 16, and any other devices or units that need to be housed within the housing 18 in a waterproof and dustproof manner.

[0031] Figure 1 and Figure 2 A control system for a steering device for the rear wheels of a vehicle is also schematically shown. The control system includes: a first magnet 20 configured to be mounted to a steering application mechanism; a second magnet 22 configured to be mounted to a rotor 10; a first magnetic sensor 24, such as a Hall element, configured to detect a first magnetic field strength of the first magnet 20 and its rate of change to generate a first detection value of linear displacement; and a second magnetic sensor 26, such as a Hall sensor, configured to detect a second magnetic field strength of the second magnet 22 and its rate of change to generate a detection value of rotational displacement.

[0032] The multi-stage transmission mechanism 12 may include at least one of the following transmission mechanisms: belt drive mechanism, gear drive mechanism, worm gear drive mechanism, lead screw and nut mating mechanism, and gear and rack mating mechanism, etc.

[0033] Taking the final stage transmission mechanism of the multi-stage transmission mechanism 12 as a gear and rack mechanism (which can also be a screw and nut mechanism) as an example, the gear in the gear and rack mechanism transmits the rotational displacement from the previous stage transmission mechanism to the rack 12a of the gear and rack mechanism, converting it into linear displacement of the rack 12a. The rack 12a is fixedly connected to the actuator 14 at least in the bidirectional translational direction, so that the actuator 14 translates accordingly. The first magnet 20 can be fixed to any suitable position of either the rack 12a or the actuator 14 by any suitable means, such as bolts, screws, or adhesives, so that it translates together with the rack 12a and the actuator 14. Figure 1 and Figure 2 The first magnet 20 is shown as being fixed to the rack 12a.

[0034] Alternatively, the first magnetic sensor 24 can be fixed to the housing 18 by any suitable means, such as mechanical fasteners like bolts and screws, or adhesives, so that the first magnetic sensor 24, especially the read head of the first magnetic sensor 24, is positioned relative to the first magnet 20 at a constant interval distance Δd1 (exaggerated for clarity). As a supplement or alternative, a fixing device made of a non-magnetic material can be specially provided at the location on the housing 18 for fixing the first magnetic sensor 24 to prevent affecting the detection sensitivity of the first magnetic sensor 24.

[0035] In the initial state where the vehicle's rear wheels are not steerable (i.e., returning to center), the first magnet 20, fixed to either the rack 12a or the actuator 14, is located at a reference zero position relative to the first magnetic sensor 24 (i.e., the read head of the first magnetic sensor 24), which is fixed to the housing 18. Preferably, when the first magnet 20 is located at the reference zero position, the gear of the rack and pinion mechanism meshes with the rack 12a at the middle position. When the rotor 10 performs rotational displacement in the energized state, the rack 12a, actuator 14, and first magnet 20 perform linear displacement, causing a change in the first magnetic field strength of the first magnet 20 detected by the first magnetic sensor 24. The first magnetic sensor 24 can determine a first detected value of the linear displacement based on the first magnetic field strength and its rate of change.

[0036] Assuming the total stroke of the first magnet 20 is within ±13mm of the reference zero position, and the steering angle of the vehicle's rear wheels corresponding to the total stroke is within ±6°, when the vehicle's rear wheels are not turning or are turning slightly, the first magnet 20 has no offset relative to the reference zero position (e.g., Figure 1 (as shown) or offset distance Δd2 (as shown) Figure 2(As shown, exaggerated for clarity) For example, within a range of ±2 mm, due to the close sensing distance between the first magnet 20 and the first magnetic sensor 24, the detection sensitivity of the first magnetic sensor 24 is high; for example, the detection sensitivity value may be 0.05 mm or even smaller. As the rear wheels of the vehicle continue to turn, the first magnet 20 continues to shift relative to the reference zero position until the shift distance Δd2 is outside the range of ±8 mm. Due to the greater sensing distance between the first magnet 20 and the first magnetic sensor 24, the detection sensitivity of the first magnetic sensor 24 decreases; for example, the detection sensitivity value may reach 0.2 mm or even larger.

[0037] On the other hand, the second magnet 22 can be mounted to the rotor 10, for example, to a rotating shaft. Generally, the rotating shaft has a first end that is kinetically associated with the multi-stage transmission mechanism 12 and a second end that is axially opposite to the first end. The second magnet 22 can be centrally mounted to the second end of the rotating shaft, and the second magnetic sensor 26 can be integrated as a chip on a circuit board including the RWS control ECU 16, positioned relative to the second magnet 22 at a constant interval. Thus, the second magnetic field strength of the second magnet 22 and its rate of change are detected by the second magnetic sensor 26 to generate a detection value of the rotational displacement of the rotor 10. This is well known in the prior art and will not be described further herein.

[0038] The detection sensitivity of the second magnetic sensor 26 can be low; for example, the detection sensitivity value can be approximately 0.2 mm or higher.

[0039] The control system also includes an additional control unit that can be integrated into the RWS control ECU 16 as part of the RWS control ECU 16. The additional control unit is configured to: acquire a first detection value of linear displacement from the first magnetic sensor 24; acquire a detection value of rotational displacement from the second magnetic sensor 26, and determine a second detection value of linear displacement based on the detection value of rotational displacement; and determine an output value of linear displacement based on the first and second detection values ​​of linear displacement to represent the steering angle of the vehicle's rear wheels.

[0040] It is understood that the first magnetic sensor 24 and the second magnetic sensor 26 can communicate with the additional control unit via wired (e.g., wire harness) or wireless means. Furthermore, the mounting positions of the first magnetic sensor 24 and the first magnet 20 cooperating with it on or near the motor rotor 10, and the mounting positions of the second magnetic sensor 26 and the second magnet 22 cooperating with it on or near the steering application mechanism, are unrestricted, provided that the first magnetic sensor 24 can detect linear displacement more directly than the second magnetic sensor 26, and that within a certain range of the total stroke length of the first magnet 20, the first magnetic sensor 24 can determine linear displacement more sensitively and accurately than the second magnetic sensor 26.

[0041] Determining the second detected value of linear displacement based on the detected value of rotational displacement can be accomplished by multiplying the detected value of rotational displacement by the transmission ratio K. For example, if the detected value of rotational displacement is two rotations, i.e., a rotation angle of 720°, the additional control unit can multiply 720° by the transmission ratio K (in mm / °) to obtain the second detected value of linear displacement.

[0042] refer to Figure 3 y out The output value representing linear displacement, y tK The first detected value y represents the linear displacement. tK , and y motor The second detected value represents the linear displacement. The first detected value of linear displacement, y, is mentioned in this article. tK Second detection value y motor The sign of the signal is actually determined by the translational direction of the rack 12a, the actuator 14, and the first magnet 20, as well as the rotational direction of the rotor 10 and the second magnet 22. However, in the following optional steps, the first detected value of linear displacement y can be used. tK Second detection value y motor The absolute value is used as the calculation object, therefore the first threshold A, the second threshold B, and the tolerance C mentioned below are all positive values.

[0043] Optionally, based on the first detected value y of the linear displacement tK Second detection value y motor Determine the output value y of the linear displacement out Including the first detected value y of the linear displacement tK When the absolute value is less than or equal to the first threshold A, the first detection value y of the linear displacement is used. tK The output value y as linear displacement outThe first threshold A is determined based on the detection sensitivity of the first magnetic sensor 24. For example, when the first magnet 20 is offset relative to the reference zero position within ±2 mm, the detection sensitivity of the first magnetic sensor 24 may be 0.05 mm or even smaller. In this case, the first threshold A can be set to 2 mm so that when the first magnet 20 has no offset relative to the reference zero position or the offset distance Δd2 is within ±2 mm, the first detection value y of the linear displacement obtained from the more sensitive first magnetic sensor 24 can be used. tK This is to help determine more accurately whether the first magnet 20 has returned to the reference zero position or is positioned at a specific location near the reference zero position, so as to more accurately represent the steering angle of the vehicle's rear wheels.

[0044] Optionally, when the first detected value of linear displacement y tK The absolute value of the second detection value y of the linear displacement is greater than the first threshold A. motor When the absolute value is greater than or equal to the second threshold B, the second detection value y is obtained with linear displacement. motor The output value y as linear displacement out The second threshold B is determined based on the detection sensitivity of the first magnetic sensor 24 and the detection sensitivity of the second magnetic sensor 26. For example, when the first magnet 20 deviates from the reference zero point to a range beyond ±8 mm, the detection sensitivity of the first magnetic sensor 24 may reach 0.2 mm or even greater. In this case, since the detection sensitivity of the second magnetic sensor 26 is approximately 0.2 mm, the second detection value y of the linear displacement obtained from the second magnetic sensor 26 can be used. motor To ensure that the output value y is maintained using linear displacement, out This represents the accuracy of the steering angle of the vehicle's rear wheels.

[0045] Optionally, when the first detected value of linear displacement y tK The absolute value of the first detection value is greater than the first threshold A, the absolute value of the second detection value of the linear displacement is less than the second threshold B, and the absolute value of the first detection value of the linear displacement y is greater than the first threshold A. tK The absolute value is greater than the second detection value y of the linear displacement. motor When the absolute value of the linear displacement is summed with the tolerance C, the second detection value y of the linear displacement is used. motor The output value y as linear displacement out The tolerance C is determined based on the detection sensitivity of the second magnetic sensor 26. For example, when the detection sensitivity of the second magnetic sensor 26 is approximately 0.2 mm, the tolerance C can be set to 0.2 mm.

[0046] Optionally, when the first detected value of linear displacement y tK The absolute value is greater than the first threshold, and the second detection value of the linear displacement is y. motorThe absolute value is less than the second threshold B, and the first detection value y of the linear displacement tK The absolute value of the second detection value y is less than or equal to the linear displacement. motor When the absolute value of the linear displacement is summed with the tolerance C, the output value y of the linear displacement is calculated based on the following formula (1). out :

[0047]

[0048] Where k1 represents the first coefficient, which indicates the first detected value y of the linear displacement. tK The signal weights, and k2 represents the second coefficient, which can indicate the second detected value y of the linear displacement. motor Signal weights.

[0049] Therefore, in the first detected value y of the linear displacement tK The second detection value y, which is greater than the first threshold A and the linear displacement, motor The first detected value y of the linear displacement within the interval less than the second threshold B. tK Is the absolute value greater than the second detection value y of the linear displacement? motor The sum of the absolute value and the tolerance C is used to determine whether the first detection value y of the linear displacement should be used. tK Second detection value y motor This is combined to more accurately represent the steering angle of the vehicle's rear wheels.

[0050] It is understandable that the first detected value y is based on the linear displacement. tK Second detection value y motor Determine the output value y of the linear displacement out It may include one or more of the above optional steps, and when there are multiple optional steps, these optional steps may be performed in the order described above or in another reasonable order.

[0051] The additional control unit can further base its output value y on the linear displacement. out The energizing state of rotor 10 is controlled by the offset distance Δd2 relative to the reference zero position, i.e., the motor assist is controlled, so that the rear wheels of the vehicle can be more precisely steered to the desired steering angle. The additional control unit can also send signals about the steering angle of the rear wheels to other ECUs in the vehicle, for example, via the CAN bus, to achieve closed-loop control.

[0052] Reference Figure 4 The control method for the steering device of the rear wheels of a vehicle accordingly includes the following steps:

[0053] S1. The first magnetic field strength and its rate of change of the first magnet 20 installed on the steering application mechanism are detected by the first magnetic sensor 24 to generate a first detection value y of linear displacement. tK ;

[0054] S2. The second magnetic field strength and its rate of change of the second magnet 22 installed on the motor rotor 10 are detected by the second magnetic sensor 26 to generate a detection value of rotational displacement;

[0055] S3. Determine the second detection value y of the linear displacement based on the detected value of the rotational displacement. motor ;

[0056] S4. First detection value y based on linear displacement tK Second detection value y motor Determine the output value y of the linear displacement out , to represent the steering angle of the vehicle's rear wheels; and

[0057] S5. Output value y based on linear displacement out The energizing state of the motor rotor 10 is controlled by the offset distance Δd2 relative to the reference zero position.

[0058] The control method for a steering device for the rear wheels of a vehicle provided in this application is intended to be executed using a control system for a steering device for the rear wheels of a vehicle. Therefore, the features of the control system and the features of the control method described herein can correspond to, combine, and be interchanged with each other.

[0059] Optionally, the control system may also include a Kalman filter for adjusting the first magnetic field strength using a Kalman filtering algorithm to generate a more accurate first detection value of linear displacement based on the first magnetic field strength that has been Kalman filtered to remove noise from the first sensor.

[0060] In this application, the Kalman prediction model is shown in Equation (2):

[0061]

[0062] in, This represents the mean of the first magnetic field strength predicted by the Kalman prediction model during the current detection period. B represents the mean of the first magnetic field strength after Kalman filtering in the previous detection cycle. at This represents the rate of change of the first magnetic field strength obtained from the first magnetic sensor in the current cycle. Additionally, A and D are constant terms set after the first magnet and the first magnetic sensor are installed to establish a relationship model between the first detected value of linear displacement and the first magnetic field strength; these can be determined based on the characteristic parameters of the first magnet and the first sensor. This represents the covariance of the first magnetic field strength predicted by the Kalman prediction model during the current detection period. A T Let A be the transpose matrix. Q represents the covariance of the random process error, which can also be determined based on the characteristic parameters of the first magnet and the first sensor.

[0063] The rate of change B of the first magnetic field strength can be determined using formula (2). at Calculate the mean value of the first magnetic field strength predicted by the Kalman prediction model during the current detection period. Simultaneously, based on the covariance P of the first magnetic field strength filtered by Kalman in the previous detection cycle... t-1 The covariance Q of the random process error is used to calculate the covariance predicted by the Kalman prediction model in the current detection period.

[0064] Meanwhile, the Kalman update model is shown in equation (3):

[0065]

[0066] Among them, K t C represents the Kalman gain coefficient. C represents the coefficient matrix that converts the first magnetic field strength into the first detected value of linear displacement. T represents the transpose of the coefficient matrix. R represents the detection error of the first magnetic sensor during the detection process. B t y represents the first magnetic field strength directly obtained from the first magnetic sensor in the current cycle. t The first detected value represents the linear displacement; therefore, y t =CB t I is the identity matrix.

[0067] The Kalman gain coefficient K was calculated using the Kalman update model. t Then, using the Kalman gain coefficient K... t The mean of the first magnetic field strength predicted in the Kalman prediction model and the covariance of the first magnetic field strength predicted in the Kalman prediction model Adjustments are made to obtain the mean value of the first magnetic field strength filtered by Kalman in the current period. The covariance P of the first magnetic field strength filtered by Kalman in the current period t In fact, by using formula (4), the mean of the first magnetic field strength filtered by Kalman in the current period is obtained. Covariance P t The probability density function of the first magnetic field strength, which is assumed to follow a Gaussian normal distribution, can be expressed as follows:

[0068]

[0069] Then, using formula (5), the mean value of the first magnetic field strength filtered by Kalman in the current period is used. Calculate the first detected value of the linear displacement:

[0070]

[0071] Alternatively, the covariance P of the first magnetic field strength after Kalman filtering can be used as the basis for the Mamdani fuzzy logic algorithm. t The second detection value y of linear displacement motor To determine the first coefficient k1 and the second coefficient k2.

[0072] In the Mamdani fuzzy logic algorithm, the covariance P of the magnetic field strength filtered by Kalman in the current cycle is used. t and the second detection value y of the linear displacement calculated in the current period. motor As inputs to the fuzzy logic algorithm, the first coefficient k1 and the second coefficient k2 serve as outputs, with their universes of discourse being |y| and |y|, respectively. motor |∈[A,B]、|P t |∈[0,P], k1∈[0,1], k2∈[0,1]. In the fuzzification of the Mamdani fuzzy logic algorithm, the membership function is, for example, a Gaussian (Gaussmf) function. The membership function mainly transforms the actual values ​​of the input and output quantities into continuous values ​​within the interval [0,1] in the fuzzy set. The closer the value is to 1, the higher the membership degree. The fuzzy language subset of the Gaussian function is defined as [NB,NS,ZO,PS,PB], and the subset distribution interval is uniformly divided. Then, the fuzzy decision method in defuzzification is, for example, the area equal division method (bisector).

[0073] Since the fuzzy operation rules of the Mamdani fuzzy logic algorithm in this application have two input quantities and two output quantities, the computer programming language is "if y motor and P t "then k1 and k2", so that the fuzzy operation rule table is as follows:

[0074] Table 1 Fuzzy Operation Rules

[0075]

[0076] Due to the covariance P of the first magnetic field strength after Kalman filtering t The smaller the value, the higher the detection accuracy of the first magnetic sensor, while the second detection value y changes with linear displacement. motorBetween the first threshold A and the second threshold B, the detection accuracy of the first magnetic sensor decreases as it approaches the second threshold B. Therefore, the principle for establishing the aforementioned fuzzy rule table is defined as: the covariance P of the first magnetic field strength filtered by the Kalman filter. t The smaller the value, the larger the first coefficient k1, and the larger the second detection value y of the linear displacement. motor The larger the value, the larger the second coefficient k2.

[0077] Understandably, the first coefficient k1 and the second coefficient k2 can also be determined using other types of fuzzy logic algorithms, as long as the covariance P of the first magnetic field strength filtered by the Kalman filter increases. t The smaller the value, the larger the first coefficient k1 can be, and the larger the second detection value y of the linear displacement. motor The larger the value, the larger the second coefficient k2 can be.

[0078] Optionally, the control unit is configured to, when it is determined that the first magnetic sensor 24 is faulty and cannot obtain a first detection value y of linear displacement from the first magnetic sensor 24... tK At that time, the second detection value y of the linear displacement motor The output value y of the linear displacement out To control the energizing state of the motor rotor 10 until the output value of linear displacement y is reached. out It becomes zero relative to the reference zero position. In other words, during the operation of the first magnetic sensor 24 and the second magnetic sensor 26, the RWS control ECU 16 and / or the additional control unit can monitor both the first magnetic sensor 24 and the second magnetic sensor 26 in real time. When the RWS control ECU 16 and / or the additional control unit receive a fault signal sent from the first magnetic sensor 24, they can only calculate the linear displacement output value y based on the detected value of the rotational displacement obtained from the second magnetic sensor 26. out This represents the steering angle of the vehicle's rear wheels, and the steering angle of the vehicle's rear wheels should be corrected in time, thus ensuring that the output value y of the linear displacement is [value missing]. out The value is reduced to zero. This ensures the safety of vehicle operation. It is also necessary to alert vehicle occupants through methods such as flashing lights and displaying text warnings to ensure that any malfunctions of the first magnetic sensor 24 can be addressed promptly.

[0079] Optionally, the control unit is configured to, when it is determined that the second magnetic sensor 26 is faulty and cannot obtain a detection value of rotational displacement from the second magnetic sensor 26, use a first detection value of linear displacement y. tK The output value y as linear displacement out To control the energizing state of the motor rotor 10 until the output value of linear displacement y is reached. outIt becomes zero relative to the reference zero position. When the RWS control ECU 16 and / or the additional control unit receive a fault signal from the second magnetic sensor 26, it can only use the first detected value y of the linear displacement obtained from the first magnetic sensor 24. tK The output value y as linear displacement out This represents the steering angle of the vehicle's rear wheels, and the steering angle of the vehicle's rear wheels should be corrected in time, thus ensuring that the output value y of the linear displacement is [value missing]. out The value is reduced to zero. This ensures the safety of vehicle operation. It is also necessary to alert vehicle occupants through methods such as flashing lights and displaying text warnings to ensure that any malfunctions of the second magnetic sensor 26 can be addressed promptly.

[0080] Optionally, the control unit is configured to lock the rear wheels of the vehicle to prevent steering when both the first magnetic sensor 24 and the second magnetic sensor 26 are determined to be faulty. This ensures vehicle driving safety. It is also necessary to alert vehicle occupants through methods such as flashing lights and displaying text warnings to ensure that the faults of the first magnetic sensor 24 and the second magnetic sensor 26 are addressed promptly.

[0081] It is understood that the control unit is configured to perform one or more of the above optional steps, and when there are multiple optional steps, these optional steps can be performed in the order described above or other reasonable order.

[0082] Furthermore, the RWS control ECU 16, optional additional control unit, first magnetic sensor 24, and second magnetic sensor 26 described above each actually include a memory and a processor. On one hand, the memory can store various executable instructions and their parameters. The memory can include electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples of memory include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusion structures storing instructions thereon, and any suitable combination thereof. On the other hand, when the executable instructions and their parameters are executed by the processor, means are created to implement the steps described in the specification and the functions / operations specified in one or more boxes in the flowcharts and / or block diagrams in the accompanying drawings.

[0083] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of control systems, control methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions. It will be known to those skilled in the art that implementation in hardware, implementation in software, and implementation using a combination of software and hardware are equivalent.

[0084] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A control system for a steering device for the rear wheels of a vehicle, The steering device includes: The motor rotor (10) is configured to perform rotational displacement when energized; and A steering application mechanism is configured to convert the rotational displacement into linear displacement for steering the rear wheels of the vehicle; The control system is characterized by comprising: A first magnet (20) is configured to be mounted to the steering application mechanism; A second magnet (22) is configured to be mounted to the motor rotor (10); A first magnetic sensor (24) is configured to detect the first magnetic field strength and its rate of change of the first magnet (20) to generate a first detection value of the linear displacement; A second magnetic sensor (26) is configured to detect the strength of a second magnetic field of a second magnet (22) and the rate of its change, in order to generate a detected value of the rotational displacement; and The control unit is configured to: The first detection value of the linear displacement is obtained from the first magnetic sensor (24); The detection value of the rotational displacement is obtained from the second magnetic sensor (26), and a second detection value of the linear displacement is determined based on the detection value of the rotational displacement; An output value of the linear displacement is determined based on a first and a second detected value, to represent the steering angle of the vehicle's rear wheels; and The energizing state of the motor rotor (10) is controlled based on the offset distance of the output value of the linear displacement relative to the reference zero position.

2. The control system according to claim 1, characterized in that, Determining the output value of the linear displacement based on the first and second detected values ​​of the linear displacement includes: When the absolute value of the first detected value of the linear displacement is less than or equal to the first threshold (A), the first detected value of the linear displacement is used as the output value of the linear displacement, and the first threshold (A) is determined based on the detection sensitivity of the first magnetic sensor (24).

3. The control system according to claim 2, characterized in that, Determining the output value of the linear displacement based on the first and second detected values ​​of the linear displacement further includes: When the absolute value of the first detection value of the linear displacement is greater than the first threshold (A) and the absolute value of the second detection value of the linear displacement is greater than or equal to the second threshold (B), the second detection value of the linear displacement is used as the output value of the linear displacement, and the second threshold (B) is determined based on the detection sensitivity of the first magnetic sensor (24) and the detection sensitivity of the second magnetic sensor (26).

4. The control system according to claim 3, characterized in that, Determining the output value of the linear displacement based on the first and second detected values ​​of the linear displacement further includes: When the absolute value of the first detection value of the linear displacement is greater than the first threshold (A), the absolute value of the second detection value of the linear displacement is less than the second threshold (B), and the absolute value of the first detection value of the linear displacement is greater than the sum of the absolute value of the second detection value of the linear displacement and the tolerance (C), the second detection value of the linear displacement is used as the output value of the linear displacement, and the tolerance (C) is determined based on the detection sensitivity of the second magnetic sensor (26).

5. The control system according to claim 4, characterized in that, Determining the output value of the linear displacement based on the first and second detected values ​​of the linear displacement further includes: When the absolute value of the first detected value of the linear displacement is greater than the first threshold (A), the absolute value of the second detected value of the linear displacement is less than the second threshold (B), and the absolute value of the first detected value of the linear displacement is less than or equal to the sum of the absolute value of the second detected value of the linear displacement and the tolerance (C), the output value of the linear displacement is calculated based on the following formula: in, The output value represents the linear displacement. Represents the first coefficient. The first detected value represents the linear displacement. Represents the second coefficient. The second detection value represents the linear displacement.

6. The control system according to claim 5, characterized in that, The control system further includes a Kalman filter for adjusting the first magnetic field strength using a Kalman filtering algorithm to generate a first detected value of the linear displacement based on the first magnetic field strength filtered by the Kalman filter.

7. The control system according to claim 6, characterized in that, The first and second coefficients are determined using the Mamdani fuzzy logic algorithm based on the covariance of the first magnetic field strength filtered by Kalman and the second detected value of the linear displacement.

8. The control system according to claim 7, characterized in that, The smaller the covariance of the first magnetic field strength after Kalman filtering, the larger the first coefficient; and the larger the second detected value of the linear displacement, the larger the second coefficient.

9. The control system for a steering device for the rear wheels of a vehicle according to any one of claims 1 to 8, characterized in that, The control unit is configured to: When it is determined that the first magnetic sensor (24) is faulty and the first detection value of the linear displacement cannot be obtained from the first magnetic sensor (24), the second detection value of the linear displacement is used as the output value of the linear displacement to control the energizing state of the motor rotor (10) until the output value of the linear displacement becomes no offset relative to the reference zero position; When it is determined that the second magnetic sensor (26) is faulty and the detection value of the rotational displacement cannot be obtained from the second magnetic sensor (26), the first detection value of the linear displacement is used as the output value of the linear displacement to control the energizing state of the motor rotor (10) until the output value of the linear displacement becomes unbiased relative to the reference zero position; and / or When it is determined that both the first magnetic sensor (24) and the second magnetic sensor (26) are faulty, the rear wheels of the vehicle are locked in a steering manner so that they cannot be steered.

10. A control method for a steering device for the rear wheels of a vehicle, executed using a control system for a steering device for the rear wheels of a vehicle according to any one of claims 1 to 9. The steering device includes: The motor rotor (10) is configured to perform rotational displacement when energized; and A steering application mechanism is configured to convert the rotational displacement into linear displacement for steering the rear wheels of the vehicle; The control method is characterized by comprising: The first magnetic field strength and its rate of change of the first magnet (20) installed on the steering application mechanism are detected by the first magnetic sensor (24) to generate the first detection value of the linear displacement; The second magnetic field strength and its rate of change of the second magnet (22) installed on the motor rotor (10) are detected by the second magnetic sensor (26) to generate the detected value of the rotational displacement; A second detection value for the linear displacement is determined based on the detected value of the rotational displacement; An output value of the linear displacement is determined based on a first and a second detected value, to represent the steering angle of the vehicle's rear wheels; and The energizing state of the motor rotor (10) is controlled based on the offset distance of the output value of the linear displacement relative to the reference zero position.

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