Method of stabilizing set torque of motor in power steering system
The method stabilizes motor torque in steer-by-wire systems by determining intermediate and limit values based on angular positions and previous torque, enhancing steering accuracy and comfort in vehicles with electronic power steering.
Patent Information
- Application Number
- JP2024212246
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-12-13
- Filing Date
- 2024-12-05
- Publication Date
- 2025-06-25
AI Technical Summary
Existing power steering systems in vehicles without mechanical connections, known as 'steer-by-wire', fail to accurately determine the cause of malfunctions between the set and actual angular positions of the rack, leading to potential safety issues.
A method for stabilizing the set torque of the motor by determining intermediate and limit values based on parameters representing the set and actual angular positions, vehicle speed, and previous motor torque, using proportional, differential, and integration gains, along with low-pass filtering to ensure accurate and stable motor control.
This method enhances the accuracy of motor torque control, reducing the impact of malfunctions and maintaining vehicle safety by ensuring the set torque remains within defined limits, thus improving steering precision and comfort across varying speeds.
Smart Images
Figure 2025094912000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of vehicles equipped with a power steering system, and more particularly to a method for stabilizing the set torque of a motor.
Background Art
[0002] The steering system of a vehicle aims to enable the driver to control the vehicle's trajectory by changing the direction angle of the vehicle's wheels using the steering wheel. The driver changes the angle of the steering wheel by applying a force to the steering wheel.
[0003] Generally, the steering system has a plurality of components including the steering wheel, a rack, and two wheels each connected to a connecting rod (tie rod). The rack is a component that enables the operation of the wheels via the connecting rod, that is, a component that enables the change of the direction angle of the wheels. The angular position of the rack with respect to the steering case is hereinafter referred to as the "rack angle position", which reflects the direction angle of the wheels.
[0004] In an electric power steering system called "steer-by-wire" without a mechanical connection, the steering wheel is mechanically disconnected from the rack. In this case, the steering system has a steering wheel unit that is mechanically independent of the rack unit. In other words, the force applied to the steering wheel unit is not mechanically transmitted to the rack unit, and vice versa.
[0005] The steering wheel unit has the steering wheel and at least one means for estimating the angle of the steering wheel, for example, an angle sensor.
[0006] The rack unit has the rack movable within the steering housing and at least one electronic control unit that controls, in particular, the angular position of the rack to match a set angular position (target angular position). The set angular position generally matches the steering wheel angle, but may be changed by vehicle functions such as a lane tracking function or a vehicle parking assistance function.
[0007] The electronic control unit determines a set motor torque (or set torque hereinafter) in order to control at least one motor that applies motor torque to the rack. In other words, the controller servo-controls the angular position of the rack to the set angular position by determining the set torque of the motor.
[0008] To ensure vehicle safety, proper operation of the controller, in particular reliable position control of the rack, is important, whereby the consistency between the set angular position and the rack angular position can be ensured.
[0009] There are known solutions that enable detection of a failure (malfunction) of the rack unit. The failure of the rack unit is defined as the difference between the angular position of the rack and the set angular position. When a malfunction (functional failure) is detected, servo control is executed by a backup controller.
Summary of the Invention
Problems to be Solved by the Invention
[0010] The drawback of this solution is that the cause of the malfunction cannot be determined. Therefore, it is not possible to judge whether the difference between the angular position of the rack and the set angular position is due to a failure of the controller or other causes such as wheel lock.
[0011] Therefore, it is necessary to stabilize the controller more efficiently.
Means for Solving the Problems
[0012] One embodiment relates to a method for stabilizing the set torque (target torque) of a motor, wherein the motor applies a motor torque to a device of a vehicle's power steering system to change the angular position of the device. This method is executed by at least one controller, and this method comprises: a first determination step in which at least one first intermediate value of the set torque is determined (as a function) based on at least one parameter representing the set angular position (target angular position) of the device and at least one parameter representing the angular position of the device; a second determination step in which a limit value of at least one first intermediate value of the set torque is determined based on at least the parameter representing the set angular position and at least the parameter representing the angular position; a third determination step in which a parameter representing the average motor torque acting at a previous time point is determined; a stabilization step in which a target value of the set torque is determined based on at least the first intermediate value of the set torque, the limit value of the first intermediate value of the set torque, and the parameter representing the average motor torque acting at a previous time point; and having.
[0013] The controller can be an electronic control unit.
[0014] The set torque indicates any quantity representing the set torque that enables control of the motor torque.
[0015] In one embodiment, the device on which the motor acts with the motor torque is the rack of the vehicle's power steering system.
[0016] In one embodiment, the power steering system is of a type without mechanical links.
[0017] In the first step, at least one first intermediate value of the set torque is determined. In other words, in one embodiment, the set torque can be determined based on several intermediate values.
[0018] The first intermediate value is determined based on at least a parameter representing the target angular position of the device and at least a parameter representing the angular position of the device. The parameter representing the target angular position or the parameter representing the angular position can be an angle, the position of the device relative to a certain point (reference point) of the motor, or the angular position of the motor. The parameter representing the angular position can be determined (calculated), estimated, or measured.
[0019] In a certain embodiment, the first intermediate value is obtained by calculating the difference between the parameter representing the target angular position and the parameter representing the angular position in particular, and multiplying the difference by a first gain. The first gain is hereinafter referred to as the "proportional gain".
[0020] In a certain embodiment, the first intermediate value is obtained by saturation processing of the integrated value of the product of the difference and the proportional gain. Therefore, "overflow" of the first intermediate value does not occur, that is, the first intermediate value is limited.
[0021] In a certain embodiment, the first determination step also determines at least one first intermediate value of the set torque based on the speed of the vehicle.
[0022] More specifically, the proportional gain may be determined by the speed of the vehicle.
[0023] Therefore, the proportional gain corrects the speed at which the vehicle wheels follow the set angular position. At the vehicle level, this changes the accuracy with which the driver can control the direction angle of the wheels. By reducing the proportional gain, this accuracy decreases, but the comfort of driving is improved because higher-frequency (higher-frequency) operations of the wheel direction are filtered out (removed).
[0024] Generally, a vehicle is equipped with a rack having a variable ratio according to the vehicle speed between the set angular position and the steering angle of the wheels. In other words, at 20 km / h, since the vehicle's trajectory changes slowly, the rack ratio is substantially direct, and the steering angle of the wheels changes substantially proportionally to the set angular position. At high speeds, since a slight change in the steering angle of the wheels causes significant snake / oscillation of the vehicle, the rack ratio is not very direct, and the change in the steering angle of the wheels is smaller than the set angular position.
[0025] According to one embodiment, the proportional gain increases with the vehicle speed.
[0026] Therefore, at 20 km / h, the proportional gain decreases and the steering accuracy of the steering angle of the wheels decreases, but the driving comfort improves, for example, when the set angular position changes suddenly, that is, when the driver vibrates the steering wheel.
[0027] For example, during high-speed driving at 130 km / h, since the rack ratio is not very direct, it is important to maintain high accuracy, and thus a large proportional gain is important.
[0028] In the second step, a limit value of at least one first intermediate value of the set torque is determined. When a plurality of intermediate values are determined, a plurality of limit values are determined in the second step. In other words, for each intermediate value determined in the first determination step, a limit value is determined in the second determination step.
[0029] In an embodiment, the limit value is obtained by calculating the difference between a parameter representing the set angular position and a parameter representing the angular position, and multiplying the difference by a first limit gain. The first limit gain is hereinafter referred to as the "limit proportional gain".
[0030] The limit value may be a pair of limit values having an upper limit value and a lower limit value. Alternatively, only one of the upper limit value or the lower limit value may be determined, and the other of the upper limit value or the lower limit value may be calculated by symmetry.
[0031] In one embodiment, the second determination step determines a limit value of at least one first intermediate value of the set torque based on the vehicle speed.
[0032] More specifically, the limiting proportional gain may be determined by the vehicle speed.
[0033] The third step determines a parameter representing the average motor torque acting at a previous time point.
[0034] The term "previous time point" means a time point located in the past with respect to the calculation of the target value of the current set torque. This previous time point is determined particularly by the speed at which the stabilization method is implemented.
[0035] Finally, in the stabilization step, at least one first intermediate value of the set torque, the limit value of at least one first intermediate value of the set torque, and a parameter representing the average motor torque acting at a previous time point are combined to determine the target value of the set torque.
[0036] The parameter representing the average motor torque can be obtained by various means such as a low-pass filter. By using the parameter representing the average motor torque, it becomes possible to ignore rapid changes in the motor torque.
[0037] The target value of the set torque is the torque value that it is desired for the motor to act on the device. This is a safe set torque. In other words, it can be guaranteed that the required set torque corresponding to the target value of the set torque is included in a defined interval around the parameter representing the average motor torque acting at a previous time point by the stabilization step. In other words, there is a framework for the target value of the set torque. Therefore, there is no large and rapid deviation from the required set torque. Therefore, errors related to malfunctions (functional failures) of the controller that executes at least the first step are avoided, or the impact of failures is limited without switching to another control strategy such as a backup law or another controller.
[0038] In one embodiment, the parameter representing the average motor torque acting at a previous time is determined based on at least the parameter representing the set angular position and at least the parameter representing the angular position of the device.
[0039] One means for determining the parameter representing the average motor torque is to use at least the parameter representing the set angular position and at least the parameter representing the angular position of the device.
[0040] In one embodiment, the parameter representing the average motor torque is obtained by particularly calculating the difference between the parameter representing the set angular position and the parameter representing the angular position, and then multiplying the difference by a gain hereinafter referred to as an "integration gain".
[0041] In one embodiment, the parameter representing the average motor torque is obtained by saturation processing and integration of the integrated value of the difference and the integration gain. Therefore, there is no "overflow" of the parameter representing the average motor torque, that is, the parameter representing the average motor torque is limited.
[0042] In one embodiment, the parameter representing the average motor torque is determined based on at least the vehicle speed.
[0043] More specifically, the integration gain may be determined by the speed of the vehicle.
[0044] In one embodiment, the parameter representing the average motor torque acting at a previous time is determined based on the target value of the set torque at the previous time or based on the measured value of the parameter representing the motor torque acting at the previous time.
[0045] The measurement of the acting motor torque can be carried out directly or indirectly in the device or the motor.
[0046] In one embodiment, the parameter representing the average motor torque acting at the previous time point is determined by applying a low-pass filter to the target value of the set torque at the previous time point or the measured value of the parameter representing the motor torque acting at the previous time point.
[0047] In one embodiment, the low-pass filter is a second-order filter.
[0048] Accordingly, the static part of the acting motor torque is obtained, that is, the rapid fluctuations of the acting motor torque are removed. This low-pass filter makes it possible to obtain a kind of "average" motor torque.
[0049] In one embodiment, the parameter representing the average motor torque acting at the previous time point is obtained by multiplying the filtered target value of the set torque at the previous time point or the filtered measured value of the parameter representing the motor torque acting at the previous time point by a gain hereinafter referred to as the "static gain".
[0050] In one embodiment, the static gain is determined by the speed of the vehicle.
[0051] In one embodiment, the stabilization method is a first evaluation step in which a provisional value of the set torque is evaluated based on at least one first intermediate value of the set torque and the parameter representing the average motor torque acting at the previous time point, and a second evaluation step in which a limit value of the provisional value of the set torque is determined based on the limit value of at least one first intermediate value of the set torque and the parameter representing the average motor torque acting at the previous time point, and a stabilization step in which the target value of the set torque is determined based on at least the provisional value of the set torque and the limit value of the provisional value of the set torque.
[0052] For example, the first evaluation step sums at least one first intermediate value of the set torque and a parameter representing the average motor torque acting at the previous point in time. In other words, when a plurality of intermediate values are determined, the first evaluation step sums the plurality of intermediate values of the set torque and a parameter representing the average motor torque acting at the previous point in time.
[0053] For example, the second evaluation step sums the limit value of the first intermediate value of the set torque and a parameter representing the average motor torque acting at the previous point in time. In other words, when a plurality of intermediate values are determined, that is, when a plurality of limit values are determined, the second evaluation step sums the plurality of limit values and a parameter representing the average motor torque acting at the previous point in time.
[0054] Next, in the stabilization step, the provisional value of the set torque is restricted by the limit value of the provisional value of the set torque, and the provisional value of the set torque is included in the limit value of that provisional value.
[0055] In one embodiment, the first determination step, the third determination step, and the first evaluation step are executed by a position controller of the device, and the second determination step, the third determination step, the second evaluation step, and the stabilization step are executed by a stabilization controller that particularly receives the provisional value of the set torque of the position controller as an input.
[0056] Therefore, the stabilization controller is arranged downstream independently of the position controller. Thus, on the one hand, it is possible to modify and adjust the position controller independently of the stabilization controller, and on the other hand, it is possible to place the stabilization controller in a section of the electronic control unit that is more resistant to failures than the position controller. Therefore, the stabilization of the set torque of the motor is guaranteed.
[0057] In one embodiment, this method A first stabilization step of determining at least one target value of at least one first intermediate value of the set torque is based on at least one first intermediate value of the set torque and a limit value of at least one first intermediate value of the set torque. The stabilization step determines the target value of the set torque based on the target value of at least one first intermediate value of the set torque and a parameter representing the average motor torque acting at the previous time.
[0058] The first stabilization step includes, for example, limiting at least one first intermediate value of the set torque by a limit value of at least one first intermediate value of the set torque. Therefore, the target value of at least one first intermediate value of the set torque does not exceed or is equal to the limit value of at least one first intermediate value of the set torque.
[0059] When a plurality of intermediate values are determined, each intermediate value is limited by an appropriate limit value.
[0060] The stabilization step determines the target value of the set torque based on at least the target value of at least one first intermediate value of the set torque and a parameter representing the average motor torque acting at the previous time.
[0061] For example, the target value of the set torque is obtained by the sum of at least one target value of at least one first intermediate value of the set torque and a parameter representing the average motor torque acting at the previous time. When a plurality of target values of a plurality of intermediate values are determined, the target value of the set torque is obtained by the sum of the target values of all intermediate values and a parameter representing the average motor torque acting at the previous time.
[0062] In an embodiment, the first determination step also determines a second intermediate value of the set torque based on at least one parameter representing the target speed of the device and a parameter representing the speed of the device, and the second determination step also determines a limit value of the second intermediate value of the set torque based on at least the parameter representing the target speed of the device and the parameter representing the speed of the device.
[0063] The parameter representing the target speed of the device or the parameter representing the speed of the device may be determined based on the parameter representing the set angular position of the device or the parameter representing the angular position of the device, or may be measured directly or indirectly in the motor or device.
[0064] In certain embodiments, the second intermediate value is obtained by calculating, in particular, the difference between the parameter representing the set speed and the parameter representing the speed of the device, and multiplying the difference by a second gain. The second gain is hereinafter referred to as the "differential gain".
[0065] In certain embodiments, the second intermediate value is obtained by saturation processing of the integrated value of the difference and the differential gain. Therefore, "overflow" of the second intermediate value does not occur, in other words, the second intermediate value is limited.
[0066] In certain embodiments, the first determination step also determines a second intermediate value of the set torque based on the speed of the vehicle.
[0067] More specifically, the differential gain may be determined by the speed of the vehicle.
[0068] Therefore, the differential gain changes the speed at which the vehicle wheels follow the set angular position. At the vehicle level, this changes the accuracy with which the driver can control the direction angle of the wheels. By reducing the differential gain, this accuracy decreases, but the driving comfort is improved because higher frequency (high frequency) wheel direction operations are filtered out (removed).
[0069] According to one embodiment, the differential gain increases with the speed of the vehicle.
[0070] Therefore, when the vehicle speed is 20 km / h, for example, when the set angular position changes rapidly, that is, when the driver rocks the steering wheel, the differential gain decreases and the accuracy of controlling the direction angle of the wheels decreases, but the driving comfort is improved.
[0071] At high speeds, such as 130 kilometers per hour, since the ratio of the rack is not very direct, it is important to maintain high precision and thus a high differential gain.
[0072] In one embodiment, the limit value of the second intermediate value of the set torque is obtained by calculating the difference between the parameter representing the set speed and the parameter representing the speed, and multiplying the difference by a second limit gain. The second limit gain is hereinafter referred to as the "limit differential gain".
[0073] In one embodiment, the second determination step determines the limit value of the second intermediate value of the set torque based on the vehicle speed.
[0074] More specifically, the limit differential gain may be determined by the vehicle speed.
[0075] Another aspect of the present invention relates to a vehicle equipped with a type of power steering system without a mechanical link for implementing the stabilization method according to the present invention.
[0076] The present invention will be better understood from the following description of a plurality of embodiments according to the present invention. These are shown as non-limiting examples and are described with reference to the accompanying schematic drawings.
Brief Description of the Drawings
[0077]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Best Mode for Carrying Out the Invention
[0078] Only the elements necessary for understanding the present invention will be described.
[0079] The present invention relates to methods 100, 200 for stabilizing (protecting, ensuring safety) the set torque of a pair of auxiliary motors 24, 24' of a power steering system 1 of a vehicle 2, and more particularly of a motor vehicle 2 intended for carrying people.
[0080] In a manner known per se and as shown in FIG. 5, the power steering system 1 comprises a steering wheel 3 by means of which the driver can apply a force called the "steering wheel torque" T3. The angle θ3 of the steering wheel 3 is measured by an angle sensor 23.
[0081] The steering wheel torque T3 and the angle θ3 of the steering wheel are transmitted to a rack electronic control unit 20.
[0082] The steering wheel 3 is not mechanically connected to the steering rack 6, which itself is guided to move translationally within a steering housing 7 fixed to the vehicle 2. In other words, the steering wheel 3 is mechanically disconnected from the steering rack 6. In this case, the steering system 1 comprises a steering wheel unit that is mechanically independent of the rack unit. That is, the force T3 applied to the steering wheel unit is not mechanically transmitted to the rack unit, and vice versa. The power steering system 1 is of the "without mechanical link" or "steer-by-wire" type.
[0083] The steering wheel unit has the steering wheel 3 and at least one steering wheel electronic control unit (not shown), and determines the torque (hereinafter referred to as the set control torque) that the driver should feel particularly during the operation of the steering wheel 3. The set control torque is particularly intended to make the driver feel torque information corresponding to the driving situation (such as turning, straight driving, grip level, road surface condition, etc.) in which the vehicle 2 is placed. The steering wheel electronic control unit controls the steering wheel torque T3 to the set control torque by a control motor (not shown). Then, the control motor exerts a control motor torque so that the steering wheel torque T3 becomes close to or equal to the set control torque.
[0084] In an embodiment, the stabilization methods 100, 200 according to the present invention can be applied to the control motor.
[0085] The rack unit has the rack 6 and at least the rack electronic control unit 20, and particularly controls the angular position P of the rack 6 c to coincide with the set angular position P tg . The set angular position P tg generally coincides with the steering wheel angle θ3, but may be changed by a function of the vehicle 2 such as the trajectory tracking function of the vehicle 2 or the parking assist function of the vehicle 2.
[0086] The rack electronic control unit 20 determines a set motor torque (set target torque in the following description) and enables the control of a pair of auxiliary motors 24, 24' that actuate motor torques T12, T12' on the rack 6. In other words, the rack electronic control unit 20 servo-controls the angular position P of the rack 6 c to the set angular position P tg by determining the set torques of the pair of motors 24, 24'.
[0087] The angular position P of the rack 6 c can be estimated from the angular positions θ12, θ12' of the respective motors 24, 24'.
[0088] Preferably, both ends of the rack 6 are respectively connected to steering rods 8 and 9 connected to the steering knuckles of the steering wheels 10 and 11 (each of the left and right wheels 10 and 11), and the longitudinal translational movement of the rack 6 can change the steering angles (yaw angles) of the steering wheels 10 and 11. The steering wheels 10 and 11 may preferably be drive wheels.
[0089] Each assist motor 24, 24' is preferably an electric motor that operates in two directions, and is preferably a brushless rotary electric motor.
[0090] Each assist motor 24, 24' can be directly engaged with the steering rack 6 by, for example, pinions 13, 13'.
[0091] Set torque C tgs is distributed to each motor 24, 24' based on, for example, the availability of each motor.
[0092] In the following description, only one of the pair of motors, motor 24, will be described. However, it is obvious that the present invention can also be applied to the other motor 24'.
[0093] FIGS. 1, 2 and 3 show a first embodiment 100, and FIG. 4 shows a second embodiment 200 of the method according to the present invention. However, for ease of reading the drawings, the same reference numerals are given to the same elements in each figure.
[0094] More specifically, the present invention relates to methods 100, 200 for stabilizing the set torque of the motor 24. As described above, the motor 24 applies a motor torque T12 to the rack 6 of the power steering system 1 of the vehicle 2 to change the angular position P c of the rack. These methods 100, 200 are executed by the rack electronic control unit 20, and at least one parameter P representing the target angular position of the rack 6 tgat least one parameter P representing the angular position of the rack 6 c and based on this, a first intermediate value C of the set torque kp including a first determination step ED1 for determining it.
[0095] The set torque refers to any quantity that enables the torque of the motor 24 to be controllable.
[0096] The parameter P representing the target angular position tg or the parameter P representing the angular position g may be the angle, the position of the rack with respect to a certain point (reference point) of the motor 24, or the angular position θ12 of the motor 24. The parameter P representing the angular position g can be determined (calculated), estimated, or measured.
[0097] In each embodiment shown in the figure, the first intermediate value C kp is obtained by calculating the difference between the parameter P particularly representing the set angular position tg and the parameter P representing the angular position g and multiplying the difference by a first gain K p . The first gain K p is hereinafter referred to as the "proportional gain". And the first intermediate value C p is obtained by performing saturation processing Sat on the integrated value of the difference and the proportional gain K kp . Therefore, "overflow" of the first intermediate value C kp does not occur, in other words, the first intermediate value C kp is limited.
[0098] The first determination step ED1 also determines the first intermediate value C of the set torque based on the speed V of the vehicle 2 kp .
[0099] More specifically, the proportional gain K p is determined by the speed V of the vehicle 2. Therefore, the proportional gain K pChanges the speed at which the vehicle's wheels follow a set angular position. At the vehicle level, this changes the accuracy with which the driver can control the steering angle of the wheels. Decreasing the proportional gain K p reduces this accuracy but improves driving comfort by filtering more frequent (higher frequency) steering wheel movements.
[0100] Vehicles often have a rack whose ratio between the set angular position and the steering angle of the wheels varies based on the vehicle speed V. In other words, at 20 km / h, the ratio of the rack is substantially direct, which means that the steering angle of the wheels changes substantially proportionally to the set angular position. The reason is that the vehicle's trajectory changes slowly. At high speeds, the ratio of the rack is less direct, which means that the steering angle of the wheels changes less than the set angular position P tg because a small change in the steering angle of the wheels causes a large snake / oscillation of the vehicle.
[0101] According to one embodiment, the proportional gain K p increases with the speed V of the vehicle 2.
[0102] Thus, at 20 km / h, for example, when the set angular position fluctuates rapidly, i.e., when the driver vibrates the steering wheel, the proportional gain K p is reduced to decrease the steering accuracy of the steering angle of the wheels but increase driving comfort.
[0103] At high speeds, such as 130 km / h, since the ratio of the rack is less direct, it is important to maintain high accuracy and thus a high proportional gain K p is maintained.
[0104] The first decision step ED1 also determines a second intermediate value C of the set torque based on at least one parameter V ctg representing the set speed of the rack 6 and a parameter V c representing the speed of the rack 6. kd
[0105] Parameter V representing the set speed of the rack ctg Or parameter V representing the speed of the rack c Is parameter P representing the set angular position tg Or parameter P representing the angular position of the rack c Can be determined based on, or is measured directly or indirectly on motor 24 or the rack.
[0106] Second intermediate value C kd In particular, is parameter V representing the set speed ctg And parameter V representing the speed of the rack c Calculate the difference between them, and multiply the difference by second gain K d To obtain. Second gain K d Is hereinafter referred to as the "differential gain".
[0107] Second intermediate value C kd Is obtained by saturation processing Sat of the integrated value of the difference and differential gain K d Therefore, "overflow" of the second intermediate value does not occur, in other words, the second intermediate value C kd Is limited.
[0108] The first determination step ED1 determines the second intermediate value C of the set torque also according to the speed V of the vehicle 2 kd To determine.
[0109] More specifically, differential gain K d May be determined by the speed V of the vehicle 2. In this way, differential gain K d Changes the speed at which the wheels of the vehicle follow the target angular position. At the level of vehicle 2, this changes the accuracy with which the driver can control the direction angle of the wheels. Differential gain K d Reduces this accuracy by reducing it, but improves driving comfort because higher frequency wheel direction movements are filtered.
[0110] According to one embodiment, differential gain K dincreases with the speed V of the vehicle 2.
[0111] Therefore, at 20 km / h, the differential gain K d decreases and the steering accuracy of the wheel direction angle deteriorates. However, in the case of a sudden change in the set angle position, for example, when the driver vibrates the steering wheel, the driving comfort improves.
[0112] At high speeds such as 130 km / h, since the ratio of the rack is not very direct, it is important to maintain the system well and thus maintain a high differential gain K d is important.
[0113] The methods 100, 200 have a second determination step ED2 for determining the limit value B kp of the first intermediate value C kpl of the set torque, B kpu based on the parameter P tg representing the set value angle position and the parameter P c representing the angle position.
[0114] The limit value B kpl , B kpu is obtained by calculating the difference between the parameter P tg representing the set angle position and the parameter P c representing the angle position, and multiplying the difference by the first limit gain B kp . The first limit gain B kp is hereinafter referred to as the "limit proportional gain".
[0115] The limit value B kpl , B kpu may be a pair of limit values having an upper limit value B kpu and a lower limit value B kpl . Alternatively, only one of the upper limit value B kpu or the lower limit value B kpl is determined, and the other upper limit value B kpu or lower limit value B kpl may be calculated by symmetry.
[0116] The second determination step ED2 is the first intermediate value C of the set torque kp of the limit value B kpl 、B kpu is determined based on the speed V of the vehicle 2. More specifically, the limit proportional gain B kp may be determined by the speed V of the vehicle 2.
[0117] The second determination step ED2 is the parameter V representing the set speed ctg and the parameter V representing the speed of the rack 6 c Based on this, the limit value B of the second intermediate value C of the set torque kd 、B kdl is also determined. kdu
[0118] The limit value B of the second intermediate value C of the set torque kd 、B kdl is calculated by calculating the difference between the parameter V kdu representing the set speed in particular ctg and the parameter V c representing the speed, and multiplying the difference by the second limit gain B kd . The second limit gain B kd is hereinafter referred to as the "limit differential gain".
[0119] The second determination step ED2 is based on the speed V of the vehicle 2, and the second intermediate value C of the set torque kd of the limit value B kdl 、B kdu is determined. More specifically, the limit differential gain B kd may be determined by the speed V of the vehicle 2.
[0120] This method has a third determination step ED3 for determining the parameter P fc 、P fi representing the average motor torque acting at the previous point in time.
[0121] The "previous point in time" refers to the target value C of the current set torque tgs means a past point in time with respect to the calculation of. The previous point in time is determined in particular by the implementation speed of the stabilization methods 100, 200. Parameter P representing the average motor torque fc , P fi By using, it becomes possible not to consider the sudden change in the motor torque T12.
[0122] Figures 2 and 4 show a first embodiment in which the parameter P representing the average motor torque acting at the previous point in time fi is determined based on the parameter P tg representing the set angular position and the parameter P c representing the angular position of the rack.
[0123] The parameter P fi representing the average motor torque is calculated in particular as the difference between the parameter P tg representing the set angular position and the parameter P c representing the angular position, and then the difference is multiplied by a gain K i referred to as the "integration gain" below.
[0124] The parameter P fi representing the average motor torque is obtained by saturation processing Sat and integration Int of the integrated value of the difference and the integration gain K i . Therefore, "overflow" of the parameter P fi representing the average motor torque does not occur, in other words, the parameter P fi representing the average motor torque is limited.
[0125] In an embodiment, the parameter P fi representing the average motor torque is determined based on the speed V of the vehicle 2. More specifically, the integration gain K i can be made to depend on the speed V of the vehicle 2.
[0126] Figure 3 shows the parameter P fcis determined based on the target value of the set torque at the previous point in time, or on a parameter C representing the motor torque acting at the previous point in time, which was directly or indirectly implemented by the rack 6 or the motor 24 mot shows a second embodiment determined based on the measured value of
[0127] More precisely, a parameter P representing the average motor torque acting at the previous point in time fc is determined by applying a low-pass filter Moy to the measured value of the target value of the set torque at the previous point in time or the parameter C representing the motor torque acting at the previous point in time mot . For example, the low-pass filter Moy is a second-order filter
[0128] Thus, the static component T12 of the acting motor torque is obtained, in other words, the rapid fluctuations of the acting motor torque are removed. The low-pass filter Moy makes it possible to obtain a kind of "average" motor torque
[0129] A parameter P representing the average motor torque acting at the previous point in time fc is obtained by multiplying the filtered target value of the set torque at the previous point in time, or the filtered measured value of the parameter C representing the motor torque acting at the previous point in time mot by a gain K, hereinafter referred to as the "static gain" s . The static gain K s is determined by the vehicle speed V
[0130] Finally, this method 100, 200 includes a stabilization step ES, in which the target value C of the set torque tgs is limited by the first intermediate value C of the set torque kp , the second intermediate value C of the set torque kd , the first intermediate value C of the set torque kp limiting value B kpl , B kpu , the second intermediate value C of the set torque kd limiting value B kdl , B kdu , and the parameter P representing the average motor torque acting at the previous point in timefi , P fc is determined based on
[0131] The target value C of the set torque tgs is the torque value that it is desirable for the motor 24 to act on the rack. This is the stabilized set torque. In other words, by the stabilization step ES, the required set torque corresponding to the target value C of the set torque tgs is guaranteed to be included in the defined interval around the parameter P fi , P c around it. Therefore, there is no large and sudden deviation from the required set torque. Therefore, an error regarding a malfunction of the controller that executes at least the first step is avoided.
[0132] In the embodiments shown in FIGS. 1, 2, and 3, the method 100 includes a first evaluation step EE1 of evaluating a provisional value (temporary value) C of the set torque based on a first intermediate value C of the set torque kp , a second intermediate value C of the set torque kd , and a parameter P representing the average motor torque acting at the previous time point fi . The first evaluation step EE1 sums the first intermediate value C of the set torque tg , the second intermediate value C of the set torque kp , and the parameter P representing the average motor torque acting at the previous time point kd . fi
[0133] This method has a limit value B tg of the provisional value C of the set torque u , B l such that the limit value B kp of the first intermediate value C of the set torque kpl , B kpu , the limit value B kd of the second intermediate value C of the set torque kdl , B kdu , and the parameter P representing the average motor torque acting at the previous time point fcalso has a second evaluation step EE2 determined based on it. More specifically, the second evaluation step EE2 is the first intermediate value C of the set torque kp of the limit value B kpl , B kpu , the second intermediate value C of the set torque kd of the limit value B kdl , B kdu , and the parameter P representing the average motor torque acting at the previous time fc are summed up.
[0134] The stabilization step is the provisional value C of the set torque tg and the provisional value C of the set torque tg of the limit value B u , B l and based on it, determines the target value C of the set torque tgs . More specifically, the stabilization step then restricts the provisional value of the set torque by the limit value of the provisional value of the set torque so that the provisional value of the set torque is included in the limit value of the provisional value.
[0135] In the embodiments shown in FIGS. 1, 2, and 3, the first determination step ED1, the third determination step ED3, and the first evaluation step EE1 are executed by the controller of the AFC position of the rack, and the second determination step ED2, the third determination step ED3, the second evaluation step EE2, and the stabilization step ES are executed by the stabilization controller AFS that receives the provisional value C of the set torque tg as an input from the controller of the AFC position in particular. Thus, the stabilization controller AFS is arranged in the subsequent stage independently of the controller of the AFC position. Therefore, on the one hand, the controller of the AFC position can be changed or adjusted independently of the stabilization controller AFS, and on the other hand, the stabilization controller AFS can be placed in a section of the electronic control unit that is more resistant to failures than the position controller AFC. Therefore, the stabilization of the set torque of the motor is guaranteed.
[0136] In the embodiment shown in FIG. 4, this method 200 is the target value C of the first intermediate value C of the set torque kp ofkps as the first intermediate value C of the set torque kp and the first intermediate value C of the set torque kp limit value B kpl , B kpu and is determined based on, and the second intermediate value C of the set torque kd target value C kds as the second intermediate value C of the set torque kd and the second intermediate value C of the set torque kd limit value B kdl , B kdu includes a first stabilization step ES1 determined based on
[0137] The first stabilization step ES1, more precisely, limits the first intermediate value C of the set torque kp by its limit value B of the first intermediate value C of the set torque kp limit value B kpl , B kpu and limits the second intermediate value C of the set torque kd by its limit value B of the second intermediate value C of the set torque kd limit value B kdl , B kdu . Therefore, the target value C of the first intermediate value C of the set torque kp target value C kps does not exceed or is equal to its limit value B of the first intermediate value C of the set torque kp limit value B kpl , B kpu and the target value C of the second intermediate value C of the set torque kd target value C kds does not exceed or is equal to its limit value B of the second intermediate value C of the set torque kd limit value B kdl , B kdu .
[0138] Next, the stabilization step ES determines the target value C of the set torque tgs based on the target value C of the first intermediate value C of the set torque kp target value C kps , the target value C of the second intermediate value C of the set torque kd target value C kds , and a parameter P representing the average motor torque acting at the previous time point fi . For example, the target value C of the set torque tgsis the first intermediate value C of the set torque kp target value C kps , the second intermediate value C of the set torque kd target value C kds , and the parameter P representing the average motor torque acting at the previous point in time fi is obtained by the sum of.
[0139] Although the present invention has been described with reference to specific embodiments, it is obvious that these examples can be modified and changed without departing from the overall scope of the invention specified by the claims. In particular, the individual features of the various embodiments illustrated / described can be combined in other embodiments. Therefore, the specification and drawings should be considered in an illustrative rather than a restrictive sense.
[0140] Also, it is obvious that all the features described with respect to the method are applicable to the apparatus alone or in combination, and conversely, all the features described with respect to the apparatus are applicable to the method alone or in combination.
Claims
1. A stabilization method (100, 200) executed by at least one controller (20), in which a motor (24, 24') applies a motor torque (T12, T12') to a device (6) of a power steering system (1) of a vehicle (2) to change the angular position of said device (6) in order to stabilize a set torque of said motor (24, 24'), the stabilization method comprising: At least one first intermediate value (C ｋｐ ) is determined by at least one parameter (P ｔｇ ) and at least one parameter (P ｃ a first determination step (ED1) based on At least one first intermediate value (C ｋｐ ) limit value (B ｋｐｌ , B ｋｐｕ ) is at least a parameter (P ｔｇ ) and at least a parameter (P ｃ a second decision step (ED2) based on A parameter (P ｆｉ , P ｆｃ a third determination step (ED3) in which the number of The target value of the set torque (C ｔｇｓ ) is at least a first intermediate value (C ｋｐ ), the first intermediate value of the set torque (C ｋｐ ) limit value (B ｋｐｌ , B ｋｐｕ ), and a parameter (P ｆｉ , P ｆｃ A stabilization step (ES) determined based on The stabilization method according to claim 1,
2. 2. The stabilization method (100, 200) of claim 1, A parameter (P ｆｉ ) is a parameter (P ｔｇ ) and at least a parameter (P ｃ ) and a stabilization method (100, 200) determined based on the
3. 2. The stabilization method (100, 200) according to claim 1, A parameter (P ｆｃ ) is the target value (C ｔｇｓ ) or a parameter (C ｍｏｔ A stabilization method (100, 200) is determined based on measurements of
4. A stabilization method (100, 200) according to claim 3, A parameter (P ｆｃ ) is the target value (C ｔｇｓ ) or a parameter (C ｍｏｔ The stabilization method (100, 200) is determined by applying a low pass filter (Moy) to the measurements of
5. A stabilization method (100, 200) according to any one of claims 1 to 4, The first determination step (ED1) determines at least one first intermediate value (C ｋｐ ) also based on the speed (V) of said vehicle (2).
6. A stabilization method (100, 200) according to any one of claims 1 to 5, The second determination step (ED2) determines at least one first intermediate value (C ｋｐ ) limit value (B ｋｐｌ , B ｋｐｕ ) based on the speed (V) of the vehicle (2).
7. The stabilization method (100) according to any one of claims 1 to 6, The provisional value of the set torque (C ｔｇ ) is at least one first intermediate value (C ｋｐ ) and a parameter (P ｆｉ , P ｆｃ a first evaluation step (EE1) in which the The provisional value of the set torque (C ｔｇ ) limit value (B ｕ , B ｌ ) is at least one first intermediate value (C ｋｐ ) limit value (B ｋｐｌ , B ｋｐｕ ) and a parameter (P ｆｉ , P ｆｃ and a second evaluation step (EE2) determined based on The stabilization step (ES) is performed to stabilize the set torque target value (C ｔｇｓ ) to at least the provisional value (C ｔｇ ) and the provisional value of the set torque (C ｔｇ ) limit value (B ｕ , B ｌ ) based on which the stabilization method (100, 200) is determined.
8. 8. The stabilization method (100) of claim 7, further comprising: The first determination step (ED1), the third determination step (ED3) and the first evaluation step (EE1) are performed by a position controller (AFC) of the device (6), and the second determination step (ED2), the third determination step (ED3), the second evaluation step (EE2) and the stabilization step (ES) are performed by receiving, in particular, the provisional value (C) of the set torque from the position controller (AFC). ｔｇ ) as input.
9. The stabilization method (200) according to any one of claims 1 to 6, At least one first intermediate value (C ｋｐ At least one target value (C ｋｐｓ ) is at least one first intermediate value (C ｋｐ ) and at least one first intermediate value (C ｋｐ ) limit value (B ｋｐｌ , B ｋｐｕ ) a first stabilization step (ES1) determined based on The stabilization step (ES) is performed to stabilize the set torque target value (C ｔｇｓ ) to at least one first intermediate value (C ｋｐ At least the target value (C ｋｐｓ ) and a parameter (P ｆｉ , P ｆｃ ) and a stabilization method (100, 200) for determining the stabilization amount based on the
10. A stabilization method (100, 200) according to any one of claims 1 to 9, The first determination step (ED1) comprises determining at least one parameter (V ｃｔｇ ) and a parameter (V ｃ ) and the second intermediate value (C ｋｄ ) and said second determination step (ED2) also determines a parameter (V ｃｔｇ ) and a parameter (V ｃ ) based on the second intermediate value (C ｋｄ ) limit value (B ｋｄｌ , B ｋｄｕ ) is also determined.
11. A vehicle (2) equipped with a power steering system (1) of the type without mechanical linkage, in which a stabilization method (100, 200) according to any one of claims 1 to 10 is implemented.