Method for securing setpoint torque of motor of power steering system
By calculating multiple intermediate values and limit values of set point torque in the power steering system, and combining the parameters of the average motor torque, the target set point torque value is determined, and the problem of inability to distinguish the source of faults in the prior art is solved, and precise control and fault identification of the power steering system are achieved.
Patent Information
- Application Number
- CN202411838404.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-13
- Filing Date
- 2024-12-13
- Publication Date
- 2025-06-13
AI Technical Summary
The prior art cannot effectively distinguish the source of faults between the rack angular position and the set point angular position in a power steering system, resulting in the inability to determine whether the difference is caused by a controller failure or other reasons.
By determining multiple intermediate and limit values of set point torque, and combining parameters of average motor torque applied at previous moments, the target set point torque value is calculated to ensure correct operation of the controller and identification of the fault source.
Accurate control of set point torque in the power steering system is achieved, misjudgment caused by controller failure is avoided, and the system's robustness and fault recognition ability are improved.
Smart Images
Figure CN120135262A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of vehicles including a power steering system, and more particularly to a method for ensuring a setpoint torque of a motor. Background Art
[0002] The purpose of a vehicle's steering system is to allow the driver to control the vehicle's trajectory by changing the orientation angle of the vehicle's wheels by means of the steering wheel. The driver changes the angle of the steering wheel by applying a force to it.
[0003] Generally, the steering system includes a plurality of elements, which include the steering wheel, a rack, and two wheels each connected to a connecting rod. The rack is a component that allows the wheels to be maneuvered, that is, allows the orientation angle of the wheels to be changed via the connecting rod. The angular position of the rack relative to the steering housing (hereinafter referred to as the rack angular position) is an image of the orientation angle of the wheels.
[0004] In an electric power steering system without a mechanical connection, called "steer-by-wire", the steering wheel is mechanically detached from the rack. In this case, the steering system includes 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 includes the steering wheel and at least one device for estimating the angle of the steering wheel, such as an angle sensor.
[0006] The rack unit includes the rack that is movable in the steering housing and at least one electronic control unit that specifically controls the angular position of the rack so that it coincides with a setpoint angular position. The setpoint angular position generally coincides with the steering wheel angle, but it can be changed by vehicle functions such as a trajectory tracking function or a vehicle parking assistance function.
[0007] The electronic control unit determines a setpoint motor torque (or setpoint torque in the remainder of this description) to control at least one motor that applies a motor torque to the rack. In other words, the controller servo-controls the angular position of the rack at the setpoint angular position by determining the setpoint torque of the motor.
[0008] Ensuring the correct operation of the controller, and more particularly the control of the position of the rack, so as to allow ensuring the consistency between the setpoint angular position and the rack angular position is important for guaranteeing the safety of the vehicle.
[0009] There are known solutions that allow the detection of faults in a rack unit. A fault in the rack unit is defined as the difference between the rack angular position and the setpoint angular position. When a fault is detected, the servo control is then carried out by a backup controller.
[0010] The drawback of this solution is that it is unable to identify the source of the fault. Thus, it is impossible to determine whether the difference between the rack angular position and the setpoint angular position is due to a controller fault or, for example, due to other reasons such as wheel jamming.
[0011] Therefore, there is a need to ensure the controller more efficiently. SUMMARY OF THE INVENTION
[0012] An embodiment relates to a method for ensuring a setpoint torque of a motor that applies a motor torque to a device of a vehicle's power steering system to change the angular position of the device. The method is carried out by at least one controller and includes:
[0013] - A first determination step, in which at least one first intermediate value of the setpoint torque is determined based on at least one parameter representing the setpoint angular position of the device and at least one parameter representing the angular position of the device;
[0014] - A second determination step, in which a limit value of at least one first intermediate value of the setpoint torque is determined based on at least one parameter representing the setpoint angular position and at least one parameter representing the angular position;
[0015] - A third determination step, in which a parameter representing the average motor torque applied at a previous moment is determined;
[0016] - An ensuring step, in which a target value of the setpoint torque is determined based on at least one first intermediate value of the setpoint torque, the limit value of the first intermediate value of the setpoint torque, and the parameter representing the average motor torque applied at a previous moment.
[0017] The controller can be an electronic control unit.
[0018] The setpoint torque refers to any quantity representing the setpoint torque such that the torque of the motor can be controlled.
[0019] In some embodiments, the device to which the motor applies the motor torque is a rack of a vehicle's power steering system.
[0020] In some embodiments, the power steering system belongs to the type without mechanical linkage.
[0021] The first step determines at least one first intermediate value of the setpoint torque. In other words, in some embodiments, the setpoint torque can be determined based on a plurality of intermediate values.
[0022] The first intermediate value is determined based on at least one parameter representing the target angular position of the device and at least one 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 point of the motor, or the angular position of the motor. The parameter representing the angular position can be determined, estimated, or measured.
[0023] In some embodiments, the first intermediate value is specifically obtained by calculating the difference between the parameter representing the target angular position and the parameter representing the angular position, and then multiplying the difference by a first gain. The first gain is subsequently referred to as the "proportional gain".
[0024] In some embodiments, the first intermediate value is obtained by saturating the product of the difference and the proportional gain. Thus, the first intermediate value does not "overflow", that is, the first intermediate value is limited.
[0025] In some embodiments, the first determination step also determines at least one first intermediate value of the setpoint torque based on the speed of the vehicle.
[0026] More particularly, the proportional gain can depend on the speed of the vehicle.
[0027] Thus, the proportional gain changes the speed at which the vehicle wheels will follow the setpoint angular position. At the vehicle level, this changes the precision with which the driver can control the wheel orientation angle. By reducing the proportional gain, this precision is reduced but driving comfort is increased because it filters out higher frequency wheel orientation movements.
[0028] The vehicle is typically equipped with a rack that has a variable ratio between the setpoint angular position and the wheel orientation angle depending on the vehicle speed. In other words, at 20 km / h, the rack ratio is substantially direct, that is, the wheel orientation angle varies substantially proportionally to the setpoint angular position because the vehicle's trajectory changes slowly. At high speeds, the rack ratio is not very direct, that is, the change in the wheel orientation angle is less than the setpoint angular position because the slightest change in the wheel orientation angle would cause the vehicle to deviate / shake significantly.
[0029] According to an embodiment, the proportional gain increases with the vehicle speed.
[0030] Thus, at 20 km / h, the proportional gain is reduced in order to reduce the steering precision of the wheel orientation angle but increase driving comfort, for example in the case of a rapid change in the setpoint angular position, that is, if the driver wiggles the steering wheel.
[0031] At high speeds (e.g., 130 km / h), the rack ratio is not very direct, so it is important to maintain good precision and thus maintain a significant proportional gain.
[0032] The second step determines the limit value of at least one first intermediate value of the setpoint torque. When multiple intermediate values are determined, the second step determines multiple limit values. In other words, for each intermediate value determined by the first determination step, the second determination step determines the limit value.
[0033] In some embodiments, the limit value is specifically obtained by calculating the difference between the parameter representing the setpoint angular position and the parameter representing the angular position, and then multiplying the difference by a first limit gain. The first limit gain is subsequently referred to as the "limit proportional gain".
[0034] The limit value can be a pair of limit values including an upper limit value and a lower limit value. Alternatively, only one of the upper limit value or the lower limit value can be determined, and the other of the upper limit value or the lower limit value is calculated by symmetry.
[0035] In some embodiments, the second determination step determines the limit value of at least one first intermediate value of the setpoint torque according to the vehicle speed.
[0036] More particularly, the limit proportional gain can depend on the vehicle speed.
[0037] The third step determines the parameter representing the average motor torque applied at a previous moment.
[0038] The term "previous moment" means a past moment with respect to the calculation of the target value of the current setpoint torque. The previous moment specifically depends on the speed at which the method is implemented.
[0039] Finally, the ensuring step combines at least one first intermediate value of the setpoint torque, the limit value of at least one first intermediate value of the setpoint torque, and the parameter representing the average motor torque applied at a previous moment in order to determine the target value of the setpoint torque.
[0040] The parameter representing the average motor torque can be obtained in various ways, such as through a low-pass filter. Using the parameter representing the average motor torque makes it possible to ignore the rapid changes in the motor torque.
[0041] The target value of the setpoint torque is the torque value that we want the motor to apply to the device. This is the setpoint torque to be ensured. In other words, the ensuring step makes it possible to guarantee that the requested setpoint torque corresponding to the target value of the setpoint torque is included in the defined interval around the parameter representing the average motor torque applied at a previous moment. In other words, there is a framework for the target value of the setpoint torque. Therefore, there is no significant and sudden deviation from the requested setpoint torque. Therefore, errors related to the failure of the controller implementing at least the first step are avoided, or the impact of the failure is limited, without switching to another regulation strategy (such as a backup law) or another controller.
[0042] In some embodiments, a parameter representing the average motor torque applied at a previous moment is determined based on at least one parameter representing a setpoint angular position and at least one parameter representing the angular position of the device.
[0043] One of the methods for determining the parameter representing the average motor torque is to use at least one parameter representing the setpoint angular position and at least one parameter representing the angular position of the device.
[0044] In some embodiments, the parameter representing the average motor torque is specifically obtained by calculating the difference between the parameter representing the setpoint angular position and the parameter representing the angular position, and then multiplying the difference by a gain (subsequently referred to as the "integral gain").
[0045] In some embodiments, the parameter representing the average motor torque is obtained by saturating and integrating the product of the difference and the integral gain. Thus, the parameter representing the average motor torque does not "overflow", that is, the parameter representing the average motor torque is limited.
[0046] In some embodiments, the parameter representing the average motor torque applied at a previous moment is determined based on at least the vehicle speed.
[0047] More particularly, the integral gain can depend on the vehicle speed.
[0048] In some embodiments, the parameter representing the average motor torque applied at a previous moment is determined based on the target value of the setpoint torque at the previous moment or the measured value of the parameter representing the motor torque applied at the previous moment.
[0049] The measured value of the applied motor torque can be made directly or indirectly on the device or the motor.
[0050] In some embodiments, the parameter representing the average motor torque applied at a previous moment is determined by applying a low-pass filter to the target value of the setpoint torque at the previous moment or the measured value of the parameter representing the motor torque applied at the previous moment.
[0051] In some embodiments, the low-pass filter is second-order.
[0052] Thus, the static part of the applied motor torque is obtained, that is, the rapid changes of the applied motor torque are eliminated. The low-pass filter enables the obtaining of an "average" motor torque.
[0053] In some embodiments, the parameter representing the average motor torque applied at a previous moment is obtained by multiplying the filtered target value of the setpoint torque at the previous moment or the filtered measured value of the parameter representing the motor torque applied at the previous moment by a gain subsequently referred to as the "static gain".
[0054] In some embodiments, the static gain depends on the vehicle speed.
[0055] In some embodiments, the ensuring method comprises:
[0056] - A first evaluation step, wherein a provisional value of the setpoint torque is evaluated based on at least one first intermediate value of the setpoint torque and a parameter representing the average motor torque applied at a previous moment, and
[0057] - A second evaluation step, wherein a limit value of the provisional value of the setpoint torque is determined based on a limit value of at least one first intermediate value of the setpoint torque and a parameter representing the average motor torque applied at a previous moment;
[0058] The ensuring step determines a target value of the setpoint torque based on at least one provisional value of the setpoint torque and the limit value of the provisional value of the setpoint torque.
[0059] For example, the first evaluation step sums at least one first intermediate value of the setpoint torque with a parameter representing the average motor torque applied at a previous moment. In other words, if multiple intermediate values are determined, the first evaluation step sums the multiple intermediate values of the setpoint torque with a parameter representing the average motor torque applied at a previous moment.
[0060] For example, the second evaluation step sums the limit value of the first intermediate value of the setpoint torque with a parameter representing the average motor torque applied at a previous moment. In other words, if multiple intermediate values are determined, and thus if multiple limit values are determined, the second evaluation step sums the multiple limit values with a parameter representing the average motor torque applied at a previous moment.
[0061] The ensuring step then performs a limitation of the provisional value of the setpoint torque by the limit value of the provisional value of the setpoint torque such that the provisional value of the setpoint torque is included within the limit value of the provisional value.
[0062] In some embodiments, the first determination step, the third determination step, and the first evaluation step are performed by a position controller of the device, and the second determination step, the third determination step, the second evaluation step, and the ensuring step are performed by an ensuring controller which specifically receives the provisional value of the setpoint torque of the position controller as an input.
[0063] Thus, the ensuring controller is positioned independently and after the position controller. Thus, on the one hand, it is possible to change or adjust the position controller independently of the ensuring controller, and on the other hand, it is possible to position the ensuring controller in a partition of the electronic control unit which is more robust to faults than the position controller. Thus, the setpoint torque of the motor is ensured.
[0064] In some embodiments, the method comprises:
[0065] - A first ensuring step, in which at least one target value of at least one first intermediate value of the setpoint torque is determined based on at least one first intermediate value of the setpoint torque and a limit value of at least one first intermediate value of the setpoint torque;
[0066] The ensuring step determines the target value of the setpoint torque based on at least one target value of at least one first intermediate value of the setpoint torque and a parameter representing the average motor torque applied at a previous moment.
[0067] The first ensuring step includes, for example, limiting at least one first intermediate value of the setpoint torque by a limit value of at least one first intermediate value of the setpoint torque. Thus, the target value of at least one first intermediate value of the setpoint torque is at most or at least equal to the limit value of at least one first intermediate value of the setpoint torque.
[0068] In the case where a plurality of intermediate values are determined, each intermediate value is limited by an appropriate limit value.
[0069] The ensuring step determines the target value of the setpoint torque based on at least one target value of at least one first intermediate value of the setpoint torque and a parameter representing the average motor torque applied at a previous moment.
[0070] For example, the target value of the setpoint torque is obtained by summing at least one target value of at least one first intermediate value of the setpoint torque and a parameter representing the average motor torque applied at a previous moment. In the case where a plurality of target values of a plurality of intermediate values have been determined, the target value of the setpoint torque is obtained by summing all the target values of the intermediate values and a parameter representing the average motor torque applied at a previous moment.
[0071] In some embodiments, the first determining step further determines a second intermediate value of the setpoint 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 determining step further determines a limit value of the second intermediate value of the setpoint torque based on at least one parameter representing the target speed of the device and a parameter representing the speed of the device.
[0072] The parameter representing the setpoint speed of the device or the parameter representing the speed of the device can be determined based on the parameter representing the setpoint angular position or the parameter representing the angular position of the device, or can be measured directly or indirectly on the motor or the device.
[0073] In some embodiments, the second intermediate value is specifically obtained by calculating the difference between the parameter representing the setpoint speed and the parameter representing the speed of the device, and then multiplying the difference by a second gain. The second gain is subsequently referred to as the "derived gain".
[0074] In some embodiments, the second intermediate value is obtained by saturating the product of the difference and the derived gain. Thus, the second intermediate value does not "overflow", that is, the second intermediate value is limited.
[0075] In some embodiments, the first determining step further determines a second intermediate value of the setpoint torque based on the vehicle speed.
[0076] More particularly, the derived gain can depend on the speed of the vehicle.
[0077] Thus, the derived gain changes the speed at which the vehicle wheels will follow the setpoint angular position. At the vehicle level, this changes the precision with which the driver can control the wheel orientation angle. By reducing the derived gain, this precision is reduced but driving comfort is increased because it filters out higher frequency wheel orientation movements.
[0078] According to an embodiment, the derived gain increases with the vehicle speed.
[0079] Thus, at 20 km / h, the derived gain is reduced in order to reduce the precision of the control of the wheel orientation angle but to increase driving comfort, for example in the case of rapid changes in the setpoint angular position, that is, if the driver wiggles the steering wheel.
[0080] At high speeds (e.g. 130 km / h), the rack ratio is not very direct, so it is important to maintain good precision and thus maintain a high derived gain.
[0081] In some embodiments, the limit value of the second intermediate value of the setpoint torque is specifically obtained by calculating the difference between the parameter representing the setpoint speed and the parameter representing the speed, and then multiplying this difference by a second limit gain. This second limit gain is subsequently referred to as the "limit derived gain".
[0082] In some embodiments, the second determining step determines the limit value of the second intermediate value of the setpoint torque based on the vehicle speed.
[0083] More particularly, the limit derived gain can depend on the vehicle speed.
[0084] Another aspect of the invention relates to a vehicle comprising a power steering system of the non-mechanical linkage type implementing the ensuring method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0085] The invention will be better understood from the following description, which relates to several embodiments according to the invention, given as non-limiting examples and explained with reference to the schematic drawings, in which:
[0086] Figure 1is a schematic representation of a first embodiment of the present invention;
[0087] Figure 2 is a schematic representation of a first part of the first embodiment;
[0088] Figure 3 is a schematic representation of a second part of the first embodiment;
[0089] Figure 4 is a schematic representation of a second embodiment;
[0090] Figure 5 is a schematic representation of a vehicle including a power steering system without a mechanical linkage. Detailed Description
[0091] Only the elements necessary for understanding the present invention are shown.
[0092] The present invention relates to a method 100, 200 for ensuring a setpoint torque for a pair of auxiliary motors 24, 24' of a power steering system 1 for a vehicle 2, and more particularly for a motor vehicle 2 intended to transport persons.
[0093] In a manner known per se, and as can be seen from Figure 5 the power steering system 1 includes a steering wheel 3 to which the driver can apply a force, called "steering wheel torque" T3. The angle θ3 of the steering wheel 3 is measured by an angle sensor 23.
[0094] The steering wheel torque T3 and the angle θ3 of the steering wheel are transmitted to an electronic rack control unit 20.
[0095] The steering wheel 3 is not mechanically connected to the steering rack 6 which is itself translationally guided in a steering housing 7 fixed to the vehicle 2. In other words, the steering wheel 3 is mechanically detached from the steering rack 6. In this case, the steering system 1 includes a steering wheel unit that is mechanically independent of the rack unit. In other words, 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 belongs to the "no mechanical linkage" or "steer-by-wire" type.
[0096] The steering wheel unit includes the steering wheel 3 and at least one electronic steering wheel control unit (not shown), which specifically determines the torque felt by the driver during the manipulation of the steering wheel 3, hereinafter referred to as the setpoint control torque. The setpoint control torque is specifically intended to make the driver feel torque information consistent with the actual situation of the vehicle 2 (turning, straight driving, grip level, road surface condition, etc.). The electronic steering wheel control unit controls the steering wheel torque T3 to the setpoint control torque by means of a control motor (not shown). The control motor then applies a control motor torque such that the steering wheel torque T3 approaches or is equal to the setpoint control torque.
[0097] In some embodiments, the ensuring methods 100, 200 according to the present invention can be applied to the control motor.
[0098] The rack unit includes the rack 6 and at least one electronic rack control unit 20, which specifically controls the angular position P of the rack 6 c , such that it is consistent with the setpoint angular position P tg . The setpoint angular position P tg is generally consistent with the steering wheel angle θ3, but it can be changed by functions of the vehicle 2 (such as the trajectory tracking function or the parking assistance function of the vehicle 2).
[0099] The electronic rack control unit 20 determines the setpoint motor torque (or the setpoint torque in the remainder of this description) such that a pair of auxiliary motors 24, 24' can be controlled to apply motor torques T12, T12' to the rack 6. In other words, the electronic rack control unit 20 servo-controls the angular position P of the rack 6 c to the setpoint angular position P tg .
[0100] The angular position P of the rack 6 c can be derived from the angular positions θ12, θ12' of each of the motors 24, 24'.
[0101] Preferably, the ends of the rack 6 are respectively connected to the steering rods 8, 9, which are connected to the steering knuckles of the steering wheels 10, 11 (the left wheel 10 and the right wheel 11 respectively), such that the longitudinal translational movement of the rack 6 can change the steering angles (yaw angles) of the steering wheels 10, 11. The steering wheels 10, 11 can also preferably be drive wheels.
[0102] Each auxiliary motor 24, 24' will preferably be an electric motor with two operating directions, and preferably a brushless type rotary electric motor.
[0103] Each auxiliary motor 24 , 24 ′ can be coupled directly to the steering rack 6 , for example by means of a gearwheel 13 , 13 ′.
[0104] For set point torque C tgs The distribution to each of the motors 24 , 24 ′ is carried out, for example, as a function of the availability of each of these motors.
[0105] In the remainder of the description, reference will be made to only one motor 24 of the pair of motors. However, it is obvious that the invention can also be applied to the other motor 24'.
[0106] Figure 1 , Figure 2 and Figure 3 A first embodiment 100 of the method according to the invention is shown, and Figure 4 A second embodiment 200 of the method according to the invention is shown. However, in order to facilitate the reading of the drawings, identical elements have the same reference numerals from one figure to another.
[0107] The invention more particularly relates to a method 100, 200 for ensuring a setpoint torque of a motor 24. As described above, the motor 24 applies a motor torque T12 to a rack 6 of a power steering system 1 of a vehicle 2 in order to change the angular position P of the rack. c The method 100, 200 is executed by the electronic rack control unit 20 and comprises a first determination step ED1 in which a first intermediate value C of the setpoint torque is set. kp According to the target angular position P of the rack 6 tg At least one parameter and represents the angular position P of the rack 6 c is determined by at least one parameter of
[0108] The set point torque refers to any quantity representing a set point torque, such that the torque of the motor 24 can be controlled.
[0109] represents the target angular position P tg Parameters or angular position P g The parameter of may be an angle, a position of a point of the rack relative to the motor 24, or an angular position θ12 of the motor 24. A parameter representing the angular position P may be determined, estimated, or measured. g Parameters.
[0110] In each of the embodiments shown in the figure, the first intermediate value C kp Specifically, the set point angular position P is expressed by calculating tg The parameters and the angular position P g The difference of the parameters is then multiplied by the first gain K p To obtain the first gain K pSubsequently, it is referred to as "proportional gain". Then, the first intermediate value C kp is obtained by implementing saturation Sat of the product of this difference and the proportional gain K p . Thus, the first intermediate value C kp has no "overflow", that is to say, the first intermediate value C kp is limited.
[0111] The first determination step ED1 also determines the first intermediate value C of the setpoint torque according to the speed V of the vehicle 2 kp .
[0112] More particularly, the proportional gain K p depends on the speed V of the vehicle 2. Thus, the proportional gain K p changes the speed at which the vehicle wheels will follow the setpoint angular position. At the vehicle level, this changes the precision with which the driver can control the wheel orientation angle. By reducing the proportional gain K p , the precision is reduced but the driving comfort is improved because it filters out higher frequency wheel orientation movements.
[0113] The vehicle is generally equipped with a rack which has a variable ratio between the setpoint angular position and the wheel orientation angle depending on the vehicle speed V. In other words, at 20 km / h, the rack ratio is substantially direct, that is to say, the wheel orientation angle changes substantially proportionally to the setpoint angular position because the vehicle's trajectory changes slowly. At high speeds, the rack ratio is not very direct, that is to say, the change in the wheel orientation angle is less than the setpoint angular position P tg because the slightest change in the wheel orientation angle would cause the vehicle to deviate / shake significantly.
[0114] According to an embodiment, the proportional gain K p increases with the speed V of the vehicle 2.
[0115] Thus, at 20 km / h, the proportional gain K p is reduced in order to reduce the steering precision of the wheel orientation angle but improve the driving comfort, for example in the case of a rapid change in the setpoint angular position, that is to say if the driver wiggles the steering wheel.
[0116] At high speeds (for example 130 km / h), the rack ratio is not very direct, so it is important to maintain good precision and thus maintain a high proportional gain K p .
[0117] The first determination step ED1 also determines the second intermediate value C of the setpoint torque according to at least one parameter representing the setpoint speed V ctg of the rack 6 and a parameter representing the speed V c of the rack 6. kd .
[0118] represents the setpoint speed V of the rack ctg parameter or represents the speed V of the rack c parameter can be determined on the basis of the parameter representing the setpoint angular position P of the rack tg or the angular position P of the rack, or can be measured directly or indirectly on the motor 24 or the rack c
[0119] The second intermediate value C kd Specifically, by calculating the difference between the parameter representing the setpoint speed V of the rack ctg and the parameter representing the speed V of the rack c and then multiplying this difference by the second gain K d to obtain. The second gain K d is subsequently referred to as the "derived gain".
[0120] The second intermediate value C kd is obtained by applying saturation Sat to the product of this difference and the derived gain K d . Thus, the second intermediate value does not "overflow", that is, the second intermediate value C kd is limited
[0121] The first determination step ED1 also determines a second intermediate value C of the setpoint torque based on the speed V of the vehicle 2 kd .
[0122] More particularly, the derived gain K d can depend on the speed V of the vehicle 2. Thus, the derived gain K d changes the speed at which the vehicle wheels will follow the setpoint angular position. At the vehicle 2 level, this changes the precision with which the driver can control the wheel orientation angle. By reducing the derived gain K d , this precision is reduced but driving comfort is increased because it filters out higher frequency wheel orientation movements
[0123] According to one embodiment, the derived gain K d increases with the vehicle 2 speed V
[0124] Thus, at 20 km / h, the derived gain K d is reduced in order to reduce the precision of the steering of the wheel orientation angle but increase driving comfort, for example in the case of rapid changes in the setpoint angular position, that is, if the driver wiggles the steering wheel
[0125] At high speeds (e.g. 130 km / h), the rack ratio is not very direct, so it is important to maintain good precision and thus maintain a high derived gain K d .
[0126] The methods 100, 200 include: a second determination step ED2, in which a first intermediate value C of the setpoint torque is set kp limit value B kpl , B kpu is determined based on a parameter representing the setpoint angular position P tg and a parameter representing the angular position P c .
[0127] Limit value B kpl , B kpu Specifically, by calculating the difference between a parameter representing the setpoint angular position P tg and a parameter representing the angular position P c , and then multiplying the difference by a first limit gain B kp to obtain. The first limit gain B kp is subsequently referred to as the "limit proportional gain".
[0128] Limit value B kpl , B kpu can be a pair of limit values including an upper limit value B kpu and a lower limit value B kpl . Alternatively, only the upper limit value B kpu or the lower limit value B kpl can be determined, and the upper limit value B kpu or the lower limit value B kpl of the other can be calculated by symmetry.
[0129] The second determination step ED2 determines the limit value B kp of the first intermediate value C of the setpoint torque based on the vehicle 2 speed V kpl , B kpu . More particularly, the limit proportional gain B kp can depend on the vehicle 2 speed V.
[0130] The second determination step ED2 also determines the limit value B ctg of the second intermediate value C of the setpoint torque based on a parameter representing the setpoint speed V c and a parameter representing the speed V of the rack 6 kd . kdl , B kdu .
[0131] The limit value B kd of the second intermediate value C of the setpoint torque kdl , B kdu is specifically obtained by calculating the difference between a parameter representing the setpoint speed V ctg and a parameter representing the speed V cthe difference between the parameters, and then by multiplying the difference by a second limit gain B kd is obtained. The second limit gain B kd is subsequently referred to as the "limit-derived gain".
[0132] A second determination step ED2 determines a second intermediate value C of the setpoint torque as a function of the vehicle 2 speed V kd of the limit value B kdl 、B kdu . More particularly, the limit-derived gain B kd may depend on the vehicle 2 speed V
[0133] The method includes: a third determination step ED3 in which a parameter P representing the average motor torque applied at a previous moment is determined fc 、P fi .
[0134] The previous moment is understood to mean a past moment with respect to the calculation of the target value C of the current setpoint torque tgs . The previous moment depends in particular on the speed at which the methods 100, 200 are implemented. The use of the parameter representing the average motor torque P fc 、P fi makes it possible to disregard rapid variations in the motor torque T12
[0135] Figure 2 and Figure 4 shows a first embodiment in which the parameter representing the average motor torque P fi applied at a previous moment is determined as a function of the parameter representing the setpoint angular position P tg of the rack and of the parameter representing the angular position P c of the rack
[0136] The parameter representing the average motor torque P fi is obtained more particularly by calculating the difference between the parameter representing the setpoint angular position P tg and the parameter representing the angular position P c of the rack and then multiplying the difference by a gain K i which is subsequently referred to by the term "integration gain".
[0137] The parameter representing the average motor torque P fi is obtained by implementing saturation Sat and integration Int on the product of the difference and the integration gain K i . Thus, the parameter representing the average motor torque P fi does not "overflow", that is to say the parameter representing the average motor torque P fi is limited
[0138] In some embodiments, the parameter representing the average motor torque P fi is determined as a function of the vehicle 2 speed V. More particularly, the integral gain K i may depend on the vehicle 2 speed V.
[0139] Figure 3 A second embodiment is shown, in which the parameter representing the average motor torque P fc applied at the previous moment is determined as a function of the target value of the setpoint torque at the previous moment or as a function of the measured value C mot of the parameter representing the motor torque applied at the previous moment, this measured value being taken directly or indirectly on the rack 6 or on the motor 24.
[0140] More precisely, the parameter P fc representing the average motor torque applied at the previous moment is determined by applying a low-pass filter Moy to the target value of the setpoint torque at the previous moment or to the measured value C mot of the parameter representing the motor torque applied at the previous moment. For example, this low-pass filter Moy is second order.
[0141] Thus, a static part T12 of the applied motor torque is obtained, that is to say the rapid variations of the applied motor torque are eliminated. The low-pass filter Moy makes it possible to obtain an "average" motor torque.
[0142] The parameter representing the average motor torque P fc applied at the previous moment is obtained by multiplying the filtered target value of the setpoint torque at the previous moment or the filtered measured value Cmot of the parameter representing the motor torque applied at the previous moment by a gain K s subsequently referred to as "static gain". The static gain K s depends on the vehicle 2 speed V.
[0143] Finally, the methods 100, 200 comprise: ensuring a step ES in which the target value C tgs of the setpoint torque is determined as a function of a first intermediate value C kp of the setpoint torque, a second intermediate value C kd of the setpoint torque, the limit value B kp of the first intermediate value C kpl of the setpoint torque, B kpu the limit value B kd of the second intermediate value C kdl of the setpoint torque, B kdu and the parameter representing the average motor torque P fi applied at the previous moment, P fc .
[0144] The target value C of the setpoint torquetgs is the torque value that the motor 24 is expected to apply to the rack. This is the setpoint torque to be ensured. In other words, the ensuring step ES enables the guarantee that the requested setpoint torque corresponding to the target value C tgs of the setpoint torque is included within the defined interval around the parameter representing the average motor torque P fi 、P c applied at the previous moment. Thus, there is no significant and sudden deviation from the requested setpoint torque. Therefore, errors related to the malfunction of the controller implementing at least the first step are avoided.
[0145] In Figure 1 、 Figure 2 and Figure 3 the embodiment shown, the method 100 includes a first evaluation step EE1, in which the provisional value C kp of the setpoint torque is evaluated based on the first intermediate value C kd of the setpoint torque, the second intermediate value C fi of the setpoint torque, and the parameter representing the average motor torque P tg applied at the previous moment. The first evaluation step EE1 sums the first intermediate value C kp of the setpoint torque, the second intermediate value C kd of the setpoint torque, and the parameter representing the average motor torque P fi applied at the previous moment.
[0146] The method further includes a second evaluation step EE2, in which the limit values B kp 、B kpl 、B kpu of the first intermediate value C kd of the setpoint torque, the limit values B kdl 、B kdu of the second intermediate value C fc of the setpoint torque, and the parameter representing the average motor torque P tg are used to determine the limit values B u 、B l of the provisional value C kp of the setpoint torque. More specifically, the second evaluation step EE2 sums the limit values B kpl 、B kpu of the first intermediate value C kd of the setpoint torque, the limit values B kdl 、B kdu of the second intermediate value C fc of the setpoint torque, and the parameter representing the average motor torque P
[0147] The ensuring step is based on the provisional value C tgand the limit value B of the temporary value C of the setpoint torque tg of the limit value B u 、B l to determine the target value C of the setpoint torque tgs . More precisely, the ensuring step then performs a limit on the temporary value of the setpoint torque by means of the limit value of the temporary value of the setpoint torque, such that the temporary value of the setpoint torque is included within the limit value of the temporary value.
[0148] Figure 1 、 Figure 2 and Figure 3 The embodiments shown allow the first determination step ED1, the third determination step ED3, and the first evaluation step EE1 to be performed by a controller in the AFC position of the rack, and the second determination step ED2, the third determination step ED3, the second evaluation step EE2, and the ensuring step ES to be performed by an ensuring controller AFS, which specifically receives the temporary value C of the setpoint torque from the controller in the AFC position tg as an input. Thus, the ensuring controller AFS is positioned independently and after the controller is in the AFC position. Thus, on the one hand, it is possible to change or adjust the AFC position controller independently of the ensuring controller AFS, and on the other hand, it is possible to position the ensuring controller AFS in a partition of the electronic control unit that is more robust to faults than the position controller AFC. Thus, the setpoint torque of the motor is ensured.
[0149] In Figure 4 the embodiment shown, the method 200 includes: a first ensuring step ES1, in which a target value C of the first intermediate value C of the setpoint torque is determined according to the first intermediate value C of the setpoint torque kp and the limit value B of the first intermediate value C of the setpoint torque kp of the limit value B kpl 、B kpu to determine the target value C of the first intermediate value C of the setpoint torque kp ,and a target value C of the second intermediate value C of the setpoint torque is determined according to the second intermediate value C of the setpoint torque kps and the limit value B of the second intermediate value C of the setpoint torque kd and the second intermediate value C of the setpoint torque kd of the limit value B kdl 、B kdu to determine the target value C of the second intermediate value C of the setpoint torque kd , kds ,
[0150] The first ensuring step ES1 more precisely includes limiting the first intermediate value C of the setpoint torque by means of the limit value B kp of the first intermediate value C of the setpoint torque kpl 、B kpu ,and limiting the first intermediate value C of the setpoint torque by means of the limit value B kp of the second intermediate value C of the setpoint torque kdThe limit value B kdl , B kdu to limit the second intermediate value C of the setpoint torque kd . Thus, the first intermediate value C of the setpoint torque kp the target value C kps is at most or at least equal to the first intermediate value C of the setpoint torque kp the limit value B kpl , B kpu , and the second intermediate value C of the setpoint torque kd the target value C kds is at most or at least equal to the second intermediate value C of the setpoint torque kd the limit value B kdl , B kdu .
[0151] Then, ensure that step ES is based on the first intermediate value C of the setpoint torque kp the target value C kps , the second intermediate value C of the setpoint torque kd the target value C kds and a parameter representing the average motor torque P applied at a previous time fi to determine the target value C of the setpoint torque tgs . For example, the target value C of the setpoint torque tgs is obtained by the sum of the target value C of the first intermediate value C of the setpoint torque kp , the target value C of the second intermediate value C of the setpoint torque kps , and a parameter representing the average motor torque P applied at a previous time kd the target value C kds fi .
[0152] Although the present invention has been described with reference to specific embodiments, it is apparent that these examples can be changed and modified without departing from the overall scope of the invention as defined by the claims. Specifically, the various features of the illustrated / mentioned embodiments can be combined in additional embodiments. Therefore, the description and the drawings should be considered in an illustrative rather than a restrictive sense.
[0153] It is also apparent that all features described with reference to the method can be transferred to the apparatus, either individually or in combination, and conversely, all features described with reference to the apparatus can be transferred to the method, either individually or in combination.
Claims
1. A method (100, 200) for ensuring a set point torque of a motor (24, 24') which applies a motor torque (T12, T12') to a device (6) of a power steering system (1) of a vehicle (2) in order to change the angular position of the device (6), the method being executed by at least one controller (20) and comprising: - a first determination step (ED1) in which a target angular position (P tg ) and at least one parameter representing the angular position (P c ) to determine at least one first intermediate value (C kp ); - a second determination step (ED2) in which the setpoint angular position (P tg ) and represents the angular position (P c ) to determine at least one first intermediate value (C kp ) limit value (B kpl , B kpu ); - a third determination step (ED3) in which a value representing the average motor torque applied at the previous moment (P fi , P fc ) parameters; - a step of ensuring (ES) in which, according to at least one first intermediate value (C kp ), the first intermediate value of the set point torque (C kp ) limit value (B kpl , B kpu ) and represents the average motor torque applied at the previous moment (P fi , P fc ) parameter to determine the target value of the set point torque (C tgs ).
2. The ensuring method (100, 200) according to claim 1, wherein: represents the average motor torque applied at the previous moment (P fi ) is a parameter representing the set point angular position (P tg ) and at least one parameter representing the angular position (P c ) is determined by at least one parameter of 3. The ensuring method (100, 200) according to claim 1, wherein: represents the average motor torque applied at the previous moment (P fc ) is based on the target value of the set point torque at the previous moment (C tgs ) or based on a measurement of a parameter representing the motor torque applied at a previous moment (C mot ) to determine.
4. The ensuring method (100, 200) according to claim 3, wherein: represents the average motor torque applied at the previous moment (P fc ) is obtained by applying a low-pass filter (Moy) to the target value of the set-point torque at the previous moment (C tgs ) or a measurement of a parameter representing the motor torque applied at the previous moment (C mot ) to determine.
5. The ensuring method (100, 200) according to any one of the preceding claims, wherein: The first determination step (ED1) also determines at least one first intermediate value (C ) of the setpoint torque as a function of the speed (V) of the vehicle (2). kp ).
6. The ensuring method (100, 200) according to any one of the preceding claims, wherein: The second determination step (ED2) determines at least one first intermediate value (C ) of the setpoint torque as a function of the speed (V) of the vehicle (2). kp ) limit value (B kpl , B kpu ).
7. The ensuring method (100) according to any one of the preceding claims, comprising: - a first evaluation step (EE1) in which, according to at least one first intermediate value (C kp ) and represents the average motor torque applied at the previous moment (P fi , P fc ) parameter to evaluate the temporary value of the set point torque (C tg ),as well as - a second evaluation step (EE2) in which, according to at least one first intermediate value (C kp ) limit value (B kpl , B kpu ) and represents the average motor torque applied at the previous moment (P fi , P fc ) parameter to determine the temporary value of the set point torque (C tg ) limit value (B u , B l ); The ensuring step (ES) is based on at least one temporary value (C tg ) and the temporary value of the set point torque (C tg ) limit value (B u , B l ) to determine the target value of the set point torque (C tgs ).
8. The ensuring method (100) according to claim 7, wherein: 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 ensuring step (ES) are performed by an ensuring controller (AFS) which in particular receives the temporary value (C) of the setpoint torque from the position controller (AFC). tg ) as input.
9. The ensuring method (200) according to any one of claims 1 to 6, comprising: - a first ensuring step (ES1) in which, according to at least one first intermediate value (C kp ) and at least one first intermediate value (C kp ) limit value (B kpl , B kpu ) to determine at least one first intermediate value (C kp ) of at least one target value (C kps ); The ensuring step (ES) is based on at least one first intermediate value (C kp ) of at least one target value (C kps ) and represents the average motor torque applied at the previous moment (P fi , P fc ) parameter to determine the target value of the set point torque (C tgs ).
10. The ensuring method (100, 200) according to any one of the preceding claims, wherein: The first determination step (ED1) is also based on a setpoint speed (V ctg ) and at least one parameter representing the speed (V c ) to determine the second intermediate value (C kd ), and the second determination step (ED2) is also based on a set point speed (V ctg ) and at least one parameter representing the speed (V c ) parameters to determine the limit value (B kdl , B kdu ).
11. A vehicle (2) comprising a power steering system (1) of the non-mechanical linkage type implementing a securing method (100, 200) according to any one of the preceding claims.