Method of determining and instructing corrected set motor torque which varies according to correction frequency with operation value as center on basis of set motor torque

Abstract

To provide a control motor that is small-sized and needs only a small number of machine components.SOLUTION: A method of determining a corrected set motor torque Cmc is adapted to a control motor of an electric power steering system devoid of a mechanical link. The control motor receives the corrected set motor torque Cmc, and applies a motor torque to a rotation shaft having a steering wheel. The method includes a step of receiving a set motor torque Cmo and a correction step. At the correction step, the corrected set motor torque Cmc is determined based on a result of comparing the set motor torque Cmo with an ordinary operation threshold. The corrected set motor torque Cmc varies according to a correction frequency with a corrected operation value as a center within a corrected operation range Zc. The corrected operation value is lower than the set motor torque Cmo.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to the field of power steering, and more particularly to a method for commanding a set motor torque and a power steering without mechanical linkage that implements such a method. [Background technology]

[0002] A vehicle steering system is intended to allow a driver to control the path of the vehicle by changing the steering angle of the vehicle's wheels with the steering wheel. The wheel steering angle is particularly related to the steering wheel angle, hereinafter referred to as "steering wheel angle." The driver changes the steering wheel angle by applying a force to the steering wheel, hereinafter referred to as "steering wheel torque."

[0003] Generally, a steering system comprises several elements, including the steering wheel, a rack, and two wheels, each connected to a connecting rod. The rack is the part used to steer the wheels, i.e., change the angle of the wheels via the connecting rod. The rack converts changes in the angle of the steering wheel into changes in the angle of the vehicle's wheels.

[0004] In electric power steering systems without a mechanical link, known as "steer-by-wire," the steering wheel is mechanically decoupled from the rack. In this case, the steering system includes a steering wheel unit that is mechanically independent from the rack unit. In other words, forces applied to the steering wheel unit are not mechanically transmitted to the rack unit, and vice versa.

[0005] The rack unit includes the rack and at least one rack electronic control unit that specifically controls the angular position of the rack so that the angular position of the rack approximately corresponds to the angle of the steering wheel. Thus, the driver can control the vehicle by the steering wheel, i.e., change the angular position of the rack. The rack electronic control unit includes a steering regulator that controls a steering motor that applies a steering motor torque to the rack. More specifically, the angle of the steering wheel is measured or calculated to determine a set steering angle to be reached by the angular position of the rack. In other words, the steering regulator controls the angular position of the rack to the set steering angle by controlling the steering motor torque applied by the steering motor on the rack.

[0006] The steering wheel unit comprises said steering wheel and at least one steering wheel electronic control unit which determines in particular the torque to be felt by the driver during steering, hereinafter referred to as set motor torque. The set motor torque is particularly intended to make the driver feel torque information that corresponds to the actual situation in which the vehicle is located (curve, straight, grip level, road surface condition, etc.). The steering wheel electronic control unit comprises a control regulator which controls the steering wheel torque to the set motor torque by means of a control motor. The control motor then applies the motor torque to the rotation axis of the steering wheel.

[0007] The set motor torque varies between a minimum and a maximum value depending, among other things, on the maximum torque that can be provided by the control motor.

[0008] More specifically, the set motor torque varies mainly as a function of the vehicle's driving speed, i.e., the actual situation of the vehicle, the forces acting between the wheels and the rolling surface, and the rack position, particularly the rack position when the rack is in contact with a stopper. The rack is provided with a stopper at each end. The stopper may be a physical stopper that mechanically prevents the rack from moving, or a virtual stopper that prevents the rack from moving by the steering motor. In particular, a maximum value is required when the rack reaches a limit position, i.e., when the steering wheel can no longer be turned in a power steering system with a mechanical link between the steering wheel unit and the rack unit.

[0009] As an example, it is assumed that at a set motor torque between 30Nm-50Nm, the steering wheel is prevented from rotating. In other words, when the control motor applies a torque between 30Nm-50Nm, the driver's force is not sufficient to rotate the steering wheel.

[0010] There are known solutions in which the control motor used is a motor that generates the motor torque directly on the rotation axis of the steering wheel. This solution requires a control motor that can generate a motor torque between the minimum and maximum set motor torque, i.e., between 30Nm and 50Nm, and can drive a large motor. In addition, power electronics are required, which leads to high power consumption and high electronic component prices.

[0011] In some solutions, the control motor used is equipped with a reducer, which is placed between the motor and the rotating shaft of the handle, making it possible to generate a motor torque between the minimum and maximum set motor torque. For example, with a 20x reduction and 90% efficiency, the maximum set motor torque is 2.8 Nm. This solution requires a motor with smaller dimensions than the above solutions, but it requires an additional mechanical component, the reducer, which increases the risk of failure.

[0012] Therefore, there is a need for a control motor that is small and requires few mechanical parts. Summary of the Invention

[0013] In some embodiments, 1. A method for indicating a corrected set motor torque determined based on a set motor torque for a control motor of an electric power steering having no mechanical linkage, the method comprising: The control motor receives the corrected set motor torque and exerts the motor torque on a rotary shaft having a handle; The method is implemented by a steering wheel electronic control unit, the method comprising: receiving a set motor torque; A correction step, wherein the correction step comprises: the corrected set motor torque is determined based on a result of comparing the set motor torque with a normal operation threshold; the corrected setpoint motor torque varies at a corrected frequency about a corrected operating value over a corrected operating range; the corrected operating value is lower than the set motor torque; a correction step; An instruction step, in which the control motor applies the corrected set motor torque to the rotation axis of the handle; Instruction steps and The present invention relates to a method comprising:

[0014] The control motor is part of the steering wheel unit of the electric power steering without any mechanical link, which in particular comprises said steering wheel and at least one steering wheel electronic control unit which determines the torque to be felt by the driver during steering, hereinafter referred to as set motor torque. The set motor torque is in particular intended to make the driver feel torque information that corresponds to the actual situation in which the vehicle is located (curves, straights, grip level, road surface condition, etc.).

[0015] The steering wheel electronic control unit receives the set motor torque during a receiving step and then corrects, i.e. modifies, this set motor torque according to the particular situation during a correcting step to determine a corrected set motor torque.

[0016] The corrected setpoint motor torque is the motor torque that serves as the setpoint for the control motor.

[0017] In the correction step, the set motor torque is compared with a normal operation threshold, and based on the result, a corrected set motor torque is determined.

[0018] Over a corrected operating range, which corresponds to a range of set motor torque values, the corrected set motor torque varies at a corrected frequency around a corrected operating value, the corrected operating value being lower than the set motor torque.

[0019] In other words, for a set motor torque within the corrected operating value, the corrected set motor torque varies around the corrected operating value between a value greater than the corrected operating value and a value less than the corrected operating value.

[0020] Therefore, the control motor does not provide the set motor torque, at least permanently. The control motor provides a motor torque that is at least partially lower than the set motor torque. Therefore, the control motor that applies the motor torque directly to the rotation shaft of the handle can be smaller in size than if it had to provide the set motor torque completely. Therefore, the size and power consumption of the control motor and the electronic control unit are reduced compared to the prior art control motor that applies the motor torque directly to the rotation shaft of the handle.

[0021] The compensated change in set motor torque causes a vibration-like sensation in the steering wheel, which, according to the applicant's research, makes it possible to simulate a motor torque that is greater than the actually applied motor torque, and therefore the driver of the vehicle holding the steering wheel gets the impression of a stronger resistive torque than the actually applied resistive torque.

[0022] The subject matter of the present disclosure may include one or more of the following features, either alone or in combination.

[0023] In some embodiments, the corrected set motor torque is less than or equal to the set motor torque.

[0024] In some embodiments, the corrected set point motor torque is less than the set point motor torque over the corrected operating range.

[0025] Thus, the control motor is smaller in size than a control motor that must provide the full set motor torque.The present invention allows the control motor to be reduced in size and power consumption compared to the prior art.

[0026] In some embodiments, the corrected set point motor torque varies at a corrected frequency around a corrected operating value.

[0027] The difference between the upper and lower limit values ​​of the corrected set motor torque for a given set motor torque corresponds to the correction amplitude.

[0028] The correction amplitude affects how the driver feels the vibration.

[0029] In some embodiments, the correction amplitude depends on the set motor torque and / or time.

[0030] For example, the correction amplitude increases with the set motor torque.

[0031] For example, the correction amplitude increases with the duration that the set motor torque is required.

[0032] In some embodiments, the corrected set point motor torque is equal to the set point motor torque over the normal operating range.

[0033] Therefore, in the normal operating range, the set motor torque is not changed.

[0034] In some embodiments, the normal operating threshold is equal to both the maximum value of the normal operating range and the minimum value of the corrected operating range.

[0035] The normal operating threshold is a set motor torque value that marks the boundary between the normal operating range and the corrected operating range.

[0036] Thus, the normal operating threshold determines from which set motor torque the correction is applied.

[0037] For example, if the set motor torque is less than the normal operating threshold, the set motor torque is within the normal operating range and no correction is applied; if the set motor torque is greater than the normal operating threshold, the set motor torque is within the corrected operating range and correction is applied.

[0038] In some embodiments, the correction frequency depends on the set motor torque and / or time.

[0039] For example, the correction frequency increases with the set motor torque.

[0040] For example, the correction frequency increases with the duration that the set motor torque is required.

[0041] In some embodiments, the corrected operating value depends on the set motor torque and / or time.

[0042] For example, the corrected operating value increases with the set motor torque.

[0043] For example, the corrected operating value increases with the duration that the set motor torque is required.

[0044] In some embodiments, the method determines a torque signal based on a set motor torque.

[0045] The torque signal varies depending on the set motor torque to be commanded to the driver.

[0046] In some embodiments, the torque signal is determined based on a corrected set point motor torque.

[0047] In some embodiments, the torque signal is a tactile signal, an auditory signal, or a visual signal.

[0048] Thus, the driver receives information about the set motor torque through other sensations.

[0049] In some embodiments, the method includes a resetting step following the correcting step, in which the angle of the steering wheel is determined upon detecting movement of the steering wheel in a direction opposite to the direction in which the correcting step was performed.

[0050] The present invention does not prevent the steering wheel from rotating. In fact, since the steering wheel is not mechanically connected to the rack and the corrected set motor torque is less than the set motor torque, the vehicle driver can continue to turn the steering wheel, for example, while the rack is in a limited position or while the wheels are blocked. Thus, the driver can turn the steering wheel multiple times in the same direction without changing the rack position. To avoid the driver having to repeat this turn in the opposite direction multiple times before moving the rack in the opposite direction again, the method according to the present invention includes a reset step. For this purpose, the reset step detects counter-steer, i.e., a change in the direction of rotation of the steering wheel, and determines the steering wheel angle corresponding to the rack position.

[0051] In some embodiments, during the reset step, the angle of the steering wheel is determined based on the result of a comparison between the set motor torque and a limit threshold.

[0052] The limit threshold is the value of the set motor torque at which it is considered that the wheel rotation is blocked or the rack is in a limit position and therefore the rack can no longer be displaced.

[0053] Thus, for example, the reset step is only performed if the set motor torque is greater than a limit threshold, or in other words, if the steering angle is likely to become inconsistent with the actual position of the rack.

[0054] Another aspect of the invention relates to an electric power steering without mechanical linkage, which implements the method according to the invention. [Brief explanation of the drawings]

[0055] The invention will be better understood from the following description of one or more embodiments according to the invention, given by way of non-limiting example and illustrated with reference to the accompanying schematic drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of a power steering system without mechanical links. [Figure 2] FIG. 2 is a diagram of the change in corrected set motor torque as a function of set motor torque. [Figure 3] FIG. 3 is a diagram illustrating the corrected frequency and corrected operating value as a function of the set motor torque. DETAILED DESCRIPTION OF THE INVENTION

[0056] Only those elements necessary for the understanding of the invention are shown, and to facilitate readability of the figures, identical elements have been given the same reference numerals from one figure to the next.

[0057] It should be noted that in this specification, the terms "right" and "left" used to describe the direction of rotation of a vehicle's wheels, and "clockwise" and "counterclockwise" used to describe the direction of rotation of a vehicle's steering wheel, refer to this direction relative to the vehicle in a forward driving situation, i.e., the direction as viewed by the driver, who is typically positioned directly in front of the steering wheel.

[0058] The present invention relates to a corrected set motor torque C determined on the basis of a set motor torque for a control motor M of a power steering system 1 for a vehicle 2, more particularly for a motor vehicle 2 intended for the transportation of people. mc This relates to a method of indicating the following.

[0059] The control motor M is preferably an electric motor with two operating directions, and is preferably a brushless rotary electric motor. The control motor M is directly engaged with the rotation shaft of the handle 3, for example by a pinion. For example, the control motor M has a maximum motor torque of less than 5 Nm, for example 4 Nm, preferably 3 Nm. Therefore, the dimensions of the control motor M should be less than 10 cm x 10 cm, for example about 8 cm x 8 cm, and the current consumption should be less than 70 A.

[0060] 1, the power steering system 1 includes a steering wheel 3, to which a driver can apply a force called "steering wheel torque." The angle θ3 and rotation direction of the steering wheel 3 are measured by an angle sensor 23.

[0061] The handle torque T3, the angle θ3 of the handle 3, and the rotation direction of the handle 3 are transmitted to the rack electronic control unit 20 and the handle electronic control unit 21.

[0062] The steering wheel 3 is not mechanically connected to the steering rack 6, and the steering rack 6 itself is guided for translational movement within a steering casing 7 fixed to the vehicle 2. In other words, the steering wheel 3 is mechanically separated from the steering rack 6. In this case, the steering system 1 comprises a steering wheel unit that is mechanically independent from the rack unit. In other words, a force 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 "steer-by-wire" type.

[0063] The steering wheel unit comprises at least said steering wheel 3 and a steering wheel electronic control unit 21 which determines in particular the torque to be felt by the driver when steering the steering wheel 3, which torque is hereinafter referred to as a set motor torque C mo This is called the set motor torque C mo is specifically intended to make the driver feel torque information that corresponds to the actual situation in which the vehicle 2 is located (curves, straight lines, grip level, road surface condition, etc.). The steering wheel electronic control unit 21 sets the steering wheel torque by means of the control motor M. mo Then, the handle torque is controlled to the set motor torque C mo The control motor M applies a motor torque to the rotation axis of the handle so that the motor torque is close to or equal to the rotation axis of the handle.

[0064] The rack unit includes at least the rack 6 and a rack electronic control unit 20 that controls, in particular, the angular position of the rack 6 so that the angular position of the rack 6 coincides with a set angular position. The set angular position usually coincides with the steering angle θ3, but can be changed depending on the functions of the vehicle 2, such as a path following function or a parking assist function of the vehicle 2.

[0065] The rack electronic control unit 20 determines a set rack torque for controlling the steering motor 24 that applies a motor torque T12 to the rack 6. In other words, by determining the set rack torque of the steering motor 24, the rack electronic control unit 20 controls the angular position of the rack 6 to a set angular position.

[0066] The angular position of the rack 6 can be derived from the angular position θ12 of the steering motor 24.

[0067] Preferably, the ends of the rack 6 are connected to steering connecting rods 8, 9 which are connected to the steering knuckles of the steering wheels 10, 11 (left wheel 10 and right wheel 11, respectively), so that longitudinal translational movement of the rack 6 makes it possible to change the steering angle (yaw angle) of the steering wheels 10, 11. The steering wheels 10, 11 may preferably be drive wheels.

[0068] The steering motor 24 is preferably an electric motor with two directions of operation, and is preferably a rotary electric motor of the brushless type.

[0069] The steering motor 24 may be directly coupled to the steering rack 6, for example by means of a pinion 13.

[0070] The indication method according to the present invention is to set the motor torque C mo and then receiving the corrected set motor torque C mc and finally, an instruction step is performed, in which the control motor M applies the corrected set motor torque C to the rotary shaft of the steering wheel. mc Apply the corrected set motor torque C mc is the motor torque that serves as the target value for the controlled motor M.

[0071] In the correction step, the corrected set motor torque C mc is the set motor torque C mo and normal operating threshold S fIn other words, during the correction step, the set motor torque C mo is the normal operating threshold S f Based on this result, the corrected set motor torque C mc is determined.

[0072] In some embodiments, as illustrated in FIGS. 2 and 3, the normal operating threshold S f On the other hand, the normal operating range Z f on the other hand, the corrected operating range Z c The normal operating threshold S f is the normal operating range Z f and the corrected operating range Z c The set motor torque value C is the boundary between mo is.

[0073] Normal operation threshold S f What is the set motor torque C? mo Set motor torque C from mo Determines whether the correction is applied.

[0074] For example, if you set the motor torque C mo is the normal operating threshold S f If it is less than the set motor torque C mo is the normal operating range Z f Therefore, the corrected set motor torque C mc is the normal operating range Z f Over the time, set motor torque C mo is equal to.

[0075] If the motor torque C mo is the normal operating threshold S f If it is larger, set motor torque C mo is the corrected operating range Z c The correction is performed by the steering electronic control unit 21.

[0076] Corrected operating range Z cThe corrected set motor torque C mc is the corrected operating value V fc Centered on the correction frequency F c changes over time.

[0077] In some embodiments, the correction frequency F c is the set motor torque C as shown in Figure 2 or Figure 3. mo and / or time dependent.

[0078] In Figures 2 and 3, the correction frequency increases with the set motor torque.

[0079] In some embodiments, the correction frequency F c is the set motor torque C mo increases with the duration of the request.

[0080] Corrected operating value V fc is the corrected set motor torque C mc corresponds to the torque value at the center of vibration. The corrected operating value V fc is the set motor torque C mo is selected to be lower.

[0081] In some embodiments, the corrected operating value V fc is the set motor torque C mo and / or time dependent.

[0082] For example, the corrected operating value V fc As shown in Figure 3, the set motor torque C mo increases with

[0083] For example, the corrected operating value V fc is the set motor torque C mo increases with the duration of the request.

[0084] In some embodiments, the corrected set motor torque C mc is the corrected operating value V fcIt varies with the correction amplitude around .

[0085] Given set motor torque C mo Corrected set motor torque C mc The difference between the upper and lower limits corresponds to the correction amplitude.

[0086] The correction amplitude affects how the driver feels the vibration.

[0087] In some embodiments, the correction amplitude is calculated by multiplying the set motor torque C mo and / or time dependent.

[0088] For example, the correction amplitude is set to the set motor torque C mo increases with

[0089] For example, the correction amplitude is set to the set motor torque C mo increases with the duration of the request.

[0090] In some embodiments, the corrected set motor torque C mc is the set motor torque C mo or less than the set motor torque C mo is equal to.

[0091] In some embodiments, the corrected set motor torque C mc is the compensated operating range Z c Over the time, set motor torque C mo is less than.

[0092] Therefore, the control motor M is set to the motor torque C mo The control motor M does not provide a set motor torque C mo Thus, the control motor M provides a motor torque at least partially lower than the set motor torque C moThe present invention makes it possible to reduce the size and power consumption of the control motor M and electronic control unit compared to the prior art where the control motor applies torque directly to the rotation shaft of the steering wheel.

[0093] Corrected set motor torque C mc The change in the resistance torque causes a vibration-like sensation in the steering wheel 3, which, according to the applicant's findings, makes it possible to simulate a motor torque that is greater than the actually applied motor torque, and therefore the driver of the vehicle holding the steering wheel 3 gets the impression of a resistance torque that is stronger than the actually applied resistance torque.

[0094] However, the corrected set motor torque C mc , the steering wheel rotation is not blocked. In other words, the driver can continue to rotate the steering wheel 3 in one direction indefinitely, despite feeling vibrations, without changing the position of the rack 6. To avoid the driver having to rotate the rack 6 in the opposite direction multiple times before moving it in the opposite direction again, the method according to the invention includes a reset step.

[0095] The reset step following the correction step determines the steering angle θ3 when it detects movement of the steering wheel 3 in the direction opposite to the direction in which the correction step was performed. In other words, the reset step detects counter-steer, i.e., a change in the rotational direction of the steering wheel 3, and determines the steering angle θ3 that is consistent with the position of the rack 6.

[0096] In some embodiments, during the reset step, the handle angle θ3 is adjusted to the set motor torque C mo and the limiting threshold S b The decision is based on the results of a comparison with

[0097] Limit Threshold S bis the set motor torque C at which it is considered that the rotation of the wheels 10, 11 is blocked or the rack 6 is in a limit position so that the rack 6 can no longer be moved. mo is the value.

[0098] Therefore, for example, the set motor torque C mo is the limiting threshold S b In other words, the reset step is performed only if the handle angle θ3 may become inconsistent with the actual position of the rack 6.

[0099] This method sets the motor torque C mo This torque signal is then converted into a corrected set motor torque C mc In addition to this, the set motor torque C that should be felt by the driver mo Shows.

[0100] In some embodiments, this torque signal is the corrected set point motor torque C mc is determined based on the

[0101] In some embodiments, the torque signal is a tactile signal, an auditory signal, or a visual signal.

[0102] Thus, the driver receives information about the set motor torque through other sensations.

[0103] While the present invention has been described with reference to particular embodiments, it will be apparent that modifications and variations can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments shown / mentioned may be combined in additional embodiments. Accordingly, the specification and drawings should be considered illustrative rather than restrictive.

[0104] It is also clear that all features described in relation to a method can be transferred to a device, either alone or in any combination, and conversely, all features described in relation to a device can be transferred to a method, either alone or in any combination.

Claims

1. A corrected set motor torque (C) determined based on a set motor torque for a control motor (M) of an electric power steering (1) without a mechanical link. ｍｃ ) a method of indicating The control motor (M) is driven by the corrected set motor torque (C ｍｃ ) and exerts a motor torque on a rotating shaft equipped with a handle (3), The method is realized by a steering wheel electronic control unit (21), and the method comprises: Set motor torque (C ｍｏ ) and A correction step, wherein the correction step comprises: The corrected set motor torque (C ｍｃ ) is the set motor torque (C ｍｏ ) and normal operating threshold (S ｆ ) and is determined based on the results of a comparison with The corrected set motor torque (C ｍｃ ) is the corrected operating range (Z ｃ ) over the corrected operating value (V ｆｃ ) as the center of the correction frequency (F ｃ ) and The corrected operating value (V ｆｃ ) is the set motor torque (C ｍｏ ) lower, a correction step; A reset step following the correction step, in which determining the angle (θ3) of the steering wheel based on the detection of the movement of the steering wheel (3) in a direction opposite to the direction in which the correction step was performed; A reset step and An instruction step, in which The control motor (M) applies the corrected set motor torque (C ｍｃ ) to apply Instruction steps and A method comprising:

2. The corrected set motor torque (C ｍｃ ) is the corrected operating value (V ｆｃ ) with a correction amplitude, The method of claim 1 .

3. The correction amplitude is the set motor torque (C ｍｏ ) and / or time-dependent, The instruction method according to claim 2 .

4. The corrected set motor torque (C ｍｃ ) is the normal operating range (Z ｆ ) over the set motor torque (C ｍｏ ) is equal to The method of claim 1.

5. Normal operation threshold (S ｆ ) on the other hand, the normal operating range (Z ｆ ) on the other hand is equal to the maximum value of the corrected operating range (Z ｃ ) is equal to the minimum of The instruction method according to claim 4.

6. The correction frequency (F ｃ ) is the set motor torque (C ｍｏ ) and / or time-dependent, The method of claim 1.

7. The set motor torque (C ｍｏ ) further comprising determining a torque signal as a function of The method of claim 1.

8. During the reset step, the handle angle (θ3) is adjusted to the set motor torque (C ｍｏ ) and the limiting threshold (S ｂ ) determined based on the results of a comparison with The method of claim 1.

9. Implementing the method according to any one of claims 1 to 8 Electric power steering without mechanical linkage (1).

Images