DE102007026189A1 - Electromechanical steering mechanism for motor vehicle i.e. passenger car, has high pass filter for filtering difference signal, where high pass filtered difference signal is modulated with signal that represents additional steering moment - Google Patents

Abstract

The mechanism (1) has an electromotor (9) applying an additional steering moment (MZ) to the mechanism depending on a steering moment (ML) applied by a driver. A steering tie rod sensor (12) generates a signal that represents force of a steering tie rod, and a difference calculating unit calculates a difference between the rod force signal and another signal that represents the steering moment and the additional moment. A high pass filter filters the difference signal, where the high pass filtered difference signal is modulated with the signal that represents the additional moment. An independent claim is also included for a method for operating an electromechanical steering mechanism of a motor vehicle.

Description

The The invention relates to an electromechanical steering system for a motor vehicle, comprising an electric motor via which in response to a signal representing a steering torque, An additional steering torque can be introduced into the steering. Further relates the invention relates to a method for operating such a steering.

Such steering systems are well known in the art and are inter alia in the DE 103 17 991 A1 , of the DE 103 60 582 A1 and the DE 10 2005 003 180 A1 described.

at Electromechanical steering is when steering by an electric motor generates an additional torque to assist the driver. electric motors wise by design relatively high inertia on. These inertias attenuate a road-side force excitation, which over Tie rods, a steering gear and a steering column to a Steering wheel is transmitted. Here, the inertia act the electric motor in a sense like a flywheel. at Vehicles designed primarily for comfort be, is such a damping of the road-side force excitation basically welcome. Indeed the driver experiences so little feedback from the roadway. For vehicles with a more sporty character This can sometimes be disturbing.

Of the Invention is based on the object to remedy this situation. In particular, the invention aims at an electromechanical Steering to improve the road feel.

These Task is by an electromechanical steering system according to claim 1 solved. For this purpose, means for generating a one Tie rod force representing signal, means for subtraction between the tie rod force signal and a steering torque and / or Additional signal representing signal and a high-pass filter provided for filtering the difference signal. The high pass filtered Tie rod force signal is one representing the additional steering torque Signal modulated.

High frequency Suggestions that are generated by the roadway, would normally dampened by the inertia of the electric motor become. By their inclusion in the control of the electric motor These are noticeable to the driver, as by means the electric motor of the road surface excitation corresponding moments on the steering wheel being represented.

At a steering gear is due to the kinematic conditions a close relationship between a force on the rack and a moment at the steering column. Under one the tie rod force representing signal, hereinafter also "tie rod force signal", In the present case, one of the tie rod forces will be directly equivalent Force size and one of these indirectly corresponding Size such as a corresponding one Moment understood at the steering column. Correspondingly, too a signal representing the steering torque and / or additional torque, hereinafter also "steering torque signal or" additional torque signal "via a corresponding force magnitude of the rack being represented. For differential signal formation required Signal adjustments, of course, the expert takes without further ahead.

The Tie rod force signal, for example, by means of suitable sensors be measured. Further, it is possible the tie rod force from data available on the vehicle using a calculation model estimate.

According to one Another advantageous embodiment of the invention is the high-pass filtered difference signal to a control signal for controlling the electric motor, with which the Additional steering torque is adjusted, modulated and if necessary accordingly edited. However, it is also possible to use the tie rod force signal already earlier in the generation to include the actuating signal for the electric motor.

to Difference with the tie rod signal, the additional torque signal, the steering torque signal or a signal are used which the Sum of the steering torque applied by the driver and that of the electric motor represents additional torque generated.

The The above object is further achieved by a method of operation an electromechanical steering system according to claim 9 solved.

Further, advantageous embodiments of the invention are in the claims specified.

following the invention will be described with reference to embodiments shown in the drawings explained in more detail. The drawing shows in:

1 a schematic view of an embodiment of an electromechanical steering system according to the invention,

2 a representation of the consideration of the tie rod force according to a first embodiment, and in

3 a representation of the consideration of the tie rod force according to a second embodiment

4 a representation of the consideration of the tie rod force according to a third embodiment.

The embodiment in 1 shows an electromechanical steering 1 for a passenger vehicle. The steering 1 includes a steering wheel 2 via which a steering torque M _L can be introduced by a driver. This steering torque M _L is from the steering wheel 2 over a steering column 3 to a steering gear 4 transfer. The steering gear 4 has a rack, which at their ends in each case via a joint 5 with a tie rod 6 is coupled. Every tie rod 6 engages a wheel carrier supported on the vehicle body 7 on which a vehicle wheel 8th is stored. About the steering gear 4 is the steering torque M _L in the form of a steering force along the rack on the tie rods 6 and ultimately on the vehicle wheels 8th brought to action.

At a suitable point, in the embodiment of the steering gear 4 , An additional steering torque M _{Z is} in the steering 1 initiated to assist the driver in steering. This additional steering torque M _Z is at an electromechanical steering 1 by an electric motor 9 generated, which can be arranged, for example, axially parallel to the rack. The electric motor 9 This can either be installed coaxially around the rack or laterally offset next to the rack. It is also possible to arrange the engine elsewhere or a force attack on the steering column 3 provided. About the additional steering torque M _Z is thus another force component on the rack or on the tie rods 6 provided.

The additional steering torque M _Z is set as a function of the steering torque M _L applied by the driver. This steering torque M _L can for example via a rotation angle sensor 10 on the steering column 3 be measured.

In the calculation of the additional steering torque optionally further vehicle characteristics include, which are known from an antilock braking system or an electronic stability program, such as the current wheel speeds and braking pressures, the vehicle speed, the yaw rate of the vehicle or a steering angle thereof. Furthermore, the steering angle speed on the steering wheel 2 be taken into account. Based on these parameters is in a conventional manner by means of a control unit in a 11 stored auxiliary characteristic curve or according to a calculation rule prescribed there for the respective driving situation to a steering torque M _L an additional steering torque M _Z determined and in the form of a suitable control signal to the electric motor 9 transmit, which then generates a corresponding moment. At the steering thus both moments M _L and M _{Z come} into effect. As the support is continuous and steady, the support is on the steering wheel 2 not felt. However, the level of support may vary depending on the driving situation.

In addition to the steering torque M _{L of} the driver and the additional steering torque M _Z engage the steering 1 other forces, including the rolling of the vehicle wheels 8th on the roadway and over the tie rod 6 , the steering gear 4 and the steering column 3 to the steering wheel 2 can be transmitted. The excitation by the roadway takes place with relatively high frequencies, but rather low amplitudes. In an electromechanical steering of the type described above, the electric motor act 9 and a transmission stage associated therewith, however, due to their inertial masses as a damper, so that the road-side suggestions are swallowed by as far as possible in the steering and the steering wheel 2 do not reach. For the driver this is very little feedback from the road felt. In a sporty suspension design, this is sometimes undesirable.

Therefore, it is proposed here, the ideas swallowed by the steering suggestions about the electric motor 9 to represent and so for the driver on the steering wheel 2 to make palpable. For this purpose, a near-wheel steering rod force F _{SP is} measured or estimated by means of a calculation model and subtractive in the determination of the control of the electric motor 9 included. The tie rod force F _SP represents the sum of the axial components of the steering torque M _{L of} the driver, the additional torque M _{Z of} the electric motor and the road surface excitation. If, for example, the roadway excitation to a highly dynamic, temporary increase in the tie rod force F _SP , this would at the steering wheel 2 make unmuffled power transmission by a corresponding reaction torque noticeable. Due to the inertia in an electromechanical steering, the driver would normally not notice such a highly dynamic increase in the tie rod force. According to the invention by the inclusion of the tie rod force F _SP in the control of the electric motor 9 the additional steering torque M _{Z be} changed briefly so that for the driver on the steering wheel 2 a reaction is noticeable that corresponds to a lane feedback. As a result, the road feel is improved.

At the in 1 illustrated embodiment are suitable sensors 12 in the area of tie rods 6 or the ends of the rack of the steering gear 4 arranged. The tie rod sensor reindeer 12 generate a signal representing the tie rod force F _SP , the signal to the control unit 11 is transmitted.

From the signals of the sensors 12 the individual tie rods 6 will be in a first step 13 a resulting tie rod signal is formed. This can be done for example by simple averaging or by a driving situation-dependent evaluation of the signal components.

As in 2 is shown, a difference signal s _{F is} generated by subtraction between the tie rod force signal and a signal representing the additional torque M _Z , which represents the roadway excitation. The signal generation is here by way of example based mathematically on torque quantities, including the measured tie rod force, as by reference numerals 16 indicated, converted to a moment size. However, it is equally possible to refer all signals to force magnitude or otherwise match each other. For example, the manual torque M _L can be guided over a characteristic curve. That's just a reinforcement and not a filter. The output quantity is then also a force, which is converted by a factor into an engine torque.

Subsequently, this difference signal s _F by means of a high-pass filter 14 filtered. The high pass filter 14 has a preferably non-jumping gain characteristic over which the individual frequency ranges of the road-side vibration excitation can be weighted.

to Enabling individual suspension tuning through the driver can increase the gain of the high-pass filtered Tie rod force signal can be made adjustable, so that, for example, in the context of different suspension programs between a sporty and a comfortable, if necessary also multi-stage vote of the steering can be selected can.

Furthermore, it is possible to switch off the high-pass filter 14 provide, so that by switching off a greater damping of the steering can be adjusted.

The high-pass filtered signal becomes a summer 15 switched. Another input signal is at the summer 15 a signal representing the additional steering torque M _Z. The output signal of the summer 15 thus represents an additional steering torque with a modulated difference signal, which expresses the roadway excitation. This modified signal M _Z * is, optionally after further conditioning, as a control signal to the electric motor 9 transmitted.

In a modification, the tie rod force F _{SP is} not measured, but estimated from known parameters on the vehicle. A corresponding calculation device with a suitable calculation algorithm is in the control unit 11 stored and replaced or supplements the signal input of the tie rod sensors 12 , The signal obtained by the calculation algorithm representing the tie rod force F _SP is determined as in FIG 2 explained embodiment further treated, that is initially high-pass filtered.

In a further modification, it is possible to generate the difference signal s _F from the tie rod force signal and the steering torque signal. The difference signal s _{F can} then be included at an earlier time in the calculation of the additional steering torque M _Z to obtain a modified additional torque M _Z *, as the in 3 is shown. However, it is also possible here, the difference signal s _F as in 2 Immediately modulate on the control signal of the motor.

Alternatively, a signal representing the steering torque M _L and the additional torque M _Z can also be used as an input quantity for subtraction with the tie rod force signal, as described in US Pat 4 is indicated. The thus generated difference signal s _F can then as in 2 or 3 be included in the determination of the modified additional moment M _Z *.

The The invention has been described above with reference to preferred embodiments and modifications explained in more detail. It is, however not limited to this, but includes all through the claims defined embodiments.

1

electromechanical steering

2

steering wheel

3

steering column

4

steering gear

5

Tie joint

6

tie rod

7

wheel carrier

8th

vehicle

9

electric motor

10

Rotation angle sensor

11

control unit

12

Tie rod sensor

13

Steering wheel angle sensor

14

High Pass Filter

15

summing

16

signal Conditioning

F _SP

Tie-rod force

M _L

steering torque

M _Z

Additional steering torque

_MZ *

modified Additional steering torque

S _F

difference signal

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10317991 A1 [0002]
• - DE 10360582 A1 [0002]
• - DE 102005003180 A1 [0002]

Claims (16)

Electromechanical steering system for a motor vehicle, comprising an electric motor ( 9 ), via the dependent on a driver applied steering torque (M _L ) an additional steering torque (M _Z ) in the steering ( 1 ), characterized in that means for generating a signal representing a tie rod force (F _SP ), means for subtracting between the tie rod force signal and a signal representing the steering torque and / or additional torque, and a high-pass filter ( 14 ) are provided for filtering the difference signal, and the high-pass filtered difference signal is modulated to the additional steering torque (M _Z ) representing signal. Electromechanical steering system according to claim 1, characterized in that a control device ( 11 ) is provided, which in dependence of the steering torque (M _L ) representing a signal representing the additional steering torque (M _Z ) actuating signal for the electric motor ( 9 ), wherein the high-pass filtered difference signal is modulated to the additional signal (M _Z ) representing the control signal. Electromechanical steering system according to claim 1, characterized in that a control device ( 11 ) is provided, which in dependence of the steering torque (M _L ) representing a signal representing the additional steering torque (M _Z ) actuating signal for the electric motor ( 9 ), wherein the high-pass filtered difference signal is modulated to the signal representing the steering torque (M _L ) prior to generation of the actuating signal. Electromechanical steering system according to one of claims 1 to 3, characterized in that at least one sensor ( 12 ) is provided for measuring the tie rod force (F _SP ). Electromechanical steering system according to one of Claims 1 to 3, characterized in that a calculation device ( 16 ) for estimating the tie rod force (F _SP ) from signals of an anti-lock brake system and / or an electronic stability program and / or a steering wheel angle is provided. Electromechanical steering system according to one of Claims 1 to 5, characterized in that the high-pass filter ( 14 ) can be switched off. Electromechanical steering system according to one of claims 1 to 6, characterized in that the high-pass filter ( 14 ) has a jump-free gain characteristic. Electromechanical steering according to one of the claims 1 to 7, characterized in that the gain of high-pass filtered differential signal is adjustable. Method for operating an electromechanical motor vehicle steering system in which, as a function of a steering torque (M _L ) applied by the driver, by means of an electric motor ( 9 ) an additional steering torque (M _Z ) is generated, characterized in that a tie rod force (F _SP ) representing signal generated by subtraction with a steering torque (M _L ) and / or additional torque (M _Z ) representing signal generates a difference signal and high pass filtered and the high-pass filtered signal into the drive of the electric motor ( 9 ) is included. A method according to claim 9, characterized in that in dependence of the steering torque (M _L ) representing a signal representing the additional steering torque (M _Z ) actuating signal for the electric motor ( 9 ) is generated, wherein the high-pass filtered difference signal is modulated to the additional torque (M _Z ) representing the control signal. Electromechanical steering system according to claim 9, characterized in that, depending on the steering torque (M _L ) representing a signal representing the additional steering torque (M _Z ) actuating signal for the electric motor ( 9 ), wherein the high-pass filtered difference signal is modulated onto the signal representing the steering torque (M _L ) prior to the generation of the actuating signal. Electromechanical steering system according to one of claims 9 to 11, characterized in that the tie rod force (F _SP ) is measured. Electromechanical steering system according to one of claims 9 to 11, characterized in that the tie rod force (F _SP ) is estimated from signals of an anti-lock brake system and / or an electronic stability program and / or a steering wheel angle. Electromechanical steering system according to one of Claims 9 to 13, characterized in that the high-pass filter ( 14 ) can be switched off. Electromechanical steering system according to one of Claims 9 to 14, characterized in that the high-pass filter ( 14 ) has a jump-free gain characteristic. Electromechanical steering according to one of the claims 9 to 15, characterized in that the reinforcement of the high-pass filtered difference signal is adjustable.