WO1991000188A1

WO1991000188A1 - Device for controlling a vehicle's chassis as a function of the road surface

Info

Publication number: WO1991000188A1
Application number: PCT/DE1990/000403
Authority: WO
Inventors: Erich Rubel; Michael Panther; Klaus Gatter
Original assignee: Robert Bosch Gmbh
Priority date: 1989-06-29
Filing date: 1990-05-30
Publication date: 1991-01-10
Also published as: DE3930517A1; EP0434784A1; JPH04500492A; KR920700124A

Abstract

Disclosed is a device for controlling the chassis, as a function of the road surface, of a vehicle, in particular a motor vehicle. The device comprises sensors which determine the dynamic running status, the data from the sensors being fed to a processing circuit which generates a signal characteristic of the unevenness of the road surface and controls actuators acting on the vehicle suspension. It is proposed that, for each wheel, the instantaneous value of the road-surface unevenness (S) and/or the speed on road-surface unevenness (S) be determined from the data supplied by the sensors in each wheel region and this value supplied as an actual variable to the control circuit associated with each wheel.

Description

Device for road-dependent chassis control

State of the art

The invention relates to a device for the travel-dependent suspension control of a vehicle, in particular a motor vehicle, according to the preamble of the main claim.

The driving state of a vehicle is dependent on the driver's driving maneuvers on the one hand, but also on the road on the other. Uneven road surfaces which excite the wheels of the vehicle to vibrate can lead to the energy of these vibrations being transmitted to the body of the vehicle. In order to achieve the highest possible driving comfort, such vibrations should be avoided. Furthermore, unevenness in the roadway can lead to changes in the wheel load, ie to dynamic changes Cause wheel load fluctuations. These are a measure of driving safety. A wheel load that is as constant as possible is aimed for a safe driving condition.

From DE-PS 35 18 503 a device for computer-aided, roadway-dependent control of dampers of a vehicle suspension is known. Sensors are provided which emit electrical signals which are characteristic of the unevenness of the road and which are fed to an evaluation circuit. The evaluation circuit converts the sensor signals into two different signals. The first signal corresponds to the averaged height of the road bumps overall, and the second signal represents the relationship, referred to as ripple, between the averaged heights of the long-wave and short-wave road bumps. The control signals for the control systems are made from these signals by means of characteristic maps the damper is formed in such a way that it is composed of a function, the sum of which depends, among other things, on the average height of the uneven road surface, the ripple and the product of the average height and ripple. To determine the dynamic driving state data, a sensor on the front axle and - to determine the body-side accelerations - in the front vehicle body area is provided on the vehicle. This configuration and the described signal processing take into account averaged and therefore, moreover, time-shifted values of the road unevenness in the chassis control. Advantages of the invention

The device according to the invention with the features mentioned in the main claim has the advantage that the unevenness of the road surface or uneven road speed occurring on each wheel is detected and is currently fed to each control circuit, so that a corresponding control of an actuator assigned to the wheel is carried out can be done. The unevenness of the road is thus detected and counteracted immediately in a corresponding size, so that optimum wheel load values can be set and maintained and wheel deflections are counteracted in such a way that virtually no vibrations are transmitted to the body of the vehicle. Since, according to the invention, each wheel area of the vehicle is monitored by sensors and has its own control loop, possible pitch and roll movements of the body are essentially prevented by the unevenness of the roadway. Overall, it is clear that the chassis control according to the invention offers a high level of comfort with great driving safety. The immediate, current intervention, which takes place in the full size of the road unevenness disturbance, and not by means of time-delaying and amplitude-influencing averaging, as in the prior art, results in extremely high dynamics of the chassis control, which crucially improves comfort. and safety behavior of the vehicle improved. According to a further development of the invention, the uneven road surface and / or the uneven road surface speed is fed to the controller as a disturbance variable.

In each wheel area there is a damper force, a sensor which measures the relative distance (spring deflection) between the wheel and the structural section of the vehicle located in the wheel area and a sensor which detects the vertical wheel acceleration. From the data of these three sensors, the evaluation circuit forms the associated unevenness in the road and the speed of the road in unevenness. It is particularly advantageous that - in contrast to the prior art mentioned - no size-varying data are used in the evaluation, such as e.g. B. the mass of the body of the vehicle, since it varies with the payload.

In particular, the device is designed so that a summing point is assigned to each wheel, which is supplied with the damping force as additive input variables and which is fed in a first multiplication stage with the spring constant of the spring arrangement assigned to the wheel area and to which the travel in a second multiplication stage wheel acceleration multiplied by the wheel mass is connected as a subtraction quantity and that the output signal of the summing point is connected via a third multiplication stage, which takes into account the reciprocal value of the spring constant of the tire, as a subtraction quantity at a sum point which is additively generated in an integration stage temporal double integral of the wheel acceleration provides the instantaneous value of the road unevenness. It is preferably provided that the output signal

<the summing point forms a dynamic wheel load fluctuation, which indicates the change in force of the associated tire on the road.

In order to form the unevenness of the road speed, the time integral of the wheel acceleration with a positive sign and the output value of the third multiplier stage with a negative sign, which is conducted via a differentiator, are fed to a summation point.

Active or, in particular, semi-active dampers can be used as the actuator. An active damper is to be understood as a piston / cylinder unit, the piston of which can be actively acted upon by a pressure medium, so that the position of its characteristic curve is possible in all four quadrants of a Cartesian coordinate system in which the ordi¬ The damper force is plotted and the piston speed is plotted on the abscissa. The active damper requires high control energies, since an active pressure build-up is necessary for piston displacement. In contrast, semi-active dampers manage with low control energy, since only a displacement of the pressure medium is carried out by piston displacement, but no active pressure generation for piston displacement takes place. A piston / cylinder unit is again provided. The piston divides the cylinder space into two chambers communicating with one another via a passage cross section. This passage cross section is controllable, that is, the flow resistance for the pressure medium displaced by the piston can be varied. Excellent measurement results can be obtained if the sensor detecting the damper force determines its measured variable between a support bearing of the damper and the associated body section of the vehicle. The sensor that detects the wheel acceleration is preferably arranged close to the wheel bearing of the associated wheel. The sensor determining the spring deflection detects its measured variable between the steering knuckle of the associated wheel and the section of the vehicle body that is present in the wheel area.

drawing

The invention is explained in more detail below with reference to the figures. Show it:

FIG. 1 shows a block diagram of the chassis control according to the invention,

FIG. 2 shows a two-mass model of the chassis control,

FIG. 3 shows a positioning of sensors that detect the driving state data, shown on the model,

FIG. 4 shows a block diagram for determining the unevenness of the road and

FIG. 5 shows a detailed block diagram of the chassis control. Description of the embodiment

The vehicle (passenger car) shown schematically in FIG. 1 is provided with sensors 4, 5 and 6 on all four wheels 1, ie twice in the area of the front axle 2 and also in the area of the rear axle 3. Each wheel 1 is arranged on a steering knuckle and is connected to a body 8 of the vehicle via a spring arrangement 7 (FIG. 2). In parallel to the spring arrangement 7, an actuator 9 is arranged between the wheel support part and the body 8. The actuator 9 is designed as a semi-active damper 10.

The sensors 4 (FIG. 1) are used to determine the damper force F _d . To record this measurement variable, they are arranged between a support bearing (not shown) of the respective damper 10 and the section of the body 8 located in the respective wheel area (FIG. 3). In order to determine the spring deflection x _{ar of} each wheel 1 relative to the body 8, the sensors 5 are connected between the respective steering knuckle of the associated wheel 1 and the corresponding section of the body 8. The sensors 6 are attached to each wheel 1 directly next to the wheel bearing. They determine the wheel acceleration x _r . The wheel acceleration x _r is recorded in the vertical direction, ie parallel to the deflection x _ar .

The signals from the sensors 4, 5 and 6 each arrive in a signal processing circuit 11. The unevenness S of the road and the road surface S are determined from the processed signals in a processing unit 12. Roughness speed S determined. This will be discussed in more detail below. Using these and other signals (such as the damper force F _d , the compression speed x _ar , the compression travel x _ar and the build-up speed x _a ), a processor circuit 65 determines the control signal for the assigned semi-active damper 10. The processing unit 12 and the processor circuit 65 are preferably implemented with powerful microprocessors. The instantaneous damping of the semi-active dampers 10 is individually optimized for each wheel 1, taking into account unevenness S and unevenness S of the road. Optimizing the overall damping of the vehicle against pitching and swaying is the task of a higher-level circuit 15. It communicates in both directions with the four processor circuits 65 via a data transmission device 14 (for example a CAN bus) to which it just like the processor circuits 65, is connected via lines 13. The data transmission device 14 can also lead to other electronic circuits in the vehicle (for example for injection control, etc.). The circuit 15 can alternatively also be integrated in one of the processor circuits 65 or distributed over a plurality of processor circuits 65.

FIG. 2 shows a so-called two-mass model, which embodies the respective wheel area of the vehicle. The wheel mass m _{r of} the wheel 1 is connected to the body mass via the spring arrangement 7. The body mass m _a is to be understood here as the portion of the total mass of the vehicle body which is to be assigned to each wheel 1. The spring arrangement 7 has the spring constant c _& . The damper 10, _which develops the damper force F _d _, lies between the wheel mass _r and the body mass m _a . The spring deflection x _ar exists between the wheel mass _r and the body mass _a - the elastic parts of the wheel 1 (tire) are embodied in the model by a spring 16 with the spring constant c _r . The wheel 1 rolls on the road 17, which has an unevenness S on the road. The road unevenness S is defined with respect to an inertial system 18 (vertical component). The wheel acceleration x _r and the cycle path x _{r are also} related to this inertial system 18.

For each wheel 1, the wheel-equation of motion, which is shown in FIG. 2, can be easily established on the basis of the model described. It reads:

^F d ^{+ c} a ^x ar - F, H = 0

with F _r = c _r (x _r - S)

The wheel load fluctuation is designated with F _r . It indicates the change in force of the associated tire on the road.

If the wheel motion equation is solved for the unevenness S and the unevenness S, the result is

S = x _r - F _r ^c r 1 S = x _r - F _r ^c r

FIG. 4 shows, as a block diagram, the circuit structure for determining the unevenness S of the road and the uneven road speed S. Such a circuit structure is provided for each wheel 1 of the vehicle. The damper force F ^ determined by the sensor 4 of the corresponding wheel 1 is fed to a low-pass filter 19 (500 Hz), the output of which is connected to a high-pass filter 20 (T = 5 s). The output of the high-pass filter 20 is connected to an evaluation circuit 21 which has the factor "1". The output signal of the evaluation circuit 21 is additively fed to a summing point 22. The spring deflection x _ar of the wheel 1 in question relative to the body 8 of the vehicle is - as already described - determined by the associated sensor 5. Its data are also fed to a low-pass filter 22 '(500 Hz) which is connected to a high-pass filter 23 (T = 5 s). The output of the high-pass filter 23 is connected to a first multiplier stage 24, which carries out a multiplication by the spring constant c _{a of} the spring arrangement 7. Finally, the output signal of the first multiplication stage 24 is fed additively to the summing point 22.

The wheel acceleration x _r determined by the corresponding sensor 6 is connected to a low-pass filter 25 (500 Hz), which is followed by a high-pass filter 26 (T = 5 s). Via a line 27, a second multi- tiplizierstufe 28 connected, which carries out a multiplication by the wheel mass _r . The output signal of the second multiplier stage 28 is supplied to the summing point 22 subtractively. The output 29 of the summing point 22 is subtractively connected to a summing point 30 via a third multiplication stage 33. In the third multiplier stage 33, the reciprocal of the spring constant c _{r of} the wheel 1 (tire) is multiplied. The line 27 has a branch which leads to an integrating stage 27 'with two integrators 31 and 31', which forms the temporal double integral of the input data. This means that the wheel path x _{r is} formed from the wheel acceleration x _r evaluated by the filters 25 and 26. The output of the integrating stage 27 'is connected to the sum point 30 with a negative sign. The starting value of the sum point 30 provides the unevenness S of the road. At the output of the third multiplier stage 33, a differential detector 32 'is connected, which - with a negative sign - leads to a summation point 32 and feeds the relative wheel speed x _{rr to} it. The time integral of the wheel acceleration x _r originating from the integrator 31 is - with a positive sign - given to the sum point 32. At the exit of the summing point 32, the roadway unevenness speed S is available.

The unevenness of the roadway S which is not directly measurable can therefore be determined by the circuit described above and shown in FIG. It is fed as a disturbance variable to a controller 65 of the chassis control. The road surface unevenness speed is also S is determined and also fed to the controller as a disturbance variable.

A corresponding overview block diagram is shown in FIG. The circuit arrangement shown there is provided for each wheel 1 of the vehicle. It includes the circuit structure according to FIG. 4. The damper force F _d , the wheel acceleration x _r , the relative spring deflection x _ar and the body acceleration x _a are supplied to the low-pass filters 19, 22 ', 25 and 38, which have already been mentioned in part and which are used as so-called anti-aliasing filters are formed. A line 39 leads from the low-pass filter 19 to the high-pass filter 20, the output 41 of which applies the now filtered data of the damper force F ^ to the controller 65. The line 41 also leads to the evaluation circuit 21, which is connected to the summing point 22. The output of the low-pass filter 25 is connected to the already described high-pass filter 26, which is connected to the integrator 31. Furthermore, the output of the high-pass filter 26 leads to the second multiplier stage 28, which is connected to the summing point 22 with a negative sign. At the output of the integrator 31, the wheel speed x _r is available, which is fed via a filter 48 to the further integrator 31 'belonging to the integrating stage 27', at whose output the cycle path x _r is present, which is at the summing point 30 connected. The output variable x "(wheel speed) of the integrator 31 is fed to a summing point 53 via a line 51 and a filter 52. The output of the low-pass filter 22 'is connected to a differentiator 54, which uses a filter 55 to determine the relative spring speed _{ar to} the controller 65 feeds. Furthermore, the output of the low-pass filter 22 'is connected to the high-pass filter 23, the output of which leads via the first multiplier stage 24 to the summing point 22. The output of the high-pass filter 23 is also connected to the controller 65 and provides the relative deflection x _ar . The output of the low-pass filter 38 is also connected to a high-pass filter 58, the output of which is connected to an integrator 59 which supplies the assembly speed _& to the controller 65. The output of the summing point 22 leads via a line 29 to a differentiator 61, the output of which provides the relative wheel speed x _rr , which is connected to the summing point 53 with a negative sign. The line 29 is also connected — also with a negative sign — to the summation point 30. The output 30 'of the summation point 30 is connected to the controller 65 and provides the unevenness S on the roadway. The output 63 of the summing point 53 has the uneven road speed S which is fed to the controller 65. The controller 65 bil¬ det from the mentioned input variables (F _d, x _ar, S, S, _Ar and x x _a) an operating voltage V _d with which a Durchströmguerschnitt influencing the Steuer¬ means of the damper is driven 10th

Claims

Expectations

1. Device for the roadway-dependent chassis control of a vehicle, in particular a motor vehicle, with sensors which record the dynamic driving state and whose data are fed to an evaluation circuit which generates a signal which is characteristic of the unevenness of the road and which has a spring arrangement Actuators interacting with the vehicle controls, characterized in that the evaluation circuit for each wheel (1) determines the instantaneous value of the road unevenness (S) and / or road unevenness (S) present there from the data of each wheel area arranged sensors (4, 5, 6) are determined and supplied to the control circuit associated with each wheel (1) as the current variable.

2. Device according to claim 1, characterized in that the controller (65) Uneven road surface (S) and / or uneven road surface speed (S) is supplied as a disturbance variable.

3. Device according to one of the preceding claims, characterized in that in each wheel area a the damper force (F _d ), a the relative distance (deflection x _ar ) between the wheel (1) and a body (8) of the vehicle and a the vertical wheel acceleration (x _r ) sensor (4,5,6) is provided.

4. Device according to one of the preceding claims, characterized by a summing point (22) assigned to each wheel (1), the damping force (F _d ) as additive input variables and that in a first multiplier stage (24) with the spring constant (c _a ) the spring deflection path (x _ar ) assigned to the wheel area (7) is fed and to which the wheel acceleration (x _r ) multiplied in a second multiplier stage (28) by the wheel mass (m _r ) is connected as a subtraction variable and that the output signal of the summing point (22) is connected as a subtraction variable to a summation point (30) via a third multiplication stage (33) taking into account the reciprocal of the spring constant (c _r ) of the tire (wheel 1), the additive that in an integrator (27 ') er¬ witnessed temporal double integral of the wheel acceleration (x _r) is supplied, wherein the output of the Sum¬ menpunkts (30) the instantaneous value of Fahrbahnun evenness (S) returns.

5. Device according to one of the preceding claims, characterized in that that the output signal of the summing point (22) forms a dynamic wheel load fluctuation F _r = c _χ (x _r - S), which indicates the change in force of the associated tire on the road.

6. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that to form the road bump speed

(5) the time integral of the wheel acceleration (x _r ) with a positive sign and the output value passed via a differentiator 32 'to the third multiplier stage (33) with a negative sign are fed to a summation point (32).

7. Device according to one of the preceding claims, that the actuator (9) is constructed as a semi-active damper (10).

8. Device according to one of the preceding claims, characterized in that the damper force (F _d ) detecting sensor (4) determines its measured variable between a support bearing of the damper (10) and the associated section of the body (8) of the vehicle.

9. Device according to one of the preceding claims, characterized in that the wheel acceleration (x _r ) determining sensor

(6) is arranged next to the wheel bearing of the associated wheel (1).

10. Device according to one of the preceding claims, characterized in that that the sensor (5) detecting the spring deflection (x _ar ) determines its measured variable between the steering knuckle of the associated wheel (1) and the corresponding section of the body (8) of the vehicle.