Sensor system for vehicles, in particular motor vehicles, for detecting the vehicle speed, the vehicle level and/or the state of the vehicle suspension, arrangement for such a sensor system and vehicle having such a sensor system

Abstract

An arrangement for a sensor system for vehicles, in particular motor vehicles, for detecting the vehicle speed, the vehicle level and/or the state of the vehicle suspension, having a sensor for measuring the level of a point on a vehicle body and a vibration damper, the vibration damper comprising a first part and a second part which are movable relative to each other, and wherein the level sensor has an excitation coil, at least one receiver coil and at least one electrically conductive element, wherein the excitation coil and the at least one receiver coil are arranged on the second part of the vibration damper and the electrically conductive element is arranged on the first part of the vibration damper or the first part comprises or forms the electrically conductive element.

Claims

1. A sensor system for motor vehicles, for detecting a vehicle speed, a vehicle level and/or a state of the vehicle suspension, the system comprising: at least one first sensor for measuring a level of a point on a body of the vehicle; at least one second sensor for measuring an acceleration of a point on the vehicle perpendicular to a reference plane on the vehicle; and an evaluation unit, configured to determine a vehicle speed from a distance between axles of the vehicle and a signal curve, determined over a period of time, of a level signal supplied by the at least one first sensor and/or a signal profile, determined over a period of time, of an acceleration signal supplied by the at least one second sensor, wherein the vehicle speed is determined by correlating the distance between the axles of the vehicle and a time interval between two similar sections of the signal curve of the level signal and/or a time interval between two similar sections of the signal curve of the acceleration signal.

2. The sensor system according to claim 1, wherein the sensor system comprises a pair of the at least one first sensor for measuring the level of the point on the body of the vehicle.

3. The sensor system according to claim 1, wherein the sensor system comprises a pair of the at least one second sensor for measuring the acceleration of the point on the vehicle perpendicular to the reference plane on the vehicle.

4. The sensor system according to claim 1, wherein the sensor system comprises two pairs of the at least one first sensor for measuring the level and the at least one second sensor for measuring the acceleration.

5. A vehicle comprising the sensor system according to claim 1.

6. The vehicle according to claim 5, further comprising a first pair of the at least one first sensor and a first pair of the at least one second sensor, wherein one of the first sensors of the first pair of the at least one first sensor and one of the second sensors of the first pair of the at least one second sensor are arranged at a first point in or on the vehicle and the other first sensor of the first pair of the at least one first sensor and the other second sensor of the first pair of the at least one second sensor are arranged at a second point in or on the vehicle, wherein the second point lies behind the first point when viewed in the longitudinal direction of the vehicle.

7. The vehicle according to claim 6, further comprising a second pair of the at least one first sensor and a second pair of the at least one second sensor, one of the first sensors of the second pair of the at least one first sensor and one of the second sensors of the second pair of the at least one second sensor are located at a third point in or on the vehicle and the other first sensor of the second pair of the at least one first sensor and the other second sensor of the second pair of the at least one second sensor are located at a fourth point in or on the vehicle, wherein the fourth point lies behind the third point when viewed in the longitudinal direction of the vehicle, and wherein the first pair of the at least one first sensor and the first pair of the at least one second sensor are arranged on a right-hand side of the vehicle and the second pair of the at least one first sensor and the second pair of the at least one second sensor are arranged on a left-hand side of the vehicle.

8. The vehicle according to claim 5, wherein a first pair of sensors, that includes a first one of the at least one first sensor and a first one of the at least one second sensor, is located at a first point in or on the vehicle and a second pair of sensors, that includes a second one of the at least one first sensor and a second one of the at least one second sensor, is located at a second point in or on the vehicle, and wherein the second point lies behind the first point when viewed in the longitudinal direction of the vehicle.

9. The vehicle according to claim 8, wherein a third pair of sensors, that includes a third one of the at least one first sensor and a third one of the at least one second sensor, is arranged at a third point in or on the vehicle, and a fourth pair of sensors that includes a fourth one of the at least one first sensor and a fourth one of the at least one second sensor, is arranged at a fourth point in or on the vehicle, the fourth point lies lying behind the third point when viewed in the longitudinal direction of the vehicle, and wherein the first and second pairs of sensors are arranged on a right-hand side of the vehicle and the third and fourth pairs of sensors are arranged on a left-hand side of the vehicle.

10. A method for detecting the vehicle speed in the vehicle according to claim 5, the method comprising: detecting, when traveling over ground unevenness, a change in a level of the body and/or the acceleration of a first point on the vehicle relative to a reference plane, via one first sensor of the at least one first sensor and/or one second sensor of the at least one second sensor arranged at the first point on the vehicle; and detecting a time interval, a change in the level of the vehicle body and/or in the acceleration of a second point on the vehicle relative to the reference plane, via another first sensor of the at least one first sensor and/or another second sensor of the at least one second sensor arranged at the second point on the vehicle when traveling over the same ground unevenness; and determining a vehicle speed from a quotient of a known distance between the first point and the second point and from the time interval determined from the level signals of the sensors.

11. A method for monitoring a tire pressure in the vehicle according to claim 5, wherein the vehicle further comprises speed sensors for detecting a speed of the wheels of the vehicle, the method comprising: recording a first value for the speed of the vehicle by the speed sensors; recording a second value for the speed of the vehicle; comparing the first value and the second value and, in the event of a deviation beyond a predetermined value and/or an increase in the deviation, a signal is generated requesting the driver to check the tire pressure.

12. A method for monitoring a steering angle of the vehicle according to claim 5, the method comprising: detecting, when traveling over a first ground unevenness, a change in a level of the body or in the acceleration of a first point on the vehicle relative to a reference plane by one first sensor of the at least one first sensor and/or one second sensor of the at least one second sensor arranged at the first point on the vehicle; detecting, at a time interval, a change in the level of the body or in the acceleration of a second point on the vehicle relative to the reference plane, via another first sensor of the at least one first sensor and/or another second sensor of the at least one second sensor arranged at the second point on the vehicle, when traveling over the first ground unevenness; detecting the time interval; determining a speed of a right side of the vehicle from a quotient of a known distance between the first point and the second point and from the time interval determined from the level signals of the sensors; detecting a change in the level of the body or in the acceleration of a third point on the vehicle relative to the reference plane, via a third first sensor of the at least one first sensor and/or a third second sensor of the at least one second sensor arranged at the third point on the vehicle when traveling over a second ground unevenness, at the same time as traveling over the first ground unevenness, and, at a time interval, a change in the level of the body or in the acceleration of a fourth point on the vehicle relative to the reference plane is detected by a fourth first sensor of the at least one first sensor and/or a fourth second sensor of the at least one second sensor arranged at the fourth point on the vehicle when traveling over the second ground unevenness and the time interval is detected; and determining a speed on the left-hand side of the vehicle from the quotient of the known distance between the third point and the fourth point and of the time interval determined from the level signals of the sensors.

13. A method for detecting the state of the vehicle suspension having the sensor system according to claim 7, the method comprising: using an algorithm stored in the evaluation unit for a calculation of a course of a vibration after traveling over a ground unevenness; calculating a target vibration curve with the vehicle suspension intact from a load state determined from the level of the body measured by the at least one of the first second or from the acceleration measured by the at least one second sensor, or after traveling over the ground unevenness, with the vehicle suspension intact, a target vibration curve is read out from a memory of the evaluation unit as a function of the load state determined from the level of the vehicle body measured by the at least one first sensor and from the acceleration measured by the at least one second sensor; and comparing the target vibration curve, with the vehicle suspension intact, with an actual vibration curve measured by at least one of the first or second sensors after traveling over the ground unevenness.

14. The sensor system according to claim 1, wherein the at least one first sensor is a linear displacement sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is an arrangement according to the invention having a vibration damper, a sensor for measuring the level and a sensor for measuring acceleration,

(3) FIG. 2 is a schematic representation of a unit comprising the excitation coil and three receiver coils of the sensor for measuring the level,

(4) FIG. 3 is a schematic representation of an arrangement of the excitation coil and a first of the receiver coils,

(5) FIG. 4 shows a vehicle having a sensor system comprising the sensors of two arrangements according to the invention,

(6) FIG. 5 shows a signal curve from the sensor to measure the level, and

(7) FIG. 6 shows a signal curve from the sensor to measure acceleration.

DETAILED DESCRIPTION

(8) The example of an arrangement according to the invention shown in FIG. 1 includes the vibration damper 300, 301, 302, 303 and a pair of 100 sensors comprising the level sensor 102 and the accelerometer 103.

(9) The damper 300, 301, 302, 303 essentially corresponds to a known damper and is connected to the vehicle via two elements 301, 302. Without loss of generality, the element 301 can be assumed to be connected to the body and the element 302 connected to the chassis. The damper can be movable in the z-direction. A tappet 303 connected to the element 302 may be immersed into or emerge from a cylinder 300 of the damper 300, 301, 302, 303 connected to the element 301.

(10) The sensor system 100 according to the invention has an essentially pot-shaped holder 101, which is formed of electrically non-conductive material (e.g., plastic PPE or similar). This radially surrounds the cylinder 300 of the damper 300, 301, 302, 303 at a distance and is connected to the tappet 303 at a point 101.P1. This leads to the fact that the holder 101 also slides in the z-direction over the cylinder 300 when the coupling element 303 is immersed in the cylinder 300 of the damper 300, 301, 302, 303.

(11) The surface of the cylinder 300, which is covered by the holder 101, is therefore a measure of the compression depth of the body and thus the desired measurand for determining the vehicle level.

(12) The level sensor used in the example uses an inductive measuring principle. It is a linear displacement sensor.

(13) The linear displacement sensor 102 has a sensor circuit board that can be integrated into the housing 101. The printed circuit board preferably is formed of FR4 and is two- or four-layer. It carries (see FIG. 2) at least one excitation coil 102.10, which is essentially rectangular and may have one or more windings in one or more planes of the printed circuit board 102.

(14) In addition, the printed circuit board 102 carries at least one, preferably two and particularly preferably three receiver coils 102.11, 102.12, 102.13, which may be arranged within the excitation coil 102.10, outside the excitation coil 102.10 or both inside and outside the excitation coil 102.10. The detailed view of a first receiver coil 102.11 is shown in FIG. 3.

(15) Preferably, the receiver coil 102.11 has an identical number of right- and left-running partial turns 102.111, 102.112, which have an essentially identical geometry and are connected in series. FIG. 3 shows a lateral expansion (in the z-direction) of M, wherein the transition point of the two partial turns 102.111, 102.112 is positioned at M/2.

(16) The other receiver coils 102.12, 102.13 are intended for a multiphase system (FIG. 2). They can be moved relative to the receiver coil 102.11. The displacement can be M/4 when using two receiver coils or M/n when using n receiver coils. Optionally, the part of the receiver coils that protrudes beyond the value M in the negative z-direction can be supplemented in a positive z-direction (on the opposite side of the structure).

(17) According to the invention, the excitation coil 102.10 can be exposed to an AC voltage which has a frequency between 1 MHz and 10 MHz (preferably 3.5 MHz) and amplitudes in the range of a few volts. For this purpose, it may preferably be connected as a frequency-determining element in an LC oscillating circuit.

(18) In the receiver coils 102.11, 102.12, 102.13 voltages are induced, which are influenced in their amplitudes by a spaced, positioned electrically conductive element 102.20 which is attached to the cylinder 300 of the damper. By measuring the amplitudes of the voltages induced in the receiver coils 102.11, 102.12, 102.13, the position of the electrically conductive element 102.20 and thus the compression depth of the tappet 303 in the cylinder 300 can then be calculated.

(19) The electrically conductive element 102.20 is attached either in or to the cylinder 300. Alternatively, however, the cylinder 300 itself can act as a conductive element of the inductive linear displacement sensor. For this, the cylinder 300 must have a certain electrical conductivity. With conventional dampers, this is easily given or at least possible.

(20) On the PCB 102 another sensor 103 is applied. This sensor 103 is an inertial measurement unit (IMU), which has at least one accelerometer whose sensitive direction coincides with the z-axis. Preferably, however, the IMU 103 also contains accelerometers with other sensitive axes or rotation rate sensors.

(21) Sensor signals of the level sensor and the IMU 103 are preferably transmitted via the same interface. The interface can be a PSI5 digital interface. In addition to the use of the acceleration values for the control of adaptive chassis systems, the information according to the invention is used to derive further variables.

(22) The algorithms described below can be calculated in a vehicle control unit or in a separate sensor control unit. This requires at least two pairs of sensors, in each case one on the front wheel VR and one on the rear wheel HR.

(23) To determine the vehicle speed, the following approach may be used:

(24) FIG. 4 shows the arrangement of two sensor pairs 100.1, 100.2 on a vehicle. FIG. 5 shows the signal of the linear displacement sensors and FIG. 6 the signal of the IMU (only acceleration a.sub.z in the z-direction). It is assumed that the front wheel VR drives over a curb at time t=0, for example, and thus experiences an acceleration that leads to an almost exponentially subsiding linear movement z due to the spring-damper behavior. Since the vehicle moves in the forward direction, a time interval t later the rear wheel HR experiences an approximately identical acceleration as well as a nearly identical course of linear movement (exact course depends on the load state, etc.). From the information x, which represents the distance of the wheels of the vehicle, the vehicle speed vx=x/t can be calculated from an evaluation unit 1000. This information can be used, for example, to check the plausibility of other systems in the vehicle. The evaluation unit 1000 also determines the value t using common methods for similarity/pattern recognition of signals (e.g., cross-correlation).

(25) To determine the state of the suspension, the following approach can be used:

(26) In addition to the vehicle speed, the state of the suspension can also be assessed. For this purpose, a sensor pair 100 is used. FIGS. 5 and 6 show that an acceleration (e.g., by driving over a pothole) is followed by a certain oscillation of the damper. This depends in its shape on the vehicle load and the state of the suspension/damper:

(27) The load can be estimated by determining the compression depth of the damper. For this purpose, however, the vehicle must be located on a flat surface. When this is the case can be detected via the IMU.

(28) If, for example, the suspension is broken, this affects the post-oscillation behavior of the vehicle. This effect can be so weak that it is not perceived by the driver. However, metrological detection is possible.

(29) For this purpose, an algorithm or look-up tables are stored in the evaluation unit 1000, which calculate which post-oscillation behavior would be expected as a function of the load state and an acceleration. If this does not correspond to the actual measured behavior, either the suspension or the damper is damaged, or the air pressure of the tire has changed.

(30) Cyclic calibration or the consideration of aging and/or temperature influences is possible using common machine learning methods.

(31) By combining the vehicle level sensor 102 with an inertial measurement unit 103, which determines at least the acceleration in the vertical direction, an improvement in the accuracy of the level is possible. By combining at least two sensor pairs 100.1, 100.2, the vehicle speed can be determined.

(32) In order to keep the tolerances of the mechanics small, a solution is particularly preferably described in which the vehicle level is measured directly by measuring the compression depth of the vehicle with the aid of a linear displacement sensor 102. A sensor system according to the invention may additionally comprise an evaluation unit 1000, which evaluates the signals of at least two sensor pairs 100.1, 100.2.

(33) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.