Inertial sensor system for vehicles, and method for operating this inertial sensor system.

Abstract

This document introduces inertial sensor systems for vehicles, methods for operating such systems, and corresponding computer program products. [Solution] The present invention relates to an inertial sensor system (100) for a vehicle, the inertial sensor system (100) comprising one accelerometer (104) at at least two spatially separated locations on the vehicle, each measuring in at least two axes, the accelerometer (104) mapping the direction of action (116) of local centripetal acceleration (114) to one acceleration vector (108), and the inertial sensor system (100) is configured to identify the instantaneous pole (118) of the vehicle using at least two acceleration vectors (108).

Description

TECHNICAL FIELD

[0001] The present invention relates to an inertial sensor system for a vehicle, a method for operating a corresponding inertial sensor system, and a corresponding computer program product.

BACKGROUND ART

[0002] A vehicle may be equipped with a yaw rate sensor. Conventionally, the yaw rate sensor is arranged centrally in a control device. In order to ensure that the measurements of the yaw rate sensor are reliable, it is advantageous if the control device is arranged as close as possible to the center of gravity of the vehicle.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0003] Against this background, the approach presented herein introduces an inertial sensor system for a vehicle, a method for operating a corresponding inertial sensor system, and a corresponding computer program product as defined in the independent claims. Advantageous developments and refinements of the approach presented herein can be seen from the description and are set out in the dependent claims.

MEANS FOR SOLVING THE PROBLEMS

[0004] In the approach presented herein, at least two decentralized acceleration sensors are arranged in a distributed manner within the vehicle, as an alternative or in addition to a centrally arranged yaw rate sensor. These acceleration sensors have a known spacing from one another. In this case, the acceleration sensors are arranged in particular on the wheels of the vehicle. The acceleration sensors detect local accelerations in at least two spatial directions. The local accelerations here also include local centrifugal accelerations or centripetal accelerations. Through multidimensional detection, the acceleration sensors detect the local acting direction of the local accelerations. The acting directions that can be measured at different acceleration sensors differ due to the distributed arrangement. The instantaneous pole of the vehicle lies at the intersection of the acting directions.

EFFECTS OF THE INVENTION

[0005] The approach described here eliminates the need for a central rotation rate sensor, thereby reducing the cost associated with that sensor. Alternatively, a decentralized accelerometer can provide redundancy for the central rotation rate sensor, improving the overall failure reliability and robustness of the system.

[0006] In particular, an acceleration sensor is present within the local control unit of an electromechanical brake, and this acceleration sensor can additionally perform the function proposed here through the use described herein.

[0007] According to a first aspect of the present invention, an inertial sensor system for a vehicle is proposed, comprising one accelerometer each at at least two spatially separated locations on the vehicle, each measuring in at least two axes, wherein the accelerometer maps the direction of action of local centripetal acceleration to one acceleration vector, and the inertial sensor system is configured to determine the instantaneous pole of the vehicle using at least two acceleration vectors.

[0008] A second aspect of the present invention proposes a method for operating a vehicle inertial sensor system, which involves determining the direction of action of local centripetal acceleration at at least two spatially separated locations on the vehicle, each on at least two axes, mapping each to a single acceleration vector, and evaluating at least two acceleration vectors to identify the instantaneous pole of the vehicle.

[0009] The concepts leading to embodiments of the present invention can be considered to be based, in particular, on the ideas and understandings described below.

[0010] An inertial sensor system can capture acceleration in particular, using an accelerometer. Acceleration can be decomposed in at least two spatial directions, which in turn extend perpendicularly to each other. The accelerometer can map the captured acceleration to an electrical signal. The signal can be transmitted via a data line to a central data processing unit. The acceleration can be output as a multidimensional acceleration vector.

[0011] By decomposing acceleration into at least two spatial directions, the direction of action of the acceleration can be determined. Starting from the point of determination, the instantaneous pole of the vehicle exists where the directions of action intersect. At the time of determination, the instantaneous pole is the point of rotation around which the vehicle moves.

[0012] Accelerometers can be spaced apart from each other. In this case, the distance between adjacent accelerometers may be greater than the typical dimensions of control devices within a vehicle. For example, this distance may be greater than 30 cm, greater than 50 cm, greater than 1 m, or even greater than 1.5 m.

[0013] The accelerometers may be positioned within the area of ​​the vehicle's wheels. The vehicle's wheels are far apart from each other and from the vehicle's center. In this case, the distance between adjacent accelerometers may correspond to the distance between adjacent wheels of the vehicle. This allows for a large difference between the directions of action, and consequently, precise identification of the instantaneous pole.

[0014] The acceleration sensor may be located within the local control unit of the vehicle's electromechanical brakes. Such local control units are typically located near or within the vehicle's wheels. In any case, the local control unit of the electromechanical brakes may incorporate an acceleration sensor. This acceleration sensor may also be used to identify instantaneous poles for the purpose of closed-loop and open-loop control of the brakes.

[0015] The inertial sensor system may include acceleration sensors within the area of ​​all the wheels of the vehicle. Accordingly, the number of acceleration sensors in the inertial sensor system may correspond to the number of wheels of the vehicle. Increasing the number of measurement points can improve the accuracy of identifying instantaneous poles. Additionally, measurement errors when determining centripetal acceleration can be filtered, and the inertial sensor system can be configured to be more robust.

[0016] The direction of action of the centripetal acceleration may be determined within at least one horizontal plane. The instantaneous pole can be identified within at least this horizontal plane. The horizontal plane may be oriented approximately parallel to the ground beneath the vehicle. Identifying the instantaneous pole within the horizontal plane is particularly advantageous during normal driving.

[0017] The direction of action of local centripetal acceleration can be determined using three axes. Subsequently, the instantaneous pole can be spatially identified. By spatially identifying the instantaneous pole, the pitching motion and / or lateral sway motion of the vehicle with respect to the instantaneous pole can be understood.

[0018] Using acceleration vectors, the yaw rate of the vehicle may also be determined. The yaw rate is the motion with respect to the instantaneous pole. The yaw rate can be derived from the magnitude of the local acceleration. Generally, the greater the acceleration, the greater the yaw rate.

[0019] Under the use of instantaneous poles, the longitudinal force distribution of the vehicle may be affected. With consideration for instantaneous poles, the vehicle's wheels or axles can be individually accelerated or braked to stabilize the vehicle.

[0020] Furthermore, the wheel's rotation speed sensor may be read to identify the instantaneous pole. The instantaneous pole can be confirmed using the rotation speed information from the rotation speed sensor. In this way, unrealistic locations for the instantaneous pole can be easily eliminated.

[0021] This method is preferably implemented in a computer, and may be implemented, for example, in software or hardware, or in a mixed form consisting of software and hardware, for example in a control device.

[0022] A computer program product or computer program having program code, which can be stored on a machine-readable carrier or storage medium, for example a semiconductor memory, a hard disk storage device or an optical memory, and which is used to carry out, convert and / or control the steps of the method according to one of the aforementioned embodiments, in particular when the program product or program is executed on a computer or any device, is also advantageous.

[0023] It should be added that some of the possible features and advantages of the present invention are described herein with respect to different embodiments respectively. It is self-evident to those skilled in the art that the features of the control device and the method can be suitably combined, adapted or exchanged to arrive at further embodiments of the present invention.

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, neither the drawings nor the description should be construed as limiting the present invention. Brief Description of the Drawings

[0025] [Figure 1] It is a diagram showing a vehicle having an inertial sensor system according to an embodiment. [Figure 2] It is a diagram showing a vehicle having an inertial sensor system according to an embodiment. Modes for Carrying Out the Invention

[0026] The drawings are only schematic diagrams and are not to scale. The same reference numerals refer to the same or identically functioning features.

[0027] Figure 1 shows a vehicle having an inertial sensor system 100 according to one embodiment. The inertial sensor system 100 includes one acceleration sensor 104 in the region of at least two wheels 102 of the vehicle. The acceleration sensor 104 can resolve locally occurring acceleration 106 in at least two spatial directions, where the spatial directions to be resolved are located in a horizontal plane. That is, the acceleration sensor 104 can grasp acceleration 106 in the X and Y directions with respect to the vehicle coordinate system and map the resulting acceleration vectors 108 to one acceleration signal 110 each.

[0028] The acceleration signal 110 is read and evaluated by the central control unit 112 of the inertial sensor system 100.

[0029] Multiple acceleration sensors 104 are positioned within the regions of different wheels 102 of the vehicle, and these acceleration sensors 104 are separated from each other by a predetermined distance in the design. When the vehicle is moving along a curved motion trajectory, centrifugal force acts on the acceleration sensors 104, and each acceleration sensor 104 captures one local centripetal acceleration 114 and maps the direction of action 116 of the centripetal acceleration 114 as a component of the acceleration vector 108 to the acceleration signal 110.

[0030] The directions of action 116 of multiple local centripetal accelerations 114 intersect at the instantaneous pole 118 directly beneath the vehicle. The directions of action 116 differ significantly depending on the spacing between the multiple acceleration sensors 104. The position of the instantaneous pole 118 is determined within the central control unit 112 by triangulation of the directions of action 116 using this spacing.

[0031] Here, instantaneous pole 118 is located to the side of the vehicle. The vehicle is, in other words, traveling on a curve.

[0032] In one embodiment, the acceleration sensor 104 is integrated into a local control unit 120 of the vehicle's electromechanical brakes. The acceleration signal 110 may be used, for example, within the local control unit 120 to monitor and / or control the operation of the brakes.

[0033] In one embodiment, acceleration sensors 104 are placed on all wheels 102 of the vehicle.

[0034] In one embodiment, the acceleration sensor 104 is a three-axis acceleration sensor, meaning it can capture acceleration 106 in all spatial directions. As a result, the acceleration vector 108 is also spatial (three-dimensional), and the instantaneous pole 118 can be spatially identified within the central control unit 112. This allows for the capture of not only the yawing motion related to the vehicle's vertical axis, but also the pitching motion related to the vehicle's lateral axis and the rolling motion related to its longitudinal axis.

[0035] Figure 2 shows a vehicle having an inertial sensor system 100 according to one embodiment. This inertial sensor system 100 is substantially equivalent to the inertial sensor system shown in Figure 1. Unlike the inertial sensor system shown in Figure 1, the instantaneous pole 118 is substantially located in the center of the vehicle. The vehicle is, in other words, rotating about the height axis.

[0036] The possible configurations of the present invention are summarized again below, or expressed in slightly different terms.

[0037] This article describes the use of electromechanical brake acceleration sensors to measure the yaw rate of a vehicle.

[0038] The type of brake system that has been used for a long time is the hydraulic brake system. In the case of a hydraulic brake system, the driver has a mechanical means of intervention in the brakes. In the future, the use of electromechanical brakes (EMBs) will increase and may replace hydraulic brake systems. In the case of electromechanical brakes, an electric motor is energized, and the resulting moment is converted into translation by a transmission mechanism, and a caliper with pads causes the vehicle to decelerate through friction.

[0039] Furthermore, the EMB actuator may be configured to include a sensor system, such as a current strength sensor / current sensor, an EMB position sensor, and / or a wheel speed sensor / wheel rotation speed sensor. Such an EMB actuator may be referred to as a "smart actuator." In particular, an acceleration sensor (e.g., MEMS) inside the ECU can be used inexpensively to measure acceleration (in the x, y, and / or z directions), vibration, or acoustics.

[0040] EMB actuators may be mounted on each of the vehicle's wheels, resulting in a single system. One possible architecture / topology may consist of a central control unit, a communication bus, and the EMB actuators.

[0041] In a conventional H-circuit topology for a braking system, the central control unit is responsible for distributing the braking force and issuing commands to the EMB actuators.

[0042] The approach described here allows for highly reliable measurement of vehicle angular velocity. This measurement can be supplied to the ESP, enabling the ESP to better understand the driving conditions.

[0043] For this purpose, acceleration sensors within the EMB's control unit are used to measure the vehicle's angular velocity. The key feature of this method is that multiple acceleration sensors are distributed, generating different centripetal forces. This allows for highly reliable determination of the yaw rate.

[0044] The advantage lies in the robustness of the measurement, due to the use of multiple sensors.

[0045] In particular, with conventional yaw rate sensors, to ensure good measurement accuracy, the yaw rate sensor must be installed as close as possible to the vehicle's center of gravity. If the yaw rate sensor is not installed at the vehicle's center of gravity, a time-consuming or costly coordinate transformation is required.

[0046] The approach presented here is based on measuring the centripetal acceleration (a_zentri) that occurs when rotational motion or yaw rate exists at radius r and velocity v. The following equation represents the fundamental physical principle.

[0047]

number

[0048] Here, the radius r represents the distance from the instantaneous pole (MP) (center of rotation). The initial challenge is that while the accelerometer can measure a_zentri, both the rotational speed v and the radius r are unknown. This challenge is solved by the inherent characteristic of having multiple EMB actuators, which allows at least two measurements to be taken at two EMBs of the vehicle. Figures 1 and 2 show two examples with four accelerometers. In these cases, instantaneous pole determination by a_zentri is shown during cornering or when the vehicle is spinning.

[0049] The arrows mark the measured centripetal acceleration a_zentri. The intersection of the a_zentri vectors creates instantaneous poles (MPs) around which the vehicle rotates.

[0050] In one minimal variation, at least two accelerometers are required to be incorporated into two different actuators in the x and y directions (in a plane parallel to the road). More advantageous, however, is the incorporation of four sensors measuring in at least two different directions, such that none of the sensors measuring in the same direction are incorporated into the same EMB as any other sensors measuring in the same direction. These sensors can be incorporated into two, three, or four EMBs. A simpler approach here is two accelerometers measuring in the x and y directions, incorporated into two EMBs.

[0051] In one embodiment, however, three or four accelerometers may be integrated into different EMBs, which can improve the robustness of the measurements (comparable to GPS having three or four satellites).

[0052] In one embodiment, a three-axis accelerometer is incorporated instead of a two-axis accelerometer. This allows for the identification of three-dimensional instantaneous poles, thereby enabling the identification of both the MP for lateral motion and the MP for pitching motion.

[0053] In one embodiment, the force distribution of the brakes, drive, steering, and suspension is derived based on yaw motion or lateral sway motion and / or pitching motion (if measured).

[0054] In particular, the measured force distribution can be compared to a desired force distribution, thereby allowing vehicle actuators (at least EMB; however, steering, drive, and suspension are also possible) to be monitored, or closed-loop control circuits to be closed.

[0055] In one embodiment, monitoring is further performed between the acceleration sensor, the yaw rate sensor (if present), and the wheel speed sensor.

[0056] In one embodiment, the vehicle stability system accesses the captured / processed data.

[0057] Finally, it should be added that the concept of "to have, to possess (aufweisend, umfassend, etc.)" does not exclude other elements or steps, and the concept of the "indefinite article (eine, ein, etc.)" does not exclude plurals. The symbols in the claims should not be considered limiting. [Explanation of Symbols]

[0058] 100 Inertial Sensor Systems 102 wheels 104 Accelerometer 106 Acceleration 108 Acceleration vector 110 Acceleration signal 112 Central Control System 114 Centripetal acceleration 116 Direction of action 118 Instantaneous Extreme 120 Local control unit

Claims

1. An inertial sensor system (100) for a vehicle, the inertial sensor system (100) comprising one accelerometer (104) measuring in at least two axes at at least two spatially separated locations on the vehicle, the accelerometer (104) mapping the direction of action (116) of local centripetal acceleration (114) to one acceleration vector (108), and the inertial sensor system (100) is configured to identify the instantaneous pole (118) of the vehicle using at least two of the acceleration vectors (108).

2. The inertial sensor system (100) according to claim 1, wherein the acceleration sensor (104) is located within the area of ​​the wheel (102) of the vehicle.

3. The inertial sensor system (100) according to claim 2, wherein the acceleration sensor (104) is located within a local control device (120) of the vehicle's electromechanical brake.

4. The inertial sensor system (100) according to claim 2 or 3, wherein the inertial sensor system (100) comprises acceleration sensors (104) within the area of ​​all wheels (102) of the vehicle.

5. A method for operating a vehicle inertial sensor system (100), comprising: determining the direction of action (116) of local centripetal acceleration (114) in at least two spatially separated locations on the vehicle, each on at least two axes, mapping each to a single acceleration vector (108), and evaluating at least two of the acceleration vectors (108) to identify the instantaneous pole (118) of the vehicle.

6. The method according to claim 5, wherein the direction of action (116) of the centripetal acceleration (114) is determined within at least one horizontal plane, and the instantaneous pole (118) is identified within at least the horizontal plane.

7. The method according to claim 5 or 6, wherein the direction of action (116) of the local centripetal acceleration (114) is determined in three axes, and the instantaneous pole (118) is spatially identified.

8. The method according to any one of claims 5 to 7, further comprising determining the yaw rate of the vehicle using the acceleration vector (108).

9. The method according to any one of claims 5 to 8, wherein the longitudinal force distribution of the vehicle is affected under the use of the instantaneous pole (118).

10. Furthermore, the method according to any one of claims 5 to 9, wherein the rotation speed sensor of the wheel (102) is read in order to identify the instantaneous pole (118).

11. A computer program product, wherein the computer program product is configured to cause a processor to perform, convert and / or control the method described in any one of claims 5 to 10 when the computer program product is executed.

12. A machine-readable storage medium in which the computer program product described in claim 11 is stored.

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