Abstract:
A sensor arrangement for detecting movements, which is designed as a monolithic arrangement and in which several sensors are integrated. A first sensor is provided to detect a linear acceleration and a second sensor to detect a yaw rate. The sensor arrangement also comprises a third sensor for detecting yaw acceleration.

Description:
[0001]    This application is the U.S. national phase application of PCT International Application No. PCT/EP2005/051213, filed Mar. 16, 2005, which claims priority to German Patent Application No. DE 10 2004 012 686.0, filed Mar. 16, 2004 and German Patent Application No. DE 10 2004 012 688.7, filed Mar. 16, 2004. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a sensor arrangement for detecting movements, which is designed as a monolithic arrangement. 
         [0004]    2. Description of the Related Art 
         [0005]    In driving stability control operations (ESP) for controlling and limiting undesirable yaw movements of the vehicle about its vertical axis, sensors are used to measure essential variables, which can be varied by the driver on purpose. The variables that can be changed by the driver relate to the steering angle, the accelerator pedal position, the brake pressure, the lateral acceleration of the vehicle as well as the rotating speed of the individual vehicle wheels. A nominal yaw rate is calculated from the measured variables. Additionally, a yaw rate sensor is used to measure the actual value of the yaw rate, which develops in response to the driving maneuver. If the actual value of the yaw rate differs from the calculated nominal value of the yaw rate by a predetermined degree jeopardizing driving stability, the yaw motion of the vehicle and, thus, the actual yaw rate is limited to admissible values by way of a targeted brake and engine intervention. 
         [0006]    In addition to driving stability control systems, passenger protection devices serve to increase the safety of passengers in a motor vehicle. Only one single motor vehicle is involved in a considerable number of accidents. Deadly injuries occur in accidents of this type mostly in case the motor vehicle overturns about its longitudinal axis in the accident. Vehicle rollover can have fatal consequences especially in convertibles. For this reason, passenger protection devices are known for convertibles, which safeguard a survival space for the vehicle occupants in order that they will not get into direct contact with the ground when rollover takes place. A safety roll bar extending over the heads of the vehicle passengers is used for this purpose. However, a stationary safety roll bar will greatly impair the aesthetic impression of convertibles. This is why some convertibles are equipped with protecting devices which, in the normal case, are hidden in the vehicle seats or behind the vehicle seats and will only pop up in case of an imminent rollover to fulfill their protective function then. The initiation of a protection device of this type in good time requires the detection of an imminent rollover in good time. 
         [0007]    DE 101 23 215 A1 discloses a method for activation of a passenger protection device in a motor vehicle, which among others is mainly based on measuring the yaw acceleration of the motor vehicle about the vehicle&#39;s longitudinal axis. 
         [0008]    In addition, DE 199 62 685 C2 discloses a method and a system for determining the angular acceleration of a motor vehicle turning about its longitudinal axis. The prior art method calculates the angular acceleration from the difference of the detected accelerations and the component of a distance vector being normal to the axis of rotation. 
         [0009]    DE 199 22 154 C2 discloses a device for generating electric signals, which reflect the yaw rate, the acceleration, and the roll velocity of the vehicle body. 
         [0010]    Basic components of these prior art methods and devices are sensor arrangements, which detect linear velocities and accelerations as well as yaw rates and yaw accelerations about different axes of an initial system attached to a vehicle. To limit costs of manufacture, sensor arrangements of this type are made of silicon as micromechanical systems. The monolithic design of acceleration sensors for two or three directions in space is known in prior art. Sensors of this type are commercially available e.g. with the makers VTI and Kionix. 
         [0011]    In addition, a monolithic arrangement is described in U.S. Pat. No. 5,313,835, which is composed of a two-axis gyroscope, a uniaxial gyroscope, a three-axis linear acceleration sensor, and a microprocessor electronic unit. The two-axis gyroscope and the uniaxial gyroscope add to become a gyroscope measuring in three directions in space. The prior-art sensor arrangement is appropriate to measure yaw rates and linear accelerations in three directions in space. 
       SUMMARY OF THE INVENTION 
       [0012]    Based on the above, an object of the invention involves disclosing a sensor arrangement, which exhibits improved characteristics compared to the state of the art. 
         [0013]    This object is achieved by a sensor arrangement as described herein. The sensor arrangement of the invention that is intended to detect movements is configured as a monolithic arrangement in which several sensors are integrated. A first sensor is provided for detecting a linear acceleration and a second sensor for detecting a yaw rate. According to the invention, the sensor arrangement is characterized in that it comprises a third sensor for detecting yaw acceleration. 
         [0014]    Advantageously, the sensor arrangement can be configured on a monocrystal substrate. In one embodiment of the invention, the monocrystal substrate is made of silicon. It is favorable in this respect that the silicon technology is matured so that high-quality sensors can be manufactured at low costs. 
         [0015]    In a preferred embodiment, the sensors are designed as micromechanical structures in the substrate. 
         [0016]    According to another design, it is favorably provided that all or individual sensors and evaluating circuits are connected to and contacted by the substrate by means of flip-chip technology or cementing, soldering and wire-bonding. 
         [0017]    In an application in the automotive industry, it has proven especially expedient when the sensors on the substrate are aligned in such a fashion that they are appropriate in a corresponding installation position in a motor vehicle, to measure the linear acceleration in the longitudinal direction of the motor vehicle, the yaw rate, and the roll acceleration about the longitudinal axis of the motor vehicle. The yaw rate represents an important input quantity for driving dynamics control operations, while the roll acceleration frequently controls the initiation of passenger protection systems, which have been described hereinabove. 
         [0018]    In an optional improvement of the invention, the sensor arrangement includes a fourth sensor, which is suitable for detecting a linear acceleration and is aligned on the substrate in such a way as to be able to additionally measure a linear acceleration across the longitudinal axis of the vehicle. The lateral acceleration is another useful input quantity for driving dynamics control operations. 
         [0019]    In another embodiment of the sensor arrangement of the invention, the direction of measurement of the sensors can lie in the principal plane defined by the substrate, while in another embodiment the direction of measurement of the sensors can be disposed perpendicular to the principal plane defined by the substrate. 
         [0020]    It has proven favorable in cases of practical application when several sensor arrangements are integrated to form a subassembly, when the subassembly comprises two sensor arrangements in which the directions of measurement of the sensors lie in the principal plane defined by the substrate, and the directions of measurement of the two sensor arrangements are oriented perpendicular to each other, and when the subassembly comprises an additional sensor arrangement in which the direction of measurement of the sensors lie normal to the principal plane defined by the substrate. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Embodiments of the invention are represented in the drawings. In the accompanying drawings: 
           [0022]      FIGS. 1   a  and  1   b  show a view of the symbolism of parameters used and the directions of reference; 
           [0023]      FIGS. 2   a  to  2   b  are schematic views of the components of the sensor arrangement of the invention, and 
           [0024]      FIGS. 3   a  to  3   c  are schematic views of the integration of the sensor arrangement into a packing. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]      FIG. 1   a  illustrates the symbols for sensors integrated in the sensor arrangement, which are used to explain the invention. Each sensor is shown as an arrow in combination with a parameter identification code. The arrow indicates the direction of measurement of the respective sensor. The arrow abstracts the presence of an associated transducer, which is realized e.g. in silicon by means of etching technology. Etching technologies of this type for different systems are known in the prior art. In particular, a linear acceleration sensor LA is represented. A positive sign implies in this case acceleration in the direction of the arrow. A yaw rate sensor AT is represented by a circle about an arrow, and the direction of rotation is clockwise in the direction of the arrow. This corresponds to the so-called ‘right-hand rule’, according to which the fingers of the right hand indicate the direction of rotation when the thumb is pointing in the direction of arrow. A yaw acceleration sensor AA is represented by two circles about an arrow, and the yaw acceleration is clockwise about the direction of the arrow. 
         [0026]      FIG. 1   b  illustrates the directional characteristics explained with respect to  FIG. 1   a  for better explanation with reference to a system of coordinates. With reference to the XY-plane, the arrow  1  symbolizes a yaw acceleration sensor being responsive to the X-direction. The arrow  2  refers to a linear acceleration sensor being responsive to the Y-direction. Finally, arrow  3  designates a yaw rate sensor being responsive to the Z-direction. Assuming that the silicon substrate as a chip is placed in the XY-plane, the directions of measurement of the transducers for yaw acceleration AR  1  and linear acceleration AA 2  are ‘in plane’ and the transducer for the yaw rate AA 3  is ‘out of plane’ according to the technically customary designation. 
         [0027]      FIGS. 2   a  to  2   d  represent the components of the sensor arrangement. The represented structures relate to embodiments based on micromechanical systems being made on the basis of silicon. Techniques of this type are known to one skilled in the art and can be adapted so as to conform to the respectively prevailing case of application of the invention. 
         [0028]      FIG. 2   a  shows a silicon chip  4  with an integrated structure of yaw rate sensor  5 , linear acceleration sensor  6 , yaw acceleration sensor  7 , and linear acceleration sensor  8 . Surfaces  5   a,    6   a,    7   a,    8   a  symbolize associated transducer chip surfaces. A surface  4   a  symbolizes a co-integrated electronic circuit for operation or pre-stage operation of the transducers  5 ,  6 ,  7 . In a favorable case of application, this component is employed as a cased inertial analyzer for an ESP application combined with a rollover protection. For this purpose, the chip plane is aligned in parallel to the vehicle plane or the earth&#39;s surface. The direction of measurement of the sensors  7 ,  8  is identical with the driving direction of a vehicle into which the sensor arrangement is mounted. The inertial analyzer detects—in relation to the vehicle—the yaw rate, the roll acceleration, the longitudinal acceleration, and the lateral acceleration. This embodiment represents a favorable combination of known sensors with a yaw acceleration sensor  7 . 
         [0029]      FIG. 2   b  shows a diagrammatic view of a frequently required, reduced embodiment of the inertial analyzer of  FIG. 2   a.  The analyzer comprises a chip  9 , a yaw rate sensor  10 , a linear acceleration sensor  11 , and a yaw acceleration sensor  12 . The direction of measurements of the sensors  10 ,  11 ,  12  are oriented exactly as the directions of measurement of the corresponding sensors  5 ,  7 ,  8  of the inertial analyzer described in  FIG. 2   a.    
         [0030]      FIG. 2   c  shows a component with a chip  13 , a linear accelerator sensor  14 , a yaw acceleration sensor  15 , and a yaw rate sensor  16 . The directions of measurement of all three sensors  14 ,  15 ,  16  are realized corresponding to the definition ‘out of plane’, which has been described hereinabove. 
         [0031]      FIG. 2   d  shows a component with a chip  17 , which comprises a linear accelerator sensor  18 , a yaw rate sensor  19 , and a yaw acceleration sensor  20 . The directions of measurement of all three sensors are realized corresponding to the definition ‘in plane’, which has been described hereinabove. 
         [0032]    In a possible embodiment of the invention, it is arranged that a chip  13  and two chips  17  are combined with each other in such a manner that an inertial analyzer develops which measures in all three directions in space the yaw rate, the linear acceleration, and the yaw acceleration in addition. The three chips are aligned ‘in plane’ for this purpose. In this arrangement, the two chips  17  rotate at a right angle relative to each other in plane so that their sensorial directions of measurement are aligned normal to each other and orthogonal to the directions of measurement of the sensors on the chip  13 . 
         [0033]      FIG. 3  shows schematically in several embodiments the integration of several monolithic sensor arrangements of the invention in one single packaging casing. 
         [0034]    In  FIG. 3   a,  a casing  21  encloses a sensorial component  24  of the type described in connection with  FIG. 2   a  or  FIG. 2   b,  as well as an associated separate electronic circuit  25 , which evaluates the sensor output signals. 
         [0035]    In  FIG. 3   b,  a casing  22  encloses a sensor component  26  of the type described in connection with  FIG. 2   a  or  FIG. 2   b,  as well as an associated separate electronic circuit  28 , which evaluates the sensors of the component  26 . The sensor component  26  comprises a co-integrated electronic circuit  27 . 
         [0036]    In  FIG. 3   c,  a casing  23  encloses two sensor components  29   a,    29   b  according to  FIG. 2   d,  a component  30  according to  FIG. 2   c,  as well as an associated separate electronic circuit  31 . The sensorial components  29   a,    29   b,    30  can contain additional co-integrated electronic circuits. This arrangement is a defined embodiment of an inertial analyzer, which measures the yaw rate, the linear acceleration, and the yaw acceleration in all three directions of space.