Inertial sensor system for missiles

Abstract

Inertial sensor system (10) for use in an inertial navigation system of a missile (100), comprising: an inertial sensor (1); a temperature sensor (2) which is designed to measure a sensor temperature of the inertial sensor (1); an ambient temperature sensor (3) which is designed to measure an ambient temperature of the inertial sensor system (10); a sensor heater (4) which is designed to heat the inertial sensor (1); a control unit (5) which is designed to heat the inertial sensor (1) as a function of the measured ambient temperature by means of the sensor heater (4) such that the sensor temperature of the inertial sensor (1) reaches a predetermined first calibration temperature, wherein the control unit (5) is designed to increase the sensor temperature of the inertial sensor (1) to a second calibration temperature that is next higher than the measured ambient temperature if the measured ambient temperature exceeds the first calibration temperature; and a printed circuit board (7) on which the inertial sensor (1) is implemented, wherein the sensor heater (4) in the circuit board (7) is formed as a meandering conductor track in a copper layer directly below the inertial sensor (1).

Description

The invention relates to an inertial sensor system for missiles and to a missile having such an inertial sensor system.Light missiles, such as guided missile or guided missile, are often equipped with an inertial navigation system (INS). A central component of such an INS is an inertial measurement unit (IMU), which is equipped with acceleration sensors and rotation rate sensors and the like, which are generally referred to below as inertial sensors.Inertial sensors, in particular inexpensive commercial sensors, usually exhibit a strong temperature dependence with respect to the measured variables and their measurement errors. In order to compensate for this dependency, the sensors can be calibrated over a selected temperature range, for example by discrete calibration temperatures being approached in a temperature and / or climate chamber and compensation variables being created on the basis of the measured deviations from the setpoint values. However, the inertial sensors, which are frequently already integrated in an IMU in measurements of this type, assume the applied temperatures only very slowly and imprecisely. In addition, the inertial sensors or the IMU itself generate heat. This makes the calibration time-consuming and error-prone. Moreover, under realistic conditions, only a finite number of calibration points can be evaluated, so that intermediate temperature values have to be interpolated, which can in turn lead to residual errors. The expensive measurements and associated challenges can easily eliminate the cost advantages of commercial sensors.Temperature stabilization is sometimes proposed at the system level, i.e. at the level of the IMU higher-order than the inertial sensors, see, for example, the publications U.S. Pat. No. 8,558,150 B2 and U.S. Pat. No. 6,778,908 B2.US 2017 / 0 122 976 A1 describes a system for improving the accuracy of a motion or orientation sensor, wherein the system is designed for controlled heating of a device in a housing to a desired temperature dependent on the ambient temperature. The operating temperature of the device can then be known and controlled. The ambient temperature may be known, for example, by an ambient temperature sensor. From this information, a controller compensates the data output from the device to further improve the accuracy of the measurements. The level of the compensation, like the heating power supplied to the arrangement, depends on the ambient temperature and / or the device temperature.JP 2005-308 689 A describes a sensor having more stable output characteristics as compared with conventional types with respect to temperature changes in the environment in which the sensor is used.The publication EP 3 002 563 A1 describes a housing for the thermal stabilization of a temperature-sensitive component on a printed circuit board.The publication DE 10 2016 209 658 A1 describes a sensor arrangement having a micromechanical sensor element and a sensor space surrounded by a housing, in which the micromechanical sensor element is hermetically sealed, the sensor space being filled with a gas medium and having a predefined internal pressure. In this case, a compensation device is provided which adjusts and keeps constant the internal pressure in the sensor space as a function of at least one adjustment criterion.Against this background, the present invention is based on the object of finding improved solutions for inertial sensor systems which have the lowest possible susceptibility to errors in the event of temperature changes and are easy to calibrate.According to the invention, this object is achieved by an inertial sensor system having the features of patent claim 1 and by a missile having the features of patent claim 5.An idea underlying the present invention is to control the temperature of the individual inertial sensor or sensors of an inertial sensor system and not merely to regulate or stabilize the temperature at the system level. In this case, the temperature of the inertial sensor or sensors is measured using dedicated temperature sensors. The ambient temperature can be measured with an additional sensor element in an unheated area of the inertial sensor system. Among other things, the sensor temperature of each inertial sensor can be adjusted specifically to a specific, suitable calibration point depending on the ambient temperature. Due to this active adaptation of the temperature on an individual sensor level, modeling errors or interpolation errors (e.g. calibration) are avoided or at least reduced to a considerable extent. For example, at a specific ambient temperature, the closest (higher or equal) calibration temperature can be set as the sensor temperature. Due to the active heating, this can take place very quickly, for example within a few seconds. Since the inertial sensor has been calibrated at this calibration temperature, interpolation is therefore dispensed with as soon as the inertial sensor has reached this temperature, and the sensor operates in a well-defined state. At best, during the very short heating phase, it may be necessary to interpolate between calibration points. The calibration itself can also be significantly accelerated on the basis of the invention, since when a predetermined temperature level is approached in a temperature chamber, it is not necessary to wait until a temperature equilibrium of the system has been established. Rather, the temperature of each sensor element can be controlled in a targeted manner. The active temperature control also enables smaller, more cost-effective designs and avoids complicated thermal insulations. Corresponding sensor elements can be formed with a low heat capacity, so that they can be heated particularly quickly and efficiently.Advantageous embodiments and refinements emerge from the further dependent claims and from the description with reference to the figures.According to the invention, the sensor heater is designed to directly heat the inertial sensor. The sensor heater is configured directly below the inertial sensor for this purpose.According to the invention, a printed circuit board is provided on which the inertial sensor is implemented. The sensor heater is formed in the printed circuit board directly below the inertial sensor. In principle, it is possible to implement all elements of the inertial sensor system on such a printed circuit board or printed circuit board. The special arrangement of the sensor heater enables a direct and efficient heating of the corresponding inertial sensor.According to the invention, the sensor heating is designed as a meandering conductor track. The sensor heater is specifically designed as a copper layer. Such an implementation of the heating as a conductor plane or conductor track in a printed circuit board and / or printed circuit board is cost-effective and does not require any additional or special manufacturing steps. For example, an additional copper layer can be embedded in a printed circuit board for this purpose, in which conductor tracks are embodied as meandering heating windings. These heating windings can each be placed directly under the (e.g. soldered) sensor modules. A current regulator or the like can be controlled via the control unit, which in turn controls the heating winding, so that the inertial sensor is held at a predefined sensor temperature in this way.According to one refinement, the control unit may be designed to keep the sensor temperature of the inertial sensor at the first calibration temperature by means of the sensor heater. The sensor heater can thus be used to locally heat the inertial sensor to a defined temperature level and stabilize it there.According to the invention, the control unit is designed to increase the sensor temperature of the inertial sensor to a second calibration temperature which is the next higher than the measured ambient temperature if the measured ambient temperature exceeds the first calibration temperature.According to one refinement, the temperature sensor may be integrated into the inertial sensor. For example, the temperature sensor can be designed as a temperature sensor directly in, on or at the temperature sensor.According to one refinement, a plurality of inertial sensors may be provided, each having an associated temperature sensor and / or having an associated sensor heater. Accordingly, in such refinements, a control unit can be provided for each inertial sensor. Alternatively, however, a central control unit can also control or regulate the inertial sensors independently of one another. For example, all inertial sensors of an inertial sensor system, e.g., three (linear) acceleration sensors and three rotation rate sensors (gyroscopic sensors), may be designed correspondingly with an individual temperature sensor and an individual sensor heater. The inertial sensor system can have, for example, a central control unit for controlling or regulating all six inertial sensors. Alternatively or additionally, the six inertial sensors can each also be designed with an individual control unit. In principle, moreover, mixed forms are conceivable in which specific sensors are controlled and / or regulated jointly, e.g. a group of linear acceleration sensors and / or a group of rotation rate sensors, while other sensors have individual control units, e.g. a three-dimensional linear acceleration sensor and / or a three-dimensional gyroscopic sensor.The above embodiments and developments can be combined with one another as desired, if appropriate. Further possible embodiments, developments and implementations of the invention also include combinations of features of the invention described above or below with respect to the exemplary embodiments, which combinations are not explicitly mentioned. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.The present invention is explained in more detail below with reference to the exemplary embodiments indicated in the schematic figures. The following are shown: FIG. 1 shows a schematic perspective view of an inertial sensor system according to one specific embodiment of the present invention; FIG. 2 shows a schematic perspective view of an inertial sensor system according to a further specific embodiment of the present invention; FIG. 3 shows an exemplary sectional view of a missile with one of the inertial sensor systems from FIG. 1 or FIG. 2 ; and FIG. 4 shows a flow chart of a method for operating one of the inertial sensor systems from FIG. 1 or FIG. 2.The accompanying figures are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the advantages mentioned are evident with reference to the drawings. The elements of the drawings are not necessarily shown to scale with respect to each other.In the figures of the drawing, elements, features and components that are the same, have the same function and act in the same way-unless stated otherwise-are each provided with the same reference numerals.Missiles in the sense of the present invention include all ballistic or unguided missiles and guided missile which can move on determinable flight paths in and outside the airspace. Within the meaning of the present invention, missiles include, in particular, light drones, guided rockets, guided garnets, all types of marsh missiles, ground target missiles, air-ground rockets, anti-tank guided weapons, sea target missiles, air target missiles such as air-air rockets or anti-flight rockets, anti-rocket rockets and Antisatellitenraketen.An inertial measurement unit (IMU) in the sense of the present invention is a spatial combination of a plurality of inertial sensors such as acceleration sensors, rotation rate sensors and similar sensors. IMUs are sensory measurement apparatuses of inertial navigation systems ("inertial navigation system", INS), which are used, inter alia, in missiles for flight navigation and for regulation-technology stabilization of the missile in space. To detect six possible kinematic degrees of freedom, an IMU usually has at least three acceleration sensors (translation sensors) installed orthogonally to one another in each case for detecting the translatory movement in the x, y and z directions, and at least three rotation rate sensors (gyroscopic sensors) mounted orthogonally to one another for detecting rotating or gyroscopic movements about the x, y and z axes. IMUs can therefore provide as measured values at least three linear acceleration values for the translatory movement and at least three angular velocity values for the rotation rates. In an INS, the linear velocity along the trajectory and the position in space with respect to a reference point can be determined from the linear acceleration values, if appropriate after compensation of the gravitational acceleration. The integration of the three angular velocity values provides the orientation in space with respect to a reference point.FIG. 1 shows a schematic perspective view of an inertial sensor system 10 according to one specific embodiment of the present invention. The components of the inertial sensor system 10 shown in FIG. 1 are merely exemplary in nature and further components may be implemented in conjunction with the inertial sensor system 10 (see FIG. 2 ). The inertial sensor system 10 can be part of an inertial navigation system (INS), for example, which is designed for use in a missile. Such a missile 100, which may have the inertial sensor system 10, is illustrated by way of example in FIG. 3.Inertial sensor system 10 is designed for use in an inertial navigation system of missile 100. The inertial sensor system 10 comprises a printed circuit board 7 or printed circuit board, which can be mounted or mounted, for example, on a carrier platform (not shown) or the like, via which the inertial sensor system 10 can in turn be attached to a frame of the missile 100. The further components of the inertial sensor system 10 are implemented on this printed circuit board 7 and comprise an inertial sensor 1 with an integrated temperature sensor 2 and with a sensor heater 4 located under the inertial sensor 1, a control unit 5 with a current regulator 6 coupled thereto and an ambient temperature sensor 3. In principle, the inertial sensor 1 can be soldered onto soldering points on the printed circuit board 7 indicated by the dashed lines by way of example and in this way be thermally coupled directly to the sensor heater 4.The inertial sensor 1 is to be considered merely as representative of the plurality of inertial sensors that are usually present. For the sake of clarity, FIG. 2 shows a schematic perspective view of an inertial sensor system 10 according to a further specific embodiment of the present invention, which includes two inertial sensors 1, each of which is equipped with an integrated temperature sensor 2, a sensor heater 4, and a current regulator 6, and which are controlled or regulated jointly by a control unit 5. It will be clear to the person skilled in the art that a multiplicity of inertial sensors 1 can be configured in such a way or in a similar way within the meaning of the present invention. The inertial sensors 1 can be selected from various types. Each type of inertial sensor is a group of sensors designed to measure a specific inertial sensor parameter, such as linear acceleration sensors, rotational acceleration sensors, rotation rate sensors, gyroscopic sensors and similar sensor types. Inertial sensors within a group of sensors assigned to one type of inertial sensor may differ with regard to their measurement properties. For example, inertial sensors of the same type of inertial sensor may have different bandwidths, different vibration resistances, different acceleration resistances, different measurement accuracy, different temperature dependencies, etc.Referring again to FIG. 1, the temperature sensor 2 is designed to measure a sensor temperature of the inertial sensor 1. The ambient temperature sensor 3 is configured to measure an ambient temperature of the inertial sensor system 10. For this purpose, the ambient temperature sensor 3 is formed spatially clearly separate from the inertial sensor 1 and the sensor heater 4 on the printed circuit board 7 in an unheated region. In principle, it can be provided that the ambient temperature sensor 3 is designed to be thermally insulated from the sensor heater 4 in order to avoid corruption of the measured temperatures.The sensor heater 4 is designed as a meandering conductor track, e.g. made of copper, below the inertial sensor 1 and can be controlled by the current regulator 6 in order to heat the inertial sensor 1 to a predefined temperature in a targeted manner. The control or regulation of the current regulator 6 and of the sensor heater 4 is here taken over by the control unit 5.FIG. 4 shows a flow diagram of a method M for operating the inertial sensor system 10 from FIG. 1 or FIG. 2, the method M comprises under M 1 measuring a sensor temperature of the inertial sensor with the temperature sensor 2, the method M further comprises under M 2 measuring the ambient temperature of the inertial sensor system 10 with the ambient temperature sensor 3, the method M further comprises under M 3 heating the inertial sensor 1 with a sensor heater 4 as a function of the measured ambient temperature in such a way that the sensor temperature of the inertial sensor 1 reaches a first calibration temperature and is held at this calibration temperature. Finally, method M includes, under M 4, increasing the sensor temperature of inertial sensor 1 to a second calibration temperature if the measured ambient temperature exceeds the first calibration temperature.By way of example, a temperature control circuit based on these method steps could proceed functionally as follows. After an initialization of the system, e.g. during or before an inertial sensor measurement with the inertial sensor system 10 in or before the flight of the missile 100, the ambient temperature and the sensor temperature are detected. Based on a comparison of these two temperatures, the calibration temperature can now be selected which is next higher with respect to the measured ambient temperature. The control unit 5 now ensures, via the current regulator 6 and the sensor heater 4, that the current sensor temperature is brought as quickly as possible to this first calibration temperature. Accordingly, a current intensity of the current regulator 6 can be adjusted in order to bridge this temperature difference. Meanwhile, the temperature sensor and the ambient temperature sensor are continuously read out to track any temperature changes. As long as the ambient temperature remains below the set first calibration temperature, the sensor temperature is correspondingly maintained at the set calibration temperature. As soon as the ambient temperature exceeds the first calibration temperature, the control unit 5 again adjusts the sensor temperature so that a second calibration temperature is reached, which preferably corresponds to the calibration point that is the next higher than the current ambient temperature sensor.As a result, the sensor temperature of the inertial sensor or sensors 1 is (post)regulated immediately at any time, so that the inertial sensors 1 are at a known, calibrated temperature value and thus well-defined state as far as possible at any time, which does not require interpolation of the measurement results. Since the temperature control is carried out not at the system level but directly at the inertial sensors 1, measurement inaccuracies and errors are minimized in a very simple and efficient manner.In a corresponding manner, the above method can be used for a calibration of the inertial sensor system 10. In this case, the inertial sensors 1 are approached step by step with continuously increasing temperature values in order to record the behavior of the respective inertial sensor 1 at each of these calibration points and store it for future applications. The sensor heater 4 serves here to shorten the warm-up times between the respective calibration points. The calibration of the inertial sensor system 10 can thus proceed much more rapidly and efficiently than in conventional systems in which it is first necessary to wait at each calibration point until the system has set itself to the predefined temperature.In the foregoing detailed description, various features have been summarized to improve stringency of the representation in one or more examples. However, it should be understood that the above description is merely illustrative, not restrictive in nature. It is intended to cover all alternatives, modifications, and equivalents of the various features and embodiments. Many other examples will be immediately and immediately apparent to those skilled in the art from the knowledge of the art in view of the above description.The exemplary embodiments were selected and described in order to be able to best illustrate the principles underlying the invention and their possible applications in practice. This enables those skilled in the art to optimally modify and utilize the invention and its various embodiments with respect to the intended purpose of use. In the claims and the description, the terms "including" and "having" are used as neutral language terminology for the corresponding terms "comprising". Furthermore, a use of the terms "a", "an" and "an" is not intended to exclude a plurality of features and components described in this way in principle.List of reference characters1 Inertial sensor 2 Temperature sensor 3 Ambient temperature sensor 4 Sensor heater 5 Control unit 6 Current controller 7 Printed circuit board 10 Inertial sensor system 100 Missile M Method M 1 Method step M 2 Method step M 3 Method step M 4 Method step

Claims

Inertial sensor system (10) for use in an inertial navigation system of a missile (100), having: an inertial sensor (1); a temperature sensor (2) which is designed to measure a sensor temperature of the inertial sensor (1); an ambient temperature sensor (3) which is designed to measure an ambient temperature of the inertial sensor system (10); a sensor heater (4) which is designed to heat the inertial sensor (1); a control unit (5) which is designed to heat the inertial sensor (1) by means of the sensor heater (4) as a function of the measured ambient temperature in such a way that the sensor temperature of the inertial sensor (1) reaches a predefined first calibration temperature, wherein the control unit (5) is designed to increase the sensor temperature of the inertial sensor (1) to a second calibration temperature which is the next higher than the measured ambient temperature if the measured ambient temperature exceeds the first calibration temperature; and a printed circuit board (7) on which the inertial sensor (1) is implemented, wherein the sensor heater (4) is designed in the printed circuit board (7) as a meandering conductor track in a copper position directly below the inertial sensor (1).Inertial sensor system (10) according to Claim 1, wherein the control unit (5) is designed to keep the sensor temperature of the inertial sensor (1) at the first calibration temperature by means of the sensor heater (4).Inertial sensor system (10) according to Claim 1 or 2, wherein the temperature sensor (2) is integrated into the inertial sensor (1).Inertial sensor system (10) according to one of Claims 1 to 3, wherein a plurality of inertial sensors (1) are provided in each case with an associated temperature sensor (2) and / or with an associated sensor heater (4) in each case.Missile (100) having an inertial sensor system (10) according to one of Claims 1 to 4.

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