WO2010105848A1 - Calibration of weight-force measurements for seats - Google Patents

Abstract

The invention relates to a calibration device (20) for calibrating a weight-force sensor of a seat (8), having an apparatus (1) for exerting pressure onto the seat (8). The calibration device comprises a force sensor (3, 4) for measuring the exerted pressure onto the seat (8) and a force control for controlling the pressure exerted onto the seat (8) in consideration of a measured value of the force sensor (3, 4). The calibration device (20) is characterized in that the device (1) for exerting pressure onto the seat (8) comprises a linear drive (1). Further, the invention also has the aim of providing a corresponding calibration method and a calibration system which includes the calibration device.

Description

Calibration of weight measurements for seats

The invention relates to a calibration device for calibrating a weight force sensor of a seat, in particular a vehicle seat, a method for calibrating a corresponding weight force sensor with such a calibration device and a calibration system comprising a KaI ibriervorrichtung invention.

It is generally known to equip seats for motor vehicles, in particular the passenger seat, with a weight measuring system. This should in particular make it possible to adapt belt tightening and airbag ignition to the weight of the person in the seat. In the USA, the equipment is compulsory with a corresponding weight measuring system in accordance with the "Car Safety Standard - FMVSS-208" guideline.

Widespread is about the PODS system ("Passive Occupant Protection System") of the company Delphi. This system is installed by various manufacturers worldwide in seats for weight measurement. The PODS system includes a flat gel-filled cushion for insertion into the seat below the seat surface with built-in pressure sensors and an electronic control unit. When weight is applied, the Pressure sensors increase the pressure and the control unit evaluates the measurement. In particular, the classes "not occupied", "adult" and "toddler" are distinguished.

The control unit of the PODS system can then communicate the result of the force measurement via a CAN interface to other control units of the vehicle. For example, the airbag should be switched off when a child is sitting in the passenger seat.

The weight system is calibrated after the final assembly of the seat.

A corresponding calibration must be carried out according to the strict specifications of the sensor manufacturer Delphi Delco Electronics Europe GmbH for each passenger seat.

For this purpose, different pressures are applied with a device for applying pressure at different locations of the seat. In this way, the weight should be simulated.

It is known to generate the required force via a pneumatic cylinder. The pressure on the seat is adjusted by a change in the pressure within the pneumatic cylinder. The load is carried out by pressing a pressure plate on the seat. It is necessary to control the force applied to the pneumatic cylinder. This is mainly because the applied force is usually not linearly dependent on different sizes and in particular also non-linearly related to the indentation depth in the seat. In addition, the force to be exerted depends on the location of the seat to which the Calibration device currently acts, and finally, the properties can also change from seat to seat.

Because the calibration process takes place, in particular in the USA, for every single installed passenger seat, it is desirable to be able to carry out the calibration process particularly quickly, in a short cycle time. Since safety-relevant aspects are touched, a certain degree of precision is necessary.

The object of the invention is to provide a calibration device with which the calibration process can be carried out particularly quickly and also precisely. It is also intended to specify a corresponding calibration method and a corresponding calibration system.

The object is achieved by a calibration device for calibrating a weight sensor of a seat with a device for exerting pressure on the seat. For this purpose, the calibration device comprises a force sensor for measuring the pressure exerted on the seat and a regulation for regulating the pressure exerted on the seat Considering a measured value of the force sensor. The calibration device is characterized in that the means for exerting pressure on the seat comprises a linear drive.

Preferred embodiments of the invention are specified in the dependent claims.

The invention is based on the finding that per seat several points are to be loaded with different pressure. Accordingly, a comparatively large two-dimensional parameter space is passed through. Total calibration time can quickly add up to several minutes even if every single measurement (specific location of the seat with certain pressure) only takes a few seconds.

The invention is further based on the observation that the time per calibration point depends significantly on the time required for the force control.

It has further been recognized that the control time and precision is significantly affected by the use of pneumatic cylinders known in the art.

Calibration by means of pneumatic cylinders is susceptible to pressure fluctuations in the pneumatic system of the entire system. In addition, it is difficult to adjust pressure changes in the pneumatic cylinder sufficiently accurately to achieve satisfactory accuracy.

Overall, results from these disadvantages a comparatively long settling time for the scheme.

The invention is based on the idea of using a linear drive for exerting pressure on the respective seats instead of the pneumatic cylinder. This eliminates the disadvantages associated with the use of pneumatic cylinders. In other words, the invention is based on the idea, as a control variable for the control not - as in a pneumatic cylinder - to use a force change.

There are different technologies available for the linear drive. Basically, about a worm gear or a threaded rod drive or a linear motor, in particular an electric linear drive, come into question. Essential for the invention is that not, as in a Pneumatic cylinder, a force is regulated, but the positioning of the linear actuator. It is therefore also possible to speak of an "immediate" positioning, since the linear drive acts on the positioning without a detour, for instance via the build-up of pressure in a pressure cylinder; the manipulated variable can be, in particular, positioning or position change of the linear drive.

Basically, it applies that it has a positive effect on the success of the invention, when the linear drive has a high resolution. Accordingly, then sufficiently small changes in force can be made via the control variable of the control. The predetermined force setpoint can then be reached quickly.

If a linear drive is used, the adjustment of the force to apply pressure to the seat, preferably by a method of linear drive. It is therefore implemented a positioning or a change in length or position change in a force change. For reasons of linguistic simplicity, the linear element of the linear drive to be traversed is referred to as a push rod. In these words, therefore, a certain force is set by positioning or moving the push rod.

In this respect, one should not speak of a direct force regulation; Rather, the positioning is controlled by the linear drive, which then indirectly, via the push rod, determines the depth of depression in the seat, and thus ultimately indirectly the force exerted on the seat force. For reasons of linguistic simplicity, however, this application also refers to a force regulation or a "regulation for regulating the pressure exerted on the seat" or else to a "regulation of the pressure exerted on the seat". It turns depending on the Eindrückiefe a force exerted by the seat counterforce. The relationship is usually not linear.

Since linear drives can be positioned very accurately and quickly, small path differences can be set accurately and quickly. The depth of depression in the seat can thus be adjusted very accurately and quickly. This means, finally, that the force resolution can be very good.

The seat facing the end of the push rod may be widened, such as a pressure plate to distribute the pressure on a desired part of the surface of the seat. When changing the indentation depth of the pressure plate in the seat results in a corresponding change in force. The linear drive implements the control variable accordingly.

Overall, with the invention possible specifications regarding the interval of the expended forces and the tolerance in the application of force can be met very quickly and accurately.

Calibration devices according to the invention were in cooperation with the Daimler AG manufactory

Interior components (location Sindelfingen) produced and already successfully tested.

Preferably, the force sensor is installed in series with the linear drive. For this purpose, the force sensor may be installed, for example, in the push rod or between the pressure plate and the push rod. If the force sensor is installed in series with the linear drive, it can directly, for example, via the linear drive and / or the push rod on the seat measure applied force. The measurements of such a force sensor can be used directly as actual values for the control without further conversions.

The force sensor may comprise a strain gauge. Such force sensors can be made particularly cheap and are also relatively robust.

In a particularly preferred embodiment of the invention, the calibration device has a second force sensor for checking the first force sensor.

With the second force sensor, the first force sensor can be monitored particularly effectively. Conventional calibration devices are checked with a balance after each measurement. For this purpose, such conventional calibration devices must be moved laterally, since the balance is usually positioned next to the seat to be calibrated. The check is then carried out by comparing the measured values of the force sensor and the balance. The lateral procedure of the calibration device and the verification with the help of the balance is completely in the cycle time.

However, if the calibration device itself has two force sensors, then one of the two force sensors can act as actual value transmitter and this can be checked by the further force sensor. Particularly advantageous is an embodiment in which both force sensors are installed in series with the linear drive. For example, both force sensors can be installed in each case within the push rod one behind the other.

Such a design allows not only a review of the iswertgebenden force sensor following each clock, but even while pressure is exerted on the seat to be measured via the calibration device. Such a check can even be carried out constantly. Since the check can be carried out parallel to the control, the check here does not extend the cycle time; the calibration can be significantly shortened.

Overall, any, any cyclic or permanent check of the actual value can be carried out particularly time efficient.

The results of the two force sensors are compared with each other by means of a control device. The result of this comparison can be used to intervene in the calibration if necessary. For example, the calibration process can be aborted if the measurements of the two force sensors deviate too much from each other.

The check may relate both to the accuracy of the force measurements and more fundamentally to the measuring capability per se.

The object is also achieved by a method for calibrating a weight sensor of a seat with a calibration device according to the invention. A method according to the invention comprises the following steps: applying pressure to the seat, measuring the pressure applied to the seat with a force sensor, regulating the pressure exerted on the seat taking into account a measured value of the force sensor. The method is characterized in that the pressure on the seat is generated by means of a linear drive. The object is additionally achieved by a calibration system with a calibration device according to the invention. The calibration system is designed to carry out a method according to the invention.

Preferably, the calibration system comprises a portal for positioning the calibration device. For this purpose, the calibration device is suspended in the portal and can be moved via drives of the portal, so that the calibration device can take all the positions required for the measurements.

The calibration system preferably further comprises a balance. The scale can also be used to check the calibration device. If a second force sensor is present in the calibration device, these two sensors may already be mutually monitoring each other, nevertheless it may be necessary to check the calibration device as a whole from time to time. This can happen, for example, after a larger number of seats has been calibrated with the calibration device.

The portal of the calibration system can be used to move the calibration device and place it on the scale.

The aspects disclosed in the preceding and following description relate to both the calibration device, the calibration method and the calibration system, although this is not always explicitly stated. In principle, the individual features can also be essential to the invention in combinations other than those shown. In the following, the invention will be explained in more detail with reference to exemplary embodiments, without wishing to restrict the invention by the examples:

FIG. 1 shows a calibration device according to the invention.

FIG. 2 shows the calibration device from FIG. 1 together with further components of a calibration system according to the invention.

FIG. 3 shows an XY portal for a calibration system according to the invention.

For the same or corresponding features, the same reference numerals are used across the figures.

In the left part of Figure 1, a arranged over a seat 8 calibration device 20 is shown. The calibration device 20 comprises a linear drive 1, which is here aligned perpendicular to the seat with a push rod 2. At the end of the push rod 2, a pressure plate 6 is installed with the shape of a large B. In the push rod 2, a first force sensor 3 and a second force sensor 4 are installed. If the pressure plate 6 is pressed by means of the linear drive via the push rod 2 on the seat 8, so measure the two force sensors 3 and 4, the force exerted. Both force sensors include strain gauges (not shown). Rods 5 extend laterally on both sides of the linear drive 1 or the push rod 2 through a guide 9. These additional rods 5 serve for the stability of the calibrating device or for protecting the force sensors 3 and 4 from transverse forces.

In the right part of Figure 1, a control console for controlling the calibration device 20 can be seen. FIG. 2 schematically shows the calibration device 20 from FIG

I above a seat 8. Also, the control console 7 of Figure 1 is shown here.

The pressure plate 6 is tiltable in the sitting direction forward or backward about an axis. The current tilt angle is measured via an angle sensor 12. The measured values of the force sensors 3 and 4 and the angle sensor 12 are fed to a control and control device 10, 14; as well as the console 7 is connected to this. Furthermore, the signal from six laser path sensors 13 is read out via this device 10, 14. About these sensors 13, the most accurate position and adjustment of the seat 8 is measured. About drives

II, the calibration device 20 is moved laterally in an XY portal (see FIG. In addition, the calibration system includes other useful features such as a scanner 16, a handheld scanner 17, and a label printer 18.

FIG. 3 shows an XY portal for the lateral method of a calibration device according to the invention. Here one recognizes the calibration device 20 from FIGS. 1 and 2, which is suspended in the XY portal and can be moved horizontally along rails 21 and 22 in two dimensions.

Within the portal there is also an additional balance (not shown) to repeatedly check the calibration device 20 using the balance. This should always be done after a larger number of calibrations.

The calibration procedure is explained in more detail using the example of a passenger seat. The calibration must be carried out after the final assembly. Before the calibration, the passenger seat is brought into the calibration position with its adjusting motors for the back, height adjustment, inclination, longitudinal adjustment and seat cushion depth adjustment (drives not shown). After calibration, the desired delivery position is set. With laser path sensors (see Figure 2), the position of the seat is measured as accurately as possible at six different locations. The drive commands for the individual seat axes receives the control unit of the seat (not shown) via a second CAN interface.

During calibration, different forces must be exerted one after the other on this seat at different points in the seat. The force setpoint values can be predefined from a range of 0 to 1,000 Newtons.

The introduction of the force in the seat via the above-illustrated linear actuator via the push rod. A change in the force is adjusted via a method, ie a change in position, the push rod. The more the push rod presses into the seat, the greater the force exerted.

The two force sensors installed in the push rod in series with the linear drive can monitor each other. One of the two force sensors serves as an actual value transmitter for the force control for the linear drive. The control compares the force setpoint with the force actual value and calculates a new control value per control cycle for the force unit (the linear drive). Which force setpoint values are used for calibration for which seat variants is transmitted for the

Production control competent computer (14 in Figure 2). The parameter tables with the setpoints are managed in the application and are stored on the same computer 14.

After completion of the calibration and testing, the application returns the results to the production control. The results of the tested seats are used to control post-processing.

The passenger seats are transported fully automatically to the calibration system on a workpiece carrier before calibration, where they are positioned and contacted. After calibration, the front passenger seat is transported on the same workpiece carrier and arrives together with the remaining seats in the vehicle final assembly.

The measuring system may, for example, have a 19-inch industrial PC. Here all signals can converge. The industrial PC can be installed in a control cabinet, which can be integrated compactly into the calibration system. It makes sense to program the software applications for the test automation with LabView. The application has a modular design so that it can be adapted to different applications. The most important modules are: test sequence frame; Function library of the individual test steps; (PID) control, • Parameter management; Version management; Result Management; Statistical analysis; User management; User interface.

Overall, the invention allows precise calibration of seats with a short total cycle time. Demanding requirements can also be met, such as: - A variable setpoint specification over a wide range of forces;

- low tolerances regarding compliance with these specifications;

- quickly reaching the setpoints within the required tolerance;

- Cyclical checking of the actual value of the control.

Claims

claims A calibration device (20) for calibrating a weight force sensor of a seat (8) having means (1) for applying pressure to the seat, a force sensor (3, 4) for measuring the applied pressure on the seat (8) and a controller for controlling the pressure exerted on the seat (8) taking into account a measured value of the force sensor (3, 4), characterized in that the device (1) for exerting pressure on the seat (8) comprises a linear drive (1). 2. Calibration device (20) according to claim 1, wherein the linear drive (1) comprises a push rod (2) for exerting pressure on the seat (8) and is adapted to the pressure on the seat by direct positioning of the push rod (2 ). 3. Calibration device according to claim 1 or 2, wherein the force sensor (3, 4) is installed in series with the linear drive (1). 4. Calibration device according to one of claims 1 to 3, wherein the force sensor (3, 4) comprises a strain gauge. 5. Calibration device according to one of the preceding claims with a second force sensor (3, 4) for checking the first force sensor (3, 4). 6. Calibration device according to claim 5, wherein the second force sensor (3, 4) is installed in series with the linear drive (1). 7. Calibration device according to one of the preceding claims, designed for carrying out a method according to one of claims 8 to 14. 8. A method for calibrating a weight force sensor of a seat with a calibration device (20) according to any one of claims 1 to 7 with the steps: Exerting pressure on the seat (8), Measuring the pressure exerted on the seat (8) with a force sensor (3, 4), Regulation of the pressure exerted on the seat taking into account a measured value of the force sensor (3, 4), characterized in that the pressure on the seat by means of a linear drive (1) is generated. 9. The method of claim 8, wherein the linear drive (1) comprises a push rod (2) for applying pressure to the seat (8), comprising the step: Regulation of the pressure exerted on the seat (8) Position the push rod (2). 10. The method of claim 9, wherein the force sensor (3, 4) measures the pressure on the seat (8) in series with the linear drive (1). 11. The method of claim 9 or 10, wherein the calibration device in addition to the first force sensor (3, 4) still a second force sensor (3, 4) and with the second force sensor (3, 4) of the first force sensor (3, 4) is checked. 12. The method of claim 11, wherein the second force sensor (3, 4) measures the pressure on the seat (8) in series with the linear drive (1). 13. The method of claim 11 or 12, wherein the first force sensor (3, 4) by means of the second force sensor (3, 4) is repeatedly checked during operation. 14. The method according to any one of claims 11 to 13, wherein the first force sensor (3, 4) by means of the second force sensor (3, 4) is checked parallel to the control. 15. The method according to any one of claims 11 to 14, wherein when exceeding a predetermined deviation of the two force sensors (3, 4) from each other, the process is terminated. 16. Calibration system with a calibration device according to one of claims 1 to 7 for carrying out a method according to one of claims 8 to 15. 17. Calibration system according to claim 16 with a portal for positioning the calibration device relative to the seat. 18. Calibration system according to claim 16 or 17 with a balance for repeated checking of the calibration device (20).