Patent Publication Number: US-2015068275-A1

Title: Test device simulating motor vehicle crashes and method for operating a test device

Description:
The invention relates to a test device for simulating motor vehicle crashes according to the preamble of patent claim  1  and to a method for operating a test device. 
     Accordingly, the invention relates to a test device for simulating motor vehicle crashes, with a slide arrangement which is arranged displaceably along a rail arrangement, a test rig which is arranged on the slide arrangement and on which at least one motor vehicle component to be tested is arranged or can be mounted, and with an acceleration unit via which a force is transmittable to the slide arrangement in order to accelerate the latter. 
     A test device of this type, which is also referred to in the specialist field as a servo-hydraulic or pneumatic catapult system, is generally known in terms of principle from vehicle engineering and serves to cope with the ever shorter development times in automobile manufacturing and the requirements for greater passive safety. With such a test device, inverse crash tests can be carried out. In such tests, the deceleration forces which can occur in normal operation or in the event of a crash do not act on the motor vehicle components to be examined. Instead, in inverse crash tests, the acceleration forces corresponding to the deceleration forces which can occur are introduced into the motor vehicle components to be examined. 
     As a rule, in this context the vehicle components to be examined, such as seats, steering columns and steering wheels, windshields, dashboards, seatbelts and the attachment means thereof, airbag systems and other components, are accelerated in a controlled manner, corresponding to the various accident situations, in a reinforced vehicle body, what is referred to as the tank, on a slide, and the fracture behavior or component reliability is examined. In conventional test devices, the slide is accelerated using, for example, a push rod which is part of an acceleration unit. In particular, it is known to move the push rod hydraulically or pneumatically out of a cylinder tube of a drive cylinder in accordance with a real deceleration curve. In order to be able to simulate the real deceleration curve, it is attempted here to control the hydraulic or pneumatic loading of the push rod by means of a valve. 
     In order to obtain a real deceleration curve, a very accurate acceleration profile for the loading of the push rod has to be ensured. It is known from the prior art to calculate this acceleration profile on the basis of applied air or fluid pressures. However, it has been shown that the pressure profiles numerically calculated in this respect frequently do not result in reproducible acceleration profiles of the slide arrangement. 
     On the basis of this problem, it is the object of the invention to develop a test device for simulating motor vehicle crashes of the type mentioned at the beginning and also a method for operating a test device of this type in such a manner that a simulation of accident situations can be improved in a way which is simple to implement, but is nevertheless reproducible. In particular, a test device is intended to be specified, with which, in comparison to conventional test devices, the reproducibility of the tests and the simulation accuracy of the tests can be improved, and the number of necessary iteration steps can be reduced. 
     With regard to the test device, this object is achieved according to the invention in that the test device has at least one sensor element for continuously detecting motion measured values of the slide arrangement. 
     The test device according to the invention has the advantage that, during the test, the instantaneous acceleration of the slide arrangement can be continuously measured. Accordingly, the simulation accuracy of the tests is greatly improved and the number of necessary iteration steps reduced. Furthermore, reliable test parameters can be determined and ensured by the test device according to the invention. 
     Advantageous developments of the test device according to the invention are specified in the dependent patent claims. 
     Provision is thus made, in a further implementation of the test device according to the invention, for the test device to furthermore have a regulating device for regulating the acceleration value of the slide arrangement. For this purpose, the regulating device is electrically connected to the at least one sensor element. Accordingly, it is conceivable to store the motion measured values of the slide arrangement, which are detected by the test device according to the invention, not only for documentation purposes but also to use said motion measured values for regulating the acceleration of the slide arrangement. According to this variant of the test unit according to the invention, the motion measured values of the slide arrangement, which are detected continuously by the at least one sensor element, are transmitted to the regulating device. The regulating device uses the associated motion measured values as a regulating variable in order, as an actuating variable, to regulate the acceleration of the slide arrangement. 
     Provision is in particular made here for the regulating device to be designed to regulate the force which is transmitted by the acceleration unit to the slide unit with reference to the motion measured values of the slide arrangement. Specifically, the force is regulated by the fact that the regulating device loads the acceleration unit with calculable pressures as the actuating value. In other words, the pressure which prevails at the acceleration unit can be controlled by the regulating device in order therefore to regulate the force, i.e. the acceleration too, which is transmitted by the acceleration unit to the slide unit. Of course, the test device according to the invention is not restricted here to a specific embodiment of the acceleration unit. Rather, the acceleration unit can provide a force for accelerating the slide arrangement by means of all conventional driving mechanisms (pneumatically, hydraulically, electrically, magnetically, etc.). 
     According to a next use of the test device according to the invention, provision is made for the test device to furthermore have a braking device which is connected to the regulating device and is configured for controlling the acceleration of the slide arrangement. By means of the provision of a braking device, the regulability of the desired acceleration profile can be further improved. As a result, the reproducibility of the desired acceleration profiles is advantageously greatly improved. Furthermore, it is conceivable for the braking device mentioned also to be used to brake the slide arrangement after the latter has passed through the desired acceleration profile. In other words, the regulating device can be used not only to increase the acceleration of the slide arrangement by influencing the acceleration unit, but also to reduce the acceleration of the slide arrangement if required. 
     In this case, provision is preferably made for the braking device to be designed as an eddy current brake. The test device according to the invention is thereby subject to a particularly small amount of wear, wherein a particularly rapid and precisely determinable braking power is obtained at the same time. Of course, it is also conceivable to configure the braking device as any other electromagnetic or mechanical brake or as a fluid brake. 
     According to a further alternative embodiment, the at least one sensor element for continuously detecting motion measured values of the slide arrangement has an acceleration sensor and/or a speed sensor and/or a position sensor. In this case, it is preferred in particular to configure the sensor element as an acceleration sensor. For example, it is conceivable in this case to design the acceleration sensor as a strain gauge and/or as a magnet which is moved in the electrical field of a coil. Further examples include the use of lasers, such as laser Doppler technology. If the motion measured value involves the acceleration of the slide arrangement, the regulating variable (motion measured value) can be directly compared with the desired value (sought acceleration profile). If, on the other hand, the motion measured value involves the position or the speed of the slide arrangement, this has to be recalculated beforehand by the regulating device. For example, it is conceivable in this connection for the at least one sensor element to be designed as a speed sensor and for the regulating device to continuously convert the detected speed profile into an acceleration profile of the slide arrangement. Furthermore, the speed profile just mentioned could be used at the same time by the regulating device to calculate absolute position measured values of the slide arrangement in real time. In other words, the regulating device can serve as a virtual sensor element which makes use of the actual measured values of the physical sensor element. 
     According to the invention, the abovementioned object is also achieved by a method for operating a test device for simulating motor vehicle crashes. In the method according to the invention, first of all a slide arrangement is accelerated with the aid of an acceleration unit, wherein motion measured values of the slide arrangement are recorded continuously with the aid of a sensor element. Said motion measured values are furthermore transmitted continuously to a regulating device, with the aid of which the force which is transmitted by the acceleration unit to the slide unit is regulated with reference to the motion measured values of the slide arrangement. The force which is transmitted by the acceleration unit to the slide arrangement can be regulated, in particular in real time, i.e. as the test proceeds, or else for the next test sequence after the end of the test. 
     Test parameters which are particularly readily reproducible can also be obtained by the method according to the invention. 
     According to a further embodiment of the method according to the invention, provision is made for a braking force which is transmitted to the slide arrangement with the aid of a braking device to be controlled with the aid of the regulating device with reference to the motion measured values of the slide arrangement. The acceleration profile, which has already been mentioned above, of the slide arrangement is therefore particularly reliably controlled, as a result of which test conditions which are very readily reproducible can be produced in an advantageous manner. 
    
    
     
       An exemplary embodiment of the test device according to the invention is described in more detail below with reference to the attached drawing, in which: 
         FIG. 1  shows a signal flowchart of an exemplary embodiment of the invention. 
     
    
    
       FIG. 1  is a schematic view of a signal flowchart of an exemplary embodiment of the test device  100  according to the invention. As illustrated, the test device  100  has a slide arrangement  110  and an acceleration unit  120 . The slide arrangement  110  and the acceleration unit  120  are connected by means of a force transmission device  121 . In the embodiment shown, the force transmission device  121  is a push rod or piston rod. A test object, for example a motor vehicle or components thereof, can be arranged on the slide arrangement  110 . 
     The acceleration unit  120  has a hydraulic or pneumatic drive cylinder  122  with a piston  123  and two control valves (first valve  124 , second valve  125 ). The piston  123  together with the piston rod  121  which is connected thereto can be displaced axially along the axis of the drive cylinder  122  and separates two cylinder regions, the piston-side cylinder region  128  and the piston-rod-side cylinder region  129 , from each other in a fluid-tight manner. 
     In particular, in the embodiment of the test device  100  according to the invention that is illustrated in  FIG. 1 , provision is made for the drive cylinder  122  to be embodied as a double-acting cylinder. In this case, that side of the first valve  124  which is not connected to the piston-side region  128  of the drive cylinder  122  is fluidically connected to a first fluid reservoir  140 . The first fluid reservoir  140  can be, for example, a piston storage unit. On the other hand, that side of the second valve  125  which is not connected to the piston-rod-side region  129  of the drive cylinder  122  is fluidically connected either to a second unpressurized fluid reservoir  141  or to a high-pressure fluid reservoir  170 , depending on the actuating signal. 
     Accordingly, a highly-pressurized fluid can be supplied via the first valve  124  to the piston-side region  128  of the drive cylinder  122  such that the pressure P1 prevailing in the piston-side region  128  of the drive cylinder  122  can be increased and a pressure force acting on the piston  123  and the piston rod  121  can be transmitted to the slide arrangement  110 . The slide arrangement  110  can thereby be accelerated. 
     In particular, the compressive force acting on the piston rod  121  is determined by the difference between the pressure P1 prevailing in the piston-side region  128  of the drive cylinder  122  and the pressure P2 prevailing in the piston-rod-side region  129  of the drive cylinder  122 . In addition, the active area which is present in the piston-side region  128  on the piston  123 , and the active area which is present in the piston-rod-side region  129  on the piston  123  influence the compressive force acting on the piston rod  121 . On the other hand, the side which is not connected to the piston-rod-side region  129  of the drive cylinder  122  can be brought into fluidic connection with the unpressurized fluid reservoir  141 . 
     As already indicated, fluid can flow into and out of the piston-rod-side region  129  of the drive cylinder  122  via the second valve  125 . In this way, the pressure P2 which occurs in the piston-rod-side region  129  and the resulting acceleration can be decisively influenced. In particular, so much pressurized fluid can flow out of the high-pressure reservoir  170  into the piston-rod-side region  129  of the drive cylinder  122  or can flow off into the unpressurized reservoir  141  via the valve  125  that the force exerted on the piston  123  via the pressure difference between the piston-side region  128  and the piston-rod-side region  129  brings about the desired acceleration of the slide arrangement  110  via the force transmission device  121 . 
     However, in order to be able to record the actual acceleration profile of the slide arrangement, the test device according to the invention has at least one sensor element  111 ,  112 ,  113 . The at least one sensor element can be a position sensor  111  and/or a speed sensor  112  and/or an acceleration sensor  113 . Accordingly, the at least one sensor element records, preferably continuously, motion measured values (position, speed or acceleration) of the slide arrangement  110 . 
     According to the preferred embodiment illustrated in  FIG. 1 , the motion measured values determined are transmitted directly to a regulating device  150  for regulating the acceleration of the slide arrangement  110 . For this purpose, said regulating device  150  is connected to the at least one sensor element  111 ,  112 ,  113 . The regulating device is furthermore connected to a control unit  160 , such as, for example, to a PC, via a signal-transmitting connection. Via the signal-transmitting connection, a desired variable for the acceleration of the slide arrangement, which desired variable can be defined in advance and can be input, for example, manually into the control unit  160 , is transmitted to the regulating device  150  by the control unit  160 . The desired variable can be a predetermined acceleration value or else also a predetermined acceleration profile (i.e. a predetermined variation of the acceleration over time). 
     The regulating device  150  is therefore configured to adjust a regulating variable in accordance with the desired variable. In a preferred embodiment of the test device  100  according to the invention, the regulating variable is the instantaneous motion measured value which is detected by at least one sensor element  111 ,  112 ,  113 . The motion measured value is either the position, the speed or the acceleration of the slide arrangement  110  depending on the sensor element  111 ,  112 ,  113 . If the motion measured value is the acceleration of the slide arrangement, said regulating variable can be directly compared with the desired value. If, on the other hand, the motion measured value is the position or the speed of the slide arrangement  110 , this has to be recalculated beforehand by the regulating device  150 . 
     The regulating device  150  is furthermore configured to regulate the force which is transmitted by the acceleration unit  120  to the slide unit  110  with reference to the motion measured values of the slide arrangement  110 . In other words, from the motion measured value(s) (regulating variable) and the desired value, the regulating device  150  generates an actuating variable which changes the flow rates through the two valves  124 ,  125  and therefore influences the pressures P1, P2 of the drive cylinder  122  by changing the quantity of fluid which is fed to the piston-side region  128 , or is discharged in the rod-side region  129 , per unit of time. 
     In various embodiments of the test device  100 , for example proportional (P) regulators, proportional integral (PI) regulators or proportional integral differential (PID) regulators can be used as the regulating device  150 . 
     The test device  100  shown furthermore has a braking device  114  for braking the slide arrangement  110  again during and/or subsequent to the test phase. The braking device  114  is in particular connected to the regulating device  150 , as a result of which the regulating device  150  can output a control signal for the braking device  114  as a second actuating variable. In other words, the regulating device  150  can be used not only to increase the acceleration of the slide arrangement  110  by influencing the acceleration unit  120  but also for reducing the acceleration of the slide arrangement  110 , if required. 
     Of course, it is alternatively also possible to configure the connection between the slide arrangement  110  and force transmission unit  121  in such a manner that, after the acceleration phase, the slide arrangement  110  becomes detached from the force transmission unit  121  by the piston  123  and is braked with suitable braking means independently of the piston  123  and of the force transmission unit  121 . 
     The schematically illustrated braking device  114  can advantageously be an eddy current brake. The test device  100  according to the invention thereby has particularly low wear, wherein, at the same time, a very rapid and precisely determinable braking power is obtained. Of course, it is also conceivable to configure the braking device  114  as any other electromagnetic or mechanical brake or else as a fluid brake. 
     As already mentioned above, the at least one sensor element  111 ,  112 ,  113  can be a position sensor  111  and/or a speed sensor  112  and/or an acceleration sensor  113 . In this case, it is preferred in particular to configure the at least one sensor element as an acceleration sensor  113 . For example, it is conceivable in this case to design the acceleration sensor  113  as a strain gauge and/or as a magnet which is moved in the electrical field of a coil. Further examples include the use of optical measuring technology, such as laser Doppler technology. Of course, the test device according to the invention is not restricted to a certain type of sensor element but may in principle use any measuring principle which is suitable for rapid detection of the motion measured values. 
     The invention is not restricted to the embodiment of the test device  100  that is described by way of example with reference to  FIG. 1 , but rather results from a combination of all of the features and advantages described herein.