"apparatus and method for detecting a time evolution of

Abstract

The invention relates to an apparatus (1) and a method for detecting a time evolution of an impact force generated by a free-falling impacting body (CI), wherein said apparatus (1) comprises a supporting base (11) that allows positioning a test body (CP) to be hit by said impacting body (CI), sensor means (12,13,14) configured to detect a force generated by a mass of said test body (CP) and by an interaction between said test body (CP) and the impacting body (CI), a platform (15) positioned above said supporting base (11), actuator means (16) able to keep said impacting body constrained to said platform, accelerometer means (17) configured to detect an acceleration to which said test body (CP) is subjected after being hit by the impacting body (CI) and to generate a second signal on the basis of said acceleration.

Description

[0001] TITLE: "APPARATUS AND METHOD FOR DETECTING A TIME EVOLUTION OF

[0002] AN IMPACT FORCE"

[0003] DESCRIPTION:

[0004] The present invention relates to an apparatus and a method for detecting a time evolution of an impact force generated by a free-falling impacting body, in particular by an impacting body that, following a first impact against a test body, generates one or more subsequent impacts and / or fragmentations / comminutions .

[0005] As is known, in order to improve the safety of a manufactured product (e.g. having a skeleton made of iron, reinforced concrete, wood, or another material) it is necessary to analyse how said manufactured product will behave when hit by an impacting body such as, for example, a stone coming off a landslide, detritus thrown when demolition work is carried out using explosives, a collapsing slab, etc.

[0006] One impact-related phenomenon which is most subject to attention is a collapse that propagates within a manufactured product following an impact. Indeed, knowing how such propagation phenomenon occurs makes it advantageously possible to identify a solution to stop such propagation, such as, for example, adequately oversizing a portion of the structure, using special joints, or the like.

[0007] In order to analyse how a collapse propagates, it is necessary to study the interactions between manufactured products and impacting objects (e.g. stones, detritus, slabs, etc.) that may break up and / or that may generate multiple impacts, since impacts of impacting objects mostly occur in portions thereof not coinciding with their centre of mass, resulting in partial energy dissipation and a high probability that the body will undergo further impacts and / or fractures or comminutions.

[0008] The present invention aims at solving these and other problems by providing an apparatus for detecting a time evolution of an impact force generated by a free- falling impacting body .

[0009] In addition, the present invention aims at solving these and other problems by providing also a method for detecting a time evolution of an impact force generated by a free- falling impacting body .

[0010] The basic idea of the present invention is to use sensor means ( e . g . load cells ) coupled to a supporting base and configured to detect a force generated by a mass of said test body and by an interaction between said test body and the impacting body, when said test body is positioned on the supporting base and hit by said impacting body, together with accelerometer means ( e . g . a piezoelectric accelerometer ) configured to detect an acceleration to which said test body is subj ected after being hit by the impacting body, wherein said sensor means are configured to generate a first signal and said accelerometer means are configured to generate a second signal .

[0011] This makes it possible to detect the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body . When the test body receives the f irst impact , in fact , it starts vibrating freely at its resonance frequency . When this occurs , the load cells will detect j ust a partial load, because the test body may not be able to fully trans fer to the load cel ls the forces it i s generating ( e . g . its weight force ) and those that are acting upon it ( e . g . the impact force generated by successive impacts against the impacting body or against portions of said impacting body) . The use o f accelerometer means overcomes this limitation, since it advantageously provides constant monitoring of the acceleration to which said test body i s subj ected, thereby advantageously identi fying the forces acting upon said test body according to the following relation : where (t) is the time evolution of a contact force between the impacting body and the impacted body, m is a mas s of the test body, a(t) is the time evolution ( detected by the accelerometer means ) of an acceleration of the impacted body, F(t) is the time evolution ( detected by the sensor means ) of a total force transmitted from the impacted body to the supporting base .

[0012] It is thus possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body .

[0013] Further advantageous features of the present invention are set out in the appended claims .

[0014] These features as well as further advantages of the present invention will become more apparent in the light of the fol lowing description of a preferred embodiment thereof as shown in the annexed drawings , which are provided herein merely by way o f non-limiting example , wherein :

[0015] - Fig . 1 shows a perspective view of an apparatus for detecting a time evolution of an impact force according to the invention;

[0016] - Fig . 2 shows a side view of the apparatus of Fig . 1 ;

[0017] - Fig . 3 shows a front view of the apparatus of Fig . 1 ;

[0018] - Fig . 4 shows a flow chart representing the phases of a method of detecting a time evolution of an impact force according to the invention;

[0019] - Fig . 5 shows a front view of a portion of the apparatus of Fig . 1 ;

[0020] - Fig . 6 shows a sectional view along plane A-A of Fig . 5 ;

[0021] - Fig . 7 shows a perspective view of an impacting body employed by the apparatus of Fig. 1;

[0022] - Fig. 8 shows a side view of the apparatus of Fig. 1 in an operating condition which is different from the one shown in Fig . 2.

[0023] In this description, any reference to "an embodiment" will indicate that a particular configuration, structure or feature is comprised in at least one embodiment of the invention. Therefore, expressions such as "in an embodiment" and the like, which may be found in different parts of this description, will not necessarily refer to the same embodiment. Moreover, any particular configuration, structure or feature may be combined as deemed appropriate in one or more embodiments. The references below are therefore used only for simplicity's sake, and shall not limit the protection scope or extension of the various embodiments .

[0024] With reference to Figures 1, 2 and 3, the following will describe an apparatus 1 for detecting a time evolution of an impact force generated by a free-falling impacting body CI; such apparatus 1 comprising the following elements:

[0025] - a supporting base 11, preferably made of concrete and preferably having a thickness of 40 cm and a rectangular base (e.g. having a width of 75 cm and a height of 55 cm) , which allows positioning a test body CP that will have to be hit by said impacting body CI, and wherein said test body CP preferably has a thickness equal to or greater than 10 cm and a base which is smaller than the supporting base 11;

[0026] - sensor means 12,13,14 (e.g. a load cell of the capacitive type or the like) configured to perform the following activities :

[0027] • detecting a force generated by a mass of said test body CP and by an interaction between said test body CP and the impacting body CI, when said test body CP is positioned on said supporting base 11 and hit by said impacting body CI ;

[0028] • generating a first signal on the basis of said force ;

[0029] - a platform 15 positioned above said supporting base 11 , preferably having a square or rectangular base ( e . g . a width of 55 cm and a height of 45 cm) , and preferably constrained to said supporting base 11 by constraining means 18a, 18b, 19a, 19b (which will be further described below) ;

[0030] - actuator means 16 , e . g . an electromagnet , able to keep said impacting body constrained to said platform, and configured to release said impacting body in free fall upon reception of a command signal ;

[0031] - accelerometer means 17 , e . g . a piezoelectric accelerometer, configured to perform the following activities :

[0032] • detecting an acceleration to which said test body CP is subj ected after being hit by the impacting body CI ;

[0033] • generating a second signal on the basis of said acceleration .

[0034] It must be highlighted that those skil led in the art may use alternative accelerometer means 17 other than a piezoelectric accelerometer ( for example, the acceleration of the test body CP could be detected by exploiting the variations in the flight time of luminous or electromagnetic radiations or acoustic pressure waves ) , without however departing from the teachings of the present invention .

[0035] Al so with reference to Fig . 4 , the following wi ll describe a method of detecting the time evolution of an impact force generated by the free- falling impacting body CI according to the invention .

[0036] When the apparatus 1 is in an operating condition, said apparatus 1 is used in order to execute the method according to the invention, which comprises the following phases :

[0037] - a preparation phase Pl , in which the test body CP is positioned on a supporting base , where said test body CP is to be hit by said impacting body CI , and in which said impacting body CI is constrained, by the actuator means 16, to the platform 15 positioned above said supporting base 11 ;

[0038] - a release phase P2 , in which the impacting body CI is released, by the actuator means 16 , in free fall towards the supporting base 11 after said actuator means 16 have received a command signal ;

[0039] - a first generation phase P3 , in which the first signal is generated, by the sensor means 12 , 13 , 14 , on the basis of the force generated by the mas s o f said test body CP and by the interaction between said test body CP and the impacting body CI , when said test body is positioned on said supporting base 11 and hit by said impacting body CI ;

[0040] - a second generation phase P4 , in which the second signal is generated, by the accelerometer means 17 , on the basis of the acceleration to which said test body CP is subj ected after being hit by the impacting body CI .

[0041] It must be pointed out that the first generation phase P3 and the second generation phase P4 are executed, at least partly, at the same time .

[0042] This makes it possible to detect the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body . In this way, it is possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body .

[0043] In combination with the above , the apparatus 1 preferably comprises also the following elements :

[0044] - computing means ( e . g . at least one CPU, one MCU, one GPU, or the like ) ; - input means (e.g. an analogue-to-digital converter connected to a communication interface) for acquiring the first signal and the second signal, wherein said input means are in communication with said computing means;

[0045] - transmission means (e.g. a USB, RS232, RS485, Ethernet interface or the like, which may coincide with the input means) for transmitting an output signal, preferably over a private or public communication network.

[0046] In addition, the computing means are preferably configured to execute the following steps:

[0047] - acquiring, via the input means, the first signal and the second signal;

[0048] - computing at least one contact force between the impacting body CI and the test body CP on the basis of said first signal and said second signal, e.g. by executing a set of instructions implementing the above formula (1) ;

[0049] - transmitting, via the transmission means (e.g. a USB, RS232, RS485, Ethernet interface or the like, which may coincide with the input means) , the output signal in which said at least one contact force is encoded, e.g. as a floating-point representation of said at least one contact force.

[0050] In other words, the method according to the invention preferably comprises also the following steps:

[0051] - an acquisition phase, in which the first signal and the second signal are acquired by the input means;

[0052] - a computing phase, in which at least one contact force between the impacting body CI and the test body CP is computed, by the computing means, on the basis of the first signal and the second signal;

[0053] - a transmission phase, in which an output signal, in which said at least one contact force is encoded, is transmitted by the transmission means. This facilitates the detection of the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body, since it is not necessary to (externally) acquire, in a synchronous manner, the signals of the sensor means 12,13,14 and of the accelerometer means 17 in order to subsequently determine the contact force between the impacting body CI and the test body CP. In this way, it is possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body.

[0054] Also with reference to Figures 5 and 6, the following will describe the preferred sensor means which can be used for implementing the invention.

[0055] In combination with or as an alternative to the above, the sensor means of the apparatus 1 preferably comprise at least three load cells 12, 13, 14 so positioned as to support the test body CP at the same time.

[0056] This particular arrangement of the load cells 12,13,14 advantageously allows an operator to position the test body in such a way that the centre of mass of the test body CP lies over the (geometric) centre of gravity of the figure (in this example, a triangle) having as vertices the (three) load cells 12, 13 and 14; when the test body CP is in this position, in fact, the weight force it generates is equally distributed among the three load cells 12, 13 and 14, so that said load cells 12, 13 and 14 will advantageously operate within the same detection range, thus making it possible to compare and combine (e.g. by means of an arithmetic sum) load data encoded in load signals generated by said load cells 12, 13 and 14 in a significant manner (i.e. without an excessive increase in the error associated with the detection / measurement ) , because such load data will be affected by similar detection / measurement errors.

[0057] In other words, each one of said at least three load cells 12,13,14 preferably generates a load signal and, during the preparation phase Pl of the method according to the invention, the test body CP is preferably positioned relative to the supporting base on the basis of said load signals, so that the force generated by the mass of said test body CP will be (evenly) distributed among said at least three load cells 12,13,14.

[0058] This improves the detection of the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body, because it reduces the load cells' measurement errors. In this way, it is possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body.

[0059] It must be pointed out that the test body CP may be laid onto the load cells 12,13,14 either during the preparation phase Pl or during the subsequent phases (i.e. when it is hit by the impacting body CI) . As an alternative, the test body CP may be constrained to the load cells 12,13,14, e.g. by means of threaded bars (each one coupled to one of said load cells 12, 13, 14) and nuts compatible with said threaded bars; in such a case, the body CP is preferably laid (whether directly or indirectly) onto the load cells 12,13,14 during the preparation phase Pl, when the best position of said test body CP is found as described above, and then the test body CP can be drilled and constrained to the load cells 12,13,14 by means of the threaded bars and the nuts .

[0060] However, those skilled in the art will be able to constrain the test body CP to the load cells 12,13,14 differently than described above (e.g. by means of screws, adhesive, etc.) without departing from the teachings of the present invention. In combination with or as an alternative to the above , the accelerometer means 17 are preferably configured to be positioned on the surface of said test body CP ( e . g . constrained by means of adhesive , a piece of double-sided adhesive tape , or the l ike ) in proximity to the centre of mas s o f said test body CP, i . e . as near as possible to the geometric centre of gravity of the surface of the test body CP to which said accelerometer means 17 are applied, when said test body CP is made of a material with uni form mass density . In other words , during the preparation phase Pl of the method according to the invention, the accelerometer means 17 are preferably positioned on the underside o f said test body CP, close to the centre of mass of said test body CP, e . g . by means of adhesive , a piece of doublesided adhesive tape, or any other means capable of constraining said accelerometer means to said test body 17 .

[0061] This improves the detection of the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body, because the real acceleration of the test body CP will be detected . In this way, it is possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body .

[0062] In combination with the above , the accelerometer means preferably comprise a piezoelectric accelerometer .

[0063] This type of accelerometer is particularly suitable for detecting the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body, because it has , advantageously, a very wide passband that makes it fit for impact analysis ; moreover, such an accelerometer is much lighter than the test body CP, and therefore cannot alter the results of the impact tests . Lastly, this accelerometer advantageously has no moving parts that might increase the moment of inertia of the test body, thus altering the results of the impact tests , especially in the presence of multiple impacts and / or f ragmentations / comminutions with lower energies and smaller masses than the main impact .

[0064] Also with reference to Fig . 7 , the impacting body CI may be pointed at one end, preferably at that end which will hit the test body CP ; in addition, said impacting body CI preferably has a smaller mass than the test body CP . In more detail , the impacting body CI comprises a constraining element attached to its surface , preferably a washer W of ferromagnetic material ( e . g . iron) suitable for interacting with the electromagnet , which preferably constitutes the actuator means 16 , by generating a force suf ficient to keep said impacting body CI constrained to said platform 15 .

[0065] Those skilled in the art may however employ a retaining system other than the one based on the electromagnet 16 and the washer W ( e . g . a command-openable hook constrained to the platform 15 and a li ft ring coupled to the impacting body) without departing from the teachings of the present invention .

[0066] In combination with or as an alternative to the above , the actuator means 16 are configured to vary their own position relative to the supporting base 11 and to the platform 15 ; for example , the actuator means 16 are constrained to the platform 15 by means of Velcro or a piece of double-sided adhesive tape , which allows moving the actuator means 16 , and hence the impacting body CI , so that said impacting body CI will , as soon as its free fall ends , hit the test body CP in proximity to the centre of mass o f the test body CP, i . e . as close as possible to the geometric centre of gravity of the surface of the test body CP that is receiving the impact, when said test body CP is made of a material with uni form mass density . In other words , during the preparation phase Pl the actuator means 16 are pos itioned relative to the supporting base 11 and the platform 15 in such a way that the impacting body CI wil l hit said test body CP in proximity to its centre of mass .

[0067] Along with the positioning of the accelerometer means 17 near the centre of mass of the test body CP, by having the collision of the impacting body CI occurring in proximity to the centre of mass of the test body CP it is advantageously possible to increase the validity of the relation expressed by formula ( 1 ) . This improves the detection of the time evolution o f an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body .

[0068] It is thus possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body .

[0069] Also with reference to Fig . 8 , the following will describe the constraining means 18a, 18b, 19a, 19b that constrain the platform 15 to the supporting base 11 . The apparatus 1 preferably comprises constraining means 18a, 18b, 19a, 19b, configured to vary a height and / or an inclination of said platform 15 relative to the supporting base 11 , so that said impacting body CI will start falling from di f ferent heights and / or will hit the test body CP at di f ferent points and with di f ferent orientations .

[0070] In more detail , the constraining means preferably comprise the following elements :

[0071] - a first support element 18a preferably consisting of a tee section preferably one to three metres long;

[0072] - a second support element 18b preferably consisting of a tee section preferably one to three metres long;

[0073] - a first tie rod 19a constraining the first support element 18a to a first portion of the platform 15 ; - a second tie rod 19b constraining the second support element 18b to a second portion of the platform 15 .

[0074] The first support element 18a and the second support element 18b are positioned side by side on the platform 15 in such a way that they extend along a direction which is perpendicular to the plane in which the supporting base 11 develops ; each one of them is preferably constrained to the platform 15 by means of a threaded bar and a nut , by welding, or otherwise .

[0075] The first tie rod 19a comprises the following parts :

[0076] - a first pin-type support 191a that constrains said first support element 18a to said first tie rod 19a;

[0077] - a first hinge 192a that constrains said first tie rod 19a to said platform 15 .

[0078] Furthermore , the second tie rod 19b comprises the following parts :

[0079] - a second pin-type support 191b that constrains said second support element 18b to said second tie rod 19b ;

[0080] - a second hinge 192b that constrains said second tie rod 19b to said platform 15 .

[0081] The platform 15 comprises also the following constraining elements :

[0082] - a third pin-type support 151a that constrains said first support element 18a to said platform 15 ;

[0083] - a fourth pin-type support 151b that constrains said second support element 18b to said platform 15 .

[0084] Each one of the support elements 18a, 18b comprises a series of holes to which the pin-type supports 191a, 191b, 151a, 151b can be coupled . In more detail , the first pin-type support 191a and the second pin-type support 191b are preferably coupled to holes which lie higher than those associated with the third pin-type support 151a and the fourth pin-type support 151b . In this way, the tie rods 19a, 19b will advantageously always remain above the platform 15, thus not interfering with the impacting body CI and posing no limits to the dimensions of said impacting body CI . By changing the holes to which the pin-type supports 191a, 191b, 151a, 151b are coupled, it is advantageously possible to adj ust the height from which the free fall of the impacting body CI will start .

[0085] Furthermore , the axes of rotation of said pin-type supports 191a, 191b, 151a, 151b are preferably all parallel to one another . Thus , the angle o f the platform 15 relative to the supporting base 11 can be adj usted by acting upon j ust one axis , i . e . by changing either the holes coupled to the pin-type supports 191 a, 191b o f the tie rods 19a, 19b or those coupled to the pintype supports 151a, 151b of the platform 15 , so as to vary the distance between the third pin-type support 151a and the first pin-type support 191a and between the fourth pin-type support 151b and the second pin-type support 191b . In combination with or as an alternative to moving the pin-type supports 191a, 191b, 151a, 151b, each one of the tie rods 19a, 19b i s preferably of the telescopic type , i . e . adj ustable in length ( e . g . after loosening a locking screw, after overcoming a force generated by a snap-type mechanism, or the like ) , allowing the pin-type supports 191a, 191b, 151a, 151b and the hinges 192a, 192b to rotate and change the angle of the platform 15 relative to the supporting base 11 about an axis without changing the holes associated with the pin-type supports 191a, 191b, 151a, 151b .

[0086] This makes it possible to carry out a plurality o f distinct impacts tests to detect , during each test , the time evolution of an impact force even in the presence of multiple impacts and / or f ragmentations / comminutions of both the impacting body and the test body . In this way, it is possible to study the contact force between the impacting body and the impacted body generated during impact phenomena that may involve fracture / fragmentation / comminution of the impacting body and / or of the impacted body .

[0087] Of course, the example described so far may be subj ect to many variations .

[0088] Some of the possible variants of the invention have been described above , but it will be clear to those skilled in the art that other embodiments may also be implemented in practice , wherein several elements may be replaced with other technically equivalent elements . The present invention is not , therefore , limited to the above-described illustrative examples , but may be subj ect to various modi fications , improvements , or replacements of equivalent parts and elements without however departing from the basic inventive idea, as speci fied in the following claims .

Claims

CLAIMS :

1. Apparatus (1) for detecting a time evolution of an impact force generated by a free-falling impacting body (CI) , comprising- a supporting base (11) for positioning a test body (CP) to be hit by said impacting body (CI) ,- sensor means (12,13,14) configured to detect a force generated by a mass of said test body (CP) and by an interaction between said test body (CP) and the impacting body (CI) , when said test body (CP) is positioned on said supporting base (11) and hit by said impacting body (CI) , and to generate a first signal on the basis of said force,- a platform (15) positioned above said supporting base (11) ,- actuator means (16) able to keep said impacting body (CI) constrained to said platform (15) , and configured to release said impacting body in free fall upon reception of a command signal , characterized in that it further comprises- accelerometer means (17) configured to detect an acceleration to which said test body (CP) is subjected after being hit by the impacting body (CI) , and to generate a second signal on the basis of said acceleration.

2. Apparatus (1) according to claim 1, comprising- acquisition means for acquiring said first signal and said second signal,- transmission means for transmitting an output signal,- computing means configured for• acquiring, via said acquisition means, the first signal and the second signal, and• computing at least one contact force between the impacting body (CI) and the test body (CP) on the basis of said firstsignal and said second signal.• transmitting, via said transmission means, the output signal in which said at least one contact force is encoded.

3. Apparatus (1) according to claim 1 or 2, wherein the sensor means comprise at least three load cells (12,13,14) so positioned as to support the test body (CP) at the same time.

4. Apparatus (1) according to any one of claims 1 to 3, wherein the accelerometer means (17) are configured to be positioned on the surface of said test body (CP) in proximity to the centre of mass of said test body (CP) .

5. Apparatus (1) according to any one of claims 1 to 4, wherein the accelerometer means comprise a piezoelectric accelerometer.

6. Apparatus (1) according to any one of claims 1 to 5, wherein the constraining means ( 18a, 18b, 19a, 19b) are configured to vary a height and / or an inclination of said platform (15) relative to the supporting base (11) .

7. Apparatus (1) according to any one of claims 1 to 6, wherein the actuator means (16) are configured to vary their own position relative to the supporting base (11) and the platform (15) .

8. Method of detecting a time evolution of an impact force generated by a free-falling impacting body (CI) , comprising- a preparation phase (Pl) , in which a test body (CP) is positioned on a supporting base, where said test body (CP) is to be hit by said impacting body (CI) , and in which said impacting body (CI) is constrained, by actuator means (16) , to a platform (15) positioned above said supporting base (11) ,- a release phase (P2) , in which the impacting body (CI) isreleased, by actuator means (16) , in free fall towards the supporting base (11) after said actuator means (16) have received a command signal,- a first generation phase (P3) , in which a first signal is generated, by sensor means (12,13,14) , on the basis of a force generated by a mass of said test body (CP) and by an interaction between said test body (CP) and the impacting body (CI) , when said test body is positioned on said supporting base (11) and hit by said impacting body (CI) , characterized in that it further comprises- a second generation phase (P4) , in which a second signal is generated, by accelerometer means (17) , on the basis of an acceleration to which said test body (CP) is subjected after being hit by the impacting body (CI) .

9. Method according to claim 8, further comprising- an acquisition phase, in which the first signal and the second signal are acquired by input means,- a computing phase, in which at least one contact force between the impacting body (CI) and the test body (CP) is computed, by computing means, on the basis of said first signal and said second signal, and- a transmission phase, in which an output signal, in which said at least one contact force is encoded, is transmitted by transmission means.

10. Method according to claims 8 or 9, wherein the sensor means comprise at least three load cells (12,13,14) so positioned as to support the test body (CP) at the same time, wherein each one of said at least three load cells (12,13,14) generates a load signal, and wherein, during the preparation phase (Pl) , the test body (CP) is positioned relative to the supporting base (11) according to said load signals, so that the force generatedby the mass of said test body (CP) will be distributed among said at least three load cells (12,13,14) .

11. Method according to any one of claims 8 to 10, wherein, during the preparation phase (Pl) , the accelerometer means (17) are positioned on the surface of said test body (CP) in proximity to the centre of mass of said test body (CP) .

12. Method according to any one of claims 8 to 11, wherein, during the preparation phase (Pl) , the actuator means (16) are positioned relative to the supporting base (11) and the platform (15) in such a way that the impacting body (CI) will hit said test body (CP) in proximity to its centre of mass.

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