Helmet center of gravity and moment of inertia testing device and method

Abstract

The invention discloses a device and method for testing the center of gravity and moment of inertia of a helmet, comprising a helmet fixing box, a V-shaped pad, a measuring stand, a cam mechanism, a base, first to third force sensors, a vibration frequency sensor and a host computer; the helmet fixing box is used for fixing and placing a helmet to be tested; the V-shaped pad is a pad with a 90-degree V-shaped groove; the measuring stand comprises a torsion pendulum stand, a bending fulcrum bearing and a butterfly plate; the bending fulcrum bearing is installed at the bottom of the torsion pendulum stand, the bending fulcrum bearing comprises a moving end and a static end, the moving end and the static end are connected by two pairs of cross-shaped spring sheets, the moving end is fixedly connected to the torsion pendulum stand, the static end is fixedly connected to the butterfly plate, and a locking piece is arranged between the static end and the torsion pendulum stand; the cam mechanism is arranged between the butterfly plate and the base; the first to third force sensors are arranged on the base in an equilateral triangle, the vibration frequency sensor is arranged on the static end, and the first to third force sensors and the vibration frequency sensor are all connected to the host computer.

Description

Technical Field

[0001] The invention relates to a device and a method for testing the centre of gravity and moment of inertia of a helmet, and belongs to the technical field of centre of gravity and moment of inertia testing. Background Art

[0002] Helmets are important protective equipment for the human head. They are widely used in military, medical, sports, entertainment and other industries. The center of gravity and moment of inertia of helmets have a great impact on the safety of use, especially for pilots and astronauts. This impact may even endanger the life safety. However, the helmet is a geometrically irregular body, and it is difficult to calculate its center of gravity and moment of inertia, so it needs to be measured and determined.

[0003] The ergonomic performance of helmets is an important factor affecting the performance of helmets, but it has not received due attention for a long time, especially the lack of objective testing and research methods. Among the studies on the ergonomic performance of military helmets conducted by various countries, the research conducted by the US military is the most comprehensive and in-depth. Jeffrey MT and others from the US Air Force Warfare Center used the KGR30 mass analyzer produced by Cosmic Electronics to test the center of gravity of the "head model-flight helmet" system, but the study did not directly measure the center of gravity of the irregular helmet body. Asko V. of the University of Melbourne, Australia, established a set of SPH-4 helmet dynamic performance evaluation equipment, but the equipment is relatively complicated and is greatly affected by the physiological factors of the helmet wearer. At present, there are few objective evaluation methods for helmet shape, helmet comfort and stability at home and abroad, and there is almost no overall quantitative test evaluation of fit. Domestic research on the ergonomic performance of helmets is also mainly concentrated in the field of aerospace, but there are still quite few research reports on objective evaluation methods. The Institute of Aviation Medicine has conducted experiments on the relationship between the weight of military helmets, wearing time and neck muscle fatigue. The neck muscle surface electromyography power spectrum was used to determine whether the neck muscles were fatigued, and the fatigue degree was evaluated in combination with subjective wearing sensations. The relationship between the weight of military helmets and the wearing time and neck muscle fatigue degree was obtained. During the development of the QGF02 helmet of our army, actual wearing experiments on the ergonomic performance of the helmet were organized, and fuzzy mathematics evaluation methods were used to evaluate factors such as the stability of helmet wearing and the ease of adjustment.

[0004] In summary, there are few studies on objective evaluation methods for helmet comfort and stability at home and abroad, and there is no special instrument to measure the inertial parameters, wearing comfort and stability of irregular helmets. Therefore, it is very necessary to develop a set of relevant testing equipment to conduct quantitative research and analysis on the comfort and stability of helmets. Accurately measuring the center of gravity and rotational inertia of helmets is even more important for evaluating, using and improving helmet design. Summary of the invention

[0005] The purpose of the present invention is to provide a helmet center of gravity and moment of inertia testing device and method with the characteristics of simple operation, convenient installation, high precision, etc., which can be applied to the testing of the center of gravity and moment of inertia of various helmets.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a helmet center of gravity and moment of inertia testing device, comprising a helmet fixing box, a V-shaped pad, a measuring stand, a cam mechanism, a base, first to third force sensors, a vibration frequency sensor and a host computer;

[0007] The helmet fixing box is used to fix the helmet to be tested;

[0008] The V-shaped pad is a pad with a 90-degree V-shaped groove, and the V-shaped pad is used to place a helmet fixing box or a helmet fixing box with a helmet to be tested;

[0009] The measuring stand comprises a torsion pendulum stand, a bending fulcrum bearing and a butterfly plate; the torsion pendulum stand is used to fix a helmet box during testing, and a first slide groove and a second slide groove intersecting vertically are formed at the center of the top surface of the torsion pendulum stand; the bending fulcrum bearing is installed at the bottom of the torsion pendulum stand, and the bending fulcrum bearing comprises a moving end and a static end with the same structure, and the moving end and the static end are centrally symmetrically distributed, and the moving end and the static end are connected by two pairs of cross-shaped spring sheets, and the moving end rotates relative to the static end around an axis formed by the intersection of the two pairs of cross-shaped spring sheets, the moving end is fixedly connected to the bottom of the torsion pendulum stand, and the static end is fixedly connected to the butterfly plate, and a locking member is arranged between the static end and the torsion pendulum stand, and the locking member is used to lock the torsion pendulum stand on the static end together with the moving end;

[0010] The cam mechanism is arranged between the butterfly plate and the base, and the cam mechanism is used to drive the measuring platform to move up and down relative to the base;

[0011] The first to third force sensors are located directly below the butterfly plate and are arranged on the base in an isosceles triangle; the first to third force sensors are used to collect the gravity of the helmet fixing box or the helmet fixing box containing the helmet to be tested during testing;

[0012] The vibration frequency sensor is arranged on the static end of the bending fulcrum bearing, and is used to collect the vibration frequency of the torsion pendulum stand;

[0013] The first to third force sensors and the vibration frequency sensor are all connected to the host computer.

[0014] In some embodiments, the cam mechanism includes a mounting seat, a cam, a push rod and a transmission shaft; the mounting seat is fixedly mounted on the base, the cam is rotatably arranged in the mounting seat through the transmission shaft, the transmission shaft is eccentrically passed through the cam, the push rod is vertically movably passed through the mounting seat, a top plate is fixedly arranged on the upper end of the push rod, the top plate is in contact with the butterfly plate, and the lower end of the push rod is in contact with the circumferential surface of the cam; one end of the transmission shaft extends out of the base.

[0015] In some embodiments, the locking member includes stop holes correspondingly opened on the torsion disc frame and the static end, and a stop member movably matched between the stop holes on the torsion and swinging frame and the static end;

[0016] Two limiting slide plates are arranged on both sides of the butterfly plate, the two limiting slide plates are fixed on the base, grooves are respectively provided on the edges of both sides of the butterfly plate, and the limiting slide plates are slidably matched in the grooves.

[0017] In some embodiments, the bending fulcrum bearing, butterfly plate, cam mechanism and base are all placed in a box, the torsion pendulum frame extends out of the top of the box, and an opening is provided on the side wall of the box, which is opposite to the end of the transmission shaft extending out of the base.

[0018] In some embodiments, the first, second and third force sensors are connected to the single-chip microcomputer via a multi-channel pressure transmitter circuit module, the vibration frequency sensor is connected to the single-chip microcomputer, the single-chip microcomputer is connected to the host computer, and a display panel is provided on the outside of the box, which is connected to the single-chip microcomputer and is used to display the gravity measured by the first to third force sensors and the vibration frequency of the torsion pendulum stand.

[0019] In some embodiments, the first to third force sensors all adopt BK-2S shear beam load sensors, the vibration frequency sensor adopts an optical pulse sensor, the optical pulsation sensor is arranged on the static end, and a baffle is arranged on the torsion pendulum stand; the butterfly plate is made of aluminum alloy; the helmet fixing box is made of plexiglass, and the helmet fixing box includes a box body and a box cover detachably arranged on the top of the box body.

[0020] In some embodiments, the torsion pendulum stand includes a circular disc made of aluminum alloy, the bottom surface of the circular disc is provided with spokes and rib structures, the center of the top surface of the circular disc has a first slide groove and a second slide groove that intersect vertically, a slider is slidably provided in the first slide groove and the second slide groove, a locking member is provided on the slider to lock it in the first slide groove or the second slide groove, and scales are attached to the edges of the first slide groove and the second slide groove.

[0021] In some embodiments, the host computer is integrated with a test parameter setting module, a serial port data receiving module, a data processing module, a data display module and a data storage module; the test parameter setting module is used to set the test parameters; the serial port data receiving module is used to receive the force values ​​collected by the first to third force sensors and the vibration frequencies collected by the vibration frequency sensor; the data processing module is used to receive and process the force values ​​and vibration frequency data to obtain the center of gravity and moment of inertia data of the helmet to be tested; the data display module is used to transmit and display the obtained data of the center of gravity and moment of inertia of the helmet to be tested on the interface of the host computer; the data storage module is used to store the center of gravity and moment of inertia data of the helmet to be tested and the corresponding test parameters.

[0022] In addition, the present invention also provides a method for testing the device in any of the above embodiments, comprising the following steps:

[0023] 1) Measure the position of the center of gravity of the helmet to be tested relative to itself H X , H Y , H Z The specific steps of measurement include:

[0024] S1) the measuring stand is lowered to the lowest position by a cam mechanism, the butterfly plate at the bottom of the measuring stand is pressed on the first to third force sensors, and the torsion pendulum stand is locked by a locking member, and the helmet center of gravity measurement mode is entered;

[0025] S2) taking the corner point shared by three adjacent and vertical faces on the helmet box as the coordinate origin and the three edges passing through the corner point as the xyz axes to form a fixed coordinate system, placing the helmet box on the oscillating stand in three steps, the first step taking the x-axis and y-axis on the helmet box parallel to the two slide grooves on the oscillating stand respectively, and aligning the center of the box surface where the xy axis is located with the center of the top surface of the oscillating stand; the second step taking the y-axis and x-axis on the helmet box parallel to the two slide grooves on the oscillating stand respectively, and aligning the center of the box surface where the yx axis is located with the center of the top surface of the oscillating stand; the third step taking the y-axis and z-axis on the helmet box parallel to the two slide grooves on the oscillating stand, and aligning the center of the box surface where the yz axis is located with the center of the top surface of the oscillating stand;

[0026] S3) respectively recording the readings F of the first force sensor when the helmet fixing box is placed on the torsion pendulum stand three times in step S2) x(盒) 、F y(盒) 、F z(盒) ; Taking the projection of the line connecting the second force sensor and the third force sensor as the fulcrum and the coordinate origin O', the position of the center of gravity of the fixed helmet box relative to the coordinate origin O' is calculated by the weighing method. The calculation formula is as follows:

[0027]

[0028] Among them, X 盒Indicates the position of the center of gravity of the helmet box in the x-axis direction; Y 盒 Indicates the position of the center of gravity of the helmet box in the y direction; Z 盒 Indicates the position of the center of gravity of the helmet box in the z direction; F x(盒) Indicates the first force sensor reading when the helmet box is placed for the first time; F y(盒) Indicates the reading of the first force sensor when the helmet box is placed for the second time; F z(盒) It indicates the reading of the first force sensor when the helmet box is placed for the third time; L indicates the distance between the force measuring point and the coordinate origin O'; G 盒 Indicates the weight of the helmet box;

[0029] S4) placing the helmet into a helmet fixing box, wherein the x-axis on the helmet fixing box is aligned with the H-axis on the helmet. X Parallel, the y-axis is parallel to the H on the helmet Y Parallel, z-axis and H on the helmet Z In parallel, place the helmet box with the helmet on the torsion pendulum stand, and the first to third force sensors measure the weight G 盔+盒 Then repeat steps S2) and S3) to record the force reading F at one end of the first force sensor when the helmet + helmet box is placed on the torsion pendulum stand three times. x(盔+盒) 、F y(盔+盒) 、F z(盔+盒) Then the position of the center of gravity of the helmet + fixed helmet box relative to the coordinate origin O' is calculated as follows:

[0030]

[0031] Among them, X 盔+盒 : The position of the center of gravity of the helmet + helmet box in the x direction; Y 盔+盒 : The position of the center of gravity of the helmet + helmet box in the y direction; Z 盔+盒 : The position of the center of gravity of the helmet + helmet box in the z direction; F x(盔+盒) : The first force sensor reading when the helmet + helmet box is placed for the first time; F y(盔+盒) : The first force sensor reading when the helmet + helmet fixing box is placed for the second time; F z(盔+盒) : The first force sensor reading when the helmet + helmet box is placed for the third time; G 盔+盒 : Weight of helmet + helmet box.

[0032] The position of the helmet's center of gravity relative to the coordinate origin O' is calculated as follows:

[0033]

[0034] Among them, X 盔 : The position of the helmet's center of gravity in the x direction; Y 盔 : The position of the helmet's center of gravity in the y direction; Z 盔 : The position of the helmet's center of gravity in the z direction; G盔 : Helmet weight G 盔 =G 盔+盒 -G 盒 .

[0035] S5) Measure the distance L between the front edge of the helmet, the left edge of the helmet and the top of the helmet from the coordinate origin O' 前 , L 左 , L 顶 ;

[0036] S6) Calculate the position H of the helmet's center of gravity relative to itself X , H Y , H Z .

[0037] The calculation formula is as follows:

[0038]

[0039] 2) Measure the moment of inertia of the helmet, including:

[0040] I) raising the measuring stand by means of a cam mechanism, so that the butterfly plate of the measuring stand is out of contact with the first to third force sensors, unlocking the locking member, and allowing the torsion pendulum stand to rotate freely;

[0041] II) The helmet fixing box is fixedly set on the oscillating stand three times. For the first time, the x-axis on the helmet fixing box is parallel to the rotation axis, the y-axis and the z-axis are parallel to the two slide grooves on the oscillating stand, and the center position of the box surface where the yz-axis is located is aligned with the center position of the top surface of the oscillating stand; for the second time, the y-axis on the helmet fixing box is parallel to the rotation axis, the center position of the box surface where the x-axis and the z-axis are located is parallel to the two slide grooves on the oscillating stand, and the center position of the box surface where the xz-axis is located is aligned with the center position of the top surface of the oscillating stand; for the third time, the z-axis on the helmet fixing box is parallel to the rotation axis, the center position of the box surface where the x-axis and the y-axis are located is parallel to the two slide grooves on the oscillating stand, and the center position of the box surface where the xy-axis is located is aligned with the center position of the top surface of the oscillating stand; each time, an initial angular displacement is given to the oscillating stand so that the oscillating stand performs torsional free vibration;

[0042] III) respectively record the vibration frequencies of the torsion pendulum frame collected three times by the vibration frequency sensor in step II), obtain the periods of the torsion pendulum frame's three torsional free vibrations according to the relationship between frequency and period, and calculate the moment of inertia J according to the moment of inertia measurement formula x , J y , J z ;

[0043] Where, K: torsional stiffness, fixed value is 4.57N·m / deg; J x J is the moment of inertia of the fixed helmet box with the x-axis parallel to the rotation axis and the torsional vibration of the torsion pendulum stand; yis the moment of inertia of the fixed helmet box with the y-axis parallel to the rotation axis and the torsional vibration of the torsion pendulum stand; J z is the moment of inertia of the fixed helmet box with the z-axis parallel to the rotation axis and the torsional vibration of the torsion pendulum stand; T x(盒) is the period of torsional vibration of the fixed helmet box with the x-axis parallel to the rotation axis along the torsional pendulum stand; T y(盒) is the period of torsional vibration of the fixed helmet box with the y-axis parallel to the rotation axis along the torsional pendulum stand; T z(盒) is the period of torsional vibration of the fixed helmet box with the z-axis parallel to the rotation axis along the torsion pendulum stand;

[0044] IV) Put the helmet into the helmet box, repeat II) to III), and calculate J x `、J y `、J z `;

[0045]

[0046] In the formula, J x ` is the moment of inertia of the helmet box with the helmet placed therein, which vibrates with the torsion pendulum stand with the x-axis parallel to the rotation axis; J y ` is the moment of inertia of the torsion vibration of the torsion pendulum stand with the y-axis parallel to the rotation axis of the helmet box; J z ` is the moment of inertia of the helmet box with the helmet placed therein, which vibrates with the torsion pendulum stand with the z-axis parallel to the rotation axis; T x(盔+盒) T is the period of torsional vibration of the helmet box with the helmet placed on it with the x-axis parallel to the rotation axis; y(盔+盒) T is the period of torsional vibration of the helmet box with the helmet placed on it with the y-axis parallel to the rotation axis; z(盔+盒) The period of torsional vibration of the helmet box with the helmet placed therein with the torsional pendulum stand with the z-axis parallel to the rotation axis;

[0047] V) Based on the additivity of moments of inertia, find the moment of inertia of the helmet relative to the center of rotation;

[0048] The calculation formula is as follows:

[0049]

[0050] VI) Determine the moment of inertia of the helmet relative to its center of gravity;

[0051] The calculation formula of the distance between the center of gravity and the center of rotation is as follows:

[0052]

[0053] Among them, X 盔 : The position of the helmet's center of gravity in the x direction; Y 盔 : The position of the helmet's center of gravity in the y direction; Z 盔: The position of the helmet's center of gravity in the z direction; d x : The distance between the rotation center and the coordinate origin O' in the x-axis direction; d y : The distance between the rotation center and the coordinate origin O' in the y-axis direction; d z : The distance between the rotation center and the coordinate origin O' in the z-axis direction; L: The distance between the force measuring point and the coordinate origin O';

[0054] According to the theorem of parallel axis displacement of moment of inertia, the formula of the moment of inertia of the helmet around its own center of gravity is as follows:

[0055]

[0056] Right now:

[0057]

[0058] In the formula, J x ``: The moment of inertia of the helmet around its own center of gravity in the x direction; J y ``: The moment of inertia of the helmet around its own center of gravity in the y direction; J z ``: The moment of inertia of the helmet around its own center of gravity in the z direction; m is the mass of the helmet.

[0059] In some embodiments, step III) further includes: placing a helmet fixing box on a V-block, adjusting the fixed position of the V-block on the torsion pendulum frame, respectively raising the planes where the x and y axes, the planes where the y and z axes, and the planes where the z and x axes are located on the helmet fixing box, and aligning them with the rotation axis; giving the torsion pendulum frame an initial angular displacement each time so that the torsion pendulum frame performs torsional free vibration; respectively recording the vibration frequency of the torsion pendulum frame collected by the vibration frequency sensor three times, obtaining the periods of the torsion free vibration of the torsion pendulum frame three times, and then calculating the moment of inertia J xy , J yz , J zx ;

[0060]

[0061] In the formula, J xy J is the moment of inertia of the fixed helmet box when the plane where the xy axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; yz is the moment of inertia of the fixed helmet box when the plane where the yz axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; J zx is the moment of inertia of the fixed helmet box with the torsional vibration of the torsion pendulum stand when the plane where the zx axis is located coincides with the rotation axis; T xy(盒) is the period of torsional vibration of the fixed helmet box with the plane where the xy axis is located coincident with the rotation axis; T yz(盒) is the period of torsional vibration of the fixed helmet box with the plane where the yz axis is coincident with the rotation axis; T zx(盒)is the period of torsional vibration of the fixed helmet box with the plane where the zx axis is located coincident with the rotation axis;

[0062] Step IV) also includes placing a helmet fixing box with a helmet on a V-block, adjusting the fixed position of the V-block on the torsion pendulum frame, respectively standing up the planes where the x and y axes, the planes where the y and z axes, and the planes where the z and x axes are located on the helmet fixing box with the helmet, and aligning them with the rotation axis; giving the torsion pendulum frame an initial angular displacement each time so that the torsion pendulum frame performs torsional free vibration; respectively recording the vibration frequency of the torsion pendulum frame collected by the vibration frequency sensor three times, obtaining the periods of the torsion free vibration of the torsion pendulum frame three times, and then calculating the moment of inertia J xy `、J yz `、J zx `

[0063]

[0064] J xy ` is the moment of inertia of the helmet box with the helmet placed on it when the plane where the xy axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; J yz ` is the moment of inertia of the helmet box with the helmet placed on it when the plane where the yz axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; J zx ` is the moment of inertia of the helmet box with the helmet placed on it, when the plane where the zx axis is located coincides with the rotation axis, and when the torsion pendulum frame torsional vibrates; T xy(盔+盒) is the period of torsional vibration of the torsion pendulum stand when the plane where the xy axis of the helmet box is placed coincides with the rotation axis; T yz(盔+盒) is the period of torsional vibration of the torsion pendulum stand when the plane where the yz axis of the helmet box is placed coincides with the rotation axis; T zx(盔+盒) It is the period of torsional vibration of the torsion pendulum stand when the plane where the zx axis of the helmet box is placed coincides with the rotation axis.

[0065] The present invention adopts the above technical scheme, which has the following advantages: the helmet center of gravity and moment of inertia testing device provided by the present invention utilizes a cam mechanism to drive a measuring stand to perform lifting motion, so that the testing device switches between helmet center of gravity measurement and moment of inertia measurement states; the first to third force sensors distributed on the butterfly plate collect the gravity of a helmet fixing box or a helmet fixing box with a helmet to be tested during testing; the vibration frequency sensor collects the vibration frequency of a torsion pendulum stand, and then calculates the center of gravity position and moment of inertia of the helmet to be tested; the entire testing device has the characteristics of simple operation, convenient installation, high precision, etc., and can be applied to the testing of various helmet center of gravity and moment of inertia, which is of great significance for evaluating, using and improving the design of helmets. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0067] Figure 2 It is a structural schematic diagram of a V-shaped pad for placing a helmet fixing box according to the present invention;

[0068] Figure 3 It is a structural schematic diagram of the torsion pendulum stand of the present invention;

[0069] Figure 4 It is a schematic diagram of the bending fulcrum bearing structure of the present invention;

[0070] Figure 5 yes Figure 4 AA structural diagram;

[0071] Figure 6 It is a schematic diagram of the butterfly plate structure of the present invention;

[0072] Figure 7 It is a structural schematic diagram of the cam mechanism of the present invention;

[0073] Figure 8 It is the principle diagram of the cam mechanism of the present invention;

[0074] Fig. 9 It is a flowchart of connecting the first to third force sensors and the vibration frequency sensor of the present invention with a host computer;

[0075] Fig.10 It is a definition diagram of the helmet coordinate system of the present invention.

[0076] Fig.11 is a top view layout diagram of the first, second and third force sensors of the present invention;

[0077] Fig.12 This is a schematic diagram of the center of gravity measurement principle of the helmet of the present invention;

[0078] Fig.13 It is a schematic diagram of a fixed coordinate system on the helmet fixing box of the present invention;

[0079] Fig.14 1 is a schematic diagram of placing a helmet fixing box containing a helmet when measuring the moment of inertia of the present invention. Fig.14 a is a schematic diagram showing that the x-axis of the helmet box is parallel to the rotation axis, and the y-axis and z-axis are parallel to the two slides on the torsion pendulum stand; Fig.14 b is a schematic diagram showing that the y-axis of the helmet-fixing box is parallel to the rotation axis, and the center of the box surface where the x-axis and z-axis are located is parallel to the two slide slots on the torsion pendulum stand; Fig.14 c is a schematic diagram showing that the z-axis on the fixed helmet box is parallel to the rotation axis, and the center of the box surface where the x-axis and y-axis are located is parallel to the two slide slots on the torsion pendulum stand; Fig.14 d is a schematic diagram when the plane where the x and y axes on the fixed helmet box are located coincides with the rotation axis; Fig.14 e is a schematic diagram when the plane where the y and z axes on the fixed helmet box are located coincides with the rotation axis; Fig.14f is a schematic diagram when the plane where the z and x axes on the fixed helmet box are located coincides with the rotation axis. DETAILED DESCRIPTION

[0080] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0081] like Figures 1 to 6 As shown, a helmet center of gravity and moment of inertia testing device provided by the present invention comprises a helmet fixing box 1, a V-shaped pad 2, a measuring stand, a cam mechanism 6, a base 7, first to third force sensors, a vibration frequency sensor and a host computer; the helmet fixing box 1 is used to fix the helmet to be tested; the V-shaped pad 2 is a pad with a 90-degree V-shaped groove, and the V-shaped pad 2 is used to place the helmet fixing box 1 or the helmet fixing box 1 with the helmet to be tested; the measuring stand comprises a torsion pendulum stand 3, a bending fulcrum bearing 4 and a butterfly plate 5; the torsion pendulum stand 3 is used to fix the helmet fixing box 2 during testing, and a first slide groove and a second slide groove intersecting vertically are formed at the center of the top surface of the torsion pendulum stand 3; the bending fulcrum bearing 4 is installed at the bottom of the torsion pendulum stand 3, and the bending fulcrum bearing 4 comprises a moving end 41 and a static end 42 with the same structure, and the moving end 41 and the static end 42 are centrally symmetrically distributed, and the moving end 41 and the static end 42 are separated by two pairs of cross-shaped bearings. The moving end 41 rotates relative to the static end 42 around the axis formed by the intersection of the spring sheet 43, the moving end 41 is fixedly connected to the bottom of the torsion pendulum frame 3, the static end 42 is fixedly connected to the butterfly plate 5, and a locking piece is arranged between the static end 42 and the torsion pendulum frame 3, and the locking piece is used to lock the torsion pendulum frame 3 on the static end 42 together with the moving end 41; the cam mechanism 6 is arranged between the butterfly plate 5 and the base 7, and the cam mechanism 6 is used to drive the measuring stand to move up and down relative to the base 7; the first to third force sensors are located directly below the butterfly plate 5 and are arranged on the base 7 in an isosceles triangle, and are used to collect the gravity of the helmet fixing box 1 or the helmet fixing box 1 with the helmet to be tested during testing, and the vibration frequency sensor is arranged on the static end 42 of the bending fulcrum bearing 4, and is used to collect the vibration frequency of the torsion pendulum frame 3; the first to third force sensors and the vibration frequency sensor are all connected to the host computer.

[0082] In the above embodiment, preferably, Figure 7 , Figure 8As shown, the cam mechanism 6 includes a mounting seat 61, a cam 62, a push rod 63 and a transmission shaft 64; the mounting seat 61 is fixedly mounted on the base 7, the cam 62 is rotatably arranged in the mounting seat 61 through the transmission shaft 64, the transmission shaft 64 is eccentrically penetrated on the cam 62, the push rod 63 is vertically movably penetrated on the mounting seat 61, the upper end of the push rod 63 is in contact with the butterfly plate 5, and the lower end of the push rod 63 is in contact with the circumferential surface of the cam 62; one end of the transmission shaft 64 extends out of the base 7.

[0083] In the above embodiment, preferably, the cam mechanism further includes a top plate 65 , which is fixed to the upper end of the top rod 63 , and the top plate 65 is in contact with the butterfly plate 5 .

[0084] In the above embodiment, preferably, the locking member includes stop holes correspondingly opened on the torsion disk frame 3 and the static end 42, and a stop member (such as a pin) movably engaged between the stop holes on the torsion pendulum frame 3 and the static end 42, thereby preventing the torsion pendulum frame 3 from rotating when the center of gravity measurement is performed.

[0085] In the above embodiment, preferably, Figure 6 As shown, two limit slides 8 are arranged on both sides of the butterfly plate 5, and the two limit slides 8 are fixed on the base 7. Grooves are respectively provided on the edges of both sides of the butterfly plate 5, and the limit slides 8 are slidably fitted in the grooves; when the height of the torsion pendulum stand 3 is raised or lowered by the cam adjustment mechanism, the butterfly plate 5 moves up and down along the limit slides 8, limiting the measuring stand to only move up and down, ensuring that the rotation center of the measuring stand remains unchanged, and improving the measurement accuracy of the test device.

[0086] In the above embodiment, preferably, the bending fulcrum bearing 4, the butterfly plate 5, the cam mechanism 6 and the base 7 are all placed in the box, the torsion pendulum frame 3 extends out of the top of the box, and the side wall of the box is provided with an opening, which is directly opposite to the end of the transmission shaft 64 extending out of the base 7. When in use, the hexagonal wrench can be inserted into the box through the opening and cooperate with the transmission shaft 64. The tester drives the transmission shaft 64 to rotate through the wrench outside the box, and the transmission shaft 64 drives the cam 62 to rotate, and the cam 63 pushes the top rod to move up and down, thereby realizing the up and down movement of the torsion pendulum frame 3, and realizing the conversion of the measurement of the center of gravity and the moment of inertia of the helmet.

[0087] In the above embodiment, preferably, Fig. 9As shown, the first, second and third force sensors are connected to the single-chip microcomputer through a multi-channel pressure transmitter circuit module, the vibration frequency sensor is connected to the single-chip microcomputer, and the single-chip microcomputer is connected to the host computer. The single-chip microcomputer processes the data transmitted by the first to third force sensors and the vibration frequency sensor, obtains the force values ​​collected by the first to third force sensors and the vibration period of the torsion pendulum stand, and transmits them to the host computer; a display panel is arranged on the outside of the box, the display panel is connected to the single-chip microcomputer, and the display panel is used to display the gravity measured by the first to third force sensors and the vibration frequency of the torsion pendulum stand 3.

[0088] In the above embodiment, preferably, the first to third force sensors are all BK-2S shear beam load sensors, the vibration frequency sensor is an optical pulse sensor, the optical pulsation sensor is arranged on the static end portion 42, and a baffle is arranged on the torsion pendulum stand 3. When torsional vibration occurs, the baffle moves back and forth between the transmitting and receiving ends of the optical pulse sensor. The sensor measurement frequency is the vibration frequency of the torsion pendulum stand multiplied by the number of baffles. In this way, the vibration frequency of the torsion pendulum stand 3 can be obtained, and then the vibration period of the torsion pendulum stand 3 can be calculated; the single-chip microcomputer adopts the PIC18F25K22 single-chip microcomputer, and the single-chip microcomputer is connected to the host computer via the RS485 bus.

[0089] In the above embodiment, preferably, Figure 3 As shown, the torsion pendulum stand 3 includes a disk made of aluminum alloy, the bottom surface of the disk is provided with spokes and rib structure, the center of the top surface of the disk is provided with a first slide groove and a second slide groove intersecting vertically, a slider is slidably provided in the first slide groove and the second slide groove, a locking member is provided on the slider to lock it in the first slide groove or the second slide groove, and a scale is attached to the edge of the first slide groove and the second slide groove. When in use, the slider can be used to fix the helmet fixing box 1 or the helmet fixing box 1 with the helmet to be tested on the torsion pendulum stand 3, and at the same time, the position of the helmet fixing box 2 on the torsion pendulum stand 3 can be read by the scale.

[0090] In the above embodiment, preferably, the butterfly plate 5 is made of aluminum alloy.

[0091] In the above embodiment, preferably, the helmet fixing box 1 is made of organic glass, and comprises a box body and a box cover detachably arranged on the top of the box body.

[0092] In the above embodiment, preferably, a test parameter setting module, a serial port data receiving module, a data processing module, a data display module and a data storage module are integrated in the host computer; the test parameter setting module is used to set test parameters, such as torsional stiffness K, helmet parameters (model and quality, etc.), and helmet fixing box parameters (model and quality, etc.); the serial port data receiving module is used to receive the force values ​​F1, F2 and F3 collected by the first to third force sensors and the vibration frequency collected by the vibration frequency sensor, and the data processing module is used to receive and process the force values ​​F1, F2, F3 and the vibration frequency data to obtain the center of gravity and moment of inertia data of the helmet to be tested; the data display module is used to transmit and display the obtained data of the center of gravity and moment of inertia of the helmet to be tested on the interface of the host computer; the data storage module is used to store the center of gravity and moment of inertia data of the helmet to be tested and the corresponding test parameters.

[0093] Based on the above-mentioned helmet center of gravity and moment of inertia testing device, the present invention also provides a helmet center of gravity and moment of inertia testing method, which comprises the following steps:

[0094] 1) Measure the position H of the center of gravity C of the helmet to be tested relative to itself X , H Y , H Z The measurement of Fig.10 As shown, H X H is the distance from the center of gravity C to the left edge of the helmet, Y H is the distance from the center of gravity C to the front edge of the helmet; Z is the distance from the center of gravity C to the top of the helmet.

[0095] The weighing method is used to measure the center of gravity of irregular objects such as helmets. The weighing method is a method based on the principle of levers, such as Fig.11 , Fig.12 As shown, the projection of the line connecting the second force sensor and the third force sensor is selected as the fulcrum and the coordinate origin O', then the weight of the object and the supporting force of the first force sensor are equivalent to the lever force. As long as the force reading F of the object under test at one end of the force sensor is known, the center of gravity position Gx of the object under test in the x direction can be calculated using the following formula.

[0096]

[0097] Where: G is the weight of the object to be measured, G=F1+F2+F3; F is the reading of the first force sensor, F=F1; L is the distance between the force measuring point and the coordinate origin O', L=L1+L2.

[0098] Rotate the object horizontally 90 degrees to find the center of gravity Gy of the object in the y direction, and then rotate the object vertically 90 degrees to find the center of gravity Gz of the object in the z direction. Then the relative position of the object to be measured can be determined. Fig.12The center of gravity of the coordinate origin O' in the image is actually the position of the center of gravity relative to itself. To this end, the helmet to be tested is fixed in a lightweight box (helmet box) that can ensure that there are three mutually perpendicular surfaces, with the three edges passing through the corner point as the xyz axis, such as Fig.13 The role of the helmet fixing box is not only to make the stable measurement of the military helmet possible, but also to obtain the position of the center of gravity of the military helmet relative to its own reference surface by taking the surface of the helmet box as the reference positioning surface.

[0099] In actual measurement, the center of gravity position of the helmet with and without a helmet needs to be measured separately, that is, the center of gravity position of the helmet fixing box itself is measured first, and then by calculation, after deducting the influence of the helmet fixing box, the center of gravity position of the helmet relative to itself can be obtained (such as Fig.10 shown).

[0100] Therefore, the position of the helmet's center of gravity relative to itself is H X , H Y , H Z The specific steps of the measurement include:

[0101] S1) the measuring stand is lowered to the lowest position by the cam mechanism 6, the butterfly plate 5 at the bottom of the measuring stand is ensured to press on the first to third force sensors, and the torsion pendulum stand 3 is locked by the locking member, and the helmet center of gravity measurement mode is entered;

[0102] S2) Take the corner point shared by three adjacent and vertical surfaces on the fixed helmet box 1 as the coordinate origin, and take the three edges passing through the corner point as the xyz axis to form a fixed coordinate system (such as Fig.13 As shown in the figure, the helmet box 1 is placed on the oscillating stand 3 three times. The first time, the x-axis and y-axis on the helmet box 1 are parallel to the two slide grooves on the oscillating stand 3 respectively, and the center position of the box surface where the xy axis is located is aligned with the center of the top surface of the oscillating stand 3; the second time, the y-axis and x-axis on the helmet box 1 are parallel to the two slide grooves on the oscillating stand 3 respectively, and the center position of the box surface where the yx axis is located is aligned with the center of the top surface of the oscillating stand; the third time, the y-axis and z-axis on the helmet box 1 are parallel to the two slide grooves on the oscillating stand 3, and the center position of the box surface where the yz axis is located is aligned with the center of the top surface of the oscillating stand.

[0103] S3) respectively recording the readings F of the first force sensor when the helmet fixing box 1 is placed on the torsion pendulum stand 3 in step S2) three times x(盒) 、F y(盒) 、F z(盒) ; The relative coordinate system of the center of gravity of the helmet box 1 ( Fig.12 The coordinate origin O') position in the calculation formula is as follows:

[0104]

[0105] Among them, X 盒Indicates the position of the center of gravity of the helmet fixing box 1 in the x-axis direction; Y 盒 Z represents the position of the center of gravity of the helmet fixing box 1 in the y direction; 盒 Indicates the position of the center of gravity of the helmet fixing box 1 in the z direction; F x(盒) Indicates the first force sensor reading when the helmet fixing box 1 is placed for the first time; F y(盒) Indicates the reading of the first force sensor when the helmet fixing box 1 is placed for the second time; F z(盒) It indicates the reading of the first force sensor when the helmet box is placed for the third time; L indicates the distance between the force measuring point and the coordinate origin O' (fixed value 25cm); G 盒 Indicates the weight of the helmet box (fixed value 0.955kg).

[0106] S4) placing the helmet into the helmet fixing box 1, wherein the x-axis on the helmet fixing box 1 is aligned with the H-axis on the helmet. X Parallel, the y-axis is parallel to the H on the helmet Y Parallel, z-axis and H on the helmet Z In parallel, the helmet box 1 containing the helmet is placed on the torsion pendulum stand 3, and the first to third force sensors measure the weight G 盔+盒 Then repeat steps S2) and S3) to record the force reading F at one end of the first force sensor when the helmet + helmet box is placed on the torsion pendulum stand 3 three times. x(盔+盒) 、F y(盔+盒) 、F z(盔+盒) ,

[0107] Helmet + helmet box center of gravity relative coordinate system ( Fig.12 The position of the coordinate origin O' in the calculation formula is as follows:

[0108]

[0109] Among them, X 盔+盒 : The position of the center of gravity of the helmet + helmet box in the x direction; Y 盔+盒 : The position of the center of gravity of the helmet + helmet box in the y direction; Z 盔+盒 : The position of the center of gravity of the helmet + helmet box in the z direction; F x(盔+盒) : The first force sensor reading when the helmet + helmet box is placed for the first time; F y(盔+盒) : The first force sensor reading when the helmet + helmet fixing box is placed for the second time; F z(盔+盒) : The first force sensor reading when the helmet + helmet box is placed for the third time; G 盔+盒 : Weight of helmet + helmet box.

[0110] Helmet center of gravity relative coordinate system ( Fig.12 The position of the coordinate origin O' in the calculation formula is as follows:

[0111]

[0112] Among them, X 盔 : The position of the helmet's center of gravity in the x direction; Y 盔 : The position of the helmet's center of gravity in the y direction; Z 盔 : The position of the helmet's center of gravity in the z direction; G 盔 : Helmet weight G 盔 =G 盔+盒 -G 盒 .

[0113] S5) Measure the distance between the front edge of the helmet, the left edge of the helmet and the top of the helmet from the coordinate system ( Fig.12 The distance L from the origin of the coordinates O') 前 , L 左 , L 顶 ;

[0114] S6) Calculate the position H of the helmet's center of gravity relative to itself X , H Y , H Z .

[0115] The calculation formula is as follows:

[0116]

[0117] Where: H X : The distance between the center of gravity of the helmet and the left edge of the helmet; H Y : The distance between the center of gravity of the helmet and the front edge of the helmet; H Z : The distance between the center of gravity of the helmet and the top of the helmet; L 前 : The distance from the front edge of the helmet to the coordinate origin O'; L 左 : The distance from the left edge of the helmet to the coordinate origin O'; L 顶 : The distance from the top of the helmet to the coordinate origin O'; G 盔 : The weight of the helmet.

[0118] 2) Measure the moment of inertia of the helmet,

[0119] For the measurement of the moment of inertia of irregular shaped objects such as helmets, this device uses the torsion pendulum method. The measurement principle diagram is as follows: Figure 2 As shown. Its principle is based on the isochronism of free torsional vibration. By measuring the frequency (or period) of the free torsional vibration of an object, the purpose of measuring the moment of inertia of the object is achieved.

[0120] The object to be measured is placed on a disk that is subjected to torsional vibration around a fixed axis. The disk is constrained by a torsion spring with a stiffness of K. Given an initial angular displacement, the disk is subjected to torsional free vibration, and the moment of inertia of the system around the center of rotation is:

[0121]

[0122] Where J is the moment of inertia of the system around the center of rotation, T is the natural period of torsional vibration; K is the torsional stiffness, that is, the torsional stiffness of the torsion spring, and its value is 4.75.

[0123] Therefore, the measurement process of the helmet's moment of inertia specifically includes:

[0124] I) raising the measuring stand by means of the cam mechanism 6, so that the butterfly plate 5 of the measuring stand is out of contact with the first to third force sensors, unlocking the locking member, and allowing the torsion pendulum stand 3 to rotate freely;

[0125] II) The helmet fixing box 1 is fixed on the torsion pendulum stand three times. The first time, Fig.14 As shown in a, the x-axis on the helmet fixing box 1 is parallel to the rotation axis, the y-axis and the z-axis are parallel to the two slide slots on the torsion pendulum frame 3, and the center position of the box surface where the yz-axis is located is aligned with the center position of the top surface of the torsion pendulum frame 3; the second time, as shown in Fig.14 As shown in b, the y-axis on the helmet fixing box 1 is parallel to the rotation axis, the center position of the box surface where the x and z axes are located is parallel to the two slide grooves on the torsion pendulum stand 3, and the center position of the box surface where the x and z axes are located is aligned with the center position of the top surface of the torsion pendulum stand 3; the third time, as shown in Fig.14 As shown in c, the z-axis on the helmet fixing box 1 is parallel to the rotation axis, the center position of the box surface where the x and y axes are located is parallel to the two slide grooves on the torsion pendulum frame 3, and the center position of the box surface where the xy axes are located is aligned with the center position of the top surface of the torsion pendulum frame 3; each time the torsion pendulum frame 3 is given an initial angular displacement, the torsion pendulum frame 3 is made to perform torsional free vibration;

[0126] III) respectively record the vibration frequencies of the torsion pendulum frame 3 collected three times by the vibration frequency sensor in step II), obtain the periods of the three torsional free vibrations of the torsion pendulum frame 3 according to the relationship between frequency and period, and calculate the moment of inertia J according to the moment of inertia measurement formula x , J y , J z ;

[0127]

[0128] In the formula, J x J is the moment of inertia of the helmet box 1 when the torsion vibration of the torsion pendulum stand 3 is parallel to the x-axis and the rotation axis; y J is the moment of inertia of the helmet box 1 when the torsion vibration of the torsion pendulum stand 3 is parallel to the y-axis and the rotation axis; z T is the moment of inertia of the helmet box 1 with the z axis parallel to the rotation axis and the torsion pendulum stand 3 torsional vibration; x(盒) T is the period of torsional vibration of the fixed helmet box 1 with the x-axis parallel to the rotation axis and the torsion pendulum stand 3; y(盒) T is the period of torsional vibration of the fixed helmet box 1 with the y-axis parallel to the rotation axis and the torsion pendulum stand 3; z(盒)It is the period of torsional vibration of the helmet box 1 with the z-axis parallel to the rotation axis and the torsion pendulum stand 3.

[0129] IV) Place the helmet fixing box 1 on the V-block 2, adjust the fixed position of the V-block 2 on the torsion pendulum stand 3, and respectively stand up the plane where the x-axis and y-axis, the plane where the y-axis and z-axis, and the plane where the z-axis and x-axis are located on the helmet fixing box 1, and make them coincide with the rotation axis (such as Fig.14 d-14f); each time the torsion pendulum frame 3 is given an initial angular displacement, the torsion pendulum frame 3 is subjected to torsional free vibration; the vibration frequency sensor is used to collect the vibration frequency of the torsion pendulum frame 3 three times, and the periods of the torsional free vibration of the torsion pendulum frame 3 are obtained, and then the moment of inertia J is calculated. xy , J yz , J zx ;

[0130]

[0131] In the formula, J xy J is the moment of inertia of the helmet box 1 when the plane where the xy axis is located coincides with the rotation axis and the torsion pendulum stand 3 torsional vibration; yz J is the moment of inertia of the helmet box 1 when the plane where the yz axis is located coincides with the rotation axis and the torsion vibration of the torsion pendulum stand 3; zx is the moment of inertia of the helmet box 1 when the plane where the zx axis is located coincides with the rotation axis and the torsion pendulum stand 3 torsional vibration; T xy(盒) T is the period of torsional vibration of the fixed helmet box 1 with the plane where the xy axis is located coincident with the rotation axis; yz(盒) is the period of torsional vibration of the fixed helmet box 1 with the plane where the yz axis is coincident with the rotation axis along with the torsional pendulum stand 3; T zx(盒) is the period of torsional vibration of the torsion pendulum stand 3 when the plane where the zx axis is located coincides with the rotation axis.

[0132] V) Put the helmet into the helmet fixing box 1, repeat II to IV, and calculate J x `、J y `、J z `、J xy `、J yz `、J zx `;

[0133]

[0134]

[0135] In the formula, J x ` is the moment of inertia of the helmet box 1 with the helmet placed therein, which vibrates with the torsion swing stand 3 with the x-axis parallel to the rotation axis; J y` is the moment of inertia of the torsion vibration of the torsion pendulum stand 3 with the y-axis parallel to the rotation axis when the helmet fixing box 1 is placed therein; J z ` is the moment of inertia of the helmet box 1 with the helmet placed therein, which vibrates with the torsion swing stand 3 with the z axis parallel to the rotation axis; T x(盔+盒) T is the period of torsion vibration of the helmet box 1 with the helmet placed therein with the torsion pendulum stand 3 with the x-axis parallel to the rotation axis; y(盔+盒) T is the period of torsion vibration of the helmet box 1 with the helmet placed therein with the torsion pendulum stand 3 with the y-axis parallel to the rotation axis; z(盔+盒) The period of the torsional vibration of the helmet box 1 with the helmet placed therein with the torsional pendulum stand 3 with the z axis parallel to the rotation axis. xy ` is the moment of inertia of the helmet box with the helmet placed therein, which vibrates with the torsion pendulum stand 3 with the plane where the xy axis is located coinciding with the rotation axis; J yz ` is the moment of inertia of the helmet box 1 with the helmet placed therein, which vibrates with the torsion swing stand 3 with the plane where the yz axis is located coinciding with the rotation axis; J zx ` is the moment of inertia of the helmet box 1 with the helmet placed therein, which vibrates with the torsion pendulum stand 3 with the plane where the zx axis is located coinciding with the rotation axis; T xy(盔+盒) T is the period of torsional vibration of the helmet box 1 with the helmet placed therein with the torsional pendulum stand 3 when the plane where the xy axis is located coincides with the rotation axis; yz(盔+盒) T is the period of torsional vibration of the helmet box 1 with the helmet placed therein with the torsional pendulum stand 3 when the plane where the yz axis is located coincides with the rotation axis; zx(盔+盒) It is the period of torsional vibration of the torsion pendulum stand 3 when the helmet box 1 with the helmet is placed therein and the plane where the zx axis is located coincides with the rotation axis.

[0136] VI) Based on the additivity of the moment of inertia, the moment of inertia of the helmet relative to the center of rotation (i.e., the center of rotation) is calculated; the calculation formula is as follows:

[0137]

[0138] VII) Find the moment of inertia of the helmet with respect to its center of gravity.

[0139] The calculation formula of the distance between the center of gravity and the center of rotation is as follows:

[0140]

[0141] Among them, X 盔 : The position of the helmet's center of gravity in the x direction; Y 盔 : The position of the helmet's center of gravity in the y direction; Z 盔 : The position of the helmet's center of gravity in the z direction; d x : The distance between the rotation center and the coordinate origin O' in the x-axis direction; d y : The distance between the rotation center and the coordinate origin O' in the y-axis direction; d z: The distance between the rotation center and the coordinate origin O' in the z-axis direction; L: The distance between the force measuring point and the coordinate origin O' (fixed value 25cm);

[0142] According to the parallel axis theorem of moment of inertia: J′=J-md 2

[0143] Where: J′: the moment of inertia of the measured object around its own center of gravity; J: the moment of inertia of the measured object around the center of rotation; m: the mass of the measured object; d: the distance between the measured object's own center of gravity and the center of rotation.

[0144] The formula for the moment of inertia of the helmet around its own center of gravity is as follows:

[0145]

[0146] Right now:

[0147]

[0148] Where, K: torsional stiffness, fixed value is 4.57N·m / deg; J x ``: The moment of inertia of the helmet around its own center of gravity in the x direction; J y ``: The moment of inertia of the helmet around its own center of gravity in the y direction; J z ``: The moment of inertia of the helmet around its own center of gravity in the z direction; m is the mass of the helmet.

[0149] The following are the results of testing the center of gravity and moment of inertia of five types of helmets using the testing device and testing method of the present invention.

[0150] Table 1. Related data of the center of gravity measurement of each helmet

[0151]

[0152] Note: The dimensions in the above table are in cm

[0153] Table 2 Related data of the moment of inertia measurement of each helmet

[0154]

[0155]

[0156] Note: The time unit in the above table is ms

[0157] Table 3 Measurement results of center of gravity and moment of inertia of each helmet

[0158]

[0159] The present invention is only described with the above embodiments, and the structure, location and connection of each component can be changed. Based on the technical solution of the present invention, any improvement or equivalent transformation of individual components based on the principle of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for testing the center of gravity and moment of inertia of a helmet, characterized in that: The following steps are involved: 1) A helmet center of gravity and moment of inertia test device is set up, which includes a helmet fixing box, a V-shaped pad, a measuring stand, a cam mechanism, a base, first to third force sensors, a vibration frequency sensor and a host computer; the helmet fixing box is used to fix the helmet to be tested; the V-shaped pad is a pad with a 90-degree V-shaped groove, and the V-shaped pad is used to place the helmet fixing box or the helmet fixing box with the helmet to be tested; the measuring stand includes a torsion pendulum stand, a bending fulcrum bearing and a butterfly plate; the torsion pendulum stand is used to fix the helmet fixing box during testing, and the center of the top surface of the torsion pendulum stand is formed with a first slide groove and a second slide groove that intersect vertically; the bending fulcrum bearing is installed at the bottom of the torsion pendulum stand, and the bending fulcrum bearing includes a moving end and a static end with the same structure, the moving end and the static end are centrally symmetrically distributed, and the moving end and the static end are connected by two pairs of cross-shaped distributed spring sheets, and the moving end is relative to the static end. The end rotates around the axis formed by the intersection of the two pairs of cross-shaped spring sheets, the moving end is fixedly connected to the bottom of the torsion pendulum frame, the static end is fixedly connected to the butterfly plate, a locking piece is arranged between the static end and the torsion pendulum frame, and the locking piece is used to lock the torsion pendulum frame on the static end together with the moving end; the cam mechanism is arranged between the butterfly plate and the base, and the cam mechanism is used to drive the measuring frame to move up and down relative to the base; the first to third force sensors are located directly below the butterfly plate and are arranged on the base in an isosceles triangle; the first to third force sensors are used to collect the gravity of the helmet fixing box or the helmet fixing box containing the helmet to be tested during testing; the vibration frequency sensor is arranged on the static end of the bending fulcrum bearing, and is used to collect the vibration frequency of the torsion pendulum frame; the first to third force sensors and the vibration frequency sensor are all connected to the host computer; 2) The position of the center of gravity of the helmet to be tested relative to itself H X , H Y , H Z The specific steps of measurement include: S1) the measuring stand is lowered to the lowest position by a cam mechanism, the butterfly plate at the bottom of the measuring stand is pressed on the first to third force sensors, and the torsion pendulum stand is locked by a locking member, and the helmet center of gravity measurement mode is entered; S2) taking the corner point shared by three adjacent and vertical faces on the helmet box as the coordinate origin and the three edges passing through the corner point as the xyz axes to form a fixed coordinate system, placing the helmet box on the oscillating stand in three steps, the first step taking the x-axis and y-axis on the helmet box parallel to the two slide grooves on the oscillating stand respectively, and aligning the center of the box surface where the xy axis is located with the center of the top surface of the oscillating stand; the second step taking the y-axis and x-axis on the helmet box parallel to the two slide grooves on the oscillating stand respectively, and aligning the center of the box surface where the yx axis is located with the center of the top surface of the oscillating stand; the third step taking the y-axis and z-axis on the helmet box parallel to the two slide grooves on the oscillating stand, and aligning the center of the box surface where the yz axis is located with the center of the top surface of the oscillating stand; S3) respectively recording the readings F of the first force sensor when the helmet fixing box is placed on the torsion pendulum stand three times in step S2) x(盒) 、F y(盒) 、F z(盒) ; Taking the projection of the line connecting the second force sensor and the third force sensor as the fulcrum and the coordinate origin O', the position of the center of gravity of the fixed helmet box relative to the coordinate origin O' is calculated by the weighing method. The calculation formula is as follows: Among them, X 盒 Indicates the position of the center of gravity of the helmet box in the x-axis direction; Y 盒 Indicates the position of the center of gravity of the helmet box in the y direction; Z 盒 Indicates the position of the center of gravity of the helmet box in the z direction; F x(盒) Indicates the first force sensor reading when the helmet box is placed for the first time; F y(盒) Indicates the reading of the first force sensor when the helmet box is placed for the second time; F z(盒) It indicates the reading of the first force sensor when the helmet box is placed for the third time; L indicates the distance between the force measuring point and the coordinate origin O'; G 盒 Indicates the weight of the helmet box; S4) placing the helmet into a helmet fixing box, wherein the x-axis on the helmet fixing box is aligned with the H-axis on the helmet. X Parallel, the y-axis is parallel to the H on the helmet Y Parallel, z-axis and H on the helmet Z In parallel, place the helmet box with the helmet on the torsion pendulum stand, and the first to third force sensors measure the weight G 盔+盒 Then repeat steps S2) and S3) to record the force reading F at one end of the first force sensor when the helmet + helmet box is placed on the torsion pendulum stand three times. x(盔+盒) 、F y(盔+盒) 、F z(盔+盒) Then the position of the center of gravity of the helmet + fixed helmet box relative to the coordinate origin O' is calculated as follows: Among them, X 盔+盒 : The position of the center of gravity of the helmet + helmet box in the x direction; Y 盔+盒 : The position of the center of gravity of the helmet + helmet box in the y direction; Z 盔+盒 : The position of the center of gravity of the helmet + helmet box in the z direction; F x(盔+盒) : The first force sensor reading when the helmet + helmet box is placed for the first time; F y(盔+盒) : The first force sensor reading when the helmet + helmet fixing box is placed for the second time; F z(盔+盒) : The first force sensor reading when the helmet + helmet box is placed for the third time; G 盔+盒 : Weight of helmet + helmet box; The position of the helmet's center of gravity relative to the coordinate origin O' is calculated as follows: Among them, X 盔 : The position of the helmet's center of gravity in the x direction; Y 盔 : The position of the helmet's center of gravity in the y direction; Z 盔 : The position of the helmet's center of gravity in the z direction; G 盔 : Helmet weight G 盔 =G 盔+盒 -G 盒 ; S5) Measure the distance L between the front edge of the helmet, the left edge of the helmet and the top of the helmet from the coordinate origin O' 前 , L 左 , L 顶 ; S6) Calculate the position H of the helmet's center of gravity relative to itself X , H Y , H Z ; The calculation formula is as follows: 3) Measure the moment of inertia of the helmet, including: I) raising the measuring stand by means of a cam mechanism, so that the butterfly plate of the measuring stand is out of contact with the first to third force sensors, unlocking the locking member, and allowing the torsion pendulum stand to rotate freely; II) The helmet fixing box is fixedly set on the oscillating stand three times. For the first time, the x-axis on the helmet fixing box is parallel to the rotation axis, the y-axis and the z-axis are parallel to the two slide grooves on the oscillating stand, and the center position of the box surface where the yz-axis is located is aligned with the center position of the top surface of the oscillating stand; for the second time, the y-axis on the helmet fixing box is parallel to the rotation axis, the center position of the box surface where the x-axis and the z-axis are located is parallel to the two slide grooves on the oscillating stand, and the center position of the box surface where the xz-axis is located is aligned with the center position of the top surface of the oscillating stand; for the third time, the z-axis on the helmet fixing box is parallel to the rotation axis, the center position of the box surface where the x-axis and the y-axis are located is parallel to the two slide grooves on the oscillating stand, and the center position of the box surface where the xy-axis is located is aligned with the center position of the top surface of the oscillating stand; each time, an initial angular displacement is given to the oscillating stand so that the oscillating stand performs torsional free vibration; III) respectively record the vibration frequencies of the torsion pendulum frame collected three times by the vibration frequency sensor in step II), obtain the periods of the torsion pendulum frame's three torsional free vibrations according to the relationship between frequency and period, and calculate the moment of inertia J according to the moment of inertia measurement formula x , J y , J z ; Where, K: torsional stiffness, fixed value is 4.57N·m / deg; J x J is the moment of inertia of the fixed helmet box with the x-axis parallel to the rotation axis and the torsional vibration of the torsion pendulum stand; y is the moment of inertia of the fixed helmet box with the y-axis parallel to the rotation axis and the torsional vibration of the torsion pendulum stand; J z is the moment of inertia of the fixed helmet box with the z-axis parallel to the rotation axis and the torsional vibration of the torsion pendulum stand; T x(盒) is the period of torsional vibration of the fixed helmet box with the x-axis parallel to the rotation axis along the torsional pendulum stand; T y(盒) is the period of torsional vibration of the fixed helmet box with the y-axis parallel to the rotation axis along the torsional pendulum stand; T z(盒) is the period of torsional vibration of the fixed helmet box with the z-axis parallel to the rotation axis along the torsion pendulum stand; IV) Put the helmet into the helmet box, repeat II) to III), and calculate J x `、J y `、J z `; In the formula, J x ` is the moment of inertia of the helmet box with the helmet placed therein, which vibrates with the torsion pendulum stand with the x-axis parallel to the rotation axis; J y ` is the moment of inertia of the torsion vibration of the torsion pendulum stand with the y-axis parallel to the rotation axis of the helmet box; J z ` is the moment of inertia of the helmet box with the helmet placed therein, which vibrates with the torsion pendulum stand with the z-axis parallel to the rotation axis; T x(盔+盒) T is the period of torsional vibration of the helmet box with the helmet placed on it with the x-axis parallel to the rotation axis; y(盔+盒) T is the period of torsional vibration of the helmet box with the helmet placed on it with the y-axis parallel to the rotation axis; z(盔+盒) The period of torsional vibration of the helmet box with the helmet placed therein with the torsional pendulum stand with the z-axis parallel to the rotation axis; V) Based on the additivity of moments of inertia, find the moment of inertia of the helmet relative to the center of rotation; The calculation formula is as follows: VI) Determine the moment of inertia of the helmet relative to its center of gravity; The calculation formula of the distance between the center of gravity and the center of rotation is as follows: Among them, X 盔： The position of the helmet's center of gravity in the x direction; Y 盔： The position of the helmet's center of gravity in the y direction; Z 盔： The position of the helmet's center of gravity in the z direction; d x : The distance between the rotation center and the coordinate origin O′ in the x-axis direction; d y : The distance between the rotation center and the coordinate origin O′ in the y-axis direction; d z : The distance between the rotation center and the coordinate origin O′ in the z-axis direction; L: The distance between the force measuring point and the coordinate origin O′; According to the theorem of parallel axis displacement of moment of inertia, the formula of the moment of inertia of the helmet around its own center of gravity is as follows: Right now: In the formula, J x ``: The moment of inertia of the helmet around its own center of gravity in the x direction; J y ``: The moment of inertia of the helmet around its own center of gravity in the y direction; J z ``: The moment of inertia of the helmet around its own center of gravity in the z direction; m is the mass of the helmet; Step III) also includes: placing the helmet fixing box on the V-block, adjusting the fixed position of the V-block on the torsion pendulum frame, respectively standing up the planes where the x and y axes, the planes where the y and z axes, and the planes where the z and x axes are located on the helmet fixing box, and aligning them with the rotation axis; giving the torsion pendulum frame an initial angular displacement each time, so that the torsion pendulum frame performs torsional free vibration; respectively recording the vibration frequency of the torsion pendulum frame collected by the vibration frequency sensor three times, obtaining the periods of the torsion free vibration of the torsion pendulum frame three times, and then calculating the moment of inertia J xy , J yz , J zx ; In the formula, J xy J is the moment of inertia of the fixed helmet box when the plane where the xy axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; yz is the moment of inertia of the fixed helmet box when the plane where the yz axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; J zx is the moment of inertia of the fixed helmet box with the torsional vibration of the torsion pendulum stand when the plane where the zx axis is located coincides with the rotation axis; T xy(盒) is the period of torsional vibration of the fixed helmet box with the plane where the xy axis is located coincident with the rotation axis; T yz(盒) is the period of torsional vibration of the fixed helmet box with the plane where the yz axis is coincident with the rotation axis; T zx(盒) is the period of torsional vibration of the fixed helmet box with the plane where the zx axis is located coincident with the rotation axis; Step IV) also includes placing a helmet fixing box with a helmet on a V-block, adjusting the fixed position of the V-block on the torsion pendulum frame, respectively standing up the planes where the x and y axes, the planes where the y and z axes, and the planes where the z and x axes are located on the helmet fixing box with the helmet, and aligning them with the rotation axis; giving the torsion pendulum frame an initial angular displacement each time so that the torsion pendulum frame performs torsional free vibration; respectively recording the vibration frequency of the torsion pendulum frame collected by the vibration frequency sensor three times, obtaining the periods of the torsion free vibration of the torsion pendulum frame three times, and then calculating the moment of inertia J xy , J yz , J zx J xy `` is the moment of inertia of the helmet box with the helmet placed on it when the plane where the xy axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; J yz ` is the moment of inertia of the helmet box with the helmet placed on it when the plane where the yz axis is located coincides with the rotation axis and the torsional vibration of the torsion pendulum stand; J zx ` is the moment of inertia of the helmet box with the helmet placed on it, when the plane where the zx axis is located coincides with the rotation axis, and when the torsion pendulum frame torsional vibrates; T xy(盔+盒) is the period of torsional vibration of the torsion pendulum stand when the plane where the xy axis of the helmet box is placed coincides with the rotation axis; T vz(盔+盒) is the period of torsional vibration of the torsion pendulum stand when the plane where the yz axis of the helmet box is placed coincides with the rotation axis; T zx(盔+盒) It is the period of torsional vibration of the torsion pendulum stand when the plane where the zx axis of the helmet box is placed coincides with the rotation axis.

2. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 1, characterized in that: The cam mechanism includes a mounting seat, a cam, a push rod and a transmission shaft; the mounting seat is fixedly mounted on the base, the cam is rotatably arranged in the mounting seat through the transmission shaft, the transmission shaft is eccentrically inserted into the cam, the push rod is vertically movably inserted into the mounting seat, a push plate is fixedly arranged on the upper end of the push rod, the push plate is in contact with the butterfly plate, and the lower end of the push rod is in contact with the circumferential surface of the cam; one end of the transmission shaft extends out of the base.

3. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 1, characterized in that: The locking member comprises stop holes respectively provided on the torsion swing frame and the static end, and a stop member movably fitted between the stop holes on the torsion swing frame and the static end; Two limiting slide plates are arranged on both sides of the butterfly plate, the two limiting slide plates are fixed on the base, grooves are respectively provided on the edges of both sides of the butterfly plate, and the limiting slide plates are slidably matched in the grooves.

4. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 2, characterized in that: The bending fulcrum bearing, butterfly plate, cam mechanism and base are all placed in a box body, the torsion swing stand extends out of the top of the box body, and an opening is arranged on the side wall of the box body, and the opening is directly opposite to one end of the transmission shaft extending out of the base.

5. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 4, characterized in that: The first, second and third force sensors are connected to the single-chip microcomputer through a multi-channel pressure transmitter circuit module, the vibration frequency sensor is connected to the single-chip microcomputer, the single-chip microcomputer is connected to the host computer, and a display panel is arranged on the outside of the box, the display panel is connected to the single-chip microcomputer, and is used to display the gravity measured by the first to third force sensors and the vibration frequency of the torsion pendulum stand.

6. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 1, characterized in that: The first to third force sensors are all BK-2S shear beam load sensors, the vibration frequency sensor is an optical pulse sensor, the optical pulse sensor is arranged on the static end, and a baffle is arranged on the torsion pendulum stand; the butterfly plate is made of aluminum alloy; The helmet fixing box is made of organic glass and comprises a box body and a box cover detachably arranged on the top of the box body.

7. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 1, characterized in that: The torsion pendulum stand includes a circular disc made of aluminum alloy, the bottom surface of the circular disc is provided with spokes and rib structure, the center of the top surface of the circular disc is provided with a first slide groove and a second slide groove intersecting vertically, a slider is slidably arranged in the first slide groove and the second slide groove, a locking member is provided on the slider to lock it in the first slide groove or the second slide groove, and scales are attached to the edges of the first slide groove and the second slide groove.

8. The method for testing the center of gravity and moment of inertia of a helmet as claimed in claim 1, characterized in that: The host computer is integrated with a test parameter setting module, a serial port data receiving module, a data processing module, a data display module and a data storage module; the test parameter setting module is used to set the test parameters; the serial port data receiving module is used to receive the force values ​​collected by the first to third force sensors and the vibration frequencies collected by the vibration frequency sensor; the data processing module is used to receive and process the force values ​​and the vibration frequency data to obtain the data of the center of gravity and the moment of inertia of the helmet to be tested; the data display module is used to transmit and display the obtained data of the center of gravity and the moment of inertia of the helmet to be tested on the interface of the host computer; the data storage module is used to store the data of the center of gravity and the moment of inertia of the helmet to be tested and the corresponding test parameters.

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