CN214096484U - Helmet center of gravity and inertia testing arrangement - Google Patents
Helmet center of gravity and inertia testing arrangement Download PDFInfo
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- CN214096484U CN214096484U CN202022951732.2U CN202022951732U CN214096484U CN 214096484 U CN214096484 U CN 214096484U CN 202022951732 U CN202022951732 U CN 202022951732U CN 214096484 U CN214096484 U CN 214096484U
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Abstract
The utility model discloses a helmet gravity center and rotational inertia testing device, which comprises a helmet fixing box, a V-shaped cushion block, a measuring rack, a cam mechanism, a base, first to third force sensors, a vibration frequency sensor and an upper computer; the helmet fixing box is used for fixedly placing a helmet to be tested; the V-shaped cushion block is a cushion block with a 90-degree V-shaped groove; the measuring rack comprises a torsional pendulum rack, a bending fulcrum bearing and a butterfly plate; the bending fulcrum bearing is arranged at the bottom of the torsional pendulum rack and comprises a movable end part and a static end part, the movable end part and the static end part are connected through two pairs of spring pieces distributed in a cross shape, the movable end part is fixedly connected to the torsional pendulum rack, the static end part is fixedly connected to the butterfly plate, and a locking piece is arranged between the static end part and the torsional pendulum rack; the cam mechanism is arranged between the butterfly plate and the base; first to third force sensor be regular triangle's arranging on the base, and the vibration frequency sensor sets up on quiet tip, and first to third force sensor and vibration frequency sensor all are connected with the host computer.
Description
Technical Field
The utility model relates to a helmet focus and inertia testing arrangement belongs to focus and inertia test technical field.
Background
The helmet is important protective equipment for the head of a human body, has wide application in various industries such as military, medical treatment, sports, entertainment and the like, and the gravity center and the rotational inertia of the helmet have great influence on the use safety, particularly the influence on pilots and astronauts, even endanger the life safety. However, the helmet is a geometrical irregular body, and the center of gravity and the moment of inertia of the helmet are difficult to calculate, so that measurement and determination are needed.
The ergonomic performance of the helmet is an important factor influencing the performance of the helmet, but the attention of the helmet is not paid for a long time, and particularly, an objective test and research means is lacked. The research conducted by the army is the most comprehensive and deep in the research on the ergonomic performance of military helmets conducted in various countries. Jeffrey (Jeffrey M.T.) at the united states air force operations center, et al, used a KGR30 mass analyzer manufactured by cosmic electronics to test and study the center of gravity of a "head model-flight helmet" system, but this study did not directly measure the center of gravity of an irregular helmet body. The assco (Asko V.) of melbourne university, australia, has established a suite of SPH-4 helmet dynamics evaluation devices, but these are relatively cumbersome and are greatly influenced by the physiological factors of the helmet wearer. At present, few objective evaluation methods for helmet shape, helmet comfort and stability are available at home and abroad, and almost no overall quantitative test evaluation for fitness is available. The domestic research on the helmet ergonomics is mainly focused on the aerospace field, but the research reports about objective evaluation methods are still quite few. The aeronautical medicine research institute has made experiments on the relationship between the weight of a military helmet, wearing time and the fatigue of cervical muscles, adopts the myoelectric power spectrum of the body surface of the cervical muscles to judge whether the cervical muscles are fatigue or not, and evaluates the fatigue degree by combining subjective wearing feeling to obtain the relationship between the weight of the military helmet and the wearing time as well as the fatigue degree of the cervical muscles. In the development process of the QGF02 helmet in our army, the practical wearing experiment of the helmet ergonomics performance is organized, and factors such as the wearing stability, the adjustment convenience and the like of the helmet are evaluated by adopting a fuzzy mathematics judgment method.
In summary, the research on the objective evaluation method of the comfort and the stability of the helmet at home and abroad is few, and no special instrument for measuring the inertia parameters, the wearing comfort and the stability of the irregular helmet exists. Therefore, it is necessary to research and develop a set of related testing equipment for quantitative research and analysis of comfort and stability of the helmet, and the accurate measurement of the center of gravity and the rotational inertia of the helmet is of great significance to evaluation, use and improvement of helmet design.
Disclosure of Invention
The utility model aims at providing a helmet focus and inertia testing arrangement who has characteristics such as easy operation, simple to operate, accuracy height, applicable in the test of various helmet focus and inertia.
In order to achieve the above purpose, the utility model adopts the following technical scheme: a device for testing the gravity center and the rotational inertia of a helmet comprises a helmet fixing box, a V-shaped cushion block, a measuring rack, a cam mechanism, a base, first to third force sensors, a vibration frequency sensor and an upper computer;
the helmet fixing box is used for fixedly placing a helmet to be tested;
the V-shaped cushion block is a cushion block with a 90-degree V-shaped groove and is used for placing a helmet fixing box or a helmet fixing box with a helmet to be tested;
the measuring rack comprises a torsional pendulum rack, a bending fulcrum bearing and a butterfly plate; the torsional pendulum rack is used for fixedly placing the helmet fixing box during testing, and a first sliding groove and a second sliding groove which are vertically intersected are formed in the center of the top surface of the torsional pendulum rack; the bending fulcrum bearing is installed at the bottom of the torsional pendulum rack and comprises a movable end part and a fixed end part which are the same in structure, the movable end part and the fixed end part are distributed in a central symmetry manner, the movable end part and the fixed end part are connected through two pairs of spring pieces distributed in a cross shape, the movable end part rotates around an axis formed by the intersection points of the two pairs of spring pieces distributed in the cross shape relative to the fixed end part, the movable end part is fixedly connected to the bottom of the torsional pendulum rack, the fixed end part is fixedly connected to the butterfly plate, a locking part is arranged between the fixed end part and the torsional pendulum rack, and the locking part is used for locking the follow-up end part of the torsional pendulum rack on the fixed end part;
the cam mechanism is arranged between the butterfly plate and the base and is used for driving the measuring rack to move up and down relative to the base;
the first force sensor, the second force sensor, the third force sensor and the fourth force sensor are positioned right below the butterfly-shaped plate and are arranged on the base in an isosceles triangle shape; the first to third force sensors are used for collecting the gravity of the helmet fixing box or the helmet fixing box containing a helmet to be tested during testing;
the vibration frequency sensor is arranged on the static end part of the bending fulcrum bearing and is used for collecting the vibration frequency of the torsional pendulum rack;
the first to third force sensors and the vibration frequency sensor are connected with an upper computer.
In some embodiments, the cam mechanism comprises a mount, a cam, a ram, and a drive 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 arranged on the cam in a penetrating manner, the ejector rod is vertically and movably arranged on the mounting seat in a penetrating manner, the upper end of the ejector rod is fixedly provided with a top plate, the top plate is in contact with the butterfly-shaped plate, and the lower end of the ejector rod is in contact with the circumferential surface of the cam; one end of the transmission shaft extends out of the base.
In some embodiments, the locking member includes stop holes opened on the torsional pendulum platform and the stationary end portion, respectively, and a stop member movably fitted between the torsional pendulum platform and the stop holes on the stationary end portion.
In some embodiments, two limiting sliding plates are arranged on two sides of the butterfly-shaped plate, the two limiting sliding plates are fixed on the base, two side edges of the butterfly-shaped plate are respectively provided with a groove, and the limiting sliding plates are in sliding fit in the grooves.
In some embodiments, the bending fulcrum bearing, the butterfly plate, the cam mechanism and the base are all arranged in a box, the torsional pendulum rack extends out of the top of the box, the side wall of the box is provided with an opening, and the opening is opposite to one end, extending out of the base, of the transmission shaft.
In some embodiments, the first, second and third force sensors are connected to the single chip microcomputer through a multi-path pressure transmission circuit module, the vibration frequency sensor is connected to the single chip microcomputer, the single chip microcomputer is connected to the upper computer, a display panel is arranged outside the box body, and the display panel is connected to the single chip microcomputer and used for displaying the gravity measured by the first to third force sensors and the vibration frequency of the torsional pendulum rack.
In some embodiments, the first to third force sensors are all BK-2S-shaped 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 blocking sheet is arranged on the torsional pendulum rack; 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 at the top of the box body.
In some embodiments, the torsional pendulum rack comprises a disc made of an aluminum alloy material, the bottom surface of the disc is provided with spokes and a rib plate structure, the center of the top surface of the disc is provided with a first sliding groove and a second sliding groove which are vertically intersected, sliding blocks are arranged in the first sliding groove and the second sliding groove in a sliding mode, locking pieces which lock the sliding blocks in the first sliding groove or the second sliding groove are arranged on the sliding blocks in a sliding mode, and graduated scales are attached to the edges of the first sliding groove and the second sliding groove.
The utility model adopts the above technical scheme, it has following advantage: the utility model provides a helmet focus and inertia testing arrangement, utilize cam mechanism drive to measure the rack and make elevating movement, make testing arrangement measure at the helmet focus and the inertia measurement state switches, the gravity of deciding the helmet box or putting the helmet box of the helmet that awaits measuring in first to third force sensor that distributes on the butterfly plate when the test, the vibration frequency of torsional pendulum rack is gathered to the vibration frequency sensor, and then calculate the focus position and the inertia that obtain the helmet that awaits measuring, whole testing arrangement has easy operation, simple to operate, characteristics such as accuracy height, it is applicable in various helmet focuses and inertia's test, to the evaluation, use and improvement helmet design have important meaning.
Drawings
Fig. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic structural view of a V-shaped cushion block for placing a helmet box according to the present invention;
fig. 3 is a schematic structural view of the torsional pendulum stand of the present invention;
fig. 4 is a schematic structural view of the bending fulcrum bearing of the present invention;
FIG. 5 is a schematic view of the structure of FIG. 4 taken along line A-A;
fig. 6 is a schematic structural view of a butterfly plate of the present invention;
fig. 7 is a schematic structural diagram of the cam mechanism of the present invention;
fig. 8 is a schematic diagram of the cam mechanism of the present invention;
fig. 9 is a block diagram of the flow of connection between the first to third force sensors and the vibration frequency sensor of the present invention and the upper computer;
fig. 10 is a diagram illustrating the definition of the coordinate system of the helmet of the present invention.
Fig. 11 is a top layout view of the first, second and third force sensors of the present invention;
FIG. 12 is a schematic diagram of the measurement of the center of gravity of the helmet of the present invention;
FIG. 13 is a schematic view of the present invention showing a coordinate system fixed to the helmet mounting case;
fig. 14 is a schematic view of the helmet fixing box with a helmet placed thereon for measuring the moment of inertia of the present invention, and fig. 14a is a schematic view of the helmet fixing box with the x-axis parallel to the rotation axis and the y-axis and the z-axis parallel to the two sliding grooves on the swing rack; FIG. 14b is a schematic view showing the y-axis of the helmet fixing box being parallel to the rotation axis, and the center positions of the box surfaces of the x-axis and the z-axis being parallel to the two sliding grooves on the swing frame; FIG. 14c is a schematic view showing that the z-axis of the helmet fixing box is parallel to the rotation axis, and the center of the box surface of the x-axis and the y-axis is parallel to the two sliding grooves of the swing frame; FIG. 14d is a schematic view of the x and y axes of the helmet mounting box in a plane coincident with the rotation axis; FIG. 14e is a schematic view of the helmet box with the y and z axes in a plane coincident with the rotation axis; fig. 14f is a schematic view of the helmet box with the z and x axes in the plane coincident with the rotation axis.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the objects, features and advantages of the invention can be more clearly understood. It should be understood that the embodiments shown in the drawings are not intended as limitations on the scope of the invention, but are merely illustrative of the true spirit of the technical solution of the invention.
As shown in fig. 1 to 6, the utility model provides a device for testing the gravity center and the rotational inertia of a helmet, which comprises a helmet fixing box 1, a V-shaped cushion block 2, a measuring rack, a cam mechanism 6, a base 7, a first force sensor, a second force sensor, a third force sensor, a vibration frequency sensor and an upper computer; the helmet fixing box 1 is used for fixedly placing a helmet to be tested; the V-shaped cushion block 2 is a cushion block with a 90-degree V-shaped groove, and the V-shaped cushion block 2 is used for placing the helmet fixing box 1 or the helmet fixing box 1 with a helmet to be tested; the measuring rack comprises a torsional pendulum rack 3, a bending fulcrum bearing 4 and a butterfly plate 5; the torsional pendulum rack 3 is used for fixedly placing the helmet fixing box 2 during testing, and a first sliding groove and a second sliding groove which are vertically intersected are formed in the center of the top surface of the torsional pendulum rack 3; the bending fulcrum bearing 4 is installed at the bottom of the torsional pendulum rack 3, the bending fulcrum bearing 4 comprises a movable end part 41 and a static end part 42 which are the same in structure, the movable end part 41 and the static end part 42 are distributed in a central symmetry manner, the movable end part 41 and the static end part 42 are connected through two pairs of spring pieces 43 distributed in a cross shape, the movable end part 41 rotates around an axis formed by cross points of the spring pieces 43 relative to the static end part 42, the movable end part 41 is fixedly connected to the bottom of the torsional pendulum rack 3, the static end part 42 is fixedly connected to the butterfly plate 5, a locking piece is arranged between the static end part 42 and the torsional pendulum rack 3, and the locking piece is used for locking the follow-up end part 41 of the torsional pendulum rack 3 on the static end part 42; the cam mechanism 6 is arranged between the butterfly plate 5 and the base 7, and the cam mechanism 6 is used for driving the measuring rack to move up and down relative to the base 7; the first to third force sensors are positioned under the butterfly plate 5, arranged on the base 7 in an isosceles triangle shape and used for collecting the gravity of the helmet fixing box 1 or the helmet fixing box 1 containing a helmet to be tested during testing, and the vibration frequency sensor is arranged on the static end part 42 of the bending fulcrum bearing 4 and used for collecting the vibration frequency of the torsional pendulum rack 3; the first to third force sensors and the vibration frequency sensor are connected with an upper computer.
In the above embodiment, preferably, as shown in fig. 7 and 8, the cam mechanism 6 includes the mount 61, the cam 62, the jack 63, and the transmission shaft 64; the mounting base 61 is fixedly mounted on the base 7, the cam 62 is rotatably arranged in the mounting base 61 through a transmission shaft 64, the transmission shaft 64 is eccentrically arranged on the cam 62 in a penetrating manner, the ejector rod 63 is vertically and movably arranged on the mounting base 61 in a penetrating manner, the upper end of the ejector rod 63 is in contact with the butterfly plate 5, and the lower end of the ejector rod 63 is in contact with the circumferential surface of the cam 62; one end of the transmission shaft 64 protrudes outside the base 7.
In the above embodiment, preferably, the cam mechanism further includes a top plate 65, the top plate 65 is fixed to the upper end of the top bar 63, and the top plate 65 is in contact with the butterfly plate 5.
In the above embodiment, preferably, the locking member includes a stopper hole opened in the swing frame 3 and the stationary end 42, respectively, and a stopper (e.g., a latch) is movably fitted between the swing frame 3 and the stopper hole in the stationary end 42, thereby preventing the swing frame 3 from rotating when the center of gravity measurement is performed.
In the above embodiment, preferably, as shown in fig. 6, two limiting sliding plates 8 are arranged on two sides of the butterfly-shaped plate 5, the two limiting sliding plates 8 are fixed on the base 7, two side edges of the butterfly-shaped plate 5 are respectively provided with a groove, and the limiting sliding plates 8 are slidably fitted in the grooves; when the cam adjusting mechanism is used for lifting or lowering the height of the torsional pendulum rack 3, the butterfly plate 5 moves up and down along the limiting sliding plate 8, the measuring rack is limited to move up and down only, the rotating center of the measuring rack is guaranteed to be unchanged, and the measuring precision of the testing device is improved.
In the above embodiment, preferably, the bending fulcrum bearing 4, the butterfly plate 5, the cam mechanism 6 and the base 7 are all disposed in the box, the torsional pendulum platform 3 extends out of the top of the box, and the side wall of the box is provided with an opening which is opposite to the end of the transmission shaft 64 extending out of the base 7. During the use, hexagon socket spanner accessible trompil stretches into in the box to with the cooperation of transmission shaft 64, tester passes through the spanner drive transmission shaft 64 in the box outside and rotates, and transmission shaft 64 drives cam 62 and rotates, and cam 63 promotes the ejector pin and makes up-and-down motion, and then realizes the up-and-down motion of torsional pendulum rack 3, realizes the conversion that helmet focus and inertia measured.
In the above embodiment, preferably, as shown in fig. 9, the first, second, and third force sensors are connected to the single chip microcomputer through a multi-path pressure transmitting circuit module, the vibration frequency sensor is connected to the single chip microcomputer, the single chip microcomputer is connected to the upper computer, and the single chip microcomputer processes data transmitted from the first to third force sensors and the vibration frequency sensor to obtain force values collected by the first to third force sensors and a vibration period of the torsional pendulum frame, and transmits the force values and the vibration period to the upper computer; the outside of box is provided with display panel, and display panel is connected with the singlechip, and display panel is used for showing the gravity of first to third force transducer measurement and the vibration frequency of torsional pendulum rack 3.
In the above embodiment, preferably, the first to third force sensors each employ a BK-2S-type shear beam load sensor, the vibration frequency sensor employs an optical pulse sensor, the optical pulse sensor is disposed on the stationary end portion 42, the torsional pendulum frame 3 is provided with a blocking piece, when torsional vibration is performed, the blocking piece moves back and forth between the transmitting end and the receiving end of the optical pulse sensor, and the sensor measurement frequency is the vibration frequency of the torsional pendulum frame multiplied by the number of the blocking pieces, so that the vibration frequency of the torsional pendulum frame 3 can be obtained, and the vibration period of the torsional pendulum frame 3 can be calculated; the single chip microcomputer adopts a PIC18F25K22 single chip microcomputer, and is connected to an upper computer through an RS485 bus.
In the above embodiment, preferably, as shown in fig. 3, the swing frame 3 includes a disc made of an aluminum alloy material, the bottom surface of the disc is provided with spokes and a rib plate structure, the center of the top surface of the disc is provided with a first sliding groove and a second sliding groove which are vertically intersected, the first sliding groove and the second sliding groove are both provided with sliding blocks in a sliding manner, the sliding blocks are provided with locking members which lock the sliding blocks in the first sliding groove or the second sliding groove, and the edges of the first sliding groove and the second sliding groove are attached with scale scales.
In the above embodiment, the butterfly plate 5 is preferably made of an aluminum alloy.
In the above embodiment, the helmet fixing box 1 is preferably made of organic glass, and includes a box body and a box cover detachably disposed on the top of the box body.
In the above embodiment, preferably, the upper 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 for setting test parameters, such as torsional rigidity K, helmet parameters (type, quality and the like), and helmet box parameters (type, quality and the like); the serial port data receiving module is used for receiving force values F1, F2 and F3 acquired by the first to third force sensors and vibration frequency acquired by the vibration frequency sensor, and the data processing module is used for receiving and processing the force values F1, F2, F3 and the vibration frequency data to obtain data of the gravity center and the rotational inertia of the helmet to be tested; the data display module is used for transmitting and displaying the obtained data of the gravity center and the rotational inertia of the helmet to be tested on an interface of the upper computer; the data storage module is used for storing the gravity center and the rotational inertia data of the helmet to be tested and corresponding test parameters.
Based on the device for testing the gravity center and the rotational inertia of the helmet, the utility model also provides a method for testing the gravity center and the rotational inertia of the helmet, which comprises the following steps,
1) carrying out the position H of the gravity center C of the helmet to be measured relative to the helmet to be measuredX、HY、HZIn which, as shown in figure 10,HXis the distance of the center of gravity C from the left edge of the helmet, HYThe distance from the center of gravity C to the front edge of the helmet; hZThe distance of the center of gravity C from the top of the helmet.
The gravity center of the irregular object such as the helmet is measured by adopting a weighing method. The weighing method is a method based on the lever principle, as shown in fig. 11 and 12, the projection of the connecting line of the second force sensor and the third force sensor is selected as a fulcrum and a coordinate origin O', and the gravity of the object and the supporting force of the first force sensor are equivalent to the lever acting force. As long as the force reading F of the measured object at one end of the force sensor is known, the gravity center position Gx of the measured object in the x direction can be calculated by adopting the following formula.
In the formula: g is the weight of the measured object, G ═ F1+F2+F3(ii) a F is the first force sensor reading, F ═ F1(ii) a L is the distance between the force measuring point and the origin of coordinates O', and L is equal to L1+L2。
The center of gravity position Gy of the measured object in the y direction is obtained by horizontally rotating the measured object by 90 degrees, and the center of gravity position Gz of the measured object in the z direction is obtained by vertically rotating the measured object by 90 degrees, so that the center of gravity position of the measured object with respect to the coordinate system (the origin of coordinates O' in fig. 12) can be determined. But in practice the position of the center of gravity relative to itself makes sense. For this purpose, the helmet to be tested is fixed in a lightweight box (helmet box) that ensures three mutually perpendicular planes, with the three edges passing through the corner points as xyz axes, as shown in fig. 13. The effect of the helmet fixing box can enable stable measurement of the army helmet to be possible, and the position of the gravity center of the army helmet relative to the self reference surface can be obtained by taking the box surface of the helmet fixing box as the reference positioning surface.
In actual measurement, the gravity center positions of the helmet without the helmet and the helmet with the helmet are measured respectively, that is, the gravity center position of the helmet box is measured, and then the influence of the helmet box is deducted through calculation, so that the position of the gravity center of the helmet relative to the gravity center of the helmet can be obtained (as shown in fig. 10).
Whereby the position H of the centre of gravity of the helmet relative to itselfX、HY、HZThe specific steps of the measurement of (1) include:
s1) the measuring rack is descended to the lowest position through the cam mechanism 6, the butterfly plate 5 at the bottom of the measuring rack is ensured to be pressed on the first to third force sensors, the torsional pendulum rack 3 is locked by the locking piece, and the helmet gravity center measuring mode is started;
s2) taking a common angular point of three adjacent and vertical surfaces on the helmet fixing box 1 as a coordinate origin, taking three edges passing the angular point as xyz axes to form a fixed coordinate system (as shown in figure 13), placing the helmet fixing box 1 on the swing rack 3 for three times, wherein the x axis and the y axis on the helmet fixing box 1 are respectively parallel to two sliding grooves on the swing rack 3 for the first time, and the center position of the box surface where the xy axis is positioned is aligned with the center of the top surface of the swing rack 3; the y axis and the x axis on the helmet fixing box 1 are respectively parallel to the two sliding grooves on the torsion pendulum rack 3 for the second time, 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 torsion pendulum rack; and the y-axis and the z-axis on the helmet fixing box 1 are parallel to the two sliding grooves on the torsion pendulum rack 3 for the third time, and the center of the box surface where the yz-axis is located is aligned with the center of the top surface of the torsion pendulum rack.
S3) recording the readings F of the first force sensor when the helmet fixing box 1 is placed on the wig stand 3 in three times in the step S2), respectivelyx (Box)、Fy (Box)、Fz (Box)(ii) a The position of the center of gravity of the helmet box 1 with respect to the coordinate system (origin of coordinates O' in fig. 12) is calculated by the following formula:
wherein, XBoxThe position of the center of gravity of the helmet mounting box 1 in the x-axis direction is shown; y isBoxThe position of the gravity center of the helmet box 1 in the y direction is shown; zBoxShowing the position of the center of gravity of the helmet mounting box 1 in the Z direction; fx (Box)Indicating a first force sensor reading when the helmet box 1 is first placed; fy (Box)Indicating a first force sensor reading when the helmet box 1 is placed a second time; fz (Box)Indicating a first force sensor reading at a third placement of the headgear box; l meterThe distance (fixed value 25cm) from the force measurement point to the origin of coordinates O' is shown; gBoxThe weight of the helmet box is indicated (fixed value 0.955 kg).
S4) putting the helmet into the helmet box 1, wherein the x-axis of the helmet box 1 and the H-axis of the helmet areXParallel to the y-axis and H on the helmetYParallel to the z-axis and H on the helmetZIn parallel, the helmet box 1 with the helmet is placed on the swing frame 3, and the first to third force sensors measure the weight GHelmet and box(ii) a Then, the steps S2) and S3) are repeated, and the reading F of the end force of the first force sensor when the helmet and the helmet fixing box are placed on the torsional pendulum rack 3 for three times is recorded respectivelyx (helmet and box)、Fy (helmet and box)、Fz (helmet and box)，
The position of the center of gravity of the helmet + the helmet box relative to the coordinate system (the origin of coordinates O' in fig. 12) is calculated as follows:
wherein, XHelmet and box: the gravity center of the helmet and the helmet fixing box is positioned in the x direction; y isHelmet and box: the position of the gravity center of the helmet and the helmet fixing box in the y direction; zHelmet and box: the position of the gravity center of the helmet and the helmet fixing box in the z direction; fx (helmet and box): reading a first force sensor when the helmet and the helmet fixing box are placed for the first time; fy (helmet and box): reading the first force sensor when the helmet and the helmet fixing box are placed for the second time; fz (helmet and box): reading the first force sensor when the helmet and the helmet fixing box are placed for the third time; gHelmet and box: helmet + helmet box weight.
The position of the center of gravity of the helmet with respect to the coordinate system (origin O' in fig. 12) is calculated as follows:
wherein, XHelmet: the position of the center of gravity of the helmet in the x-direction; y isHelmet: the position of the helmet center of gravity in the y-direction; zHelmet: helmet center of gravityA position in the z direction; gHelmet: weight G of helmetHelmet＝GHelmet and box-GBox。
S5) measuring the distance L of the front edge of the helmet, the left edge of the helmet, and the top of the helmet from the coordinate system (the origin O' of coordinates in fig. 12)Front side、LLeft side of、LTop roof；
S6) calculating the position H of the gravity center of the helmet relative to the helmetX、HY、HZ。
The calculation formula is as follows:
wherein: hX: distance of the center of gravity of the helmet from the left edge of the helmet; hY: the distance of the center of gravity of the helmet from the front edge of the helmet; hZ: distance of the center of gravity of the helmet from the top of the helmet; l isFront side: distance of the front edge of the helmet from the origin of coordinates O'; l isLeft side of: distance of left edge of helmet from origin of coordinates O'; l isTop roof: the distance from the top of the helmet top to the origin of coordinates O'; gHelmet: the weight of the helmet.
2) The measurement of the moment of inertia of the helmet is carried out,
for measuring the moment of inertia of an irregular object such as a helmet, a torsion pendulum method is adopted in the device, and a measuring schematic diagram is shown in fig. 2. The principle is based on the isochronism of free torsional vibrations. The purpose of measuring the rotational inertia of the object is achieved by measuring the frequency (or period) of the free torsional vibration of the object.
The object to be measured is placed on a disc which is torsionally vibrated about a fixed axis. The disc is constrained by a torsion spring of stiffness K. Giving an initial angular displacement, making the disk do free torsional vibration, and the moment of inertia of the system around the rotation center is:
in the formula, J is the moment of inertia of the system around the rotation center, and T is the inherent period of torsional vibration; k is the torsional stiffness, i.e. the torsional stiffness of the torsion spring, with a value of 4.75.
Therefore, the measuring process of the rotational inertia of the helmet specifically comprises the following steps:
I) the measuring rack is lifted through the cam mechanism 6, so that the butterfly plate 5 of the measuring rack is separated from the contact with the first force sensor, the third force sensor and the fourth force sensor, the locking piece is unlocked, and the torsional pendulum rack 3 is enabled to rotate freely;
II) fixedly arranging the helmet fixing box 1 on the torsion pendulum platform frame for the first time in three times, wherein as shown in figure 14a, an x axis on the helmet fixing box 1 is parallel to a rotating shaft, y and z axes are parallel to two sliding grooves on the torsion pendulum platform frame 3, and the central position of a box surface where the yz axis is positioned is aligned with the central position of the top surface of the torsion pendulum platform frame 3; for the second time, as shown in fig. 14b, the y axis on the helmet fixing box 1 is parallel to the rotation axis, the central positions of the box surfaces where the x and z axes are located are parallel to the two sliding grooves on the swing frame 3, and the central position of the box surface where the xz axis is located is aligned with the central position of the top surface of the swing frame 3; thirdly, as shown in fig. 14c, the z axis on the helmet fixing box 1 is parallel to the rotating shaft, the central positions of the box surfaces of the x and y axes are parallel to the two sliding grooves on the swing frame 3, and the central position of the box surface of the xy axis is aligned to the central position of the top surface of the swing frame 3; giving an initial angular displacement to the torsional pendulum rack 3 each time to enable the torsional pendulum rack 3 to do torsional free vibration;
III) respectively recording the vibration frequency of the torsional pendulum rack 3 acquired by the vibration frequency sensor three times in the step II), obtaining the period of the torsional pendulum rack 3 three-time torsional free vibration according to the relationship between the frequency and the period, and calculating according to a rotational inertia measurement formula to obtain a rotational inertia Jx、Jy、Jz；
In the formula, JxThe moment of inertia of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is parallel to the x axis and the rotating shaft; j. the design is a squareyThe moment of inertia of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is parallel to the y axis and the rotating shaft; j. the design is a squarezTorsional vibration of the torsional pendulum platform 3 parallel to the z-axis and the rotation axis for the helmet fixing box 1The moment of inertia of (a); t isx (Box)The period of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is parallel to the x axis and the rotating axis; t isy (Box)The period of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is parallel to the y axis and the rotating shaft; t isz (Box)The period of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is parallel to the rotation axis in the z axis.
IV) placing the helmet fixing box 1 on the V-shaped block 2, adjusting the fixed position of the V-shaped block 2 on the swing rack 3, and respectively erecting the plane of the x and y axes, the plane of the y and z axes, and the plane of the z and x axes on the helmet fixing box 1 and coinciding with the rotating shaft (as shown in figures 14d-14 f); giving an initial angular displacement to the torsional pendulum rack 3 each time to enable the torsional pendulum rack 3 to do torsional free vibration; respectively recording the vibration frequency of the torsional pendulum rack 3 acquired by the vibration frequency sensor for three times to obtain the period of the torsional pendulum rack 3 with three-time torsional free vibration, and then calculating to obtain the moment of inertia Jxy、Jyz、Jzx；
In the formula, JxyThe rotational inertia of torsional vibration of the torsional pendulum rack 3 is superposed with the rotating shaft by the plane of the xy axis of the helmet fixing box 1; j. the design is a squareyzThe moment of inertia of torsional vibration of the torsional pendulum rack 3 is superposed by the plane of the yz axis of the helmet fixing box 1 and the rotating shaft; j. the design is a squarezxThe moment of inertia of torsional vibration of the torsional pendulum rack 3 is superposed by the plane of the zx axis of the helmet fixing box 1 and the rotating shaft; t isxy (Box)The period of torsional vibration of the torsional pendulum rack 3 which is coincided with the rotating shaft by the plane of the xy axis of the helmet fixing box 1; t isyz (Box)The period of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is coincident with the plane of the yz axis and the rotating shaft; t iszx (Box)The period of torsional vibration of the helmet fixing box 1 along with the torsional pendulum rack 3 is coincident with the plane of the zx axis and the rotating axis.
V) putting the helmet into the helmet box 1, repeating II-IV to obtain Jx`、Jy`、Jz`、Jxy`、Jyz`、Jzx`；
In the formula, JxThe moment of inertia of torsional vibration along with the torsional pendulum rack 3 is parallel to the rotation axis by the x axis of the helmet fixing box 1 with the helmet; j. the design is a squareyThe moment of inertia of torsional vibration along with the torsional pendulum rack 3 is parallel to the rotation axis by the y axis of the helmet fixing box 1; j. the design is a squarezThe moment of inertia of torsional vibration along with the torsional pendulum rack 3 is parallel to the rotating shaft by the z axis of the helmet fixing box 1 with the helmet; t isx (helmet and box)The period of torsional vibration of the helmet fixing box 1 with the helmet along with the torsional pendulum rack 3 is parallel to the rotation axis by the x axis; t isy (helmet and box)The period of torsional vibration of the helmet fixing box 1 with a helmet along with the torsional pendulum rack 3 is parallel to the rotation axis by the y axis; t isz (helmet and box)The helmet fixing box 1 for holding the helmet has a period of torsional vibration along with the torsional pendulum platform 3 with the z-axis parallel to the rotation axis. J. the design is a squarexy"is the moment of inertia of torsional vibration of the swing-following platform 3, which is superposed with the rotating shaft by the plane of the xy axis of the helmet fixing box with the helmet; j. the design is a squareyzThe moment of inertia of torsional vibration along with the torsional pendulum rack 3 is superposed by a plane of a yz axis of the helmet fixing box 1 with a helmet and a rotating shaft; j. the design is a squarezxThe moment of inertia of torsional vibration along with the torsional pendulum rack 3 is superposed by the plane of the zx axis of the helmet fixing box 1 with the helmet and the rotating shaft; t isxy (helmet and box)The period of torsional vibration of the rack 3 which is coincided with the rotating shaft by the plane of the xy axis of the helmet fixing box 1 with the helmet is; t isyz (helmet and box)The period of torsional vibration of the rack 3 which is coincident with the rotation axis and is formed by the plane of the yz axis of the helmet fixing box 1 provided with the helmet; t iszx (helmet and box)The period of torsional vibration of the helmet fixing box 1 with the zx axis is coincident with the rotating axis along with the torsional pendulum rack 3.
VI) solving the rotational inertia of the helmet relative to a rotational center (namely a rotation center) according to the additivity of the rotational inertia;
the calculation formula is as follows:
VII) calculating the moment of inertia of the helmet relative to the gravity center of the helmet.
The calculation formula of the distance between the self gravity center and the rotation center is as follows:
wherein, XHelmet: the position of the center of gravity of the helmet in the x-direction; y isHelmet: the position of the helmet center of gravity in the y-direction; zHelmet: the position of the helmet center of gravity in the z-direction; dx: the distance between the rotation center and the coordinate origin O' in the direction of the x axis; dy: the distance between the rotation center and the coordinate origin O' in the y-axis direction; dz: the distance between the rotation center and the origin of coordinates O' in the z-axis direction; l: the distance (fixed value 25cm) of the force measuring point from the coordinate origin O';
according to the theorem of parallel axis shift of moment of inertia: j' ═ J-md2
Wherein: 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 gravity center of the measured object and the rotation center.
The formula for the moment of inertia of the helmet about its own centre of gravity is as follows:
namely:
wherein, K: torsional rigidity, fixed value 4.57 N.m/deg; j. the design is a squarex' is as follows: the moment of inertia of the helmet about its own center of gravity in the x-direction; j. the design is a squarey' is as follows: the moment of inertia of the helmet about its own center of gravity in the y-direction; j. the design is a squarez' is as follows: the moment of inertia of the helmet about its own center of gravity in the z-direction; and m is the mass of the helmet.
The following is the result of testing the gravity center and the rotational inertia of five types of helmets by using the testing device and the testing method of the utility model,
TABLE 1 center of gravity measurement related data for each helmet
Note: the unit of the dimension in the upper table is cm
TABLE 2 measurement of rotational inertia of each helmet
Note: the time unit in the above table is ms
TABLE 3 center of gravity and moment of inertia measurement results for each helmet
The present invention has been described only with reference to the above embodiments, and the structure, arrangement position and connection of the components may be changed. On the basis of the technical scheme of the utility model, the all sides according to the utility model discloses the principle is all not excluded to the improvement that individual part goes on or the transform of equivalence the utility model discloses a protection scope is outside.
Claims (8)
1. The utility model provides a helmet focus and inertia testing arrangement which characterized in that: the device comprises a helmet fixing box, a V-shaped cushion block, a measuring rack, a cam mechanism, a base, first to third force sensors, a vibration frequency sensor and an upper computer;
the helmet fixing box is used for fixedly placing a helmet to be tested;
the V-shaped cushion block is a cushion block with a 90-degree V-shaped groove and is used for placing a helmet fixing box or a helmet fixing box with a helmet to be tested;
the measuring rack comprises a torsional pendulum rack, a bending fulcrum bearing and a butterfly plate; the torsional pendulum rack is used for fixedly placing the helmet fixing box during testing, and a first sliding groove and a second sliding groove which are vertically intersected are formed in the center of the top surface of the torsional pendulum rack; the bending fulcrum bearing is installed at the bottom of the torsional pendulum rack and comprises a movable end part and a fixed end part which are the same in structure, the movable end part and the fixed end part are distributed in a central symmetry manner, the movable end part and the fixed end part are connected through two pairs of spring pieces distributed in a cross shape, the movable end part rotates around an axis formed by the intersection points of the two pairs of spring pieces distributed in the cross shape relative to the fixed end part, the movable end part is fixedly connected to the bottom of the torsional pendulum rack, the fixed end part is fixedly connected to the butterfly plate, a locking part is arranged between the fixed end part and the torsional pendulum rack, and the locking part is used for locking the follow-up end part of the torsional pendulum rack on the fixed end part;
the cam mechanism is arranged between the butterfly plate and the base and is used for driving the measuring rack to move up and down relative to the base;
the first force sensor, the second force sensor, the third force sensor and the fourth force sensor are positioned right below the butterfly-shaped plate and are arranged on the base in an isosceles triangle shape; the first to third force sensors are used for collecting the gravity of the helmet fixing box or the helmet fixing box containing a helmet to be tested during testing;
the vibration frequency sensor is arranged on the static end part of the bending fulcrum bearing and is used for collecting the vibration frequency of the torsional pendulum rack;
the first to third force sensors and the vibration frequency sensor are connected with an upper computer.
2. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 1, wherein: the cam mechanism comprises a mounting seat, a cam, a mandril 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 arranged on the cam in a penetrating manner, the ejector rod is vertically and movably arranged on the mounting seat in a penetrating manner, the upper end of the ejector rod is fixedly provided with a top plate, the top plate is in contact with the butterfly-shaped plate, and the lower end of the ejector rod is in contact with the circumferential surface of the cam; one end of the transmission shaft extends out of the base.
3. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 1, wherein: the locking piece comprises stop holes which are respectively arranged on the torsional pendulum stand and the static end part, and a stop piece which is movably matched between the torsional pendulum stand and the stop holes on the static end part.
4. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 1, wherein: two limiting sliding plates are arranged on two sides of the butterfly-shaped plate and fixed on the base, grooves are respectively formed in edges of two sides of the butterfly-shaped plate, and the limiting sliding plates are in sliding fit in the grooves.
5. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 2, wherein: the bending fulcrum bearing, the butterfly plate, the cam mechanism and the base are arranged in the box body, the torsional pendulum rack extends out of the top of the box body, a hole is formed in the side wall of the box body, and the hole is opposite to one end, extending out of the base, of the transmission shaft.
6. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 5, wherein: first, second and third force transducer pass through multichannel pressure transmission circuit module and are connected with the singlechip, the vibration frequency sensor is connected with the singlechip, the singlechip with the host computer is connected, and the outside of box is provided with display panel, and display panel is connected with the singlechip for show first to third force transducer measuring gravity and the vibration frequency of twisting pendulum rack.
7. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 1, wherein: the first force sensor, the second force sensor, the third force sensor, the vibration frequency sensor and the torsional pendulum rack are arranged in sequence, the first force sensor, the second force sensor and the third force sensor are all BK-2S-shaped shear beam load sensors, the vibration frequency sensor is an optical pulse sensor, the optical pulse sensor is arranged on the static end portion, and a blocking piece is arranged on the torsional pendulum rack; 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 at the top of the box body.
8. A helmet center of gravity and moment of inertia test apparatus as claimed in claim 1, wherein: the torsional pendulum rack comprises a disc made of an aluminum alloy material, spokes and a rib plate structure are arranged on the bottom surface of the disc, a first sliding groove and a second sliding groove which are intersected vertically are formed in the center of the top surface of the disc, sliding blocks are arranged in the first sliding groove and the second sliding groove in an all-sliding mode, locking pieces which are arranged in the first sliding groove or the second sliding groove are arranged on the sliding blocks in a locking mode, and a graduated scale is attached to the edges of the first sliding groove and the second sliding groove.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202022951732.2U CN214096484U (en) | 2020-12-08 | 2020-12-08 | Helmet center of gravity and inertia testing arrangement |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022951732.2U CN214096484U (en) | 2020-12-08 | 2020-12-08 | Helmet center of gravity and inertia testing arrangement |
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| CN214096484U true CN214096484U (en) | 2021-08-31 |
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| CN202022951732.2U Active CN214096484U (en) | 2020-12-08 | 2020-12-08 | Helmet center of gravity and inertia testing arrangement |
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