Static friction coefficient measuring device

Abstract

The utility model discloses a static friction coefficient measuring device which comprises a friction assembly, an electromagnetic balance assembly, an electromagnetic coil driving circuit, a width modulation pulse signal circuit and a data processing assembly, the friction assembly comprises a sliding bottom plate and a sliding block, the electromagnetic balance assembly comprises a supporting rod, a permanent magnet, a coil, a light-emitting diode, a light shielding plate and a photosensitive diode, and the supporting rod drives the light shielding plate to move up and down so that the photosensitive diode can receive illumination of the light-emitting diode; the electromagnetic coil driving circuit is used for applying current to the coil according to a current signal generated by photoelectric conversion; the width modulation pulse signal circuit is used for generating a width modulation pulse signal corresponding to the current applied to the coil; and the data processing assembly is used for determining a force value applied to the sliding block according to the width modulation pulse signal, and performing calculation by combining the mass of the sliding block to obtain a friction coefficient value. By adopting the electromagnetic balance system, the sliding starting moment can be captured with high sensitivity, and the accuracy of static friction coefficient measurement is improved.

Description

Technical Field

[0001] This utility model relates to a static friction coefficient measuring device, belonging to the field of static friction coefficient testing of materials. Background Technology

[0002] The coefficient of friction is the ratio of the force between two material surfaces to the perpendicular force acting on the surface. It is related to the surface roughness but independent of the contact area. Methods for measuring the coefficient of friction are mainly divided into the inclined plane method and the horizontal method. The inclined plane method involves placing the sample on the surface of a substrate, adjusting the inclination angle of the substrate to allow the sample to slide under gravity, and calculating the static friction coefficient by measuring the inclination angle of the substrate when the sample begins to slide. The horizontal method uses a horizontal force to pull the sample along the substrate surface, recording the force at the start of the movement and the normal force exerted by the sample on the substrate to calculate the static friction coefficient.

[0003] Currently, existing measuring devices using the inclined plane method, whether adjusting the substrate tilt angle manually or mechanically, suffer from experimental errors due to mechanical vibration. Furthermore, the substrate's rotational angular velocity affects the coefficient of friction. While existing measuring devices using the horizontal method do not have these problems, they still suffer from sluggish force signal recording when using force gauges or electronic tensile testing machines. Additionally, both methods struggle to accurately capture the moment of sliding. Utility Model Content

[0004] The purpose of this invention is to provide a static friction coefficient measuring device, which, as a highly sensitive test device for capturing the moment of sliding initiation, can improve the accuracy of static friction coefficient measurement.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is: a static friction coefficient measuring device, which includes a friction component, an electromagnetic balance component, an electromagnetic coil drive circuit, a pulse width modulation signal circuit, and a data processing component.

[0006] The friction assembly includes a sliding base plate and a slider. The slider, as the sample to be tested, is placed horizontally on the sliding base plate, and the combination of the slider and the sliding base plate is placed on the worktable.

[0007] The electromagnetic balancing assembly includes a support rod, a permanent magnet, a coil, a light-emitting diode, a light-shielding plate, and a photodiode. The upper end of the support rod passes through the center of the permanent magnet and is connected to the slider through a balancing mechanism. The lower end of the support rod is equipped with a coil, which is placed in an annular groove at the lower end of the permanent magnet. The bottom of the support rod is equipped with a light-shielding plate. A light-emitting diode is provided on one side of the light-shielding plate, and a photodiode is provided on the other side of the light-shielding plate. The photodiode is connected to the electromagnetic coil driving circuit through a photoelectric conversion circuit.

[0008] The electromagnetic coil driving circuit is used to apply current to the coil according to the current signal generated by the photoelectric conversion circuit;

[0009] The pulse width modulation (PWM) signal circuit is used to generate a PWM pulse signal corresponding to the current applied to the coil.

[0010] The data processing component is used to determine the force applied to the slider based on the pulse width modulation signal, and output the friction coefficient value after calculation in combination with the slider mass pre-input into the system.

[0011] Furthermore, the balancing mechanism includes a pulley, a counterweight, and a lever. The two ends of the lever are connected to the counterweight and a support rod, respectively. At the same time, the bottom end of the counterweight is connected to a metal wire, which is wrapped around the pulley and then connected to the slider.

[0012] Furthermore, the counterweight has the same mass as the combination of the support rod, coil, and light shield, so that the lever is initially in a balanced state.

[0013] Furthermore, the coil and the support rod are connected and fixed by a crossbeam, and one end of the support rod passing through the central hole of the permanent magnet is connected to one end of the lever, while the other end is connected to the light shield.

[0014] Furthermore, a gap is left between the coil and the annular groove of the permanent magnet, and a gap is left between the support rod and the central hole of the permanent magnet, so that the coil can move up and down freely in the annular groove of the permanent magnet under the drive of the support rod.

[0015] Furthermore, the electromagnetic coil drive circuit includes a PID controller and a transistor; the output terminal of the PID controller is connected to the base of the transistor, the collector of the transistor is connected to the voltage source VCC, the emitter of the transistor is connected to the first end of the coil and applies current to the first end of the coil, and the second end of the coil is connected to the floating potential node A in the pulse width modulation signal circuit.

[0016] Furthermore, the pulse width modulation (PWM) signal circuit includes a PWM signal generation circuit, a current charging and discharging circuit, and a controllable current source, with a floating potential node A provided between the current charging and discharging circuit and the controllable current source.

[0017] Furthermore, the data processing component includes a microprocessor, a recording and output system, and an operation panel.

[0018] The beneficial effects of this invention are: This device designs a brand-new method for detecting the static friction coefficient. By adopting an electromagnetic balance system, it can highly sensitively capture the moment when sliding begins, thus improving the accuracy of static friction coefficient measurement. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the static friction coefficient measuring device of this utility model.

[0020] Figure 2 This is a schematic diagram of the electromagnetic system structure of this utility model.

[0021] The following are labeled in the diagram: 1. Sliding base plate; 2. Slider; 3. Pulley; 4. Counterweight; 5. Lever; 6. Support rod; 7. Permanent magnet; 8. Coil; 9. Light-emitting diode; 10. Light-shielding plate; 11a and 11b, Photodiodes; 12. Photoelectric conversion circuit; 13. PID controller; 14. Transistor; 15. Current charging and discharging circuit; 16. Pulse width modulation signal generation circuit; 17. Controllable current source; 18. Microprocessor; 19. Recording and output system; 20. Operation panel; 21. Crossbeam. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0023] like Figure 1 and 2 As shown, a static friction coefficient measuring device can be divided into five systems, including a friction component (A), an electromagnetic balance component (B), an electromagnetic coil drive circuit (C), a pulse width modulation (PWM) signal circuit (D), and a data processing component (E). The friction component includes a sliding base plate 1 and a slider 2; the electromagnetic balance component includes a pulley 3, a counterweight 4, a lever 5, a support rod 6, a permanent magnet 7, a coil 8, a light-emitting diode 9, a light-shielding plate 10, photodiodes 11a and 11b, and a photoelectric conversion circuit 12; the electromagnetic coil drive circuit includes a PID controller 13 and a transistor 14; the PWM signal circuit includes a PWM signal generation circuit 16, a current charging and discharging circuit 15, and a controllable current source 17; and the data processing component includes a microprocessor 18, a recording and output system 19, and an operation panel 20.

[0024] In this embodiment, slider 2 is placed on sliding base plate 1, and the assembly of slider 2 and sliding base plate 1 is placed on the worktable. Slider 2 is connected to counterweight 4 by a metal wire through pulley 3. Counterweight 4 is also connected to one end of lever 5, and the other end of lever 5 is connected to support rod 6. The mass of the assembly of counterweight 4, support rod 6, coil 8, and light shield 10 is equal, so that the lever 5 is initially in a balanced state.

[0025] In this embodiment, the permanent magnet 7 has a through hole in its center, through which the support rod 6 passes and is connected to the lever 5 via a metal wire. The coil 8 is placed in the annular groove of the permanent magnet 7, with a certain gap between them to allow the coil 8 to move up and down without obstruction. The coil 8 is connected to and fixed to the support rod 6 via the crossbeam 21. The support rod 6 is made of a non-magnetic metal (such as copper, aluminum, etc.) and can move up and down in the through hole. During the up and down movement of the support rod 6, it moves the light-shielding plate 10 along with it. When the light-shielding plate moves up, the light emitted by the light-emitting diode 9 can be received by the photosensitive diode 11. The light-shielding plate 10 and the support rod 6 are connected together as a whole, and the movement of the light-shielding plate 10 can change the amount of light emitted by the light-emitting diode 9 received by the photosensitive diodes 11a and 11b.

[0026] In this embodiment, the current signals generated by photodiodes 11a and 11b after receiving light are converted into current by photoelectric conversion circuit 12 and PID controller 13. The output terminal of PID controller 13 is connected to the base of transistor 14, the collector of transistor 14 is connected to voltage source VCC, and the emitter of transistor 14 is connected to the first end of coil 8, applying current to the first end of coil 8. The second end of coil 8 is connected to floating potential node A. Pulse width modulation (PWM) signal generation circuit 16 is connected to floating potential node A and is used to generate PWM pulse signals corresponding to the current applied to the first end of coil 8. Microprocessor 18 is connected to PWM signal generation circuit 16 and is used to determine the force applied to the slider based on the pulse signal, and then calculate the friction coefficient value after performing calculations with the mass of slider 2 pre-input into the microprocessor system.

[0027] The working principle of this device is as follows: Before the assembly of slider 2 and sliding base plate 1 is moved, the light-blocking plate 10 is in a balanced position, blocking the light emitted by photodiode 9. Photodiodes 11a and 11b do not receive light, the photoelectric detection circuit outputs zero, and therefore the PID controller 13 outputs zero. At this time, transistor 14 is disconnected, the current I flowing through coil 8 is also zero, and thus the electromagnetic force generated by coil 8 is zero. After the assembly of slider 2 and sliding base plate 1 is displaced, the PID controller 13 receives the signal from the photoelectric detection circuit and outputs a corresponding voltage, thereby turning on transistor 14, supplying power to VCC, and thus applying current I to coil 8. The formula for calculating the current I applied to coil 8 is as follows:

[0028]

[0029] Among them, V CE It is the voltage between the collector and emitter of transistor 14, V. CC V is the voltage of the power supply VCC. A V is the voltage at floating potential node A, and R is the resistance of coil 8. Furthermore, V CEInfluenced by the output voltage of the PID controller 13, the PID controller 13 can change V CE The magnitude of the current I is adjusted, thereby adjusting the magnitude of the electromagnetic force generated by the coil 8. Furthermore, the pulse width modulation (PWM) signal generation circuit 16 is connected to the floating potential node A to generate a PWM signal corresponding to the current I. The microprocessor 18 can then determine the magnitude of the current I based on this PWM signal, and thus determine the magnitude of the electromagnetic force generated by the coil 8.

[0030] During the test, the sliding base plate 1 is pulled, which in turn moves the support rod 6 and the light-shielding plate 10 upwards via the slider 2. The photodiode receives the light signal, and a current I is applied to the coil 8, generating an electromagnetic force. When the force increases to the maximum static friction, the slider 3 begins to move relative to the sliding base plate 2, at which point the static friction transforms into sliding friction, and the force decreases rapidly. The assembly containing the support rod 6 then moves downwards, pulling the slider to its equilibrium position. At this point, the light-shielding plate 10 also returns to its equilibrium position, blocking the light emitted by the photodiode 9. The photodiodes 11a and 11b do not receive light, and the photoelectric detection circuit outputs zero. Consequently, the PID controller 13 also outputs zero, ending one test. The microprocessor system calculates the maximum force value recorded in one test against the pre-input mass of the slider 2 and outputs the coefficient of friction value.

[0031] Among them, static friction coefficient F is the tension force on the slider, generated by the coil, and N is the vertical force exerted by the slider on the sliding base plate, which can be obtained from the mass of the slider.

[0032] According to the electromagnetic force formula F = B × L × I × sinθ, where F is the tension generated by the coil, B is the magnetic induction intensity of the permanent magnetic field, L is the effective length of the coil (the conductor under force), I is the coil current, and θ is the angle between the current-carrying conductor and the magnetic field. Since the dimensions of the moving coil in the sensor are fixed, B and L do not change, and θ is 90°, so sinθ = 1. Therefore, the magnitude of F is directly related to I.

[0033] In addition, this device can also detect the coefficient of friction between thin film materials. Specifically, the thin film material is flatly adhered to the upper surface of the sliding base plate and the lower surface of the slider, and then the detection process described above is performed.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that the above embodiments do not limit the scope of protection of this utility model in any way, and all technical solutions obtained by equivalent substitution or other means fall within the scope of protection of this utility model. Parts not covered by this utility model are the same as or can be implemented using existing technology.

Claims

1. A device for measuring the static friction coefficient, characterized in that, Includes friction components, electromagnetic balance components, electromagnetic coil drive circuits, pulse width modulation signal circuits, and data processing components; The friction assembly includes a sliding base plate and a slider. The slider, as the sample to be tested, is placed horizontally on the sliding base plate, and the combination of the slider and the sliding base plate is placed on the worktable. The electromagnetic balancing assembly includes a support rod, a permanent magnet, a coil, a light-emitting diode, a light-shielding plate, and a photodiode. The upper end of the support rod passes through the center of the permanent magnet and is connected to the slider through a balancing mechanism. The lower end of the support rod is equipped with a coil, which is placed in an annular groove at the lower end of the permanent magnet. The bottom of the support rod is equipped with a light-shielding plate. A light-emitting diode is provided on one side of the light-shielding plate, and a photodiode is provided on the other side of the light-shielding plate. The photodiode is connected to the electromagnetic coil driving circuit through a photoelectric conversion circuit. The electromagnetic coil driving circuit is used to apply current to the coil according to the current signal generated by the photoelectric conversion circuit; The pulse width modulation (PWM) signal circuit is used to generate a PWM pulse signal corresponding to the current applied to the coil. The data processing component is used to determine the force applied to the slider based on the pulse width modulation signal, and output the friction coefficient value after calculation in combination with the slider mass pre-input into the system.

2. The static friction coefficient measuring device according to claim 1, characterized in that, The balancing mechanism includes a pulley, a counterweight, and a lever. The two ends of the lever are connected to the counterweight and a support rod, respectively. The bottom end of the counterweight is connected to a metal wire, which wraps around the pulley and connects to the slider.

3. The static friction coefficient measuring device according to claim 2, characterized in that, The counterweight has the same mass as the combination of the support rod, coil, and light shield, so that the lever is initially in a balanced state.

4. The static friction coefficient measuring device according to claim 1, characterized in that, The coil and the support rod are connected and fixed by a crossbeam. One end of the support rod, which passes through the central hole of the permanent magnet, is connected to one end of the lever, and the other end is connected to the light shield.

5. A static friction coefficient measuring device according to claim 1 or 4, characterized in that, A gap is left between the coil and the annular groove of the permanent magnet, and a gap is left between the support rod and the central hole of the permanent magnet. The coil moves up and down freely in the annular groove of the permanent magnet under the action of the support rod.

6. The static friction coefficient measuring device according to claim 1, characterized in that, The electromagnetic coil drive circuit includes a PID controller and a transistor; the output terminal of the PID controller is connected to the base of the transistor, the collector of the transistor is connected to the voltage source VCC, the emitter of the transistor is connected to the first end of the coil and applies current to the first end of the coil, and the second end of the coil is connected to the floating potential node A in the pulse width modulation signal circuit.

7. A static friction coefficient measuring device according to claim 1 or 6, characterized in that, The pulse width modulation (PWM) signal circuit includes a PWM signal generation circuit, a current charging and discharging circuit, and a controllable current source. A floating potential node A is provided between the current charging and discharging circuit and the controllable current source.

8. The static friction coefficient measuring device according to claim 1, characterized in that, The data processing components include a microprocessor, a recording and output system, and an operation panel.

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