CN109507106B - Snow friction coefficient measuring device and measuring method - Google Patents
Snow friction coefficient measuring device and measuring method Download PDFInfo
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- CN109507106B CN109507106B CN201811381099.9A CN201811381099A CN109507106B CN 109507106 B CN109507106 B CN 109507106B CN 201811381099 A CN201811381099 A CN 201811381099A CN 109507106 B CN109507106 B CN 109507106B
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- G01N19/02—Measuring coefficient of friction between materials
Abstract
The application relates to the technical field of snow friction coefficient measurement, in particular to a snow friction coefficient measuring device and a snow friction coefficient measuring method. The flywheel mechanism, the power starting mechanism and the support falling mechanism; the flywheel mechanism comprises a flywheel, a support shaft, a bearing seat and a rotating speed sensor, wherein the flywheel rotates by taking the support shaft as a rotating shaft; two ends of the supporting shaft are respectively loaded on the supporting falling mechanism through bearing seats; the rotating speed sensor is arranged at one end of the supporting shaft and used for detecting the rotating speed of the flywheel; the power starting mechanism is detachably connected with the supporting shaft and is used for driving the flywheel to rotate; the support falling mechanism can lift and is used for driving the flywheel mechanism to contact or separate from the snowfield. The snow friction coefficient measuring device solves the process linear acceleration at the friction coefficient, is the rotational acceleration, and simple structure satisfies portable requirement, has the characteristics of accurate control, and can adapt to the low-temperature environment of a ski field, and the whole measuring process is stable, and the measurement is convenient and accurate.
Description
Technical Field
The invention relates to the technical field of snow friction coefficient measurement, in particular to a snow friction coefficient measuring device and a measuring method for measuring a snow friction coefficient by applying the device.
Background
In all snowy athletic activities, there is friction between the athletic equipment and the surface of the snow. Just because of the presence of friction, various types of ski equipment, suitable technical actions and targeted assistance techniques are derived. Because snow sports fields are different and weather conditions are different, the snow surface friction coefficients of all positions of the fields of the same sports project are greatly different. Taking alpine skiing as an example, indexes such as the altitude, the snow density, the air temperature, the snow temperature and the like of a departure area, a middle area and a destination area are different, and the friction coefficient of the snow surface at each position is directly changed according to a certain uncertain rule. To allow athletes of different technical types to exert their own advantages, coaches and athletes must make equipment and technical adjustments based on snow surface friction. Snowboard selection, staged physical force distribution, control of over-bending speed, adjustment of gliding stance, selection of snowboard wax, and even more detailed adjustment sometimes in combination with changes in wind speed and terrain. These details are all factors to be considered in the pre-match alternative game scenario. It is seen that the snow surface friction coefficient plays a significant role in snow sports.
However, the snow surface friction coefficient measuring device in the prior art generally has the defects of inconvenient carrying, large influence by environmental factors or long testing time, can only be carried out in a laboratory, and is not suitable for direct field testing, so that the snow surface friction coefficient in an outdoor field cannot be timely and accurately tested, and further a plurality of athletes and coaches ignore the influence of the snow surface friction coefficient, and a competition scheme is formulated by means of past experience and a heart state which is not changeable, and optimization is not achieved.
Disclosure of Invention
The application aims to provide a snow friction coefficient measuring device and a measuring method for measuring a snow friction coefficient by applying the device, so as to solve the technical problem that in the prior art, snow friction coefficient measuring equipment is not suitable for outdoor field direct test, and the friction coefficient of the snow surface on an outdoor field cannot be directly measured.
The application provides a snow coefficient of friction measuring device includes: the flywheel mechanism, the power starting mechanism and the support falling mechanism;
the flywheel mechanism comprises a flywheel, a support shaft, a bearing seat and a rotating speed sensor, wherein the support shaft penetrates through the flywheel so that the flywheel can rotate by taking the support shaft as a rotating shaft; the supporting shaft is horizontally arranged, and two ends of the supporting shaft are respectively loaded on the supporting and dropping mechanism through the bearing seats; the rotating speed sensor is arranged at one end of the supporting shaft and used for detecting the rotating speed of the flywheel;
the power starting mechanism is detachably connected with the supporting shaft and is used for driving the flywheel to rotate;
the support falling mechanism can lift and is used for driving the flywheel mechanism to be in contact with or separated from the snowfield.
Further, the power starting mechanism comprises a motor, a motor supporting sliding table and a transmission pin;
the motor is positioned on the motor supporting sliding table, and an output shaft of the motor can be connected with the supporting shaft through the transmission pin and is used for driving the flywheel to rotate;
the motor support sliding table can drive along the extending direction of the support shaft, the motor is close to or far away from the flywheel mechanism, and the transmission pin is connected with or separated from the support shaft.
Furthermore, the supporting and dropping mechanism comprises a flywheel supporting sliding table, a flywheel supporting frame and a driving device;
the flywheel support frame is positioned on the flywheel support sliding table, and the driving device can drive the flywheel support frame to move up and down on the flywheel support sliding table along the vertical direction;
the bearing seat of the flywheel mechanism is carried on the flywheel support frame, and the flywheel support frame can drive the flywheel mechanism to move up and down.
Furthermore, the flywheel mechanism also comprises a linear guide rail and a sliding block;
the linear guide rail extends along the vertical direction, and the sliding block can slide on the linear guide rail; the bearing seat is fixedly connected with the sliding block and used for guiding the up-and-down movement of the flywheel.
Furthermore, the snow friction coefficient measuring device also comprises a frame;
the linear guide rail and the power starting mechanism are arranged on the rack.
Further, the snow friction coefficient measuring device further comprises a controller;
the rotation speed sensor transmits the acquired angular speed and angular acceleration signals in the rotation process of the flywheel to the controller, and the controller processes the angular speed and angular acceleration signals and transmits measured values to a computer terminal.
Further, the controller is connected with the power starting mechanism and the supporting falling mechanism respectively and used for controlling starting and stopping of the power starting mechanism and the supporting falling mechanism.
Further, the bearing is a ceramic bearing.
The application also provides a measuring method of the snow friction coefficient measuring device, which comprises the following steps:
step 100, placing a snow friction coefficient measuring device on a snow surface to be measured, adjusting the position of a flywheel support frame to enable a flywheel to be separated from the ground for a certain distance, adjusting the position of a motor support sliding table to enable a transmission pin at the output shaft end of a motor to be meshed with a support shaft of the flywheel, and preparing for starting;
200, switching on a power supply, starting the motor, accelerating the motor and driving the flywheel to rotate, detecting the rotating speed of the flywheel by a rotating speed sensor, and uploading a signal to a computer end through a controller;
step 300, when the motor is accelerated to a certain value, adjusting the position of the motor supporting sliding table to enable a transmission pin at the output shaft end of the motor to be separated from the supporting shaft of the flywheel;
step 400, adjusting the position of the flywheel support frame downwards to drive the flywheel to fall along the linear guide rail until the flywheel contacts with the detected snow surface, collecting the rotating speed value of the flywheel in the process, and calculating to obtain the angular acceleration alpha of the flywheel in the time period1；
Step 500, after the flywheel is contacted with the snow surface to be detected, the flywheel supporting frame continuously falls until the flywheel supporting frame is separated from a bearing seat of the flywheel, so that the gravity of a flywheel mechanism completely acts on the snow surface to be detected, after the flywheel supporting frame is contacted and rubbed, the rotating speed value of the flywheel in the process is collected, and the angular acceleration of the flywheel in the time period is calculated to be alpha2(ii) a Obtaining angular acceleration of flywheel as alpha ═α1-α2；
Step 600, measuring the mass m, the moment of inertia J and the diameter d of the flywheel mechanism according to the formula
And obtaining the friction coefficient of the detected snow surface.
Further, in step 300, after the motor is separated from the flywheel, the flywheel is operated for a certain time to stabilize the flywheel, and then the next step is performed.
Compared with the prior art, the invention has the beneficial effects that:
the application provides a snow coefficient of friction measuring device includes: the flywheel mechanism, the power starting mechanism and the support falling mechanism;
the flywheel mechanism comprises a flywheel, a support shaft, a bearing seat and a rotating speed sensor, wherein the support shaft penetrates through the flywheel so that the flywheel can rotate by taking the support shaft as a rotating shaft; the supporting shaft is horizontally arranged, and two ends of the supporting shaft are respectively loaded on the supporting and dropping mechanism through the bearing seats; the rotating speed sensor is arranged at one end of the supporting shaft and used for detecting the rotating speed of the flywheel so as to obtain the angular speed and the angular acceleration of the flywheel.
The power starting mechanism is used for providing rotating power for the flywheel to enable the flywheel to reach a certain initial rotating speed, so that the outer surface of the flywheel is rubbed with the measured snow surface, the friction torque is calculated by calculating the angular acceleration value of the rotating speed sensor after the contact friction, and the gravity of the part, namely the total gravity of the flywheel mechanism, is the positive pressure on the measured snow surface; and the power starting mechanism is detachably connected with the supporting shaft, and when the flywheel reaches a certain initial rotating speed, the power starting mechanism can be separated from the flywheel, so that the flywheel idles and is ready for later measurement.
The support falling mechanism can lift, and the flywheel mechanism is carried on the support falling mechanism, so that the flywheel mechanism can lift along with the support falling mechanism. Specifically, when the test is started, the support falling mechanism supports the flywheel mechanism to enable the flywheel mechanism to be separated from the snow, and at the moment, the power starting mechanism is started to enable the flywheel to obtain a certain rotating speed; after the flywheel rotates stably, the supporting falling mechanism descends to enable the flywheel to be in contact with the snow land; and then the supporting and falling mechanism descends again, the supporting and falling mechanism does not play a role in supporting the flywheel mechanism any more, and the gravity of the flywheel mechanism completely acts on the snowfield at the moment.
The snow friction coefficient measuring device changes linear acceleration into rotational acceleration in the friction coefficient solving process, has the characteristics of simple structure, meeting the portable requirement, having accurate control, being capable of adapting to the low-temperature environment of a ski field, having stable integral measuring process, having high measuring precision on variables such as gravity, rotational inertia, rotating speed, time and the like, and being convenient and accurate to measure.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic structural diagram of a snow friction coefficient measuring device according to an embodiment of the present invention;
FIG. 2 is a flywheel mechanical model of a flywheel mechanism provided by an embodiment of the invention;
FIG. 3 is a schematic diagram of a snow coefficient of friction measuring device provided by an embodiment of the present invention;
fig. 4 is a schematic connection diagram of system components of a control acquisition system according to an embodiment of the present invention;
fig. 5 is a flowchart illustrating an operation of the control acquisition system according to an embodiment of the present invention.
Reference numerals:
the device comprises a flywheel mechanism 1, a flywheel 11, a flywheel 12, a support shaft 13, a bearing seat 14, a rotating speed sensor 15, a linear guide rail 16, a sliding block 2, a power starting mechanism 21, a motor 22, a motor support sliding table 23, a transmission pin 3, a support falling mechanism 31, a flywheel support sliding table 32, a flywheel support frame and a rack 4.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention.
The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention.
All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
A snow friction coefficient measuring apparatus and a measuring method of measuring a snow friction coefficient using the same according to some embodiments of the present invention will be described below with reference to fig. 1 to 5.
Referring to fig. 1, the present application provides a snow friction coefficient measuring device, including: the device comprises a flywheel mechanism 1, a power starting mechanism 2 and a supporting falling mechanism 3;
the flywheel mechanism 1 comprises a flywheel 11, a support shaft 12, a bearing seat 13 and a rotating speed sensor 14, wherein the support shaft 12 penetrates through the flywheel 11, so that the flywheel 11 can rotate by taking the support shaft 12 as a rotating shaft; the supporting shaft 12 is horizontally arranged, and two ends of the supporting shaft 12 are respectively loaded on the supporting and dropping mechanism 3 through bearing seats 13; the rotation speed sensor 14 is provided at one end of the support shaft 12 and detects the rotation speed of the flywheel 11 to obtain the angular velocity and the angular acceleration of the flywheel 11.
The power starting mechanism 2 is used for providing rotary power for the flywheel 11 to enable the flywheel 11 to reach a certain initial rotating speed, so that the outer surface of the flywheel 11 is rubbed with the measured snow surface, the friction torque is calculated by calculating the angular acceleration value of the rotating speed sensor 14 after the contact friction, and the gravity of the part is the positive pressure on the measured snow surface; and the power starting mechanism 2 is detachably connected with the support shaft 12, when the flywheel 11 reaches a certain initial rotating speed, the power starting mechanism 2 can be separated from the flywheel 11, so that the flywheel 11 idles, and preparation is made for later measurement.
The support falling mechanism 3 can be lifted, and the flywheel mechanism 1 is mounted on the support falling mechanism 3, so that the flywheel mechanism 1 can be lifted along with the support falling mechanism 3. Specifically, when the test is started, the support falling mechanism 3 supports the flywheel mechanism 1 to separate the flywheel mechanism from the snow, and at the moment, the power starting mechanism 2 is started to enable the flywheel 11 to obtain a certain rotating speed; after the flywheel 11 rotates stably, the supporting falling mechanism 3 descends to enable the flywheel 11 to be in contact with the snow; and then the supporting and falling mechanism 3 descends again, the supporting and falling mechanism 3 does not play a role in supporting the flywheel mechanism 1 any more, and the gravity of the flywheel mechanism 1 completely acts on the snowfield.
The snow friction coefficient measuring device disclosed by the invention is based on the principle of a braking flywheel method, and the test process is as follows:the integral measuring device is fixed on the surface of the snow to be measured, a power source is used for giving an initial speed to the middle flywheel 11, after the initial speed is stable, the power source is removed, then the falling mechanism 3 is supported to drive the middle flywheel 11 to fall, the round surface of the flywheel 11 is in contact with the surface of the snow to be measured, and the rotating speed of the flywheel 11 at the moment is recorded as W by the rotating speed sensor 141Recording the rotating speed W of the flywheel 11 at the moment after T time after the flywheel 11 is in frictional contact with the detected snow surface2，
I.e. the acceleration a during this time period.
According to the classical mechanical tribology theory, the friction force is in direct proportion to the positive pressure on the friction pair, wherein the proportional parameter is the friction coefficient, and the friction coefficient calculation formula is as follows:
f-frictional force (N);
f-positive pressure (N);
mu-coefficient of friction.
The mechanical model of the flywheel of the snow friction coefficient measuring device of the present application is shown in fig. 2, and the friction coefficient μ can be calculated by the following formula
By
M＝Jα
To obtain
And, N ═ mg
To obtain
Wherein μ — coefficient of friction;
n is positive pressure;
f-friction;
d-flywheel 11 diameter;
m-friction torque;
j-moment of inertia of the flywheel 11;
α — flywheel 11 angular velocity;
m is the total mass of the flywheel mechanism 1;
t-flywheel 11 rotation time;
wherein d, J, m are constants, and W is1、W2The speed can be measured by a rotating speed sensor of the snow friction coefficient measuring device, and T is the rotating time of the flywheel.
The snow friction coefficient measuring device changes linear acceleration into rotational acceleration in the friction coefficient solving process, has the characteristics of simple structure, meeting the portable requirement, having accurate control, being capable of adapting to the low-temperature environment of a ski field, having stable integral measuring process, having high measuring precision on variables such as gravity, rotational inertia, rotating speed, time and the like, and being convenient and accurate to measure. The method is particularly suitable for measuring the snow friction coefficient in the alpine skiing process, determining the relation between the friction coefficient and the sliding speed of the athlete, and making a targeted response scheme for selecting a proper snowboard, a proper waxing scheme and the posture in the skiing process for a coach and the athlete.
Preferably, the flywheel 11 is in a spoke type structure, the outer surface of the flywheel can be waxed, and the friction force between the flywheel 11 and a snow surface is reduced, so that the measurement is more accurate.
Preferably, the speed sensor 14 is an ohm dragon incremental photoelectric encoder, the model number of which is E6H-CWZ3E, the single-turn pulse value of which is 1024 pulses, and the real-time speed value of the flywheel 11 can be obtained, and the angular acceleration is obtained through angular velocity differentiation, so that the friction torque is solved.
Referring to fig. 1, in one embodiment of the present application, preferably, the power starting mechanism 2 includes a motor 21, a motor support slide 22, and a driving pin 23;
the motor 21 is positioned on the motor support sliding table 22, and an output shaft of the motor 21 can be connected with the support shaft 12 through a transmission pin 23 and is used for driving the flywheel 11 to rotate;
the motor support sliding table 22 can drive the motor 21 to be close to or far away from the flywheel mechanism 1 along the extending direction of the support shaft 12, so that the transmission pin 23 is connected with or separated from the support shaft 12.
In this embodiment, the power starting mechanism 2 includes a motor 21, a motor support sliding table 22 and a transmission pin 23, the motor 21 is connected with one end of the support shaft 12 through the transmission pin 23, so that the flywheel 11 is driven to rotate by the motor 21; the driving pin 23 of the motor 21 is detachably connected with the support shaft 12, the motor 21 is fixed on the motor support sliding table 22, a slide way is arranged below the motor support sliding table 22, and the motor support sliding table 22 can slide along the slide way in a direction close to or far away from the flywheel mechanism 1, so that the driving pin 23 of the motor 21 is driven to be meshed with or separated from the driving pin 23 of the support shaft 12 of the flywheel 11; therefore, when the motor 21 approaches and is connected to the flywheel 11, the starter motor 21 can drive the flywheel 11 to rotate, so that the flywheel 11 reaches a certain rotation speed w; the motor support slide 22 then separates the motor 21 from the flywheel 11, i.e., removes the power source, and idles the flywheel 11 in preparation for later measurement.
Preferably, the sliding direction of the motor support slide table 22 is the same as the extending direction of the support shaft 12, so that the driving pin 23 of the motor 21 is more easily engaged with or disengaged from the support shaft 12. Further preferably, the motor support slide 22 is an electric slide.
Further preferably, the motor support slide 22 is a stepping motor 21 plus a ball screw linear guide slide module.
Preferably, the motor 21 is a 57HB250-5B closed-loop stepping motor 21 because the device has high requirement on the accurate index of the rotating speed.
Referring to fig. 1, in one embodiment of the present application, it is preferable that the support drop mechanism 3 includes a flywheel support slide table 31, a flywheel support frame 32, and a driving device;
the flywheel support sliding table 31 extends in the vertical direction, the flywheel support frame 32 is positioned on the flywheel support sliding table 31, and the driving device can drive the flywheel support frame 32 to move up and down along the flywheel support sliding table 31;
the bearing seat 13 of the flywheel mechanism 1 is carried on the flywheel support frame 32, and the flywheel support frame 32 can drive the flywheel mechanism 1 to move up and down.
In this embodiment, the support drop mechanism 3 includes a flywheel support sliding table 31, a flywheel support frame 32 and a driving device, and the driving device can drive the flywheel support sliding table 31 to slide on the flywheel support frame 32 to realize the up-and-down lifting of the flywheel support sliding table 31. The bearing seat 13 of the flywheel mechanism 1 is arranged on the sliding block 16, and when the flywheel mechanism 1 is contacted with the detected snow surface from a certain distance away from the detected snow surface, the sliding block 16 plays a supporting role for the flywheel mechanism 1; when the slide block 16 continues to move downwards to be separated from the flywheel mechanism 1, the support falling mechanism 3 does not support the flywheel mechanism 1 any more, and the gravity of the flywheel mechanism 1 completely acts on the detected snow surface.
It should be noted that the driving device may be a motor 21, an air cylinder, a hydraulic drive, or the like, and is preferably driven by the motor 21, in which case the flywheel support sliding table 31 is an electric sliding table.
Referring to fig. 1, in one embodiment of the present application, the freewheel mechanism 1 preferably further includes a linear guide 15 and a slider 16;
the linear guide 15 extends in the vertical direction, and the slider 16 can slide on the linear guide 15; the bearing block 13 is fixedly connected with the slider 16 for guiding the up-and-down movement of the flywheel 11.
In this embodiment, in order to guarantee the stability of flywheel mechanism 1 in the process of falling, flywheel mechanism 1 still includes linear guide 15 and slider 16, and linear guide 15 is located one side of flywheel 11, and linear guide 15 extends along vertical direction, and slider 16 slides and sets up on linear guide 15, and bearing frame 13 and slider 16 fixed connection, therefore flywheel 11 can slide along linear guide 15 in the process of falling for the process of falling of flywheel mechanism 1 is more stable.
Referring to fig. 1, in one embodiment of the present application, it is preferable that the snow friction coefficient measuring apparatus further includes a frame 4;
the linear guide rail 15 and the power starting mechanism 2 are both arranged on the frame 4.
In this embodiment, in order to ensure the stability of the whole device, the snow friction coefficient measuring device of the present application further includes a frame 4, and the linear guide 15 and the power starting mechanism 2 are both disposed on the frame 4, and play a role of stably supporting the whole device.
In one embodiment of the present application, preferably, the snow friction coefficient measuring device further comprises a controller;
the rotational speed sensor 14 transmits the collected angular speed and angular acceleration signals during the rotation of the flywheel 11 to the controller, and the controller processes the angular speed and angular acceleration signals and transmits the measured values to the computer terminal.
In this embodiment, the snow friction coefficient measuring device further includes a controller, and the controller can receive the angular velocity and angular acceleration signals acquired by the rotation speed sensor 14 during the rotation of the flywheel 11, and transmit the signals to a computer terminal for data processing, so as to obtain the friction coefficient μ to be measured.
Preferably, the controller is an AVR singlechip.
It should be noted that, referring to fig. 3, the snow friction coefficient measuring device of the present application includes a friction coefficient measuring portion and a signal collecting and processing portion, where the friction coefficient measuring portion includes a flywheel mechanism 1, a power starting mechanism 2 and a supporting and dropping mechanism 3, a motor 21 of the power starting mechanism 2 transmits power to a flywheel 11 in the flywheel mechanism 1 through a transmission pin 23, so that the flywheel 11 reaches a certain rotation speed, a sliding table of the power starting mechanism 2 drives the motor 21 to disengage from transmission, at this time, a flywheel supporting frame 32 of the supporting and dropping mechanism 3 supports the flywheel mechanism 1 to drop to a snow surface to be measured, so that an outer surface of the flywheel 11 contacts and rubs with the snow surface to be measured, an acceleration angle value of the rotation speed of the flywheel 11 is collected through a rotation speed sensor 14, and a friction force between the flywheel 11 and the snow surface to be measured can be solved through a formula, so as to obtain.
The signal acquisition and processing part comprises a power supply module, a sensor signal acquisition module, a wireless serial port module and a computer, wherein the power supply module adopts a direct current 24V power supply to supply power for the motor 21 and each electric sliding table, and converts the power into direct current 5V power through the voltage stabilizer to supply power for the sensor signal acquisition module. The sensor signal acquisition module comprises a rotating speed sensor 14 and an AVR single chip microcomputer, and the wireless serial port module transmits the measured value of the rotating speed sensor 14 to the computer for processing.
In one embodiment of the present application, the controller is preferably further connected to the power starting mechanism 2 and the supporting and dropping mechanism 3 respectively, for controlling the start and stop of the power starting mechanism 2 and the supporting and dropping mechanism 3.
In this embodiment, the controller is further connected with the power starting mechanism 2 and the supporting falling mechanism 3 respectively, and the controller can control the starting and stopping of the power starting mechanism 2 and the supporting falling mechanism 3, so that the automation of the whole measuring process is realized.
In one embodiment of the present application, preferably, the bearing is a ceramic bearing.
In the embodiment, the bearing is selected as a ceramic bearing, and the ceramic bearing has the advantages of small friction coefficient, wear resistance, small thermal expansion loss coefficient and low sensitivity to temperature gradient; the ceramic bearing has low density, oil-free self-lubricating property, adaptability to low-temperature environment and suitability for outdoor snowfield measurement; in addition, full ceramic bearing uses the ceramic race, and is lighter in the weight, and the rotational friction resistance is littleer, is applicable to the operating mode of high rotational speed, low load for the measuring device of this application measures more accurately.
The application also provides a measuring method of the snow friction coefficient measuring device, which comprises the following steps:
step 100, placing the snow friction coefficient measuring device on a snow surface to be measured, carrying out system initialization, adjusting the position of a flywheel support frame 32 to enable a flywheel 11 to be separated from the ground by 10mm, adjusting the position of a motor support sliding table 22 to enable a transmission pin 23 at the output shaft end of a motor 21 to be meshed with a support shaft 12 of the flywheel 11, and preparing for starting;
200, switching on a 24v direct-current power supply, starting a motor 21, accelerating the motor 21 and driving a flywheel 11 to rotate, detecting the rotating speed of the flywheel 11 by a rotating speed sensor 14, recording the acquisition value of an encoder by a single chip microcomputer and uploading the acquisition data to a computer terminal through a wireless module;
step 300, when the motor 21 accelerates to 160rad/s, adjusting the position of the motor support sliding table 22 to separate the transmission pin 23 at the output shaft end of the motor 21 from the support shaft 12 of the flywheel 11;
step 400, adjusting the position of the flywheel support frame 32 downwards to drive the flywheel 11 to fall along the linear guide rail 15, so that the flywheel 11 slowly falls on the detected snow surface until the flywheel 11 is in contact with the detected snow surface, acquiring the rotating speed value in the process by the encoder, and calculating the angular acceleration alpha in the time period1Namely, the angular velocity attenuation of the flywheel 11 caused by the inherent friction of the system in the suspended state;
step 500, after the flywheel 11 contacts with the detected snow surface, the flywheel support frame 32 continues to fall until the flywheel support frame is separated from the bearing seat 13 of the flywheel 11, so that the gravity of the flywheel mechanism 1 completely acts on the detected snow surface, after the contact friction, the rotating speed value of the flywheel 11 in the process is collected, and the angular acceleration of the flywheel 11 in the time period is calculated to be alpha2，α2Acceleration due to friction of contacting accumulated snow; the angular acceleration of the flywheel 11 is obtained as α ═ α1-α2Namely subtracting the error caused by the inherent friction of the system from the acceleration caused by the friction of contacting the accumulated snow;
step 600, measuring the mass m of the flywheel mechanism 1, the moment of inertia J of the flywheel 11 and the diameter d of the flywheel 11 according to the formula
And obtaining the friction coefficient of the detected snow surface.
In step 400 and step 500, the angular acceleration is α1And alpha2The angular acceleration is obtained by acquiring the real-time rotating speed value in the corresponding test process and then differentiating the angular velocity.
In one embodiment of the present application, it is preferable that in step 300, after the motor 21 is disengaged from the flywheel 11, the flywheel 11 is operated for 5s to stabilize the flywheel 11, and then the next step is performed to ensure the accuracy of the measurement.
In addition, referring to fig. 4, the present application also provides a control acquisition system of the snow friction coefficient measuring device, which mainly comprises the following parts: (1) arduino Mega 2560; (2) E6H-CWZ3E encoder; (3) APC220 wireless serial port; (4) lcd128 × 64; (5) a stepper motor 21 controller; (6) an electric slipway dc motor 21; (7) an FC054 relay; (8) LM2596685 adjustable voltage reduction module. The system is powered by a 24V direct-current power supply, adopts Arduino Mega2560 as a control board, controls all parts to move in sequence and collect data through an A/D port, transmits the data to a computer through a wireless serial port, and processes the data to calculate the friction coefficient.
Specifically, referring to fig. 4, the control acquisition process includes the following steps:
s1, initializing the screen to be the subsequent display work basis; the LCD128 x 64 screen is connected to the control panel in series through the SPI bus, and the screen is controlled and displayed through a control panel library function LCD12864RSPI.h;
s2: setting the baud rate to be 25600, sending a character 'TEST' to the control panel by the computer through the wireless serial port, if the control panel returns to 'TEST', the wireless module is correctly transmitted, and otherwise, performing S3;
s3: rechecking the wiring and running conditions of the wireless serial port module, returning to S2, and checking the transmission correctness;
s4: the wireless outlet transmission is normal;
s5: the motor 21 of the flywheel 11 starts to work; the maximum speed of skiing is about 20m/s, the radius of the flywheel 11 is 125mm, the maximum angular speed is about 20/0.125-160 rad/s-1527.88 rpm <3000rpm (the limit speed of the motor 21), the controller of the stepping motor 21 of the flywheel 11 divides 400 steps/circle, and the required pulse frequency is 400 x 160/2 pi-10185 Hz. The square wave with adjustable frequency and 50% duty ratio is output by the tone function of the control board to realize the input of the controller of the stepping motor 21. In order to prevent the motor 21 from being impacted, slow acceleration is selected, the frequency is set to change according to the sin function by using the idea that the sin function is gradually increased at 0-90 degrees and gradually decreased at 90-180 degrees, so that the acceleration of the flywheel 11 and the deceleration and stop of the motor 21 are realized;
s6: the E6H-CWZ3E encoder outputs 1024 pulses per revolution, and the control board is used for setting an interrupt to count the number of encoder pulses. Looking up a control panel parameter interrupt pin 0 (digital pin 2) to trigger interrupt, setting an interrupt mode to be rising edge trigger, and setting a counting function counter to count encoder pulses after the interrupt trigger;
s7: counting the encoder pulses, calculating time by using a micro function carried by the control board, and calculating the time T of the fixed pulse number C to obtain the angular speed w of the flywheel 11 (C/1024 x 2 pi); in order to ensure the uniformity of data of each angular velocity section when the angular velocity is acquired, the C value is a variable and is reduced along with the reduction of the angular velocity; the current recorded angular velocity is the angular velocity value after the system is accelerated by the motor 21 without contacting the snow surface;
s8: the wireless serial port sends the angular velocity value to a computer;
s9: s8 is carried out, and the current angular velocity value is displayed every 1 second and is displayed visually;
s10: the motor 21 and the sliding table motor 21 operate to separate the motor 21 of the flywheel 11 from the flywheel 11, so that the flywheel 11 rotates. At this time, an angular velocity value of 5s is recorded, and from this angular velocity value of 5s, a deceleration value of the system itself is obtained. After 5s, the lifting sliding table direct current motor 21 is controlled by a relay to start working, the flywheel 11 descends along with the lifting sliding table, then the flywheel 11 contacts the snow surface to start deceleration data acquisition, the lifting sliding table continuously descends to enable the flywheel mechanism 1 to be separated from the sliding table, and at the moment, the flywheel mechanism 1 is completely supported by the snow surface;
s11: the speed reduction angular speed value of the flywheel 11 is transmitted through a wireless serial port and recorded in a datafile txt file, so that subsequent data processing is facilitated;
s12: the angular velocity of the flywheel 11 gradually decreases due to friction until it stops; returning all the parts and finishing the collection; s13: the deceleration of the system can be obtained from the angular velocity value acquired in S10, the deceleration of the system after snow surface friction can be obtained from the angular velocity value acquired in S11, and the deceleration of the system after snow surface friction can be obtained by subtracting the former from the latter; according to the rigid body dead axle rotation rule, the friction moment M is J alpha,
mu N, where α is the angular acceleration, J is the moment of inertia of the rotating part of the system about the axis of the supporting shaft, f is the snow surface friction, d is the flywheel diameter, and N is the flywheel mechanism 1Gravity.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A snow friction coefficient measuring device, characterized by comprising: the flywheel mechanism, the power starting mechanism and the support falling mechanism;
the flywheel mechanism comprises a flywheel, a support shaft, a bearing seat and a rotating speed sensor, wherein the support shaft penetrates through the flywheel so that the flywheel can rotate by taking the support shaft as a rotating shaft; the supporting shaft is horizontally arranged, and two ends of the supporting shaft are respectively loaded on the supporting and dropping mechanism through the bearing seats; the rotating speed sensor is arranged at one end of the supporting shaft and used for detecting the rotating speed of the flywheel;
the power starting mechanism is detachably connected with the supporting shaft and is used for driving the flywheel to rotate;
the support falling mechanism can lift and is used for driving the flywheel mechanism to be in contact with or separated from the snow field;
the power starting mechanism comprises a motor, a motor supporting sliding table and a transmission pin;
the motor is positioned on the motor supporting sliding table, and an output shaft of the motor can be connected with the supporting shaft through the transmission pin and is used for driving the flywheel to rotate;
the motor support sliding table is provided with a slide way below, and can be driven by the slide way to enable the motor to be close to or far away from the flywheel mechanism, so that the transmission pin is connected with or separated from the support shaft.
2. The snow friction coefficient measuring device according to claim 1, wherein the support drop mechanism includes a flywheel support slide, a flywheel support frame, and a drive device;
the flywheel support frame is positioned on the flywheel support sliding table, and the driving device can drive the flywheel support frame to move up and down on the flywheel support sliding table along the vertical direction;
the bearing seat of the flywheel mechanism is carried on the flywheel support frame, and the flywheel support frame can drive the flywheel mechanism to move up and down.
3. The snow friction coefficient measuring device of claim 1, wherein the freewheel mechanism further comprises a linear guide and a slider;
the linear guide rail extends along the vertical direction, and the sliding block can slide on the linear guide rail; the bearing seat is fixedly connected with the sliding block and used for guiding the up-and-down movement of the flywheel.
4. The snow friction coefficient measuring device according to claim 3, further comprising a frame;
the linear guide rail and the power starting mechanism are arranged on the rack.
5. The snow friction coefficient measuring device according to claim 1, further comprising a controller;
the rotation speed sensor transmits the acquired angular speed and angular acceleration signals in the rotation process of the flywheel to the controller, and the controller processes the angular speed and angular acceleration signals and transmits measured values to a computer terminal.
6. The snow friction coefficient measuring device of claim 5, wherein the controller is further connected to the power starting mechanism and the support drop mechanism, respectively, for controlling the start and stop of the power starting mechanism and the support drop mechanism.
7. The snow friction coefficient measuring device of claim 1, wherein the bearing is a ceramic bearing.
8. A measuring method of a snow friction coefficient measuring device is characterized by comprising the following steps:
step 100, placing a snow friction coefficient measuring device on a snow surface to be measured, adjusting the position of a flywheel support frame to enable a flywheel to be separated from the ground for a certain distance, adjusting the position of a motor support sliding table to enable a transmission pin at the output shaft end of a motor to be meshed with a support shaft of the flywheel, and preparing for starting;
200, switching on a power supply, starting the motor, accelerating the motor and driving the flywheel to rotate, detecting the rotating speed of the flywheel by a rotating speed sensor, and uploading a signal to a computer end through a controller;
step 300, when the motor is accelerated to a certain value, adjusting the position of the motor supporting sliding table to enable a transmission pin at the output shaft end of the motor to be separated from the supporting shaft of the flywheel;
step 400, adjusting the position of the flywheel support frame downwards to drive the flywheel to fall along the linear guide rail until the flywheel contacts with the detected snow surface, collecting the rotating speed value of the flywheel in the process, and calculating to obtain the angular acceleration alpha of the flywheel in the time period1；
Step 500, after the flywheel is contacted with the snow surface to be detected, the flywheel supporting frame continuously falls until the flywheel supporting frame is separated from a bearing seat of the flywheel, so that the gravity of a flywheel mechanism completely acts on the snow surface to be detected, after the flywheel supporting frame is contacted and rubbed, the rotating speed value of the flywheel in the process is collected, and the angular acceleration of the flywheel in the time period is calculated to be alpha2(ii) a Obtaining angular acceleration of flywheel as alpha ═ alpha1-α2；
Step 600, measuring the mass m, the moment of inertia J and the diameter d of the flywheel mechanism according to the formula
And obtaining the friction coefficient of the detected snow surface.
9. The method of measuring a snow friction coefficient measuring device according to claim 8, wherein in step 300, after the motor is separated from the flywheel, the flywheel is operated for a certain time to stabilize the flywheel, and then the next step is performed.
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| CN109799187B (en) * | 2019-03-26 | 2021-06-22 | 河北科技大学 | Sliding friction coefficient testing device and testing method |
| CN110231284B (en) * | 2019-07-16 | 2024-01-30 | 上海宝冶集团南京建筑有限公司 | Rigidity friction coefficient measuring device |
| CN113051994B (en) * | 2020-11-18 | 2021-12-17 | 庄景江 | Real-time lifting system of grip ability based on environmental monitoring |
| CN112683673B (en) * | 2020-12-21 | 2024-03-19 | 哈尔滨商业大学 | Snow-removing rolling brush mechanical property test experiment table and test method |
| CN112663550B (en) * | 2021-01-14 | 2022-11-08 | 江苏坤典交通建设工程有限公司 | Laying road icing detection knockout device capable of being adjusted in self-adaption mode |
| DE102021117038B3 (en) | 2021-07-01 | 2022-09-15 | Hochschule Kaiserslautern | Determination of friction between a material and a snow or ice surface |
| CN113624676B (en) * | 2021-09-01 | 2022-05-24 | 东北大学 | Portable intelligent robot for automatically measuring snow surface friction coefficient |
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| US4594878A (en) * | 1983-06-24 | 1986-06-17 | Nippo Sangyo Co. Ltd. | Dynamic friction coefficient measuring apparatus |
| CN1325024A (en) * | 2000-05-19 | 2001-12-05 | 大和建工株式会社 | Kinetic-friction coefficient measuring device |
| JP3940613B2 (en) * | 2002-02-12 | 2007-07-04 | ヒノデホールディングス株式会社 | Dynamic friction coefficient measuring device |
| JP4771175B2 (en) * | 2007-06-18 | 2011-09-14 | 横浜ゴム株式会社 | Method and apparatus for measuring sliding friction force of tire |
| CN202372437U (en) * | 2011-11-02 | 2012-08-08 | 彭宏志 | Road friction coefficient measurement device |
| CN207051167U (en) * | 2017-06-26 | 2018-02-27 | 重庆能源职业学院 | Road friction coefficient test device |
| CN107505259B (en) * | 2017-08-18 | 2019-11-01 | 黑龙江省木材科学研究所 | A kind of rotary skin-friction coefficient test macro and test method |
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