CZ2021106A3 - Method of non-contact measurement of tyre tread deformation and the equipment for this - Google Patents

Abstract

The method of non-contact measurement of tire tread deformation and the device for performing this method enables non-contact measurement of tire tread deformation in both static and dynamic mode. The main components of the device are a line laser (2) and a scanning camera with optics (12), which can form one functional unit, as well as two sensors (4,5), which determine the angular rotation and rotation speed of the complete wheel. Thanks to wireless technologies, the device allows the measured data to be transmitted wirelessly to the evaluation device, which evaluates the real deformation of the pattern based on them. The device does not require the presence of contact sensors located directly on the tire casing and measures with an accuracy of tenths of a millimeter.

Description

Method for non-contact measurement of tire tread deformation and equipment for performing this method

Field of technology

The invention relates to a special measuring technique for the rubber industry. The designed device allows non-contact measurement of tire tread deformations in both static and dynamic mode and thus provides valuable data for assessment and modification of its design. This diagnosis is non-contact and is performed in online mode.

Current state of the art

From the point of view of current tire manufacturers, the interaction between the tire and the road is decisive for determining the dynamic behavior of the road vehicle. Thus, the contact forces of the road surface and tires are key variables in the design of traction control, braking and vehicle stability systems. Traditionally, the contact forces of the road surface and tires are indirectly estimated from vehicle dynamics measurements (chassis acceleration, yaw rate, suspension deflection, etc.).

The emergence of the concept of the so-called "intelligent tire" (a tire with built-in sensors and the ability to digitally process data) basically enables a more accurate estimation of the contact forces between the vehicle and the road surface. Since this technology is currently not fully developed and therefore common, its main problem is the selection of suitable sensors for estimating the contact force between the vehicle and the road surface.

The methods of diagnosing tire contact with the road surface are currently mostly based on the use of contact sensors. The use of optical non-contact methods is not frequent because the system of their application is too complicated.

The article Savaresi, S., M et al. is known from the non-patent literature: Design and testing of an innovative measurement device for tire-road contact forces, IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY Volume: 16 Issue: 4 (2008) Pages: 769- 780, which uses a wheel encoder and an accelerometer located directly in the tire. The acceleration measurement is then transmitted via a wireless channel. The key innovative concept of this solution is to use the phase shift between the wheel encoder. a. impulse signals provided by sensors'

Another article from this area is presented by the collective Cheli, F et al.: Design and testing of cm innovative measurement device for tire-road contact forces, MECHANICAL SYSTEMS AND SIGNAL PROCESSING Volume: 25 Issue: 6 (2011) Pages: 1956, when working the principle of the tire-road surface contact measuring device is based on the measurement of three deformations of the wheel rim using strain gauges.

Attention to this issue is also given in the article by Erdogan, G et al.: Estimation of Tire Road Friction Coefficient Using a Novel Wireless Piezoelectric Tire Sensor, IEEE SENSORS JOURNAL Volume: 11 Issue: 2 (2011) Pages: 267-279, where the authors deal with sensing tire-road surface contact using a wireless piezoelectric sensor.

The issue is also described through the article Yi, J..G. et al.: A smart tire system for tire/road friction estimation, PROCEEDINGS OF THE ASME DYNAMIC St S I EMS AND CONTROL CONFERENCE 2008, PTS A AND B (2009) Pages: 847-854, where the development of the tire deformation sensing system is described, which can provide important information for tire/road surface interaction estimation with a focus on mobile robots and vehicles. The polyvinyl difluoride (PVDF) based sensor is designed and manufactured as such. to fit the inner surface of the tread and is designed to measure the deformation of the rubber tread.

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In the study Matsuzaki, R. et al.: Rubber-based strain sensor fabricated using photolithography for intelligent tires SENSORS AND ACTUATORS A-PHYSICAL Volume: 148 Issue: 1 (2008) Pages (9-13), where a new type of sensor based on rubber, which is made using fbtolithography. The rubber base has the same mechanical properties as the tire surface: the sensor therefore does not interfere with the deformation of the tire and can precisely monitor its behavior. Thus, this study describes in detail the design and fabrication of the rubber sensor.

Car manufacturers can assess a tire's texture by listening to the synthesized sound that the tire would emit when rolling on a certain type of road surface, as shown in the Ishihama study. M. et al.: Tire sound quality evaluation tool using sound synthesis with physical modeling. PROCEEDINGS OF THE ASME INTERNATIONAL MECHANIC-LA ENGINEERING CONGRESS AND EXPOSITION, VOL 3: DESIGN AND MANUFACTURING (2007) Pages 527-533

The study below designs and experimentally investigates a new wireless strain measurement system using the change in electrical capacitance of steel wire reinforced tires. A small CR oscillating circuit is built into the tire. Thus, the deformation of the tire causes a change in the capacity of the tire, which includes steel wire and rubber. These capacitance changes, which in turn change the oscillating frequency of the oscillating circuit, are described in the article by Matsuzaki, R., et al: .: Wireless strain monitoring of tires using electrical capacitance changes with an oscillating circuit, SENSORS AND ACTUATORS A-PHYSICAL Volume: 119 Issue: 2 (2005) Pages: 323-331.

In an article by Moon. K..S a koiaTire tread deformation sensor and energy harvester development for Smart Tire applications, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2007, Pts 1 and 2 Book Series: PROCEEDINGS OF THE SOCIETY 'OF PHOTO-OPHCAL INSTRUMENTATION ENGINEERS (SPIE) Volume: 6529 (2007) Pages: U204-U215 the development of a tire tread deformation sensor and energy harvester for real-time tire monitoring and control is presented. The polyvinyl difluoride (PVDF) microsensor is designed and manufactured to fit inside the tire tread and measure tread deformation.

The results of the vehicle test and laboratory experiments allow a detailed view of the basic friction processes during braking on dry roads. The high shear forces that occur in an emergency braking situation create a typical pattern of deformation of the rubber blocks in the tire tread, which leads to significant geometric changes of the contact area parallel to the tread under free rolling conditions, which is discussed in the article by the author Kendzíor, N. akol: On the dynamics of tire/road contact and the relevance tor controlled braking, TIRE - CHASSIS- ROADS Book Senes: VD1BERICHTE Volume: 1791 (2003) Pages: 71.

Acoustic measurements presented in Dona van, P and kok: Tire Noise Generation and Propagation over Porous and Nonparous Asphalt Pavements. TRANSPORTATION RESEARCH RECORD Issue: 2233 (2011) Pages: 135 was conducted on several asphalt test tracks at the National Center tor Asphalt Technology (NCAT) test track. The measurement results also showed that single-layer porous pavements were particularly effective in reducing road noise source strength for frequencies above 1250 Hz for 18 to 33 mm thick designs. For thicker two-layer porous paving, the source power reduction was extended up to 630 Hz. Porous pavements have also been found to be effective in reducing the strength of the road-tire interaction source by reducing some of the tire noise mechanisms and reducing the source's acoustic power level through local sound absorption.

The paper by Kindt, P., et al: Measurement and analysis of rolling tire vibrations, OPTICS AND LASERS IN ENGINEERING Volume: 47 Issue: 3-4 Special Issue: SI (2009) Pages: 443453. deals with the measurement and analysis of tire vibrations in due to road surface impact excitations such as paved roads, intersections between concrete road surfaces.

-2CZ 2021 - 106 A3 level crossings. Vibrations of the tire surface due to road excitation cause noise radiation in the frequency range usually below 500 Hz. Measurement of tire vibrations with a laser doppler vibrometer is carried out online.

Article by Horvath, P et al. .Measurement of deformation by means of correlation of speckle fields, EXPERIMENTAL MECHANICS Volume: 46 Issue: 6(2006) Pages: 713-723, then contains a description of non-contact measurement of deformation of an object by means of correlation of speckle fields. This optical method uses the statistical properties of speckle patterns to detect the components of the small deformation tensor of the elementary region of the surface of the investigated object.

From the patent literature, a solution to an originally European patent is known, which is validated for the Czech Republic as PV 2007-18961, entitled Device and method for detecting the shape of a tire related to the measurement of the tire profile, it measures their external profile and does not allow the measurement of tire deformation arising from the contact of the tire with the road . This solution makes it possible to measure the dimensions of a rotating tire in three directions, but without contact with the real road.

Another solution included in the patent literature is IP 2007010405A Method and device for measuring of dynamic landing shape of tire ”, here a tire monitor is placed in the wheel arch and configured to project a beam(s of laser) onto. tire, changes the reflection of the beam(s). The processors are configured like this. to create a two-dimensional (2D) profile of the tire based on the reflections, compare the depths of the created profile with the depths of the pre-stressed profile and assess tire wear based on the comparison. The processors are set to determine the ride height of the vehicle based on the reflections. The processors are also configured to check the match against the preset profile before making the comparison and can further determine the match by comparing the width(s) of the built-in profile to the width(s) of the pre-stressed profiles. It is a laboratory device that contains a device for emitting rays on the tire pattern, it has a database of preset tire patterns. The device is not intended for measuring changes in tire tread when in contact with the road.

The above-mentioned devices and methods fall within the field of interference methods, they are laboratory devices and these devices mostly require the application of touch sensors, which can be a certain disadvantage from the point of view of practical use. The measurement is usually carried out by means of a glass plate, on which a tire is placed, which is gradually loaded. The disadvantage of this type of measurement is that it is only a simulation, not real measurements. Another disadvantage is the used material of the pad, which in these cases is usually glass, and this has completely different properties than the real road surface.

The essence of the invention

The invention described below can be divided into two parts - the first - representing a method of measurement and evaluation, which deals with measuring the deformation of the tire from the inside, and the second, which is a device, the components of which are, a line laser, sensors, a camera that captures the line track of the laser and two sensors that establish , angularly rotated and the speed of rotation of the complete wheel. The track of the line laser is a wavefront, i.e. a constant phase plane copying from the inside the deformation of the pattern, which is in contact with the substrate, in our case, the road. The device is able to transmit the measured data to the evaluation device wirelessly and then based on them to evaluate the real deformation of the pattern. The device does not require the presence of contact sensors located directly on the tire casing and measures with an accuracy of tenths of a millimeter.

The device consists of a control unit that is wirelessly connected to the scanning camera and to the line laser and at the same time synchronizes the exposure of each image, the switching on of the laser and controls the transfer of measured data from the scanning camera. The wireless connection is realized by technologies such as Wifi, Bluetooth, GSM, etc. The control unit is equipped with a battery. A position sensor and a speed sensor are also connected to the control unit, and the control unit these sensors at the same time

-3 CZ 2021 - 106 A3 supplies. Both sensors are located on the vehicle axle, on the outside of the wheel. The recording camera is also wirelessly connected to the recording and evaluation unit. The acquisition camera and line laser are then powered by an external battery. The scanning camera and the line laser are detachable, but firmly attached from the inside to the tire disc in such a way that the emitted beam of the line laser is perpendicular to the inner surface of the tire and at the same time so that the scanning camera can record its light trail through its scanning angle. The recording camera is equipped with a memory card, a USB connector and a transmitter for a wireless connection from the above-mentioned group, e.g. Wi-fi.

The method of measuring the deformation of the tire pattern consists in the fact that the scanning camera uses its optics to detect the light trail left on the inner surface of the tire by a line laser.

The laser beam is projected in a plane perpendicular to the tire, this plane passing through the center of rotation of the tire, including its rim.

The scanning camera is therefore placed in a place shifted by such an angle that the entire laser beam projected by the line laser onto the inner surface of the tire is scanned. The exposure of the scanning camera is controlled through the control unit, which is represented by a microcontroller located outside the tire, on the outside of the wheel).

When calibrating the scanning camera, depending on the specific measurement conditions, i.e. on the camera optics used, the size of the rim and tire, which determine the places for mounting the laser and the camera, an unambiguous conversion of the individual image points of the camera sensor, which is a natural part of it, to coordinates is achieved in the space of the plane of the emitted laser beam.

The wheel position is evaluated by both sensors, the position sensor and the speed sensor. There is a time interval (delay) between sending the exposure command and the actual exposure, which is determined by the used software and hardware equipment of the camera. From the measured rotation speed of the wheel measured by the speed sensor and from the time interval when the tire was in the measuring position (position for starting the laser, see Fig. 2), the time of the beginning of the exposure of the scanning camera is determined (position for starting the camera, see Fig. 2). Thus, when the tire is turned into the ideal position for measurement, the image is already being recorded. The inner space of the tire is completely without lighting in this phase of the measurement, as a result of which the sensor camera chip does not record any image. At the moment when the position sensor evaluates that the position of the tire for sensing is ideal, i.e. the position when the tire is turned so that the emitter of the laser beam is directed perpendicular to the road (position for starting the laser, see Fig. 2), it is for a precisely defined time , which depends on the sensitivity of the camera sensor, the line laser emitter is started, whose laser beam projects a light trail onto the inner wall of the tire. At this moment, the emitter of the line laser beam is perpendicular to the road and the tire shows signs of deformation associated with its rolling on the surface, i.e. the road. Subsequently, the captured curves are evaluated by software and, by means of time stamps, they are unambiguously identified with the position of the tire, as shown in Fig. 4.

Stone sensors with its optics and line laser can also be encapsulated into one unit, which is very suitable for handling especially smaller tires.

The advantage of the invention is that it does not require the application of touch sensors, so it is non-contact, fully automatic and has a relatively high accuracy (resolution 1 mm .-1-.0.2 mm). It is also advantageous that the device can be applied to a wide range of tire types, for example racing motorcycles, motorcycle tricycles, racing cars, ordinary cars and trucks.

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Clarification of drawings

In Fig. 1 there is a diagram of the device. Fig. 2 schematically shows the method of measurement with individual positions. Giant. 3 then represents the laser track on the inner side of the tire and Fig. 4 then the measurement evaluation graph.

Examples of implementation of the invention

Example 1

The device consists of a control unit U which is wirelessly connected to the scanning camera 3 and to the line laser 2 and at the same time synchronizes the exposure of each image of the scanning camera 3, starts the line laser 2 and controls the transfer of measured data from the scanning camera 3. The wireless connection is implemented via Wi-fi . Control unit 1 is equipped with a battery. A position sensor 4 and a speed sensor 5 are also connected to the control unit 1, while the control unit 1 supplies these 4 sensors simultaneously. Both sensors 4.5 are located on the axle of the passenger vehicle, on the outside of the wheel. The recording camera 3 is also wirelessly connected to the recording and evaluation unit 6. The recording camera 3 and the line laser 2 are powered by an external battery. The scanning camera 3 and the line laser 2 are detachable, but firmly attached from the inside to the tire disc by means of holders and straps, so that the emitted laser beam 10 of the line laser 2 is perpendicular to the inner surface of the tire and at the same time so that the scanning camera 3 can record its light trail on the inner surface of the tire through its sensing angle. The laser beam 10 is thus projected in a plane perpendicular to the tire, this plane passing through the center of rotation of the tire, including its rim. The recording camera 3 is equipped with a memory card, a USB connector and a transmitter for a wireless Wi-fi connection.

The scanning camera 3 is thus placed in a place shifted by an angle that enables scanning of the entire trace of the laser beam 10 projected by the line laser 2 on the inner surface of the tire. The exposure of the sensing camera 3 is controlled via the control unit L

Before the actual measurement, the sensing camera 3 is calibrated. When calibrating the sensing camera 3, depending on the specific measurement conditions, a clear conversion of the individual image points of the sensor of the sensing camera 3 to coordinates in the space of the plane of the emitted laser beam 10 is achieved.

The wheel position is evaluated by both sensors, the 4-position sensor and the 5-speed sensor. From the measured rotation speed of the wheel measured by the speed sensor 4 and from the time interval when the tire is in the measuring position, which is represented by position 8 for starting the line laser 2, the time of the beginning of the exposure of the scanning camera 3 is determined. That is, at the time when the tire is rotated to the ideal position for measurement, the recording of the image is already in progress, which was started in position 9 to start the sensing camera 3. The inner space of the tire is completely without light in this phase of the measurement, as a result of which the sensing camera chip does not record any image.

At the moment when the position sensor 4 evaluates the position of the tire for sensing as ideal, i.e. the position when the tire is turned so that the emitter of the laser beam 10 is directed perpendicular to the road 11, it is triggered for a time that depends on the sensitivity of the sensor of the sensing camera 3 the emitter of the line laser 2 and its laser beam 10 projects a light trail onto the inner wall of the tire, while the tire shows signs of deformation associated with its rolling on the surface, i.e. the road 11. Subsequently, the scanned light trails of the laser beam 10 in the form of a curve are evaluated by software and through of the timing marks are uniquely identified with the tire position as shown in Fig. 4.

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Example 2

Example 2 differs from example 1 in that the device is used for measurements on truck tires. In this case, wireless transmission is via Bluetooth technology.

Example 3

Example 3 differs from example 1 in that the line laser 2, the scanning camera 3 and its optics 12 are encapsulated in a plastic case. The measurement is made on the tires of a racing motorcycle.

Example 4

Example 4 differs from example 2 in that the line laser 2, the scanning camera 3 and its optics 12 are encapsulated in a plastic case, which is subsequently applied to the tires of a Formula 1 racing car.

Industrial applicability

The device is intended for specialized measurements for tire manufacturers (rubber industry) and thus enables assessment and subsequent modification of tire constructions.

Claims (8)

1. Device for non-contact measurement of tire tread deformation, which includes a scanning camera, characterized in that the control unit (1) of the device is wirelessly connected to the scanning camera (3) and line laser (2) and is further connected to the sensor (4) position and speed sensor (5), while the control unit (1) is equipped with an internal battery to which both sensors (4,5) are connected, and the scanning camera (3) and line laser (2) are connected to an external battery, scanning camera (3) is also bidirectionally connected to the recording and evaluation unit (6) for controlling the transfer of measured data. 2. The device for non-contact measurement of tread deformation according to claim 1, characterized in that the sensing camera (3) includes optics (12), a USB connector, a transmitter for wireless connection and a storage medium. 3. Device for non-contact measurement of pattern deformation according to claim 1 and 2, characterized in that the scanning camera (3) and the line laser (2) are separate units or are encapsulated in one unit. 4. Device for non-contact measurement of tread deformation according to claim 3, characterized in that the scanning camera (3) and line laser (2) or their encapsulated unit are adapted to be attached to the tire disc. 5. Device for non-contact measurement of pattern deformation according to the preceding claims, characterized in that the scanning camera (3) and the line laser (2) are moved relative to each other so that the optics (12) of the scanning camera (3) are in contact with the line laser (2) ) angle for the entire scanning length of the laser beam track. 6. Method of non-contact measurement of tire tread deformation with the device according to claim 1, characterized in that the light trace of the laser beam is projected onto the inner wall of the tire at the moment when the laser beam (10) is perpendicular to the road (11) and the tire is deformed by its by rolling on the road (11), this trace is then fed by the sensing camera (3) in the form of at least one curve to the recording and evaluation unit (6), where it is evaluated and assigned time markers for unambiguous identification with the position of the tire during rolling and is thus obtaining the resulting internal profile of the laser track in two-dimensional space. 7. The non-contact deformation measurement method according to claim 6, characterized in that the control unit (1) starts the line laser (2) at the moment when the position sensor (4) sends the information to the control unit (1) that the emitter of the line laser is in perpendicular position to the road (11). 8. The method of non-contact measurement of deformation according to claim 6, characterized in that the time of the beginning of the exposure of the sensing camera (3) in the position (9) for starting the sensing camera (3) is defined as the intersection of the speed of rotation of the wheel from the speed sensor (5) and the time interval when the tire is in position (8) for starting the laser.