Rotating friction coefficient measuring ball for cars and trucks

Abstract

(Main claim) Friction coefficient measurement system for a vehicle, comprising a freely rotating sensor sphere provided with a rubberized running surface and having sensors for measuring rotational speed, normal and tangential forces, wherein the sensor sphere is in direct contact with the road surface and the coefficient of friction between the sphere and the road surface is calculated in real time.

Description

Technical field

[0001] The invention relates to a system for the mobile detection of road surface conditions, in particular the coefficient of friction between tires and the road surface. The system is intended for use in road maintenance vehicles, emergency services, automobile clubs (e.g., ADAC), and other road safety organizations. "The system is particularly suitable for mountain passes, steep inclines and declines, tunnel portals, and winding mountain roads." State of the art

[0002] Known systems for recording road surface conditions are predominantly based on: • optical camera systems for detecting snow, water and ice, • Infrared sensors for measuring surface temperature, • driving dynamics models (ABS / ESP) that indirectly derive the coefficient of friction from wheel slip, • stationary measuring stations on individual road sections.

[0003] However, these systems do not provide a direct mechanical measurement of the coefficient of friction. In particular, no mobile system exists that: • uses a freely rotating sensor ball with a defined rubber running surface, • provides interchangeable balls for summer, winter and rainy conditions, • Directly measures frictional forces and slippage, • Recommended driving speeds calculated for cars and trucks, • derives optimal tire pressures for current conditions, • and transmits the data in real time to road authorities and automobile clubs. Description of the invention

[0004] The invention solves the aforementioned problems through a modular friction coefficient measurement system that is integrated into a vehicle and consists of the following main components: 1. Freely rotating sensor sphere ◯ with rubber tread and defined profile structure, ◯ with integrated pressure sensor (TPMS), ◯ with interchangeable versions for summer, winter and rain. 2. Measuring module ◯ Detection of ball rotation using encoders, ◯ Measurement of normal and tangential forces using force sensors, ◯ IMU sensor for detecting micro-movements and slippage. 3. Environmental sensors ◯ Camera for detecting ice, snow, water, ◯ Infrared sensor for measuring road surface temperature, ◯ Outdoor temperature sensor. 4. Calculation unit ◯ Calculation of the coefficient of friction µ, ◯ Determination of the slip between vehicle speed and ball rotation, ◯ Determination of the recommended maximum speed for cars and trucks, • Determining the optimal tire pressure for current conditions, ◯ Classification of the road section (dry, wet, snow, ice). 5. Communication module • Transmission of measurement data to road maintenance depots, ADAC, traffic control centers, • Issuance of warning messages and speed suggestions. 6. Advantages of the invention • Direct mechanical friction coefficient measurement instead of indirect modeling. • Interchangeable spheres for different seasons and weather conditions. • Independent measurement of parameters relevant to cars and trucks. • Mobile application on any road segment. • Increased road safety through precise warnings and recommendations. • Optimizing tire pressure for fleet and private vehicles. • Use in real-time monitoring systems of ADAC, road authorities and winter services. 7. Feasible strategy and economic viability

[0005] The invention is technically and economically feasible, as all required components are already available in the automotive industry and can be used in modified form. The cost structure of a complete system per vehicle is as follows: 7.1. Cost of the sensor sphere • Mechanical construction (ball, rubber running surface, bearings): €150-300 • Rotary encoders, IMUs, force sensors, pressure sensors: €150-350 • Protective housing, sealing, wiring: €50-100 Total cost of sensor sphere: €350-750 7.2. Electronic modules • Electronic processing unit (ECU): €150-300 • Communication module (LTE / 5G): 50-120 € • Power supply, cabling: €50-100 Total electronics costs: €250-520 7.3. Environmental sensors • Camera (automotive quality): €80-200 • Infrared sensor for road surface temperature: €30-80 • Outdoor temperature sensor: €10-20 Total cost of environmental sensors: €120-300. 7.4. Installation costs • Mechanical integration: €200-400 • Electrical integration: €150-300 • Software calibration: €300-600 Total installation costs: €650-1,300 7.5. Total costs per vehicle • A spherical module: €1,300-2,700 • Two spherical modules (front + rear): €2,200-4,500

[0006] This makes the system suitable for installation in vehicles from manufacturers such as BMW, Mercedes-Benz, MAN, Volvo, Peugeot or other OEMs, who can then supply vehicles to road maintenance depots, mountain rescue services, police, ADAC or insurance companies. 8. Sensor list and electronic components

[0007] The system includes the following sensors and modules: 8.1. Sensor sphere modules • Rotary encoder for measuring ball speed • IMU sensor (Inertial Measurement Unit) with 3-axis gyroscope and 3-axis accelerometer • Force sensors (normal and tangential force) for direct determination of the coefficient of friction • Pressure sensor (TPMS) for monitoring the internal ball pressure • Temperature sensor for monitoring the sphere temperature • Replaceable rubber treads (summer, winter, rain) 8.2. Environmental sensors • Front camera for optical detection of: ◯ Snow ◯ Ice ◯ Water ◯ Slush ◯ dry road surface • Infrared sensor for measuring surface temperature • Outdoor temperature sensor • Humidity sensor (optional) 8.3. Vehicle and system integration • CAN bus interface for recording vehicle speed • ECU processing unit for calculating: ◯ Coefficient of friction µ ◯ Hatching ◯ Recommended speed for cars and trucks ◯ optimal tire pressure • Communication module (LTE / 5G) for data transmission to: • ADAC • Road maintenance depots • Traffic control centers • Insurance (optional) 8.4. Software modules • Friction coefficient calculation • Slip analysis • Road classification • Speed ​​calculation • Print recommendation algorithm • Data logging and cloud transfer 9. Areas of operation on critical road sections

[0008] The friction coefficient measuring system according to the invention is particularly advantageous for use on road sections that have an increased risk of accidents due to climatic and topographical conditions. These include, in particular: 9.1. Roads with frequent snowfall and winter conditions

[0009] In regions with heavy snowfall, snowdrifts, and prolonged sub-zero temperatures, the system enables precise measurement of the actual coefficient of friction between the road surface and the sensor sphere. This allows winter maintenance services and traffic control centers to identify early on when gritting measures are necessary and what speeds are safe for cars and trucks. 9.2. Sections with a risk of icing (black ice, freezing ice, frozen wetness)

[0010] On roads prone to sudden icing – for example, in high humidity, shaded areas, or with temperature changes – the sensor sphere provides a direct mechanical measurement of slippage. This enables warning messages such as "Danger: Black ice – recommended speed 30 km / h". 9.3. Dangerous Curve Sections

[0011] Curves with a tight radius or changing gradient pose an increased risk, especially in snow, wet conditions or ice.

[0012] The system detects: • premature understeering or oversteering, • reduced lateral force build-up, • Critical drops in friction coefficient when turning.

[0013] The processing unit can derive a recommended cornering speed for cars and trucks and transmit it to traffic control systems. 9.4. Tunnel exits and tunnel portals

[0014] During the transition from the warm tunnel interior to the cold outside air, the following often occur: • frozen wetness, • local black ice, • abrupt changes in the coefficient of friction. The sensor sphere detects these changes immediately and enables automatic • Warning to following vehicles or traffic control centers. 9.5. Mountain passes and altitudes (mountain roads, alpine passes, inclines and declines)

[0015] The following occur particularly frequently at high altitudes: • rapid temperature changes, • Icing caused by wind, • Snowdrifts, • Abrupt fluctuations in the coefficient of friction. • On inclines and declines, the rotating friction coefficient measuring sphere enables precise measurement of the available lateral and longitudinal friction coefficient.

[0016] The mobile system can regularly drive over such sections and provide precise data to road maintenance depots, mountain rescue services and automobile clubs (e.g. ADAC). 9.6. Bridges and viaducts

[0017] Bridges cool down faster than regular roads and ice up sooner. The sensor sphere detects: • beginning of slipperiness, • reduced coefficient of friction during braking, • critical slip values.

[0018] This data can be automatically transferred to variable traffic signs. 9.7. Shady areas and wooded sections

[0019] Roads that are permanently in shadow retain ice and snow for significantly longer. The system enables continuous monitoring of such sections and provides real-time data on: • Residual snow, • frozen moisture, • local areas of slipperiness. 10. Benefits for road safety and infrastructure operators

[0020] By deploying the system on the aforementioned critical sections, the following can be achieved: • Reduced accidents, • Winter services optimized, • Speed ​​limits dynamically adjusted, • More precise warning messages and • Insurance risks can be better assessed.

[0021] The combination of mechanical friction coefficient measurement, optical road surface detection and real-time communication represents a significant improvement over existing systems. 11. Support for legal requirements for summer and winter tires

[0022] In many European countries, including Germany, Austria, and Switzerland, there are legal requirements regarding the use of summer and winter tires. These regulations stipulate that vehicles must be equipped with suitable tires in winter road conditions, with sufficient tread depth and a winter-suitable rubber compound.

[0023] The system according to the invention with the rotating friction coefficient measuring sphere for cars and trucks offers considerable advantages in this context: 11.1. Optimized selection of summer and winter tires

[0024] By directly mechanically measuring the coefficient of friction µ between the sensor sphere and the road surface, the system can precisely determine which type of tire offers the best grip under the current conditions.

[0025] This enables: • Recommendations for choosing suitable winter tires in snow, ice and slush, • Recommendations for choosing suitable summer tires in dry and warm conditions, • objective evaluation of different tire profiles and rubber compounds. 11.2. Determining the optimal tire pressure

[0026] The sensor sphere has an integrated pressure sensor and serves as a reference tire. Based on the sphere's behavior under real-world driving conditions, the system can determine the optimal tire pressure for cars and trucks.

[0027] This is particularly relevant because: • Too low pressure reduces the coefficient of friction and increases the braking distance, • Excessive pressure reduces the contact area and impairs adhesion, • Incorrect pressure in winter tires leads to unstable driving behavior.

[0028] The system can therefore provide real-time recommendations such as: • “Recommended tire pressure for current conditions: 2.4 bar (passenger car)” • “For trucks: 7.5 bar recommended due to reduced grip on snowy roads” 11.3. Support from authorities, automobile clubs and insurance companies

[0029] The precise friction coefficient data enable: • objective assessments of road safety, • Recommendations for mandatory winter tires on certain routes, • Support for ADAC, police and road maintenance departments in risk assessment, • Well-founded decisions by insurance companies when analyzing accidents. 11.4. Contribution to road safety

[0030] Through the combination of: • direct friction coefficient measurement, • optical lane detection, • Temperature measurement, • and analysis of the optimal tire pressure The system can significantly contribute to improving compliance with legal tire requirements and considerably increasing road safety in winter and wet conditions. Rotating friction coefficient measuring sphere for cars and trucks. Illustrations and installation position of the sensor sphere. Fig. 1

[0031] Fig. The figure shows a schematic front view of a vehicle with a sensor sphere positioned centrally below the front bumper. The sphere is arranged so that it is in direct contact with the road surface and enables reliable friction measurement regardless of the vehicle's drive system (front-, rear- or all-wheel drive).

[0032] The positioning of the ball can vary depending on the vehicle type and area of ​​application: • In passenger car modules, the ball is typically mounted in the area of ​​the front axle to record the steering behavior and the friction coefficient conditions when entering a curve. • In truck modules, the ball can also be attached in the area of ​​the rear axle to analyze stability when exiting curves and braking processes under load. Influence of road surface type on spherical profile and measurement strategy

[0033] The choice of rubber tread and internal pressure of the sensor sphere depends on the road surface type and the climatic conditions of the test track. Different sphere variants are used depending on the application: • Summer tire: for dry and warm roads, with low tread depth and higher pressure. • Winter globe: for snowy and icy roads, with a deeper tread and softer rubber compound. • Rain globe: for wet and slippery roads, with a special water displacement structure.

[0034] The sphere thus serves as a reference tire, whose behavior under real conditions supports the selection of suitable vehicle tires and their optimal air pressure. Fig. 2 - Installation position of the sensor sphere in the front area

[0035] Fig. This shows a perspective front view of a classic car with a stylized body shape. The sensor sphere is clearly visible in the lower front area, positioned centrally below the radiator grille.

[0036] The illustration shows: • the typical installation position of the rotating friction coefficient measuring sphere in vehicles with front-wheel drive or all-wheel drive, • the integration of the ball into the lower area of ​​the front bumper, so that it has direct contact with the road surface, • the option to replace the sphere as needed (summer, winter or rain version), • the visual distinction between vehicle design and sensor module.

[0037] The sphere is arranged in such a way that it: • works regardless of vehicle design, • does not impose any restrictions on ground clearance or driving behavior, • and enables a stable measurement of the coefficient of friction during steering, braking and acceleration.

[0038] This installation method is particularly suitable for: • Passenger car test vehicles, • ADAC measuring vehicles, • Fleet vehicles for road analysis, • as well as for integration into production vehicles with an optional safety module. Fig. 3 - Installation position of the sensor sphere in the rear area

[0039] Fig. The image shows a stylized side view of a vehicle with a clearly marked sensor sphere in the lower rear section of the body. The sphere is positioned centrally below the rear and is in direct contact with the road surface.

[0040] This type of installation is particularly useful for: • the recording of friction values ​​at the curve exit, • the analysis of braking behavior under load, • the assessment of rear axle stability, • the detection of oversteer or rear-end slides in wintery or wet conditions.

[0041] The rear ball can: • can be used in addition to the front ball (dual-ball system), • especially used in truck vehicles, • contribute to symmetrical friction coefficient measurement in all-wheel drive vehicles.

[0042] The combination of front and rear spheres creates a complete picture of the driving dynamics on critical road sections such as: • Downhill runs (gradients), • Tunnel exits, • icy curves, • Bridges and shaded areas.

[0043] The ball at the rear is also replaceable and can be fitted with specific rubber profiles for summer, winter or rain conditions. Fig. 4 - Installation positions of the sensor sphere, front and rear

[0044] Fig. shows a schematic representation of a vehicle with two marked installation positions for the rotating friction coefficient measuring sphere: • Front (front area): The sphere is mounted centrally below the front bumper. This position allows for the measurement of friction coefficients during steering, cornering, and braking on wintry or wet roads. It is particularly suitable for front-wheel drive or all-wheel drive vehicles. • Rear (back area): The sphere is located below the rear bodywork, near the rear axle. This position is used to analyze driving behavior when exiting curves, rear stability, braking under load, and in rear-wheel drive vehicles.

[0045] The combination of both ball positions allows for a complete dynamic friction coefficient analysis along the vehicle length and provides differentiated data for: • Passenger cars (cars), • Trucks (lorries), • Vehicles with different drive configurations (front, rear, all-wheel drive).

[0046] The sensor spheres are interchangeable and can be fitted with specific rubber profiles for summer, winter, or rainy conditions. The measured data is processed in real time and used to calculate: • optimal driving speed, • suitable tire pressure, • Selection of suitable tire types, • Warning messages for critical road sections. Fig. 5 - Installation position of the sensor sphere in truck vehicles

[0047] Fig. The figure shows a schematic side view of a truck with a marked sensor sphere located below the front left wheel. The sphere is positioned so that it is in direct contact with the road surface and records the coefficient of friction under real load conditions.

[0048] This configuration is particularly suitable for: • Trucks, • Transport vehicles, • Winter service and mountain rescue vehicles, • ADAC measuring vehicles for heavy classes.

[0049] The front ball joint on trucks enables: • the measurement of the coefficient of friction when starting on inclines, • the analysis of braking behavior on gradients, • the assessment of driving stability under heavy loads, • the detection of critical road conditions at tunnel exits, bridges and icy mountain passes.

[0050] The ball is interchangeable and can be fitted with specific rubber profiles for summer, winter or rainy conditions.

[0051] The measurement data is processed in real time and used to calculate: • Recommended speeds for trucks on critical sections, • optimal tire pressure for heavy vehicles, • Warning messages for drivers and traffic control centers.

[0052] This installation method is particularly relevant for: • Mountain passes, • long downhill stretches, • icy ramps, • Access roads to tunnels and bridges, • as well as for insurance and fleet analysis under winter conditions.

Claims

[1] (Main claim) Friction coefficient measuring system for a vehicle, comprising a freely rotating sensor sphere provided with a rubberized running surface and having sensors for measuring rotational speed, normal and tangential forces, wherein the sensor sphere is in direct contact with the road surface and the coefficient of friction between the sphere and the road surface is calculated in real time. [2] System according to claim 1, characterized by that the sensor sphere is interchangeable and is provided in versions for summer, winter and rainy conditions. [3] System according to claim 1 or 2, characterized by that the sensor sphere has an integrated pressure sensor for monitoring the internal sphere pressure. [4] System according to one of the preceding claims, comprising a camera for optical detection of the road surface condition. [5] System according to one of the preceding claims, comprising an infrared sensor for measuring the road surface temperature. [6] System according to one of the preceding claims, wherein the computing unit calculates a recommended maximum speed for cars and trucks from the measurement data. [7] System according to one of the preceding claims, wherein the computing unit determines an optimal tire pressure for current road and weather conditions. [8] System according to one of the preceding claims, wherein the measurement data are transmitted via a communication module to road authorities, automobile clubs or traffic control centers. [9] System according to any one of the preceding claims, characterized by , that the computing unit generates a recommendation for selecting suitable summer or winter tires for the current road and weather conditions based on the measured coefficient of friction. [10] System according to one of the preceding claims, wherein the computing unit performs an evaluation of the adhesion performance of different tire types (summer tires, winter tires, all-season tires) based on the measured friction coefficient data. [11] System according to any one of the preceding claims, characterized by , that different sensor spheres are provided for passenger cars and trucks, with the spheres being adapted to the respective vehicle classes in terms of diameter, rubber compound, profile structure and internal pressure. [12] System according to one of the preceding claims, wherein the sensor sphere or several sensor spheres are arranged on vehicles with front-wheel drive, rear-wheel drive or all-wheel drive such that the coefficient of friction is reliably detected regardless of the respective drive concept.

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