This matches the visions and strategies of vehicle manufacturers, car suppliers and tire manufacturers regarding intelligent tire/wheel systems, which are summarized. An overview of selected patent applications for systems and key components of intelligent tire/wheel systems is given.
Introduction
Key technologies for intelligent tire/wheel systems are wireless data transmission and battery-free power technologies. An overview is provided of selected patent applications for systems or key components of intelligent tire/wheel systems.
Accident Analysis
- Introduction
- Finland
- Germany
- Conclusion
In two out of three tire-related accidents either worn tires or tires unsuitable for road conditions were a major contributing factor. The most important risk factor in wet road conditions is worn tires (about 8%) (see table 2.2-1).
Trends and Strategies
Vehicle manufacturers
In the field of intelligent tire systems, Tire Pressure Monitoring Systems (TPMS) are the first products introduced to the market. European OEMs have been the first players to introduce TPMS as a first step towards intelligent tire/wheel systems in the automotive market.
Automotive electronics suppliers
In addition to the sensor system, the design of the interface between the tire/wheel system and the vehicle is of great importance for the implementation of an intelligent tire/wheel system. Another trend that an intelligent tire/wheel system can benefit from is the development of robust electronics for a harsh vehicle environment, e.g.
Tyre manufacturers and co-operations
The introduction of x-by-wire systems is a foreseeable future trend for automotive applications. Although wires are used for x-by-wire systems, the lessons learned from this development, especially on the relevant architectures, standards and product homologation process, can be applied to the design and development of an intelligent tire/rim system that uses wireless. technologies.
Tyre Pressure Monitoring Systems (TPMS)
- Indirect measurement
- Direct measurement - active sensors
- Battery-operated sensor technology in general
- Clamp-on-rim sensors
- Valve-attached sensors
- Valve-cap-integrated sensors
- Direct measurement - passive sensors
- Introduction on batteryless sensor technology
- Batteryless TPMS at 2.4 GHz
- Other systems
- Conclusion
Other aftermarket products that have a sensor with steel clamp fixation are TireSafe from Algonquin Scientific (USA) (Figure 4.2-4), Tire-SafeGuard from Topchek System (China) (Figure 4.2-5), The Third Eye from Strong Frontier (Malaysia) ) (Figure 4.2-6) and TMS from A. Another Taiwanese company with a presentation of a TPMS on their website is Lite-On Automotive (Figure 4.2-20).
Advanced Tyre Sensor Systems
- Side Wall Torsion sensor
- Darmstadt tyre sensor
- Surface Acoustic Wave sensor
- Conclusion
Mechanical problems are largely eliminated because the inner wall of the tire facing away from the curb is magnetized. An important requirement in the automotive market is the free choice of tire by customers and vehicle manufacturers. The movements of the tread block depend on the friction and forces at the tire-road contact and can be monitored.
Standard steel cord tapes can therefore be examined without any influence of the steel cord on the magnetic field. This parameter depends on the sensitivity of the Hall cross magnetic field, the size of the magnet and the distance of the Hall crosses. The results show that the longitudinal deformations depend on the available friction between the tire and the road.
It is used to describe the behavior of the tread element at the tire contact patch. The change in the difference between these two frequencies is directly proportional to the difference in pressure of the belt and the reference chamber. The main issues regarding SAW sensors for tire applications are the robustness of the electronics and the way to integrate them into the tire.
Basic Sensor Technologies
- Introduction
- Acoustic sensor
- Optical sensor
- Vibrating string sensor
- Ultra Wide Band technology
- Capacitive sensor
- Micromechanical sensor
- Capacitive displacement sensor
- Measurement of capacitance
- Conclusion
An optical sensor concept for measuring the water film height on the road surface is shown in Figure 6.3-2. Depending on the percentage of the received diffused and reflected light, the water film height is calculated using a specific algorithm. The spectral intensities of the reflected light are analyzed and an algorithm is used to detect the road condition such as dry, wet, icy, snowy.
When mechanically excited, the wire vibrates at its natural frequency, which is related to the length of the wire, the properties of its material, and the state of stress. It was found that the vibration of the wire modulates the radio signal to the frequency of the vibration. The ratio between the natural frequency and the voltage in the wire determines the high sensitivity of the sensor.
Using interdigitated capacitor, a lateral displacement sensor can be designed which provides a better sensitivity than that shown in Figure 6.6-4 (see Figure 6.6-5). What physical phenomena in the tire/wheel system and the tire-road interface contain relevant information needed for specific vehicle applications. Which is a suitable design for an integrated electronics including all components of the overall system and for a mechatronic integration in the tire/wheel system.
Basic Technologies for Wireless Data Transmission
- Technology overview
- Classification of wireless data transmission
- Data transmission of passive wireless sensors
- Existing wireless vehicle applications
- Standards and regulations
- Trends
- Wireless sensors using active radio communication
- Vehicle applications using active radio communication
- Conclusion
The cost of producing this type of sensor is a few cents in large quantities. A more advanced concept of using a two-way RF connection would allow identification with only one antenna and one receiver in the vehicle. In this band, however, the allocated radiated power is only 0.5 W in Europe, while in the US the reader can use 4 W.
In the 2.400 GHz - 2.4835 GHz band, which is allocated worldwide, a much higher transmission speed may be possible. These high data rates could allow sensor data to be transmitted from the tire to a receiver in the vehicle chassis without pre-processing. An important aspect is the interference caused by other radio receivers in the same frequency band.
A Bluetooth transceiver, for example integrated into the trip computer, is able to transmit vehicle data (thus also tire data) to a Bluetooth-equipped PDA or GSM mobile phone. For the subsystem of wireless data transmission in the APOLLO project, an active radio communication capable of receiving and transmitting radio signals seems to be the suitable one. There is a potential perspective to switch to a more powerful radio communication technology at higher frequency bands in the future.
Basic Technologies for Batteryless Power Supply
- Introduction
- Inductive power transmission
- Power generation
- Capacitive generator
- Piezo generator
- Summary
- Conclusion
Distance is limited to the ranges of the lines of force emitted by a magnetic field generator. For an efficient power transfer, the coil radius of the reader must be in the order of magnitude of the distance. The parameters are the relative permittivity (er) of the material and the area (A) and the distance (d) of the electrodes.
If pressure is applied to the electrodes and the surface area remains constant, the change in capacitance depends on the bulk modulus of the dielectric (center). At constant charge, the energy is inversely proportional to the square of the capacitor surface area. With an energy density of approximately 0.2 J/g, the device's output is a maximum of 0.28 J per heel strike.
Power supply is one of the key points in the design of an intelligent tire. Thus, power supply aspects have a strong impact on the overall system architecture of the electronics required for an intelligent tire/wheel system. The conclusions of the possibilities of different techniques for batteryless power supply are presented below (Table 8.3-4).
Physical Properties of Tyre/Wheel System
Tyre attenuation at 434 MHz, 869 MHz, and 2.45 GHz
The λ/4 monopole antenna located in the center of the rim is used as a radiation source. The other three sides of the box that limit the problem are so-called 'radiation boundaries' that absorb the radiation to which they are exposed. This makes the situation similar to that where the tire is in free space.
The simulations based on the worst case situation of permittivity values predict slightly higher attenuation values, but the difference between 434 MHz and 869 MHz is approximately the same. The 2.45 GHz case could not be simulated due to the magnitude of the problem in wavelengths (software limitations). Using the data from Table 9.1-1, one can estimate the power available for the sensor from the electromagnetic radiation.
In conclusion, the bandwall attenuation at UHF and microwave frequencies is not prohibitively large, less than 20 dB. The frequencies 434 MHz and 468.2 MHz are probably too low for band applications because antennas are too large, especially if the radiation is the only power source for the sensor. The polarization of the radiation must be such that the electric field is perpendicular to the tire due to the steel wires of the tire.
Electromagnetic properties
- Introduction
- Measurement results of permittivity
- Attenuation of magnetic field below 100 MHz
The two different materials of the tire samples used are indicated in the following figures by the red and blue color of the graphs. The relative permittivity is typical for most plastics – between 4 and 5 throughout the frequency range. 9.2-3: Relative permittivity (ε') and loss factor (ε") for a typical low graphite rubber in the frequency range 1 MHz - 1 GHz.
The measurement results for the steel tire samples from Pirelli are shown in the figures below. It is interesting to note the resonance behavior of the rubber sample in Figure 9.2-5 at about 900 MHz. The attenuation of the ac magnetic field through the rubber composite with embedded steel belt was measured using the setup shown in Figure 9.2-6.
The measurement was done with and without the rubber connection between the coils in the frequency range 0.1 – 100 MHz. The permittivity is measured in the frequency range of 1 MHz – 1 GHz for several samples of rubber material. More important for evaluation is the Q value which is the ratio of the relative permittivity (ε') and the loss factor (ε").
Patent Overview
- Accelerometer and other sensors
- Tyre integration
- Antenna
- Power transmission / generation
- General aspects of total system
- Conclusion
A light beam emitter and an optical sensor are mounted on the rim, and a reflector is mounted opposite the inner surface of the tire. It is important to maintain the standard behavior of the tire (including performance, integrity and fatigue). A module that checks the tire information is supported by a rubber layer applied to the inside of the tire.
A method is described for attaching a module to the inside of the tire using a special rubber layer. The patch is adapted to carry the recording device and to mount the recording device to the inner lining of the tire. The focus of the invention concerns the mounting and electrical contact of the antenna and the monitoring device.
The antenna is mounted on the sidewall of the tire outside the body cord of the tire, or it is embedded in the body of the sidewall. The system is used for an automatic update of the tire monitor's position on the vehicle. A system for monitoring the condition of the tire (condition not specified) is part of the proposed concept.
Abbreviations and References
Chapter 4 References (Tire Pressure Monitoring Systems (TPMS)) [NR1] http://www.autospeed.com/A_1267/P_4/article.html. NR10] http://www.asiapacific.com.my/the3rdeye/home.html [NR11] http://www.ambromley.co.uk. NR21] http://www.visteon.com/technology/automotive/tirepress_monitor .shtml [NR22] http://www.alltech.it.
