TRW's TireWatch system uses a pressure sensor that's mounted on the tire valve stem to monitor air pressure and temperature inside the tire. The tire transmits the information via a radio signal to a control unit in the vehicle, which provides warning messages to the driver information display. Simultaneously, Michelin has developed an innovative tire/wheel assembly me-thod called the Pax System. This will prevent the tire from coming off the wheel when it goes flat, while providing excellent handling, mobility, and safety in run-flat situations. Together, the two partners are working to combine their complementary strengths and create a single system that will allow car makers to optimize the package for performance, reliability, weight, and cost.
According to TRW, this technology will not only alert drivers about potential problems, but it also will identify the tire involved. Under the agreement, the two will develop improved tire-pressure monitoring systems for both the Pax System and conventional radial tires.
Incidentally, the recent Firestone tire controversy has prompted the U.S. Congress to make it mandatory for auto makers to outfit all cars within three years with a warning system that indicates when a tire is significantly underinflated (see "Firestone Recall Fuels Interest In Smart Tires," wall street journal, Nov. 22, 2000, p. 1). Many more developers are jumping on this bandwagon to take advantage of new laws, whereby auto makers and consumers have no choice. Expect to possibly pay more for these new safety features, which will soon be mandatory.
As car makers attempt to surround the vehicle with an electronic cocoon, they're importing sensor technologies that are standard equipment in other transportation systems like aircraft and ships. For object detection and collision warning, they're tapping radar sensing technologies. Recently, Visteon and Raytheon entered into a cooperative deal to develop radar-based sensors for detecting objects in front of and behind a vehicle.
For back-up warning applications, the Maple Consulting Group has readied a programmable microwave sensor that combines FSK modulation and Doppler techniques to warn drivers of possible obstructions in the reverse mode. Because the microwave sensor is programmable at the time of installation, it can be used on many vehicle platforms, asserts Heyward S. Williams, president of Maple Consulting. Programmable parameters include range, priority, velocity, turn-off time, direction of motion, and alarm. The range can be programmed from 0.3 to 10 meters. It implements an autocalibration feature that improves accuracy and avoids human intervention.
The probability of avoiding an accident varies with respect to the distance that the obstacle is located from the sensor, as explained in a paper titled "A Programmable Microwave Back-Up Warning Sensor," presented last year by Williams in the Automotive Sensors & Applications session at Sensors Expo (Fig. 3). Nonetheless, Williams believes that the microwave sensor is commercially viable and can provide detection and warning in 90% to 95% of possible scenarios that could cause a collision. "Any alarm is as good as the driver," Williams notes.
The initial target for this sensor was fleet vehicles where installation procedures can be quickly established. Now, the developers are focusing on OEMs and are hoping to supply them within three years. The microwave back-up warning sensor uses a 10.525-GHz carrier with less than 10 mW of transmit power. To prevent it from interfering with other similar sensors or setting off radar detectors, the microwave sensor is pulsed at a 12% duty cycle.
Similarly, Motorola and MobilEye Vision Technologies Ltd. are collaborating to extend advanced robotic vision technology to the automotive arena. Through this alliance, Motorola will combine its expertise in microcontrollers and DSPs with MobilEye's computerized vision capabilities to develop auto safety features, such as lane-departure warning, collision warning, drowsy-driver detection, and obstacle/pedestrian detection.
There are many more opportunities for sensors in the automotive world. Engine-oil monitoring is on the horizon, where MEMS suppliers and others are diligently exploring the use of sensors to monitor the chemical composition of the oil, as well as its level. The monitor's sensors and signal-conditioning circuitry must be able to withstand the elevated temperatures of the engine and surrounding harsh environment.
Rugged packages are under development, so these sensors and electronics can be embedded in the system. With drivers seeking real-time information on vehicle dynamics, the trend is toward more on-board diagnostics and high-speed data transfers, including the use of the CAN interface (Fig. 4). Such an interface minimizes the need for a wiring harness within an automotive system while making it simpler to add or remove sensors in that environment.