Yazaki enables in-vehicle digital video

Incorporation of digital network buses such as MOST builds the digital data infrastructure for advanced audio-video systems, according to Yazaki engineers.

Recent trends in automotive electronics point toward a growing demand for sophisticated audio and video systems in new vehicles. According to Raymond Ernst and Dave Paul of Yazaki North America, these systems are being driven by several factors, including a migration of consumer electronics devices to vehicles and a need to control these devices in the vehicle's driver and passenger environment. Their findings were presented during the SAE 2002 World Congress.

Incorporation of digital network buses such as the Media-Oriented Systems Transport (MOST) builds the digital data infrastructure in the vehicle for these advanced audio-video systems. However, additional considerations must be given to the constraints around the deployment of the audio and video devices into the vehicle and adapting them to a vehicle's digital infrastructure bus.

Today's video entertainment systems typically consist of two analog video sources: a videocassette player/digital-video disc player and a game console connected with coaxial cable to a display. Although functional, these stand-alone, analog solutions are not easily upgraded or expanded and they do not interact with other vehicle systems.

Tomorrow's systems will be capable of much more because of their digital electronics. Next-generation video entertainment systems will take advantage of additional devices in the vehicle as well as services from outside the vehicle. New onboard devices include ports and gateways for consumer electronics like hand-held computers, digital camcorders, and portable digital audio players. Additional video sources will not be limited to local devices but they also will come from wireless sources as compressed digital video.

Designers not only need a means of managing and switching these multiple sources, but also need a cost-effective means of making the system reliable and easy to operate. In addition to solving the routing and distribution issues, a network also is easily upgraded as new features and services become available. These new features and services present new challenges for designers who must deal with multiple video formats from many sources while processing and routing them to various destinations.

As the requirements for in-vehicle networking continue to gain momentum, the need for video encoding and decoding products will be significant. Matching video input characteristics to the display's capabilities should shape the system's architecture. From a system perspective, overall price and performance tradeoffs suggest the use of Motion Pictures Export Group-1 (MPEG-1) encoding of video and audio as opposed to newer generations of compression techniques.

- John Fobian

Passive keyless entry from Microchip

Remote keyless entry uses a unidirectional transmission for authentication, while passive keyless entry relies on a bidirectional IFF sequence to identify the key. Click to enlarge

Remote keyless entry (RKE) has become a standard feature on many vehicles (as well as garage door openers), even those at the low end of the range. Although it is an easy way to unlock doors or gates, manufacturers are now looking to the next generation of convenience, according to Fanie Duvenhage, Product Marketing Manager, Microchip Technology Inc.

The next-generation, called passive keyless entry (PKE) systems, are designed so that the user does not have to press a button to gain entry to the vehicle or home. Instead, the user simply carries the electronic key around in a pocket, bag, or attached to a belt. The controller in the doors uses radio frequency (RF) communications to determine whether the key is present and uses that to unlock the doors. Activation can be as simple as raising a door handle. The system uses that as a trigger event to query the electronic key and decide whether to unlock the door or not. Passive-entry systems can even be designed to unlock the doors when the key-holder is within a couple of feet, so that there is no waiting time at all.

As with conventional RKE, PKE systems need high security. Conventional RKE is a unidirectional process. The user presses a button and a code generated by an encryption algorithm is transmitted to the base station. Passive entry depends on bidirectional communications to perform an "identify friend or foe" (IFF) operation for security. To authenticate the communication, the vehicle sends a random challenge to the key; the key encrypts this value and sends it back to the vehicle. The vehicle performs the same encryption and compares the value received from the key with its own calculated value and unlocks if the value matches.

Click to enlarge.

Because a typical PKE transmitter can also be used as a conventional RKE transmitter, it will be powered by battery, which makes battery life a critical design parameter. To obtain the required range of 1.5 m (5 ft) from the low-frequency 125-kHz signal, the detection circuitry needs to be very sensitive to detect a signal of only a few mV, but also robust enough to withstand several volts when the key is close to the sender.

There is also a power consumption issue for the base station. If the system depends purely on the proximity of the key to unlock the doors, it needs to poll continuously for its presence by generating the magnetic field at regular intervals. Although this consumes energy from the vehicle battery, it helps ensure that the doors are unlocked by the time the user lifts the handle. One way to reduce the risk of draining the vehicle battery is to wait for a trigger, such as lifting the door handle, before the flow frequency signal is activated. By triggering the field once the handle is lifted, battery power in the vehicle and key can be conserved because it reduces the number of false-trigger events caused by other cars or keys in the vicinity. The main drawback for a handle-triggered system is one of latency. The user will want to feel that the door unlocks the moment that they lift the handle.

There are a number of issues and tradeoffs that face designers planning to include passive-entry facilities in their vehicles or access control systems (table). System functionality can also be expanded to include advanced features such as mutual authentication, for which the base station can identify the key and vice versa.

- Kevin Jost

Compact starter-alternators from Continental

Continental's ISAD enables features such as stop-start, power boosting, and efficient power generation, while at the same time providing increased comfort and environmental compatibility.

The tightly packed engine compartments of today's cars set strict limits for the introduction of new systems. Engineers at Continental ISAD Electronic Systems have developed compact starter-alternator systems with small electrical machines and power electronic units in mind. Engineers presented their latest developments at an SAE 2002 42-V technical session regarding the company's integrated starter alternators with damping (ISAD) to satisfy the increasing demand for electrical power on board vehicles. ISAD enables features such as stop-start, power boosting, and efficient power generation, while at the same time providing increased comfort and environmental compatibility.

Small e-machines with high efficiency require windings with low impedance and a large active length, which means a small winding overhang. This can be achieved when L-shaped copper sheets with a rectangular cross-section are used instead of round wires. With this method, e-machines can produce approximately 25% higher torque than standard units.

The ISAD's power-electronics cooling system allows a 3-D arrangement of the components, which results in compact power units that are also able to drive integrated starter-alternators from a 12-V power supply. With a volume less than 1 L (0.2 gal), a 42-V power electronics system delivers a continuous current of up to 450 A. Systems with a starting torque of 300 N•m (220 lb•ft) for passenger cars and 1000 N•m (738 lb•ft) for commercial vehicles have been designed by the company. A heat-pipe system has been developed by engineers that not only provides effective cooling, but also acts as a vibration filter for the sensitive electronic devices, which allows the power electronics to be directly mounted to the combustion engine. The system also allows easy integration of the ISAD system in the production and test process of automakers.

The ISAD includes a power inverter that converts the battery's dc current to a three-phase ac current, creating a rotating magnetic field in the engine-fixed stator. As a result, a mechanical force is excited in the rotor, which is mechanically connected to the crankshaft. Intelligent algorithms and powerful semiconductors allow the transformation of electrical to mechanical energy with efficiencies in the 90% range. In contrast to conventional systems, it is only a matter of software to decide the direction of power conversion, so it is possible to change from motor to the generator mode and vice versa within about 10 ms. Due to this highly dynamic operation, it is possible to implement an intelligent energy-management scheme that generates electrical power during braking and is switched off during acceleration to deliver maximum torque if needed.

Today's starter-alternator-systems deliver electrical power of several kilowatts and can crank even large diesel engines. A further size reduction can be achieved when the power control unit is mounted directly to the electrical machine. Therefore, electrical losses and electromagnetic emissions as well as the costs can be significantly reduced.

- Linda Trego