Focus on Electronics

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TRW develops active roll control

The components of TRW's Active Roll Control (ARC) system. Click to enlarge

Anticipating elevated safety concerns for high-cg vehicles such as SUVs, engineers at TRW Chassis Systems have developed an Active Roll Control (ARC) system to help reduce the risk of rollover accidents. The technology will also assist vehicle manufacturers in meeting anticipated U.S. federal requirements under the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act signed by President Clinton in late 2000.

The ARC system reduces or eliminates the vehicle roll angle in cornering and can help reduce the risk of vehicle rollover using hydraulic and electronic technology. Click to enlarge

The ARC system also aids vehicle-dynamics engineers in their struggles to achieve a good compromise between vehicle ride and handling. At one end of the spectrum are large sedans and luxury cars that are focused on good ride qualities with only adequate handling behavior; at the other are sports cars with good handling but firm ride quality. In between are the many variations that are determined by vehicle manufacturers for their target customers. The ARC system allows engineers to achieve both good ride and handling, offering many of the advantages of a fully active suspension at a fraction of the cost, according to TRW. Its design allows both improved ride for single-wheel-bump inputs and eliminated body roll angle, depending on the severity of the lateral forces.

The ARC system combines typical steering and braking technologies, such as pumps and pressure control valves, with additional sensors including a lateral accelerometer, steering-angle sensor, other sensors that already exist on today's vehicles, and an actuator at one end of both the front and rear stabilizer bars. During handling maneuvers, the sensors detect the roll force created by the cornering of the vehicle. Then the actuators apply an offsetting force to the end of the stabilizer bar to reduce roll angle and assist in maintaining stability. In straight-line driving, the stabilizer bar is free to move with wheel motions up to the stroke of the actuator. Since no pressure is generated in the actuators, the bar is, in effect, disconnected. In this condition, the ride of the vehicle is markedly improved, with little or no "head toss" and better single-wheel-bump performance. In addition, axle articulation is improved for off-road use. Other benefits include improved passenger comfort due to reduced lean in cornering and increased grip, especially for independent suspensions.

In ARC straight-line driving, the stabilizer bar is free to move with wheel motions up to the stroke of the actuator, improving ride quality. Click to enlarge

Due to the increasing need for such a system, TRW is currently in negotiations for development contracts with several vehicle manufacturers in Europe and North America. By combining ARC expertise with its other technologies in steering and braking, TRW says it is able to demonstrate higher levels of performance and cost through systems integration than would be realized by using individual systems. Ultimately, this combination of advancements will form the basis of future TRW Integrated Vehicle Control Systems that will offer drivers improved vehicle control.

- Kevin Jost

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Electronics demand to grow nearly 7% annually

Worldwide demand for automotive electronics for OEM use is forecast to advance nearly 7% annually to $98 billion in the year 2005, according to World OEM Automotive Electronics, a new study from The Freedonia Group, Inc. Though established market niches—such as electronic engine controls, transmissions, and fuel-injection systems—are maturing in North America, Western Europe, and Japan, the industry is entering the next phase of evolution, characterized by strong demand for entertainment, communications, and navigation systems. In the developing world, growth is being generated by the increasing inclusion of basic electronics packages designed to improve safety, efficiency, and emissions control.

Higher per-vehicle electronics content will drive demand, with projected modest advances in light vehicle production also contributing to the growth. The rapid development of new electronic entertainment, communications, and intelligent-vehicle systems will contribute to the expanded value of electronics in the average vehicle. Growth in content value is even more impressive given the gains in overall computing power come as electronics unit prices fall dramatically—a trend that is familiar in the personal computer industry but relatively new in the automotive industry.

The best growth prospects are in several market niches, particularly entertainment electronics (mobile Internet, video, and gaming systems), advanced navigation and collision-avoidance systems, and power electronics—the last designed to handle and coordinate the rapidly growing electrical requirements of newer vehicles. Much of the expected growth in OEM electronics demand derives from a changing perception of light vehicles, which are increasingly being viewed more as extensions of the consumers living environment than as strictly transportation machines.

- Kevin Jost

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Duraswitch technology for Delphi seat switches

Duraswitch PushGate push-button technology combines the tactile feel of a traditional discrete switch with the thin profile of a membrane switch. Click to enlarge

Delphi Automotive is now developing truck-seat switches using Duraswitch PushGate push-button technology, which combines the tactile feel of a traditional discrete switch with the thin profile of a membrane switch. The slim profile and flat backside of PushGate gives engineers greater flexibility in their designs, eliminating bulkiness and providing better reliability in a switch that keeps its crisp, consistent "click" for over 500 million actuations. Delphi has exclusive rights to use and manufacture Duraswitch technology for the automotive industry.

Besides giving the desired tactile feedback, the patented PushGate push button is well suited to automated surface-mount technology; can be environmentally sealed; and exhibits good performance when exposed to extreme temperatures and harsh environments. It also easily lends itself to elastomerics, keycaps, and embossed polyester, in addition to having full key illumination capabilities. A primary benefit for designers is that the PushGate switch can be integrated into a flat panel with other slim-profile Duraswitch devices, such as rotary and slider encoders as well as multidirectional controls. The flat-panel designs have the additional benefit of eliminating the need for failure-prone component interconnections, such as solder, conductive adhesives, or wiring harnesses, to reduce costs and environmental contaminants from manufacturing processes.

Pushgate Island construction allows integration of multiple switches and switch types into a flex circuit for thin-panel design.

The unique switching element is a magnetically coupled device that employs a steel-plated armature, a magnetic sheet, and a substrate with switch contacts. The magnet holds the armature away from the fixed contact pads until actuated and, upon release, functions as a magnetic return spring. As the button is initially depressed, the magnet restrains the movement of the armature until sufficient force is supplied. At that point, the left side of the armature breaks away from the magnet, allowing the armature to contact the first fixed contact located on the substrate. As the switch is further depressed, the right-hand side breaks away and rapidly makes contact with the second fixed contact on the substrate. The armature is now bridging the fixed contacts to close the circuit. The motion of the armature creates the tactile and audible click. The magnet then draws the armature back up to its original position.

- Kevin Jost

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