Instrumentation • Electronics
Fig. 1. The Porsche Panamera is designed to be driven in pure electric mode by default up to a speed of 130km/h.
4 Most automotive engineers are familiar with mechanical and electrical vehicle design and testing requirements, but fewer will also know about all the EMC design and testing requirements for conventional, hybrid and electric vehicles. Boris Sedacca reports.
4 La plupart des ingénieurs automobiles connaissent la conception mécanique et électrique des véhicules ainsi que les exigences de test, mais peu d’entre eux savent tout de la conception CEM et des exigences de test pour les véhicules conventionnels, hybrides et électriques, déclare Boris Sedacca.
4 Die meisten
Fahrzeugingenieure kennen die mechanischen und elektrischen Entwurfs- und Prüfanforderungen für Fahrzeuge. Aber die wenigsten kennen auch die Entwurfs- und Prüfanforderungen für EMV in konventionellen, Hybrid- und Elektrofahrzeugen. Boris Sedacca berichtet.
The silent peril of electromagnetic interference
A
utomotive companies use their own requirements over and above those published in standards to avoid the threat of liability. In-house requirements are typically 10 times
higher than the EU Automotive requirements, often interpreted as absolute minimum requirements. As long as the in-house requirements are met, legislative requirements are just a formality for automotive manufacturers. EMC design is not just about shielding sources
of electromagnetic emissions. Keith Armstrong, principal at EMC specialist Cherry Clough Consultants argues that EMC shielding is costly and adds unnecessary weight when other measures are available by using robust circuit and software techniques. “The result of interference is a delayed,
degraded or false signal,” says Armstrong. “If interference causes a vehicle fieldbus not to recognise a data packet and it has to be transmitted again, this could be hazardous in safety circuits such as braking. There are hardware and software signal and power integrity techniques listed as good practice in the IEC 61508 international industry
standard for functional safety. “A vehicle electromagnetic environment is very
harsh because of electrical activity such as DC motors, sparking plugs and pulses that feeds a fuel injection system. Electric vehicles also produce a good deal of interference from pulse width modulation (PWM) motor drives as a series of continuous spikes and transients.
Steer-by-wire
“Hydraulic vehicle steering consumes a lot of power because the pumps are always running and so is being overtaken by electronically assisted power steering which only uses power when it is needed. In steer-by-wire systems, turning a steering wheel turns an encoder connected to a computer to steer the wheels, just as most throttles do nowadays instead of using a mechanical link between the accelerator pedal and a butterfly valve in the throttle.” Armstrong holds that improved vehicle fuel
economy has also been achieved by electronic means in other vehicle constituent parts, like suspension yaw and pitch control or stability control by modulating the braking and acceleration of
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