SMT007 Magazine

SMT-Apr2018

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14 SMT007 MAGAZINE I APRIL 2018 to vehicle subsystems. As recently as 10 years ago, a fully mechanical coupling between the steering wheel and the front wheels was not unusual. The steering wheel connected to a shaft that connected to a rack-and-pinion system that turned the wheels, and even a more effi - cient hydraulic version of the system still main- tained a mechanical coupling between the steer- ing wheel and the tires. The story is similar for the accelerator pedal and manual transmission. The explosion of drive-by-wire technology throughout the modern vehicle has changed this paradigm. A sensor, a remote actuator, and multiple control systems have replaced the mechanical linkage. Instead of a direct connec- tion between the steering wheel and the front tires, a sensor on the steering column now measures the angle of the wheel. An embedded controller then translates that measurement into an angle and sends the value to the vehi- cle's communication bus. Elsewhere on the communication bus, another controller picks up the value, translates that into an angle of the wheel potentially based on vehicle speed and driver settings, and then commands an actuator to move the wheel to a desired angle. In many vehicles, a safety system sits in the middle of this drive-by-wire steering system to make sure the vehicle stays in the traffic lane and avoids obstacles in the roadway. As the number of power electronics subsystems in the vehicle grows, the automobile itself begins to look like an electrical microgrid with a common power bus connecting a growing list of sources and sinks of power, each managed by an inde- pendent embedded control system. The Broader Impact—Challenges Taking a slightly broader look at the implica- tions of government automotive mandates, the exponential growth in electrification and the impending end of internal combustion engines represent a radical change in the infrastructure required to support the shift in vehicle power plants. A car with an internal combustion engine requires roughly 10 minutes at nearly any petrol station to fill up its tank for another 300 miles of driving. However, even with a dedicated supercharger, a similar pit stop requires at least an hour for a fully electric vehicle to charge. Even for the slow recharge associated with a daily commute, the required charging hardware In many vehicles, a safety system sits in the middle of this drive-by-wire steering system to make sure the vehicle stays in the traffic lane and avoids obstacles in the roadway.

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