Overview of Automotive Sensors
A bunch of sensors, which includes rotational motion sensors, position sensors, gas sensors used in the exhaust, pressure sensors, linear accelerometer, occupant comfort/convenience sensors, far-distance and near-distance obstacle detection sensors, temperature sensors, mass air flow sensors, engine knock sensor and many more sensors are combined to build and control the automotive electronic systems. With the advancement in emerging, state-of-the-art sensors technologies, automotive sensors are synchronized to balance accuracy, manufacturability, robustness, interchangeability, and low cost.
Before the arrival of microprocessors, the role of the primary automotive sensors devices was to measure oil pressure, fuel level, coolant temperature, etc. The advancements in manufacturing processes have impacted automobile sector immensely by adapting micromachining and microelectromechanical systems (MEMS) for high-performing automotive sensors too. The utilization of batch processing, miniaturization, and integration of on-chip electronic intelligence has made MEMS a preferable choice for manufacturing high-performance, low-cost sensors.
The essential automotive sensors are the ones used in the powertrain system for improved fuel economy, reduced emissions and enhanced drivability of automobiles. They measure parameters like rotational motion, pressure, exhaust gas and fuel temperature, air intake, crankshaft angle and speed, etc.
Another set of automotive sensors are used in chassis application to help enhance various aspects of braking, steering and general stability of a vehicle. For chassis applications, predominant sensors include inertial acceleration and inertial angular rate sensors.
Rotational motion sensors are the most profound automotive sensors used in both powertrain and chassis systems. Variable reluctance sensors are used in engine crankshaft control, fuel injection timing, engine speed measurement, transmission input and output shaft control, wheel speed control for the antilock brake system (ABS), etc. High performing magnetoresistor, AMR and GMR sensors are used for accurate crankshaft angular measurements to detect the engine misfire.
Pressure sensors are the second most used sensors with very diverse automotive applications. Piezoresistive MEMS pressure sensors are extensively used to measure engine manifold pressure, turbo-boost pressure, and evaporative fuel leak pressure. Capacitive touch-mode MEMS sensors are used to measure tire pressure and engine oil pressure. To measure brake fluid pressure, suspension hydraulic pressure and A/C compressor pressure, capacitive ceramic-module sensors are used.
Position sensors measure linear displacements ranging between 1 μm-200 mm and angular position with a ±1° measurement accuracy. Potentiometric sensors are extensively used to measure fuel-float level, accelerator pedal angle and transmission gear position. Noncontact Hall sensors are used to measure throttle angle, EGR valve position, and wheel-to-chassis height. Hall sensors and optical-encoder sensors are used in seat belt buckles and steering-wheel angle respectively.
Yet another type of sensor called body sensors has gradually been included in the automotive sensors group. These sensors are chiefly related to passenger safety and comfort, navigation convenience and vehicle security. The body sensors help sense near obstacles and blind-spot detection, crash detection and air-bag actuation, automatic temperature, headlights and wiper controls, real-time traffic navigation, radar cruise-control and anti-theft warning systems.
More than fifty major automotive sensors are applied in different areas such as mass airflow, exhaust gas oxygen, engine knock, linear acceleration, yaw angular rate, input/output shaft speed, steering wheel angle, and torque wheel-to-wheel variance of rolling speed, webbing payout velocity etc.
The field of automotive sensors is ever evolving. More advanced, intelligent, state-of-the-art sensor technologies are expected to impact automotive systems development significantly.