Inertial Measuring has Come a Long Way
By Mr. Tommi Vilenius, Product Manager, Murata Electronics Oy, Finland
Automotive sensors and applications have come a long way since the first ball-in-tube airbag sensors. Today electronic stability control (ESC) is the main sensor application, but new applications – especially for gyros - are emerging all the time. Although the objective in most applications remains the same, improving road safety, we could soon see also user interface applications taking advantage of the high performance inertial sensors.
Featuring yaw, lateral accelerometers, and steering angle sensors, ESC is the most wide ranging automotive sensor application and the one that is most familiar to drivers and engineers. Recent sensor developments have led from a separate sensor cluster to integration in the brake ECU under the hood. This has been enabled by more robust gyro sensors like the SCC1300 from Murata that withstands the vibration and temperatures under the hood.
New applications are emerging
Besides the ESC, a number of new applications featuring inertial sensing are emerging, and it seems that we are only seeing the tip of the iceberg in terms of new applications. For example, Jaguar makes diesel engines more refined and quiet by actively measuring and damping engine vibration. With the pressure on downsizing engines, including the adoption of 2 and 3 cylinder engines as well as cylinder shut-off systems, noise, vibration, and harshness (NVH) properties are becoming more complex. As a result, more intelligent mounting systems are required. The Murata sensing elements with different measurement axes, ranges, and frequency responses are combined to analog or digital electronics, depending on system requirements and capabilities to suit any vehicle measurement need.
The same sensors with slightly different tuning are also being used to refine the ride of the Porsche Cayenne, Mercedes S-class, and many others. An interesting note is that although most vehicles only require a body sensor and a suspension position sensor, the supercar league of Ferrari and others require another accelerometer in the wheel hub, as the suspension travel in a sports car is so short.
So far we have not seen inertia-based user interfaces in the automotive environment, but as these are becoming more popular in the gaming and mobile devices, it is only a matter of time before we begin to see these kinds of applications as well.
Murata’s 3D MEMS enable robust structure and high performance
New sensor applications emerge, and to satisfy the growing demand, Murata, the market leading manufacturer and supplier of sensitive (low-g) acceleration sensors to the global automotive industry, has recently expanded its product range to gyros and combined sensors. Murata’s sensors are based on the company’s proprietary 3D MEMS technology that enables high robustness, extremely accurate measuring, and excellent offset temperature. The SCC1300, combining an X-axis gyroscope and a 3-axis accelerometer, is exceptionally insensitive to mechanical shocks and vibrations, and presents a superior angular rate bias stability over temperature and time. SCC1300 is so accurate, that according to a research study implemented by the University of Tampere in Finland, it is possible to measure the Earth’s rotation with this sensor! This, indeed, leaves some room for car designers’ imagination.