UAV stepped into the home, ADI launched MEMS to provide lift

Whoever thought that the drones that were exclusively used for military purposes began to penetrate into the lives of ordinary people after being widely used by the United States for anti-terrorist operations and eradicating the enemy for ten years. With the maturity of drone technology in recent years, the civilian demand for drones has also increased dramatically, including the participation of leading global technology manufacturers such as Google and Amazon, and this emerging consumer electronic product has become a future technology field. The next focus.

Similarly, the huge prospects of the drone market have attracted the attention of many upstream chip manufacturers. As the world's leading provider of high-performance signal processing solutions, ADI is constantly working on the development of drone technology and related products. And provide the core driving force for the civil aircraft process of drones.

ADI has a very high voice in the field of MEMS device development, and also provides a wealth of advanced MEMS devices for various UAVs and multi-axis aircraft. Mr. Zhao Yanhui, ADI's Asia Pacific MEMS product and application manager, said that ADI's industrial grade gyroscopes ADXRS652, ADXRS620, ADXRS623, ADXRS646, ADXRS642 and industrial accelerometers ADXL203 and ADXL278 are widely used in professional-grade aerial equipment. Commercial grade accelerometers ADXL335, ADXL326, ADXL350, ADXL345, etc., have also been widely used in all-in-one machines and various aircraft. These MEMS sensors are mainly used to achieve smooth control and assisted navigation of the aircraft. The reason why the aircraft can hover can be used for aerial photography because the MEMS sensor can detect the pitch and roll angle changes of the aircraft during flight. After detecting the angle change, the motor can be controlled to rotate in the opposite direction to stabilize. Effect. This is a typical closed loop control system. As for the measurement of angle changes with MEMS sensors, it is generally necessary to select a combination of sensors, neither relying solely on accelerometers nor relying solely on gyroscopes, because each sensor has certain limitations. For example, the gyroscope outputs angular velocity. It is necessary to obtain the angle through integration. However, we know that even in the zero input state, the gyro still has an output, and its output is a superposition of white noise and slowly varying random functions. Influence, in the process of integration, the cumulative error will inevitably be introduced. The longer the integration time, the larger the error. This requires an accelerometer to correct the gyroscope, because the accelerometer can use the force decomposition principle to determine the tilt angle by the component of gravity acceleration in different axial directions. Since there is no integral error, the accelerometer can correct the gyroscope error under relatively static conditions. However, in the state of motion, the credibility of the accelerometer output is reduced because it measures the resultant force of gravity and external force. A more common algorithm is to use complementary filtering, combined with the output of the accelerometer and gyroscope to calculate the angular change.

What advantages does ADI have over these products compared to similar products in the industry? In response to this question, Mr. Zhao Yanhui answered this question. The main advantage of ADI products is that they can obtain high-precision output under various harsh conditions. Taking a gyroscope as an example, its ideal output is only responding to angular velocity changes, but it is actually limited by design and process. The gyro is also sensitive to acceleration, which is the deg/sec/g indicator we commonly see in the gyroscope data sheet. . For multi-axis aircraft applications, this indicator is particularly important, because the motor in the aircraft generally brings more intense vibration. Once the damping control is not good, it will generate a large acceleration during the flight, which is bound to be Bringing the change of the gyro output, which causes the angle to change, the motor will malfunction, and finally the intuitive feeling to the end user is that the aircraft is not stable. In addition, in some cases, if the aircraft suddenly turns, it may cause the input speed to exceed the gyroscope's test range. Ideally, the output of the gyroscope should be saturated. After the speed returns to the gyroscope range. The gyroscope then correctly responds to real-time angular velocity changes, but some gyroscopes do not. If the input exceeds the range, the gyro will produce an oscillating output, giving a completely wrong angular velocity. In some cases, the aircraft will be subjected to large acceleration shocks. Ideally, the gyroscope should try to suppress this impact. ADI's gyroscopes are designed with this in mind, using dual-core and quad-core. The mechanical structure uses the principle of differential output to suppress the impact of this "common mode" and accurately measure the angular velocity of the "differential mode". However, some gyroscopes produce very large false outputs in this case, even producing an oscillating output.

For the aircraft, the most important point is safety. Regardless of its hardware design or software design, it must first ensure safety, and then it is the ultimate user experience. Mr. Zhao Yanhui also agrees with this view. He further represents ADI's MEMS. The sensor design concept just coincides with this. Our MEMS sensor is first to ensure stability under various extreme conditions, and then to pursue the ultimate indicator. According to the customer's measured feedback, the ADI's gyroscope output will not be affected at all by the wrong operation of the aircraft, and some other gyroscopes will have a very large zero offset. ADI's accelerometers will not cause any reliability problems after being impacted, while some other accelerometers will have no output at all with a high probability. The differences measured by these users are due to the fact that ADI MEMS sensors are designed with extreme considerations in mind.

In the view of Mr. Zhao Yanhui, the MEMS products on the future aircraft will also develop in the direction of integration, such as 3-axis acceleration plus integrated products of 3-axis gyroscopes, even SOC, integrating the processor and providing angle output directly. The backend processor is called. Since the application scene of the aircraft is generally outdoor, the customer is bound to do temperature compensation within the full temperature range, and the MEMS product is warmed up in the full temperature range before the factory, or the sensor is designed to super low temperature drift. It will be the development direction of MEMS products in this field.