UAVs, more commonly known as drones, are aircraft without a human pilot on board and are part of a more sophisticated unmanned aircraft system (UAS) that also incorporates a ground-based controller and a communication method for the controller to interface with the UAV.
Image Credit: Superior Sensor Technology
When in flight, the internal electronics of UAVs can facilitate autonomous operation, or they can be controlled remotely by a human operator. In either case, UAVs depend heavily on a variety of sensors to ensure that they perform as intended.
To properly function, UAVs depend on a number of sensors that instruct the system to adjust by measuring a variety of conditions. Some of the sensors in UAVs include:
- Accelerometers to track linear movement along any axis.
- The angle of Attack (AOA) measures the flow angle of winged UAVs and plays a critical role in determining the aerodynamic forces of the aircraft.
- Barometers to measure air pressure and establish and maintain a stable altitude.
- Gyroscopes to establish the rate of rotation, degree of tilt and angular velocity.
- GPS to determine the positioning of the UAV based on signaling from GPS satellites.
- Magnetometers to signal the strength and direction of the magnetic field to verify heading.
- Obstacle avoidance sensors to make sure a UAV or drone does not crash into other objects. These avoidance systems can include one or more stereoscopic sensors (visual cameras to see objects), LiDAR (emit light pulses via lasers to measure distances of objects), ultrasonic sensors (ultrasonic waves to determine distance from objects) and infrared sensors (similar to ultrasonic sensors but use infrared signals instead of ultrasonic waves).
- Installed pitot tubes for measuring the air speed of winged UAVs.
This article focuses on four of the types of sensors listed above that utilize highly accurate pressure sensors: accelerometers, barometers, gyroscopes and pitot tubes.
The first three are occasionally fused together to produce an Inertial Measurement Unit (IMU) to measure a number of parameters, including the pitch, roll and yaw of the UAV.
Figure 1. UAV Roll, Pitch and Yaw. Image Credit: Superior Sensor Technology
The Role of Pressure Sensors in IMUs
Pressure sensors are a key component of the different IMU elements as they can rapidly sense pressure differences and alert the UAV so that the appropriate action can be taken to adjust and correct. The three main areas where pressure sensors are deployed within the IMU system are listed below.
Barometer
Air pressure changes with altitude – the higher you go, the lower the pressure. As a barometer measures changes in altitude, a pressure sensor can rapidly measure changes in atmospheric pressure to help ensure the UAV is flying at the appropriate elevation.
Accelerometer
As an accelerometer measures air speed, a differential pressure sensor can identify any changes in air pressure from the nose of the UAV to help make sure the device sustains a stable rate of movement despite variations in the wind conditions and other external factors.
Gyroscope
Gyroscopes are installed for the measurement of angular movement, and differential pressure sensors can detect changes in air pressure due to varying angles. This is applicable for any axis movement – roll, pitch and yaw.
The Role of Differential Pressure Sensors in Pitot Tubes
Pitot tubes track airspeed, which is the measurement of the UAVs speed relative to the air around it. It is located on the UAV’s exterior and utilizes a differential pressure sensor to measure the difference between the pressure of still air (static pressure) and that of moving air condensed by the aircraft’s forward motion (ram pressure).
The difference between these pressures increases as overall speed increases.
Figure 2. Pitot Tube Diagram. Image Credit: Superior Sensor Technology
Superior Sensor’s Technology Advantage
Superior Sensors’ proprietary NimbleSenseTM architecture is an industry-first System-in-a-Sensor integrated platform.
Integrating a highly differentiated state-of-the-art pressure sensing system with the capability to incorporate optional building blocks results in the highest levels of accuracy and reliability with a lower overall system cost.
Superior’s unique technology offers a number of advantages for UAVs and other airborne devices.
Lowest Noise Floor
One of the biggest barriers pressure sensors deployed in UAVs must overcome is the noise generated by both the drone and external elements such as wind.
With the application of Superior’s integrated state-of-the-art digital filtering technology, these pressure sensors cancel out the noise created by these factors before they reach the sensor sub-system. Thus, the noise is canceled out before it becomes an error signal that can result in inaccurate air pressure readings.
Highest Levels of Accuracy
With a fast-moving UAV, any deviation in altitude, speed or angle of attack can have a direct influence on its trajectory.
To significantly reduce this potential impact, a differential pressure sensor with the highest levels of accuracy is a must. Superior’s sensors show off industry-leading accuracy to within 0.05% of the selected pressure range and a total error band (TEB) within 0.10% of FSS.
Fastest Response Times
To compliment the accuracy, the time it takes the pressure sensor to update its measurement data is vital for a UAV - the quicker the updated pressure measurements are delivered, the better the drone can maintain its accurate positioning.
While user-configurable, Superior’s sensors enable update rates as fast as 1 millisecond.
Sensor Customization and Flexibility
As UAVs need several pressure sensors, the capability to incorporate just one sensor into the design that can then be customized for each application on the drone is a significant benefit, both from an efficiency and product cost perspective.
The NimbleSense architecture allows the same sensor to fulfill all UAV pressure sensing needs. The sensor can be easily configured for each specific purpose depending on the application. There are a number of features that can be customized, such as pressure range, bandwidth filter and output data rate.
Conclusion
UAVs are extremely sophisticated devices that demand a consistent stream of flight information. Pressure sensors are vital in providing this data, allowing drones to fly without any issues.
Installing differential pressure sensors that cancel out noise, offer exceptionally high degrees of accuracy, deliver the fastest response times and can be tailored for each application will result in better performing products.
Superior Sensor Technology’s differential pressure sensors offer complete design flexibility with unparalleled performance.
For more detailed information about Superior’s solutions for UAVs or to learn how to improve drone products, contact Superior Sensor today.
This information has been sourced, reviewed and adapted from materials provided by Superior Sensor Technology.
For more information on this source, please visit Superior Sensor Technology.