“Sensor fusion makes inclination measurement faster and more precise.”

The topic of sensor fusion and the benefits it offers has been a subject of discussion in the industry for quite some time. How long has TURCK been working on this?

Michael Troska: We have long offered tilt sensors for a wide variety of mobile applications, such as construction vehicles, excavators, cranes, wheel loaders, and other vehicles, as well as in traditional industrial sectors, such as for web tension control in the paper and textile industries. Traditional tilt sensors can successfully handle many tasks, but for certain applications, sensor technologies that are fused together are simply better. That’s why we’ve been working on sensor fusion for some time now and have since introduced our first devices featuring an IO-Link interface and a fusion of a gyroscope and a MEMS accelerometer.

What are the limitations of conventional tilt sensors?

Conventional tilt sensors typically use accelerometers that rely on Earth’s gravity as a reference signal. When the sensor is tilted, it measures a different acceleration because it is no longer level—a factor that is important for calculating the angle. If we encounter interference from acceleration in the application—such as from vibration, shocks, or during acceleration, braking, or cornering—the measurement signal becomes distorted. Most manufacturers use filter functions designed to smooth the output signal and thereby reduce this interference. However, these filters have a major drawback: they make the output signal very slow, and under certain circumstances, the sensor may no longer be able to accurately detect rapid movements because they are filtered out. That is why we developed the fused sensors.

What specific advantages does sensor fusion using a MEMS accelerometer and gyroscope offer?

In addition to the MEMS accelerometer, we use a gyroscope that measures angular velocity in degrees per second. A major advantage is that gyroscope signals are not affected by acceleration. This means that when I combine the acceleration and gyroscope signals using an intelligent fusion algorithm, I obtain an output signal that responds extremely quickly and is also highly precise even in moving applications.

For which applications are tilt sensors with sensor fusion particularly well-suited, especially in dynamic or mobile applications?

I mainly see applications in mobile machinery. Let’s imagine an AGV—that is, an automated guided vehicle—that is constantly in motion. If this vehicle is traveling along a constant curve, for example, then there is a constant disturbance, namely a disturbance acceleration. A conventional tilt sensor cannot filter out this disturbance acceleration. And that’s why I see the best applications, particularly in dynamic mobile applications that require a fast sensor response time.

IO-Link supports high dynamics. Is this another benefit for users in terms of more precise and faster results? If so, why?

We generally rely heavily on IO-Link because, in addition to the actual user data, the protocol can transmit additional information and offers other advantages. In our tilt sensor family, for example, temperature and the number of operating hours are recorded in addition to the angle data. Furthermore, IO-Link also allows users to read application-specific information alongside the sensor data. This is significantly more than an analog interface with 4–20 mA can offer. And because communication via IO-Link is highly EMC-resistant, users can use unshielded, three-wire cables and save costs.

A special feature of your sensor is the LED level indicator. What is it used for?

The spirit level is an installation aid. This means that during installation, the user does not first have to pair the sensor with the controller to receive the process value. The user simply receives direct feedback from the sensor as soon as it is powered by 24 V. The yellow LEDs remain lit when the sensor is within a ±0.5-degree window of the zero position.

What other developments are currently taking place in the field of MEMS sensors, for example in condition monitoring and vibration measurement?

After initially using MEMS cells in our tilt sensors to suppress unwanted vibrations, we now also use them in our CMVT vibration sensors. There, they do the opposite: they precisely measure and output the vibrations. CMVT stands for Condition Monitoring, Vibration, and Temperature, as the sensor measures temperature as well. When the user reads the process data from our sensor via IO-Link—specifically, the vibration velocity—they can easily identify a potential hazard in their machine. If, over time, the vibration value continues to rise or exceeds the limits specified in ISO 10816-3, the user knows that action must be taken before major damage occurs. The sensor data also helps ensure that maintenance is performed at the optimal intervals—neither too late nor too early—since both scenarios cost money. In addition to IO-Link, the CMVT also has switching outputs. The user can therefore easily configure the sensor so that the switching output is triggered when preset limit values are exceeded. This allows, for example, a tower light to be activated that illuminates in green, yellow, or red. All of this is completely self-contained, without any control system integration. Commissioning and operation of the sensor are made easier by our TURCK Vibration Monitor. The tool visualizes vibration and temperature data in real time in any web browser and can be easily used via any TURCK IO-Link master without additional software. This allows the user to view the measured vibration data over a specific period of time; if necessary, the data can also be exported to Excel for further analysis.