When people refer to the Internet of Things (IoT), they imagine a network of ‘smart’ devices that make life more comfortable and convenient. A typical example is a healthcare product that can track how many calories have been ingested and then burned through exercise, accompanied by a reassuring graph of the wearer’s heart rate. Another example is the smart home where specific music tracks can play on command, lights can be turned off in unoccupied rooms, and temperature can be remotely adjusted to suit the occupant.
But the IoT is moving into the industrial arena too, with networks that can collect data to monitor and control production lines, inventory, and energy use for sustainable, reliable manufacturing. As part of the Industrial IoT (IIoT) these models rely on devices (or nodes) such as thermostats, or optical sensors at the edges of the network, receiving and sending data that a central system can analyze and act upon to, for example, optimize a process.
Today, sensors are typically positioned on the outside of equipment where access is easier, but what if the sensors were embedded into the machine’s actual moving components when it was manufactured or serviced? The data gathered from an embedded sensor would offer far more detailed information about what was happening inside the machine, practically in real time, dramatically enhancing how well a process was controlled and improving machine maintenance. But even with today’s compact, power-frugal, and inexpensive wireless sensors, is it really possible to integrate the device into the very fabric of a machine and then expect it to reliably transmit information for months or even years? A team of researchers at Dresden University of Technology (TU Dresden), Germany, have been finding out.
Material gain
The TU Dresden team has been experimenting with wireless sensors embedded into the fiber- reinforced material used to make industrial brake discs, turning the discs into rotating IoT nodes.
The brake discs are critical for safety applications in industrial equipment. An example is in elevators, where the discs are used to control the speed of the ascending car, protect against unintended movement, and maintain the car’s position when it stops at each floor. In addition to difficult access, measuring specific system parameters, such as vibration or wear, traditionally requires the addition of expensive hardware, such as torque shafts. Embedded wireless sensors can do away with all that.
During the experiments, a Nordic Semiconductor nRF51 Series Bluetooth LE System-on-Chip (SoC), paired with MEMS-based sensors to measure acceleration in the x, y and z axes, three-axis gyroscopes, magnetic field sensors, and temperature sensors, were combined with a power supply to monitor the condition of the electromagnetic braking system. An important consideration was that the integration of the electronic components would not affect the mechanical performance of the brake disc material, which has to operate reliably and safely in harsh, dirty industrial environments at high temperatures.
Sven Grunwald and Bernard Bäker from TU Dresden developed a low-cost method to embed the wireless sensors into the fiber-reinforced material to measure three parameters: Brake disc wear, the condition of the system in which it was used, and air gap detection between the disc and the brake-activating magnetic anchor.
The data from the wireless sensors can also be used to remotely report on the status of the brake and identify the best time for maintenance or repairs while minimizing disruption.
Integration cuts costs
The “always-on” nature of the IoT demands low power consumption to extend battery life. Nordic’s ultra low power wireless SoCs feature microampere average current consumption leading to years of battery life (depending on the application), an important consideration in an application where the battery can’t be replaced and hence must last the lifetime of the host product.
The Nordic nRF51 Series SoC employed by the university team used a Bluetooth LE RF protocol “stack” certified to the Bluetooth 4.2 standard. This version of the standard supports a channel dedicated to IPv6 communication. With some additional software and an IoT router, the sensor could send data directly to a Cloud without human intervention.
The system described by Grunwald and Bäker is also upgradeable to Bluetooth 5 (using Nordic’s nRF52 Series SoCs). This version of the Bluetooth LE standard increases the range of wireless connectivity or doubles the bandwidth achievable compared to Bluetooth 4.2 without any power consumption penalty. Nordic has also released a Software Development Kit (SDK) that enables designers to take advantage of the recently-released Bluetooth mesh standard - making it much easier to integrate multiple embedded industrial wireless sensors into a network, enhancing the robustness of the system. This is again an important factor when there is no possibility of replacing a faulty sensor.
Nordic’s nRF51 SoC integrates the 2.4GHz radio with an ARM Cortex M0 processor, 256 kB/128 kB Flash and 32 kB/16 kB RAM, plus a power management system. This high level of integration reduces the component count in the embedded system to minimize the bill of materials, simplifies design and assembly, saves space, and increases reliability. The SoC provides bidirectional Bluetooth LE wireless connectivity between the brake’s embedded sensors and host system, or a wireless router (and then the Cloud). Updates can be seamlessly implemented using the SoC’s over-the-air device firmware update (OTA-DFU) capability.
After verifying that the electronics’ integration into the composite material did not affect its properties, the brake components were tested. Grunwald and Bäker concluded: “The integration of electronic, IoT-enabled systems, based on a low-cost [Bluetooth LE] SoC and the required sensor electronics into a composite material is [successful],” despite the mechanical stresses and high temperature operation of the brake disc. They reported: “Defect-free integration of the measurement unit, as well as typical end applications, such as shock detection, speed measurement, and temperature monitoring, were [also] successfully realized.”
Grunwald and Bäker concluded that their system had proven itself capable of “monitoring performance parameters and condition monitoring of the brake disc, as well as fulfilling predictive maintenance tasks within the field of electric drives, according to Industry 4.0 [‘smart factory’]”.
The idea can be extended to other machine components. “It is important to mention that [the experimental] applications represent only a small excerpt of possible and useful applications,” noted Grunwald and Bäker.
Vision becomes reality
John Leonard, a Product Marketing Manager with Nordic, has speculated on the new business models that the IIoT can support. He envisages business models where rather than constantly fighting a battle with unplanned repairs of broken-down machinery, companies can reduce costs by planned maintenance where wear has been reported by wireless sensors. In addition, Cloud servers could use sensor data in algorithms to predict high and low periods of demand, with the system’s operation adjusted accordingly to save energy.
The German research shows these models can be refined by moving the sensors into the very heart of the machine, and in doing so, designers can accelerate the advent of the smart factory. With cost-effective wireless SoCs and sensors embedded directly into components and connected via a mesh network to the Cloud, powerful servers can, for example, determine the location of underused equipment and process bottlenecks to adjust the speed of the process accordingly. In addition, every part of an automated factory can be monitored for wear and tear to pinpoint maintenance needs, slashing production stoppages due to equipment failure.
This vision of the smart factory is rapidly turning into reality, according to consultant PwC. In a recent report (Industry 4.0: Building the digital enterprise) the company explains that Industry 4.0 investments are already significant and global industrial products companies will invest $907 billion per year through to 2020. PwC suggests: “The major focus of this investment will be on digital technologies like sensors or connectivity devices, [as well as on software and applications like manufacturing execution systems].”
Bluetooth LE, initially targeted at consumer peripherals, has rapidly adapted with security, IP connectivity, range/throughput, and mesh networking enhancements to become a foundation technology of the IIoT. In turn, the technology is helping power Industry 4.0, the revolution that will see today’s manufacturing facilities transformed into the highly-efficient, highly-sustainable smart factories of tomorrow.