Hardware-Software Co-Design for Energy-efficient IIoT Systems

We encounter sensor systems in many areas of everyday life: at home, in agriculture, and in industrial production. Advancing digitalization requires flexible, retrofittable, and networked sensor solutions – every industry has specific requirements that must be met.

An important prerequisite for the economic use of IIoT systems is their energy efficiency. RealIZM spoke with Carsten Brockmann, head of the Sensor Nodes & Embedded Microsystems working group at Fraunhofer IZM, about how hardware-software co-design contributes to optimal system partitioning of IIoT systems and their performance review.

The Industrial Internet of Things

IIoT stands for »Industrial Internet of Things« and refers to a network of physical objects (»things«) that are equipped with sensors and software. These objects connect to other devices or systems via the Internet to collect and exchange data in real time. IIoT systems equipped with wireless sensors have three key features – they transmit data wirelessly, can be easily retrofitted without disrupting ongoing processes, and can be installed in a decentralized (distributed) manner as well as in hard-to-reach areas.

Possible applications of IIoT systems in condition monitoring

One important application of IIoT systems is condition monitoring in industrial manufacturing processes. This improves  both the understanding of the processes (process mining) and the ability to perform predictive maintenance. Identifying problems early on, before downtime or system failures occur, improves quality assurance in industrial manufacturing and also increases the safety of civil infrastructure.

For example, motors in industrial plants can be monitored for temperature and vibration, , machine fill levels can be checked, and the temperature and humidity in storage rooms can be controlled. The condition of bridges can also be monitored, allowing  their maintenance to be planned in advance, or the control of wastewater treatment and the supply of drinking water.

The MicroMole research project developed an energy-autonomous sensor system to monitor wastewater discharges.  For example, a sensor ring can be used to measure the flow rate in a gravity sewer.

The digital transformation of the energy sector and infrastructure is an integral part of the energy transition. In order to be able to respond flexibly to the ever-increasing supply of renewable energy and the partly displaced demand, intelligent control of energy flows is necessary.¹

ASTROSE® overhead line monitoring is an IIoT system consisting of wireless sensor nodes that monitor high- and extra-high-voltage power lines. By continuously recording various measured values in the voltage fields, grid operators can optimize transport capacity, identify critical conditions more quickly, and collect long-term operating data.

From left to right: MicroMole research project: Sensor ring for use in wastewater treatment plants; ASTROSE®: Wireless sensor network for monitoring high-voltage and extra-high-voltage power lines | © Fraunhofer IZM I Volker Mai

Energy efficiency is a fundamental prerequisite ment for the economical use of IIoT systems. The aim is for an IIoT system to operate without maintenance for as long as possible. Every battery replacement and every maintenance operation is time-consuming, resource-intensive, and costly. Additionally, many applications only make sense once they have been in operation for a certain minimum period of time. Whether an IIoT system is energy self-sufficient or battery-powered is assessed on a case-by-case basis.

Hardware-software co-design for optimal system partitioning

»We are system integrators and designers and take a holistic view of IoT systems,« says Carsten Brockmann, summarizing his area of responsibility. From the energy supply and data processing of the IIoT system to communication, he and his team develop a conceptual understanding of the respective system and its application scenario. Together with the clients, they determine sensible system integration and partitioning.

Optimal system partitioning is crucial for the energy efficiency of an IIoT system. Errors in partitioning, such as outsourcing functions to the software when they could be implemented more efficiently in the hardware, negatively impact the system’s overall energy efficiency.

In hardware-software co-design, two important development strands of go hand in hand. Brockmann and his team examine how the system partitioning should be configured for a given application and which functions can be mapped in hardware and software. Their goal is to identify the interactions between these two sections in order to develop the most energy-efficient IIoT system possible.

Carsten Brockmann’s working group brings together experts from the fields of hardware and software, including electrical engineers, computer scientists, and technical computer scientists.

Ways to increase the energy efficiency of IIoT applications

»For us as system integrators, energy efficiency means implementing as many functions as possible with the lowest possible energy consumption,« explains Brockmann. There are various approaches to improving the energy balance of IIoT systems. For instance, fast data processing and robust transmission can increase efficiency. One example of this is the IoT protocol mioty® developed by Fraunhofer IIS.

Another option is to optimize the ratio of active measurement and processing time to idle time, allowing the system to enter idle mode for extended periods. This deactivates unnecessary components, reducing their power consumption to a fraction of the normal level. This approach is particularly suitable for operations that do not require continuous measurement.

The greatest efficiency gains are achieved through dynamic system configuration. Hardware-software co-design involves developing architectures that enable functions to be switched on or off as needed. Brockmann compares this process to cylinder deactivation in cars: in powerful engines, certain cylinders are deactivated during partial load operation to reduce fuel consumption. These cylinders can be activated dynamically as needed.

Fraunhofer IZM has developed a technology demonstrator that can be configured according to customer specifications. The energy-efficient, battery-powered SWARMY sensor-actuator platform has integrated sensors and external interfaces for connecting strain gauges. SWARMY measures vibrations and temperatures on annexes and components and records parameters such as acceleration, angular acceleration, light, humidity, pressure, and distance. The measurement intervals and sensitivities can be customized.

Modular multi-sensor platform: Configurable sensors for various measurement scenarios with local data processing and wireless communication interface | © Fraunhofer IZM I Fabian Mathar

Fraunhofer IZM relies on machine learning to boost the efficiency of IoT systems. This requires significantly less power than static optimization methods. A self-learning AI modifies the system’s operating behavior. It runs on the system and uses specific, predefined performance data (e.g., data throughput, value history) to determine how to adjust the system’s behavior to achieve maximum energy efficiency while maintaining the same functionality.

Benchmarking and performance review of IIoT systems

Energy-efficient IIoT systems are characterized by the fact that they do not heat up. Heat means energy loss. This heat is often not noticeable in certain performance classes. Power/voltage profiles can be used to determine power requirements and compare them with functionalities. »This enables us to benchmark. We can compare the tested system with a reference system in terms of energy efficiency,« explains Brockmann.

Measurement and analysis of the performance profile of systems and assemblies | © Fraunhofer IZM I Volker Mai

Although performance tests are well established for computer systems, benchmarks for IoT systems are only available in isolated cases. As part of the »Green ICT« research project, Fraunhofer IZM examined various IoT system architectures and determined preliminary reference values for energy efficiency. The challenge lies in the system’s diverse functions and characteristics. The energy requirements of these systems vary greatly and must be made comparable.

Researchers have developed an internal tool that can record the load profiles of IIoT systems with varying degrees of granularity and quickly extrapolate them to extensive operating scenarios. This makes it possible to estimate the effects of development decisions early on or to carry out comparative evaluations of existing products. Additionally, load scenarios can be compared with energy supply options to achieve a holistic view and optimize the source and load sides of a system, if necessary.

Example from the Excel tool, which can be used to record and evaluate the energy consumption of different operating modes of IoT components or modules and scale them to operating scenarios. | © Fraunhofer IZM

Fraunhofer IZM collaborates with clients to draw up project specifications. Thanks to the benchmark, researchers have access to a library of reference values. Tests and validations are carried out throughout the project. These validations are important because they ensure that the initial estimates made in the specifications are accurate.

»Our goal is to set the global benchmark for energy-efficient IoT systems. Every research project brings us closer,« explains Brockmann. All findings are continuously developed in a generic and modular manner. Brockmann and his team are working on a technology platform that demonstrates the progress in system architecture. Specific solutions can be extracted from this platform. However, the focus remains on further development.

Current research projects to improve energy efficiency

»We try to be open to all technologies,« explains Brockmann. In everyday research, however, work on industrial applications is often closely linked to future product developments. Marketable technologies are frequently used to enable rapid prototyping and quick industry adoption. Additionally, IoT systems undergo rapid development cycles and must be marketable quickly.

The LoLiPoP-IoT research project is investigating how to implement IoT systems as energy-efficiently as possible. The goal is to research and develop energy harvesting solutions for sensors with a very long service life. To this end, 12 different use cases from various sectors (logistics, maintenance, production) are being investigated.

Fraunhofer IZM is collaborating with Fraunhofer IIS on this project to develop energy-autonomous sensor nodes for monitoring the condition of bulk materials in large silos. Retrofitting the necessary infrastructure is usually too expensive. The sensor nodes are designed to prevent fermentation or self-ignition effects during the storage of certain goods and ensure that the quality of the stored goods is not impaired. If necessary, an alarm should trigger automatically, releasing N2 gas or extinguishing foam as a preventive measure. Methods used to date focus on detecting smoldering gas residues. However, this is too late for a preventive response, as the avalanche process has already begun.

Lifetime and sustainability of IoT systems

Another focus of the researchers at Fraunhofer IZM is to provide information on the lifecycle of IoT systems in order to determine their carbon footprint and estimate their lifetime. The »Sensor Nodes & Embedded Microsystems« working group collaborates closely with the »Environmental & Reliability Engineering« department at Fraunhofer IZM. Environmental experts in electronics perform environmental audits and analyze the energy required for the production of assemblies, transport routes, maintenance, and disposal.

They also study failure mechanisms to predict the reliability and longevity of electronic devices. Brockmann estimates the achievable service life of IoT systems to be at least 10 years. This includes the service life of the technology and components, balanced energy usage, and system reparability.

»Our services are aimed at industrial and logistics companies, maintenance teams, and environmental authorities looking for energy-efficient IoT systems that meet specific criteria such as maintenance-free operation,« Brockmann summarizes. »We also offer the option of further developing existing IoT systems to make them more energy-efficient and extend their service life.«

From idea to concept: Example of possible components of an IoT device | © Fraunhofer IZM

Synergies between Fraunhofer IZM and Fraunhofer IIS in the development of energy-efficient IoT systems

Fraunhofer IZM is collaborating with Fraunhofer IIS to improve the energy efficiency of IoT solutions. Fraunhofer IIS develops components such as energy harvesters and highly efficient radio receivers, while Fraunhofer IZM develops integration solutions for IoT systems.

»We know how and in which systems components can be used effectively and where they may not be useful – that is our area of expertise,« says Brockmann, describing the focus of his working group. »We have already integrated and implemented many wireless solutions, protocols, and standards, and we understand how they behave in terms of energy efficiency for specific applications.«

Source:

¹ https://www.energieforschung.nrw/erfolge-und-stories/digitale-netze