IIoT-based Solutions for Operator Activity Tracking

From the viewpoint of operators, connection and conversion are the most critical levels of cyber-physical systems as these two levels are responsible for interaction. As smart sensors are key components of solutions for cyber-physical production systems (CPPS), it is necessary to overview what kind of tools are available for monitoring the activity of the operators.

Usually, operator activity is monitored by Radio Frequency IDentification (RFID)-based object tracking. This technology can collect real-time data about the activities of workers (operators) and machines, as well as movements of materials and workpieces. Multi-agent supported RFID systems realize location-sensing systems and intelligent-guided view systems. RFID systems for human-activity monitoring provide an excellent opportunity to observe the work of the operators. With the help of these devices, the whole production process as well as production and waiting times have become measurable online. Based on this information, shop floor control (SFC) and optimization can also be realized.

When the RFID readers are placed such that the duration of the tasks can be estimated, how the production line is balanced in addition to the effect of product changes can be evaluated, and real-time data for OEE (Overall Equipment Effectiveness) calculations provided. The tracking of production can be significantly improved by indoor positioning system (IPS) utilized for localizing the positions of the products and operators.

Context-aware systems require unobtrusive sensors to track each step of the performed task. As wearable sensors are becoming more common, their utilization is also becoming more attractive. However, hand motion-based activity recognition is still challenging and requires the application of advanced machine learning algorithms. Tracking operator activity is a challenging and highly infrastructure-demanding task which should utilize information stream fusion approaches to improve the robustness of the algorithms.

IIoT-based Solutions to Support Operator Activities

The operators not only have to provide real-time information about their actions but at the same time require real-time support in their work. Industrial wearable and communication solutions help to handle this challenge. The previous section showed what kind of techniques exist to collect information from the operator. In this section, potentially applicable feedback technologies will be introduced which are related to the configuration level of cyber-physical systems.

In the early applications production activities required to complete orders were scheduled and managed by shop floor control systems (SFCS). In a hierarchical SFCS (shop, workstation, equipment) was adopted. A vision-based human-computer interaction system was introduced that interacts with the operator and provides feedback. Complex hardware was installed in intelligent environments, equipped with a steerable projector and spatial sound system, to position the character within the environment.

A potential grouping of feedback technologies is the following: fix-mounted devices (e.g. LED TVs), mobile devices (e.g. tablets, smartphones) and wearable devices (e.g. smart glasses). Intuitive displays can reduce the cost of operator intervention as the performance of the operator is improved by the auditory and visual understanding. Visual collaboration systems can provide appropriate instructions for each step of the assembly task.

All groups are used correctly and efficiently, but the novelty of wearable devices compared to the 'simple' mobile devices is the total freedom of movement and free use of limbs. So far some of these only provide a human-machine interface (HMI) and need a (mobile) computer (e.g. a smartphone) to operate, but the tendency is that every device will work separately and can cooperate with other devices through some communication solutions (e.g. LAN/WiFi, Bluetooth). Headsets, VR helmets, smart gloves and smart clothes are examples of types of devices presented. The importance of this area is shown in the statistical increase in the numbers of sales. So far these kinds of solutions have resulted in approximately 5.8 billion in business.

The connections between the categories of Operator 4.0 solutions and potential feedback technologies are available. Which feedback opportunity is expedient is defined by the task in question. For example, in the case of the Super-Strength operator the feedback indicating danger is a critical function. The next step of the design is to select the technology that delivers the information. Danger can be indicated with the help of smart glasses or by a speaker. As soon as the operator hears the warning alarm the danger can be avoided. In the case of smart glasses, the worker can obtain more detailed information about the type and location of risk. The potential applications of these solutions are summarized in the last column of the table.

Some companies have been testing these innovative technologies in manufacturing processes. In every case when these techniques are used, the production process is complex, the quality management is strict, and there is a wide variety of products. The results are impressive because the efficiency improves while the learning time reduces in every observed situation. In the following, some of these solutions will be introduced.

Smart glasses-based augmented reality is used in the manufacturing of high-horsepower wheeled tractors with hundreds of variations by the company AGCO. Presently, 100 pairs of glasses are in use to visualize the next manufacturing step and necessary information for the inspection process. The results in numbers are promising:

• 50% reduction in learning time (in the case of new workers)

• 30% reduction in inspection time (eliminates paperwork and manual upload)

• 25% reduction in production time (in the case of complex assemblies and low volumes)

Similar advantages of smart glasses were reported at DHL which is one of the leading logistics companies in the world. Ten workers who used smart glasses for three weeks managed to distribute 20,000 packages (9,000 orders) leading to a 25% increase in the efficiency of the operators and a reduction in errors of 40%.

Quality and reliability are critical in aerospace manufacturing. Boeing and Model-Based Instructions (MBI) from Iowa State University support the work of the operators. The first solution was designed to show the instructions for the workers. The installation of the desktop MBI was static and there were numerous situations when the operator could not see them during the assembly process. The tablet MBI used the same instructions as the desktop MBI, but it was mounted on a mobile arm. The tablet AR was the same tablet that provided the tablet MBI solution, but the operator could see the real world on the display of the tablet and the software added virtual elements into the video stream. It was observed that the AR technology yielded the best solutions with regard to first-time quality, speed and worker efficiency out of these three solutions.

These benefits are in accordance with what was observed in the introduction of general Industry 4.0 solutions. The examination of 385 published applications shows that the most common benefits of Industry 4.0 are the enhanced efficiency (47%), prevention of errors (33%), reduction of cost (33%), employee support (32%) and minimization of lead time (31%). It is worth noting that the importance of communication (31%), human-machine interfaces (25%) and sensor technology (11% ) were also highlighted.

The review concerning examples of applications showed clearly that the Operator 4.0 concept works in practice and the following advantages were observed: (1) elimination of classical paper-based administration, (2) operators can use their arms freely and receive real-time feedback about the manufacturing process, (3) the duration of training of workers decreases, and (4) the efficiency of production increases and the number of errors decreases simultaneously in all cases.

In summary, operators will be more efficient in smart workplaces, where new opportunities will be available to safeguard their activities and ensure alertness. Production systems will become safer, more controllable and manageable than ever before. A win-win situation will develop in which humans remain an important element.

Operator 4.0 technologies only capable of bringing about these benefits when the manufacturing process is complex and the variety of products is wide. Of course, some advantages can be observed in cases of traditional mass production too, but it is difficult to compensate for the high investment and development costs of these technologies.

Further information: https://doi.org/10.3390/app8091650.