The review discusses the possibilities of different driving mechanisms and sensors of spherical robots, and a special kind of mobile robots is introduced and discussed. The sensors discussed can expand robots’ sensing capabilities which are typically very limited. Most spherical robots have holonomic characteristics and protect the inner environment using a shell. Today, there are a diversity of driving mechanisms. Therefore, this article provides a review of all of them and identifies their basic properties. Accordingly, many spherical robots have only inner sensors for moving, balancing, driving, etc. However, a few of them are also equipped with sensors that can measure environmental properties. Therefore, in this paper, we propose the possibility of using such sensors as cameras, LiDARs, thermocouples, and gas sensors, which can be used for special purposes underground, for example, in mines, underground tunnels, or road tunnels. After combining all components are combined, it is possible to design a special type of spherical robot designed for underground exploration, such as accidents in mines or road tunnels.

Many modern vehicles today are equipped with an on-board e-call system that can send information about the number of passengers in the event of an accident. However, in case of fire or other major danger in a road tunnel, it is very important for rescue services to know not only the number of passengers in a given vehicle that has an accident and called help via e-call but how many people are in the tunnel in total. This paper deals with the issue of passenger detection and counting using the TPH3008-S Thermal camera and the VIVOTEK IP7361 IP Cameras noninvasively, i.e., the cameras are placed outside the vehicle. These cameras have their limitations; therefore, we investigated how to improve conditions and how to make detection better for future work. The main goal of this article is to summarize the achieved results and possibilities of improvement of the proposed system by adding other sensors and systems that would improve the final score of passenger detection. The experimental results demonstrate that our approach has to be modified and we have to add additional sensors or change methods to achieve more promising results. The results, findings and conclusions might be later used in tunnels and highways and also be applied in telematics and lead to better, safer road transport and improvement of existing tunnel systems sustainability by utilizing resources in a smarter way.

Applications of safety-related control systems demand reliable and credible inputs from physical sensors, therefore there is a need to extend their capabilities to provide a validated input with high availability. Our main idea is to insert virtual sensors between physical sensors and the control system’s logic. The created solution can validate the values of real sensors and with the use of multiple virtual sensors we can achieve high availability in addition, therefore our solution is entitled as a virtual redundant sensor. It works by the digital twin’s concept and uses fusion function to calculate validated results. The fusion function is used to transform the measured values from the physical sensors according to designed numerical models. The selection of a numerical model with assigned fusion functions can be performed via the WEB-based graphical user interface. Proposal of the numerical model is created and validated on the experimental workplace with emulation of physical sensors and MQTT integration (smart IoT sensors). The results of testing have shown that our solution can be applied to validate the values of physical sensors. Proposed fusion functions calculated results according to the selected model in all cases, while non-standard cases were handled according to our definition. In addition, the high availability concept with a group of two virtual sensors has proven fast recovery and availability of results for safety-related applications as well.

Each safety-related function must be implemented with a defined safety integrity level (SIL) if the control system implements safety-related functions (SFs) in addition to the standard control functions. The required SIL of the SF depends on the quantity of the risk associated with the failure of this one SF. The SIL against random failure can be expressed through the dangerous failure rate of the SF for an electronic safety-related control system (ESRCS) operating in a continuous mode of operation. The proof must be provided (among other things) that the SIL requirements for the individual SFs are met so the ESRCS can be accepted and implemented. The assessment of the impact of random failures on the SIL of the SF must be performed using the quantitative analysis method. This paper describes the procedure and derives equations for evaluating the impact of random failure on SIL of the SF using Markov chains with two absorption states. The achieved results are presented for SF implemented by ESRCS with dual architecture based on composite fail-safety technique.

The implementation of safety functions, in contrast to ordinary control functions, requires a different approach to the design of the hardware and software of the control system. The reason for the different approaches is that each safety function must meet the required Safety Integrity Level (SIL). This has two aspects: safety integrity against random failures and safety integrity against systematic failures. Hardware is primarily related to random failure safety integrity, and software primarily to systematic failure safety integrity. The focus of this contribution lies in the design of a method that will allow the software of a safety function for industrial applications to be designed using a model of the functional behavior of this function. Since commercially available programmable logic controllers (PLCs) with a defined SIL level (so-called safety PLC) do not support such solutions, a dual architecture based on standard PLCs, including their software control, is proposed in the paper. Such an approach will make it possible to significantly limit the occurrence of systematic errors in the creation of application software, as well as to test the created application software and reveal deficiencies that arose in previous phases of the life cycle (e.g., when specifying safety functions). To implement the method proposed in this paper, a dual architecture created from the safety PLC Simatic series S7-1500 is used. With the help of this architecture, the safety function “Muting” is implemented.

The safety of small CNC (Computer Numerical Control) milling machines is typically ensured through organizational measures. However, when such a CNC milling machine is used in a manner that may involve contact with untrained individuals or children (e.g., for demonstration purposes), it becomes essential to ensure safety through appropriate technical measures. The required safety can be achieved by implementing safety functions to mitigate identified hazards. This paper addresses the design and application of a Safety-Related Control System (SRCS) that implements safety functions for a small CNC milling machine. A notable aspect of this implementation is that commonly available sensors (e.g., optical barriers) with a defined Safety Integrity Level (SIL) are unsuitable for small CNC milling machines in size, cost, and performance parameters. For instance, these sensors might fail to detect the entry of a child’s hand. Consequently, it was necessary to design suitable custom sensors for realizing an SRCS. The paper also demonstrates the achieved SIL for the implemented safety functions.