## 4. Accident Prevention System for Heavy Duty Machines--A Case Study of Small Demolition Robots
### HMI System for Accident Prevention
By offering additional functionalities, it would be possible to create a multi-part non-haptic feedback device with this safety equipment. Figure 14b depicts a possible solution for an intelligent safety helmet with additional accident prevention features. Apart from adding systems described in the following paragraphs, the helmet can be filled with advanced light cork liner [33; 34; 35] which reduces the energy upon impact. The helmet protects the wearer mainly from head injuries resulting from falling or airborne items or from hitting static obstacles [33; 34; 35]. Such a safety helmet is classified as personal safety gear by (national) safety regulations and is mandatory in most operational environments during deconstruction projects. Depending on the preferences of the company, the color of the helmet can also indicate the affiliation of a worker to a special department or that he or she is qualified to use special machinery, e.g., a demolition robot. Additionally, the safety helmet also serves, directly or indirectly, as storage for other components that the operator needs, e.g., safety goggles and ear protection. To supply these modified safety components with voltage and current, a battery and a Bluetooth/WIFI-device should also be installed, to enable communication between all components and reduce the hazard of injuries, such as strangulation by tethered components. The second part of this essential safety gear are safety goggles which protect against eye injuries caused by dust, small particles, and airborne items as well as similar hazards to eyes in working environments described earlier. Safety goggles are also classified as personal safety gear and need to be worn in deconstruction projects such as house demolitions. An advanced system could be supplied by means of augmented reality glasses or Virtual Reality goggles which could provide the operator with additional data [36; 32]. Since in warm and humid surroundings conventional goggles tend to become scratched and cause a foggy view, especially if the operator wears glasses, a shield could be used alternatively instead of goggles. A modification of the goggles or the shield consisting of a frame made of acrylic, or a similar light-conductor, illuminated by LED lights could serve as a visual warning system, e.g., by blinking, which is always visible and does not directly blind the operator or obstruct his or her view. The power source for this application lies in the battery stored inside the helmet. Ear protection could serve as the third component in such a non-haptic feedback system [31]. Its function is to prevent ear injury caused by high levels of noise and frequencies or airborne particles and items while working in a hazardous environment. Just as with the safety helmet and goggles, ear protection is classified as personal safety gear and needs to be worn when working in an environment where noise exceeds a given level. Since there is a foreseeable noise reduction by such ear protection, there are some advantages in the actual application of an acoustic warning signal in this component. By installing a headphone inside the ear protection, a warning signal could be emitted at a level that is deemed safe in relation to the noise level of the working environment. This is also convenient for the operator and makes the acoustic warning signal emitted by the remote control or the robot unnecessary, which also helps to reduce the noise of the working environment. Additional features of the non-haptic feedback device, such as radio communication are also possible, but are not considered in this paper. A combination of these technologies is recommended in designing tailor-made products that respond to specific expectations of end-users and are offered as a list of accessories and features. In this context, what is equally important is that applicability is not reducible to technical issues alone. It should be viewed in the context of technical requirements, its technical applications in the existing system, and, most importantly, the user's approval.