# Distance Assessment by Object Detection--For Visually Impaired Assistive Mechatronic System
## 2 State of the Art
Some outdoor assistance systems for people with disabilities are based on the global positioning system (GPS), which allows the correct assessment with an error of 1 m of the position of the subject's location on the maps used and the speeds of travel in any direction can change [31]. One article that studies a portable system for detecting objects and estimating distance using ultrasonic sensors is [32]. When a person approaches an obstacle, the sensors can only detect the existence of the object in front of the user and, using a piezoelectric buzzer, the state is announced through the sound system of the device. Another article in which the authors studied an ultrasonic radar system that would also allow the identification of moving objects is [33]. The researchers were able to simultaneously evaluate several parameters: the distance from the object, the direction of travel, its speed, and even the shape of the observed object. For complex objects with multiple geometric configurations in paper [34], the researchers developed an advanced system with the help of a high-performance ultrasonic sonar from Polaroid with which it was possible to recognize objects using various information extracted from the echo waves of the sonar, and having a database with different configurations of searched objects. The conclusion was that ultrasonic sonar can be used as a viable system for real-time object recognition in robotics or other applications. The coverage of the field to be studied, depending on the situations in practice, can be done with the help of in-line scanning cameras--cameras that are especially suitable for applications that require both high speeds and high image quality. A line-scan camera reads image data one at a time. It detects fine features such as text lines, barcodes, material characteristics, and QR codes, all of which are possible because it uses optical character recognition (OCR) techniques [35]. A special chapter on the recognition of structures by imaging methods is a specific domain of medical imaging. The methods of obtaining images in this field are based on completely different techniques from those used in common photo or video cameras. Medical imaging is based on deep tissue scanning methods using techniques that use ionizing radiation (CT or X-ray and gamma radiation), based on nuclear magnetic resonance (MRI), or photoacoustic methods based on laser radiation or ultrasound. Images are obtained using sensors that are specifically sensitive to each of these types of radiation [36; 37; 38; 39]. [PERSON] and [PERSON] sought to combine different methods of object detection for greater accuracy, obtaining more types of information through the detection procedure and appropriate measurements in various work environments, thus obtaining more complete coverage of the studied field [40]. An algorithm often used by optic devices is YOLO (You Only Look Once). This algorithm is popular because of its speed and accuracy. It has been used in various applications to detect traffic signals, people, parking meters, and animals. YOLO can also be used in security systems to enforce the security in an area [41; 42; 43; 44]. Its high performance results from multiple improvements, such as YOLOv2, YOLOv3, YOLOv4 (R-YOLOv4, LS-R-YOLOv4 based on the LIDAR sensor). The detection and recognition systems have specialized software, with up to 2500 algorithms (for example, OpenCV--soft open source for Computer Vision). In fact, we used this software and its implemented algorithms in our research, as further evidenced. Based on the knowledge evidenced by the cited references and, not least, based on the expertise and authors' personal experience, two new customized ways of transforming objective reality into information (useful for visually impaired persons) were considered for distance assessment by object detection and recognition.