# Design and Validation of a Camera-Based Safety System for Fenceless Robotic Work Cells
## 1 Introduction  
As a result of rapid developments, new technologies are being introduced to the industry every day. Rapidly changing the technology and different customer preferences affect the production lines and create predictable or unpredictable changes in final products. Therefore, production systems are required to adapt to these changes [1]. However, flexibility in production is not natural to implement when considering mass production costs. Various production systems have been put forward, such as reconfigurable, fenceless, and hybrid systems [2, 3]. Hybrid production systems involve human-robot cooperation, and they are also called collaborative systems, in which the human factor provides flexibility in the production to maximize operational efficiency [4].  
Fenceless robotic production systems have been emerging for a couple of decades, and they are still being developed. As these systems consist of work cells without any separators between robot workspaces and neighboring fields, some active precautions are necessary to achieve tasks and workers' safety requirements. A fenceless and robot-assisted human-guided production system has significant advantages over full automated ones covered with fences. The most critical obstacle for a successful application in production is the inefficiency caused by the safety requirements [5]. Three-dimensional (3-D) cameras are the most common in image processing-based safety systems according to the current standards [6, 7]. High-cost safety systems using a single 3-D camera have a significantdisadvantage due to the lack of intervention in blind spots. A system using multiple low-cost, two-dimensional (2-D) cameras instead of a 3-D camera may solve this problem. However, it is crucial to make the most suitable choice for the cameras' placements and orientations to scan a broader area eliminating blind spots.  
Currently, the standards described in \"ISO 10218: Robots for Industrial Environments--Safety Requirements\" [8] apply to the primary robot cells' safety operations [9]. If the distance between the robot and the human is below a certain safety level, the robot arm is required to slow down and standstill. Thus, manipulators are prevented from hitting workers. In the designed safety system, there are three safety areas, which are the warning, alarm, and working zones. The robot arm is required to decelerate and stop when entries into the warning and alarm zones are detected, respectively. This study aims to design a safety system using multiple low-cost 2-D cameras for robotic work cells considering current international standards. It proposes an optimal calculation method of camera placements and a design of a safety camera system for fenceless robotic production fields.  
After this brief introduction, some background information is summarized. Design and optimization of the proposed system are followed by a description of the image processing method to avoid blind spots. Next, testing of the optimized design using a deep learning algorithm is presented. The experimental setup design section is followed by results and discussions of the validation tests. The article ends with some concluding remarks.