## 5 Conclusions  
This paper outlines the architecture of a novel robot designed to patrol in the workspace. The robot has four functions: independent patrolling, signing in at inspection points, the detection and tracking of intruders, and remote backup of data to facilitate real-time monitoring and user queries. The robot receives from an SVS depth information pertaining to the environment for use in the identification of a suitable path to follow. Inspection point markers encountered along this path cause the robot to veer off the path to check-in. Upon arrival at the inspection point, the number of the RFID tag at that point is recorded. After signing in, the robot rotates CCW and continues its patrol task. In the event that an intruder appears within the FOV of the SVS, the skeleton of the intruder is identified according to the function of the openNI library. The intruder is subsequently tracked and imaged until the intruder moves beyond the viewing window. All data recorded during this encounter is uploaded to the server, to enable monitoring in real-time and facilitate subsequent queries of historical data. Several experiments verify the efficacy of the proposed algorithm. Figure 13: The recorded images of intruder recorded by robot. For comparison to other guard solutions, e.g., security cameras, as mentioned in the introduction, sweeping robots have gradually become commonplace in every home or workspace environment. If there is a simple and low-cost method that can increase the patrol function on traditional sweeping robots, it will effectively solve the problem of home security. In addition, the prices of the retrofit devices (SVS and RFID sensors, etc.) on sweeping robots of the proposed system are lower than N.T.D. 5000, but the prices of a security camera is generally higher than that. Secondary, mobility and randomness are the two key points of the patrol system. For the proposed system, there are two functions can achieve these objectives, one is path-free autonomous patrol, and the other is intruder following. The path-free autonomous patrol function creates a random patrol path which can avoid intruders to find possible flaws for planned paths in advance, and the intruder following function can avoid blind spots caused by furniture, and then record more image information of intruders. On the other hand, a security camera is usually installed at a fixed location, and its rotation degree is limited. Therefore, more cameras need to be installed to cover all monitoring ranges, and lack of mobility. Moreover, information security and privacy are issues that everyone values in recent years. For the proposed system, the user cannot get the image information directly from the patrol robot. The recorded images are saved in a server at first. Users need to login the server to get access to watch the records. Generally, a server has a higher level of information security protection. On the other hand, a security camera has a convenience that users can monitor remotely and directly. However, now a day, \"security camera has been hijacked or hacked\" is heard from time to time, and these events will cause users to concern about the security of the patrol by security camera. Summarily, the proposed system is not convenient for users to view patrol results, however, it has a lower price, better path randomness, better mobility, and more information security and privacy. The comparison results are shown in Table 2.  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/10/3/974/s1](http://www.mdpi.com/2076-3417/10/3/974/s1)]([http://www.mdpi.com/2076-3417/10/3/974/s1](http://www.mdpi.com/2076-3417/10/3/974/s1)), Video S1: The recorded color images and the depth information from the SVS during the patrol task. **Author Contributions:** Developed the idea of the proposed method and directed the experiments, C.-W.L. ; fabricated the devices and performed the experiments, C.-Y.C. All authors have read and agreed to the published version of the manuscript.