# A Review on the Prospects of Mobile Manipulators for Smart Maintenance of Railway Track
## 8 Conclusions  
Railway is an environmentally friendly, safe, and reliable public transport system. The track is the most critical part of a railway asset management system, which requires rigorous maintenance to ensure a safe and comfortable travel experience. The railways are older than the automotive or aerospace industries yet do not use modern robotic technologies in a widespread fashion. As the demand for trains is increasing, more attention is required to upgrade current maintenance technologies using robotic and autonomous solutions. Although a small number of railways robots have been developed, the vast majority do not have manipulation capability and only focus on inspection tasks without repair capability.  
The feasibility and benefits of using mobile manipulators for maintenance tasks across various industries have been found throughout extensive research in the past few decades. An extensive literature review has classified mobile manipulators into different categories based on the base robot type and application areas. Although most mobile manipulators are based on ground robots, researchers are looking into other types of base robots, such as aerial, underwater, etc. The high-voltage power transmission line is the most significant area of application for application of mobile manipulator. However, mobile manipulator usage is increasing across the nuclear reactor, aerospace, agriculture, and construction fields.  
With adequate design, instrumentation, computational algorithms, and workflow frameworks, the usability and benefits of mobile manipulators can be successfully adopted in the railway track maintenance activities. Previous studies have proved the economic and safety benefits of modern robotic technologies in different applications in railway [48; 71; 158; 159]. Hence, the usage of intelligent mobile manipulators for track maintenance will provide robust, reliable, and greener support for a mass transportation system which can increase human safety and asset digitalization.  
Nonetheless, improved navigation methods in GPS-denied areas and local data storage capabilities are required to achieve deployment in remote areas. Additionally, safety and security measures are demanded for successful operation. Moreover, the design of maintenance is a desirable criterion for cost optimization. Finally, the hardware and software of robots should be capable of verifying the completed task by following the railway standard.  
Most of the current mobile manipulators are not designed to consider railway applications. Hence, more research is required in the future to design and fabricate railway-compatible mobile manipulators. Furthermore, as many of the railway sites lack good signal for data transfer-, teleoperation-, and mixed reality (MR)-based mobile manipulation in railway track environment can be potential future research. Besides, railway track maintenance requires different types of tools. Thus, self-reconfigurable end-of-arm tools constitute another research prospect in the field of mobile manipulators.  
Conceptualization--M.R.; validation--M.R., I.D.C. and H.L.; formal analysis--M.R.; writing--original draft preparation--M.R. and I.D.C.; writing--review and editing--H.L., I.D.C., A.S., A.H. and R.A.; supervision--I.D.C., A.S., A.H. and R.A.; funding acquisition--I.D.C. and A.S. All authors have read and agreed to the published version of the manuscript.  
The work was partly supported by the Shift2 Rail Joint Undertaking under the European Union's Horizon 2020 research and innovation program under grant agreements No. 881574 and No. 826255. Additionally, this research was directly supported by Network Rail Limited.  
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The authors declare no conflict of interest.