3.1 Structural design
The existing construction robots generally have problems such as large volume and heavy mass, and their functions are also affected. To reduce or avoid functional impairment, the mechanical structure can be simplified or replaced with lightweight materials, such as: Jianghong Sun et al. (2015) proposed a 2-PSS&PPU parallel micro-robot mechanism based on the workspace principle of the parallel mechanism. This mechanism has a simple structure. Makhsuda et al. (2017) injected nylon 66 composite material containing 70% glass fiber into the back cover of automobile reducer to replace the original aluminum alloy back cover. The experiment has proved that the composite material contains all the properties required by the aluminum alloy back cover, and has advantages of lower cost, lighter weight and higher hardness.