Precise truss assembly using commodity parts and low precision welding

Abstract

Abstract-We describe an Intelligent Precision Jigging Robot (IPJR), which allows high precision assembly of commodity parts with low-precision bonding. We present preliminary experiments in 2D that are motivated by the problem of assembling a space telescope optical bench on orbit using inexpensive, stock hardware and low-precision welding. An IPJR is a robot that acts as the precise "jigging", holding parts of a local assembly site in place while an external low precision assembly agent cuts and welds members. The prototype presented in this paper allows an assembly agent (in this case, a human using only low precision tools), to assemble a 2D truss made of wooden dowels to a precision on the order of millimeters over a span on the order of meters. We report the challenges of designing the IPJR hardware and software, analyze the error in assembly, document the test results over several experiments including a large-scale ring structure, and describe future work to implement the IPJR in 3D and with micron precision.

Truss assembly and welding by Intelligent Precision Jigging Robots

“…A system consisting of an IPJR and the LSMS successfully assembled and welded a truss using stock titanium materials, and improving on the methods and practicality of the wooden experiment from [1], [2] . The LSMS was augmented with a welding gun and a lifting plate for the experiment.…”

“…A jig is the scaffolding used to hold components in place while the welding is performed. Intelligent Precision Jigging Robots (IPJR), introduced and described extensively in [1], [2], hold multiple components in a precise pose for welding, enabling an external, imprecise agent to manipulate, assemble, and weld components made of stock materials. IPJRs are autonomous, with a comptuer containing the assembly sequence, a pose controller, algorithms for adjusting for errors, and communication hardware.…”

“…The initial prototype [1], [2] enabled the assembly of flat wooden trusses to a precision of under 1 mm, as measured on the strut lengths, despite using simple, imprecise tools such as glue guns and hot glue. This work demonstrated that IPJRs and a coarse manipulator could work together to assemble structures made of simple elements to a high precision, thereby negating the need for the high cost associated with high precision manufacturing.…”

Assembly path planning for stable robotic construction

“…We intend to test the method presented in this paper on a truss assembly experiment using the Intelligent Precision Jigging Robot (IPJR) paradigm [25], [26], the most recent version of which is shown in Figure 5. Previous IPJR experiments were performed with 2D trusses, so stability was not a concern.…”

Multi-scale assembly with robot teams

“…Rather than using mobile robots, they propose a static system which moves the constructed structure as new layers are added. Komendera et al (2014) investigate approaches to roboticized tools which can be used to achieve precise assembly of truss structures. Rojas and Peters (2012) develop different controllers for assembly operations and analysed their relative performances.…”