A trajectory-based explicit reference governor for the laying activity with heavy pre-fabricated elements

Introduction In recent years, robotic solutions for the construction industry have attracted the attention of various researchers and the market. Several robotic systems have been proposed for the construction of buildings involving heavy suspended elements. However, most of the solutions proposed so far did not pass the prototype status. Objectives The first objective of this paper is to describe an innovative bricklaying concept based on a lifting mechanism and a lightweight robotic arm to handle and place heavy suspended objects ensuring a high level of precision during the planned operations. The second objective is to design a constrained control strategy that belongs to the so-called “Explicit Reference Governor (ERG)” theory, to properly control the proposed robotic system ensuring correct and safe cooperation. Methods First the mathematical model of the system under consideration is developed. Some mechanical properties of the proposed multi-robot system are analyzed. Then, the resulting model is exploited to design a constrained control strategy to ensure: (i) the correct cooperation between the robot and the lifting mechanism to move the payload to a desired position; (ii) the safe cooperation between the two sub-units so that the robot will never be overloaded. Results To demonstrate the feasibility of the proposed concept and the effectiveness of the proposed control solution, realistic CAD-based physical simulations are presented. Through simulations, we are able to demonstrate that the multi-robot system is capable of correctly positioning a 100 kg block. The proposed control scheme ensures that the constraints of the system are always satisfied and the robotic arm is never in an overload situation. Conclusion This paper proposed a constrained control scheme based on the ERG framework for controlling a mechanical system to place heavy prefabricated elements. In the first part of this paper, a mathematical model of the overall system is derived, then the constrained control scheme is described. Simulation results show that the proposed control scheme is able to fulfill the constraints of the system while moving the suspended object to its final position.