Force-egulated Impact Control of a Reinforced Concrete Box Culvert Chipping Robot

A reinforced concrete box culvert (RCBC) is a structure that allows water to flow under a road, trail, or similar obstruction. Currently, many RCBCs are located under cities and roads. If a ground subsidence occurs owing to the sudden collapse of an RCBC, it could result in a serious accident. Therefore, continuous management and maintenance work should be performed to prevent RCBC collapse and accidents. Typical RCBC maintenance work consists of detecting damaged parts, concrete chipping, etc. In particular, the chipping process in which workers remove the deteriorated concrete of RCBC by using heavy equipment has a high risk of musculoskeletal injury. Moreover, because poor working conditions in this process can cause major accidents, the process is regarded as hazardous, and even skilled construction workers avoid undertaking this work. Therefore, the concrete chipping process is one of the construction operations that urgently require the application of a construction robot. In this paper, the RCBC chipping robot is introduced as a solution to this problem, and the force-regulated impact control for improving quality of the chipping work is described. The RCBC chipping robot is developed to perform the concrete-chipping process instead of workers. The robot consists of a robot mobile platform for locomotion, a robot manipulator, a chipping tool installed at the end of the manipulator, and a robot motion controller. To perform the chipping process, the chipping robot moves to the work area through the robot mobile platform. Then, the robot manipulator follows the trajectory for the process, and the chipping tool strikes the deteriorated concrete. Trajectory generation and control for these operations are performed through the robot motion controller. When the work using the RCBC chipping robot is performed at constant speed irrespective of the striking object and its state, hardness, the concrete is removed unevenly according to hardness and this causes an uneven chipping surface, i.e. fall in chipping quality. Therefore, in order to improve the chipping quality, motion control for adjusting the chipping speed according to the striking target and its state is necessary. In this paper, a force-regulated impact control algorithm to classify a striking object of the robot and its state from reaction force and control motion of the robot according to the state is proposed. In order to implement the proposed algorithm, reaction forces when the robot strikes concrete with chipping tool are collected, and classification to identify the striking object and its hardness is carried out based on the obtained reaction forces. In addition, a variable motion control algorithm is realized by setting the dynamic characteristics of the robot with respect to the reaction force according to striking object and its stat. To verify the effectiveness of the proposed algorithm, chipping work with an RCBC chipping robot is conducted in a simulation environment consisting of reinforced concrete. Chipping work with the robot is carried out in both cases, with and without the proposed algorithm, and the performance of the proposed algorithm is verified by comparing and analyzing the quality of each chipping work.