Human-robot cooperation control for installing heavy construction materials

Seung Yeol Lee, Kye Young Lee, Sang Heon Lee

Autonomous Robots, N0.22, 2007

Summary

                  Automation System and Robotic Construction is an issue which has came to discussion among researched due to the importance of safety, productivity, quality and work environment. The first robot applied in construction field was in 1983, followed by other examples of robots using pneumatic actuators and servo motors in hybrid solutions or in master-slave solutions. With the new trend of tall and dangerous buildings, advances in new material have be done, but still the process remains mainly assigned to manpower. An automation system (ASCI: Automation System for Curtain Wall Installation) has been developed for mechanized construction to enable simple and precise installations, specially in regard of safety improvement. Automation in construction faces some characteristics which make it much different from manufacturing, in fact rarely processes are highly repetitive, therefore the requirements for this system are: the robot must follow the operator in various works, a robot must share the work space with the operator, there must be coordination between the operator’s and the robot’s force and an intuitive operation method that reflect dexterity of an operator should be performed. Human robot cooperation has been an interest for many different fields of application, in the 60’s the department of defence enhanced the capability of carrying heavy material with “Suit of Armor” and similar ideas where carried later on.  The paper introduces a robot control method for the installation of heavy construction material in cooperation with a human operator, basically the system allows the operator to handle heavy material by exerting operational force with a certain power assist ratio. Target dynamics model the interactions among human, robot and environment, an impendance controller which considers each environment contacting is performed considering two cases: constrained and unconstrained, which differ in the presence or not of environment contact. In unconstrained condition the operator handle heavy materials on an obstacle free area, the force is measured by a force (torque) sensor, F_h(T) is the force generated by the interaction between the operator and a heavy material, M_pt(M_ot) and B_pt(B_ot) are respectively the n x n positive definite diagonal inertia and damping matrices. The desired dynamics, given input F_f,(T_h) is obtained by impedance, by means of λ_p and λ_o, respectively the power assist ration of the position and orientation. The Stiffness Matrices is K is to not be considered having the property of a spring.  Constrained condition differed in the presence in the impedance of F_e(T_e), the experimental force (torque) and in this case, if contact occurs the generalized active impedance is considered. High stability is achieved s through damping, where too much damping may decrease mobility of the system so M_pt(M_ot) and B_pt(B_ot) are adjusted according to the requirements of the operator and appropriate values are found through simulation. Motion control is made stiffness so as enhance disturbance disturbance rejection, so a reference frame and a desired frame are introduced in the previous models. Experiment have been carried on requiring the operator to perform a circle applying force on the robot’s gripper.

Key Concepts

Human Robot Interaction, Human Robot Cooperation, Impedance Control, Control Systems

Key Results

The results show that and increase in M_pt(M_ot) stability decreases (although the with the increase of M_pt an object can move to a long-distance place with small operational force), while the opposite is for B_pt(B_ot), making it necessary to make a trade-off.

Also it is shown that a robot operation without the inner motion control (which balances the system) shows inferior desired position following performance in an unconstrained condition.

The force required by an operator gets smaller with higher values of the power ratio, but this won’t cause hang in F_e (force that reflect in the contacting condition.