Tip-Over Detection and Avoidance Algorithms as Stabilization Strategy for Small-Footprint and Lightweight Mobile Manipulators

Abstract

The risk of tip-over is a common problem in agile, lightweight mobile manipulators. An easy-to-implement and reliable stabilization strategy plays a key role for the wide operation of these highly dynamic systems in the industrial sector. This study addresses a method in which mobile manipulators independently detect instabilities and trigger countermeasures to prevent them from tilting. A tip-over detection algorithm was implemented based on the Moment Height Stability method, whose main advantage is the examination of all dynamical influences affecting the mobile manipulator to indicate how stable/unstable the system is during its operation. Consequently, the theoretical workspace of the robot manipulator was redefined using a certain critical boundary surface subjected to the analysis of the stability value. This workspace optimization was complemented with an additional algorithm in which the robot manipulator joints adopt an appropriate configuration to compensate in real-time detected instabilities. During repositioning of the robot manipulator’s arm, the initial orientation of its tool center point is maintained to avoid a workpiece mishandle. The simulation and experimental results suggest that the system is stable and safe to operate in changing environments, thus providing a universal approach to avoid the inherent stability problems of agile and lightweight mobile manipulators.