A Measure of Stability for Mobile Manipulators With Application to Heavy-Duty Hydraulic Machines

This paper describes the development of a suitable algorithm to compute the potential of tipping-over for vehicles that carry manipulators. The energy method developed by Messuri and Klein (1985) is extended here to quantitatively reflect the effect of forces and moments arising from the manipulation of the implement. The amount of the impact energy that can be sustained by the vehicle without tipping-over, about each edge of potential overturning is computed. First, the instantaneous onset of instability configuration of the machine about the edge is determined by constructing an equilibrium plane. Next, the work done by all acting forces and moments when the machine is virtually brought to this unstable stance from the current state, is calculated. This work is the indication of the proximity of the machine to tipping-over around that edge. The application of this study is directed at industrial mobile machines that carry human-operated hydraulic manipulators. The algorithm is therefore used to study the stability of an excavator based log-loader. Simulation studies clearly show the importance of inertial loads in determining the stability of such machines.