Cooperative hoisting with two crawler cranes under rope-velocity constraints

Hoisting of large span and large tonnage equipment often requires two or more cranes. Usually cooperative hoisting is carried out by multiple drivers under the command of one coordinator for the task. This leads to low lifting efficiency and low safety and it is desirable to automate this process. In this paper, the physical model of double cranes is analyzed to obtain the constraints imposed by cooperative hoisting. We first solve the direct and inverse kinematic problem, obtaining the kinematic relationship between load coordinates and cable lengths. Then we consider a hoisting operation defined by an assigned trajectory and by a particular trapezoidal velocity profile, parameterized by a constant cruising velocity. We show how to compute the optimal value of the parameter that minimize the hoisting time while ensuring the admissibility constraints are satisfied. Several simulations related to two industrial crawler cranes are presented.