The goal of this research is to enable a multi-limbed robot to climb vertical rock using techniques similar to those developed by human climbers (Figure 1). The robot consists of a small number of articulated limbs. Only the limb end-points can make contact with the environment—a vertical surface with small, arbitrarily distributed features called holds (Figure 2). A path through this environment is a sequence of one-step climbing moves in which the robot brings a limb end-point to a new hold.
The robot maintains balance during each move by pushing and/or pulling at other holds, exploiting contact and friction at these holds while adjusting internal degrees of freedom to avoid sliding. The fixed set of robot-hold contacts during a one-step move is called a stance. Our planner combines a multi-step and a one-step planner. The multi-step planner searches a graph representing the adjacency relation between stances to compute a sequence of steps from the initial to the goal stance. The one-step planner (a PRM planner) searches the robot’s configuration space at a given stance for a feasible path between the previous and the next stance in the sequence computed by the multi-step planner. The one-step planner makes use of an efficient test efficient of the quasi-static equilibrium of thee robot. The multi-step planner makes use of lazy search techniques to speed up the exploration of the stance graph. It also makes use of a trained classifier to quickly recognize infeasible transitions between stances. The planner was tested in simulation and on a real four-limbed robot—LEMUR IIB—created by NASA/JPL (Figure 2). A new climbing robot with an increased number of degrees of freedom is currently being developed (Figure 3). In another develop, we adapt and extend the planner to the ATHLETE robot, a six-legged vehicle designed by NASA/JPL to climb steep, irregular, and possibly non-rigid lunar terrain (Figure 4). In such terrain ATHLETE’s wheels are frozen and are used as “feet”. This project is a joint effort with the group of Prof. Steve Rock in the Stanford Aerospace Robotics Lab.
Source: Standford