Daedalus: A Walking Robot

Carnegie Mellon University's Autonomous Planetary Exploration Program (APEX) is currently building the Daedalus robot. Daedalus is a robotic system capable of performing extended autonomous planetary exploration missions. Extended autonomy is an important capability in robots because the continued exploration of the Moon, Mars, and other solid bodies within the solar system will probably be carried out by autonomous robotic systems. There are a number of reasons for thisÑthe most important are: the high cost of placing a man or women in space; the high risk associated with human exploration; and the communication delays that make teleoperation infeasible.

The Daedalus robot represents an evolutionary approach to robot mechanism design and software system architecture. It exhibits the best capabilities of a walking robot without the complexity in design and locomotion found in other robots. Using previously proven technologies, the APEX project endeavors to encompass all of the capabilities necessary for robust planetary exploration.

Daedalus belongs to a class of walking robots called frame walkers. Frame walkers are considered to be the simplest walking machines capable of negotiating rugged terrain. Daedalus has a polygonal-shaped body and two frames, each of which has three legs as illustrated in figure 1. This configuration makes it inherently statically stable. It has a relatively small design mass of 200kg, stands between 1.5-2.5m tall, and is designed for a walking speed of 10m/minute. Its polygonal body enables maximum utilization of payload volume. The use of orthogonal legs allows the decomposition of horizontal and vertical motions, thus increasing power efficiency. Leg masses are reduces by combining strength and bearing members into a single component.

The robot moves in the following manner: the legs on one frame are lifted, this frame is moved relative to the other, then its legs are set down. Then the legs on the other frame are lifted, the second frame moves with respect to the first, then its legs are set down. This cycle of six motions describes a complete walking cycle. This technique enables the robot to negotiate slopes up to 30¡ and ditches by varying the step sizes appropriately while keeping the body level. Foot placement is reactive in nature. The compliant foot uses foot sensors to detect the ground. It then decelerates accordingly to come to a stop gracefully. This also enables Daedalus to tackle any unexpected obstacles.

The Daedalus configuration requires prismatic joints for its vertical and horizontal motions. A gear rack, for power transmission, is bolted directly to the leg, and the leg assembly is driven by a gear motor with an output pinion on a stationary member.

For efficient locomotion, the walking cycle, which involves phase times and acceleration times, was determined to minimize maximum power. The drivetrain, which is both highly efficient and robust, was designed using an innovative power balancing method. Because of the wide range of required force/speed, a two-speed gearbox was designed so that its motors could be efficient in all motion phases. This resulted in a greater than 65% of electrical power input to mechanical out-put.

Future work will involve integrating perception, a planning scheme which will be a hybrid combining the strengths of hierarchical and reactive planning schemes, and real-time control to fulfill the goals of terrain ability and reliability.

Point of Contact:
Kevin Dowling
Robotics Institute
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-8830

Telerobotics Program page

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Maintained by: Dave Lavery
Last updated: May 10, 1996