The figure depicts the Legged Excursion Mechanical Utility Robot (LEMUR) - a six-legged robot for demonstrating robotic capabilities for assembly, maintenance, and inspection. LEMUR is designed to be capable of walking autonomously along a truss structure and to perform other operations.
LEMUR is equipped with stereoscopic video cameras and image-data-processing circuitry for navigation and mechanical operations. It is also equipped with a wireless modem for remote operations. Upon receipt of a command via the modem, LEMUR would walk along the truss structure toward a mechanical assembly at a prescribed location. Once LEMUR was within a distance of 1 m from the assembly, its artificial-vision system should be able to recognize the image of the assembly and enable the LEMUR to move autonomously toward the assembly. Upon arrival at the assembly, LEMUR would perform simple mechanical operations with one or both of its front legs. It could also transmit images to a host computer.
Each of the six legs of the LEMUR is operated independently. Each of the four rear legs has three degrees of freedom (DOFs), while each of the front two legs has four DOFs. The front two legs are designed to hold, operate, and/or be integrated with tools. For example, the right front leg could be made capable of holding and turning a wrench socket, while the left front leg could be equipped with a hand, which could include an in-line macroscopic camera. The kinematic design of the LEMUR is such that it could support itself on the four rear legs, or, preferably, on three of them. The feet on the rear legs are capable of grappling.
LEMUR includes an onboard computer containing a Pentium (or equivalent or better) processor with a minimum speed of 200 MHz, a dynamic random-access memory of at least 32MB, and an assortment of digital control circuits, digital input/output circuits, analog-to-digital converters for input, and digital-to-analog (D/A) converters for output. Feedbacks from optical encoders in the leg actuators are utilized for closed-loop microcomputer control of the positions and velocities of the actuators. Signals for controlling motors in the actuators are generated by D/A converters and multiplexed through a sample-and-hold circuit. The multiplexed outputs are sent to pulse-width-modulator circuits, the outputs of which would constitute the control voltages applied to the motors.
LEMUR contains a rechargeable-battery power supply that could sustain operation for 1 hour. It would also be capable of operation through an electrical umbilical cord. Optionally, the umbilical cord could serve as a bypass for the wireless modem.
This work was done by Gregory Hickey and Brett Kennedy of Caltech for NASA's Jet Propulsion Laboratory.