Engineering topics

Desai, Rajiv S.

Publications and source records attributed to Desai, Rajiv S..

6 records

NASA NTRS1993

Experiments with a small behaviour controlled planetary rover

A series of experiments that were performed on the Rocky 3 robot is described. Rocky 3 is a small autonomous rover capable of navigating through rough outdoor terrain to a predesignated area, searching that area for soft soil, acquiring a soil sample, and depositing the sample in a container at its home base. The robot is programmed according to a reactive behavior control paradigm using the ALFA programming language. This style of programming produces robust autonomous performance while requiring significantly less computational resources than more traditional mobile robot control systems. The code for Rocky 3 runs on an eight bit processor and uses about ten k of memory.

Miller, David P.↗

NASA NTRS1992

Planning Assembly Of Large Truss Structures In Outer Space

Report dicusses developmental algorithm used in systematic planning of sequences of operations in which large truss structures assembled in outer space. Assembly sequence represented by directed graph called "assembly graph", in which each arc represents joining of two parts or subassemblies. Algorithm generates assembly graph, working backward from state of complete assembly to initial state, in which all parts disassembled. Working backward more efficient than working forward because it avoids intermediate dead ends.

De Mello, Luiz S. Homem↗

NASA NTRS1992

Microrover Operates With Minimal Computation

Small, light, highly mobile robotic vehicles called "microrovers" use sensors and artificial intelligence to perform complicated tasks autonomously. Vehicle navigates, avoids obstacles, and picks up objects using reactive control scheme selected from among few preprogrammed behaviors to respond to environment while executing assigned task. Under development for exploration and mining of other planets. Also useful in firefighting, cleaning up chemical spills, and delivering materials in factories. Reactive control scheme and principle of behavior-description language useful in reducing computational loads in prosthetic limbs and automotive collision-avoidance systems.

Miller, David P.↗

NASA NTRS1990

Studies in knowledge-based diagnosis of failures in robotic assembly

The telerobot diagnostic system (TDS) is a knowledge-based system that is being developed for identification and diagnosis of failures in the space robotic domain. The system is able to isolate the symptoms of the failure, generate failure hypotheses based on these symptoms, and test their validity at various levels by interpreting or simulating the effects of the hypotheses on results of plan execution. The implementation of the TDS is outlined. The classification of failures and the types of system models used by the TDS are discussed. A detailed example of the TDS approach to failure diagnosis is provided.

Lam, Raymond K.↗

NASA NTRS1990

Assembly, disassembly and repair of large truss structures in space

This paper addresses the problem of planning assembly, disassembly and repair sequences for large truss structures in space. First, the AND/OR graph representation scheme for mechanical assemblies is reviewed and extended to truss structures. The assembly, disassembly and repair sequence planning problem is then formulated as a graph search problem using assembly's AND/OR graph and appropriate cost functions. The general search problem, which is known to be exponential, is simplified by taking advantage of the symmetries that exist in truss structures. General cost functions for truss assembly are discussed.

Desai, Rajiv S.↗

NASA NTRS1989

Identification and verification of termination conditions in fine motion in presence of sensor errors and geometric uncertainties

Results are reported from a search for reasonable constraints under which an automatic uncertainty-handling strategy (for robot part-mating tasks) is guaranteed to succeed. The concept of contact formations is introduced to describe contacts among parts in a system, aiming at reducing the dimensionality of assembly verification. Also described is a technique for identifying contact formations in spite of errors in sensing and geometric uncertainties. It is impossible to verify termination conditions in general. Design constraints for which verification can be guaranteed are formulated and shown to be reasonable in the sense that they do not impose unrealistic conditions on typical designs. Results of implementation on a robot system consisting of a PUMA robot with RTI force/torque sensors support the theoretical derivations and show empirically that good results can still be obtained when the theoretical constraints are relaxed somewhat.

Desai, Rajiv S.↗