The variable terrain tilt platform (VTTP) is a means of providing simulated terrain for mobility testing of engineering models of the Mars Exploration Rovers. The VTTP could also be used for testing the ability of other robotic land vehicles (and small vehicles in general) to move across terrain under diverse conditions of slope and surface texture, and in the presence of obstacles of various sizes and shapes.

The VTTP consists mostly of a 16-ft- (4.88-m)-square tilt table. The tilt can be adjusted to any angle between 0° (horizontal) and 25°. The test surface of the table can be left bare; can be covered with hard, high-friction material; or can be covered with sand, gravel, and/or other ground-simulating material or combination of materials to a thickness of as much as 6 in. (≈15 cm). Models of rocks, trenches, and other obstacles can be placed on the simulated terrain.

ImageFor example, for one of the Mars- Rover tests, a high-friction mat was attached to the platform, then a 6-in.- (≈15 cm) deep layer of dry, loose beach sand was deposited on the mat. The choice of these two driving surface materials was meant to bound the range of variability of terrain that the rover was expected to encounter on the Martian surface. At each of the different angles at which tests were performed, for some of the tests, rock-like concrete obstacles ranging in height from 10 to 25 cm were placed in the path of the rover (see figure).

The development of the VTTP was accompanied by development of a methodology of testing to characterize the performance and modes of failure of a vehicle under test. In addition to variations in slope, ground material, and obstacles, testing typically includes driving up-slope, down-slope, cross-slope, and at intermediate angles relative to slope. Testing includes recording of drive-motor currents, wheel speeds, articulation of suspension mechanisms, and the actual path of the vehicle over the simulated terrain. The collected data can be used to compute curves that summarize torque, speed, power demand, and slip characteristics of wheels during the traverse.

This work was done by Randel Lindemann of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free online at under the Mechanics category. NPO-42522

This Brief includes a Technical Support Package (TSP).
Platform for Testing Robotic Vehicles on Simulated Terrain

(reference NPO-42522) is currently available for download from the TSP library.

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This article first appeared in the June, 2006 issue of NASA Tech Briefs Magazine.

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