Comparative study of the usability of directional commands for two different conceptions of agricultural machinery

Santa Catarina showed a significant increase in its fleet of agricultural machinery in the past 40 years. For the historical origins, the state experienced a strong farm household that grows in small portions of land. This small size of farms boosted the purchase of farm machinery such as small power tillers. It is estimated that in Santa Catarina there are more than 20,000 machines like these. The initial design of this machine its use is intended for operations on foot position for possessing it commands designed for the walking posture. But a large proportion of power tillers is used to transport cargo and personnel, by adapting implement that allows driving in the sitting position. This modification is incomplete because it does not allow the installation of steering wheel. Thus the inadequacy of command increases the difficulty in driving the vehicle and may potentiate human error, leading to the accident. To compare the usability and rate of errors in triggering commands power tiller and tractors, the work used two methods: analysis uses the model Usa-Design (U-D©) and usability testing. A panel was positioned in front of the two agricultural machines simulated obstacles appearing on the right or left side of operator, in a position to rise or fall, and observed the reaction to the same stimulus. A sample of 53 volunteers showed that for all groups (experience levels ) the error was greater for the power tiller. The tractor had 5.7 % error while the power tiller this value was 49.1 %. The results found by U-D© model was similar with the found in the test and pointed out serious deficiencies in functional and safety aspects of power tiller