How should Trackball Directional Movement Intuitively Relate to an End Effector?

Abstract

Three strategies for the trackball control of an end effector on a laparoscopic graspers tool were tested to see which strategy was most intuitive to the user. The three strategies (UURR, UDRL, UDRR) were tested on four different orientations of the hand: horizontal holding the tool as an extension of the arm while rolling the trackball with the thumb, horizontal holding the tool as an extension of the arm and forearm pronated 90 degrees while rolling with the thumb, horizontal with tool 90° to arm using the thumb, and horizontal with tool 90° to arm using the index finger to roll the ball. Twenty-four subjects, each randomly chosen to test one of the three movement strategies, performed two trials sets per hand orientation, the first to test for intuition and the second to test for the effect of training. The outcome of the trials was a number of correct and incorrect movements of the trackball to control the end effector which was simulated on a computer screen. The results were analyzed using a general linear model test on repeated measures to determine the effects of strategy and hand orientation. Analyses showed that intuitively, subjects were significantly better when the end effector moved as the trackball did (UURR). The analyses of the learned trials showed that subjects did equally well with all three strategies. From these results, it was determined that the trackball control of the forceps will be manipulated using the UURR strategy.