Design of a haptic controller for excavators

Van der Zee, Lodewyk Francois (2009-03)

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.

Thesis

The input orientation of the excavators in use today usually comprises two joysticks that control the actuator links individually. In order to perform an excavation task, several different combinations of joystick inputs are required, placing high psychomotor demands on the operator. In training an operator this creates a steep learning curve, with a lengthy training time and a reasonable amount of experience being required to perform an excavation task skilfully. In this master’s thesis a haptic1 device was developed, resolving input ergonomics and creating a single input device capable of providing feedback to the operator. The design and construction of the haptic device, with the related control scheme, is presented and discussed. The control scheme combines position and rate control, and relates all the actuator joint positions to a single end-effector point. The control and ergonomic aspects of the haptic device were tested and compared to the traditional two joystick control setup by means of the implementation of a virtual excavator simulator. The simulation was developed in MATLAB, and virtual excavator displayed in an openGL window. The objective of this study was to evaluate the human factors related to the input orientation. Ten inexperienced test subjects were recruited to perform four sets of tests, where each test required a different level of operator skill. The results indicated that, on average, the test subjects had an increased level of performance after training on the haptic device. These results strongly support the hypothesis that haptic control simplifies the operational tasks required for operating an excavator. 1The word haptic means of, or relating to, the sense of touch, or tactile

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