Simulating the Human-Machine Interface for Excavation Illustrates Benefits of ERC's University/Industry Collaboration
Researchers affiliated with the Center for Compact and Efficient Fluid Power (CCEFP), an NSF-funded Engineering Research Center (ERC) headquartered at the University of Minnesota, are making significant progress in their approaches to enhancing, by means of simulation, the work performance of mobile-equipment operators.
Researchers at Georgia Tech and North Carolina Agricultural and Technical State University, in cooperation with their CCEFP colleagues at Purdue University (all CCEFP core partner institutions) as well as with input and contributions from several of the Center’s industrial partners, are working in a multi-disciplinary team to perfect an excavator simulator. Beyond illustrating a key value of an ERC's collaborative approach to research, the implications for increased efficiency and improved performance resulting from this effort are significant. Demonstrated improvements in excavator productivity, fuel efficiency, accuracy of motion, and error frequency are indicators of enhanced performance. To date, performance improvements using these measures have been particularly dramatic for novice operators, who can perform at the current levels of experts after spending time in the simulator. (See accompanying figure.)
The excavator simulator, developed at Georgia Tech, combines the cab of a Bobcat 435 mini-excavator (the same model as the Center’s excavator test bed at Purdue) with a full dynamic model of the excavator’s hydraulic and mechanical systems and their interactions with the environment. A 52” LCD television screen, mounted vertically on the cab’s windshield, displays the simulated excavator arm and environment.
Fidelity of the graphics program exceeds that of most academic simulators. In addition to donating an excavator to the project, Bobcat gave the CCEFP access to the CAD files of the machine, which allowed the researchers to create a high-fidelity graphical model of the arm. The environment shown includes trees, bushes, and the shadow of the excavator’s arm to increase the operator’s depth perception. The graphics program also plays a continuous engine noise track that varies in volume with the power demand of the pumps. The excavator’s dynamics are calculated at 1 kHz in real time. A new soil model was developed for the simulator that calculates environmental forces for any bucket trajectory through the soil. Researchers at Purdue made friction, line loss, and other measurements, which were included in the model and improved its fidelity.