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When considering energy requirements and optimization for robots, it is important to consider mission requirements,
and the type of robot performing the mission. For example, the small robots used in today's reconnaissance
and explosive ordnance disposal applications have weak manipulators, and do not perform significant physical
work on their surrounding environment. In this paper, we focus on robots that will be required to do much
more physically demanding tasks, such as manipulating large heavy objects in unstructured environments, and
carrying such objects over challenging terrain. Energy considerations for such systems must include models of
physical work performed for basic manipulation, pose transition, and locomotion maneuvers.
Given the scarcity of robots that can perform useful work in unstructured environments, it is useful to
begin the investigation of energy optimization for such robots by considering typical tasks they might perform.
This paper makes three contributions in this direction. First, we develop a set of standard tasks that would
be useful in unstructured environments. The tasks are expressed in terms of the objects being manipulated,
and the work being done, so they are independent of robot morphology. Second, we develop energy metrics
and analytical results for theoretical energy requirements for these tasks. These requirements assume no losses
due to friction, so they give a best-case estimate of what is achievable. Such metrics are useful in subsequent
evaluation of real systems that are not as efficient. Third, we perform preliminary comparisons between different
actuation technologies in performing these tasks. These actuation technologies will include electro-mechanical
and hydraulic systems. We compare these technologies in terms of power density, and evaluate expected energy
efficiency when performing the metric tasks.
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