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A problem still unsolved in kinematics is the enumeration of a complete list of kinematic chains and mechanisms without isomorphisms and without degenerate chains that operate in any screw system. In this paper, a method for the enumeration of kinematic chains without isomorphisms and degenerate chains for all screw systems and a new method of enumeration of kinematic chain inversions (i.e. mechanisms) based on group theory techniques are presented. New concepts of the group theory are introduced and a new method of enumeration of inversions is presented. Kinematic inversions are related to the symmetries of the chain which can be identified analysing the corresponding graph. The symmetry of a graph can be identified for the group of automorphisms of the graph and its orbits provides sets of vertices (links) that are in the same equivalence classes, i.e. they have the same properties of symmetry. The main definitions of group theory and examples of application of the new method of enumeration of inversions are presented. New results are obtained and divided in two classes: original results in non-planar screw systems (λ = 3) and results in agreement with a previously published list for planar kinematic chains and planar mechanisms (inversions). Two tables (1 and 3) are provided, which are up-to-date lists of kinematic chains and mechanisms for several screw systems.

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The growing interest in use of renewable energy sources, such as photovoltaic energy systems, occurs due to the high cost of conventional energy sources and the environmental awareness linked to renewable sources. For photovoltaic panels efficient operation, it is necessary the system presents appropriate cleaning conditions to the dirt do not obstruct the solar radiation incidence. In this context, periodic cleaning of photovoltaic panels is an obvious necessity. This work aims to present a market survey and patent analysis on the use of robots to perform cleaning tasks on photovoltaic panels. For that, the Brazilian and international literature were consulted. As a result, it was noted the existence of different solutions for cleaning photovoltaic panels, all with positive and negative aspects in practical terms. With this study it was also possible to map the technology of robotics for cleaning photovoltaic panels.

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