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Two of the main sources of position error in parallel manipulators are clearances at joints and elastic deformations of the links. The former are usually necessary in order to produce a smooth movement between the pin and the hub of a joint. The latter are unavoidable and they tend to be greater in manipulators designed for pick-and-place tasks due to the need of light links. It can be stated that the end-effector pose error depends on the mechanism configuration, the applied external wrenches, the nature and magnitude of clearances, and the rigidity of the mechanical components. This paper proposes a procedure to calculate position error in parallel manipulators due to both clearances and elastic deformations. Although the procedure is applicable to any planar or spatial parallel manipulator, a planar 5R mechanism is used as an illustrative example in order to make it easier to understand.

Solar trackers are devices that improve the efficiency of photovoltaic collectors increasing the area exposed to direct radiation of the sun. The main drawback of these kinds of devices is that they have to consume certain energy in order to move the collectors following the sun trajectory. This work presents the detailed design of a mechanism with parallel kinematics architecture able to accurately follow the sun motion, which has been designed with the aim of minimizing the energy consumption during its operation.

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