This paper proposes a methodology for optimizing a class of robotic solar tracking systems with two degrees of freedom using a heuristic approach. The proposal allows a balance to be found between the energy consumption and tracking accuracy in the tracking system. The main purpose is the behavior modification of the system through the combination of two manipulation strategies, one associated with the energy savings and the other with the tracking error. The heuristic approach was implemented in a solar tracking system with the end effector connected to a solar measurement device. Four energy saving strategies and three tracking strategies were developed, simulated and implemented in the system. The simulation results show that the resulting strategy combination (tracking error and energy saving approach) led to 31.55% energy saved compared to the reference values, with a tracking error of 0.06∘. Moreover, the experimental assessment of the same combination led to 26.98% energy being saved, with an azimuthal tracking error of 0.062∘ and elevation tracking error of 0.071∘. The preceding values support the aim of the presented proposal to significantly reduce the energy consumption while concurrently achieving a competitive tracking error.

This paper is concerned with the design and experimental assessment of, both, feedback linearization and sliding mode control techniques to the tracking trajectory problem of a flexible-joint robotic arm for a smooth rest to rest maneuver. The robust improvement of these controllers is analyzed by means of additional integral compensation, in which an alternative sliding surface was proposed for the control of the flexible arm. A feedback linearization of the nonlinear dynamic equation of the robot arm is computed in order to get a full-state non-linear feedback control law. On the other hand, it is proposed a second order sliding mode control with an integral term in the sliding surface, which improves the robustness of the controller sliding surface. Some experimental evaluations that include the addition of external unmodeled perturbations to test the enhancement of the robustness property show the improvements and effectiveness of the proposed control laws in disturbance rejection tasks. The controllers were implemented using exclusively position measurements and time derivatives approximations.

Solar Tracking Systems are useful to increase the generation efficiency of photovoltaic technology, mainly for concentration technology, where dual-axis is required on account of the high accurate alignment to the Sun. Even when there exists a strong relation between tracking error and energy efficiency, multiple technological and research developments have sought to solve these problems independently. The present research proposes a novel concurrent design methodology for optimizing the overall performance of two-axis trackers, allowing to keep a balance between the tracking error and the energy consumption from the design stage, from an optimization approach. The concurrent approach was implemented to design a Solar Tracker as a solar monitoring system, was compared with four commercial systems, obtaining a similar pointing accuracy with a mixed tracking error of ${0.0942}^{°}$. The system has the best energy balance, consuming only $0.9641\%$ of the energy generated for the tracking action, below commercial models. Finally, a CO${}_2$ impact analysis was carried out, where the proposed tracker obtained the lowest value, with $25.7018$ g. The results support the developed concurrent strategy for the optimization of the overall performance of dual-axis systems, allowing us to find a harmonic balance between the energy consumption and the required tracking accuracy.

This study presents the design and evaluation of a prototype snake-like robot that possesses an actuation system based on shape memory alloys (SMAs). The device is constructed based on a modular structure of links connected by two degrees of freedom links utilizing Cardan joints, where each degree of freedom is actuated by an agonist–antagonist mechanism using the SMA spring-shaped actuators to generate motion, which can be easily replaced once they reach a degradation point. The methodology for programming the spring shape into the SMA material is described in this work, as well as the instrumentation required for the monitoring and control of the actuators. A simplified design is presented to describe the way in which the motion is performed and the technical difficulties faced in manufacturing. Based on this information, the way in which the design is adapted to generate a feasible robotic system is described, and a mathematical model for the robot is developed to implement an independent joint controller. The feasibility of the implementation of the SMA actuators regarding the motion of the links is verified for the case of a joint, and the change in the shape of the snake robot is verified through the implementation of a set of tracking references based on a central pattern generator. The generated tracking results confirm the feasibility of the proposed mechanism in terms of performing snake gaits, as well as highlighting some of the drawbacks that should be considered in further studies.