This paper presents a novel approach for an energy control of a DC microgrid. It combines decentralized grid management and energy management. For this purpose, the conventional voltage droop curves are extended to a characteristic diagram with electricity costs as a further dimension. The support points of these characteristic diagrams are then optimized with a particle swarm optimizer. The target criterion of this optimization is a monetary cost function, that takes several effects, such as depth of discharge, on the operating costs into account. The optimized characteristic diagrams are designed more robust by a sensitivity analysis. The proposed method has been tested successfully in simulations and experiment and was always more cost-efficient than the initial characteristics diagram. Index Terms-energy control, DC microgrid, characteristic diagrams, voltage droop control This is the author's version of an article that has been published in the ICIT 2019 proceedings.

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The use of continuous and flexible structures instead of rigid links and discrete joints is a growing field of robotics research. Recent work focuses on the inclusion of continuous segments in parallel robots to benefit from their structural advantages, such as a high dexterity and compliance. While some applications and designs of these novel parallel continuum robots have been presented, the field remains largely unexplored. Furthermore, an exact quantification of the kinematic advantages and disadvantages when using continuous structures in parallel robots is yet to be performed. In this paper, planar parallel robot designs using tendon actuated continuum robots instead of rigid links and discrete joints are proposed. Using the well known 3-RRR manipulator as a reference design, two parallel continuum robots are derived. Inverse and differential kinematics of these designs are modeled using constant curvature assumptions, which can be adapted for other actuation mechanisms than tendons. Their kinematic performances are compared to the conventional parallel robot counterpart. On the basis of this comparison, the advantages and disadvantages of using continuous structures in parallel robots are quantified and analyzed. Results show that parallel continuum robot can be kinematic equivalent and exhibit similar kinematic performances in comparison to conventional parallel robots depending on the chosen design.

Industrial manipulators and parallel robots are often used for tasks, such as drilling or milling, that require three translational, but only two rotational degrees of freedom (“3T2R”). While kinematic models for specific mechanisms for these tasks exist, a general kinematic model for parallel robots is still missing. This paper presents the definition of the rotational component of kinematic constraints equations for parallel robots based on two reciprocal sets of Euler angles for the end-effector orientation and the orientation residual. The method allows completely removing the redundant coordinate in 3T2R tasks and to solve the inverse kinematics for general serial and parallel robots with the gradient descent algorithm. The functional redundancy of robots with full mobility is exploited using nullspace projection.

Robotic tasks like welding or drilling with three translational and only two rotational degrees of freedom ("3T2R") are of high industrial relevance but are rather scarcely addressed in scientific publications. Existing solutions for the resolution of the functional redundancy of robotic manipulators with more than five axes performing these tasks either expand the full kinematic formulation or reduce it in intermediate steps. This paper presents an approach to reduce the kinematic formulation from the start to solve the problem in a simpler way. This is done by using a set of reciprocal Euler angles to describe the end-effector orientation and the orientation error in inverse kinematics.

A new approach for more energy efficient industrial production processes are smart industrial direct current (DC) microgrids with one or more connections to the alternative current (AC) grid. The advantage of the DC-technology is an easier integration of renewable energies sources and energy storage systems (ESS). Different applications for ESS are possible, for instance an uninterruptible power supply (UPS) for a DC microgrid. Within this paper, a new handling concept for a mains supply failure (e.g. a blackout of the supplying AC grid) with a droop curve control is introduced. In this approach, the droop curve controlling the ESS is adapted, depending on the ESS' state of charge (SoC), which results in a droop curve with a hysteresis. This concept realizes the charging of the ESS only with recuperation energy, that occurs in the DC microgrid during the production process. Thus, all recuperation energy will be kept in the DC microgrid and a transformation of the energy in AC or an energy loss through braking resistors will be avoided. Furthermore, no additional energy is needed to charge the ESS. This increases the energy efficiency of the entire production process. The concept was verified in simulation and validated in experiment and it has shown a DC voltage deviation of less than two percent.

This paper presents an approach to significantly improve modeling accuracy for the power and energy demands of industrial robots. This is achieved by taking the temperature dependency of the joint's viscuous friction parameters into account. While the connection is commonly known, it is usually neglected in state-of-the-art energy consumption models for industrial robots. This paper shows that a consideration of temperature-dependent friction provides significant improvement of energy modeling accuracy. The approach is validated on a test rig with a KUKA KR 16 robotic manipulator. Measurements show that the grid energy consumption modeling error can be reduced from up to 45 % to approx. 5 % over the whole spectrum of operating temperatures.

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