The coexistence of humans and robots in fenceless robot cells requires robust safety precautions to prevent humans from being injured. Currently, safety is ensured by limiting the robot velocity, force, and power. This results in large cycle times and, hence, very inefficient industrial applications, where no amortization of the robotic system can be expected. In this letter, a novel method for improving the robot performance is presented that still complies with the international safety standards for collaborative robots. The approach of this letter is based on a projection of a human arm motion into the robot's path to estimate a possible collision with the robot. This idea is addressed in an optimization approach by minimizing the time needed by the robot to reach the goal position under human-in-the-loop constraints. The segmented path is optimized by solving a nonlinear programming problem, and the effect of crucial parameters is analyzed. To guarantee a flexible motion of the resulting optimized path, a generalization method using dynamic movement primitives and the compliance of constraints are proposed. Experiments validate this new method that significantly improves the efficiency of human-robot coexistence.

The control design for many practical applications involves a need to specifically treat parameter uncertainty and disturbances. As shown in previous work of the authors, techniques from interval analysis can be used for this purpose in an efficient way. The two options that have been considered so far are the use of interval analysis in either a framework for model predictive control or in a framework for variable-structure sliding mode design. In the latter case, interval techniques can be used efficiently for a robust stabilization of continuous-time dynamic systems despite bounded uncertainty. To avoid unnecessarily conservative control strategies, it has to be shown in real time that the closed-loop control system is guaranteed to remain asymptotically stable despite bounded error variables. This online stability proof is performed on the basis of suitable candidates for Lyapunov functions, whereas functionalities for interval analysis are provided by C++ software libraries. Required partial derivatives, for transformations of state equations into suitable canonical forms and for the estimation of a finite number of time derivatives of the controlled variables, are efficiently computed by algorithmic differentiation. This paper presents an overview of interval-based variable-structure control approaches for the thermal behavior of solid oxide fuel cells. These approaches consist of trajectory tracking during nonstationary heating phases and disturbance compensation at high-temperature operating points. Finally, they rigorously account for state and actuator constraints.

In this paper, control-oriented modeling approaches are presented for distributed parameter systems. These systems, which are in the focus of this contribution, are assumed to be described by suitable partial differential equations. They arise naturally during the modeling of dynamic heat transfer processes. The presented approaches aim at developing finite-dimensional system descriptions for the design of various open-loop, closed-loop, and optimal control strategies as well as state, disturbance, and parameter estimation techniques. Here, the modeling is based on the method of integrodifferential relations, which can be employed to determine accurate, finite-dimensional sets of state equations by using projection techniques. These lead to a finite element representation of the distributed parameter system. Where applicable, these finite element models are combined with finite volume representations to describe storage variables that are—with good accuracy—homogeneous over sufficiently large space domains. The advantage of this combination is keeping the computational complexity as low as possible. Under these prerequisites, real-time applicable control algorithms are derived and validated via simulation and experiment for a laboratory-scale heat transfer system at the Chair of Mechatronics at the University of Rostock. This benchmark system consists of a metallic rod that is equipped with a finite number of Peltier elements which are used either as distributed control inputs, allowing active cooling and heating, or as spatially distributed disturbance inputs.