Browsing by Author "Schäfer, Peter"

Now showing 1 - 4 of 4

Open Access
Application of parallel computing to robot dynamics
(1993) Schäfer, Peter; Schiehlen, Werner
In this paper an approach for the application of parallel processing to the dynamic analysis of robots based on the multibody system method is presented. The inherent structure of the symbolic equations of motion is used for partitioning those into independent modules for concurrent evaluation. The applied strategies for parallelization include the parallel evaluation of subsystem equations and the parallel computation of the inertia matrix along with its factorization, and of the force vectors and control inputs. The implementation of the parallel structures is discussed with respect to optimal utilization of transputer resources. The presented approach yields a strong reduction of computing time and supports real-time simulations of controlled robots, which is also shown in an example.
Unknown
Fuzzy control of speed limiter
(1993) Thurn, V. M.; Schäfer, Peter; Schiehlen, Werner
Future regulations of the European Community (EC) require a speed control for the limitation of truck speeds on the European roads. Today's speed limiters consist of an adaptive PID-controller. However, the resulting truck behaviour is not satisfactory compared to an experienced driver. Therefore, the human experience has to be used to improve the design. Some fundamental aspects for the development of a Fuzzy-Logic-Controller (FLC) for limiting the truckspeed are presented in the paper. Simulations of a controller with one and two input variables are shown. It turns out that a FLC can be interpreted as a highly nonlinear control. The resulting control law will be discussed.
Open Access
Group diagrams for simplified representation of scanpaths
(2023) Schäfer, Peter; Rodrigues, Nils; Weiskopf, Daniel; Storandt, Sabine
We instrument Group Diagrams (GDs) to reduce clutter in sets of eye-tracking scanpaths. Group Diagrams consist of trajectory subsets that cover, or represent, the whole set of trajectories with respect to some distance measure and an adjustable distance threshold. The original GDs allow for an application of various distance measures. We implement the GD framework and evaluate it on scanpaths that were collected by a former user study on public transit maps. We find that the Fréchet distance is the most appropriate measure to get meaningful results, yet it is flexible enough to cover outliers. We discuss several implementation-specific challenges and improve the scalability of the algorithm. To evaluate our results, we conducted a qualitative study with a group of eye-tracking experts. Finally, we note that our enhancements are also beneficial within the original problem setting, suggesting that our approach might be applicable to various types of input data.
Open Access
High-dynamic test bed for mechatronic vehicle suspensions
(1993) Schäfer, Peter; Schiehlen, Werner
Advanced vehicles are mechatronic systems consisting of mechanical parts like rigid bodies, flexible tires, bearings, joints, springs and dampers as well as electronic components including actuators, control devices and sensors. In particular the electronic parts have to be tested rigorously by realistic loads. For this purpose a high-dynamic hydraulic test bed for actively controlled vehicle suspensions has been developed. The timevarying loads are obtained from a real-time simulation of multibody systems equations representing the mechanical parts of the vehicle. The test bed is operating up to frequencies of 35 Hz without dynamic errors in amplitude and phase.