620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
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One major problem of a continuous process like plastic extrusion is their incapability to deal with non-local gas pressure. This is an inherent problem because a continuous process has an open end in the feeding port where pressure can escape. In this study a novel feeding system was developed to enable granulate feeding into gas pressurized processes inside a single- or twin-screw extruder. With this apparatus gas pressure can be applied inside the extrusion process. The apparatus separates the pressurized extruder from the dosing equipment that feeds the extruder. It keeps the pressure inside the system while continuously feeding new material into the process. A small-scale prototype was designed for proof-of concept. The small size of the prototype was able to handle small amounts of granulates of around 100 - 200 g/h. An applied gas pressure of 8 bar was achieved. In future optimizations, throughput can be increased and maximum applied gas pressure towards 15-20 bar.
This article deals with the topic of damping the rates of a satellite after separation from the launcher by sensing the rates with magnetometers or gyroscopes and actually damping it with torquerods or thrusters.
In literature problems of this kind are treated by linearization which is not adequate here due to the high nonlinearity of the problem caused by the high gyroscopic torque. This paper addresses the observability and controllability of the rate dynamics for symmetric satellite bodies.
Furthermore, robust stability of any bodies is investigated by means of the Krasovskii–LaSalle principle which is a variant of Ljapunov’s Second Method. It is found that – apart from one exception - the system is robustly stable for certain conditions depending only on the gain matrix and not depending on the orbit, moments of inertia or initial conditions. The exception is that of the intuitive case of an equator type orbit, in which the satellite rotates around the magnetic field lines, in this case the satellite’s rate cannot be damped.
Several design configurations are analysed with respect to their performance and cost: Rate damping with magnetometers or gyroscopes as sensors, and torquerods and thrusters as actuators. The results are evaluated with respect to the time to reach the desired rate, the propellant and the power equivalent battery mass used.
The goal is to use the results to allow an AOCS equipment and architecture trade-off at an early project phase. The design of the rate damping control of the SWARM project is presented as an example and demonstrated with simulations.
This paper analyses the achievable performance of the orbit prediction for a geostationary satellite using clusters of electrical propulsion (EP) thrusters for station-keeping and a star tracker based attitude control system.
The challenge in the orbit prediction is that the real electrical propulsion thrust is known with limited accuracy only. In combination with thrust pointing errors, these inaccuracies can accumulate to large orbit position errors during long low thrust burn arcs.
The discrepancy between real and predicted satellite position is determined in terms of probability and as a worst case scenario.
This paper deals with the preparation of the Small GEO mission and the accommodation of a GPS receiver as an experiment. The expected benefits of using the GPS receiver for Small GEO are explained. The feasibility of using GPS for position determination is investigated by simulation using a MosaicGNSS receiver, which was stimulated by a Spirent RF signal generator. A procedure, how to evaluate flight data on ground is outlined. Success criteria of the experiment and the minimal size of the downlink stream required and reserved for the receiver TM are presented.
The problem dealt with in this paper is the analytical determination of the attitude of a rigid body which undergoes a given rate profile. Usually the attitude is determined by solving the kinematic differential equation numerically. For long lasting movements the outcome can cost computation time plus encountered losses in accuracy, which can be disturbing especially in optimization problems. This contribution solves the kinematic differential equation for certain rate profiles exactly and compares the results in accuracy and computation time with the standard procedures.
Position measuring devices with sinusoidal measuring signals are widely used in position-controlled servo drives in industrial automation, e.g., for machine tools or semiconductor production machines. Usually, the feedback signal for the speed or velocity controller is calculated from the measured position. Therefore, position measuring errors affect these control loops. This study presents an analytic error model that considers non-ideal sinusoidal measuring signals with basic deviations (amplitude differences, offset errors, and phase shift) as well as signal harmonics. The model was used to systematically investigate the influence of signal quality and the number of signal periods from position measuring devices on speed ripple, across a wide range of speeds. A test stand with a high-resolution reference angle measuring device was used to confirm the results.
A hybrid current and acceleration control is presented and shown to improve the load disturbance behavior of servo drives significantly without additional sensor effort. The feedback signal of the acceleration control loop is calculated from the position data of the motor encoder. Hence, position measuring errors influence this control loop and lead to speed ripple. Therefore, the presented design of the acceleration control loop considers both load sensitivity and position measuring errors.
Für eine Einführung in die fertigungstechnischen Grundlagen der Aufbau- und Verbindungstechnik sind im Wahlfach „Leiterplattentechnik Praktikum“ an der Technischen Hochschule (TH) Rosenheim Inhalte der Prozesstechnik und des Leiterplattendesigns miteinander kombiniert. Zu Beginn der Veranstaltung zeichnen die Praktikumsteilnehmer ein Layout für eine Leiterbahn-Teststruktur, welche anschließend im Haus gefertigt wird. Nach der Fertigung folgt eine elektrische und optische Charakterisierung zur Kontrolle der Prozessqualität. Die praxisnahe Erstellung eines einlagigen Layouts für eine LED-Taschenlampe auf Basis eines vorgegebenen Schaltplans und innerhalb einer begrenzten Platinenfläche sowie dessen Fertigung befähigen die Kursteilnehmer später, eigene Layouts für elektronische Schaltungen selbstständig zu entwickeln. Die anspruchsvolle, teilautomatische Bestückung einer zweilagigen, vorgegebenen SMT(Surface Mount Technology)-Leiterplatte, die ein FM-Radio mit Capacitive Touch-Steuerung bildet, rundet die erfolgreiche Qualifizierung in der Leiterplattentechnik ab.
Texas Instruments' MSP430 Launch Pad is used as a key component for remote labs that complement an introduction course to microcomputer technology in the bachelor program Mechatronic at the University of Applied Sciences in Rosenheim. The remote labs use breakout boards and include a timer experiment with generation of pulse width modulation signals, I2C communication and analog to digital conversion.
Reference design projects are implemented to the Xilinx Zynq on the Zedboard which is extended by user defined electronic hardware connected through the Zedboard's FMC (FPGA Mezzanine Card) connector. The implementation method with HDL Workflow Advisor includes constraint definitions for modified reference design projects for use with digital input and outputs and Zynq's XADC (Analog-Digital converter) which is characterized and compared to its data sheet. The bandwidth of the Zynq's internal AXI (Advanced eXtensible Interface) bus connected to the Simulink host PC is determined.
A DDR2 DRAM test setup is developed and implemented on the Griffin III ATE test system from HILEVEL Technologies. The test system provides a raw platform for performing various mixed signal and digital tests. In order to configure patterns easily in a vector format, a software platform is developed to manage test patterns according to the user's analysis needs. As examples, retention test patterns with disabled self-refresh are applied to 2 Gbit DDR2 SDRAM of two different DRAM vendors. The devices are characterized in respect to their intrinsic leakage and data retention behavior under the influence of stress conditions such as temperature or access algorithm. The tests are automated and test data is logged for an off-line data analysis. Data is recorded before and after solder simulation steps in order to observe a retention time degradation.
A DDR2 SDRAM test setup implemented on the Griffin III ATE test system from HILEVEL Technologies is used to analyse the row hammer bug. Row hammer pattern experiments are compared to standard retention tests.
The analysis confirms that the row hammer effect is caused by a charge excitation process depending on the number of stress activation cycles. The stress has to occur in the local neighborhood of the cells under test.
Shallow impurity levels support the responsible charge carrier transport process in the used DDR2 SDRAM technology