Master (MSc) Thesis ''Structural Dynamics… at OHB Sweden · Stockholm

Mechanical disturbances from spacecraft equipment, such as reaction wheels, can couple into the satellite structure and affect sensitive payloads. Previous work at OHB has investigated methods for estimating reaction-wheel parameters from measured waterfall plots.

The purpose of this thesis is to develop a simple and cost-effective experimental setup for characterizing relevant dynamic parameters and evaluating structural or damping improvements.

The proposed concept is a flexible plate or table supported by springs and instrumented with accelerometers and/or force sensors. The work will combine analytical modelling, finite element analysis, and measurement data to identify parameters such as stiffness, damping, and modal properties.

The long-term objective is to establish a fast in-house method for comparing structural and damping concepts before formal qualification testing.

Possible future applications include evaluating bracket designs, elastomeric damping concepts, and other structural interfaces.

Job overview:

The thesis will focus on developing and validating a method for identifying mechanical parameters from vibration measurements.

The student will design and model a simplified test setup, define suitable measurement methods and investigate how sensor data can be translated into physical parameters of the test object. The method will first be verified using simulated data with known parameters.

The core scope includes modelling, parameter identification, test-jig design and uncertainty assessment. Depending on progress, available hardware and budget, the thesis may also include manufacturing and experimental testing of the setup.

The thesis will follow a top-down approach, starting with a deliberately simple and well-understood mechanical system. Once the modelling and parameter-identification method has been validated, individual design changes can be introduced and their effect quantified relative to a baseline.

The tasks of the master's thesis topic are as follows:

• Develop and evaluate concepts for the proposed test jig, instrumentation, and measurement quantities.
• Develop an analytical and/or finite element model of the test setup.
• Develop a method for estimating mechanical parameters from measured responses.
• Verify the method using simulated data with known parameters.
• Perform sensitivity and uncertainty analyses.
• Design a practical test jig based on a flexible plate or table supported by springs.
• Evaluate how the setup can be used to compare changes in brackets, damping materials, or structural interfaces.
• Document recommendations for further development and use at OHB.

If time and resources allow, the work may also include manufacturing of the test jig and validating the method experimentally using a motor, engineering model or available reaction wheel.

A secondary application may be investigated using impact-hammer excitation to measure transfer functions through brackets or structural interfaces.

The required candidate’s skills are:

• Master's-level student in Mechanical Engineering, Engineering Mechanics, Aerospace Engineering, Applied Physics or related field.
• Very good understanding of mechanics, vibrations, and structural dynamics.
• Experience with analytical or finite element modelling, preferably Optistruct/Hypermesh or MSC Nastran
• Interest in experimental mechanics and hands-on engineering.

Preferred:

• Background in precision metrology and instrumentation.
• Experience with MATLAB, Python or similar tools.
• Experience with accelerometers, force sensors, or vibration measurements.
• Knowledge of modal analysis, parameter identification, or uncertainty analysis.

What can we offer the student for them to succeed in their master's thesis?

• Supervision from engineers working with spacecraft mechanics and structural dynamics.
• Access to relevant previous work.
• Support with simulation, measurement, and experimental methods.
• Access to available sensors, laboratory equipment and representative hardware where applicable.

Successful thesis work may also open a path towards future employment within the Mechanical & Thermal team at OHB Sweden.