Active Force-Balancing Control for Micro-Gravity Sensors
Supervisor: Dr Karl Toland
School: Physics and Astronomy
Description:
The project aims to design, implement, and validate a closed-loop force-feedback control architecture for the University of Glasgow’s microgravity sensor platform (“Wee-g”).
Wee-g is a pioneering micro-electro-mechanical system (MEMS) gravimeter that has contributed to the emergence of a rapidly growing MEMS gravimetry field. MEMS gravimeters are increasingly being developed worldwide as compact, low-cost, and portable alternatives to conventional relative or quantum gravimeters, enabling new applications in environmental monitoring (volcanoes, groundwater), subsurface characterisation (sinkholes, abandoned mine shafts), and defence and security (gravity-aided navigation, buried hazard detection). MEMS devices use a suspended micro-scale proof mass whose displacement in response to gravitational acceleration is measured electronically. In most current implementations, this displacement is measured in an open-loop configuration, without actively stabilising the proof-mass position. As a result, performance is highly sensitive to drift, temperature variation, and fabrication tolerances, limiting dynamic range, bandwidth, and long-term stability.
Active force-feedback control can transform such devices into force-balancing instruments. Rather than measuring displacement directly, a feedback force can maintain the proof mass at a fixed operating point, and the control signal required to hold equilibrium then becomes the measurement output. This approach, widely used in high-performance macroscopic gravimeters and seismometers, reduces drift sensitivity while improving linearity, dynamic range, and bandwidth.
The student will develop a dynamic model of the coupled mechanical–electrical system underlying Wee-g, capturing proof-mass mechanics, actuation response, and readout dynamics. Drawing on established graduate-level concepts from control theory and vibration systems, the student will analyse stability margins, loop bandwidth, and noise propagation relevant to closed-loop operation.
The modelling framework will be implemented in MATLAB/Simulink to simulate system behaviour, and a digital feedback controller (e.g., PID or state-space formulation) will be designed and validated in both time and frequency domains. The final controller will be deployed to embedded hardware using automatic code generation tools.
Experimental characterisation on a real Wee-g sensor will benchmark open- and closed-loop performance using quantitative metrics including noise spectral density, bandwidth, linearity, and drift stability, establishing a validated framework for closed-loop MEMS gravimetry.
The project will provide the student with practical training in advanced control engineering, embedded implementation, and precision sensor characterisation within a state-of-the-art MEMS platform. For the research group, the validated closed-loop framework will strengthen ongoing efforts to enhance the robustness and deployability of Wee-g platforms, supporting broader work in resilient sensing and position, navigation, and timing technologies, as well as ongoing commercialisation activities through a University spin-out.