The general idea of interest of this Master thesis project is the increasing demand for micropropulsion systems for miniaturized spacecraft. The developments and deployment of these satellites increased rapidly in the last decade. CubeSats and more recently PocketQubes are an interesting opportunity for lower budget organizations or universities. The ability to control the motion of these satellites becomes more important and hence a propulsion system is required.

This thesis presents the first steps in the development process of a dedicated control system for the vaporizing liquid micro-resistojet (VLM) of the Delft University of Technology. The produced thrust of the micropropulsion system is regulated by two main control parameters: temperature and pressure. The report proposes a different control mechanism for each control parameter and three different operational envelopes. The first two operational envelopes are solely designed for the experimental phase of the project, to examine the behavior of the control system on the separate control parameters. The final operational envelope could be used to control the propulsive operation of the VLM concept. An analysis of the measurement delay is made, to decrease the sampling time of the control loop. Two controllers, namely proportional-integral-derivative (PID) for the temperature and sliding mode control (SMC) for the pressure have been proposed.

The designed hardware is based on the requirements of the operational envelopes and control strategies. The control system can be divided into three main parts: microcontroller, temperature controller and pressure controller. The Arduino Uno is selected to be used during this phase of the development process. The temperature controller is combination of an adjustable power supply and a measurement setup. The adjustable power supply is a buck-boost converter that is controlled with two digital potentiometers connected to its feedback pin. The digital potentiometer combination has 2806 different output steps, resulting in an output resolution of 0.89 mV. The chamber temperature is determined with resistance measurements of the heater chip using voltage and current sensors. The current measurement results are unfortunately not sufficient for accurate temperature measurement, the sensor should be replaced in future projects. The chamber pressure is regulated by a ON/OFF valve at the inlet. The controller hardware is based on the requirements of the selected solenoid valve. It contains a boost converter and switching circuit to create the desired spike voltage at the solenoid valve. The energy requirements of the solenoid valve exceed the energy level of the propulsion subsystem.

The designed control system did not meet all the expectations. The temperature measurement system needs to be improved and an additional storage devices should be added to fulfil the requirements of the propulsion system. The biggest challenge that followed from this thesis project is the complex trade-off between sampling time, measurement accuracy, system dynamics and power usage. An optimal balance between these parameters is essential to make it suitable for missions in miniaturized spacecraft like the Delfi-PQ.

In recent years the field of wireless charging has seen remarkable developments. More and more devices like mobile phones and laptops can be charged wirelessly, and larger equipment like electric vehicles are likely to follow the same path. The air gaps over which the power can be transferred keeps increasing, as do the
amount of power that can be transferred and the power transfer efficiency. Though combining these three key requirements has turned out to be a problem, since there always seems to be a trade off. This thesis will focus on the design process and the result of a wireless charger for hand held devices like mobile phones. This thesis will only describe the receiver side of the wireless power transfer system. The requirements were an output of 5V at 5W, over an as large as possible air gap with an efficiency of at least 60%. After the complete circuit had been designed and assembled an efficiency of 67.8% at a distance of 2.5cm had been obtained, which satisfies the requirements.