Development of a vane motor servo system for precision positioning in an MRI- or CT-environment

Electromechanical actuators are widely used in a range of applications because of their excellent speed, torque, and bandwidth characteristics. In a CT/MRI-environment, their application is limited as the materials used can cause damage to the system and patient or degrade image quality. There is a need for precise actuators that can function in a CT/MR-environment without the aforementioned complications. Various systems have been developed for use in a CT- or MRI-scanner. However, these systems generally suffer from not being completely MRI-compatible or from having poor precision or speed characteristics. The main objective of this thesis is to develop an actuator system that can be used to precisely position a needle guide in a CT- and MRI-environment. The chosen actuator is a pneumatic vane motor. A system design of control valves and tubes is made in favour of precision positioning. A non-linear model of this system is constructed and translated to a proof-of-principle set-up. System identification is performed for this set-up and various controllers are designed. Performance is evaluated for several scenarios, including that of control valves not being present in the MRI bore, but at a distance of 5 meters from the actuator.