You don't say what you are studying and whether you want to focus on hardware or software aspects.
Also what would you like to control?
I have worked on control of industrial scale chemical plants and chemical manufacture, up to 500kW inertia simulation dynamometers, end of line test rolling road machines, component test machines involving pneumatics, vacuum pump control, automated warehouse alarm and status monitoring (scenarios where there are lots of alarms that have to be classified and managed efficiently) , smoking machines (machines that smoke lots of cigarettes simultaneously), analysis and measurement of brake disc wear.
I am now thinking about the safe and cost effective control of molten salt reactors. Lots of thinking about failure and failure mitigation and most students I seem to remember don't want to think about failure and failure mitigation in advance. It's related to the fundamental and encouraging optimism of youth.
e.g. See "Licensing of safety critical software for nuclear reactors"
In this case you have to completely partition the control system between simple and reliable safety critical control elements (hardwired and fail safe trips etc) and the more complex and relatively unreliable "safety related" SCADA or DCS stuff.
To make this achievable in terms of a third year project someone would have to design you a simulation of a relatively simple nuclear reactor and you would have to design and build a licensable control system for it.