But if it gets any more complex, or things don't work out like you planned (ie, your car wildly revs and slows your car) you have to retreat and use MATH. That's control theory: how to use math to figure out how to make systems (anything that can be described as a differential equation, this includes physical, electrical - in fact almost anything even if you have to dumb it down) behave exactly how you want them to. The key in that last sentence is math. If something goes wrong with your cruise control system you could 'use math' to change your system to be something like 'IF CAR ISN'T GOING THE RIGHT SPEED PRESS DOWN ON THE GAS BY A*ERROR'. This WILL work better. But you don't know why. The reason is control theory, and until you understand what it is and how it works your cruise control just won't work right.
That is what controls engineers do - they use some tough math to make things behave correctly. It's not easy, it takes a long time to learn and a longer time to perfect. I have a master's degree in controls engineering, so trust me. Trust me also, that job postings like this make me angry:
An aluminum manufacturing company is seeking an ELECTRONIC CONTROLS ENGINEER. Candidates must have 2 - 5 years experience with Allen Bradley PLC's in a manufacturing environment. Job responsibilities include programming process control systems, calibrating, repair and troubleshooting plant instrument, electrical and control systems. A Bachelor's Degree in Electrical Engineering is required. Excellent benefits package available including matched 401k, company-shared health/dental, and paid life insurance. Salary is commensurate with experience.What's a PLC? I never heard of that in my controls classes. Processes? Plant instrumentation? What are the inputs to my system? What am I controlling? Temperature? Shaft position?
Oh that's right. This job posting is abusing terms. They want an electronic controls engineer, but what they mean is a process controls engineer or manufacturing engineer. Their goal is process control: if I have a conveyor belt I need to know how fast it should go, where things on it are, what actions I have to perform now, etc. That's automation, and it's cool. PLC's are microcontroller systems with some nifty serial interfaces and analog components such as relays, TTL drivers, etc all built-in. Sometimes they use C for programming, sometimes they use BASIC. I know, ew, but it gets the job done. And it's a job that needs doing. But it's not controls engineering!
You couldn't take the person that automates that factory and put him in my chair. I've designed antenna control systems that can point to within an accuracy of .7 degrees using an embedded processor. I've modeled an entire dish antenna system (including mechanical, electrical and software components) in Simulink. These two things are NOT the same job. I'm not blaming anyone or saying anyone's at fault, but it's very frustrating. Ya'll feel me?