Overview I'm trying to levitate a constrained permanent magnet with 2 electromagnets. I'm having trouble conceptualizing the control system for such an operation. Setup The permanent magnet is fixed onto a horizontal pendulum and is repelled by an electromagnet above and repelled by an electromagnet below. The pendulum is attached to a rotary encoder that provides the absolute angle of the pendulum with respect to the horizontal. Goal Given a desired angle (relative to the horizontal), I need to change change the voltage going to each electromagnet. For example, if I want the pendulum to be at +25 degrees, the control system would increase voltage to the electromagnet below the pendulum and decrease voltage to the electromagnet above the pendulum, resulting in a net upwards force. Problem I was advised to use a PID controller. I'd heard of, but never used, a PID controller, so I researched them a bit online, and I understand the general idea--it's just like somebody adjusting water temperature before showering. However, my intuition tells me that I cannot use a single PID loop to control the two electromagnets because I'd be using a single input to solve two outputs. It'd be like saying f(x) = y1 and f(x) = y2 where f is a linear function. Since that's not possible for a linear function--and PIDs are linear control systems--then I cannot control 2 motors with a single PID controller. Am I right? If so, could you point me towards how people have solved similar problems? I feel like this is a common problem with control systems. If I'm wrong, could you provide an example? Many thanks!