An exemplary controller includes a control valve that includes an electric actuator operatively coupled to a valve stem, a piston operatively coupled to one or more hydraulic fluid paths controlled by the control valve and including a piston shaft, a rotatable shaft operatively coupled to the piston shaft and mechanically isolated from the valve stem and capable of adjusting geometry of the variable geometry turbine, and an electronic sensor capable of sensing an angular position of the rotatable shaft. Various other exemplary systems, methods, devices, etc., are also disclosed.