The objective of the project is to design a feedback controller that regulates the output energy of the linear accelerator (LINAC) at the Spallation Neutron Source (SNS) facility by using beam position at the high energy beam transport (HEBT) achromat. After the LINAC accelerates a negative hydrogen ion bunch to 1 GeV of energy, the HEBT achromat bends the pulsed beam 90 degrees in the horizontal plane towards the accumulator ring. The beam trajectory through the achromat varies with energy dependant on the energy of the beam as it leaves the LINAC. Since output energy can not be measured directly, the beam position at a high dispersion location in the achromat is utilized as the indicator in the variations of output energy. To stabilize the energy, the position is used as the feedback variable to control the phase of the last cavity of the superconducting cavity LINAC (SCL). This project involves the design of a feedback control system to regulate output energy by varying the phase of the last SCL cavity depending on beam position at the HEBT achromat.