A robotic heart motion simulator (HMS) is developed at DLR (German Aerospace Center) to accurately simulate real translational motions of a mechanically stabilized beating heart in a lab environment. This simulator is part of the DLR scenario for motion compensation on the beating heart. Motion compensation is a highly desired issue in minimally invasive surgery. The design of the HMS as well as its derivation of inverse kinematics, closed-loop dynamics, and proposed control structures are presented. The simulator is evaluated in the lab environment to prove its capability to precisely simulate low-amplitude translational motions of a stabilized beating heart.