This paper explores the control of a three-degree-of-freedom ungrounded rotational inertia generator that leverages the gyroscopic effect to render a prescribed inertia. A kinematic model is first established to identify the source of the instability observed with a previous version of the control system of the device. To address this instability issue, a novel control approach is then introduced and experimentally validated. Experiments are conducted in which a user actively rotates the device with prescribed simulated inertias that are set to 1, 2, 3 and 3.5 times the device's actual total inertia. In the experiments, the flywheels of the device are given an initial velocity of 105 rad/s in order to take advantage of the gyroscopic effect to render the proper inertia to the user. While this paper outlines the capability of the ungrounded device to render a prescribed inertia, it ultimately presents the continuous control of a double gimbal gyroscope that is physically limited by its joints.