The Linear Flexible Joint module consists of a passive linear cart coupled to an Linear Servo Base Unit through a linear spring. The Linear Flexible Joint is made of solid aluminum and uses linear bearings to slide along the Linear Servo Base Unit ground stainless steel shaft. As with the Linear Servo Base Unit, the Flexible Joint’s position is sensed using a rotary optical encoder whose shaft meshes with the track via a pinion. Two additional masses are supplied with the system and can be mounted atop the cart. As the Linear Servo Base Unit moves back and forth, the Linear Flexible Joint cart will naturally tend to oscillate. Using feedback control, one can attempt to attenuate these motions.