An omnidirectional passive walking aid system called "Omni RT Walker" (Omnidirectional Robot-Technology Walker) is proposed in this paper. Omni RT Walker consists of an omnidirectional platform with servo brake system, an onboard control unit and a frame. The system is called passive since it excludes motion generating parts such as wheel actuators and translates by force applied by its user, but includes controllable units; servo brakes in our prototype. Variable Dynamics Control is the control scheme applied to Omni RT Walker in order to modify its dynamic characteristics according to user's walking ability. System identification is performed to evaluate and validate this control scheme.