This work present a loose guidance method for a passive-type omnidirectional mobility aid device named Omni RT Walker-II, which its motion is performed by shared control of user and controller. Guidance is performed by division of environment to accessible and inaccessible areas and the motion of walker-user system is constrained inside the accessible area called Potential Canal. This paper attempts at providing evidence to the fact that loose guide method is an approach to optimal guidance in the sense that when the control (constrain) of ORTW-II motion is loose, its motion pattern significantly resembles user's unconstrained motion. Healthy user's natural motion is hypothesized to be optimal and is compared with constrained motion pattern of ORTW-II for different settings of the Potential Canal. Experimental results are provided and discussed.