The authors are developing "Distributed Power Control System" of "Hard-Link-Type Mobility" using the mechanical coupling device. This mobility is subject to using the Small EV, and make it possible to connect or disconnect the vehicles as necessary. "Hard-Link-Type" has two merits. The first one is robustness in operational environments (the weather, the wireless interference, and etc.). The second one is safety because "Hard-Link-Type Mobility" become a normal tractor when the vehicle control system stop. In addition, the control system enables the mechanical coupling device to avoid the load while the mobility running. This paper describes the improvement points of the control system when assuming practical use.