Many soft robotic systems for manipulation have been developed for their compliance and their smooth obstacles avoidance capabilities contrary to rigid systems. In order to increase human task aid, a new class of robots known as mobile soft manipulators has thus emerged, where the path planning of the whole system, both soft manipulator and its mobile platform, remains a real scientific challenge. For that purpose, in this paper, we suggest a curvature control algorithm for that class of hyper-redundant mobile soft manipulator approaching and handling objects with simultaneous obstacle avoidance based on potential field of velocity. The algorithm is based on principle of sliding mode, which converges in a finite time. The soft manipulator kinematics is modeled in 2D by the mean of Pythagorean Hodograph (PH) quintic curve theory with length constraints. The result of this modeling and control is applied on Festo Robotino-XT, mobile and soft manipulator robot.