This paper proposes a control scheme for handling surgical instruments by a single port access surgery robotic platform. This scheme is based on a Hidden Markov Model for detecting interaction with tissue inside the abdomen and a Kalman filter measurement fusion method for estimating the fulcrum point using forces and torques exerted on several instruments. In order to perform movements taking into account the estimated fulcrum point, a parallel force-position control algorithm is proposed in order to minimize exerted forces in the patient's abdomen. At last, proposed control scheme has been implemented in a surgical robotics platform composed by two manipulators and experimental results are shown in order to demonstrate how it works.