In this work it is considered the problem of control during the contact transition period in robotic manipulators. Typically it is the force controller that acts during the transient period, however that controller is not prepared to deal effectively with impacts and losses of contact. In this work, it is initially performed an analysis of the stability and performance of conventional force controllers working during the contact transition. The analysis is based on simplified models for rigid and flexible manipulators. It is proved that the impacts do not cause dynamic instability, but they can severely degrade the system performance. Later, with the purpose of getting more realistic models to validate the effectiveness of new controllers, a model of a two-link rigid-flexible manipulator is developed considering glued piezoelectric sheets along the flexible arm. Contact models are also studied. Finally, three new controllers are presented which are designed to specifically deal with impacts and losses of contact during the contact transition period. The main idea of the first controller is to identify the first and unavoidable impact and then to reformulate the trajectory that the endeffector will follow to approach the collision surface with a minimum velocity, thus preventing new impacts. The controller is designed by using the theory of optimal control. The second controller is based on the equation of the motion of a flexible manipulator linearized around the motion of the manipulator when all the links are considered rigid. The obtained equation is used to design a high precision position controller to prevent or lessen the severity of the initial impact. The idea of the third controller is to actively damp the flexible part of the manipulator through the piezoelectric sheets that act as collocated actuators and sensors, this way the stability in presence of residual dynamics is guaranteed. The controller design is formulated as an optimization problem that is solved through nonlinear programming techniques.