In this paper, we address the co-manipulation problem for the handling tasks through a viewpoint that we do not think sufficiently explored, even it employs classical tools of robotics. Usually, this problem is tackled through the control objective based on impedance control. We consider that this force is the only exchanged physical signal, showing the robot how to move according to the willingness of the human operator. Indeed, this force gives the desired direction of displacement at every moment, a displacement that should remain under the operator's authority. Moreover, for safety purposes, the velocity of displacement should be imposed to avoid hazardous behavior. As a result, dealing with co-manipulation consists in realizing two functions in order to perform a controlled power amplification. The first is the online trajectory generation of an appropriate trajectory. The other lies in the design of a control structure allowing a good trajectory tracking. The overall strategy is illustrated with the co-manipulation problem of a robot that handles a pendulous load.