This paper describes an approach to controlling the force generated by a piezoelectric actuator (PEA) accurately without using any force sensor. A model PEA is proposed that includes a new asymmetric hysteresis operator and that takes the external force into account. A detection model is deduced that allows computation in real time of the PEA elongation and generated force starting from the measurement of the driving voltage and current. This detection model is used to replace a force sensor for closed-loop force control of a PEA. Experiments are carried out using 2 PEAs in an experimental setup. The first actuator is the controlled actuator, and the second one is used as a dynamic controllable mechanical load. It is shown that a good control performance can be obtained whatever the mechanical loading conditions.