Electrically controlled linear actuator , said linear actuator including: • a frame , • an extensible device including a rod and a cylinder , said rod having, with respect to said cylinder , a degree of freedom in translation in an extension/retraction direction (D1) of said linear actuator , • at least one electric motor rigidly connected to said frame , said at least one electric motor including a drive shaft that can rotate with respect to said frame , • at least one conversion member for converting a rotational movement of said drive shaft of said at least one electric motor into a translational movement of said extensible device in said extension/retraction direction (D1), said at least one conversion member including an input shaft that can rotate with respect to said frame , said input shaft being driven in rotation by said drive shaft of said at least one electric motor , and also an output part that can translate rectilinearly with respect to said frame in said extension/retraction direction (D1), said output part being capable of moving, in a relative translational movement, said rod with respect to said cylinder or, alternatively, said cylinder with respect to said rod , and • automatic locking means for preventing said relative translational movement between said rod and said cylinder in at least one end position selected from a retracted end position of said extensible device and an extended end position of said extensible device , characterised in that said linear actuator includes an automatic disengaging/engaging system for mechanically disengaging said output part of said at least one conversion member from said extensible device or for mechanically engaging said part with said device, said automatic disengaging/engaging system being arranged in a disengaged state when said extensible device is positioned in at least one of said end positions selected from said retracted end position and said extended end position, said automatic disengaging/engaging system being arranged in an engaged state when said extensible device is positioned in an intermediate position arranged between said retracted end position and said extended end position. • a frame , • an extensible device including a rod and a cylinder , said rod having, with respect to said cylinder , a degree of freedom in translation in an extension/retraction direction (D1) of said linear actuator , • at least one electric motor rigidly connected to said frame , said at least one electric motor including a drive shaft that can rotate with respect to said frame , • at least one conversion member for converting a rotational movement of said drive shaft of said at least one electric motor into a translational movement of said extensible device in said extension/retraction direction (D1), said at least one conversion member including an input shaft that can rotate with respect to said frame , said input shaft being driven in rotation by said drive shaft of said at least one electric motor , and also an output part that can translate rectilinearly with respect to said frame in said extension/retraction direction (D1), said output part being capable of moving, in a relative translational movement, said rod with respect to said cylinder or, alternatively, said cylinder with respect to said rod , and • automatic locking means for preventing said relative translational movement between said rod and said cylinder in at least one end position selected from a retracted end position of said extensible device and an extended end position of said extensible device , <EOS>