Turbocompound internal combustion engine

Turbocompound internal combustion engine (1) comprising a drive shaft (19), a turbocharger (2) comprising a turbine (3) and a compressor (4); an auxiliary turbine (13) located along the path of the exhaust gas, downstream from said turbine (3) of said turbocharger (2); and transmission means (20) between said auxiliary turbine (13) and said drive shaft (19); a first sensor (28) of the angular velocity to detect the rotation speed of said auxiliary turbine (13); and a control device (31) for controlling the rotation speed of said auxiliary turbine (13), which is connected to said first sensor (28) and which in turn comprises calculating means (34, 36, 40, 41 ) for calculating a range of permissible values ​​of said rotation speed of said auxiliary turbine (13), comparison means (42, 54) for comparing the rotation speed of said auxiliary turbine (13) measured by said first sensor (28) with said range of permissible values, and control means (38, 39) for controlling operating parameters of the engine (1) in response to an authorization signal (O1) generated by said comparing means (42, 54) so said speed of said auxiliary turbine (13) remains within said range of permissible values, said engine being characterized in that said calculating means (28, 36, 40, 41) for calculating said range of permissible values ​​comprise a second sensor ( 34) of the angular velocity to detect the rotation speed of the drive shaft (19); and processing means (40, 41) for calculating at least a maximum value of the speed of said auxiliary turbine (13) based on the speed of the drive shaft (19).