Control system for a variable-geometry turbocharger

Control system for a turbocharger with variable geometry, in which an internal combustion engine is coupled to a variable geometry turbocharger (4); characterized in that said system comprises: - a first control device (41) which supplies a first control signal (P1) destined to rule (30) the geometry of said turbocharger on the basis of at least a first signal pM correlated with air flow supplied to the engine (3) by the compressor (6) of said turbocharger (4); - A second control device (43) supplying a second control signal (P2) destined to rule (30) the geometry of said turbocharger on the basis of a second signal pT correlated to the pressure of exhaust gases supplied to the turbine (10) of said turbocharger (4); - A third control device (46) which supplies a third control signal (P3) destined to rule (30) the geometry of said turbocharger on the basis of a third signal nT correlated to the rotation speed of said turbocharger (4); said first (41), said second (843) and said third (46) control devices provide, when used, a first (100, 100a), second (200; 200a) and third (300; 300a) respective modes of operation ; He said turbocharger being governed alternately by at least two of said control devices (41, 43, 46) and being automatically switched government from a control device to another respectively from one operating mode to another, characterized in that switching from the second operating mode (200) to the first operating mode (100) occurs when at least the following condition is determined: - the first signal pM is close to a reference value pMref and the third signal nT does not exceed the threshold value nTlim, - and switching from the third operating mode (300) to the first operating mode (100) occurs when lasiguiente condition is determined: - the first signal pM reaches threshold value pMlim and the second signal pT does not exceed a respective pTlim threshold value.