Identification and Inverse Torque Control of Hydrodynamic Dynamometers

Hydrodynamic dynamometers are employed in internal combustion engine test benches over the entire range of internal combustion engines, from cart engines up to large ship engines. They are inexpensive and characterized by a relatively small moment of inertia. However, nonlinearities and the absence of accurate models make the control of these dynamometers a difficult task, and so they are currently employed almost exclusively for stationary measurements. To overcome this limitation, this paper proposes an inverse torque control based on a Wiener approximation whose parameterization is strongly simplified by the choice of a suitable set of basis functions for the nonlinear map. Since the inversion of this nonlinear map would be computationally demanding, it is replaced by a dynamic inversion, which – together with the actuator redundancy – allows to incorporate additional optimality criteria. The performance of the proposed control law is validated by measurements on a test bench, showing significant improvements with respect to classical implementations.