A control system for installation on a vehicle having an engine, an hydraulic pump coupled to the engine to be driven by the engine, a steering assembly, a first hydraulic line configured to supply the steering assembly with a first portion ( Q s) of an output flow rate of said pump based on a flow rate request of the steering assembly, a second hydraulic line configured to supply an auxiliary hydraulic unit with a second portion ( Q a) of said output flow rate, the auxiliary hydraulic unit being adapted to be installed on the vehicle and to drive an implement thereof with a constant rotational speed when the supplied second portion ( Q a) is constant, and a control valve mounted on the second hydraulic line for adjusting the second portion ( Q a) as a function of a control input ( I a); the control system comprising - first means (T1, ECU) for evaluating a speed value of an engine output speed ( n) of said engine at a first instant; - second means for evaluating a first control value of said control input ( I a) at said first instant; - third means (T1, ECU) for evaluating a first time variation of the engine output speed ( n) over a first time interval from said first instant to a second instant; and - a control unit associated with said first, second, and third means (T1, ECU); wherein the control unit stores at least one mapping for determining a first coefficient ( K 2) as a function of said control input ( I a); and the first coefficient ( K 2) being a ratio of a second coefficient ( K 1) to a third coefficient ( K 3); the second coefficient ( K 1) representing the ratio of the second portion ( Q a), as a function of said control input ( I a), to a difference between said output flow rate and the first portion ( Q s); and the third coefficient ( K 3) representing a partial derivative of the second coefficient ( K 1) with respect to said control input ( I a); wherein the control unit is configured to: - determine the first coefficient ( K 2) as a function of the first control value; - computing a first parameter as the negative of a product of the determined first coefficient ( K 2) and a ratio of said first time variation to the speed value; - emit said control input ( I a) at said second instant with a second control value being equal to a linear combination of a plurality of parameters including the first control value and the first parameter. - first means (T1, ECU) for evaluating a speed value of an engine output speed ( n) of said engine at a first instant; - second means for evaluating a first control value of said control input ( I a) at said first instant; - third means (T1, ECU) for evaluating a first time variation of the engine output speed ( n) over a first time interval from said first instant to a second instant; and - a control unit associated with said first, second, and third means (T1, ECU); wherein the control unit stores at least one mapping for determining a first coefficient ( K 2) as a function of said control input ( I a); and the first coefficient ( K 2) being a ratio of a second coefficient ( K 1) to a third coefficient ( K 3); the second coefficient ( K 1) representing the ratio of the second portion ( Q a), as a function of said control input ( I a), to a difference between said output flow rate and the first portion ( Q s); and the third coefficient ( K 3) representing a partial derivative of the second coefficient ( K 1) with respect to said control input ( I a); wherein the control unit is configured to: - determine the first coefficient ( K 2) as a function of the first control value; - computing a first parameter as the negative of a product of the determined first coefficient ( K 2) and a ratio of said first time variation to the speed value; - emit said control input ( I a) at said second instant with a second control value being equal to a linear combination of a plurality of parameters including the first control value and the first parameter. - determine the first coefficient ( K 2) as a function of the first control value; - computing a first parameter as the negative of a product of the determined first coefficient ( K 2) and a ratio of said first time variation to the speed value; - emit said control input ( I a) at said second instant with a second control value being equal to a linear combination of a plurality of parameters including the first control value and the first parameter.