Recognition of degraded performance in a vehicle suspension system

A system for estimating damping characteristics of shock absorbers of a vehicle in an active or semi-active suspension system comprising:

• a plurality of adjustable damping shock absorbers, each shock absorber including a pressure chamber containing a damping fluid, a piston being slidable inside said pressure chamber, the position of which defines a lower pressure chamber and an upper pressure chamber, a by-pass chamber in communication with the upper pressure chamber, and a control valve, arranged to control passage of the damping fluid between the pressure chamber and the by-pass chamber;
• sensors detecting relative acceleration or relative movement between a vehicle body and each wheel with which a shock absorber is associated, and accelerations and movements of the vehicle body;
• and
• an electronic processing and control unit, adapted to receive signals indicative of said relative acceleration or said relative movement, and arranged to emit driving signals of control valves of the shock absorbers to achieve predetermined damping characteristics of the shock absorbers,
• the system comprising a processing module estimating degradation conditions of the shock absorbers, coupled at an input with said sensors and at an output with said electronic processing and control unit, arranged to perform a method comprising:
• providing a reference model indicative of a nominal relation between a road severity index, RSI, related to vertical acceleration values experienced by wheels of the vehicle while driving on a road section, and a quantity representative of a magnitude of a driving force of the control valves of the shock absorbers;
• acquiring respective relative acceleration or speed data of at least the front wheels of the vehicle with respect to the vehicle body;
• determining a value of the road severity index starting from said relative acceleration or speed data of the front wheels of the vehicle with respect to the vehicle body;
• acquiring values of a quantity representative of the magnitude of the driving force of the control valve of each shock absorber;
• for at least one shock absorber, comparing an acquired value of said quantity representative of the magnitude of the driving force with an expected value of said quantity representative of the magnitude of the nominal driving force determined as a function of said road severity index according to said reference model;
• and
• determining a degradation condition of a shock absorber if the acquired value of the respective magnitude of the driving force does not correspond to said expected value of the magnitude of the nominal drive force.