Steer-by-wire power steering system using actuators made transparent through use of local torque and/or force control loops

The invention relates to a steer-by-wire power steering system (1) comprising a lower-level mechanism (10) that includes a servo motor (11) and a steered wheel (12), and an upper-level mechanism (20)that includes a steering wheel (22) and an auxiliary motor (21), the lower-level mechanism (10) being closed-loop controlled, at zero force, by a lower local loop (30) comprising a feedback branch (32) that measures or estimates an actual downstream force (F10_actual) downstream of the servo motor (11) and upstream of the point of contact (12C) between the wheel (12) and the ground (2), so as to make the servo motor (11) transparent, while the upper-level mechanism (20) is closed-loop controlled, at zero torque, by an upper local loop (40) comprising a feedback branch (42) which measures or estimates an actual driver torque (T20_actual) between the auxiliary motor (21) and the steering wheel (22) so as to make the auxiliary motor (21) transparent, the lower (30) and upper (40) local loopsbeing controlled by a sing