Automobiles electric motor assisted steering in which an upper limit is fixed for the electric motor current on the basis of a power function of motor current

摘要

Electrical system includes upper motor current value limiter (33) fixing the value of the upper current limit (Imax) on the basis of a motor current power function (Ilpf(k)) in which the exponents of an exponential function of the power function are in the range: 1 <= exponent <= 2. The upper current limit is fixed on the basis of the power function for the difference between the motor current and a motor current power reference function. The electrical system includes a motor (6) current sensor; a motor drive circuit (4) with various operating modes, in which the constants of the power functions are switched in response to modes of operation of the drive motor circuit. The power functions (Ilpf(k)) are time delayed by predetermined functions for fixing the motors upper current limit (Imax); a microprocessor (3) detecting incremental temperatures of system parts, in which the upper motor current value limiter (33) adjusts the upper limit (Imax) in response to the temperatures detected by the microprocessor (3). The upper current limiter calculates a number of upper limit values of motor current by using a number of power functions and selects one value from several upper current limits.