Torque variation reduction in a synchronous motor used for automobile power assisted steering, uses iteration or Fourier transform to carry out harmonic analysis of motor phase current

摘要

In a preliminary stage the current ij is calculated by harmonic analysis by Fourier transform or iteration. The result of the calculation is stored in a table for each phase (j) as a function of the rotation angle of the rotor. The motor may be of the electric power assisted type (EPAS) or the electro-hydraulic power assisted type (EHPS). Method of reducing torque variation in a synchronous motor: (a) in a first preliminary stage the no load counter electromotive force (ej) is measured for each phase (j), followed by calculation of phase current (ij) in each phase (j) that is required to apply to the motor so that the torque Tm constant or practically constant, whatever is the angle of rotation of the rotor; (b) at the moment of motor use, the motor control applies to each phase (j) the current (ij) calculated as a function of the angle of rotation of the rotor. The motor torque Tm is taken from Tm = kT * (SUM j=1 to n (ej * ij)) where kT is a torque constant depending upon the type of motor used..