PURPOSE: To ensure switching responsiveness in reducing a shock in time of a changeover without lessening the angle of a step motor available in switching the damping force of a shock absorber.
CONSTITUTION: The extent of damping force in a shock absorber is switched to more than two steps by the power of a step motor 4. In this case, a motor current is controlled so as, not to make a velocity at the initial stage (within the step angle) in time of transition exceed an angular velocity limit value θs as detecting an actual position θ. At this time, two processing elements 54 and 56 are selected by two switches SW1 and SW2, and both A- and B-phase currents Ia and Ib are controlled so as to become such an equation as Ia=j×θs×K×sinθ, Ib=j×θs×K×sin(θ+90°), and other than this, another processing element 52 is selected, whereby such a current as doing step drive is supplied. In this connection, j is a sign (±1) showing a current direction and K is gain. In place of closed loop control, a transfer velocity may be limited by a constant motor current control pattern.
TAJIMA FUMIO
SATO KENJI
MUTO MAKOTO
HITACHI AUTOMOTIVE ENG