Patent Number: 7,711,463

Title: Electric power steering system

Abstract: An electric power steering system includes: a band-stop filter 15a having a transfer function G.sub.1(s) for suppressing resonance, and a phase compensator 15b having a transfer function G.sub.2(s). The above function G.sub.1(s) is represented by an expression G.sub.1(s)=(s.sup.2+2.zeta..sub.11.omega..sub.1+.omega..sub.1.sup.2)/(s.s- up.2+2.zeta..sub.12.omega..sub.1+.omega..sub.1.sup.2), where s is a Laplace operator, .zeta..sub.11 is a damping coefficient, .zeta..sub.12 is a damping coefficient, and .omega..sub.1 is an angular frequency. On the other hand, the above function G.sub.2(s) is represented by an expression G.sub.2(s)=(s.sup.2+2.zeta..sub.21.omega..sub.2+.omega..sub.2.sup.2)/(s.s- up.2+2.zeta..sub.22.omega..sub.2+.omega..sub.2.sup.2),where s is a Laplace operator, .zeta..sub.21 is a damping coefficient, .zeta..sub.22 is a damping coefficient, and .omega..sub.1 is an angular frequency. Furthermore, the above damping coefficients .zeta..sub.21, .zeta..sub.22 satisfy an expression .zeta..sub.2124 .zeta..sub.22.gtoreq.1.Thus, a filter such as a phase compensator may attain a design freedom while preventing the increase of arithmetic load, whereby both the suppression of resonance and a good assist response in a normal steering speed region, for example, may be achieved.

Inventors: Oya; Toshiaki (Sakai, JP), Sakamaki; Masahiko (Okazaki, JP)

Assignee: JTEKT Corporation

International Classification: B62D 6/00 (20060101)

Expiration Date: 5/04/12018