ABSTRACT
Rotary actuators are electromagnetic devices developing mechanical torque with limited rotary motion. Because of their simplicity and low cost, they are finding more and more industrial applications. The demand for rotary actuators is expanding rapidly, particularly in the automotive industry, where they are being used in steering assistance, EGR, power door locks, and other applications. Some applications are more demanding, requiring an exceptionally high torque level, symmetry, and a stable equilibrium position. In particular, for steering wheel assistance, these requirements would ensure a neutral steering wheel position. This chapter describes three types of rotary actuators with multipolar PMs featuring a high force density transverse flux configuration, which performs a spring action by developing electromagnetic torques with limited-angular movement (Harris et al. 1975, Hennenberger and Bork 1997, Mercow et al. 1990, Weh et al. 1990). Because of the magnetically complicated and nonsymmetrical rotary actuator configurations, the analysis of the magnetic field for these actuators is based on FE software (Ansoft 1991, Nehl et al. 1988). The analysis, which is well supported by test results, shows that these actuators have the capability of developing symmetrical magnetic forces in both directions of rotation with a stable equilibrium position, satisfying all design requirements.
