Design of a Noncontact Torsion Testing Device Using Magnetic Levitation Mechanism

Abstract

To facilitate torsion testing in special environments, a noncontact torsion testing device, where a noncontact torque can be transmitted to a specimen, was developed using magnetic levitation technology. A permanent magnetic gear is used to produce noncontact torque. In addition, four electromagnets and four attractive-type permanent magnetic bearings were employed to realize levitation; in more detail, the four electromagnets actively stabilized two levitation degrees of freedom (DoFs), while the four attractive-type permanent magnetic bearings passively stabilized four DoFs. Furthermore, a plant model considering the effect caused by the four attractive-type permanent magnetic bearings was built for the two levitation DoFs requiring active control. Based on the plant model, two PD-controllers were designed. Moreover, a control simulation was conducted to obtain appropriate PD-gains. Finally, experiments further validated the feasibility of the whole scheme, and it was proven that the device can apply a 0.126 N·m torque to the specimen while maintaining levitation.