This article presents a novel electrical/mechanical hybrid 4-redundancy brushless DC torque motor （BLDCM）, which has found applications in direct drive actuators （DDA） of aerial vehicles. This motor is characteristic of electrical/mechanical hybrid 4-redundancy by securing two stators along with two rotors on the same shaft. Each stator contains two sets of windings embed- ded in separated slots. Furthermore, compared to the scheme of two electrical dual-redundancy BLDCMs linked by a mechanical transmission, the proposed motor has lower volume and lighter weight, eliminates the nonlinearity caused by the gap of the me- chanical transmission, moderates the requirement for the torque balance between redundancies and reduces the cogging torque by shifting the magnets. Both magnetic circuit calculation and the finite element analysis （FEA） of the electromagnetic field are conducted to optimize the design process. A prototype motor has been produced and tested. The results indicate that its perform- ances comply with the requirements presented by designers. Moreover, the position frequency response of the prototype in the DDA＇s unloaded situation has also demonstrated the fulfillment of desired dynamic characteristics.
