To improve the electromagnetic performance of the coaxial magnetic gear (CMG)

a novel Halbach array CMG is proposed in this paper. The inner rotor permanent magnets (PMs) adopt convex-T alternating arrangement to form Halbach array

while the outer rotor PMs is a combination of Spoke structure and Halbach array to improve the magnetic concentration effect. In addition

with the optimization objectives of high output torque and low torque ripple under the premise of maintaining the number of PMs

an optimization analysis is conducted based on sensitivity analysis using the response surface method and multi-objective genetic algorithm to determine the optimal parameters of the proposed CMG. A finite element model is established with the 4 and 17 pole pairs for inner and outer rotors

respectively. The proposed CMG can effectively improve the air gap flux density and reduce the non-working harmonics in the air gap

and the output torque is increased by 45.43% and 23.69%

compared with that of conventional and Halbach array CMGs respectively. Finally

a prototype is fabricated

and a test platform is built. The experiment verifies that the torque ratio and transmission ratio of the proposed CMG are basically consistent

and the efficiency can reach over 90%.