Research On Rotating Armature Permanent Magnet Synchronous Motor With Limited Rotating Angle For Driving Biomimetic Fish

Nowadays,the fractional-slot concentrated-winding(FSCW)motors are widely used in low-speed high-torque applications.On one hand,the pole number and slot number of fractional-slot motor are close,and the pole pair number is large.With large least common multiple of slot and pole number,the amplitude of the FSCW motor cogging torque is smaller.On the other hand,concentrated winding can effectively cut down the end length of motor winding,making the coil assembly simple,reducing copper consumption,and decreasing temperature rise.In this research,the electric waist joint motor for biomimetic fish drive is taken as the object of study,hereinafter referred to as waist motor.At first,combined with the theory of hydrodynamics,the mechanical analysis of biomimetic fish caudal fin is carried out according to the fish body size,the fish body structure and the flapping pattern of caudal fin.The output torque and power of motor are acquired through installation position,rotating angular velocity and force on caudal fin.In accordance with the design requirements,the preliminary design of the waist motor is carried out.Because the torque is proportional to the square of air gap diameter,the structure of external rotor is selected.While,considering the limitation of installation space and the limited operation angle of waist motor,the topological structure is changed based on the traditional external rotor structure,and the rotating armature structure with limited rotational angle is adopted to better meet the demand.The pole-slot combination is 60-pole and 54-slot.On this basis,the weight and efficiency constraints are introduced to optimize the design.The optimum design mainly aims at the pole arc coefficient and tooth width.After determining the pole arc coefficient,under the premise of fixed torque and other conditions,the relationship between the motor efficiency,saturation degree of magnetic flux density of silicon steel sheet,motor copper consumption and tooth width is explored to determine the optimum design scheme.The stress field of the waist motor is analyzed to ensure the structure design is reasonable.Meanwhile,according to the operation mode of the waist motor,the operation efficiency is analyzed,and the thermal field is analyzed under the rated operation state.It is determined that the temperature rise of the design scheme is low,without need to introduce additional cooling facilities.Finally,the life test platform of the designed waist motor prototype is constructed.After the life test,it is found that the error between the efficiency measured of the waist motor and the efficiency calculated through efficiency map is small.It shows that the design and analysis of the waist motor is reasonable,and the output torque and operation efficiency can meet the requirements.