Application Of Magnetic Flux Modulation In Robot Servo Motor With High Torque Density

Industrial robots characterized by high operation precision,good repeatability,and high efficiency.They have been widely used in the industry applications.The amount of robot installed in china has increased year by year.Moreover,industrial robots have been included in the ten key areas in the “Made in China 2025” plan.As the heart of the robot,the robot servo motor must have fast response,high starting torque,large torque to inertia ratio,wide speed range,small size,light weight,and high overloading capacity.At present,there is still a gap in the high-performance servo products in China.Domestic servo motor with low torque density,large volume,heavy weight,can not adapt well to the needs of robot industry.Aiming at the technological gap,this thesis studies on servo motors with high torque density.Taking the performance parameters of a certain type of servo motor as the goal,a prototype is designed and processed.Research are conducted from both design theory and processing technology.The performance of a motor closely relates to the design and processing.In the case of limited processing condition,the design is difficult to achieve the expected goal.Therefore,this thesis optimizes the design of motors,using the theory of magnetic flux modulation.The slot opening is used,rather than a magnetic modulation ring,to change the distribution of magnetic conductance in the air gap,resulting in magnetic flux modulation.The difference from previous studies is that while the flux modulation motors in previous studies use distributed windings,completely relying on magnetic flux modulation to generate sub-harmonics and produce torque,the motor in this thesis uses concentrated windings,taking the magnetic flux modulation as an aid to further improve the torque density.This thesis discusses the design methodology from three aspects: theoretical analysis,model verification,and scenario comparison,proving that the magnetic flux modulation improves the torque performance,improves the voltage waveform,reduces copper loss.As to the problem that the sub-harmonics aggravate the iron loss,the thesis also have discussions.It’s concluded that the iron loss in the motors with medium or low fundamental frequency increases not as much as the copper loss decrease,and the total loss reduces.This thesis further promotes the design theory.After introducing the star of slots theory,the concept of the major sub-harmonics is proposed.It’s proved that the stator magnetic field of the concentrated windings with fractional slots and the rotor magnetic field modulated by the slot opening have their major sub-harmonics consistent in order,rotating direction and speed.As a result,the magnetic flux modulation is applicable to concentrated winding motors of all slot-pole solutions.Then three different slot-pole solutions are compared,which are 42-slot 32-pole motor,36-slot 32-pole motor,30-slot 32-pole motor.It is pointed out that the magnetic flux modulation has different degrees of influence in motor performance under different slot-pole solution.The slot-pole solutions enhanced most in performance by applying magnetic flux modulation are concluded.Finally,the design in this thesis is verified by experiments.The prototype achieves the design goal well in terms of load and overload capacity,loss and efficiency,and has a high power factor and low temperature rise.