Research Of A Bi-directional Electromagnetic Linear Actuator

Automotive electronic technology is the major element in new generation of automobiles.The function of actuator is to implement operation according to the control command issued by the electronic control unit(ECU).The performance of automotive electronic control system is directly determined by actuator.Compared with the rotary motor with motion conversion device,linear actuator has its remarkable advantages in quality,volume,response,etc.in the field of linear motion control.The linear actuator has become a hot spot in research.However,the pursuit of mass,volume,energy consumption,response and other performance of actuator is constantly improving in aviation,space flight,automobile,etc.fields.There are many challenges to develop a linear actuator with fast response and low power consumption simultaneously.Combination of theoretical analysis,simulating calculation and experimental verification,a bi-directional electromagnetic linear actuator with innovative structure is carried out in the thesis.High efficiency multi-objective optimization design method,effective multi-physical field coupling analysis method,sensorless landing control method and application of the actuator in SCR metering pump were conducted in-depth study.The main contents and results of this thesis are summarized as following:(1)An innovative moving-iron bi-directional electromagnetic linear actuator with single coil was proposed.The control scheme and electromagnetic field model of actuator were established.The influence of key structural parameters on the electromagnetic force of the actuator was analyzed.The steady-state energy consumption is reduced effectively by holding force.The force performance of the actuator can be improved by structural parameters design.All above provides a foundation for follow-up studies,such as structural optimization,dynamic characteristic analysis and control technology development.(2)An efficient structure parameters multi-objective optimization of the bi-directional electromagnetic linear actuator was realized.A genetic-particle swarn optimization algorithm was improved and its performance was evaluated.The actuator was optimized with volume restriction based on the hierarchical genetic-particle swarm algorithm(HGP).The effectiveness of the design method and the performance of the prototype were verified experimental.The results show that the contradiction between the global capacity and the convergence speed is overcome effectively by HGP.Through optimizing design,the dynamic response time of prototype is 5.8 ms,and the stroke is±1.5 mm with a good linear force-displacement curve.Moreover,the prototype start-up force is 185 N and holding force is 336 N,which increased by 36%and 87%respectively.(3)An electromagnetic-mechanical-temperature coupling model of the actuator was established.The model is precision and the output result error smaller than 5%.Based on the coupling model,the consumption composition and distribution of actuator were analyzed quantitatively,as well as the temperature rise distribution and variation rules.Besides,current control parameters and current controller were designed under temperature rise restriction.Armature iron loss,shell iron loss and coil copper loss are the main components of power consumption,as well as the main heat source.The limiting working temperature of the permanent magnet is the determining factor of the actuator working limit temperature.(4)A sensorless technology of bi-directional actuator for armature displacement detection was studied.Besides,a sensorless landing control method was proposed for the actuator with holding force.Then the simulation model of control system was established to simulate the control scheme.Finally,the effectiveness of the proposed control method wass proved experimental.The results show that the detection accuracy of armature position is higher when armature is static or at a low speed,the detection accuracy of the trigger point is within 0.05 mm.Compared with the actuator without landing control,the dynamic response time increased by 6.8%,while the first bounce decreased by 85.7%.Besides the second bounce is eliminated.Furthermore,the landing velocity and work noise of actuator decreased by 52.1%and 4dB respectively.(5)A SCR metering pump was designed based on bi-directional electromagnetic linear actuator and reed valve.The flow capacity,spring stiffness and shut-off performance of reed valve were analyzed.The flow characteristic test platform was set up and related tests were carried out.The results show that the measuring range is 0-3900mL/min and the repetitive precision is less than 5%.Compared with the existing direct driving metering pump,the prototype has its remarkable advantages in the range of metering flow,which meets the SCR system requirements.