| A fatigue testing machine using precision motion control is widely applicated in scientific research,energy transportation,mechanical electronics and other fields.An automobile is a typical heavy industry product,and taking an automobile is an important way for people to travel.A shock absorber is an important part of an automobile and its performance is related to the overall performance of the car.It is of great significance to use fatigue testing machines to study the fatigue characteristics of shock absorbers in automobile production.The existing fatigue testing machine for automobile shock absorber testing is mainly divided into two categories,mechanical fatigue testing machine and electro-hydraulic servo fatigue testing machine.There is no application of electric cylinder fatigue testing machine for automobile shock absorber fatigue testing.The test frequency of a mechanical fatigue testing machine is low,and the accuracy is not high,while the fatigue test of a electro-hydraulic servo fatigue testing machine in a longer period of time will consume a lot of energy.The electric cylinder fatigue testing machine has the advantages of small space occupation,simple structure,high energy conversion efficiency,low energy consumption and low noise.Comparing to dual-cylinder fatigue testing machine,the advantages of single-cylinder fatigue testing machine is more prominent.Therefore,the study of single-cylinder automobile shock absorber fatigue testing machine is of great significance.The electric cylinder is the core component of electric cylinder fatiguetesting machine.The servo motor control of intermediate and low-level electric cylinder fatigue testing machines for conventional motion will have a greater positioning error and phase error,and these electric cylinders can not achieve high frequency,high speed and heavy load motion control.Therefore,it is necessary to design a single-cylinder fatigue test position control system.The system can control the shock absorber through a single electric cylinder to realize the same double-acting motion function as the double electric cylinder,and the shock absorber is needed to be driven to perform high-precision and low-distortion motion under high-frequency,high-speed and large load.It is difficult to design such a high-end single-cylinder fatigue test system,which is also the main issue of this paper.To solve the problem,a position control system of double-acting motion fatigue testing machine based on single-cylinder precision motion control is designed in this paper.It is as follows:In order to realize double-acting motion position control of a single electric cylinder,this paper has carried on the plan design to the control system,and demonstrated the feasibility of the system.In this paper,two open-loop control system solutions and a closed-loop control system solution are proposed for the technical specifications of the control system.They are single-cylinder double-acting motion control system based on standard sine table,single-cylinder double-acting motion control system based on superposed harmonic table and single-cylinder double-acting motion closed-loop control system based on superposed harmonic table.Finally,a single-pole double-acting motion closed-loop control system based on superposition harmonic table is selected as the control system in this paper,and the FPGA with low delay and high parallelism is selected as the system processor.In order to solve the problem of slow response and low tracking performance of the control system under high-frequency,high-speed and large-load,a mathematical model of the control system and an adaptivefuzzy PID controller are designed for the above closed-loop control system.Through the simulation of the control system,the effects of the two control algorithms,classical PID and adaptive fuzzy PID,on response speed and tracking effect are compared,and adaptive fuzzy PID control algorithm with fast response and good tracking performance is selected as the control algorithm in this paper.Based on the proposed control scheme and control algorithm,this paper introduces the system hardware configuration and system software design.The software part designed includes the sub-modules of the control system.They are the data generation module,Ethernet communication module,memory module,pulse generation module,protection module,pulse selector module and error compensation module.In particular,the error analysis is carried out in the error compensation module,and the error compensation method is proposed.The design of the ADC compensation module and the adaptive fuzzy PID algorithm are carried out as well.Finally,the software modules are tested,including time-harmonic data reconciliation and harmonic test,Ethernet transmission and storage test,ADC module test,pulse transmission experiment and the repetitive experiment.Experiments show that each sub-module can achieve the correct function. |
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