| Basis weight control actuators include basis weight control valve and dilution profile actuator,which are important special device for basis weight control.In order to meet the basis weight indicator needs,also the improving higher quality requirements of customer,5000 steps for basis weight control and 1000 steps positioning accuracy for dilution profile actuator were objectively needed.It was essentially different from the ordinary electric valve actuator,whether in structure or in control algorithm.Since the design and manufacture techniques hasn’t been mastered by domestic enterprise currently,the actuator largely depends on import and very expensive.Applied technology fundamental research work has been conducted to solve the problems mentioned above.This dissertation mainly concentrates on the positioning control strategy of actuators.I.Design and prototype trial-manufacture of high-precision electric valve actuators.The scheme of the new type actuator was presented,which driving by stepper motor and transmitting by precise planetary gear reducer.And then,the controller based on micro control unit was developed.So,the problem of structure and self control of the actuator were solved.Lastly,the prototype machines of basis weight control valve,rotating and linear type of dilution profile actuator were developed.Firstly,the rated design torque of actuator was worked out,according to the size of valve.Secondly,the stepper motor model and the reduction ratio of the gear box were confirmed.Thirdly,the detailed mechanical structure was presented.Specially,the new scheme of reinforced air-cooling heat dissipation method and fission arrangement was proposed.And then,the controller which based on micro control unit of the actuator was developed,by analyzing the drive and control function demands.This lay the foundation of further study of control strategy for actuators in this dissertation.II.Research on the precision positioning control strategy of drive motor.An experimental device was developed to test the positioning precision of stepper motor which driving the actuator.And then,the precision positioning control strategy of trapezoidal and S-shaped velocity curves was presented.It has solved the problem of losing step and shocking,which commonly existed in the traditional full step and constant frequency control mode.So,the precision positioning of drive system has been greatly improved.The reason for accuracy-loss of stepper motor was found by simulation and experiment,which was due to the high acceleration at the starting and stopping moment.Irregular movement was occurred when the stepper motor couldn’t match with the control pulse.The method of stepper motor subdivision drive mode was beneficial to increase the positioning precision of stepper motor.However,the precision could not meet the required positioning precision.So the acceleration and deceleration control strategy was presented.Then the relationship between each time segment and the least equivalent operating step was presented.Also the math expression of each time intervals for the control pulses was proposed.Lastly,the positioning error of the stepper motor were tested at the at the trapezoidal and S-shaped velocity curves mode,respectively.Experimental result shows that the positioning error has been reduced from5.59%to 0.12%and 0.055%when the motor rotates one full circle.Also the problem of shocking was has been solved,the positioning error was reduced to16.00%and 5.00%when the motor rotates the least equivalent one pulse.This has proved that the method proposed above could greatly improve the precision of stepper motor.III.Study on drive parameters of the actuator.The experimental devices were developed to test the stepper motor driveparameters setting value,respectively,the basis weight control valve and dilution profile actuator.And then,the method of setting the drive parameters by doing experiment procedure was presented.It makes the drive parameters of the actuator to be more reasonable.The minimum drive current value which could meet the positioning precision was obtained by experiment test.Test result shows that the reasonable drive current setting value were 3.14 A and 1.4 A,for the DN 125 mm basis weight control valve,and DN 20 mm rotating type dilution profile actuator respectively.And the suitable state holding current value of the two should be both set at the level of 50%.This method has solved the matching problem,which the actual torque could hardly match with the rated design torque of actuator.Because of they were set at the rated current value of the stepper motor or by practice traditionally.Both of the new drive current setting value of the two was lower than the rated current value of stepper motor.So,less heat productivity were emitted of the stepper motor and the driving chip,compared with the traditional mode.It was helpful to solve the difficulty in cooling of the dilution profile actuator.The reliability of actuator has been improved.And it has provided assurance for precision positioning of stepper motor and safe operation of actuator.And then,the relationship between drive current value and and drive torque of stepper motor were obtained by experimental test,which could meet with the positioning precision.The mathematics correlation of the two was presented.The method of adjusting the drive torque of actuator by setting at different drive current value was proposed.It could be used to make one type of controller matching with different size of basis weight control valves.So the universality of the controller has been improved.IV.Study on backlash measurement and software compensation methods.The backlash measurement experimental devices were developed to measure the backlash of the rotating type and linear type actuator.And then,the measurement and software compensation methods were presented.The transmission system precision of the actuator was improved in this way.Experiment result revealed the the law of backlash value compensation strategy,which could only compensates the average backlash value,but couldn’t compensates fluctuation error.And then,the relationship between software compensation precision and machining accuracy of the actuator transmission parts was obtained.To meet the 5000 steps and 1000 steps precision,for the rotating and linear type actuator,respectively.At least 5-grade machining accuracy of the transmission parts was needed both of the two.Lastly,test result shows that,the return process accuracy has been increased from 407 steps to5000 steps and 293 steps to 3704 steps,for the basis weight control valve and the linear type dilution profile actuator,respectively.The precision has been improved more than 12 times,compared to the traditional method,the backlash was often neglected.Both of the two could meet the requirements of 5000 steps and 1000 steps.This has proved that the methods proposed above could greatly improve the precision of transmission system,under lower hardware precision conditions.To sum up,the technical problems of structure and precision positioning control for the paper basis weight control actuator has been solved.In this dissertation,the method of combining theoretical analysis and experimental test methods was applied.The new type of basis weight control valve,rotating type and linear type dilution profile actuator developed here has been tested.Test result shows that the positioning precision of the actuator were better than 10000steps,1000 steps and 3000 steps.The technical indicators of the actuator could reach or exceeds the equivalent value of foreign competing products.Compared with the high cost of the foreign competing products,the cost of the actuator only accounts for a quarter or one third compared with the same products.The basis weight control valve developed in this dissertation,have found applications in the tissue paper machine with the speed of 800 to 1200 m/min.The basis weight indicators could be controlled within the range of 14.0±0.3 g/m~2,which could meet the precision requirement of basis weight control in production,even could be suitable for to replace import products.It provides theoretical basis and technology reference for the localization of paper basis weight control actuators. |
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