单片机外文文献1.docVIP

单片机外文文献1 the uniform tension at a preferred value of polyester pet films in processing or rewinding is important to product quality which can be achieved by tension control furthermore the uniformtransport speed is helpful in creating uniform film tension in this article a simplified version of pet film processing systems consisting of an unwinding roll a sensor roller and a rewinding roll is considered the unwinding roll and rewinding roll are driven by a torque-controlled motor and speed-controlled motor respectively a control signal to the torque-controlled motor generated by a conventional sliding-mode controller or a fuzzy sliding-mode controller regulates the film tension moreover the speed-controlled motor adjusts the transport speed at the winding section to improve the speed fluctuation an external proportional-plus-integral plus-derivative pid controller for the speed-controlled motor was implemented the experimental results demonstrate that fuzzy sliding-mode control gives the tension response with smaller variation than the conventional sliding-mode control does and the external pid control for speed diminishes fluctuations in speed thus leading to more uniform tension while maintaining it at the preferred valuekeywordsfuzzy sliding-mode control polyester film tension controlintroductiona thin polymer film is generally conveyed to a working zone for processing and wound for storage or final shipment on a rewinding roll by means of roll-to-roll transport mechanisms in the roll-to-roll mechanism the longitudinal behavior including tension and transport speed is important to product quality and productivity for instance when coating optical films uniform tension can avoid defects such as crossweb lines bad pasting and shrinkage even breakage in the rewinding process the film may suffer from changes in shape and from breakage or crushing of the outer layers on the inner layers when tension is too high and sagging wrinkling or railing when the tension is too low because tension and transport speed are linked a severely fluctuating speed may deteriorate the tension variation as well as causing defects such as ribbing lines waves and unevenness in coating thickness thus the uniform tension and uniform transport speed at preferred values will result in higher-quality products and greater throughput young and reid1 modeled the longitudinal and lateral behaviors of webs and designed a pid tension controllerbased on the linearized model ludwicki and unnikrishnan developed a controller based on root locus methods combined with simulations of the time response to meet the dancer position and acceleration requirements for the unwind section in a film finishing application choietaldescribed the tension behavior of a moving tape by means of the one-dimensional wave equation and applied the sliding-mode control algorithm to achieve desired tension sakamoto and fujino expressed the web in terms of spring and dashpot elements and included a dancer roll in modeling the web tension system simulations were performed on the model with a proportionalplus-integral pi controller and focus on paper as a web mathur and messner controlled the torques to the unwinding and rewinding reels in a high-speed low-tension tape transport system the multi-input and multi-output system identification sequential loop closing technique adaptive ripple cancellation and fault compensation were incorporated into the control system design luo and wen proposed a multiple-page mapping artificial neural network with a back-propagation training algorithm which could decouple the speed and tension control loops allowing both loops to operate quasi-independently in order to handle the variation of the rewinding rolls diameter knittel et alpresented a multivariable h1 robust control of tension and velocity with two degrees of freedom 2dof and gain scheduling to web winding systems the 2dof significantly improved disturbance rejection while reducing the coupling between tension and velocity lin8 proposed a pi-type observer to estimate web tension precisely regardless of the effects of friction and inertia and designed an observer-based tension feedback controller against the variation of system parametersin our simplified pet film processing system we focus on the uniform control of pet film tension at a targeted level in combination with uniform transport speed at the rewinding section the tension behavior modeling is based on some assumptions and exhibits nonlinear characteristics both the conventional sliding-mode controller and the fuzzy sliding-mode controller are adopted to control tension because they can handle nonlinear systems and are robust even in the face of modeling uncertainties and fluctuations in speed to reduce the speed fluctuation an external pid controller for the speed-controlled motor was also implemented the performances of our controllers are evaluated based on the mean and standard deviations of their responses to tension and speed system modeling a simplified version of pet film processing systems shown in figure 1 is considered in this study and consists of an unwinding roll a rewinding roll a sensor roller and a pair of idle rollers the film is unwound from the unwinding roll and moved through the idle rollers which guide the film around the sensor roller at a fixed angle finally the film is wound onto the rewinding roll the unwinding roll and rewinding roll are driven by two ac servo motors in torque-controlled mode and speed-controlled modefig 1 configuration of the experimental setuprespectively for simplicity in modeling we assumed the following that the film is perfectly elastic that there is no slippage phenomenon between the roller and the filmthat both the wound-out tension and coulomb friction of the unwinding roll are zero and that the sensor roller and idle rollers do not affect tension according to the mass conservation law for a control volume and very small strain with the film the dynamic of tension is given by1 1where is the tension of the films is the tangential velocity of the rewinding roll l is the film length of a span e is youngs modulus of the film a is the cross section of the film is the radius of the unwinding roll is the angular velocity of the unwinding roll the radii of the unwinding roll and rewinding roll vary with time and their change rates are given by5 2 3where and are the radius and angular velocity of the rewinding roll respectively and this the thickness of the film because the speed-controlled motor drives the rewinding roll the tangential velocity of the rewinding roll can be written as8 4where kr and ur denote the speed constant and input voltage of the motor respectively the unwinding roll is driven by the torque-controlled motor hence the torque equilibrium at the unwinding roll gives the equation5 5where ju t is the total moment of inertia of the unwinding roll and motor bu is the viscous friction coefficient 6where is the torque constant of the motor is the input voltage to the motor is the total moment of inertia of the motor and unwinding roll without the filmwrapped on is the film density is the film width and is the radius of the unwinding roll without films therefore eqs 1 4 and 6 describe the dynamic behavior of film tension and eq 4 governs the transport speed of films at the rewinding section fuzzy sliding-mode control consider a nonlinear system with a single input and single output of the form 7 8where u is the input and y is the output we consecutively differentiate the output y in an increasing order until the minimum order r in which at least one coefficient of u appearing in the expression y r is not zero the value of r is defined as the relative degree of the system which is mathematically expressed by the lie derivatives as910 9 10 11based on the relative degree a sliding function s is defined as 12 12 where is the desired output and the coefficients are real values such that all the roots of the polynomial are in the left half-plane13 the sliding surface is defined by s 0 when the output remains on the sliding surface for it implies that taking the time derivative of s gives 13where g is a switching gain and is a sign function the trajectory of the output is always forced to move toward the sliding surface until it reaches it moves along it this can be shown by lyapunovs second stability theorem with the lyapunov functions 和consequentlythe control law becomes 14in conventional sliding-mode control smc a fixed switching gain g is chosen by the designer often suffering from the chattering problem to alleviate the drawback fig 2 membership function for s and we have the varying switching gain tuned by the fuzzy logic theorem based on the deviation from the sliding surface and its change in the fuzzy sliding-mode control fsmc 1415 the concept originates from the fact that when the output deviates from the sliding surface s and tends to move toward or away from the sliding surface in different degrees the force driving the output toward the sliding surface should have a different quantity the magnitude of g affects the driving force and the fuzzy logic theorem can determine the value of g on the basis of the statesof s andin general the fuzzy system is comprised of the fuzzifier fuzzy knowledge base fuzzy inference engine and defuzzifier in the defuzzifier we choose two input fuzzy variables s and and one output fuzzy variable g for s and s the membership functions are defined on the normalized domain -5 5 as shown in figure 2 where ln mn sn zo sp mp and lp represent large negative mediumnegative small negative zero small positive medium positive and large positive respectively for g the membership functions shown in figure 3 are defined on the normalized domain 0 5 because g is a strictly positive constant where zo sp mp and lp stand for zero small positive medium positive and large positive in addition a scaling factor is used to adjust the domain of the membership function as displayed in table 1 the rule base is built on the characteristics of the response of s for example if thefig 3 membership function for output trajectory falls far away from the sliding surface ln or lp for s and has a pronounced tendency to moveaway from the sliding surface ln or lp for a largeswitching gain lp for g that pulls the output towardthe sliding surface is required finally the min composition and center of gravity are adopted for decisionmaking and defuzzification respectivelysimulation and experimental resultsan experimental setup as schematically shown in figure 1 was built two of s-shaped load cells are located at both sides of the sensor roller around which the film wrapped at an angle of 120 thus the total force measured by the load cells minus the weight of the roller is films tension the values of system parameters are listed in table 2in practice the tension response usually fluctuates this paper deals with maintaining a target level of tension with less fluctuation furthermore maintaining the uniform transport speed at the rewinding section can enhance tension control performance the voltage signal to the torque-controlled motor generated by conventional sliding-mode control or fuzzy sliding-mode control adjusts the film tension the speed-controlled motor regulates its angular velocity based on the target transport speed and radius of the rewinding roll to improve the speed variation an external pid feedback control system to the speed-controlled motor was also implemented as shown in figure 4 where is the desired angular velocity and kp ki and kd are gains of the pid controller the target levels 30 n of tension and transport speedare maintained conventional sliding-mode control and fuzzy sliding-mode control for tension regulation in tandem with the speed-controlled motor alone or with an external pid controller are implemented and their performances are compared we consecutively differentiate eq 1 with respect to time t and find that the input ut appears in the second derivate of t in the first instance thus the relative degree is two and the sliding surface for tension control is and where is the target tension differentiating whereyields the following sliding-mode control law 15 in conventional sliding-mode control there are two coefficients and of the sliding surface and the switching gain g to be chosen in fuzzy sliding-mode control however the gain g is self tuned by the fuzzy logic theorem based on s and the scaling factors and and and fg for membership functions s and are chosen by the designer three gains kp ki and kd of the external pid controller to the speed-controlled motor also need to be selected these choices can be justified by simulation results as a consequence the choice of gives good simulation performance in tension and speed responses the simulation fig 4 an external pid control for the speed-controlled motorresults when implementing the fuzzy sliding-mode control in tandem with an external pid controller for the speed controlled motor are shown in figure 5in the experiment the tension and speed responses usually fluctuate thus their levels and uniformity are evaluated by the mean and standard deviation of tension and speed data angular velocities of the unwinding and rewinding rolls are obtained from encodings of ac motors the transport speed at the rewinding section is the productof the angular velocity and radius of the rewinding roll where the radius is estimated by integrating eq 2 the target speed divided by the radius gives the target angularvelocity of the winding roll which can be converted by eq 4 into the required input voltage to the speed controlled motor by way of demonstration figures 6 and 7 display the tension and speed responses when implementing conventional sliding-mode control and fuzzy sliding mode control in cooperation with pid control in table 3fig 5 simulation results in terms of a tension and b transport speed we summarize the mean and standard deviations denoted by m and r respectivelyin responses to tension and speed for our implementation of the controllers no matter the type of tension and speed control used the mean tension and speed are maintained at levels near to the target values when applied to either method of speed regulation fuzzy sliding-mode control can significantly reduce the standard deviation of tension in comparison with conventional sliding-mode control the speed controlled motor with an external pid controller can reduce the standard deviation of speed and also helps toreduce the standard deviation of tensi