Film thickness controller

• US 5,359,532 A
• Filed: 11/05/1992
• Issued: 10/25/1994
• Est. Priority Date: 11/12/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jukogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jukogyo Kabushiki Kaisha
• Inventors: Akasaka, Noriyuki
• Primary Examiner(s): Ruggiero, Joseph
• Application Number:
  US07/972,132
• Time in Patent Office: 719 Days
• Field of Search: 364/473, 364/476, 364/177, 364/176, 364/183, 425/141, 425/142, 425/143, 425/144, 425/145, 425/135, 425/140, 264/40.1
• US Class Current: 700/197
• CPC Class Codes: B29C 2948/92152 Thickness
• CPC Class Codes: B29C 2948/92428 Calibration, after-treatment, or cooling zone
• CPC Class Codes: B29C 2948/926 Flow or feed rate
• CPC Class Codes: B29C 2948/92647 Thickness
• CPC Class Codes: B29C 2948/92704 Temperature
• CPC Class Codes: B29C 2948/92923 Calibration, after-treatment or cooling zone
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/914 cooling drums
• CPC Class Codes: B29C 48/92 Measuring, controlling or regulating
• CPC Class Codes: B29C 55/00 Shaping by stretching, e.g. drawing through a die; Apparatus therefor B29C61/08 takes precedence
• CPC Class Codes: B29K 2995/0053 bi-axially
• CPC Class Codes: B29L 2007/008 Wide strips, e.g. films, webs
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05D 5/03 characterised by the use of electric means

Abstract

A film thickness controller capable of obtaining the rapidity of predetermined thickness control always even if the operation conditions are changed is disclosed.

The film thickness controller includes a die having a mechanism for adjusting and operating a discharge amount along the width direction of film, a thickness gauge for detecting variation of thickness of the film moved with a lag time from a position of the die to a position of the thickness gauge, and adapters 200, 201, 202 and 203 added to an operational calculator 103, a state prediction device 106, a state shifter 105 and an operation amount commander 108 constituting the film thickness controller, respectively, to thereby automatically modify a matrix of a control operation equation to be coincident with the operation conditions with respect to variation of the lag time due to movement of the film and automatically modify a gain matrix of the operational calculator, a gain matrix of a regulator and a matrix in the control operation equation to be coincident with the operation condition with respect to variation of film thickness sensitivity to heater input variation by change of the operation conditions.

Claims

1. A film thickness controller comprising:

a die having a mechanism for adjusting and operating a discharge amount of molten resin along a width direction of a film,

a thickness gauge for detecting thickness of the film at a measurement position, the thickness gauge being movable along the width direction of the film, molten resin discharged from the die having a lag time L1 before reaching the measurement position,

a subtracter for producing a thickness difference between a detected value of film thickness measured by said thickness gauge at the measurement position and a set value of thickness,

an integrator for time-integrating the thickness difference produced by said subtracter,

a memory for storing a time sequence of a past operation amounts during a time L, time L being governed by the equation

space="preserve" listing-type="equation">L=L1+L2

where L2 represents time required for said thickness gauge to reach an end of the film from the measurement position,

an operational calculator using the time sequence of said past operation amounts stored in said memory for producing an estimated value of state variable before a time when said thickness gauge reaches the end of the film by said lag time L,

an operation calculator adapted for modifying a matrix used in an operation equation in said operational calculator to be coincident with operation conditions,

a state shifter supplied with an output of said integrator and an output of said operational calculator for producing state estimated value at a time that state is shifted by an average lag time /L which is an average value of said lag time L at both ends of the film,

a state shifter adapter for modifying a matrix used in an operation equation in said state shifter to be coincident with the operation conditions,

a state prediction device for producing a state variation amount due to input from time greater than said average lag time /L to a time when said thickness gauge reaches an end of the film on the basis of time sequence of the past operation amounts stored in said memory,

a state prediction device adapter for modifying a matrix used in an operation equation in said state prediction device to be coincident with the operation conditions,

an adder for adding an output of said state shifter and an output of said state prediction device and producing a state estimated value at a time when said thickness gauge reaches the end of the film,

an operation amount commander for multiplying the state estimated value produced by said adder by state feedback gain for producing a command value of the operation amount of the operation end, and

an operation amount commander adapter for modifying a matrix used in an operation equation in said operation amount commander to be coincident with the operation conditions.

2. The film thickness controller of claim 1 wherein the mechanism for adjusting and controlling the amount of molten resin includes at least two heating elements, thickness measurements of the film being taken at positions along the width of the film corresponding to positions of the heating elements.