Modeling Advanced Temperature Measurement And Control Algorithms In Thermoforming

Modeling, Advanced Temperature Measurement, and Control Algorithms in Thermoforming

"Thermoforming is a plastic manufacturing process consisting of three major phases: heating, forming, and cooling. During the heating phase, the plastic sheet has to be heated to a precise temperature set-point (profile) at which it is flexible enough to be molded. Often, because of the complexity of the final product's shape, uneven temperature set-points are required across the plastic sheet. Therefore, it is crucial to systematically control the heaters' temperatures so that the exact temperature profile is achieved across and through the depth of the plastic sheet. In the first part of this thesis, advanced temperature measurement algorithms are developed, namely model-based virtual sensors (MBVS) and core-temperature observers. The concept of MBVSs allows for extra surface-temperature measurement points in addition to the existing infrared sensors. This leads to improved observability of the sheet's temperature and increased accuracy in achieving uneven temperature profiles, thus eliminating the use of extra infrared sensors and significantly reducing the cost of the control system. Additionally, core-temperature observers are developed in order to precisely monitor the core-temperature of the plastic sheet, as it is crucial for the center-plane of the sheet to be within the forming temperature window at the end of the cycle. In the second part of this thesis, the application of the Watanabe-modified Smith predictor control technique (an internal-model control technique) is studied for the thermoforming heating phase in order to reduce the heating-cycle time of the process. The third part of the thesis addresses the temperature control of multilayered plastic sheets during the heating phase. Thermoforming of multilayered sheets has proven to be quite challenging since different plastic materials contain their own distinctive rheological properties and forming temperatures. In this thesis, a dynamical temperature evolution model of multilayered plastic sheets is presented, followed by a proposed discrete-time model predictive control (DTMPC) algorithm to solve, for the first time, the non-uniform temperature tracking problem of all the layers, while incorporating the nonlinear dynamics of the actuators in the design. Finally, the last part of this thesis covers the important problem of parameter variations in thermoforming. During the thermoforming heating phase, temperature evolution models of plastic sheets consist of nonlinear temperature-dependent parameters, which have yet to be accounted for when solving the temperature tracking problem. These equations are subsequently modeled in the hybrid systems framework based on the segmentation of the parameter varying elements. Employing a proposed constrained hybrid optimal control (HOC) algorithm based on the Hybrid Minimum Principle (HMP), which contains the nonlinear actuator constraints of the heating phase, the temperature tracking problem is solved for this parameter varying system, for the first time. The HOC algorithm is also designed to minimize the energy consumption of the heaters during the heating phase. Moreover, a closed-loop hybrid controller (CLHC) is developed, based on the proposed HOC, to provide robustness against perturbations. Successful application of the proposed HOC algorithm also serves as a proof of concept to show that HMP based HOCs can be implemented on large-scaled nonlinear industrial processes containing parameter variations and nonlinear actuator constraints." --

Proceedings of the ASME Materials Division

Applied Plastics Engineering Handbook

Applied Plastics Engineering Handbook: Processing, Sustainability, Materials, and Applications, Third Edition presents the fundamentals of plastics engineering, helping bring readers up-to-speed on new plastics, materials, processing and technology. This revised and expanded edition includes the latest developments in plastics, including areas such as biodegradable and biobased plastics, plastic waste, smart polymers, and 3D printing. Sections cover traditional plastics, elastomeric materials, bio-based materials, additives, colorants, fillers and plastics processing, including various key technologies, plastic recycling and waste. The final part of the book examines design and applications, with substantial updates made to reflect advancements in technology, regulations, and commercialization. Throughout the handbook, the focus is on engineering aspects of producing and using plastics. Properties of plastics are explained, along with techniques for testing, measuring, enhancing, and analyzing them. Practical introductions to both core topics and new developments make this work equally valuable for newly qualified plastics engineers seeking the practical rules-of-thumb they don't teach you in school and experienced practitioners evaluating new technologies or getting up-to-speed in a new field. - Offers an ideal reference for new engineers, experienced practitioners and researchers entering a new field or evaluating a new technology - Provides an authoritative source of practical advice, presenting guidance that will lead to cost savings and process improvements - Includes the latest technology, covering 3D printing, smart polymers and thorough coverage of biobased and biodegradable plastics