Robust constrained tension control for high-precision roll-to-roll processes.

Tension control is critical for maintaining good product quality in most roll-to-roll (R2R) production systems. Previous work has primarily focused on improving the disturbance rejection performance of tension controllers. Here, a robust linear parameter-varying model predictive control (LPV-MPC) scheme is designed to enhance the tension tracking performance of a pilot R2R system for deposition of materials used in flexible thin film applications. The performance of a tension controller may degrade due to disturbances associated with model uncertainties and the slowly-changing dynamics in R2R systems. We introduce a method that separately treats these two sources of disturbance. The controller utilizes an incremental model to eliminate the errors caused by the mismatch between the nominal model and the actual system. A tube-based MPC formulation combined with scheduled parameters adequately updates models and corrects for the time-varying dynamics. Constraints on the rated motor torque are incorporated in the MPC to maintain the controller reliability and avoid machine failures. We illustrate the operation of our control algorithm through simulation of an actual R2R system. The controller outperforms the benchmarks in terms of fast transient response and offset-free tension tracking. It also demonstrates immunity from variations due to parametric uncertainties.

Synthesis and properties of organoboron functionalized nanocellulose for crosslinking low polymer fracturing fluid system.

The traditional organoboron crosslinker used in the guar gum fracturing fluid has the disadvantages of a larger amount of guar gum and crosslinker and higher susceptibility to pH. Nanoparticles have special properties such as large specific surface area and many active groups, so the organic boron crosslinker and nanoparticles are combined to obtain nano crosslinkers. In this paper, rod-shaped nano-cellulose particles were prepared by acid hydrolysis, and a nanocellulose crosslinker was synthesized by combining with organic boron and KH550. Nanocellulose cross-linker has good temperature and salt resistance. It can meet the requirements of cross-linking guar gum fracturing fluid with a mass fraction of 0.3 wt% under neutral conditions. The residual viscosity is higher than 50 mPa s under shear at 170 s-1 and 110 °C for 60 minutes when the pH increases from 7 to 13, and NBC crosslinking can withstand a temperature of 160 °C under pH = 10. The crosslinking mechanism of the widely accepted nano-crosslinker is that the organoboron on the surface of the nanoparticle combines with the homeopathic ortho hydroxyl of the guar gum molecule to form a hydrogen bond and thereby form a complex network structure. This research shows that the hydrogen bonding between the nano-cellulose crosslinker and HPG molecules, and the resulting gel has a more complex network structure because of the formation of inter-chain cross-links.

Synthesis and properties of a high-performance environment-friendly micro-nano filtration reducer.

In this research study, we modified hydroxyethyl cellulose to obtain hydrophobically associating hydroxyethyl cellulose, and grafted it onto the surface of nano-calcium carbonate to obtain a graft copolymer. The intramolecular or intermolecular associations between the macromolecular chains of the graft copolymers form different forms of supramolecular network structures, and they interact with nanoparticles to form stable structures to enhance their related properties. The structure of the obtained graft copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR) and laser particle size analysis. Thermogravimetric analysis (TGA) showed the thermal stability of the graft copolymer, and the results showed that the graft copolymer obtained thermally decomposed after 370.86 °C, indicating that it has good thermal stability. Scanning electron microscopy (SEM) revealed the mechanism of the graft copolymers in drilling fluids. The fluid loss control performance and rheology of the filtration reducer were evaluated before and after hot rolling at 180 °C for 16 hours. The results showed that the graft copolymer has excellent fluid loss reduction performance, and it has good fluid loss reduction performance in fresh water, brine and saturated brine. The API fluid loss was only 6.4 mL after hot rolling at 180 °C for 16 h in the brine base slurry. Moreover, the obtained graft copolymer is easily biodegradable, has EC50 ≥ 30 000 and good environmental performance, and can be used in high temperature and high salt reservoir with high environmental protection requirements.