M Mohamed Ezzeldin

Improved convergence of MRAC design for printing system

This paper deals with the improved design of stable model reference adaptive systems, by introducing a nonlinear adaptation gain. Uniform asymptotic stability of the system is demonstrated for both state and output feedback cases. A simulation example shows the effectiveness of the proposed approach when large parameter variations and disturbances are active. It is also being applied to control a real printing system.

Toward better printing quality for a drop-on-demand ink-jet printer: improving performance by minimizing variations in drop properties

Drop-on-demand (DoD) ink-jet printing is an efficient technology for depositing picoliter drops on various printing surfaces. DoD technology is compatible with various liquids and does not require contacting the printing media. DoD inkjet printing combines several advantages including high speed, quiet operation, and compatibility with a variety of printing surfaces. Moreover, DoD printing can make patterns without any additional lithographic process. Ink-jet printing can reduce the number of processing steps compared to conventional patterning processes, which results in a lower production cost. Therefore, DoD ink-jet technology is applied in many engineering and scientific applications (see Figure 1), such as the formation of the conductive tracks for printed circuit boards, color filters in flat panel displays and plasma displays, polymer light-emitting diode displays, organic transistors, and the construction of DNA microarrays [1]-[5].

Piezo printhead control : jetting any drop at any time

Full flexible use of inkjet printhead units in printing systems requires consistent generation of drops with any given volume and velocity at any moment and place desired. True drop-on-demand is currently hampered by physical phenomena in the printhead. These are residual vibrations and crosstalk resulting from conventional jets. This chapter presents control strategies to overcome these problems. First, with experiment-based control the drop characteristics are measured and the jet pulse that activates the jetting of a drop is optimised. Choosing a proper jet pulse structure, one can deal with single-channel residual vibration, multi-channel crosstalk, and even generalise optimisation over each bitmap to be printed. Secondly, with a model-based control approach, optimised jet pulses can be derived without additional measurement equipment. Considering the inkjet mechanism as an uncertain system and designing a robust pulse allows to deal with differences between model and real system. Both the experiment- and model-based method result in strongly improved drop characteristics, which is experimentally verified and thereby provide very valuable steps towards adaptive printing systems.

Observer-based robust L 2 control for a professional printing system

The robust control problem of a laser printing system, using an ℒ2 observer-based output feedback controller, is analyzed. The nonlinear printing system is approximated by a Takagi-Sugeno (T-S) model. A robust control technique is proposed to cope with the effect of the approximation error between the nonlinear model of the printing system and the approximated T-S model. A sufficient condition is derived to ensure robust stability of an ℒ2 observer-based output feedback controller with guaranteed disturbance attenuation level. A parameterized Lyapunov function is employed in our approach. A transformation formulates the problem in terms of a linear matrix inequality for which efficient optimization solvers are used to test feasibility. Simulation results illustrate the performance and the validity of the proposed approach.

Improving the performance of a printing system using Model Reference Adaptive Control: An LMI approach

A novel Model Reference Adaptive Control (MRAC) scheme is proposed. The formulation involves recasting the error dynamics, which comprise of the tracking error and error of the controller parameters, into a Takagi-Sugeno model. Instead of using a single adaptation gain, multiple adaptation gains are employed. A sufficient condition is derived to ensure the asymptotic stability of the system for both state and output feedback cases. The adaptive control problem is formulated as a minimization of the L2 gain. The optimal adaptation gains are obtained by solving a linear matrix inequality problem. A numerical example compares the proposed approach with the standard MRAC. Moreover, the proposed approach is applied to control a real printing system to improve the printing quality where large parameter variations, owing to different print jobs, and disturbances are presence.

Robust ℒ 2 control for a class of nonlinear systems: A parameter varying Lyapunov function approach

The problem of robustly stabilizing a class of nonlinear systems by using an ℒ2 state feedback based controller is proposed. A class of nonlinear systems is approximated by a Takagi-Sugeno (T-S) model. A robust stabilization technique is proposed to override the effect of approximation error between the original nonlinear system and the approximated T-S model. A sufficient condition is derived to ensure the robust stability of the ℒ2 state feedback based controller with guaranteed disturbance attenuation level. Unlike the approaches using a single quadratic Lyapunov function, a parameter varying quadratic Lyapunov function is employed in our approach. A transformation is presented to formulate the problem in terms of a linear matrix inequality problem for which efficient optimization techniques are available. A simulation example of an inverted pendulum on a cart illustrates the performance and the validity of the proposed approach.

Inverse-based feedforward control for an inkjet printhead

Inkjet is an important technology in document printing and many new industrial applications. As inkjet developments are moving towards higher productivity and quality, it is required to achieve droplets which are small and fired at a high jetting frequency. Inkjet printers are now widely used to form conductive traces for circuits, as well as color filters in LCD and plasma displays. This makes the printing quality an important issue. In this paper, a model-based and data-based inverse feedforward control method is proposed to improve the printing quality of the piezoelectric inkjet printer. The proposed inverse input is applied to the inkjet printhead and the system performance is investigated.

Improving the Performance of an Inkjet Printhead using Model Predictive Control

Abstract Inkjet printing is considered one of the most promising printing technologies that offers several advantages including high speed, quiet operation and compatibility with a variety of substrates. That makes it an important manufacturing technology serving a wide variety of markets. Though the performance criteria imposed by todays applications are quite tight already, the future performance requirements will be even more challenging. However, the attainable performance is limited by two operational issues that are generally encountered, namely residual vibrations and cross-talk. This paper presents an approach based on Model Predictive Control (MPC) with which an input waveform is designed to improve the printing quality of a piezoelectric inkjet printer. The narrow-gap model is employed to predict the response of the ink channel under the application of the piezo input. Simulation and experimental results are presented to investigate the performance of the proposed approach.

Adaptive control strategies for productive toner printers

This chapter discusses design considerations for industrial systems and processes when embedded systems allow to intelligently influence the system in real-time. It is shown that in such embedded systems the capability to adapt themselves to changing environments and/or to different operating conditions has to be exploited. If properly done, almost all performance indicators like accuracy, speed, robustness, insensitivity for disturbances, will improve. The challenge is to first study the process for which the behaviour has to be improved. Based on the characteristics of the process and its disturbances, one wishes to select among the hundreds of tools to achieve its goals. For the professional printer, this design process and its many compromises and choices will be illustrated. Consequently, the professional printer will be analysed for its specific characteristics whose behaviour can be influenced during printing. Based on these characteristics, appropriate control approaches are discussed in more detail to show how control can cope with uncertainty or changing parameters. With extensive and illustrative examples the various methods are compared and it is shown why some control approaches are preferred solutions in the large number of problems that are faced by professional printers.