Amol A. Khalate

Optimal experimental design for LPV identification using a local approach

A common approach for dealing with non-linear systems is to describe the system by a model with parameters that vary as a function of the operating point. Consequently, the non-linear system is seen as a combination of local Linear Time-Invariant (LTI) systems, one for each value of the operating point. Such representations are called Linear Parameter-Varying (LPV) models. Due to the importance of this representation for the control of nonlinear systems, numerous algorithms have recently been developed to identify LPV models. However, the optimal design of such identification experiments remains completely unexplored. In this paper, we consider the so-called local approach for the LPV identification. In the local approach, the local linear models, corresponding to a series of fixed operating points, are identified by performing one identification experiment at each of these operating points. The LPV nature of the system is then retrieved by interpolating the value of the parameters at other operating points for example with a polynomial function which is fitted through the parameters identified at the operating points considered. We present an approach to choose optimally the value of the operating-points at which the local identification experiments will be performed. By optimal, we mean that the value of the operating points are optimized in such a way that the LPV model obtained after interpolation has a maximum accuracy.

A Waveform Design Method for a Piezo Inkjet Printhead Based on Robust Feedforward Control

The printing quality delivered by a Drop-on-Demand (DoD) piezo inkjet printhead is limited mainly due to the residual oscillations in the ink channel. The maximal jetting frequency of a DoD inkjet printhead can be increased by quickly damping the residual oscillations and thus bringing an ink channel to rest after jetting an ink drop. In this paper, we propose a robust optimization-based method to design the input actuation waveform for the piezo actuator in order to improve the damping of the residual oscillations in the presence of parametric uncertainties in the ink-channel model. The proposed method obtains a robust actuation pulse by minimizing the tracking error under the parametric uncertainty. Experimental results with a small-droplet DoD inkjet printhead are presented to show the efficacy of the proposed method and the significant improvement in the ink drop consistency.

Optimization-based feedforward control for a Drop-on-Demand inkjet printhead

The printing quality delivered by a Drop-on-Demand (DoD) inkjet printhead is limited due to operational issues such as residual oscillations in the ink channel and the cross-talk between the ink channels. The maximal jetting frequency of a DoD inkjet printhead can be increased by quickly damping the residual oscillations and by bringing in this way the ink channel to rest after jetting the ink drop. This paper proposes an optimization-based method to design the input actuation waveform for the piezo actuator in order to improve the damping of the residual oscillations. The narrow-gap model is used to predict the response of the ink channel under the application of the piezo input. Simulation and experimental results are presented to show the applicability of the proposed method.

Adaptive fuzzy observer and robust controller for a 2-DOF robot arm

Recently, adaptive fuzzy observers have been introduced that are capable of estimating uncertainties along with the states of a nonlinear system represented by an uncertain Takagi-Sugeno (TS) model. In this paper, we use such an adaptive observer to estimate the uncertainties in the state matrices of a two-degrees-of-freedom robot arm model. The TS model of the robot arm is constructed using the sector nonlinearity approach. The estimates are used in updating the model, and the updated model is used to design a controller for the robot arm. We analyze the improvement in the achievable controller performance when using the adaptive observer.

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.

Minimization of cross-talk in a piezo inkjet printhead based on system identification and feedforward control

The printing quality delivered by a drop-on-demand inkjet printhead is severely affected by the residual oscillations in an ink channel and the cross-talk between neighboring ink channels. For a single ink channel, our earlier contribution shows that the actuation pulse can be designed, using a physical model, to effectively damp the residual oscillations. It is not always possible to obtain a good physical model for a single ink channel. A physical model for a multi-input multi-output (MIMO) inkjet printhead is made even more sophisticated by the presence of the cross-talk effect. This paper proposes a system identification-based approach to build a MIMO model for an inkjet printhead. Additionally, the identified MIMO model is used to design new actuation pulses to effectively minimize the residual oscillations and the cross-talk. Using simulation and experimental results, we demonstrate the efficacy of the proposed method.

Drop-on-demand inkjet printhead performance improvement using robust feedforward control

The printing quality delivered by a Drop-on-Demand (DoD) inkjet printhead is mainly limited due to the residual oscillations in the ink channel. The maximal jetting frequency of a DoD inkjet printhead can be increased by quickly damping the residual oscillations and by bringing in this way the ink-channel to rest after jetting the ink drop. The inkjet channel model obtained is generally subjected to parametric uncertainty. This paper proposes a robust optimization-based method to design the input actuation waveform for the piezo actuator in order to improve the damping of the residual oscillations in the presence of parametric uncertainties in the ink-channel model. Simulation results are presented to show the efficacy of the proposed method.

Robust Feedforward control for a Drop-on-Demand Inkjet Printhead

Abstract The printing quality delivered by a Drop-on-Demand (DoD) inkjet printhead is mainly limited due to the residual oscillations in the ink channel. The maximal jetting frequency of a DoD inkjet printhead can be increased by quickly damping the residual oscillations and by bringing in this way the ink-channel to rest after jetting the ink drop. The inkjet channel model obtained is generally subjected to parametric uncertainty. This paper proposes a robust optimization-based method to design the input actuation waveform for the piezo actuator in order to improve the damping of the residual oscillations in the presence of parametric uncertainties in the ink-channel model. Experimental results are presented to show the efficacy of the proposed method.

Robust Fault Diagnosis by Optimal Input Design for Self-sensing Systems

Abstract This paper presents a methodology for model based robust fault diagnosis and a methodology for input design to obtain optimal diagnosis of faults. The proposed algorithm is suitable for real time implementation. Issues of robustness are addressed for the input design and fault diagnosis methodologies. The proposed technique allows robust fault diagnosis under suitable conditions on the system uncertainty. The designed input and fault diagnosis techniques are illustrated by numerical simulation.