Paper sheet control using steerable nips

Dynamics of Underactuated Multibody Systems

2013

Nearly all real world engineering systems comprise some type of nonlinearity. Therefore, the term nonlinear systems applies to a wide range of very different systems originating from seemingly unlike fields, such as engineering, biology, physics, and chemistry. Nonlinear systems can exhibit many different complex phenomena, such as multiple equilibria, bifurcation or limit cycles. This richness in phenomena makes classification very difficult. The term non indicates the interesting fact that these systems are not clearly characterized by the possession of certain common properties, rather by the lack of properties which are characterizing a linear system. A linear system is characterized by the properties of superposition and homogeneity; the lack of either one of these properties indicates a nonlinear system.Nonlinearity of systems can have many sources. Following Slotine and Li [66], nonlinearities can be distinguished in natural and artificial nonlinearities. These can be further classified into continuous and discontinuous nonlinearities. Natural nonlinearities are inevitably present in the physical hardware and motion of a system. For example, the equation of motion of the overall dynamics of a multibody system is, generally speaking, inherently nonlinear and represents a continuous nonlinear system. In addition, nonlinearity can also be introduced by nonlinear force elements, such as nonlinear springs and dampers. While continuous nonlinearities can be locally approximated by a linear system, i.e. Jacobian linearization of the equation of motion around a stationary working point or a nominal trajectory; this is not possible for systems with discontinuities. Classical sources of discontinuous nonlinearities are, e.g., normal contact between two bodies or friction between surfaces featuring stick-slip phenomena. Artificial nonlinearities can be introduced by the control law and are mostly implemented in the control software. Applying a nonlinear feedback control law to a system without natural nonlinearities results in an overall nonlinear system. For example, adaptive control laws might result in continuous artificial nonlinearities, while bang-bang control and sliding mode control introduce discontinuous artificial nonlinearities. Since in many multibody systems the natural continuous nonlinearities are dominant they are the focus of this treatise.

Section: Control Of a Nonlinear Nonholonomic Mechatronic Systemmentioning

confidence: 99%

Feedback Linearization and Model Inversion of Nonlinear Systems

Dynamics of Underactuated Multibody Systems

2013

“…As mentioned in Refs. [7,8], this mechanism resembles that of a two-wheel robot [12]: however, not only does the two-wheel robot have one less degree of freedom than the steerabie nips system but also the control law proposed by Ref. [ 12] fails to account for singularities that arise when the steering angle of the wheels approaches zero.…”

Section: Introductionmentioning

confidence: 99%

A Robust Approach to Dynamic Feedback Linearization for a Steerable Nips Mechanism

Ergueta

Journal of Dynamic Systems, Measurement, and Control

Horowitz

2011

This paper presents two different control strategies for paper position control in printing devices. The first strategy is based on standard feedback linearization plus dynamic extension (dynamic feedback linearization). Even though this controller is very simple to design, we show that it is not able to handle actuator multiplicative uncertainties, and therefore, it fails when it is implemented on the experimental setup. The .second strategy we present uses similar concepts, but it is more robust since feedback linearization is used only to linearize the kinematics of the system and internal loops are used to locally control the actuator's positions and velocities. In this paper, not only do we formally prove the robustness of the second control strategy but we al.w show its successful implementation.

“…Each roller is driven by a servo motor attached to a rotating table, which is in turn steered by another servo motor through a coupling. This mechanism has been built and is described in Sanchez et al [2004]. As we can see in Fig.…”

Section: Steerable Nips Mechanismmentioning

confidence: 99%

“…These constraints come from non slip conditions on the rollers, and local velocities (of the paper) being zero in the direction perpendicular to the rotation of the rollers. Additional details on these constraints can be found in Sanchez et al [2004]. The kinematic model of the system is derived so that these four nonholonomic constraints are satisfied at all times.…”

Section: Steerable Nips Mechanismmentioning

confidence: 99%

Extended Luenberger Observer for a MIMO Nonlinear Nonholonomic System

Ergueta

IFAC Proceedings Volumes

Horowitz

et al. 2008

State of the art high speed color printers require sheets being accurately positioned as they arrive to the image transfer station (ITS). This goal has been achieved by constructing a steerable nips mechanism, which is located upstream from the ITS. This mechanism consists of two rollers which not only rotate to advance the paper along the track, but also steer the paper in the yaw direction. A recently developed nonlinear control strategy for the position of the sheet is briefly reviewed. The core of this paper focuses on the addition of a nonlinear observer used to estimate the longitudinal, lateral, and angular positions of a sheet, by detecting its motion along two of its perpendicular sides. The success of the approach presented is corroborated through simulations, in which the estimates from the extended Luenberger observer designed are used on a nonlinear feedback control strategy.