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FDM 3D printing is an additive manufacturing technology that is widely used, mainly for rapid prototyping. It is also one of the cheapest and most accessible AM technologies for consumers. FDM printers, and especially cheaper alternatives, can have problems with creating high quality prints. Reasons include poor design, inaccurate construction, cheap components, and improper tuning. Input shaping is a control technique that may help mitigate defects caused by poor mechanical design or construction. The “ringing” defect may be eliminated by applying this solution. To perform an evaluation in sub-optimal mechanical conditions a 3D printer was constructed with a cantilever design mainly using plastic prints for mechanically important parts. Printing tests were done with and without input shaping. The results that were produced showed a direct effect of input shaping in 3d printers., FDM 3D-printing är en additiv tillverkningsteknik som är mycket använd, främst för snabb prototypering. Det är också en av de billigaste och mest tillgängliga AM-teknikerna för konsumenter. FDM skrivare, och särskilt billigare alternativ, kan ha problem med att skapa högkvalitativa utskrifter. Orsaker inkluderar dålig design, konstruktionfel, billiga komponenter och felaktig justering. Input shaping är en kontrollteknik som kan hjälpa till att mildra defekter som orsakas av dålig mekanisk design eller konstruktion. "Ringning" defekten kan elimineras genom att tillämpa denna lösning. För att utföra en utvärdering i dåliga mekaniska förhållanden konstruerades en 3D-skrivare med en fribärande design som använder plastutskrifter för mekaniskt viktiga delar. Utskriftstester gjordes med och utan input shaping. Resultaten som framställdes visade på en uppenbar förbättring av print kvalité som en direkt effekt av input shaping.

FDM 3D printing is an additive manufacturing technology that is widely used, mainly for rapid prototyping. It is also one of the cheapest and most accessible AM technologies for consumers. FDM printers, and especially cheaper alternatives, can have problems with creating high quality prints. Reasons include poor design, inaccurate construction, cheap components, and improper tuning. Input shaping is a control technique that may help mitigate defects caused by poor mechanical design or construction. The “ringing” defect may be eliminated by applying this solution. To perform an evaluation in sub-optimal mechanical conditions a 3D printer was constructed with a cantilever design mainly using plastic prints for mechanically important parts. Printing tests were done with and without input shaping. The results that were produced showed a direct effect of input shaping in 3d printers., FDM 3D-printing är en additiv tillverkningsteknik som är mycket använd, främst för snabb prototypering. Det är också en av de billigaste och mest tillgängliga AM-teknikerna för konsumenter. FDM skrivare, och särskilt billigare alternativ, kan ha problem med att skapa högkvalitativa utskrifter. Orsaker inkluderar dålig design, konstruktionfel, billiga komponenter och felaktig justering. Input shaping är en kontrollteknik som kan hjälpa till att mildra defekter som orsakas av dålig mekanisk design eller konstruktion. "Ringning" defekten kan elimineras genom att tillämpa denna lösning. För att utföra en utvärdering i dåliga mekaniska förhållanden konstruerades en 3D-skrivare med en fribärande design som använder plastutskrifter för mekaniskt viktiga delar. Utskriftstester gjordes med och utan input shaping. Resultaten som framställdes visade på en uppenbar förbättring av print kvalité som en direkt effekt av input shaping.

VIBRATION AVOIDANCE, a technique to proactively remove unwanted or excessive vibrations in multi-joint industrial robots, has shown to be desired in various applications. A trade-off between vibration avoidance performance and path deviation has been thekey criteria for assessing the effectiveness and quality of an approach. The purpose of this thesis is to compare two proposed state-of-the-art vibration avoiding approaches: input shaping and extended flexible joint model combined with specialized compensation control and explore the fusion of them. Both approaches are first investigated and evaluated in simulation. A comparison is then conducted in the four presented baseline movements on a real robot. Among the two approaches, input shaping is less comprehensive but enables rapid identification, making it suitable for simple repetitive tasks. It is also found that joint-wise path generation used in input shaping causes a loss of path fidelity, but this problem is alleviated when using an extended flexible joint model combined with specialized compensation control. The latter approach preserves synchronicity across all joints and assures multi-input multi-output (MIMO)-path fidelity. The extended flexible joint model, which is identified through a nonlinear gray-box model, is also less susceptible to modeling errors. The performance comparison with two rudimentary digital filters exhibits promising results for both proposed solutions. Finally, a fusion of the two approaches is proposed as a final solution of this work. As a result, the collaborative approach is the closest to ideal vibration avoidance but suffers from greater path deviation. The extended flexible joint model combined with compensation results in the least deviation from the baseline trajectory among all tested approaches., VIBRATIONSDÄMPNING, en teknik för att proaktivt undvika oönskade vibrationer i fleraxlade industrirobotar, har visat sig vara önskvärd i många olika applikationer. En avvägning mellan vibrationsdämpningens prestanda och avvikelser från rörelsebanan har varit viktiga kriterier för att bedöma effektiviteten och kvalitén av ett tillvägagångssätt. Syftet med denna avhandling är att jämföra två toppmoderna tillvägagångssätt för att undvika vibrationer: ingångsformning och utökad flexibel axelmodell kombinerad med specialiserad kompensationskontroll samt utforska sammanslagning av de två. Bägge tillvägagångssätt är först undersökta och utvärderade i en simulation. En jämförelsemellan de fyra standard robotrörelserna som är presenterade är sedan genomförd på en riktig robot. Mellan de två tillvägagångssätten är ingångsformning mindre förståeligt men möjliggör en snabb identifikation vilket gör den lämplig för simpla repetitiva uppgifter. Det fastställs även att axelvis generering av rörelsebanor som används med ingångsformning orsakar lägre noggrannhet och pålitlighet vad gäller avvikelser från rörelsebanan. Detta problem är inte lika påtagligt vid användning av utökad flexibel axelmodell kombinerad med specialiserad kompensationskontroll eftersom detta tillvägagångssätt bevarar synkroniciteten över samtliga axlar och garanterar multi-input multi-output (MIMO) följdriktighet. Den utökade flexibla axelmodellen, som identifieras med hjälp av en icke-linjär gray-box modell, är även mindre mottaglig för modelleringsfel. Prestandajämförelsen med två rudimentära digitala filter uppvisar lovande resultat för bägge föreslagna lösningar. Till sist, en sammanslagning av de två tillvägagångssätt är föreslagen som en slutgiltig lösning. Det sammanslagna tillvägagångssättet är närmast perfekt vibrationsdämpning men medför större avvikelser från rörelsebanan. Den utökade flexibla axelmodellen kombinerad med kompensation resulterar i minst avvikelse från rörelsebanan bland alla testade t

The operation time of an ideal reliable wafer scanner model is defined at the die level where the actual exposure process takes place as the time unit per die, or at the wafer substrate level as the time unit per wafer substrate. Therefore, the machine throughput is given as the reciprocal of the operation time. The involved motion profiles of a machine, namely the step-and-scan trajectories, function as the heartbeats that drive its multidisciplinary elements, which suggests that a multidisciplinary design optimization should be involved when such profiles are selected or designed. This is also true when considering the traverse motion profiles among rows and columns within the wafer substrate. The step-and-scan trajectories affect the machine throughput, performance, and die yield. The effects of tracking such profiles appear as structural vibration, tracking errors, and thermal loading at various machine elements such as the actuators, the reticle, the wafer, and the projection elements specifically when the exposure high-energy duration and frequency are not taken into consideration while designing the reference motion. From the dynamics perspective, having a reference motion with nonzero and bounded higher-order derivatives is recommended since it enhances the tracking performance of the machine, however, its ability to increase the operation time is usually overlooked. In an attempt to understand such effects, we present a case study that outlines the aforementioned aspects using three step-and-scan profiles of mainly $3^{rd}$ -order. Taking the dynamics of the driven stage into consideration through input shaping, both the step-and-scan and traverse motion profiles are analyzed. We provide analytical expressions that can be used to generate both types of motion profiles on the fly without additional optimization. A simulation example of a simplified wafer scanner machine shows the usefulness of the proposed framework. Note to Practitioners - Choosing the m

We present a framework that allows designing point-to-point closed-form trajectories and identifying flexible modes, jointly. The impulse response of a k-cascaded second-order notch filter is altered by composing it with a polynomial function of even degree in the time domain. The filter impulse response parameters are designed based on the available prior knowledge about the lightly-damped uncertain modes of the driven stage. The resulting chirps signals suppress the response of these oscillatory modes within selected suppression bands in the frequency domain. To check for unknown flexible modes within any desired frequency intervals of interest, the complement of the suppression bands is excited using excitation chirps signals. Using transmissibility, then the frequencies associated with the unknown flexible modes are identified, and the k-cascaded notch filter is updated accordingly. This update process may involve optimizing the parameters of the original filter, or the new filter when the order k changes. Also, real-time trajectory extrapolation is guaranteed under the proposed framework by the simple calculations required. The effectiveness of the proposed framework is illustrated through a numeric simulation example where the integration of both kinematic and dynamic constraints gives rise to the notion of kinodynamical trajectories.

Working with a physical system, the search for a model (plant) could be computed mainly via physical equations or system identification when input/output data is available. Models which closely describe physical systems are difficult or impossible to precisely characterize. A model could be thoroughly detailed but it is never an exact representation of the real physical system; and in many applications, noise is clearly present. Modeling errors shall be considered as they might affect the performance of the system. It is at this point where the term uncertainty appears, referring to the differences between the models and the real system. Parametric uncertain models consist of a set of models derived from arange of the uncertain parameters. In linear time-invariant (LTI) control systems, input shaping (IS) is a technique originally used for defining a shaped command input to eliminate or reduce unwanted system vibration. With the input shaping schemes being inherently open-loop, uncertainties in the model can lead to system performance degradation. By its nature, the nominal model-based input shaping cannot compensate for errors in the model, since it rejects any possible variations in the parameters. For parametric uncertain models, a process to compute a robust input signal that works for the set of models derived from the uncertain parameters is required. Robustness in a system is defined as its qualification to generate the desired output over disturbances and uncertainties. In general, robust control consists of the control methods utilized to operate in the uncertain parameters of a model. The process defined in this dissertation considers the problem of robust input shaping, where a single input signal is designed for a range of variability in the parameters of a dynamic model. This work proposes an approach to robust input shaping based on the extreme models, initially derived from the extreme values of the uncertain parameters. Robustness is then achieved by

Working with a physical system, the search for a model (plant) could be computed mainly via physical equations or system identification when input/output data is available. Models which closely describe physical systems are difficult or impossible to precisely characterize. A model could be thoroughly detailed but it is never an exact representation of the real physical system; and in many applications, noise is clearly present. Modeling errors shall be considered as they might affect the performance of the system. It is at this point where the term uncertainty appears, referring to the differences between the models and the real system. Parametric uncertain models consist of a set of models derived from arange of the uncertain parameters. In linear time-invariant (LTI) control systems, input shaping (IS) is a technique originally used for defining a shaped command input to eliminate or reduce unwanted system vibration. With the input shaping schemes being inherently open-loop, uncertainties in the model can lead to system performance degradation. By its nature, the nominal model-based input shaping cannot compensate for errors in the model, since it rejects any possible variations in the parameters. For parametric uncertain models, a process to compute a robust input signal that works for the set of models derived from the uncertain parameters is required. Robustness in a system is defined as its qualification to generate the desired output over disturbances and uncertainties. In general, robust control consists of the control methods utilized to operate in the uncertain parameters of a model. The process defined in this dissertation considers the problem of robust input shaping, where a single input signal is designed for a range of variability in the parameters of a dynamic model. This work proposes an approach to robust input shaping based on the extreme models, initially derived from the extreme values of the uncertain parameters. Robustness is then achieved by

Many manufacturing processes require demanding cycle times that subject industrial robots to sudden motions. For instance, in acoustic perforation of airplane engine housings, thousands of holes are drilled to minimize acoustic emissions. Due to the large number of holes required, drilling is performed at over two holes per second, which requires rapid repositioning of the tool center point. However, due to the structural flexibilities present in industrial robots, rapid movements induce residual vibrations. To avoid violating hole tolerances (<0.2mm), industrial robots must sacrifice cycle time and wait for the vibrations to settle before proceeding to the drilling motion. This thesis presents a novel learning-based framework combined with input shaping techniques to avoid vibrations in sudden motions of an industrial robot. Input shaping is an efficient method to filter harmful frequencies and avoid exciting structural modes in industrial robots. The performance of input shaping relies heavily on the accuracy of the predicted natural frequency. In industrial robots, the dominant natural frequency varies significantly with pose and payload – making prediction within the workspace a challenge. In this thesis, a theoretical flexible-joint dynamic model is developed for the first three joints of an industrial robot to predict the dominant natural frequency for any combination of pose and payload. Model parameters, such as joint stiffness, are experimentally identified to improve the accuracy of the theoretical model. The flexible-joint dynamic model is paired with an artificial neural network for efficient real-time prediction of natural frequency for any pose. Collection and labelling of training data is autonomously performed by simulating the flexible-joint dynamic model. Model adaptation, or transfer learning, is used to quickly map the artificial neural network trained for no payload to a new payload with a 90% reduction in required training data. Finally, the le

Space robotic arm, such as robot manipulator systems on International Space Station (ISS), are usually operated manually by astronauts and ground operators. Such manipulator systems are subject to vibrations due to its flexibility, which cause degradation of the operation accuracy. We use Input Shaping method in order to suppress the vibration. However, when a posture of the arm changes dynamically, we need to improve the scheme of vibration suppression control. We propose the practical manual operation method without additional sensors and actuators. In proposed method, sensing the vibration during robotic arm operation, the parameters for vibration suppression are updated as required. Though a strain gauge is used for sensing the vibration, only actuator's current of each joint is practicable. In this paper, we conduct manual operation experiment, and examine the validity of the proposed manipulation method considering vibration suppression., 実際の宇宙ステーションなどの軌道上においては、オペレータのマニュアル操作によってロボットアームを動作させる場合が多い。そこで、柔軟性を有する6自由度冗長ロボットアームの2次元微小重力環境実験設備を構築し、マニュアル操作実験を実施する。動作中の振動を検知し、振動抑制に必要なパラメータを動作中に随時更新し、システムの振動特性が動的に変化する場合にも、振動を抑制しながら操作する手法を提案し、その有効性を実験にて実証する。実験では、柔軟リンク部に貼付したひずみゲージを利用しているが、各関節の駆動電流値からも実現でき、新たなセンサやアクチュエータを必要とせずに、操作手法の改良のみで、振動を抑制し作業効率を向上することができることを述べる。

This paper presents an adaptive algorithm to reduce residual vibrations when the feedback sensor used has null drift along the time. The adaptive approaches are useful to deal with large variations of the system parameters at each maneuver, such as it occurs in cranes. For the feedback sensor, the use of inertial measurement units such as Micro-Electro-Mechanical Systems (MEMS) is increasingly extended because of their cost, size, robustness and power consumption. However, the effectiveness of the adaptive input shaping algorithms is compromised because of this drift, which is a commonly raised issue in this kind of devices. The study presented in this manuscript focuses on the development of an automatic compensation of this drift to obviate frequent calibrations. It is based on a non-asymptotic algebraic identification technique, which does not require initial conditions and has a short convergence time. This study uses the Zero-Vibration (ZV) input shaper technique, and the null drift is added to the algorithm as a parameter to be identified. The proposed method is particularized for single maneuvers of cranes with a gyroscope as feedback sensor, in a real time scenario. Experimental results show the efficacy of the method on a scaled crane test platform., Postprint (published version)

In synchronization of high-precision stages systems, particularly the one between the wafer stage system and the reticle stage system of a wafer scanner, a novel feedforward control structure capable of achieving zero-settling errors is presented. The synchronization is achieved by including finite impulse response (FIR) filters both in the input and feedforward paths of the control loop. In an iterative process, the coefficients of three FIR filters (a wafer stage feedforward filter, a reticle stage feedforward filter, and an identical wafer stage/reticle stage input shaping filter) are obtained by minimizing a cost function involving the error of each individual stage system and the net error, the latter being the performance indicator. Tracking performance will be demonstrated by simulations and experimental results obtained from an industrial wafer scanner., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

In synchronization of high-precision stages systems, particularly the one between the wafer stage system and the reticle stage system of a wafer scanner, a novel feedforward control structure capable of achieving zero-settling errors is presented. The synchronization is achieved by including finite impulse response (FIR) filters both in the input and feedforward paths of the control loop. In an iterative process, the coefficients of three FIR filters (a wafer stage feedforward filter, a reticle stage feedforward filter, and an identical wafer stage/reticle stage input shaping filter) are obtained by minimizing a cost function involving the error of each individual stage system and the net error, the latter being the performance indicator. Tracking performance will be demonstrated by simulations and experimental results obtained from an industrial wafer scanner., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

This paper presents an approach to design command inputs for the reduction of residual vibrations in mechanical systems for nonzero initial states. The technique starts with the development of a standard input shaper in a second order oscillator, and adds the initial states of the system to the formulation. However, it is proven that the obtained input shaper does not guarantee a null residual vibration when it is convolved with any unshaped command. To obtain an analytically proven zero-vibration response, it is required to include the parameters that characterize the response of the system to a selected normalized unshaped command in the formulation. By introducing an appropriate processing time delay and by measuring the initial states using a feedback sensor, the proposed method has been applied in a real time scenario where an emergency stop of a crane is required, assuming that initially the payload is swaying., Postprint (author's final draft)

We investigate the implementation of nontraditional open-loop and closed-loop control techniques to systems at the micro and macro scales. At the macro level, we consider a quay-side container crane. It is known that the United States relies on ocean transportation for 95% of cargo tonnage that moves in and out of the country. Each year over six million loaded marine containers enter U.S. ports. Current growth predictions indicate that container cargo will quadruple in the next twenty years. To cope with this rapid growth, we develop a novel open-loop input-shaping control technique to mitigate payload oscillations on quay-side container cranes. The proposed approach is suitable for automated crane operations, does not require any alterations to the existing crane structure, uses the maximum crane capabilities, and is based on an accurate two-dimensional four-bar-mechanism model of a container crane. The shaped commands are based on a nonlinear approximation of the two-dimensional model frequency and, unlike traditional input-shaping techniques, our approach can account for large hoisting operations. For operator-in-the-loop crane operations, we develop a closed-loop nonlinear delayed-position feedback controller. Key features of this controller are that it: does not require major modifications to the existing crane structure, accounts for motion inversion delays, rejects external disturbances, and is superimposed on the crane operator commands. To validate the controllers, we construct a 1:10 scale model of a 65-ton quay-side container crane. The facility consists of a 7-meter track, 3.5-meter hoisting cables, a trolley, a traverse motor, two hoisting motors, and a 50-pound payload. Using this setup, we demonstrated the effectiveness of the controllers in mitigating payload oscillations in both of the open-loop and closed-loop modes of operation. At the micro level, we consider a micro optical device known as the torsional micromirror. This device has a tremendous

Residual vibrations degrade the performance of many systems. Due to the lightweight and flexible nature of space structures, controlling residual vibrations is especially difficult. Also, systems such as the Space Shuttle remote Manipulator System have frequencies that vary significantly based upon configuration and loading. Recently, a technique of minimizing vibrations in flexible structures by command input shaping was developed. This document presents research completed in developing a simple, closed- form method of calculating input shaping sequences for two-mode systems and a system to adapt the command input shaping technique to known changes in system frequency about the workspace. The new techniques were tested on a three-link, flexible manipulator.