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Semi-active suspensions have much better performance than the passive suspensions along with the advantages such as low power consumption and cost. In order to control the semi-active suspension system, such as MR damper, sensory feedback is required. The skyhook control which is the most widely used algorithm admits the velocity of damper and vertical sprung mass. For this, additional attachment, such as a displacement sensor (e.g., an LVDT) or an accelerometer at the sprung mass is required. The present study proposes a method for estimating the damper speed from a pre-existing IMU sensor and a lower damper accelerometer considering the damper orientation in practice. It was validated that the performance of the skyhook-controlled suspension matches with the proposed algorithm.

Three-dimensional (3D) bioprinting of self-supporting stable tissue and organ structure is critically important in extrusion-based bioprinting system, especially for tissue engineering and regenerative medicine applications. However, the development of self-standing bioinks with desired crosslinking density, biocompatibility, tunable mechanical strength and other properties like self-healing, in situ gelation, drug or protein incorporation is still a challenge. In this study, we report a hydrogel bioink prepared from alginate (Alg) and hyaluronic acid (HA) crosslinked through multiple crosslinking mechanisms, i.e. acyl-hydrazone, hydrazide interactions and calcium ions. These Alg-HA gels were highly dynamic and shear-thinning with exceptional biocompatibility and tunable mechanical properties. The increased dynamic nature of the gels is mainly chemically attributed to the presence of acyl-hydrazone bonds formed between the amine groups of the acyl-hydrazide of alginate and the monoaldehyde of the HA. Among the different combinations of Alg-HA gel compositions prepared, the A5H5 (Alginate-acyl-hydrazide:HA-monoaldehyde, ratio 50:50) gel showed a gelation time of ∼60 s, viscosity of ∼400 Pa s (at zero shear rate), high stability in various pH solutions and increased degradation time (>50 days) than the other samples. The A5H5 gels showed high printability with increased post-printing stability as observed from the 3D printed structures (e.g. hollow tube (∼100 layers), porous cube (∼50 layers), star, heart-in, meniscus and lattice). The scanning electron microscopy analysis of the 3D constructs and hydrogels showed the interconnected pores (∼181 µm) and crosslinked networks. Further, the gels showed sustained release of 5-amino salicylic acid and bovine serum albumin. Also, the mechanical properties were tuned by secondary crosslinking via different calcium concentrations. In vitro assays confirmed the cytocompatibility of these gels, where the 3D bioprinted lattice and tubular (∼70 layers) constructs demonstrated high cell viability under fluorescence analysis. In in vivo studies, Alg-HA gel showed high biocompatibility (>90%) and increased angiogenesis (threefolds) and reduced macrophage infiltration (twofold decrease), demonstrating the promising potential of these hydrogels in 3D bioprinting applications for tissue engineering and regenerative medicine with tunable properties.

In this study, a mobile robot and a manipulator were integrated and implemented using ROS (Robot Operating System). Using computer vision, the robot was intended for delivering objects such as beverages and cans to customers in service environments such as cafes and restaurants, and it will contribute to improvement in work efficiency and service automation. To reduce production costs and weight, we adopted the 4-axis manipulator with gears and motors inside the link so that the manipulator occupied a minimum space within the operating range. To achieve free movement in a narrow workspace, direct drive mechanism with low-cost geared motors was adopted for the mobile platform.

Background After recognition of 3D printing and injectable hydrogel as a critical issue in tissue/organ engineering and regenerative medicine society, many hydrogels as bioinks have been developed worldwide by using polymeric biomaterials such as gelatin, alginate, hyaluronic acid and others. Even though some gels have shown good performances in 3D bioprinting, still their performances do not meet the requirements enough to be used as a bioink in tissue engineering. Method In this study, a hydrogel consisting of three biocompatible biomaterials such as hyaluronic acid (HA), hydroxyethyl acrylate (HEA) and gelatin-methacryloyl, i.e. HA-g-pHEA-gelatin gel, has been evaluated for its possibility as a bioprinting gel, a bioink. Hydrogel synthesis was obtained by graft polymerization of HEA to HA and then grafting of gelatin- methacryloyl via radical polymerization mechanism. Physical and biological properties of the HA-based hydrogels fabricated with different concentrations of methacrylic anhydride (6 and 8%) for gelatin-methacryloylation have been evaluated such as swelling, rheology, morphology, cell compatibility, and delivery of small molecular dimethyloxalylglycine. Printings of HA-g-pHEA-Gelatin gel and its bioink with bone cell loaded in lattice forms were also evaluated by using home-built multi-material (3D bio-) printing system. Conclusion The experimental results demonstrated that the HA-g-pHEA-gelatin hydrogel showed both stable rheology properties and excellent biocompatibility, and the gel showed printability in good shape. The bone cells in bioinks of the lattice-printed scaffolds were viable. This study showed HA-g-pHEA-Gelatin gel’s potential as a bioink or its tissue engineering applications in injectable and 3D bioprinting forms.

The present study has focused on the comparison of MR damper dynamic models for the purpose of hardware in the loop simulation. A vehicle dynamic model for large-sized bus and a control logic for MR damper was built. Two typical MR damper models, viz. Bouc-Wen and hyperbolic tangent model have been considered in this study and the advantages and disadvantages of each model on the aspect of HILS system is discussed. We discussed the limitations of each model based on the analysis of the vehicle dynamic simulation. The results showed that the existing models are not suitable for HILS system. We proposed the modified hyperbolic tangent model by adopting low-pass filters. The results from the simulation showed the advantages of the modified model which were validated through HILS system.

In this study, we developed a 3D chocolate printer and studied the conditions needed for chocolate printing. Because chocolate is a mixture of cocoa mass, cocoa butter and sugar particles, its properties vary with temperature, and care is required in melting and extrusion. A chocolate supply unit is composed of a heating block and a syringe pump. It is integrated with a 3-axis linear robot. In order to be more accurate than the existing 3D chocolate printer is, the system was configured so that the printing line width became 430 μm. Printing performance was studied according to various parameters. The condition needed for printing lines with a stable width was discovered by the experimental design method and has been confirmed by a 2D line test. These 3D printing experiments showed that it was possible to build a 3D shape with an inclination angle of up to 45° without support. Further, chocolate printing of a 3D shape has been successfully verified with the developed system.

Three-dimensional (3D) printing technology is considered to be a major driving innovation in tissue engineering, since a custom-made manufacturing for patients is essential for tissue and organ generation. Depending on the bio-materials and the applications, various 3D bio-printing technologies are used. A system capable of printing a variety of bio-materials through various methods is required for fabrication of hybrid scaffolds for tissue engineering research. This paper describes the design and integration of a multi-channel 3D bio-printing system at an affordable price based on open source hardware and software. The hardware and software components of the 3D bio-printing system and the process of finding optimal printing conditions are described in the paper. Fabrication of the hybrid scaffold of synthetic polymer and cell loaded hydrogel are presented to validate the performance of the system.

CFD simulations of spray tip penetration with the standard KIVA3V, ‘original gas jet’ and ‘Normal gas jet profile with breakup length formula’ (NGJBL) spray models were performed to investigate the effects of nozzle orifice size and ambient gas density combinations on the spray penetration. The accuracy of the CFD simulation results was estimated by comparing them with available experimental data. The ambient gas density was varied in 12 kg/m3 intervals from 12 to 69 kg/m3 for each nozzle orifice diameter. The nozzle orifice diameters used were 119, 140, 183 and 206 mm. A total of 20 cases in the CFD simulations were considered with combinations of the 4 nozzle orifice diameters and 5 ambient gas densities. CFD simulations with the NGJBL spray model were more accurate than those with either the standard KIVA3V or gas jet spray models as the nozzle orifice diameter and ambient gas density was increased. The NGJBL and original gas jet model is more effective in predicting the spray tip penetration near the nozzle tip region.

In this study, carboxymethyl cellulose (CMC)-glycol chitosan (GC) hydrogel, a potential three-dimensional (3D) printing biomaterial ink for tissue engineering applications was synthesized using simple, biocompatible in situ-gelling Schiff's base reaction and ionic interactions. Different grades of hydrogels (C70G30, C50G50 and C30G70) were synthesized at physiological conditions. The oxidation of CMC and imine bond formation in the hydrogel were confirmed spectroscopically. Scanning electron microscopic images revealed the crosslinked interconnected pores in the cross-sectioned hydrogels (dried). Swelling (equilibrium: 1 h), porosity (~75%), in vitro degradation (>30 days) and thermal gravimetric analyses of the dried gels were studied. Initially, cytotoxicity assay was evaluated using mouse osteoblastic cells (MC3T3). These experiments revealed that CMC-GC gels formed stable hydrogel networks and were biocompatible. Particularly, C50G50 gels showed high printability (continuous extrusion) and post-printing stability (without secondary crosslinking). Gel 3D printing was optimized by varying the air pressure, temperature, needle size and nozzle speed, to obtain stable lattice structures (2 to 16 layers). The printed (2 and 5 layers) hydrogels showed high stability in phosphate buffer saline (PBS) solution (1 h), under UV light (1 h) and after autoclaving. The strut dimensions and porosity of the printed gels before and after the stability tests were analyzed. The hydrogel stability may be attributed to both the imine bond and ionic interaction between the cationic and anionic polymer side chains. Lactoferrin (glycoprotein) incorporated C50G50 gels showed sustained release up to 21 days in PBS (pH 7.4) solution and demonstrated increased biocompatibility (>80%) during in vitro cytotoxicity assays (MC3T3 cells and bone marrow mesenchymal stem cells) and Live/Dead assay (MC3T3 cells). A higher number of live osteoblast cells on the C50G50 hydrogels with increasing lactoferrin concentration was observed. These results show that the CMC-GC gels are promising bio-ink candidates for 3D printing and loading proteins or drugs for tissue engineering applications.

Article history: Projection stereolithography is an additive manufacturing method that uses beam projection to cure the photo-reactive resin used. The light source of a crosssection layer-form illuminates photo-curable resin for building a threedimensional (3D) model. This method has high accuracy and a fast molding speed because the processing unit is a face instead of a dot. This study describes a Scalable Projection Stereolithography 3D Printing System for improving the accuracy of the stereolithography. In a conventional projection 3D printer, when printing a small sized model, many pixels are not used in the projection or curing. The proposed system solves this problem through an optical adjustment, and keeps using the original image as possible as filling the whole projection area. The experimental verification shows that the proposed system can maintain the highest level of precision regardless of the output size.

Owing to miniaturization and low-power electronics, mobile, implanted, and wearable devices have become the main trends of electronics during the past decade. There has been much research regarding energy harvesting to achieve battery-free or self-powered devices. The optimal design problems of a double-pendulum kinetic-energy harvester from human motion are studied in this paper. For the given form factor, the weight of the harvester, and the known human excitation, the optimal design problem is solved using a dynamic non-linear double-pendulum model and an electric generator. The average electrical power was selected as the performance index for the given time period. A double-pendulum harvester was proven to be more efficient than a single-pendulum harvester when the appropriate parameters were used.

To avoid radiation exposure from repeated x-rays taken during orthopedic surgery, an x-ray permeable teleoperated Stewart platform for orthopedic fracture surgery was developed. This system is composed of a user interface device and a teleoperated operational robot, both of which use a Stewart platform mechanism. The links of the operational robot are made from an x-ray permeable material, polycarbonate, to minimize the interference. The forward and inverse kinematics algorithm applied and the structural reliability were both verified through an analysis using commercial engineering software. To monitor the operating status in real time and stop the device during an emergency, a monitoring software was developed. The performance of the x-ray permeable teleoperated Steward platform was validated experimentally.

One of the primary challenges in extrusion-based 3D bioprinting is the ability to print self-supported multilayered constructs with biocompatible hydrogels. The bioinks should have sufficient post-printing mechanical stability for soft tissue and organ regeneration. Here, we report on the synthesis, characterization and 3D printability of hyaluronic acid (HA)–carboxymethylcellulose (CMC) hydrogels cross-linked through N-acyl-hydrazone bonding. The hydrogel’s hydrolytic stability was acquired by the effects of both the prevention of the oxidation of the six-membered rings of HA, and the stabilization of acyl-hydrazone bonds. The shear-thinning and self-healing properties of the hydrogel allowed us to print different 3D constructs (lattice, cubic and tube) of up to 50 layers with superior precision and high post-printing stability without support materials or post-processing depending on their compositions (H7:C3, H5:C5 and H3:C7). Morphological analyses of different zones of the 3D-printed constructs were undertaken for verification of the interconnection of pores. Texture profile analysis (TPA) (hardness (strength), elastic recovery, etc) and cyclic compression studies of the 3D-printed constructs demonstrated exceptional elastic properties and fast recovery after 50% strain, respectively, which have been attributed to the addition of CMC into HA. A model drug quercetin was released in a sustained manner from hydrogels and 3D constructs. In vitro cytotoxicity studies confirmed the excellent cyto-compatibility of these gels. In vivo mice studies prove that these biocompatible hydrogels enhance angiogenesis. The results indicate that controlling the key properties (e.g. self-crosslinking capacity, composition) can lead to the generation of multilayered constructs from 3D-bioprintable HA-CMC hydrogels capable of being leveraged for soft tissue engineering applications.

Smoke emissions of diesel vehicles were measured using KD147 mode and the results were analyzed. The representative smoke value for the tested diesel vehicle is calculated by averaging five consecutive smoke measurement points which consists of a maximum smoke point over the KD147 mode, two points before the maximum and two points after the maximum with the measurement time interval of 0.25 second. To use the five points averaging smoke value as a representative smoke emission value for the tested vehicle has problem that it cannot include other several peak points during the KD147 mode driving. A new method for deciding a representative smoke value for the tested diesel vehicle was researched. Multiple smoke emission peaks over the KD147 were detected. The multiple smoke emission peaks are averaged for getting the representative smoke value for the tested vehicle.

Because of high oil prices and emission gas problems, many governments tighten regulation of fuel economy and emission gas. For Passenger car, there are many researches for plug-in hybrid electric vehicles and they are being manufactured. On the other hand, there are few researches for plug-in hybrid electric bus that is heavy commercial vehicle. In this study, analysis of fuel economy for series plug-in hybrid electric bus according to engine operation strategy based on simulation is conducted. Forward simulator is developed using Autonomie. Engine operation strategies consist on constant engine operation strategy and engine on/off operation strategy. Considering the engine operation strategy, results of vehicle speed, engine operating points and fuel economy are obtained and analyzed. As a result, engine on/off operation strategy has more advantage than constant engine operation strategy in terms of fuel economy. Key words : Series plug-in hybrid electric vehicle(직렬형 플러그인 하이브리드 전기 자동차), Forward simulation(전방향 시뮬레이션), Engine operation strategy(엔진 구동 전략), Fuel economy(연비)

Article history: This study proposes a closed-loop shaping control method with H∞ optimization for optical image stabilization (OIS) in mobile phone cameras. The image stabilizer is composed of a horizontal stage constrained by ball bearings and actuated by the magnetic force from voice coil motors. The displacement of the stage is measured by Hall effect sensors. From the OIS frequency response experiment, the transfer function models of the stage and Hall effect sensor were identified. The weight functions were determined considering the tracking performance, noise attenuation, and stability with considerable margins. The H∞ optimal controller was executed using closed-loop shaping and limiting the controller order, which should be less than 6 for real-time implementation. The control algorithm was verified experimentally and proved to operate as designed.

This study addresses the development of a full duplex robotic system for transferring flat-panel display glass. We propose to accomplish this using a bidirectional linear transfer mechanism in place of the conventional rotary transfer mechanism. The developed full duplex robot comprises a driving part that carries the glass panel laterally, vertical part that can be moved up and down by means of a ball screw and linear motion guide arrangement, and hand part that slides by the cylinder of the driving part along the guide rail with a V-guide bearing attached to the bottom of the support. In addition, an alignment part prevents the hand part from derailing and holds the hand part while the driving part moves horizontally. The full duplex robot lifts and drives a glass panel directly while transferring it to the buffer and does not require rotational motion. Therefore, both transferring and stacking are realized with a single device. This device can be used in existing industrial facilities as an alternative to existing industrial robots in current as well as future process lines. The proposed full duplex robot is expected to save considerable amounts of time and space, and increase product throughput.

Until recently, the primary users of wheelchairs were people with lower body disabilities. However, the number of patients recovering from accidents or surgery, as well as the number of elderly people using wheelchairs, is constantly increasing. This study examined the design and manufacture of standing and gait assist wheelchairs that assist temporary gait disturbed patients to take rehabilitation training and elderly people to engage in walking exercise. A kinematic analysis was used to select a drive motor and design a four-bar linkage mechanism for lifting the backrest vertically. Using a multibody dynamic simulation, detailed design was performed taking into consideration the spatial motion and partial interference, and the necessary push force and stroke of the linear actuator were also calculated. To ensure structural safety, the von-Mises equivalent stresses of the upper and lower brackets of the linear actuator were verified through a finite element analysis. The manufactured wheelchair was shown to operate successfully as intended, using the developed controller for the drive motors and linear actuator.

In this study, a test-bench for developing and verifying a 1- or 2-axis nanopositioner was manufactured. Using this test-bench, adesigned and manufactured flexure stage based on an analysis can configure nanopositioning systems. A breadboard and fixture were fabricated to be equipped with various types of mechanisms and sizes of stages. The test-bench has linear encoders for calibrating sensors and verifying the orthogonality and parasitic motion of 2-axis nested-type nanopositioners. The controller was developed using LabVIEW and a TI microcontroller. A case study that exemplified the test bench for developing a nanopositioner by senior undergraduate students is shown.

In this paper, a novel radial beam coupling model was proposed and the design parameters were studied for the efficient transmission of torque. To develop a high performance radial beam coupling, an analytical way to predict the performance in design phase is required. One of the best ways to estimate the performance of the coupling without manufacturing is to evaluate the stress and torsional stiffness by building a finite element model with a special attention to the radial beam cutting part. For the best results of FEA, the material properties were obtained through testing. To verify the reliability of finite element model, the results of FEA were compared with the experiments. The main design parameters of radial beam cutting width, radial beam cutting depth, and radial beam cutting direction were considered for the performance of radial beam coupling.

In the current research, we performed quantitative characterization of commercially available photo papers with respect to chemical composition and physical properties in order to find the preferred photo paper with the best electrical conductivity through in situ silver nanoparticle sintering. The composition ratio of chloride ions, surface roughness and pore size of the photo papers were quantitatively analyzed. The relationship of the above-mentioned parameters with the conductivity of the silver nanoparticle pattern formed on the printed surface was explored. The experimental results showed that chloride ions on the surface of photo papers activated the decomposition of a capping agent and sintering between the silver nanoparticles. It was also found that the chloride ions above a certain value did not affect the sintering. The surface roughness and pore size of the photo papers were found to be inversely related to the conductivity of electrode pattern. Moreover, it was found that additional heat treatment (for a relatively short time at a low temperature) contributed to the improvement of conductivity. However, this effect varied depending upon the characteristics of the photo papers. This newly developed inexpensive method using a highly accessible substrate will be very helpful for future paper electronics related devices and research.

This paper examines a coordinated feedback and feedforward control design strategy for precision motion control (PMC) systems. It is assumed that the primary exogenous signals are repeated; including disturbances and references. Therefore, an iterative learning control (ILC) feedforward strategy can be used. The introduction of additional non-repeating exogenous signals, including disturbances, noise, and reset errors, necessitates the proper coordination between feedback and feedforward controllers to achieve high performance. A novel ratio of repeated versus non-repeated signal power in the frequency domain is introduced and defined as the repetitive-to-non-repetitive (RNR) ratio. This frequency specific ratio allows for a new approach to delegating feedback and feedforward control efforts based on RNR value. A systematic procedure for control design is given whereby the feedback addresses the non-repeating exogenous signal content (RNR ≪ 0 dB) and the feedforward ILC addresses the repeating signal content (RNR ≫ 0 dB). To illustrate the design approach, two case studies using different nano-positioning devices are given.

In this paper, a design scheme is proposed that separates the issues of sample-profile estimation and amplitude regulation in dynamic-mode atomic force microscopy. In current AFM, the control signal for amplitude regulation is also used as the estimate for the sample-profile. Therefore, the sample profile estimation signal is accurate as long as the sample-profile signal perceived by the cantilever is well within the bandwidth of the control transfer function. In the proposed design scheme, maintaining a constant amplitude while scanning at high bandwidth does not impose limitations on the reconstruction of the sample topography. In fact, we analytically prove that the sample-profile signal estimation problem can be solved independently of the control design scheme for amplitude regulation. Therefore, accurate sample-profile estimations can be obtained even at frequencies near and beyond the closed-loop control bandwidths. However, we show that the robustness of estimation does depend on the control design for regulation and in fact, the robustness of estimation is described by the closed-loop sensitivity transfer function. The independence of the profile-estimation problem from the control design is another salient distinguishing characteristic of this work. The estimation bandwidths by this new scheme are improved significantly over commonly used signals. Comparison with the existing methods of using the control signal as the image is provided. The experimental results corroborate the theoretical development.

This paper proposes a 2-DOF robust optimal control design method for achieving multiple objectives of resolution, bandwidth, and robustness to modeling uncertainties in nanopositioning systems. The main theoretical contribution of this paper is the formulation of a multiobjective 2-DOF optimal control problem in terms of linear matrix inequalities, which are then solved using standard convex optimization tools. The main distinguishing feature of this approach is the flexibility this method provides in formulating and solving the optimization problems that results in achieving a larger set of performance specifications. It facilitates solving of a certain class of mixed-norm optimization and pole-placement problems that arise naturally in nanopositioning systems. This methodology is demonstrated through experiments on a nanopositioning system that archives performance specifications, which are impossible with 1-DOF designs. Experimental results also demonstrate over 200% improvement in bandwidth of the resulting nanopositioning system over the optimal 1-DOF control designed for the same resolution and robustness specifications.

This paper introduces a two degree of freedom control design for achieving robust high resolution, high bandwidth positioning systems. Feedback designs have demonstrated a significant improvement in the performance of the flexure-stage based positioning systems in atomic force microscopes (AFM) that provide large travels with high resolution. In this paper, an optimal model matching framework, where both the feedback and feedforward controllers form the decision variables, is presented which facilitates achieving better performance in terms of the resolution bandwidth and robustness to modeling uncertainties in the closed-loop device. Feedback-only designs, which significantly diminish nonlinear effects of piezoactuation and other modeling uncertainties, are restricted by practical and fundamental limitations such as the control saturation and the Bode integral law. These limitations, which become even more prominent due to non-minimum phase zeros in the context of flexure stages with non-collocated actuators and sensors, typically lead to trade-off between resolution, bandwidth and the robustness of the positioning system. A two degree of freedom controller, achieves a better trade-off by exploiting feedforward designs that are not subject to some limitations that constrain the feedback-only designs. We show that our 2DOF design achieves performance objectives that are impossible for feedback-only designs. Experiments on positioning stages on a AFM show bandwidth improvements as large as 300% over existing feedback base designs.

This paper proposes a new dynamic mode of operation in an Atomic Force Microscope (AFM) where the deflection signal is used for force regulation instead of its derivatives such as the amplitude and phase. This mode is especially useful in AFMs with high speed positioning systems with bandwidths of the order of ≈ 1/10 times the natural frequency of the scanning probe. We formulate this problem in an optimal control setting and employ multiobjective optimization techniques to design the regulating controller. Furthermore, we present a method to estimate the tip-sample interaction force and extract the sample topography information from this estimate. The overall scheme facilitates high speed imaging that can potentially exploit fast scanning devices without compromising on the bandwidth and resolution. Simulation results show a regulation bandwidth of 10−15% of the natural frequency of the probe.

This paper proposes a new method for the control design for reference tracking in a two degree-of-freedom (2DOF) robust optimal control framework. The main contribution of this paper is formulation of 2DOF multi-objective optimal control problem in terms of linear matrix inequalities. The proposed method enables formulating and solving for a larger set of performance specifications than existing conventional 2DOF designs. This method also provides a platform for implementing mixed-norm optimization problems that model many tracking applications. The theoretical results are corroborated by experiments that apply the proposed control design for a tracking problem on a positioning system.

This paper presents, reviews, compares, and analyzes optimal-control methods for designing two-degree-of-freedom (2DOF) control laws for nanopositioning. The different methods are motivated by various practical scenarios and difficulty in achieving simultaneously multiple performance objectives of resolution, bandwidth, and robustness by tuning-based or shaping-of-open-loop-plants based designs. In this context, we study fundamental trade-offs between these performance objectives in 2DOF control designs for nanopositioning systems. In particular, in terms of the trade-offs, our analysis shows that the primary role of feedback is providing robustness to the closed-loop device whereas the feedforward component is mainly effective in overcoming fundamental algebraic constraints that limit the feedback-only designs. Experimental results indicate substantial improvements (over 200% in bandwidth) when compared to optimal feedback-only controllers.

This paper studies and analyzes fundamental trade-offs between positioning resolution, tracking bandwidth and robustness to modeling uncertainties in two-degree-of-freedom (2DOF) control designs for nanopositioning systems. The analysis of these systems is done in optimal control setting with various architectural constraints imposed on the 2DOF framework. In terms of these trade-offs, our analysis shows that the primary role of feedback is providing robustness to the closed-loop device whereas the feedforward component is mainly effective in overcoming fundamental algebraic constraints that limit the feedback-only designs. This paper presents (1) an optimal prefilter model matching design for a system with an existing feedback controller and (2) a simultaneous feedforward and feedback control design in an optimal H ∞ mixed sensitivity framework. The experimental results on applying these controllers show a significant improvement, as high as 330% increase in bandwidth for similar robustness and resolution level over optimal feedback-only designs. Other performance objectives are similarly improved.We demonstrate that the 2DOF freedom design achieves performance specifications that are analytically impossible for the feedback-only design.