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This paper investigates the problem of a decoupled disturbance compensator (DDC) based stochastic sliding mode control (SMC) design for discrete linear time-invariant systems. In the developed method, the actual disturbance is estimated using the DDC method to design the control input and stabilize the system. The proposed method allows the disturbance compensation to be modified separately from the control input, since the two inputs of system are completely decoupled. To demonstrate the effectiveness of the DDC based discrete-time stochastic SMC, its performance is compared with that of the existing methods using the simulation results. Finally, experimental results are presented to demonstrate the effectiveness of the proposed method.

This paper proposes a deep reinforcement learning (deep RL) method for simultaneously designing several notch filters in complex industrial servo systems. Notch filters are highly effective for suppressing resonances in motion control systems and are widely utilized in industry. However, severe limitations exist in complex servo systems because there are many vibration modes that are difficult to identify. In such cases, several notch filters must be used, but the task of tuning these filters involves lengthy empirical procedures by well-experienced engineers. To automate this tuning process, this paper proposes a novel design method that can design several notch filters simultaneously for the first time. In this method, a deep deterministic policy gradient (DDPG) algorithm with a vector stability margin as the reward function is utilized to find filter parameters in the frequency domain. The proposed method simultaneously finds a set of many parameters for several notch filters that are optimal with respect to stability. Using a real industrial servo system that has multiple resonances, it is demonstrated that the proposed method effectively finds the optimal parameters for several notch filters and successfully suppresses multiple resonances to provide desired performances.

This article presents a novel method of dealing with disturbances and control saturation in the framework of discrete-time sliding mode control (DSMC). A DSMC with decoupled disturbance compensator (DDC) was developed for SMC to recover the loss of stability in the discrete-time domain. However, windup phenomena occur in both the switching function and the disturbance estimate when control saturation occurs, and the method cannot guarantee stability. The article develops a new method for maintaining stability under both disturbances and control saturation by incorporating a novel auxiliary state into the DSMC with DDC method. The auxiliary state prevents the windup phenomena, and the developed new method preserves the asymptotic convergence property of the disturbance estimation error dynamics and the stability of the sliding mode dynamics. Also, the error states are stable under bounded disturbances and control saturation. Simulations and experiments are performed on a commonly used industrial servo system to demonstrate the effectiveness of the proposed method.

This paper presents a three-axis biomimetic gyroscope, mimicking the haltere of Diptera. Diptera use a club-shaped mechanosensory organ called the haltere to get the three-axis angular velocity information, namely roll, pitch and yaw axes, for flight control. One pair of halteres is physically connected to the wings of Diptera that vibrate in antiphase to the flapping wings in ambient air. They sense the Coriolis force and relay angular velocity information to the Diptera. As an alternative to the conventional micro-electro-mechanical system gyroscopes which are widely used in robotics, many research groups have attempted to mimic the haltere. However, no previous study succeeded in measuring all three-axis components of angular velocity, due to various shortcomings. In this paper, we developed the first three-axis haltere-mimicking gyroscope. Two perpendicularly positioned haltere-mimicking structures that can vibrate at a 180° amplitude were mechanically integrated into a robot actuator. Two accelerometers, placed at the tip of each structure, were employed to measure the Coriolis force. The performance of the novel biomimetic gyroscope was measured in all rotational directions, using a motion capture system as the ground truth. One-axis input experiments were performed 240 times at different input magnitudes and directions, and the measured orientation error was less than ±2.0% in all experiments. In 80 three-axis input experiments, the orientation error was less than ±3.5%.

This paper presents a harsh-environment visual odometry method that is robust to the robot orientation as well as the camera movement in an outdoor environment. The accuracy of visual odometry in robots can be enhanced by using additional sensor measurements such as an encoder, gyroscope, and/or magnetometer. This strategy can even reduce the computational time. However, in an outdoor environment, the moving robot can experience vibration, which causes unsynchronized data fusion between the camera and additional sensors. This unsynchronized data fusion causes errors in the robot orientation, which can lead to unwanted large drift errors in localization. To overcome this problem, firstly two distinctively different characteristics of the gyroscope and the magnetometer are combined to estimate the robot orientation. The initial robot orientation is estimated by integration of the gyroscope input, and this initial robot orientation is corrected using the magnetometer data in bundle adjustment. Secondly, the poses of the robot and the camera are estimated separately, and these separately estimated poses of the robot and the camera are used in feature matching and bundle adjustment to reduce drift errors in localization in the outdoor environment. The performance of the proposed method is demonstrated using dataset-based experiments.

This paper presents a performance optimization methodology for the discrete-time sliding mode control (SMC) with the decoupled disturbance compensator (DDC) and the auxiliary state (AS) for an industrial position control system under control input saturation and disturbance. The discrete-time SMC with DDC and AS (SDA) method prevents windup phenomena in the switching function and the disturbance estimation error. Therefore, it provides robust performance under control input saturation, disturbances, as well as parametric uncertainties. However, it is difficult to relate several design parameters to the desired performance. In this paper, a systematical design framework for the discrete-time SDA method is developed. Based on the phase portrait of the error state, the error can be made to converge to zero with a fast speed and less oscillation under control input saturation by an offline tuning process. An optimization process is performed in terms of the peak value of the control input. Both numerical simulations and experimental results show the effectiveness of the developed tuning methodology for the discrete-time SDA method.

Air flow measurements provide significant information required for understanding the characteristics of insect movement. This study proposes a four-channel low-noise readout integrated circuit (IC) in order to measure air flow (air velocity), which can be beneficial to insect biomimetic robot systems that have been studied recently. Instrumentation amplifiers (IAs) with low-noise characteristics in readout ICs are essential because the air flow of an insect’s movement, which is electrically converted using a microelectromechanical systems (MEMS) sensor, generally produces a small signal. The fundamental architecture employed in the readout IC is a three op amp IA, and it accomplishes low-noise characteristics by chopping. Moreover, the readout IC has a four-channel input structure and implements an automatic offset calibration loop (AOCL) for input offset correction. The AOCL based on the binary search logic adjusts the output offset by controlling the input voltage bias generated by the R-2R digital-to-analog converter (DAC). The electrically converted air flow signal is amplified using a three op amp IA, which is passed through a low-pass filter (LPF) for ripple rejection that is generated by chopping, and converted to a digital code by a 12-bit successive approximation register (SAR) analog-to-digital converter (ADC). Furthermore, the readout IC contains a low-dropout (LDO) regulator that enables the supply voltage to drive digital circuits, and a serial peripheral interface (SPI) for digital communication. The readout IC is designed with a 0.18 μm CMOS process and the current consumption is 1.886 mA at 3.3 V supply voltage. The IC has an active area of 6.78 mm2 and input-referred noise (IRN) characteristics of 95.4 nV/√Hz at 1 Hz.

A new method is proposed to measure unknown amplitudes of radio frequency (RF) voltages applied to ion traps, using a pre-calibrated voltage divider with RF shielding. In contrast to previous approaches that estimate the applied voltage by comparing the measured secular frequencies with a numerical simulation, we propose using a pre-calibrated voltage divider to determine the absolute amplitude of large RF voltages amplified by a helical resonator. The proposed method does not require measurement of secular frequencies and completely removes uncertainty caused by limitations of numerical simulations. To experimentally demonstrate our method, we first obtained a functional relation between measured secular frequencies and large amplitudes of RF voltages using the calibrated voltage divider. A comparison of measured relations and simulation results without any fitting parameters confirmed the validity of the proposed method. Our method can be applied to most ion trap experiments. In particular, it will be an essential tool for surface ion traps which are extremely vulnerable to unknown large RF voltages and for improving the accuracy of numerical simulations for ion trap experiments.

For high-fidelity quantum operations in ion traps, it is important to maintain the secular frequency of the trapped ions at a constant value. The radial secular frequency is proportional to the amplitude of the radio frequency (RF) signal applied to ion traps. Owing to the changes in the ambient temperature of a helical resonator and the minute vibration of the optical table, the amplitude can vary. Recently, a method for reducing the fluctuation in the RF signal amplitude, using a commercial universal proportional-plus-integral (PI) controller, has been introduced, which, in turn, reduces the secular frequency drift of the trapped ions. The method improves the capability to maintain the secular frequency at a constant value. However, the structure of the controller is fixed, thus, the control method cannot be changed to suit different experimental conditions, and the different feedback configuration cannot be implemented to increase the resolution. In this paper, we develop a field-programmable gate array (FPGA)-based feedback controller that allows the implementation of various automatic control methods and feedback configurations. In our experiments, the fluctuation in the amplitude of the RF signal was 1.806% using a commercial universal PI controller. The fluctuation was reduced to 0.099% using the developed FPGA-based PI controller, and to 0.102% using the developed FPGA-based lag compensator. By employing the developed FPGA control method, many other automating control methods can be applied to achieve a stable and high-performance control of the secular frequency.

We present a compact optical design for a scalable trapped ion quantum processor employing a single high numerical aperture lens for the excitation of ions and collection of photons, both of which are essential for remote entanglement generation. We verified the design by performing a quantum interference experiment between two photons generated by two sets of the proposed design and observed a 82(3) % suppression of coincidence within 8.13 ns time window when the two photons became indistinguishable. This design can be extended for the simultaneous generation of multiple pairs of entangled qubits with existing fiber-array devices.

This paper presents an effective performance shaping methodology of discrete-time sliding mode control (DSMC) with disturbance observer (DOB) based on the analysis of error dynamics. DSMC with DOB exhibits excellent tracking performance and robustness subject to external disturbances and unknowns including uncertain parameters and unmodelled dynamics. In addition, DSMC with DOB can be easily implemented in various control applications attributed to its simple structure and discrete-domain representation. However, the performance cannot be easily predicted by the controller parameters of DSMC with DOB, and much tuning effort is required to achieve the desired performance. This paper derives a relationship between the performance and the controller parameters of DSMC with DOB using a disturbance-to-error transfer function. In addition, a tuning methodology for shaping the performance of DSMC with DOB is also suggested. Finally, the developed analysis is demonstrated experimentally in a commercial linear motor system.

This paper presents a new implementation method for efficient simultaneous localization and mapping using a forward-viewing monocular vision sensor. The method is developed to be applicable in real time on a low-cost embedded system for indoor service robots. In this paper, the orientation of a robot is directly estimated using the direction of the vanishing point. Then, the estimation models for the robot position and the line landmark are derived as simple linear equations. Using these models, the camera poses and landmark positions are efficiently corrected by a local map correction method. The performance of the proposed method is demonstrated under various challenging environments using dataset-based experiments using a desktop computer and real-time experiments using a low-cost embedded system. The experimental environments include a real home-like setting. These conditions contain low-textured areas, moving people, or changing environments. The proposed method is also tested using the robotics advancement through web publishing of sensorial and elaborated extensive datasets benchmark dataset.

This paper presents an application of stereo camera with two different fields of view (FoVs) for both simultaneous localization and mapping (SLAM) and obstacle detection. Stereo camera usually comprises two cameras with the same FoV. However, for high performance SLAM, a camera with a wide FoV is advantageous, and for high performance obstacle detection, a camera with a narrow FoV is advantageous. This paper proposes SLAM and obstacle detection methods using a low-cost stereo camera with one wide FoV camera and one narrow FoV camera. The performance of the proposed method is demonstrated using various dataset-based experiments.

A discrete-time sliding mode control (DSMC) with a decoupled disturbance compensator (DDC) is a nonlinear and robust control method, which is suitable for slowly-varying disturbances. To effectively compensate the disturbances, the gain of the DDC should be designed in a systematic way. This paper presents a frequency-domain design method of the DSMC with DDC in the presence of disturbance and time delay. In addition, a new generalized decoupled disturbance compensator (GDDC) is designed in the frequency domain, which improves the phase response as compared to the conventional DDC. Experimental results on an industrial servo system demonstrate the improved performance of the DSMC with GDDC method.

Estimating the position of a feature point is very important for the performance of visual simultaneous localization and mapping (SLAM). However, various factors, such as camera motion and matching result, influence the estimation accuracy of feature point position. This paper presents a feature-selection method based on matching risk estimation in visual SLAM. The matching risk is estimated for each feature point in the image. In addition, only the feature points with low matching risk are used in triangulation. The performance of the triangulation and visual SLAM applying the proposed method is demonstrated using simulation and experiments, respectively.

This paper presents a design framework for the discrete-time Sliding mode control with Decoupled disturbance compensator and Auxiliary state (SDA) method in industrial servo applications. In particular, the discrete-time SDA method is formulated to provide an excellent tracking performance even in the presence of control input saturation and disturbance. Moreover, it preserves the separation principle of the sliding mode dynamics and the disturbance estimation error dynamics of the original discrete-time Sliding Mode Control (SMC) with Decoupled Disturbance Compensator (DDC) method. However, it can be problematic due to the unpredictable transients in the error states under control input saturation. This paper investigates the error dynamics of discrete-time SDA after a transition from a saturated region to an unsaturated region, which is called the decoupled error dynamics. The decoupled error dynamics can be designed by shaping a “hidden” sliding manifold which is activated only after the transition. Based on the analysis, a systematical design methodology for the decoupled error dynamics is proposed, which prevents the recurrence of the control input saturation and provides fast convergence of the error states. The effectiveness of the proposed design methodology is shown experimentally using an industrial linear motor system.

This paper presents a new discrete derivative method for adaptive notch filter (ANF)-based frequency estimators. ANF-based frequency estimators are widely used for online frequency estimation because of their small computation requirements and simple structures. A discrete-time derivative is usually required for the estimators because they are implemented in the discrete-time domain. However, conventional discretization processes may cause problems in calculating the derivative of the adaptive filter state. For example, a derivative needs to have a phase of 90°, but finite difference methods produce phase responses that are less than 90° in high-frequency ranges. This phenomenon causes inaccurate frequency estimation results in high-frequency ranges. A bilinear transform method can prevent the phase problem, but it has oscillating transient responses, which deteriorate the convergence properties of the estimated frequency. A new discrete derivative method that modifies the bilinear transform is proposed. The proposed method does not produce the oscillating transient response in the steady state. Moreover, the phase responses of this method remain at 90° even in high-frequency ranges. Therefore, the frequency estimators that use the proposed derivative method can accurately estimate the frequencies of input signals in various frequency ranges.

Accumulated electrostatic charges on the dielectric surfaces of ion traps are known to induce stray fields, leading to ion micromotions. In typical microfabricated ion-trap chips, metal electrodes are electrically isolated using thick dielectric pillars, which can accumulate stray charges on their sidewalls. This letter presents a new microfabrication method for ion-trap chips that reduces the exposure of dielectric surfaces to trapped ions. The dielectric pillars are fabricated with large T-shaped overhangs, and the sidewalls and top surfaces are coated with AlCu (1%) films. The bottom sides of the overhang parts provide electrical isolation. To prevent oxidation of the AlCu (1%) films, the electrode surfaces are coated with an additional Au film. The fabricated chips were implemented to trap 174Yb+ ions, and the laser-induced stray fields were measured. The results indicated that the trap chip fabricated by the newly developed method generates significantly smaller stray fields as compared with previous chips. [2017-0233]

A large-scale ion trap array fabricated using the microelectromechanical systems (MEMS) technology is expected to be a promising device for building a practical quantum computer. Shuttling trapped ions is essential for operating scalable ion trap structures. This paper proposes an ion shuttling method for a MEMS-fabricated surface ion trap. Change of secular frequency of trapping potential can cause heating and subsequent loss of ions. Therefore, direct current voltage sets to form uniform ion trapping potentials around the ions while shuttling are calculated by simulations. A 32-channel digital-to-analog converter system is developed to apply the calculated voltage sets to the electrodes of the MEMS-fabricated surface ion trap. The shuttling process is experimented using trapped 174Yb+ ions. The successful round trip of the ion for 1920 μm is demonstrated using the developed approach.

This paper proposes the digital optoelectrical pulse (DOP) method for vernier-type rotary encoders in high-resolution applications. A 25-b encoder using the DOP method is demonstrated. In rotary encoders, the low-bit data of an angle measurement are easily generated using a periodic signal. The high-bit data of an absolute angle measurement can be obtained using various methods such as binary code, gray code, pseudorandom code, $M$ code, or the vernier method. The vernier method has a significant advantage over the above methods for small-sized rotary encoders because it requires fewer grating tracks than do other methods. The vernier method uses grating tracks to generate periodic signals rather than digitally coded signals. In the vernier method, periodic signals with slightly different frequencies are used. The high-bit data of an absolute angle measurement can be obtained using the difference of two periodic signals. Complete absolute angle data are obtained by concatenating the high-bit data and the low-bit data. However, the high-bit data and the low-bit data are, in general, not synchronized. As a result, significant intermediate-bit errors occur at the concatenation point. The DOP method is developed in this paper to mitigate these intermediate-bit error problems. A system on a chip (SoC) that uses the proposed method is designed and fabricated using a 0.18- $\mu \text{m}$ CMOS image sensor process. A 25-b absolute encoder is constructed using an SoC that provides absolute angle data without intermediate-bit errors.

We present a compact optical design for a scalable trapped ion quantum processor employing a single high numerical aperture lens for the excitation of ions and collection of photons, both of which are essential for remote entanglement generation. We verified the design by performing a quantum interference experiment between two photons generated by two sets of the proposed design and observed a 82(3) % suppression of coincidence within 8.13 ns time window when the two photons became indistinguishable. This design can be extended for the simultaneous generation of multiple pairs of entangled qubits with existing fiber-array devices.

We present a numerical study of a MEMS-based design of a fiber cavity integrated with an ion trap system. Each fiber mirror is supported by a microactuator that controls the mirror's position in three dimensions. The mechanical stability is investigated by a feasibility analysis showing that the actuator offers a stable support of the fiber. The actuators move the fibers' positions continuously with a stroke of more than 10 $\mu$m, with mechanical resonance frequencies on the order of kHz. A calculation of the trapping potential shows that a separation between ion and fiber consistent with strong ion-cavity coupling is feasible. Our miniaturized ion-photon interface constitutes a viable approach to integrated hardware for quantum information., Comment: 14 pages, 11 figures, 3 tables

Over the past decade, synthesized nanomaterials, such as carbon nanotube, nanoparticle, quantum dot, and nanowire, have already made breakthroughs in various fields, including biomedical sensors. Enormous surface area-to-volume ratio of the nanomaterials increases sensitivity dramatically compared with macro-sized material. Herein we present a comprehensive review about the working principle and fabrication process of nanowire sensor. Moreover, its applications for the detection of biomarker, virus, and DNA, as well as for drug discovery, are reviewed. Recent advances including self-powering, reusability, sensitivity in high ionic strength solvent, and long-term stability are surveyed and highlighted as well. Nanowire is expected to lead significant improvement of biomedical sensor in the near future.

Silicon nanowires (SiNWs) have received attention in recent years due to their anomalous piezoresistive (PZR) effects. Although the PZR effects of SiNWs have been extensively researched, they are still not fully understood. Herein, we develop a new model of the PZR effects of SiNWs to characterize the PZR effects. First, the resistance of SiNW is modeled based on the surface charge density. The characteristics of SiNW, such as surface charge and effective conducting area, can be estimated by using this resistance model. Then, PZR effects are modeled based on stress concentration and piezopinch effects. Stress concentration as a function of the physical geometry of SiNWs can amplify PZR effects by an order of magnitude. The piezopinch effects can also result in increased PZR effects that are at least two times greater than that of bulk silicon. Experimental results show that the proposed model can predict the PZR effects of SiNWs accurately.

In conventional robotics, charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) cameras have been utilized for acquiring vision information. These devices have problems, such as narrow optic angles and inefficiencies in visual information processing. Recently, biomimetic vision sensors for robotic applications have been receiving much attention. These sensors are more efficient than conventional vision sensors in terms of the optic angle, power consumption, dynamic range, and redundancy suppression. This paper presents recent research trends on biomimetic vision sensors and discusses future directions.

This paper presents a new forward-viewing mono-camera based obstacle detection algorithm for mobile robots. The proposed method extracts the coarse location of an obstacle in an image using inverse perspective mapping technique from sequential images. In the next step, graph-cut based image labeling is conducted for estimating the exact obstacle boundary. The graph-cut based labeling algorithm labels the image pixels as either obstacle or floor as the final outcome. Experiments are performed to verify the obstacle detection performance of the developed algorithm in several examples, including a book, box, towel, and flower pot. The low illumination condition, low color contrast between floor and obstacle, and floor pattern cases are also tested.

In order to provide high-quality visual information to patients who have implanted retinal prosthetic devices, the number of microelectrodes should be large. As the number of microelectrodes is increased, the dimensions of each microelectrode must be decreased, which in turn results in an increased microelectrode interface impedance and decreased injection current dynamic range. In order to improve the trade-off envelope between the number of microelectrodes and the current injection characteristics, a 3D microelectrode structure can be used as an alternative. In this paper, the electrical characteristics of 2D and 3D Au microelectrodes were investigated. In order to examine the effects of the structural difference, 2D and 3D Au microelectrodes with different base areas but similar effective surface areas were fabricated and evaluated. Interface impedances were measured and similar dynamic ranges were obtained for both 2D and 3D Au microelectrodes. These results indicate that more electrodes can be implemented in the same area if 3D designs are used. Furthermore, the 3D Au microelectrodes showed substantially enhanced electrical durability characteristics against over-injected stimulation currents, withstanding electrical currents that are much larger than the limit measured for 2D microelectrodes of similar area. This enhanced electrical durability property of 3D Au microelectrodes is a new finding in microelectrode research, and makes 3D microelectrodes very desirable devices.

This paper presents a novel method for estimating the heading angle of a home service robot. The images captured from a forward viewing mono-camera, gyroscope data, and wheel encoder data are used as sensory inputs. The data rates of camera, gyroscope, and encoder are 1 Hz, 50 Hz, and 50 Hz, respectively. The camera is slightly tilted by 16.5° to increase the amount of visual information obtained. The context of this study is simultaneous localization and mapping (SLAM) in an indoor home environment. The ceiling lines, i.e., the intersection between the ceiling and wall, are used as the only landmarks for the heading angle estimation. In our method, since the ceiling lines are used as the sole landmarks, line parameterization and data association problem can be simplified when compared to the general line based methods. In home environment, the ceiling line features can be easily detected regardless of the robot rotation. The developed method can be used to accurately estimate the global heading angle while the robot is in motion. A ceiling line map is also reconstructed. The reconstructed ceiling line map provides intuitively understandable spatial information about the environment using only a few features. The experimental results demonstrate that it is feasible to use the proposed method for an indoor home environment.

An oral medication of a molecular targeted drug, lapatinib, is taken regularly to maintain the drug concentration within the desired therapeutic levels. To alleviate the need for such cumbersome administration schedules in several drugs, advanced drug delivery systems (DDSs), which can provide time-controlled and sustained drug release, have recently received significant attention. A biodegradable synthetic polymer, such as polycaprolactone (PCL), is usually used as a carrier material for DDSs. In this paper, lapatinib powder-entrapped, PCL microstructures were fabricated with a precise X-ray lithography-based method. In vitro experiments on HER2 positive-human gastric cancer derived NCI-N87 cells were performed to appraise the drug release characteristics of the fabricated DDSs. The in vitro results indicate that after the X-ray lithography process, the lapatinib powder is still working well and show time- and dose- dependent drug release efficiencies. The cell growth inhibition characteristics of one hundred 40-mu m sized microstructures were similar to those of a 1 mu M lapatinib solution for over 144 h. In conclusion, the developed lapatinib-entrapped PCL microstructures can be used in molecular targeted delivery and sustained release as effective cancer-targeted DDSs.

A drug delivery system is used for targeting drugs to specific cells. Various drug carriers, that also reduce the side effects of unbound drugs, have been introduced and commercialized in the pharmaceutical field. Among them, synthetic biodegradable polymers have received much attention attributed to their low toxicity, controllable biodegradation rates, manufacturability, and low costs. This paper reviews the salient characteristics of biodegradable polymers as drug carriers and their microfabrication methods. The reviewed microfabrication methods include laser micromachining, rapid prototyping, replication, emulsification, microfluidic fabrication, and X-ray-lithography-based methods. For these microfabrication methods, critical dimensions, feature variety, solvent compatibility, production throughput, and tooling requirements are also summarized.

In this paper, a new localization system utilizing afocal optical flow sensor (AOFS) based sensor fusion for indoor service robots in low luminance and slippery environment is proposed, where conventional localization systems do not perform well. To accurately estimate the moving distance of a robot in a slippery environment, the robot was equipped with an AOFS along with two conventional wheel encoders. To estimate the orientation of the robot, we adopted a forward-viewing mono-camera and a gyroscope. In a very low luminance environment, it is hard to conduct conventional feature extraction and matching for localization. Instead, the interior space structure from an image and robot orientation was assessed. To enhance the appearance of image boundary, rolling guidance filter was applied after the histogram equalization. The proposed system was developed to be operable on a low-cost processor and implemented on a consumer robot. Experiments were conducted in low illumination condition of 0.1 lx and carpeted environment. The robot moved for 20 times in a 1.5 × 2.0 m square trajectory. When only wheel encoders and a gyroscope were used for robot localization, the maximum position error was 10.3 m and the maximum orientation error was 15.4°. Using the proposed system, the maximum position error and orientation error were found as 0.8 m and within 1.0°, respectively.

Retinal prosthetic devices stimulate retinal nerve cells with electrical signals proportional to the incident light intensities. For a high-resolution retinal prosthesis, it is necessary to reduce the size of the stimulator pixels as much as possible, because the retinal nerve cells are concentrated in a small area of approximately 5 mm × 5 mm. In this paper, a miniaturized biphasic current stimulator integrated circuit is developed for subretinal stimulation and tested in vitro. The stimulator pixel is miniaturized by using a complementary metal-oxide-semiconductor (CMOS) image sensor composed of three transistors. Compared to a pixel that uses a four-transistor CMOS image sensor, this new design reduces the pixel size by 8.3%. The pixel size is further reduced by simplifying the stimulation-current generating circuit, which provides a 43.9% size reduction when compared to the design reported to be the most advanced version to date for subretinal stimulation. The proposed design is fabricated using a 0.35 μm bipolar-CMOS-DMOS process. Each pixel is designed to fit in a 50 μ m × 55 μm area, which theoretically allows implementing more than 5000 pixels in the 5 mm × 5 mm area. Experimental results show that a biphasic current in the range of 0 to 300 μA at 12 V can be generated as a function of incident light intensities. Results from in vitro experiments with rd1 mice indicate that the proposed method can be effectively used for retinal prosthesis with a high resolution.

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 µm-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

The neural stimulators have been employed to the visual prostheses system based on the functional electrical stimulation (FES). Due to the size limitation of the implantable device, the smaller area of the unit current driver pixel is highly desired for higher resolution current stimulation system. This paper presents a 16-channel compact current-mode neural stimulator IC with digital to analog converter (DAC) sharing scheme for artificial retinal prostheses. The individual pixel circuits in the stimulator IC share a single 6 bit DAC using the sample-and-hold scheme. The DAC sharing scheme enables the simultaneous stimulation on multiple active pixels with a single DAC while maintaining small size and low power. The layout size of the stimulator circuit with the DAC sharing scheme is reduced to be 51.98 %, compared to the conventional scheme. The stimulator IC is designed using standard 0.18 μm 1P6M process. The chip size except the I/O cells is 437 μm × 501 μm.

Modern mechatronics systems are implemented digitally. However, the magnitude and phase errors caused in the discretization process severely restrain the control performance in systems with high-frequency components where only a few sampled data points are available per period. This paper presents a new accurate discretization method for mechatronics systems that provide good performance even when intrinsic frequency components are close to the Nyquist frequency which is one-half of the sampling frequency. The bilinear transform method is most commonly used, but it causes oscillations when the initial state error of the output is not zero or when rapid changes occur in the input signal. Several variations of the bilinear transform method have been proposed to improve these problems, but as a tradeoff, they introduce large magnitude and/or phase errors at high frequencies. In this paper, a more accurate discretization method is developed, which combines a modified bilinear transform method with a new method to compensate for the frequency and damping ratio warping caused by approximate discretization. The proposed method reduces the magnitude and phase errors over the entire frequency range. The proposed method is experimentally evaluated in a mechatronics system with a mechanical resonance frequency that is about 0.6 times the Nyquist frequency.

We describe a neural stimulator front-end with arbitrary stimulation waveform generator and adaptive supply regulator (ASR) for visual prosthesis. Each pixel circuit generates arbitrary current waveform with 5 bit programmable amplitude. The ASR provides the internal supply voltage regulated to the minimum required voltage for stimulation. The prototype is implemented in 0.35 μm CMOS with HV option and occupies 2.94 mm₂ including I/Os.

This paper proposes a neural stimulation device integrated with a silicon nanowire (SiNW)-based photodetection circuit for the activation of neurons with light. The proposed device is comprised of a voltage divider and a current driver in which SiNWs are used as photodetector and field-effect transistors; it has the functions of detecting light, generating a stimulation signal in proportion to the light intensity, and transmitting the signal to a micro electrode. To show the applicability of the proposed neural stimulation device as a high-resolution retinal prosthesis system, a high-density neural stimulation device with a unit cell size of 110 × 110 μ m and a resolution of 32 × 32 was fabricated on a flexible film with a thickness of approximately 50 μm. Its effectiveness as a retinal stimulation device was then evaluated using a unit cell in an in vitro animal experiment involving the retinal tissue of retinal Degeneration 1 (rd1) mice. Experiments wherein stimulation pulses were applied to the retinal tissues successfully demonstrate that the number of spikes in neural response signals increases in proportion to light intensity.

Ion traps can provide both physical implementation of quantum information processing and direct observation of quantum systems. Recently, surface ion traps have been developed using microfabrication technologies and are considered to be a promising platform for scalable quantum devices. This paper presents detailed guidelines for designing the electrodes of surface ion traps. First, we define and explain the key specifications including trap depth, q-parameter, secular frequency, and ion height. Then, we present a numerical-simulation-based design procedure, which involves determining the basic assumptions, determining the shape and size of the chip, designing the dimensions of the radio frequency (RF) electrode, and analyzing the direct current (DC) control voltages. As an example of this design procedure, we present a case study with tutorial-like explanations. The proposed design procedure can provide a practical guideline for designing the electrodes of surface ion traps.

This paper presents a monocular vision sensor-based obstacle detection algorithm for autonomous robots. Each individual image pixel at the bottom region of interest is labeled as belonging either to an obstacle or the floor. While conventional methods depend on point tracking for geometric cues for obstacle detection, the proposed algorithm uses the inverse perspective mapping (IPM) method. This method is much more advantageous when the camera is not high off the floor, which makes point tracking near the floor difficult. Markov random field-based obstacle segmentation is then performed using the IPM results and a floor appearance model. Next, the shortest distance between the robot and the obstacle is calculated. The algorithm is tested by applying it to 70 datasets, 20 of which include nonobstacle images where considerable changes in floor appearance occur. The obstacle segmentation accuracies and the distance estimation error are quantitatively analyzed. For obstacle datasets, the segmentation precision and the average distance estimation error of the proposed method are 81.4% and 1.6 cm, respectively, whereas those for a conventional method are 57.5% and 9.9 cm, respectively. For nonobstacle datasets, the proposed method gives 0.0% false positive rates, while the conventional method gives 17.6%.

The concepts of microrobots has been drawn significant attentions recently since its unprecedented applicability in nanotechnology and biomedical field. Bacteria attached microparticles presented in this work are one of pioneering microrobot technology for self-propulsion or producing kinetic energy from ambient for their motions. Microfluidic device, especially utilizing laminar flow characteristics, were employed for anisotropic attachment of Salmonella typhimurium flagellated chemotactic bacteria to 30 um × 30 um and 50 um × 50 um microparticles that made of biodegradable polymer. Any toxic chemicals or harmful treatments were excluded during the attachment process and it finished within 100 s for the anisotropic attachment. The attachments were directly confirmed by fluorescent intensity changes and SEM visualization. Chemotaxis motions were tracked using aspartate and the maximum velocity of the bacteria-attached microrobot was measured to be ~5 um/s which is comparable to prior state of art technologies. This reusable and scalable method could play a key role in chemotaxis delivery of functional microparticles such as drug delivery system.

In this paper, a novel microelectrode array (MEA), with varying arrowhead shapes, is fabricated and evaluated for retinal prostheses. The proposed MEA has a total of 199 arrowhead-shaped microelectrodes, with heights ranging from 42 to 123.5 μm. This height variation allows each microelectrode to contact the spherical eyeball conformably and to approach the stimulation target retinal cells very closely. The fabricated MEAs are implanted in rabbit eyes. The physical contact of the MEA is evaluated using optical coherent tomography (OCT) images, which show that the implanted MEA makes an excellent conformal contact with the spherically shaped retinal layers. These OCT images also exhibit good biocompatibility of the implanted MEA. The evaluation results show that the proposed MEA has a high potential for clinical applications. Our ongoing project is aimed at clinical application in three years. [2010-0037].

This paper presents a low noise accelerometer microsystem with a highly configurable capacitive interface circuit. A programmable capacitive readout circuit is designed to minimize the offset and gain error due to the parasitic capacitance mismatch and the process variations. The interface circuit is implemented in a 0.5 μm 2P3M CMOS technology with EEPROM. The interface circuit and MEMS sensing element are integrated in a single package, and consist the accelerometer microsystem. The supply voltage and supply current of the system are 5 V and 1.17 mA, respectively. The input range and gain are 2.5 V and 0.5 V/g, respectively. The max---min gain error and max---min offset error after calibration was measured to be 1.2% FSO and 3.3% FSO, respectively. The signal to noise ratio (SNR) and noise equivalent resolution (NER) are measured to be 93.1 dB and 110.6 μg/?Hz, respectively, when a 40 Hz, 5 g sinusoidal input acceleration is applied.