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In this study, we introduce a novel design for a three-dimensional (3D) controller, which incorporates the omni-purpose stretchable strain sensor (OPSS sensor). This sensor exhibits both remarkable sensitivity, with a gauge factor of approximately 30, and an extensive working range, accommodating strain up to 150%, thereby enabling accurate 3D motion sensing. The 3D controller is structured such that its triaxial motion can be discerned independently along the X, Y, and Z axes by quantifying the deformation of the controller through multiple OPSS sensors affixed to its surface. To ensure precise and real-time 3D motion sensing, a machine learning-based data analysis technique was implemented for the effective interpretation of the multiple sensor signals. The outcomes reveal that the resistance-based sensors successfully and accurately track the 3D controller's motion. We believe that this innovative design holds the potential to augment the performance of 3D motion sensing devices across a diverse range of applications, encompassing gaming, virtual reality, and robotics. [ABSTRACT FROM AUTHOR]

Image-based cell sorting is essential in biological and biomedical research. The sorted cells can be used for downstream analysis to expand our knowledge of cell-to-cell differences. We previously demonstrated a user-friendly image-activated microfluidic cell sorting technique using an optimized and fast deep learning algorithm. Real-time isolation of cells was carried out using this technique with an inverted microscope. In this study, we devised a recently upgraded sorting system. The cell sorting techniques shown on the microscope were implemented as a real system. Several new features were added to make it easier for the users to conduct the real-time sorting of cells or particles. The newly added features are as follows: (1) a high-resolution linear piezo-stage is used to obtain in-focus images of the fast-flowing cells; (2) an LED strobe light was incorporated to minimize the motion blur of fast-flowing cells; and (3) a vertical syringe pump setup was used to prevent the cell sedimentation. The sorting performance of the upgraded system was demonstrated through the real-time sorting of fluorescent polystyrene beads. The sorter achieved a 99.4% sorting purity for 15 μ m and 10 μ m beads with an average throughput of 22.1 events per second (eps). [ABSTRACT FROM AUTHOR]

Featured Application: Recently upgraded inject-and-transfer system will improve beamtime efficiency for serial femtosecond crystallography. Serial femtosecond crystallography (SFX) using an X-ray free-electron laser (XFEL) can be applied to determine the room-temperature structure of target molecules while minimizing radiation damage and visualizing molecular dynamics. In SFX, a sample delivery system is required to deliver microcrystals to the XFEL beam path in a serial manner. We recently developed a sample delivery method, the combined inject-and-transfer system (BITS), which is a hybrid method based on the injector and fixed-target scanning approach. In this study, we introduced recently upgraded hardware to move the injection needle in the direction of the XYZ-axis and a graphic user interface for user motion control. Furthermore, we report that the viscous solution containing 10% (w/v) PEG 3350 or PEG 6000 that is widely used for protein crystallization can be stably deposited on polyimide film with a hydrophobic surface without any special treatment. Moreover, the development of an inject-and-diffuse method for time-resolved studies with liquid applications in the BITS and its preliminary results are reported. This study provides up-to-date instrument information to SFX users using BITS and provides insights to instrument developers for SFX. [ABSTRACT FROM AUTHOR]

Featured Application: Our results provide insight into the material selection and directions to pursue in developing sample delivery devices used in XFEL studies. A crystal delivery system is essential in serial femtosecond crystallography experiments using an X-ray free-electron laser (XFEL). Investigating the XFEL-induced radiation damage to materials potentially applicable to sample delivery devices is vital for developing a sample delivery system. In this study, we investigated the radiation damage caused by an XFEL to polydimethylsiloxane (PDMS) and polyimide (PI), which are widely used as sample delivery materials in synchrotron X-rays. Upon XFEL exposure, the PDMS film produced irregularly shaped and sized holes, whereas the PI film produced relatively regular shaped and sized holes. When XFELs were exposed to the channel of the PDMS-based microfluidic device, holes were generated on the film by the radiation damage and the microfluidic device and the internal channel region were structurally destroyed. The PI-based microfluidic device experienced no structural destruction, except for the holes generated by the XFEL. However, as the XFELs were continuously exposed, bubbles generated from the solution due to radiation damage; the accumulation of these bubbles interfered with the path of the inner channel of the microfluidic device. Our results will not only help understand the phenomenon of radiation damage of PDMS and PI films by XFEL, but also provide insight into the directions to pursue in developing applications of PDMS and PI films in XFEL studies. [ABSTRACT FROM AUTHOR]

Ensuring the safety of a teleoperation system is crucial, and optimization-based control approaches are an effective solution to ensure that the robot satisfies the multiple safety constraints. However, the control input reshaping via optimization can make a system nonpassive. Therefore, this study proposes a new optimization method for ensuring both the safety and passivity of a teleoperation system by integrating it with the task scaling method. Additionally, the energy tank method is implemented to modulate the tradeoff between dissipativity and control performance. The experiments demonstrated that the proposed method ensures the safety and passivity of the teleoperated system for all robot configurations and any operator’s command inputs. [ABSTRACT FROM AUTHOR]

The Rao-Blackwellized particle filter (RBPF) and FastSLAM have two important limitations, which are the derivation of the Jacobian matrices and the linear approximations of nonlinear functions. These can make the filter inconsistent. Another challenge is to reduce the number of particles while maintaining the estimation accuracy. This paper provides a robust new algorithm based on the scaled unscented transformation called unscented FastSLAM (UFastSLAM). It overcomes the important drawbacks of the previous frameworks by directly using nonlinear relations. This approach improves the filter consistency and state estima. tion accuracy, and requires smaller number of particles than the FastSLAM approach. Simulation results in large-scale environments and experimental results with a benchmark dataset are presented, demonstrating the superiority of the UFastSLAM algorithm. Index Terms--FastSLAM, improved proposal distribution, Jacobian, linearization, Rao-Blackwellized particle filter (RBPF), scaled unscented transformation (SUT), simultaneous localization and mapping (SLAM), unscented Kalman filter (UKF), unscented particle filter (UPF).

This paper presents a quantitative comparison framework for bilateral teleoperation systems (BTSs) that have different dynamic characteristics and sensory configurations for a given task-dependent performance objective (TDPO). [micro]-synthesis is used to develop the framework since it can efficiently treat systems containing uncertainties and disturbances. The framework consists of: 1) a feasibility test and 2) a comparison methodology using prioritized TDPOs. As the formulation used is based on [micro]-synthesis, the system, operator, and environment models are represented in the form of linear nominal models with frequency-dependent multiplicative uncertainties. This framework is applied to a BTS including an uncertain human operator and environment in a practical case study. The validity of the proposed quantitative framework is confirmed through experiments. The proposed framework can be used as a tool to design BTSs, especially when there are constraints in designing drive mechanisms and choosing sensory configurations. Index Terms--Bilateral teleoperation system, haptic interface, quantitative comparison, [micro]-synthesis, task-dependent performance objective.

A hard contact is an impact that occurs when the robot contacts a stiff environment with a high velocity. In the pretransition phase of the hard contact, it is important to maintain stability while reducing succeeding force peaks and the duration time. For these purposes, we propose two control methods. One is a suppression controller that suppresses position rebounds in-between the impact time. The other is a flexible-damped joint with a joint damping controller The flexible-damped joint is a new joint type designed to increase the hardware damping. It is controlled by a novel controller, called the joint damping controller, to enhance damping. The major advantage of the proposed methods is a guaranteed stability. The performance of the proposed methods is validated via several comparative experiments. [DOI: 10.1115/1.2719766]

Numerical integration methods based on the Lie group theoretic geometrical approach are applied to articulated multibody systems with rigid body displacements, belonging to the special Euclidean group SE(3), as a part of generalized coordinates. Three Lie group integrators, the Crouch-Grossman method, commutator-free method, and Munthe-Kaas method, are formulated for the equations of motion of articulated multibody systems. The proposed methods provide singularity-free integration, unlike the Euler-angle method, while approximated solutions always evolve on the underlying manifold structure, unlike the quaternion method. In implementing the methods, the exact closed-form expression of the differential of the exponential map and its inverse on SE(3) are formulated in order to save computations for its approximation up to finite terms. Numerical simulation results validate and compare the methods by checking energy and momentum conservation at every integrated system state. Index Terms--Differential equations on Lie groups, multibody dynamics, numerical integration, special Euclidean group.

The PID trajectory tracking controller for Lagrangian systems shows performance limitation imposed by inverse dynamics according to desired trajectory. Since the equilibrium point cannot be defined for the control system involving performance limitation, we define newly the quasiequilibrium region as an alternative for equilibrium point. This analysis result of performance limitation can guide us the autotuning method for P1D controller. The quasiequilibrium region is used as the target performance of autotuning PID trajectory tracking controller. The autotuning law is derived from the direct adaptive control scheme, based on the extended disturbance input-to-state stability and the characteristics of performance limitation. Finally, experimental results show that the target performance can be achieved by the proposed automatic tuning method.

Based on the linear complementarity formulation of a unilaterally inextensible wire model, the behavior of motion and stability of wire-suspended dynamical systems is addressed in this paper. The concept of tension properness is developed to determine kinematical motion property, particularly the instantaneous degrees-of-freedom. Further, motion determinacy in spite of tension indeterminacy is proven. The notion of tension closure is described to help analyze the stability behavior of wire-suspended dynamical systems. By analyzing the maximal closure-domain of relative tension closure, one can assess the stability behavior of wire-suspended systems qualitatively as well as somewhat quantitatively. Some numerical examples and simulations will clarify and corroborate the theoretical results of this paper. Index Terms--Closure-domain, linear complementarity condition, tension-closure, wire-suspended dynamical systems.

There are many control methods to guarantee the robustness of a system. Among them, the disturbance observer (DOB) has been widely used because it is easy to apply and the cost is low due to its simplicity. Generally, an output signal of the system is required to construct a DOB, but for some systems such as magnetic/optical disk drive systems, we cannot measure the position output signal, but only the position error signal (PES). In order to apply a DOB to such systems, we must use an error signal instead of an output signal. We call it the error-based disturbance observer (EDOB) system. In this paper, we analyze the differences between a conventional DOB system and EDOB system, and show the effectiveness of the proposed EDOB through simulations and experiments. Also, this paper proposes criteria to enhance the robustness of an EDOB system, and reveals the disturbance rejection property of the EDOB system. Finally, we propose a new method of a double Q system to improve the track-following performance. This is also verified through experiments for a DVD 12x optical disk drive system. Index Terms--Digital signal processor (DSP), error-based disturbance observer (EDOB), normalized coprime factorization, optical disk drive (ODD) system, robustness, tracking servo.

A straightforward inverse kinematic algorithm for multilink flexible robots is proposed to improve the control performance. The inclusion of a dynamic constraint maximizes the performance of feedback controllers in high-speed applications. To obtain a numerically feasible solution, the singular perturbation approach is employed, which decomposes the inverse kinematics into an averaged part (slow part) and a parasitic part (fast part). The solution of the averaged part is considered the desired inverse kinematics, while the parasitic part is intentionally removed. The parameter expansion is carried out to obtain the solution sequentially. The implicit expansion method, which is a refined version of the expansion method, reduces computing time considerably. The formula in discrete time offers efficiency in computer applications. In addition, a requirement on differentiability of the desired task trajectory is derived. Index Terms--Flexible robots, inverse kinematics, singular perturbation, tracking control.

Disturbance-observer (DOB)-based controller design is one of the most popular methods in the field of motion control. In this paper, the generalized disturbance compensation framework, named the robust internal-loop compensator (RIC) is introduced and an advanced design method of a DOB is proposed based on the RIC. The mixed sensitivity optimization problem, which is the main issue of DOB design, is also solved through the parametrization of the DOB in the RIC framework. Differently from conventional methods, the Q-filter is separated from the mixed sensitivity optimization problem and a systematic design law for the DOB is proposed. This guarantees the robustness and optimality of the DOB and enables the design for unstable plants. Index Terms--Disturbance observer (DOB), mixed sensitivity optimization, motion control, robust internal-loop compensator.

Several 3-DOF pure translational parallel manipulators have been reported recently. However, kinematic conditions of such translational parallel manipulators have not been studied deeply. Most previously reported translational parallel manipulators were analyzed by considering constraints on the motion of an independent leg. In addition to the constraints of independent legs, the effect of the constraints on an overall mechanism are analyzed in this paper. The overall kinematic constraints are explained by introducing the restriction of motion, which is a constraint that prohibits a manipulator from moving in a certain region or direction, instantaneously. By introducing it, kinematic constraints can be embedded explicitly in the formulation of rate kinematics, and by analyzing it, constraints for a desired motion can be found. This paper derives constraints for pure translational motion in a systematic way. Necessary and sufficient conditions are suggested and several translational parallel manipulators with their kinematic features are provided.

One of the most important and widely used concepts in the kinematic analysis of robot manipulators is the reciprocal screw. However, there are no general expressions and easy methods to obtain the reciprocal screw in an analytic manner. This paper suggests an analytic formulation of the reciprocal screws of arbitrarily aligned screw systems. Since the reciprocal screws obtained in this paper are represented by the direction vectors and the position vectors of the given screws, we can analyze the relation between the reciprocal screw system and the given screw system easily. With the results, to find a reciprocal screw is to solve an algebraic equation of the corresponding system of screws. In order to show the usefulness of the result, several examples related to the robot manipulator are provided. For a nonredundant serial manipulator, the pseudo inverse of the Jacobian matrix is shown to be equivalent to the wrench matrix obtained by the reciprocity. For a parallel manipulator, a leg is isolated to obtain an independent part from the manipulator and is analyzed analytically. The proposed method can be applied to any arbitrarily aligned screw system. [DOI: 10.1115/1.1539508]

A combined observer is synthesized by unifying the conventional linear state estimator and the perturbation observer to estimate plant uncertainties and disturbances. It enables robust state estimation for uncertain dynamical systems and simultaneously, provides full-state to the perturbation observer under output feedback conditions. The proposed combined observer is very practical since it is given as a recursive discrete-time form with minimal tuning parameters, and it requires no knowledge of the plant uncertainty. A coupled estimation error dynamics is derived, and the related technical issues such as stability and noise sensitivity are addressed. The combined observer setting is also extended to stochastic systems, and the discrete Kalman filter is reformulated by including the perturbation estimate update process. Numerical examples and experimental results validate the proposed schemes. [DOI: 10.1115/1.1540112] Keywords: State Estimator, Discrete Kalman Filter, Perturbation Observer, Robustness

For joint tracking control of flexible robots, this paper presents a two-step design of controller: the bandwidth modulation with modal feedback approach. First, we focus on the design of rigid part's motion controller considering the bandwidth of the rigid subsystem. We investigate the relationship between macro joint tracking performance and vibration suppression capability using the bandwidth parameter. After adjusting the bandwidth of rigid motion, the composite control, which is the second step consisting of rigid and flexible sub-controllers, is applied like singular perturbation approach. As the flexible sub-controller, we propose a direct modal feedback controller that is very simple, but effective to suppress the vibration. The validity and effectiveness of the proposed method are verified by experiments using a POSTECH 3-D flexible robot. [DOI: 10.1115/1.1514240]