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Aminoacyl-tRNA synthetases (ARSs) have evolved to acquire various additional domains. These domains allow ARSs to communicate with other cellular proteins in order to promote non-translational functions. Vertebrate cytoplasmic isoleucyl-tRNA synthetases (IARS1s) have an uncharacterized unique domain, UNE-I. Here, we present the crystal structure of the chicken IARS1 UNE-I complexed with glutamyl-tRNA synthetase 1 (EARS1). UNE-I consists of tandem ubiquitin regulatory X (UBX) domains that interact with a distinct hairpin loop on EARS1 and protect its neighboring proteins in the multi-synthetase complex from degradation. Phosphomimetic mutation of the two serine residues in the hairpin loop releases IARS1 from the complex. IARS1 interacts with BRCA1 in the nucleus, regulates its stability by inhibiting ubiquitylation via the UBX domains, and controls DNA repair function.

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.

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.

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.

The disturbance observer (DOB) has been widely utilized for high-precision and high-speed motion control applications. In this note, we suggest the robustness measure of the DOB as a criterion to design the robust DOB systems. Also, we suggest its design guidelines especially for second-order systems. Experimental results for an optical disk drive system show the validity of design guidelines. Index Terms--Disturbance observer (DOB), optical disk drive (ODD) system, robustness measure.

This paper suggests an inverse optimal proportional-integral-derivative (PID) control design method to track trajectories in Lagrangian systems. The inverse optimal PID controller exists if and only if the Lagrangian system is extended disturbance input-to-state stable. First, we find the Lyapunov function and the control law that satisfy the extended disturbance input-to-state stability by using the characteristics of the Lagrangian system. The control law has a PID control form and satisfies the Hamilton-Jacobi-Isaacs equation. Hence, the [H.sub.[infinity]] inverse optimality of the closed-loop system dynamics is acquired through the PID controller if the conditions for the control law are satisfied. Also, simple coarse/fine performance tuning laws are suggested based on a performance limitation analysis of the inverse optimal PID controller. Selection conditions for gains are proposed as functions of the tuning variable. Experimental results for a typical Lagrangian system show that our analysis provides performance and [H.sub.[infinity]] optimality. Index Terms--[H.sub.[infinity]] optimality, ISS, performance, PID, tuning rule.

As a redundancy resolution method, the conventional extended Jacobian method (EJM) has two problems: One is the algorithmic singularity, and the second is nonexistence of a sufficient condition. Their impact on the inverse kinematic performances are exemplified. To remedy the related problems, we propose the notion of solution characteristics. It is based on an analytic sufficient condition for the EJM. This serves to confirm the right direction of optimization in the EJM and to characterize the algorithmic singularity problem. The above local characterization of an optimal solution by solution characteristics is globally extended by the invariance of the solution characteristics of the EJM. Specifically the characteristic of a solution with the EJM is invariant before crossing an algorithmic singularity. The ideas in this article also have practical implications since the EJM can now be fully analyzed with the theoretical results. To demonstrate its exactness and usefulness, planar three degrees of freedom (DOF) and spatial 4-DOF regional redundant manipulators are analyzed using the proposed solution characteristics.

Recent success in nonlinear [H.sub.[infinity]] control design is applied to the control of Euler--Lagrange systems. It is known that the existence of [H.sub.[infinity]] optimal control depends on solvability of the so-called Hamilton-Jacobi-Isaccs (HJI) partial differential equation, In this article, the associated HJI equation for nonlinear [H.sub.[infinity]] inverse-optimal control problem for Euler--Lagrangian system is solved analytically. The resulting control is referred to as the reference error feedback, which takes conventional PID controller form. Consequently, robust motion control can be designed for robot manipulators using [L.sub.2]-gain attenuation from exogenous disturbance and parametric error. Index Terms--Euler--Lagrange system, nonlinear [H.sub.[infinity]] inverse-optimal control, nonlinear [L.sub.2]-gain attenuation, reference error feedback (REF), reference motion compensation.

Robust time optimal control algorithm based on internal loop compensator is proposed. Internal loop compensator effectively isolates hard disk system from the uncertain disturbances including modeling error, external disturbance, shock, and control torque saturation. We use the [H.sub.[infinity]] mixed sensitivity method for the optimization of internal loop compensator and proximate time optimal controller as a feedback controller to provide a time optimal property. The performance of the proposed controller is verified via simulation works. Index Terms--Hard disk drive, internal loop compensator, [H.sub.[infinity]] mixed sensitivity method, time optimal control.

Surface electromyography (sEMG) signals reflect muscle contraction and hence, can provide information regarding a user's movement intention. High-density sEMG systems have been proposed to measure muscle activity in small areas and to estimate complex motion using spatial patterns. However, conventional systems based on wet electrodes have several limitations. For example, the electrolyte enclosed in wet electrodes restricts spatial resolution, and these conventional bulky systems limit natural movements. In this paper, a microneedle-based high-density electrode array on a circuit integrated flexible substrate for sEMG is proposed. Microneedles allow for high spatial resolution without requiring conductive substances, and flexible substrates guarantee stable skin-electrode contact. Moreover, a compact signal processing system is integrated with the electrode array. Therefore, sEMG measurements are comfortable to the user and do not interfere with the movement. The system performance was demonstrated by testing its operation and estimating motion using a Gaussian mixture model-based, simplified 2D spatial pattern. [ABSTRACT FROM AUTHOR]