Slider Positions Research Articles

The modeling and cascade sliding mode control of a moving mass-actuated coaxial dual-rotor UAV

In this study, an attitude control scheme based on a three-track moving mass control mechanism is proposed to address the problems of the overcomplicated rotor components, low service life, and low reliability of coaxial dual-rotor unmanned air vehicles (UAV). The motion and aerodynamic models of a moving mass-actuated ducted coaxial dual-rotor UAV are derived. The rotational dynamic characteristics of a moving mass-actuated UAV (MAUAV) with different slider positions and mass ratios are analyzed. An attitude controller based on backstepping sliding mode control is designed to address the nonlinearity and uncertainty of the MAUAV rotation. Based on this, we developed a position controller using cascade sliding mode control. The simulation results demonstrate that the designed attitude controller can achieve a settling time of 1.438 s in the unit-step response and a steady-state error of less than 5% in the sinusoidal attitude-tracking experiment. Additionally, the designed position controller exhibited a better trajectory-tracking effect under different levels of gust disturbance than that of a linear quadratic regulator control-based position controller.

Promoting Music Exploration through Personalized Nudging in a Genre Exploration Recommender

Recommender systems are efficient at predicting users’ current preferences, but how users’ preferences develop over time is still under-explored. In this work, we study the development of users’ musical preferences. Exploring musical preference consistency between short-term and long-term preferences in data from earlier studies, we find that users with higher musical expertise have more consistent preferences for their top-listened artists and tags than those with lower musical expertise, while high expertise users also show more diverse listening behavior. Users typically chose to explore genres that were close to their current preferences, and this effect was stronger for expert users. Based on these findings, we conducted a user study on genre exploration to investigate (1) whether it is possible to nudge users to explore more distant genres, (2) how users’ exploration behavior within a genre is influenced by default recommendation settings that balance personalization with genre representativeness in different ways, and (3) how nudging for exploration increases the perceived helpfulness of recommendations for users to explore. Our results show that users were more likely to select the more distant genres if these genres were nudged by presented at the top of the list, however, users with high musical expertise were less likely to do so. We also find that the more representative default slider, which by default recommended more genre-representative tracks, made users set the slider at a less personalized level. The more representative slider position alone did not promote more exploration of users’ current preferences but when combined with the nudge for distant genres, the more representative slider positions effectively nudged users to explore. Nudging to explore does not necessarily lead to an increase in perceived helpfulness. On the one hand, nudging for exploration improves the perceived helpfulness for exploration by making users explore away from their current preferences. On the other hand, it reduces helpfulness due to lower perceived personalization as users move away from their personalized recommendations. To improve perceived helpfulness, it seems necessary to provide a balanced trade-off between exploration and personalization.

Time-domain numerical continuation of periodic orbits for harmonically forced hysteretic nonlinear systems with Iwan joints

Coulomb sliders are used widely in order to model frictional interfaces. In many applications, the nonlinear Frequency Response Functions (FRFs) of these systems is desired, but it is extremely computationally expensive to use time-domain integration methods to compute the steady-state response. The nonlinear force and stiffness of these devices depends on the position of sliders, and the implicit nature of the slider positions makes these systems hysteretic and therefore non-trivial to address using conventional continuation methods. This paper proposes a novel numerical method, dubbed ”Hysteresis Identification via Reversal Points or (HIRP)” that can compute the steady-state harmonically forced response of frictional nonlinear systems. For this purpose, a quasi-static algorithm is introduced which can evaluate the state of sliders at any time based on the reversal points over a period. This reduces the number of state variables needed in the continuation routine by at least an order of magnitude. The method has been tested by computing the harmonic response of a hysteretic system with multiple Coulomb sliders. The method is evaluated on multi-degree of freedom systems with Iwan joints, demonstrating that the method can be a valuable tool for predicting the nonlinear, steady-state response of hysteretic systems.

Tethered Tool Manipulation Planning With Cable Maneuvering

In this letter, we present a planner for manipulating tethered tools using dual-armed robots. The planner generates robot motion sequences to maneuver a tool and its cable while avoiding robot-cable entanglements. Firstly, the planner generates an object manipulation motion sequence (OMMS) to handle the tool and place it in desired poses. Secondly, the planner examines the tool movement associated with the OMMS and computes candidate positions for a cable slider, to maneuver the tool cable and avoid collisions. Finally, the planner determines the optimal slider positions to avoid entanglements and generates a cable manipulation motion sequence (CMMS) to place the slider in these positions. The robot executes both the OMMS and CMMS to handle the tool and its cable to avoid entanglements and excess cable bending. Simulations and real-world experiments help validate the proposed method.

Simple and Low-Cost Readout Circuit for Differential Resistive Sensors

In this paper, a simple and low-cost readout circuit for differential resistive sensors is presented. The realization method is based on the relaxation oscillation technique, which utilizes the operational amplifiers (op-amps) with a single supply voltage. The oscillating output Duty-Cycle is proportional to the difference of two sensing resistances. In comparison with the traditional voltage divider circuit or the Wheatstone bridge circuit or the previously reported readout circuit based on CCIIs, the proposed circuit can be interfaced with microcontroller without using an analog-to-digital converter. Theoretical predictions are supported by the PSPICE simulation results and the experimental data. In applying a slide potentiometer with changes of slider positions of ±15 mm, it is found that the maximum error of the proposed circuit is approximately -2.90% of full-scale

Inverse dynamics of a 3-DOF translational parallel kinematic machine

In this paper, kinematics and dynamics modeling of a typical 3-Degree of freedom (DOF) translational Parallel kinematic machine (PKM) is carried out. The kinematic structure of PKM consists of three limbs, connecting the base and the tool platform. Each limb consists of an arm and a forearm with joints Prismatic-revolute-revolute-revolute (PRRR). The arrangement of joints are in such a way that the tool platform will have pure translational motion along the Cartesian axes. Inverse kinematic relations that are necessary to find the slider positions and joint angles for a given position of tool platform are derived. The dynamics model is then derived based on Natural orhogonal complement (NOC). The inverse dynamics equations presented are used to compute actuator forces. The actuator forces using NOC are validated with those obtained based on Lagrangian method. The effect of slider, arm, and forearm inertia on the actuator forces is studied to know whether to neglect the arm and forearm inertias while computing the actuator forces for PKM. Finally, an attempt is made to find the optimal location of a circular trajectory using Genetic algorithms (GA) with minimization of Grand total actuator force (GTAF) as objective function.

C6 ステレオ視法と高精度変位計を統合した高精度鏡面誤差評価方法に関する研究(膜構造(2))

In this study, a system for high-accuracy measurement of surface error properties is developed and investigated. In the system, a photogrammetric measurement system such as a stereo-vision is mounted on a slider and its movement is precisely measured by high accuracy displacement sensors such as laser displacement sensors. Deformations of a target object are measured repeatedly using the photogrammetric measurement at different slider positions. Correction methods of the measurement errors used it the developed system are derived. Some experiments are carried out and the efficiency of the system is demonstrated.

Hands-On Parameter Search for Neural Simulations by a MIDI-Controller

Computational neuroscientists frequently encounter the challenge of parameter fitting – exploring a usually high dimensional variable space to find a parameter set that reproduces an experimental data set. One common approach is using automated search algorithms such as gradient descent or genetic algorithms. However, these approaches suffer several shortcomings related to their lack of understanding the underlying question, such as defining a suitable error function or getting stuck in local minima. Another widespread approach is manual parameter fitting using a keyboard or a mouse, evaluating different parameter sets following the users intuition. However, this process is often cumbersome and time-intensive. Here, we present a new method for manual parameter fitting. A MIDI controller provides input to the simulation software, where model parameters are then tuned according to the knob and slider positions on the device. The model is immediately updated on every parameter change, continuously plotting the latest results. Given reasonably short simulation times of less than one second, we find this method to be highly efficient in quickly determining good parameter sets. Our approach bears a close resemblance to tuning the sound of an analog synthesizer, giving the user a very good intuition of the problem at hand, such as immediate feedback if and how results are affected by specific parameter changes. In addition to be used in research, our approach should be an ideal teaching tool, allowing students to interactively explore complex models such as Hodgkin-Huxley or dynamical systems.

Geometric design of slider-crank mechanisms for desirable slider positions and velocities

In problems requiring uniform cutting speeds uniform flow rates etc. slider-crank mechanisms provide economical solutions. Thus, the problem of designing slider-crank mechanisms for desirable slider positions and velocities is handled within a geometric framework in this paper. Here, the rotation of the crank has been related to the translation of the slider through a linear function. A unified methodology comprising the so-called Subdomain, Galerkin methods together with the classical collocation method is implemented to find the values of the parameters involved. The effectiveness of the methodology has been demonstrated on numerical examples. Since more than one solution results from the solution process, it is always possible to form multi-loop mechanisms. Moreover, designs with low velocity errors in the forward stroke exhibit similar feature in the backward stroke too.

Accelerated molecular dynamics simulation of low-velocity frictional sliding

Accelerated molecular dynamics (MD) simulations are implemented to model the sliding process of atomic force microscope (AFM) experiments and to lower the sliding speeds below those in a conventional MD simulation. In this study the hyperdynamics method, originally devised to extend MD time scales for non-driven systems, is applied to the frictional sliding system. This technique is combined with a parallel algorithm that simultaneously simulates the system over a range of slider positions so that the overall acceleration rate is approximately the number of processors multiplied by the boost factor from the hyperdynamics method. The new methodologies are tested using two-dimensional and three-dimensional Lennard-Jones AFM models. Direct comparison with the results from conventional MD shows close agreement validating the methods. The acceleration rate achieved in this study is four orders of magnitude in 2D and three orders of magnitude in 3D.

Atomic-scale simulations on the sliding of incommensurate surfaces: The breakdown of superlubricity

Molecular dynamics simulations of frictional sliding in an atomic force microscope (AFM) show a clear dependence of superlubricity between incommensurate surfaces on tip compliance and applied normal force. While the kinetic friction vanishes for rigid tips and low normal force, superlubric behavior breaks down for softer tips and high normal force. The simulations provide evidence that the Frenkel-Kontorova-Tomlinson (FKT) scaling applies equally to a more realistic three-dimensional (3D) incommensurate AFM model except in the limit of very low stiffness and high normal load. Unlike the FKT model in which the breakdown of superlubricity coincides with the emergence of the metastable states, in the 3D model some metastable states appear to reduce frictional force leading to nonmonotonic dependence of force on normal load and tip compliance. Metastable states vary with the slider positions and the relative stabilities of these metastable states result in varying transition mechanisms depending on sliding velocity.

Shock response analysis of hard disk drive using flexible multibody dynamics formulation

Recent development of the shock analysis on the HDD is briefly reviewed. A flexible multi-body dynamics formulation is developed to simulate the shock response of the HDD. If one component in the HDD is changed, only mode shapes and frequencies of that component should be re-calculated and then used to obtain the system’s response. Steady state Reynolds equation is solved to obtain the air pressure on the slider and disk for various slider positions. An air pressure table is formed and used to model the non-linear air bearing during the simulation. Responses of flying height for different direction and shock duration time are analyzed. Results show that the flying state of the slider is more sensitive to the shock with shorter duration time.

Dynamics of air bearing sliders

In this paper we present new results for the dynamics of a problem for the interaction of a compressible gas flow with a movable rigid surface. Compressible lubrication theory is applied to describe the dynamics of the vertical motion of air bearing sliders used in computer hard disk drives. In the limit of large bearing number we show this problem can be reduced to a nonlinear integrodifferential equation. Linear stability analysis and perturbation methods show that over the range of possible slider positions there is an infinite sequence of Hopf bifurcations yielding stable large amplitude periodic orbits. The dynamics of near-crash behavior and interaction with a moving disk surface are also addressed.

NeXT in the psychology laboratory: An example of an auditory pattern tracking task

The NeXT computer system is a relatively new, inexpensive, 68040-based computer with high computational power, storage, graphics, audio, and other capabilities. The present article examines the effectiveness of the NeXT for studies of auditory sequential memory. In these studies, subjects track the time of occurrence of a sequence of tones, using a mouse that controls the position of sliders represented on the computer screen interface. This interface allows the subject to represent the different sounds on the y-axis and the time of their occurrence on the x-axis. The computer produces random orders of stimulus sequences, provides feedback, and stores and transforms accuracy and response time data from the slider positions for subsequent analysis. A tutorial for the development of this interface and its variations is provided. As well, procedures for programming the experiment and the operation of the interface are described, accompanied by a frank account of issues surrounding development and management. It is concluded that high-quality sound and ease of both graphics interface design and program modification make NeXT an attractive option for research on auditory sequential order, promising much for further applications as well. Successful use of the NeXT, however, demands much from technical personnel for both programming and system management.

Receiver-Operating Characteristics Determined by a Mechanical Analog to the Rating Scale

In one portion of a fixed-interval-observation experiment, observers indicated their certainty that a 500-cps signal had been presented in a thermal-noise background by positioning a slider after each interval. In a second portion of this experiment, the observers responded by making binary decisions. Slider positions were treated as typical confidence ratings; the conditional probability of a given rating or of one indicating greater confidence, given signal plus noise, was plotted against the probability of these ratings, given noise alone. Functions produced in this manner, for a rating scale divided into thirty-six positions, were fit closely by the receiver-operating characteristics (ROC's) of the theory of signal detectability. A psychophysical model using two straight-line segments did not provide a good approximation to these data. Values of d′ were generally lower for the rating procedure than for the binary-decision procedure. The use of a large number of rating categories did not result in large increases information transmitted by the observers, but it did provide the desired fine resolution of the ROC's.