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This work presents a strategy to improve the control of robot manipulators actuated by servomotors controlled in position. The improvement consisted on using artificial vision in order to implement a second control loop that guarantees the joint position tracking of the desired values. The visual feedback algorithm is robust upon rotations and translations of the camera, which is its main advantage against other similar approaches reported in the literature. The proposed technique was tested on a 3 DOF robot with position actuators, to which different desired joint positions were commanded and regulated through a PID controller. The experiments were performed with different rotation angles of the camera, obtaining successful results by reducing the joint position errors with respect to the position regulation without visual feedback. [ABSTRACT FROM AUTHOR]

To achieve accurate position tracking, there is a need to develop high-fidelity robot arm models that are compliant and affordable. However, physics-based models are constrained by their stiffness and complexity. Therefore, reduced-order modelling developed from data through sub-space system identification is proposed as a solution to this problem. A high-fidelity simulation model of a two-link robot arm developed in MATLAB and Simulink was used to generate synthetic data, and the data acquired was used for the estimation and validation of first- and second-order linear state-space models. Due to its effective tracking characteristics, the model predictive control technique was used for trajectory tracking. The results of the simulations demonstrate that the first-order and second-order models can track the intended set points accurately but at the cost of larger joint torques required to counteract gravity. The results show that low-order and data-compliant models can follow trajectories with high precision. MATLAB 2020a was used for all simulations. [ABSTRACT FROM AUTHOR]

Bilateral teleoperation systems are widely used to compensate for image spin and in many other applications. Good transparency (position tracking and force feedback) is an important performance index in the control design of bilateral teleoperation systems. This study aims to achieve good transparency for teleoperation systems using force sensorless by proposing an alternative to direct force measurement. Our proposed method is a finite‐time adaptive sliding‐mode‐assisted disturbance observer, which combines disturbance observer with adaptive sliding mode control. The finite‐time stability of adaptive sliding‐mode‐assisted disturbance observer is analysed using the Lyapunov theory. Moreover, a bilateral control law based on adaptive sliding‐mode‐assisted disturbance observer is designed. The proposed method not only improves the system transparency with both force feedback and position tracking, but is also chatter‐free. Experiments are conducted using bilateral brushless DC motors in an experimental setup to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In order to improve the position tracking precision of dual permanent magnet synchronous motor (PMSM) systems, a unified nonlinear predictive control (UNPC) strategy based on the unified modeling of two PMSM systems is proposed in this paper. Firstly, establishing a unified nonlinear model of the dual-PMSM system, which contains uncertain disturbances caused by parameters mismatch and external load changes. Then, the position contour error and tracking errors are regarded as the performance index inserted into the cost function, and the single-loop controller is obtained by optimizing the cost function. Meanwhile, the nonlinear disturbance observer is designed to estimate the uncertain disturbances, which is used for feed-forward compensation control. Finally, the proposed strategy is experimentally validated on two 2.3 kW permanent magnet synchronous motors, and the experimental results show that effectiveness and feasibility of proposed strategy. [ABSTRACT FROM AUTHOR]

The presented work was directed to develop the dynamic performance of an electro-hydraulic proportional system (EHPS). A mathematical model of the EHPS is presented using electro- hydraulic proportional valve (EHPV) by Matlab-Simulink, which facilitates the simulation of the hydraulic behavior inside the main control unit. Experimental work is done and the closed loop system is designed using the linear variable displacement transducer sensor (LVDT). The controller of the system is an Arduino uno, which is considered as a processor of the system. The model is validated by the experimental system. The study also presents a real time tracking control method, based on pulse width modulation, by controlling the speed of the actuator to achieve the position tracking with minimum error and low transient time, by applying the constant input signal 50 mm the transient time was 0.9 seconds and the error 1.8 %. [ABSTRACT FROM AUTHOR]

Decision-makers in soccer routinely assess the tactical behaviour of a team and its opponents both during and after the game to optimize performance. Currently, this assessment is typically driven by notational analysis and observation. Therefore, potential high-impact decisions are often made based on limited or even biased information. With the current study, we aimed to quantitatively assess tactical performance by abstracting a set of spatiotemporal features from the general offensive principles of play in soccer using position tracking data, and to train a machine learning classifier to predict match outcome based on these features computed over the full game as well as only parts of the game. Based on the results of these analyses, we describe a proof of concept of a decision support system for coaches and managers. In an analysis of 302 professional Dutch Eredivisie matches, we were able to train a Linear Discriminant Analysis model to predict match outcome with fair to good (74.1%) accuracy with features computed over the full match, and 67.9% accuracy with features computed over only 1/4th of the match. We therefore conclude that using only position tracking data, we can provide valuable feedback to coaches about how their team is executing the various principles of play, and how these principles are contributing to overall performance. [ABSTRACT FROM AUTHOR]

The steady-state operation and controlled position tracking in ball balancer applications are largely affected due to their nonlinear and underactuated behavior. To overcome these drawbacks, this paper develops a wavelet-based fuzzy controller which operates in closed loop with the system by measuring the ball position and the plate angle. The proposed approach adapts discrete wavelet transform for denoising the error signal and tuning the weights of the fuzzy controller. To test the effectiveness of the proposed approach, numerical simulations are performed by modeling a two degree of freedom ball balancer system. The eminence of the controller is assessed by comparing its operation on the modeled system with conventional fuzzy logic controller and by calculating the root mean square error, and time response analysis. The results showed a steady and precise response of the proposed approach to the framework of positioning ball on the plate. [ABSTRACT FROM AUTHOR]

Position tracking has been widely used in medical applications, especially in 3D ultrasound imaging, where it has transformed the 2D slice limitation into 3D volume with bigger clinical impacts. As a game controller can also produce position tracking information, it has the potential to act as a low-cost and portable position tracker for ultrasound probes. This paper aims to investigate the feasibility of a game controller to perform as a position tracker and to design its implementation in 3D ultrasound imaging. The study consists of data acquisition and 3D ultrasound reconstruction for visualization. The data acquisition is accomplished by capturing the 2D ultrasound frame and its relative positional and orientation data by using an ultrasound probe and game controller respectively. These data are further reconstructed to produce 3D ultrasound volume for visualization. Our experiments include game controller position tracker testing and 3D ultrasound reconstruction on baby phantom. The results have confirmed that the game controller performance was closely aligned with that of in a robot arm. Also, the 3D ultrasound reconstruction implementation has revealed promising outcomes. With these features, the function of the currently available ultrasound probes can be prospectively improved using a game controller position tracker effectively. Graphical Abstract. [ABSTRACT FROM AUTHOR]

Altered afferent input from the neck due to fatigue alters upper limb proprioception and is likely to impact upper limb performance accuracy. This study examined the effect of cervical extensor muscle (CEM) fatigue on eye-hand tracking accuracy in healthy participants. Twenty-four healthy right-handed individuals were randomly assigned to either a control or CEM fatigue group. Each participant performed a tracking task which required shoulder rotation to move a circular object to a square target on a touchscreen computer. The task was performed with vision of the target and with the target hidden. A prone lying position, CEM fatigue protocol required participants to hold a 2 kg weight against gravity with their head in a neutral posture. The control intervention rested for 5 min, in a prone position, with the head supported in a neutral posture. Participants performed 3 trials with vision and 3 without at 5 different time points: (1) pre-intervention (fatigue or control), (2) immediately post-intervention, (3) 5 min, (4) 10 min, and (5) 20 min post-intervention. There were significant differences between the target with vision and the hidden condition for both groups between pre- and post-fatigue trials in angle of trajectory (p = 0.0001), and distance from release point to the target (p = 0.0001). Significant differences occurred in the hidden target condition for the fatigue group immediately post fatigue (p = 0.018) for distance from release to the target. Neck muscle fatigue reduced the accuracy of an upper limb tracking task to a hidden target, suggesting that altered afferent input from the neck due to fatigue may impair body schema and result in decreased upper limb performance accuracy. [ABSTRACT FROM AUTHOR]

Highlights • A passivity-based control method for delayed coupled network systems is proposed. • Conservatism is reduced by considering the energy reflection of a 2-port network. • The 2-port's energy output is distributed considering an ideal energy storage. • An experimental comparison study with a state-of-the-art approach is presented. • The new method is superior considering position error and transmitted impedances. Abstract The Time Domain Passivity Approach (TDPA), a method to inject adaptive damping to satisfy the passivity condition in real-time, has emerged as a powerful tool to stabilize coupled network systems with/without communication delay, such as haptic and teleoperation systems, due to its simplicity and effectiveness. However, we found that the conventional TDPA has unnecessary conservatism especially in delayed coupled network systems due to direction dependent energy calculation and dissipation. In this paper, we propose a new time domain passivity approach with reduced conservatism by considering the energy reflection from an energy storage element in the network. The method is generally formulated with a delayed 2-port network system including an energy storage element and implemented to a teleoperation system. The proposed method is experimentally tested and a comparison with the conventional TDPA reveals improved kinesthetic coupling and transparency in terms of position tracking and force reflection. [ABSTRACT FROM AUTHOR]

Accurate position control of an electro hydraulic servo system (EHSS) is a challenging task due to inherent system nonlinearities, parametric variations and un-modelled dynamics. Since feedback controllers alone cannot provide perfect tracking control, an integration of feedback and feed forward controller is required. A cascaded iterative learning control (ILC) technique for position control of EHSS is proposed in this paper. ILC is a feed forward controller which modifies the reference signal for a feedback fractional order proportional-integral-derivative (PID) controller by learning through current control input and previous error obtained through trails. Unlike other feed forward controllers, ILC works on signal instead of system which eliminates the need of complete knowledge of the system. As compared to other controllers, the proposed technique provides fast convergence without the need of reconfiguring the existing control loop. Simulation and experiments revealed the effectiveness of the proposed technique for EHSS. The obtained results indicated eight percent improvement in rise time and nearly twenty one percent improvement in the settling time. [ABSTRACT FROM AUTHOR]

Summary: This paper considers the adaptive sliding‐mode control (ASMC) problem of spacecraft relative position tracking with maneuvering target in the presence of external disturbance and unknown mass property. Integrated with the spacecraft absolute orbit dynamics, the line‐of‐sight–based relative position motion model is established; further, the problem is formulated in the general mechanical second‐order form with unknown mass parameter and matching disturbance, which makes it convenient to use some useful physical properties in the control law design. As a stepping‐stone, the traditional ASMC law is proposed without prior knowledge of uncertainty/disturbance bound. Then, incorporated with the smooth‐projection algorithm and equivalent‐control‐dependent gain method, the modified control law is proposed, which can force the mass estimate to remain in a desired domain and efficiently overcome the drawback of the overestimation of the disturbance in the traditional ASMC law. Within the Lyapunov frame, the bounded stability is presented in the real case that the sign function is replaced by the hyperbolic tangent function. Finally, three different simulation cases are presented to show fine performance of the modified ASMC law. [ABSTRACT FROM AUTHOR]

Abstract Helicopters are highly nonlinear and internally unstable air vehicles, the dynamic response of which can be strongly influenced by flight conditions (wind gust, ground effect, etc.). Therefore, it is a challenging task to design a reliable flight control system (FCS) with all safety and performance requirements satisfied. This paper investigates the robust position tracking problem of a helicopter in ground effect (IGE). Based on a highly reliable and computational efficient finite state representation of rotor flow field IGE, a novel nonlinear disturbance observer-based incremental backstepping (NDOIBS) controller is designed to track position commands (all derivatives of the reference trajectory are known) under the influence of system uncertainties and external disturbances. Without requiring the exact knowledge of helicopter dynamics, the NDOIBS approach guarantees that instant control increments are derived in terms of Lyapunov theory and ensures robustness in the presence of mismatched disturbances whose first derivatives are bounded. It is shown that all state variables of the closed-loop system are semi-globally uniformly ultimately bounded (SGUUB). In addition, to further improve the horizontal position tracking performance, rotor state feedback (RSF) technique and a disturbance feedback strategy are applied to develop a pitch stability augmentation system (SAS). Finally, controller performance is demonstrated through numerical simulations using the Bo-105 utility helicopter. With the efficiency and robustness properties verified, the suggested NDOIBS control scheme shows great potential for implementing advanced FCS designs in existing helicopters. [ABSTRACT FROM AUTHOR]

This paper proposes a novel bilateral adaptive control scheme to achieve position and force coordination performance of underwater manipulator teleoperation system under model uncertainty and external disturbance. A new nonlinear model reference adaptive impedance controller with bound-gain-forgetting (BGF) composite adaptive law is designed for the master manipulator force tracking of the slave manipulator. The reference position in task space is obtained from the linear second-order impedance model whose input is the force error of the master and the slave. The adaptive terminal sliding mode control based on adaptive uncertainty compensation is proposed to achieve the master position tracking of the reference position. The radial basis function neural network (RBFNN) local approximation method is proposed for the slave manipulator's position tracking. The RBFNN based on Ge-Lee (GL) matrix is adopted to directly approximate each element of the slave manipulator dynamic, and the robust term with a proper update law is designed to suppress the error between the estimate model and the real model, and the external disturbance. The asymptotic tracking performance and global stability of the teleoperation system are proved with Lyapunov stability theorem. The simulation and experiment verify the performance of the proposed controller in teleoperation manipulator model. The results show that the teleoperation system has a good ability of position and force coordination. [ABSTRACT FROM AUTHOR]

A novel Fuzzy PID-Variable Structure Adaptive Control is proposed for position tracking of Permanent Magnet Synchronous Motor which will be used in electric extremity exoskeleton robot. This novel control method introduces sliding mode variable structure control on the basis of traditional PID control. The variable structure term is designed according to the sliding mode surface which is designed by system state equation, so it could compensate for the disturbance and uncertainty. Considering the chattering of sliding mode system, the fuzzy inference method is adopted to adjust the parameters of PID adaptively in real time online, which can attenuate chattering and improve control precision and dynamic performance of system correspondingly. In addition, compared with the traditional sliding mode control, this method takes the fuzzy PID control item to replace the equivalent control item of sliding mode variable structure control, which could avoid the control performance reduction resulted from modeling error and parameter error of system. It is proved that this algorithm can converge to the sliding surface and guarantee the stability of system by Lyapunov function. Simulation results show that Fuzzy PID-Variable Structure Adaptive Control enjoys better control precision and dynamic performance compared with traditional control method, and it improves the robustness of system significantly. Finally, the effectiveness and practicability of the algorithm are verified by the method of Rapid Control Prototyping on the semiphysical simulation test bench. [ABSTRACT FROM AUTHOR]

In this brief, the exponential rotor position tracking/regulation problem for position-sensorless (nonsalient-pole surface) PMSMs with unknown constant load torque and stator resistance is addressed. The requirement of persistency of excitation conditions involving a non-definitely zero rotor speed reference is removed, owing to the design of an innovative (speed measurement-based) adaptive observer that relies on a local version of the persistency of excitation lemma and does not involve straightforward adaptations of previous ideas. [ABSTRACT FROM AUTHOR]

The line-of-sight (LOS) kinematics and dynamics of a mirror-stabilized platform are derived using the virtual mass stabilization method. Accounting for the coupled and nonlinear kinematics and dynamics, the uncertainty of external disturbances, and the actuator input saturation in the mirror-stabilized platform, a modified adaptive robust control (ARC) scheme is proposed based on the command filtered method and the extended state observer (ESO). The command-filtered approach is used to ensure the stability and tracking performance of the adaptive control system under the input saturation. In the proposed scheme, the ESO is designed to observe the modeling error and unknown external disturbances. The stability of the control system is proved using the Lyapunov method. Simulation results and experimental results proved that the proposed control scheme can effectively reduce the occurrence of input saturation, attenuate the effect of unknown disturbances, and improve the position tracking accuracy. [ABSTRACT FROM AUTHOR]

The position tracking control problem of a hydraulic manipulator system is investigated. By utilizing homogeneity theory, a finite-time output feedback controller is designed. Firstly, a finite-time state feedback controller is developed based on homogeneity theory. Secondly, a nonlinear state observer is designed to estimate the manipulator’s velocity. A rigorous analysis process is presented to demonstrate the observer’s finite-time stability. Finally, the corresponding output feedback tracking controller is derived, which stabilizes the tracking error system in finite time. Simulations demonstrate the effectiveness of the designed finite-time output feedback controller. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of a model-based feedback controller to realize high versatility of fully actuated planar bipedal robotic walking. To conveniently define both symmetric and asymmetric walking patterns, we propose to use the left and the right legs for gait characterization. In addition to walking pattern tracking error, a biped's position tracking error in Cartesian space is included in the output function in order to enable high-level task planning and control such as multi-agent coordination. A feedback controller based on input-output linearization and proportional-derivative control is then synthesized to realize exponential tracking of the desired walking pattern as well as the desired global position trajectory. Sufficient stability conditions of the hybrid time-varying closed-loop system are developed based on the construction of multiple Lyapunov functions. In motion planning, a new method of walking pattern design is introduced, which decouples the planning of global motion and walking pattern. Finally, simulation results on a fully actuated planar biped show the effectiveness of the proposed walking strategy. [ABSTRACT FROM AUTHOR]

This paper presents a new position sensorless scheme in which a smoothing filter algorithm is proposed to improve the results obtained through Extended Kalman Filter (EKF) algorithm in tracking the rotor position for sensorless control of brushless DC motors. The rotor position and speed are estimated from the input voltage and current using the Extended Kalman Filter. States obtained through filtering in each sampling instant are refined, using the new smoothing algorithm, giving much better results. In the proposed method, the estimated state in previous instant is enhanced using the present measurement sample by the smoothing algorithm which is then used to improve the present estimated state variables. The complete system is modelled and simulated in MATLAB to verify the merit of the proposed smoothing algorithm. A comparison with conventional EKF is done for various load torque and speed conditions to establish the performance of the new sensorless algorithm. Simulation results show that the proposed smoothing technique offers better estimation accuracy. The peak error in the estimated speed and rotor position is considerably reduced when compared with EKF. The improved state estimate can be used as feedback for speed control of brushless DC motors in variable speed drives. [ABSTRACT FROM AUTHOR]

Optical beam position on a detector array is an important parameter for optimal symbol detection in a free-space optical communication system; hence it is essential to accurately estimate and track the beam position (which is unknown and may be varying in time). In this paper, we have attempted to solve the beam position tracking problem by setting it up as a state space variable filtering problem in the context of a dynamical system. We propose the following filtering methods for tracking the beam position: a Kalman filter and a particle filter that both use the maximum likelihood estimate of stationary beam position as a measurement in a linear dynamical model setting, and another particle filter which employs the received photon counts as observations for the nonlinear dynamical model. We compare the performance of these three filters in terms of mean-square error assuming that the beam position evolves in time according to a specified model. It is concluded from simulation results that the Kalman filter gives close to optimal performance for high to moderate photon rates for the Gauss–Markov evolution model. However, both the particle filtering algorithms outperform the Kalman filter for the uniformly distributed evolution noise scenario. [ABSTRACT FROM PUBLISHER]

This paper examines an observer-based backstepping terminal sliding mode controller (BTSMC) for 3 degrees of freedom overhead transmission line de-icing robot manipulator (OTDIRM). The control law for tracking of the OTDIRM is formulated by the combination of BTSMC and neural network (NN) based approximation. For the precise trajectory tracking performance and enhanced disturbance rejection, NN-based adaptive observer backstepping terminal sliding mode control (NNAOBTSMC) is developed. To obviate local minima problem, the weights of both NN observer and NN approximator are adjusted off-line using particle swarm optimization. The radial basis function neural network-based observer is used to estimate tracking position and velocity vectors of the OTDIRM. The stability of the proposed control methods is verified with the Lyapunov stability theorem. Finally, the robustness of the proposed NNAOBTSMC is checked against input disturbances and uncertainties. [ABSTRACT FROM AUTHOR]

The spacecraft pose tracking control problem for an uncertain pursuer approaching to a space target is researched in this paper. After modeling the nonlinearly coupled dynamics for relative translational and rotational motions between two spacecraft, position tracking and attitude synchronization controllers are developed independently by using a robust adaptive control approach. The unknown kinematic couplings, parametric uncertainties, and bounded external disturbances are handled with adaptive updating laws. It is proved via Lyapunov method that the pose tracking errors converge to zero asymptotically. Spacecraft close-range rendezvous and proximity operations are introduced as an example to validate the effectiveness of the proposed control approach. [ABSTRACT FROM AUTHOR]

A novel sliding mode control (SMC) design framework is devoted to providing a favorable SMC design solution for the position tracking control of electrohydrostatic actuation system (EHSAS). This framework is composed of three submodules as follows: a reduced-order model of EHSAS, a disturbance sliding mode observer (DSMO), and a new adaptive reaching law (NARL). First, a reduced-order model is obtained by analyzing the flow rate continuation equation of EHSAS to avoid the use of a state observer. Second, DSMO is proposed to estimate and compensate mismatched disturbances existing in the reduced-order model. In addition, a NARL is developed to tackle the inherent chattering problem of SMC. Extensive simulations are conducted compared with the wide adoption of three-loop PID method on the cosimulation platform of EHSAS, which is built by combining AMESim with MATLAB/Simulink, to verify the feasibility and superiority of the proposed scheme. Results demonstrate that the chattering can be effectively attenuated, and the mismatched disturbance can be satisfyingly compensated. Moreover, the transient performance, steady-state accuracy, and robustness of position control are all improved. [ABSTRACT FROM AUTHOR]

Microstepping drive for a stepper motor is a well-known technique to improve the stepper motor performance. Normally, microstepping is carried at fixed pulse width planned. However, this method is suitable only when motors are driven at fixed predefined speeds for non-real-time applications. The problem discussed in this paper considers an application where motors need to track a given reference position profile precisely in real time, whose speed is varying at every interval of time. In such a scenario, fixed speed microstep drive does not meet the high pointing requirements and leads to poor system performance. For such applications, an innovative frequency modulation (FM) based microstep drive algorithm is developed that meets the high degree of motor pointing even at higher output angular rates. As per this scheme, pulse width and the number of steps that motor is supposed to move are derived from the reference position itself in a given amount of time, and the motor is actuated with a corresponding number of steps in real time. FM-based microstep drive is implemented with pulse-width modulation based chopper current controller in an optimized way without compromising on the motor torque margins. Transient error plots obtained through experiments clearly show the advantages of FM-based microstepping over fixed rate. This paper presents the design, analysis, simulation, and experimental results of FM-based microstep drive. [ABSTRACT FROM AUTHOR]

Progress has been made enabling expensive, high-end inertial measurement units (IMUs) to be used as tracking sensors. However, the cost of these IMUs is prohibitive to their widespread use, and hence the potential of low-cost IMUs is investigated in this study. A wearable low-cost sensing system consisting of IMUs and ultrasound sensors was developed. Core to this system is an extended Kalman filter (EKF), which provides both zero-velocity updates (ZUPTs) and Heuristic Drift Reduction (HDR). The IMU data was combined with ultrasound range measurements to improve accuracy. When a map of the environment was available, a particle filter was used to impose constraints on the possible user motions. The system was therefore composed of three subsystems: IMUs, ultrasound sensors, and a particle filter. A Vicon motion capture system was used to provide ground truth information, enabling validation of the sensing system. Using only the IMU, the system showed loop misclosure errors of 1% with a maximum error of 4-5% during walking. The addition of the ultrasound sensors resulted in a 15% reduction in the total accumulated error. Lastly, the particle filter was capable of providing noticeable corrections, which could keep the tracking error below 2% after the first few steps. [ABSTRACT FROM AUTHOR]

Brushed DC motors are essential components in a wide range of applications in which their unique benefits are explored. However, their being inherently nonlinear and sensitive to system based uncertainties such as load variation and process noise has made improving the precision control of brushed DC motors a challenging task. To mitigate such negative effects that invariably undermine motor stability and controllability, a novel wavelet-based nonlinear time-frequency control scheme viable for the concurrent speed and position tracking of brushed DC motors is presented. The control approach has its basis in discrete wavelet transformation and adaptive control. Considering system response in the wavelet domain allows the true dynamics of the system as delineated by both the time and frequency information of the response to be faithfully resolved without being distorted or misinterpreted. By employing adaptive theory, the undesirable features typical of nonlinear brushed DC motor systems such as being highly unstable and energy inefficient are also properly addressed. The validity of the controller design are demonstrated by evaluating its performance and the power requirement against PID control and fuzzy logic control in mitigating the speed, position, and armature voltage responses of a permanent magnet brushed DC motor under severe system uncertainties. The proposed nonlinear controller is shown to be accurate, robust, energy efficient, low in power requirement, and easy to switch between speed and position control. [ABSTRACT FROM AUTHOR]

Field-circuit coupling method is increasingly drawing attention from researchers who engage in electric machine design. It is worth mentioning that no related field-circuit coupling methods have been presented to investigate the dynamic performance for slotted limited-angle torque motor (LATM). Hence, this paper presents a simplified field-circuit coupling method to evaluate the dynamic performance including position tracking ability and operating temperature for slotted LATM during its design optimization process. All magnetic saturation problems including nonlinear torque characteristic and inductance parameter variation with rotor position can be taken into account, which is completely consistent with the actual operation condition. The simplified field-circuit coupling method contains a thermal resistance network (TRN) module which can be applied to estimate the slotted LATM operating temperature in accordance with the accurate winding current and copper loss information. Therefore, whether the slotted LATMs meet design requirements should be evaluated before manufacturing prototypes. Related experiments for the slotted LATM are carried out to validate the field-circuit coupling method cooperating with TRN module. [ABSTRACT FROM AUTHOR]

To design a soldier tracking system using wireless system for monitoring the parameters of soldier are as Body temperature & Temperature. Biomedical sensors: Here to find the health status of soldier we are using a body temp sensor to measure body temperature as well as pulse rate sensor. These parameters are then signal conditioned and will be stored in the memory. One of the fundamental challenges in military operations lays in that the Soldier not able to communicate with control room administrator. In addition, each organization needs to enforce certain administrative and operational work when they interact over the network owned and operated by other organizations. Thus, without careful planning and coordination, one troop cannot communicate with the troops or leverage the communication infrastructure operated by the country troops in the same region. The purpose of this investigation was to test the components of the Soldier Tracking and Performance Measurement System against the statement of requirements as found in the Request for Proposal. Secondary aims of this investigation included gathering data that will allow potential users of the system to understand its capabilities and limitations, as well as allow efficient planning of both time and resources necessary to ensure efficient and productive use of the system for training the solider. [ABSTRACT FROM AUTHOR]

The papers in this special section focus on sliding mode control and observations for complex industrial systems. With the recent rapid developments in industrial technology, the modern industrial systems have become more and more complex requiring a greater attention to be paid on the stabilizability, the robustness, the reliability, and the optimization issues. The recent developments in sliding mode control and observation techniques serve as powerful tools in this respect. The use of sliding mode control offers a number of advantages: insensitivity to external disturbances, system reduction, high accuracy, and finite time convergence. However, there are still several remaining issues that should be solved before it can be extensively used in the industry in the near future, that is, chattering effect, requirement of an accurate model of the system, relative higher complexity and higher implementation cost compared to existing linear controllers. [ABSTRACT FROM AUTHOR]

A singularity-free nonlinear robust controller is proposed for miniature helicopters to accomplish trajectory tracking missions. The helicopter model is decomposed into a cascaded structure with some unmodeled dynamics. The controller development applies the hierarchical strategy. First, a position loop controller is designed based on a saturation control scheme using differential hyperbolic tangent functions, and criteria for choosing controller parameters are established to ensure the finite-time position tracking and to obviate singularity in the command attitude extraction. Singularity may also occur during the attitude tracking when the pitch of the helicopter reaches \pm \frac\pi 2. Based on a barrier Lyapunov function, an attitude loop controller is put forward with a backstepping technique, and an initial condition constraint for the nonsingular attitude tracking is deduced. Simulations illustrate the applicability of the proposed controller. [ABSTRACT FROM PUBLISHER]

The disturbance suppression is one of the most common control problems in electro-hydraulic systems. especially largely an unknown disturbance often obviously degrades the dynamic performance by biasing the desired actuator outputs (e.g., load forces or torques). In order to reject the dynamic disturbances in some multi-degree-of-freedom manipulators driven by electro-hydraulic actuators, this paper proposes a state feedback control of the cascade electro-hydraulic system based on a coupled disturbance observer with backstepping. The coupled disturbance observer is designed to estimate both the independent element and the coupled element of the external loads on each electro-hydraulic actuator. The cascade controller has the ability to compensate for the disturbance estimating, as well as guarantees the system state error convergence to a prescribed steady state level. The effectiveness of the proposed controller for the suppression of largely unknown disturbances has been demonstrated by comparative study, which implies the proposed approach can achieve better dynamic performance on the motion control of Two-Degree-of-Freedom robotic arm. [ABSTRACT FROM AUTHOR]

High-pressure rubber hose is normally used to connect the control valves and actuators of hydraulic systems and thus lower their natural frequency. PID control is preferred in industrial hydraulic systems as it has many advantages over other controls. However, the low natural frequency of hose-connected systems limits the performance of PID control. In this paper, a hose-connected hydraulic lifting test rig is presented and the mathematical model of the system is proposed. Valve compensation strategy and hose compensation strategy are designed based respectively on the flow characteristic of the proportional valve and the mathematical model of the hose. Comparative experiments with typical desired trajectories are carried out in the test rig. Results show that both the compensation strategies are effective in improving the tracking accuracy. [ABSTRACT FROM AUTHOR]

Stabilization of a class of underactuated vehicles with uncertain measurements of the position tracking error is addressed. Nonlinear feedback laws ensuring semi-global stability for a large class of uncertainties on these measurements are derived based on properties of saturated controls. Practical relevance of the proposed results is illustrated by two application examples for Vertical Take-Off and Landing aerial vehicles equipped with a mono-camera sensor: point stabilization in front of a planar target and visual way-points navigation based on interpolation of homography measures. [ABSTRACT FROM AUTHOR]

In this paper, a new bounded force feedback control law is proposed to guarantee position and force tracking in nonlinear teleoperation systems in the presence of passive and nonpassive input interaction forces, time varying delay in their communication channels and sandwich linearity in their actuators. The proposed control is a nonlinear-proportional plus nonlinear damping (nP+nD ) controller with the addition of a nonlinear function of the environment force on the slave side and nonlinear function of the human force and force error on the master side, the transparency of the proposed scheme will be improved. The controller prevents the inputs from reaching their usual actuator bounds. Using a novel Lyapunov–Krasovskii functional, the asymptotic stability and tracking performance of the teleoperation system are established under some conditions on the controller parameters, actuator saturation characteristics and maximum allowable time delays. [ABSTRACT FROM AUTHOR]

This paper focuses on the quality improvements on clinching joints using a servo press with a Radial basis function neural network and a sliding mode (RBFS) control strategy. Bottom thickness, which is affected by the press punch position, is usually used to monitor clinching joint quality. Traditional clinching presses are driven by pneumatic pistons or motors that provide feedback on punch force or motor position. However, this feedback is indirectly related to the joint bottom thickness. Clinching workers who set the control parameters on these presses depend on tests and statistics. Thus, this paper presents a servo press system that utilizes punch position feedback to directly control the joint bottom thickness. Transmission errors are considered for the movement accuracy of the servo press. A mathematical model of the servo press is established for analyzing. An algorithm, which combines RBF neural network and sliding mode, is proposed and applied for press position tracking. This algorithm adopts an RBF neural network to approximate the nominal model of the press system. The update law of the algorithm is based on the Lyapunov function used to prove the stability of a closed-loop system. The sliding mode controller compensates for the neural network error and disturbance. Finally, experiments are executed on the servo press with an RBFS controller. To evaluate the performance of the proposed method, a fuzzy PID controller is also applied to the press for comparison. The results indicate that the servo clinching press system with RBFS efficiently and accurately control the clinching jointing process. [ABSTRACT FROM AUTHOR]

For the Internet of Things to be people-centered, things need to identify when people and their things are nearby. In this article, we present the design, implementation, and deployment of a positioning system based on mobile and fixed inexpensive proximity sensors that we use to track when individuals are close to an instrumented object or placed at certain points of interest. To overcome loss of data between mobile and fixed sensors due to crowd density, traditional approaches are extended with mobile-to-mobile proximity information. We tested our system in a museum crowded with thousands of visitors, showing that measurement accuracy increases in the presence of more individuals wearing a proximity sensor. Furthermore, we show that density information can be leveraged to study the behavior of the visitors, for example, to track the popularity of points of interest, and the flow and distribution of visitors across floors. [ABSTRACT FROM AUTHOR]

This paper investigates the finite-time position tracking control problem of pneumatic servo systems subject to hard nonlinearities and various disturbances. A finite-time disturbance observer is firstly designed, which guarantees that the disturbances can be accurately estimated in a finite time. Then, by combining disturbances compensation and state feedback controller together, a nonsmooth composite controller is developed based on sliding mode control approach and homogeneous theory. It is proved that the tracking errors under the proposed composite control approach can be stabilized to zero in finite time. Moreover, compared with pure state feedback control, the proposed composite control scheme offers a faster convergence rate and a better disturbance rejection property. Finally, numerical simulations illustrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Flood disasters such as dam breaks and surges from extreme hurricanes or tsunamis entrain and transport substantial amounts of submerged or floating debris. Understanding of motion and spatiotemporal distribution of debris entrained by a flood is thus of great importance to hydraulic, coastal, and structural engineers; the displacement of debris to a location where it may eventually impact critical infrastructure requires scientific attention at the laboratory scale first. In this context, the design and application of a novel smart debris system utilizing off-the-shelf components is presented and discussed. The system tracks the spatial location and orientation of a multitude of debris specimens and it proposes an accurate tool to assess their individual trajectory, velocity, and momentum in a laboratory environment. Contrary to the traditional camera-based approach of video tracking, which often fails once objects are submerged, the proposed smart debris system delivers six-degree-of-freedom (6DOF) data in a reliable, timely manner. Miniaturized inertial measurement units (IMU), commonly called motion sensors, which are used for attitude heading reference systems are deployed to output time series of spatial orientation along with filtered 3D acceleration readings. A Bluetooth low-energy (BLE) tracking system is applied along with the motion sensor to track the 3D debris positions. A detailed investigation in controlled laboratory conditions reveals the detailed individual performance of the tested spatial orientations and positions. As an application, debris transport tests were conducted in a newly built tsunami wave basin at Waseda University in Tokyo, Japan. For this test series, a typical harbor layout with a vertical quay wall adjacent to a horizontal container-stacking platform was constructed. The advection by a broken tsunamilike bore of multiple down-scaled shipping containers in basic arrangements was then tracked from their initial position. The performance of the innovative smart debris system is qualitatively tested in order to provide guidance for their future application in hydraulic and coastal engineering as well as to provide a solid basis for its application in field studies. [ABSTRACT FROM AUTHOR]

In this paper, the position tracking control problem of pneumatic servo systems is investigated. These systems usually have high nonlinearities and unmeasurable piston velocities. Firstly, by using adding a power integrator technique, a global finite-time state feedback controller is proposed. Secondly, based on homogeneous theory, a nonlinear observer is developed to estimate the piston velocity. Finally, the corresponding output feedback controller is derived, which local finite-time stabilizes the position tracking error system. Compared with the conventional backstepping output feedback control scheme, the developed nonsmooth output feedback control scheme offers a faster convergence rate and a better disturbance rejection property. Numerical simulations illustrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

As pervasive computing is widely available during daily activities, wearable input devices which promote an eyes-free interaction are needed for easy access and safety. We propose a textile wearable device which enables a multimodal sensing input for an eyes-free mobile interaction during daily activities. Although existing input devices possess multimodal sensing capabilities with a small form factor, they still suffer from deficiencies in compactness and softness due to the nature of embedded materials and components. For our prototype, we paint a conductive silicone rubber on a single layer of textile and stitch conductive threads. From a single layer of the textile, multimodal sensing (strain and pressure) values are extracted via voltage dividers. A regression analysis, multi-level thresholding and a temporal position tracking algorithm are applied to capture the different levels and modes of finger interactions to support the input taxonomy. We then demonstrate example applications with interaction design allowing users to control existing mobile, wearable, and digital devices. The evaluation results confirm that the prototype can achieve an accuracy of ≥ 80 % for demonstrating all input types, ≥ 88 % for locating the specific interaction areas for eyes-free interaction, and the robustness during daily activity related motions. Multitasking study reveals that our prototype promotes relatively fast response with low perceived workload comparing to existing eyes-free input. [ABSTRACT FROM AUTHOR]

In terms of the varying number of cell population, shape deformation, collision and uneven movement, a novel method based on multi-task particle swarm optimization (PSO) algorithm without explicit detection module, named MTPSO tracking method, is developed for automatic tracking of biological cells in time-lapse low-contrast microscopy image sequences. For tracking existing cells from the previous frames, a PSO-based tracking module is firstly implemented to give the initial positions of existing cells according to the previous estimated state of each cell, then a PSO-based contour module is proposed to determine the corresponding contour of each cell and finally achieve a precise position tracking by an iterative centroid updating process. For tracking new appearing cells at the current frame, a PSO-based discovery module, followed by the aforementioned PSO-based contour module, is proposed to search for new potential cells through appropriate initialization of particle swarm and searching mechanism. MTPSO tracking method is tested over a number of different real cell image sequences and is shown to provide high accuracy both in position and contour estimate of each cell in various challenging cases. Furthermore, it is more competitive against the state-of-the-art multi-object tracking methods in terms of performance measures such as FAR, FNR, LTR, and LSR. [ABSTRACT FROM AUTHOR]

SUMMARY We carry out a technological examination for improving the positional detection accuracy of position tracking. In this paper, we focus on positional detection technology that uses a scale in which slits are carved at a certain constant period. We develop phase modulation signal generation technology that removes a signal of two frequencies of a one-signal detection track. We report on the detection principle and the results of the principle verification experiment. [ABSTRACT FROM AUTHOR]