bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Piezoelectric Self-Sensing Performance for Varying Piezoelectric Capacitance and Adaptation Gain
Authors: Lundstrom Troy , Jalili Nader
Published: November 2017

The simultaneous measurement/electrical actuation of piezoelectric elements has been a subject of considerable interest in previous research. Within a limited bandwidth, piezoelectric materials can be modeled electrically as a voltage source and capacitor in series and when these components are integrated into a balanced capacitive bridge, simultaneous actuation and strain sensing is possible. Unfortunately, due to the sensitivity of piezoelectric materials to changing environmental conditions (temperature) and applied voltages, an adaptive scheme is required to maintain a balanced bridge and reduce high voltage spillover into the measurement channel. Even minute changes in the piezoelectric capacitance can overwhelm the strain sensing signal with high voltage content thereby preventing accurate strain sensing. The purpose of this work is to apply the self-sensing algorithm to a flexible structure with piezoelectric sensors/actuators mounted to its surface. The flexible structure utilized in this paper is composed of a small, cantilever resonator beam with two piezoelectric patches integrated into its structure and this beam is mounted at a arbitrary location to a larger, primary cantilever beam. The first two resonances of the actuator beam were tuned to that of the primary beam. High voltage signals are applied to the patch near the root of the resonator beam and simultaneous strain-induced voltage sensing is performed. Simulations have shown that estimation performance degrades with increasing rates of piezoelectric capacitance variation and conversely, adaptation times were found to decrease with increasing adaptive gains over the limited ranges of gains applied.
Limit Cycle Analysis and Control of the Dissipative Chaplygin Sleigh
Authors: Fedonyuk Vitaliy , Tallapragada Phanindra , Wang Yongqiang
Published: November 2017

There are many types of systems in both nature and technology that exhibit limit cycles under periodic forcing. Sometimes, especially in swimming robots, such forcing is used to propel a body forward in a plane. Due to the complexity in studying a fluid system it is often useful to investigate the dynamics of an analogous land model. Such analysis can then be useful in gaining insight about and controlling the original fluid system. In this paper we investigate the behavior of the Chaplygin sleigh under the effect of viscous dissipation and sinusoidal forcing. This is shown to behave in a similar manner as certain robotic fish models. We then apply limit cycle analysis techniques to predict the behavior and control the net translational velocity of the sleigh in a horizontal plane.
A Receding Horizon Switching Control Resilient to Communication Failures for Connected Vehicles
Authors: Savaia Gianluca , Abdollahi Biron Zoleikha , Pisu Pierluigi
Published: November 2017

This paper focuses on networked control systems subject to network-induced constraints, namely transmission delays and packet dropping. The proposed framework is based on a switching control logic which selects the optimal control action in a finite set of strategies tailored to a specific scenario. The switching logic relies on a receding horizon optimization — which resembles model predictive control — and does not require any prior knowledge on the condition of the network. This strategy is tested on a platoon of connected vehicles engaged in cooperative adaptive cruise control which communicate over an imperfect DSRC network. The main objective consists in avoiding unsafe scenarios where the network is subject to the aforementioned failures; results show the proposed approach achieves the objective whereas a nominal controller would lead the platoon to crash.
A Sequential LMI Approach for Design of a Gain-Scheduled PID Controller for LPV Systems
Authors: Wang Yan , Rajamani Rajesh
Published: November 2017

This paper aims at developing a robust gain-scheduled proportional-integral-derivative (PID) control design method for a linear-parameter-varying (LPV) system. It is recognized in the literature that robust fixed-order controller design can be formulated as a feasibility problem of a bilinear matrix inequality (BMI) constraint. Unfortunately, the search for a feasible solution of a BMI constraint is a NP hard problem in general. A common way to solve this dilemma is to apply a linearization method, such as variable change method or congruence transformation, to transform the BMI into LMI. The applicability of the linearization method depends on the specific structure of the problem at hand and cannot be generalized. This paper formulates the gain-scheduled PID controller design as a feasibility problem of a quadratic matrix inequality (QMI) constraint, which covers the BMI constraint as a special case. An augmentation of the newly developed sequential LMI optimization method is proposed to search for a feasible solution of a QMI constraint iteratively. In the application part, a vehicle lateral control problem is presented to demonstrate the applicability of the proposed algorithm to a real-world output feedback control design.
Torque Characterization of a Novel Pneumatic Soft-and-Rigid Hybrid Actuator
Authors: Haghshenas-Jaryani Mahdi , Manvar Maulik , Wijesundara Muthu B. J.
Published: November 2017

This paper presents development of a theoretical model for predicting the torque generated by a pneumatic soft-and-rigid hybrid actuator at a given actuation pressure and bending angle. The soft actuator with a novel architecture is comprised of half bellow-shaped flexible hollow structure (soft section) in-between block-shaped semi-rigid sections made of silicone rubber materials. This actuator provides forward and backward bending motion when air pressure and vacuum are applied into the soft section, respectively. A simplified steady-state model was developed based on the quasi-static assumption when the system dynamics is slow enough that all of the interacting forces comes to an equilibrium at any given bending angle during the motion. The elastomeric material was modeled using the Yeoh 3rd order model to capture its nonlinear behavior. The model was studied for the soft actuators with different geometrical features in two cases of the free end motion (without external force) and the constrained end motion (with external force). Experimental testing and finite element simulations were carried out corresponding to the case-studies to validate the model. Comparison of the results obtained by these two approaches show a good agreement with the theoretical model’s prediction.
Direct Tail Actuation vs Internal Rotor Propulsion in Aquatic Robots
Authors: Pollard Beau , Berkey Tyler , Tallapragada Phanindra
Published: November 2017

It is common for scientists to look to nature for inspiration in developing robots. Many times biological creatures outperform even the best man made robots. We will be focusing on aquatic locomotion of robots inspired by the locomotion of fish. There are two different means of propulsion of the robots tested in this paper. One model of the robot is propelled only through the oscillations of an internal momentum wheel, while the other is propelled by the direct actuation of a tail structure. Both of these models achieve net propulsion through vortex shedding past their trailing edge, and two of the robots locomotion is also aided by the change in shape from either a passive or active tail. Tests were conducted to highlight the locomotion performance differences of the two different means of locomotion.
Projection Method With Minimal Correction Procedure for Numerical Simulation of Constrained Dynamics
Authors: Heaney Patrick S. , Hou Gene
Published: November 2017

This paper describes a numerical technique for simulating the dynamics of constrained systems, which are described generally by differential-algebraic equations. The Projection Method for index reduction of a differential-algebraic equation and a minimal correction procedure are described. This procedure ensures algebraic constraints are satisfied during the numerical integration of the reduced index system of differential equations. Two examples illustrate how the method can be utilized to solve constrained multibody and rotational dynamics problems. The efficiency and accuracy of the proposed index-reduction and minimal correction method are then evaluated.
Neuroadaptive Control for Trajectory Tracking of Indirect Drive Robots
Authors: Zhao Yu , Yu Xiaowen , Tomizuka Masayoshi
Published: November 2017

Most industrial robots are indirect drive robots, which utilize low torque and high speed motors. Indirect drive robots have gear reducers between the motors and links. Due to the flexibility of transmission units, it is difficult to achieve high accuracy for trajectory tracking. In this paper, a neuroadaptive control, which is essentially a neural network (NN) based adaptive back-stepping control approach, is proposed to deal with this problem. The stability of the proposed approach is analysed using Lyapunov stability theory. A data-driven approach is also proposed for the training of the neural network. The effectiveness of the proposed controller is verified by simulation of both single joint and 6-axis industrial robots.
Position and Attitude Control by Rotor Tilt and Rotor Speed Synchronization for Single Axis Tilting-Rotor Quadcopter
Authors: Kumar Rumit , Nemati Alireza , Kumar Manish , Cohen Kelly , Cazaurang Franck
Published: November 2017

In this paper, the control maneuvering, and performance analysis of a tilting-rotor quadcopter during autonomous flight is presented. Unlike traditional quadcopters, a tilting-rotor quadcopter provides additional actuated controls as the propeller motors are actuated for tilt which can be utilized to improve efficiency of the aerial vehicle during flight. The tilting-rotor quadcopter design is accomplished by using an additional servo motor for each rotor that enables the rotor to tilt about the axis of quadcopter arm. Here, a detailed control strategy has been discussed to use the propeller tilts for position and orientation control during completely autonomous flights of the quadcopter. In conventional quadcopters, the variation in rotational speeds of the four propellers is utilized for maneuvering. This work incorporates use of varying propeller rotational speeds along with tilting of the propellers for maneuvering the quadcopter during flight. A PD controller is developed to achieve various modes of flight and numerical simulation results are presented demonstrating the performance of the controller. Furthermore, the performance of the tilt-rotor design is compared with respect to the conventional quadcopter in the presence of wind disturbances and uncertainties in the system.
Topology Optimization of Structural Systems Considering Both Compliance and Input Observability
Authors: Ren Yi , Yao Houpu , Lin Xinfan
Published: November 2017

Recent advances in flexible and wireless sensors, soft materials, and additive manufacturing, have stimulated demands for developing intelligent systems that can achieve multidisciplinary objectives (e.g., mechanical strength, thermal conductivity, state and input estimation, controllability, and others). Existing studies often decouple these objectives through sub-system level design, e.g., topology and material design for mechanical and thermal properties, and filter and sensor/actuator design for observability and controllability, assuming that the sub-systems have minimal influences to each others. To investigate the validity of this assumption, we take a unique angle at studying how the topology of the system influences both structural performance (e.g., compliance under static loads) and input observability (e.g., the error in estimating the loads). We reveal a tradeoff between these two objectives and derive the Pareto frontier with respect to the topology. This preliminary result suggests the necessity of a multiobjective formulation for designing intelligent structures, when significant tradeoffs among system objectives exist.
Guess-Free Pseudospectral Solution for Time Optimal Swing-Up of a Rotary Inverted Pendulum
Authors: Frontera Paul J. , Feemster Matthew , Hurni Michael , Karpenko Mark
Published: November 2017

Control of the inverted pendulum is a canonical problem in nonlinear and optimal control. Over the years, many workers have developed solutions for inverting the pendulum link (swing-up phase) and for maintaining the pendulum link upright (stabilization/disturbance rejection). In this paper, the time-optimal swing-up of a rotary inverted pendulum is studied. Previous solutions to this problem have required that the original time-optimal problem formulation be transformed to a more computationally tractable form. For example, one transformation is to a fixed-time problem with bounds on the control. Other approaches involve guessing the switching structure in order to construct a candidate solution. Advances in computational optimal control theory, particularly pseudospectral optimal control, allow the original time-optimal problem to be solved directly, and without the need for a guess. One such solution is presented in this paper. It is shown that the result adheres to the conditions of Pontryagin’s minimum principle. An experimental implementation of the solution illustrates its feasibility in practice.
Combined Plant and Controller Design Using Bayesian Optimization: A Case Study in Airborne Wind Energy Systems
Authors: Baheri Ali , Deese Joseph , Vermillion Christopher
Published: November 2017

This paper presents a novel data-driven nested optimization framework that aims to solve the problem of coupling between plant and controller optimization. This optimization strategy is tailored towards instances where a closed-form expression for the system dynamics is unobtainable and simulations or experiments are necessary. Specifically, Bayesian Optimization, which is a data-driven technique for finding the optimum of an unknown and expensive-to-evaluate objective function, is employed to solve the nested optimization problem. The underlying objective function is modeled by a Gaussian Process (GP); then, Bayesian Optimization utilizes the predictive uncertainty information from the GP to decide the best subsequent control or plant parameters. The proposed framework differs from the majority of co-design literature where there exists a closed-form model of the system dynamics. We validate the proposed framework for Altaeros’ Buoyant Airborne Turbine (BAT). We choose the horizontal stabilizer area and longitudinal center of mass relative to center of buoyancy (plant parameters) and the pitch angle set-point (controller parameter) as our decision variables. Our results demonstrate that plant and control parameters converge to optimal values within only a few iterations.
Theoretical Development of a Modified RANSAC Algorithm for Identifying Outliers in Road Surface Data
Authors: Pereira Savio J. , Altmann Craig T. , Ferris John B.
Published: November 2017

Modeling and simulation of vehicles can be improved by using actual road surface data acquired by Road Surface Measurement Systems. Due to inherent properties of the sensors used, the data acquired is often ridden with outliers. This work addresses the issue of identifying and removing outliers by extending the robust outlier rejection algorithm, Random Sampling and Consensus (RANSAC). Specifically, this work modifies the cost function utilized in RANSAC in such a way that it provides a smooth transition for the classification of points as inliers or outliers. The modified RANSAC algorithm is applied to neighborhoods of data points, which are defined as subsets of points that are close to each other based on a distance metric. Based on the outcome of the modified RANSAC algorithm in each neighborhood, a novel measure for determining the likelihood of a point being an outlier, defined in this work as its exogeny, is developed. The algorithm is tested on a simulated road surface dataset. In the future this novel algorithm will also be tested on real-world road surface datasets to evaluate its performance.
Uncertainty Bounding of CFRP Beams Towards Robust Control of Flexible Composite Structures
Authors: Pesch Alexander H. , LongJohn Tamunomiesiya , Wagner Kristopher , McAndrews Brian J.
Published: November 2017

As composite materials are becoming increasingly applied in actively controlled flexible structures, the need for practical uncertainty bounding to capture the effect of normal manufacturing variations on their dynamic behavior is also increasing. Currently, there is a lack of quantification of manufacturing variation of composite materials cast in a robust control framework. This work presents a simple experimental study on a particular case of composite member. The modal parameters of a set of 12 unidirectional carbon fiber reinforce polymer beams are identified. A nominal finite element model is numerically fit to the average experimental natural frequencies and antiresonances. The model is augmented with real parametric uncertainties placed on the modal parameters. The bound on the uncertainties is found both deterministically, to capture all experimentally observed data, and stochastically using a predetermined confidence interval. The two uncertainty bounding approaches are compared through the resulting bound on the beam model frequency response. Also, simulations are conducted to compare possible time responses using the two uncertainty bounds. It is found that the utilized structure of parametric uncertainties is effective at capturing the experimentally observed behavior.
Robust Boundary Control for an Euler Bernoulli Beam Subject to Unknown Harmonic Disturbances With a Focus on Resonance
Authors: Karagiannis Dimitri , Radisavljevic-Gajic Verica
Published: November 2017

In this paper, a sliding mode backstepping controller for a pinned-pinned Euler-Bernoulli beam is briefly reviewed and its efficacy in the presence of unknown bounded harmonic disturbances at arbitrary frequencies is analyzed. A brief discussion of the open-loop unstable response to harmonic excitations at resonant frequencies is provided. Motivated by this, particular attention is given to excitations at the natural frequencies of the system. It is shown that in the face of such resonant disturbances, the sliding mode backstepping controller is able to eliminate the vibrations in the beam system where backstepping control alone cannot. Indeed it is shown that if the disturbances are not accounted for, the closed loop system exhibits large (relative to the initial conditions) steady state harmonic vibrations. When the unknown resonant harmonic disturbances are accounted for via the sliding mode backstepping technique, the steady state position is constant and does not exhibit any vibrations, and furthermore it reaches this steady state exponentially at an arbitrarily selected rate.
Modeling and Experimental Testing of Hoverboard Dynamic Behavior
Authors: Castro Arnoldo , Singhose William , Liu Xiaoshu , Sorensen Khalid , Kwak Eun Chan
Published: November 2017

Self-balancing human transporters are naturally unstable. However, when coupled with sophisticated control laws, these machines can provide mobility within a finite stability envelope. Challenging environmental conditions, or unanticipated operator action, can cause these machines to exhibit unexpected behavior. In an effort to better understand the behavior of these systems inside and outside the stability envelope, a dynamic model of a hoverboard is presented. Motion-capture data is also presented in which an operator’s interactions with the hoverboard were recorded.
Relative Position Estimation Using Monocular Camera and Ultra-Wide Band Ranging
Authors: Dawkins Jeremy J.
Published: November 2017

This paper presents a methodology for estimating the relative position between a micro aerial vehicle (MAV) and a base-station using a monocular camera and an ultra-wide band (UWB) ranging module. The pinhole camera model is used to derive a relationship that relates the 3D position of the vehicle to its location in the image frame and the estimated range. A tracking algorithm was implemented to track the location of a light emitting diode (LED) array mounted to the MAV with a low cost webcam. The range was determined by using a two-way ranging algorithm with the UWB modules. The presented methodology is applied to experimental data collected from a quad-rotor. The results are compared to a motion capture system, and it is shown that this method is able to track the position of the MAV to within the range accuracy of the UWB modules. This relative position estimation methodology has the potential to be a viable component of a navigation system for cooperative vehicles.
Online Hybrid Model Predictive Controller Design for Cruise Control of Automobiles
Authors: Merat Kaveh , Abbaszadeh Chekan Jafar , Salarieh Hassan , Alasty Aria
Published: November 2017

In the proposed study, a Hybrid Model Predictive Controller is introduced for cruise control of an automobile model. The presented model consists of the engine, the gearbox, and the transmission dynamics, where the aerodynamics force and elastic friction between the tires and road are taken into account. Through Piecewise Linearization of nonlinearities in the system; (torque)-(throttle)-(angular velocity) of engine and (aerodynamic drag force)-(automobile velocity), a comprehensive piecewise linear model for the system is obtained. Then combined with the switch and shift between engaged gears in gearbox, the Piecewise Affine (PWA) model for the vehicle dynamics is acquired. As far as the control design is concerned, the cruise control problem for tracking a desired speed fashion is addressed by a MPC-based controller design. The proposed control approach is based on the online model predictive control, applied on the obtained PWA dynamics. The highlighted novelties of the presented research work are summarized as: first a more complete model is examined due to the consideration of a realistic model for engine. This improvement makes the polyhedron regions of the PWA system dependent to both state variable (i.e., velocity) and input signals (i.e., throttle and engaged gear) which brings the complexity to the design of control procedure. Second, due to the switch in the dynamics and dependence of our PWA model to discrete input (gear shift), the desperate need to solve the optimization problem through mixed integer programming, which needs high computation effort specially for our system, seems inevitable. We triumph over this challenge through introducing “possible gear shift scenario” sets. Hence, by constraining the optimization problem to the introduced logical sets, the problem still remains convex optimization type and the computation volume is reduced. In addition, we hired branch and bound method which allowed us to have large problems to be solved in a tractable amount of time and computation resources. At last, some simulations are presented to exhibit the performance of the proposed method.
Design and Analysis of a Pose Estimator for Quadrotor MAVs With Modified Dynamics and Range Measurements
Authors: Fernando Eranga , Mann George K. , De Silva Oscar , Gosine Raymond G.
Published: November 2017

This paper presents the design and analysis of a pose estimator for quadrotor micro aerial vehicles (MAVs). The proposed design uses the dynamic model of the quadrotor with aerodynamic effects and uses the extended Kalman filter (EKF) formulation for state estimation. Range measurements to known locations, inertial measurements and height measurements are used for the estimation task. The purpose of the study is to evaluate the performance of the estimator when navigating through a changing indoor setting. The study investigates the effect of changing number of rannge measurements, different geometrical arrangements of range sensors and changing availability of confident height information on the performance of the estimator. Performance of the estimator for each scenario is numerically analyzed. Finally a criteria is proposed for selecting the sensors, number of range measurements, geometric location of sensors which facilitates accurate position estimation using the proposed method.
A New Semi-Active Suspension System for Vehicle Applications
Authors: Siramdasu Yaswanth , Taheri Saied
Published: November 2017

The goal of this study is two fold, one is to introduce a novel double damper based semi active suspension design and the other is to demonstrate the application of dynamic tire model in development of suspension controllers. In this study, a novel double damper suspension is introduced to show that a simple design modification of suspension can further improve the performance of the semi active suspension. A dynamic tire model was developed using a rigid ring tire and a tandem elliptical cam design for the enveloping model. A Lyapunov based adaptive ride control algorithm using a quarter car vehicle model with single damper and double damper suspension is developed. An ideal Skyhook-Groundhook 2DOF suspension is used as the reference model. The tire model and active suspension controller are then integrated with a full vehicle model to perform ride analysis. Using RMS acceleration of sprung mass vertical, roll and pitch motions as ride performance metrics, ride performance of no control, fully active control of single damper suspension and semi active control of double damper suspension are performed. The simulation results demonstrated that the importance of considering tire enveloping and dynamic effects and the emulation of novel semi active suspension system as active suspension without bottoming of suspension or deterioration of road holding properties. This behavior results in reduced power consumption, complexity and cost while the system performs like a fully active suspension system.
ARX Model of a Residential Heating System With Backpropagation Parameter Estimation Algorithm
Authors: Burger Eric M. , Moura Scott J.
Published: November 2017

Model predictive control (MPC) strategies hold great potential for improving the performance and energy efficiency of building heating, ventilation, and air-conditioning (HVAC) systems. A challenge in the deployment of such predictive thermo-static control systems is the need to learn accurate models for the thermal characteristics of individual buildings. This necessitates the development of online and data-driven methods for system identification. In this paper, we propose an autoregressive with exogenous terms (ARX) model of a thermal zone within a building. To learn the model, we present a backpropagation approach for recursively estimating the parameters. Finally, we fit the linear model to data collected from a residential building with a forced-air heating and ventilation system and validate the accuracy of the trained model.
PTEM Based Moving Obstacle Detection and Avoidance for an Unmanned Ground Vehicle
Authors: Rajashekaraiah Gangadhar , Sevil Hakki Erhan , Dogan Atilla
Published: November 2017

This study presents the development and implementation of an autonomous obstacle avoidance algorithm for an UGV (Unmanned Ground Vehicle). This research improves the prior work by enhancing the obstacle avoidance capability to handle moving obstacles as well as stationary obstacles. A mathematical representation of the area of operation with obstacles is formulated by PTEM (Probabilistic Threat Exposure Map). The PTEM quantifies the risk in being at a position in an area with different types of obstacles. A LRF (Laser Range Finder) sensor is mounted on the UGV for obstacle data in the area that is used to construct the PTEM. A guidance algorithm processes the PTEM and generates the speed and heading commands to steer the UGV to assigned waypoints while avoiding obstacles. The main contribution of this research is to improve the PTEM framework by updating it continuously as new LRF readings are obtained, on the contrary to the prior work with fixed PTEM. The improved PTEM construction algorithm is implemented in a MATLAB/Simulink simulation environment that includes models of the UGV, LRF, all the sensors and actuators needed for the control of the UGV. The performance of the algorithm is also demonstrated in real time experiments with an actual UGV system.
Physics-Based Friction Model With Potential Application in Numerical Models for Tire-Road Traction
Authors: Emami Anahita , Khaleghian Seyedmeysam , Su Chuang , Taheri Saied
Published: November 2017

Good understanding of friction in tire-road interaction is of critical importance for vehicle dynamic control systems. Most of the friction models proposed to describe the friction coefficient between tire-treads and road surfaces have been developed based on empirical or semi-empirical relations that are not able to include many effective parameters involved in the tire-road interactions. Therefore, these models are just useful in limited conditions similar to the experiments, and do not accurately represent tire-road traction in numerical tire models. However, in last two decades, a few theoretical models have been developed to calculate the tire-road friction coefficient theoretically by considering both viscoelastic behavior of tire tread compounds and multi-scale interactions between tire treads and rough road surfaces. In this article, a novel physics-based model proposed by Persson has been investigated and used to develop computer algorithms for calculation of sliding friction coefficient between a tire tread compound and a rough substrate. The viscoelastic behavior of tread compound and the surface profile of rough counter surface are the inputs of this physics-based theoretical model. The numerical results of the model have been compared with the experimental results obtained from a dynamic friction tester designed and built in the Center for Tire Research (CenTire). Good agreement between numerical results of theoretical model and experimental results has been found at intermediate range of slip velocities considering the effect of adhesion and shearing in the real contact area in addition to hysteresis friction due to internal energy dissipation in the tire tread compound.
Omni Directional Moving Object Detection and Tracking With Virtual Reality Feedback
Authors: Zirakchi Armaan , Lundberg Cody Lee , Sevil Hakki Erhan
Published: November 2017

Computer vision methods are commonly used to detect and track motion using conventional cameras, however, that is limited with the field of view (FOV) of the camera. This study is to attempt to overcome this challenge by using a 360 degree camera. Our approach utilizes background subtracter from OpenCV Library which creates a continuously updating background model for the motion detection. The model is subtracted from the current frame leaving contours symbolizing the movement observed in the camera view. These contours are then analyzed and processed so that the system can track the largest contour. The tracked movement is outlined and directed to the user via Virtual Reality (VR) headset. The VR headset only displays a 60 degree portion of the camera view to the user which provides more realistic situational awareness of the surroundings for the user. These activities are a part of a larger effort to establish a foundation for autonomous unmanned vehicle systems with situational awareness capabilities.
An Inertial Sensor to Measure Wind Turbulence With RC Helicopters
Authors: Kumar Anil , Ben-Tzvi Pinhas
Published: November 2017

This paper presents a wireless sensor system developed to use RC helicopter dynamics to measure wind turbulence. Wind turbulence is a safety concern for naval helicopter operations due to typical scarcity of landing/takeoff area on naval vessels. Wind turbulence affects the dynamics of helicopters by creating uneven thrust on the rotor blades. The proposed telemetry system, when retrofitted on an RC helicopter, extracts these external disturbances in the helicopter’s dynamics and maps the wind conditions. This study focuses on learning the helicopter’s dynamics in controlled wind conditions using machine learning algorithms. The presented telemetry system uses sensors such as an Inertial Measurement Unit (IMU), optical trackers, and GPS sensors to measure the dynamics of the flying RC helicopter. The system also measures the pilot’s radio inputs to account for pilot inputs in the helicopter’s dynamics. The telemetry system is trained and tested in a large indoor facility where turbulent wind conditions were created artificially using large wind circulation fans.
Modeling and Analysis of Directional Drilling Dynamics
Authors: Feng Tianheng , Vadali Madhu , Chen Dongmei
Published: November 2017

Directional drilling technology provides more flexibility in the selection of rig locations than conventional vertical drilling. It significantly increases drilling efficiency by avoiding undesirable rock formations. In addition, it maximizes production efficiency by increasing the exposed area of a reservoir and grouping multiple reservoirs. In drilling operations, the analysis of drillstring dynamics is critical to circumvent undesirable vibrations and to improve performance. Linear modeling methods are insufficient to describe the system dynamics because directional drilling, unlike vertical drilling, causes the drillstring and the bottomhole assemble (BHA) to bend with a large curvature. In this paper, a model, based on the finite element method (FEM), is established to characterize the dynamics of a directional drill-string. High computational efficiency is achieved by separating the overall displacement into an initial displacement representing the nonlinear bending and a small deformation linear dynamic model. The proposed model is verified against two case studies from the literature, and the comparisons show accurate results. To demonstrate the utility of the proposed model, a BHA force model is included, which considers bit-rock collision, hydraulic damping of the mud, and the eccentricity of the BHA. The simulation results show the capabilities of the model in describing typical drilling vibrations.
Dynamically Planning Operating Room Schedules Using Model Predictive Control
Authors: Zeng Zhigang , Freiheit Theodor
Published: November 2017

Efficient management of operating room (OR) schedules is of particular interest as this service is the largest cost and revenue center in a hospital and can substantially impact its staffing and finances. A major problem associated with developing OR schedules for elective surgeries is the uncertainty inherent in the duration of surgical services which can disrupt a daily plan. Another problem is the impact of facilities and resources upstream and downstream to the operating room, which affect the performance of the overall system. Using a manufacturing system analytical approach, the peri-operative process is modeled as a transfer line with three machines and two buffers using a discrete time Markov chain. Model predictive control is then applied to control the pace of patient release into the OR rooms. With this model and empirical studies of OR and recovery duration, guidance can be given to OR managers on how to dynamically schedule and reschedule patients throughout an operating room’s day that minimizes cost for a given workload.
Approximation of Capture Sets in Visibility-Based Target-Tracking Games for Non-Holonomic Players
Authors: Zou Rui , Bhattacharya Sourabh
Published: November 2017

In this work, we analyze approximations of capture sets [1] for a visibility based pursuit-evasion game. In contrast to the capture problem, the pursuer tries to maintain a line-of-sight with the evader in free space in our problem. We extend the concept of U set initially proposed in [2] for holonomic players to the scenario in which the pursuer is holonomic. The problem of computing the U set is reduced to that of computing time-optimal paths for the non-holonomic vehicles to an arbitrary line. We characterize the primitives for time-optimal paths for the Dubin’s vehicle, Reed-shepps car and a Differential Drive robot. Based on these primitives, we construct the optimal paths and provide an algorithm to compute the U set.
Analysis and Enhancement of Hybrid Skyhook-Groundhook Semi-Active Suspension Controller for Optimal Performance
Authors: Ghasemalizadeh Omid , Taheri Saied , Singh Amandeep , Singh Kanwar B.
Published: November 2017

This study presents a novel approach to analyze and fine-tune control system algorithms for semi-active suspension systems. In the case off road vehicles (example military vehicles), the ability of the suspension control system to keep the vehicle ride quality in an acceptable range is of paramount importance. Though limited in their intervention, semi-active suspensions are less expensive to design and consume far less energy in comparison to active suspension systems. In recent times, research in semi-active suspension systems has continued to advance with respect to their capabilities, narrowing the gap between semi-active and fully active suspension systems. This study investigates the usage of a semi-active suspension with a skyhook-groundhook hybrid controller. As a first step, sensitivity analysis of the controller performance to varying vehicle/road input parameters is conducted. This approach utilizes sensitivity analysis and one-factor-at-a-time method (OFAT) to find and reach the optimum point of vehicle suspension settings. Furthermore, real-time tuning of the mentioned controller is studied. Real-time tuning will help keep the ride quality of the vehicle close to its optimum point even during situations when the vehicle/road input parameters change. A quarter-car model is used for all the simulations and sensitivity analysis.
Nonlinear Tracking Control of an Antagonistic Muscle Pair Actuated System
Authors: Warner Holly , Richter Hanz , van den Bogert Antonie
Published: November 2017

When developing a machine intended for interaction with humans such as rehabilitation equipment or powered prostheses, it is useful to test in simulation prior to hardware implementation, avoiding safety hazards. Few models of the human for such purposes are seen in the literature. This paper moves toward the realization of such a model by developing a simple muscle-actuated system and related controller. The backstepping control methodology is implemented such that the controller accounts for all of the levels of intricacy presented by the Hill muscle model as an actuator, including the activation dynamics. The neural inputs are used as the actual controls. To be able to derive the control law, a modified strict-feedback form of the model is also developed. Stable tracking performance is then achieved in simulation.
Prognostics and Health Monitoring of Electro-Hydraulic Systems
Authors: Soudbakhsh Damoon , Annaswamy Anuradha M.
Published: November 2017

Electro-Hydraulic Systems (EHS) are commonly used in many industrial applications. Prediction and timely fault detection of EHS can significantly reduce their maintenance cost, and eliminate the need for redundant actuators. Current practice to detect faults in the actuators can miss failures with combination of multiple sources. Missed faults can result in sudden, unforeseen failures. We propose a fault detection technique based on Multiple Regressor Adaptive Observers (MRAO). The results were evaluated using a two-stage servo-valve model. The proposed MRAO can be used for on-line fault detection. Therefore, we propose a health monitoring approach based on the trend of the identified parameters of the system. Using the history of identified parameters, normal tear and wear of the actuator can be distinguished from the component failures to more accurately estimate the remaining useful life of the actuator.
Reducing Trajectory Tracking Error of Flexible Mobile Robots Using Command Shaping With Error-Limiting Constraints
Authors: Eaglin Gerald , Vaughan Joshua
Published: November 2017

The ability to track a trajectory without significant error is a vital requirement for mobile robots. Numerous methods have been proposed to mitigate tracking error. While these trajectory-tracking methods are efficient for rigid systems, many excite unwanted vibration when applied to flexible systems, leading to tracking error. This paper analyzes a modification of input shaping, which has been primarily used to limit residual vibration for point-to-point motion of flexible systems. Standard input shaping is modified using error-limiting constraints to reduce transient tracking error for the duration of the system’s motion. This method is simulated with trajectory inputs constructed using line segments and Catmull-Rom splines. Error-limiting commands are shown to improve both spatial and temporal tracking performance and can be made robust to modeling errors in natural frequency.
Analysis of the transient surface wave propagation in soft-solid elastic plates
Authors: Benech Nicolás , Brum Javier , Grinspan Gustavo , Aguiar Sofía , Negreira Carlos A.
Published: November 2017

In dynamic elastography, the goal is to estimate the Young's modulus from audio-frequency wave propagation in soft-tissues. Within this frequency range, the shear wavelength is centimeter-sized while the compressional wavelength is meter-sized. Thus, the experimental data are usually collected in the near-field of the source. Near-field effects have been widely studied for bulk wave propagation. However, the near- and transient-fields of surface and guided waves have received less attention. In this work, the transient surface displacement field in soft-solid elastic plates in vacuum is analyzed. Due to the high Poisson's ratio, mode conversion has special characteristics in soft-solids. They are analyzed through this work where it is shown that the transient-field over the surface can be interpreted by tracing a few reflections. The authors show the existence of a critical distance needed for the formation of Rayleigh-Lamb modes. Below this distance, only direct surface waves propagate without contribution from reflected waves. Thus, the dispersion curve differs from that predicted by Rayleigh-Lamb modes. Instead, the authors propose a model based on the interference of surface waves, which agree with the experimental data. In addition, the conditions needed in order to retrieve the shear wave phase velocity from the surface field are given.
Papers of note in
Science
358
(6364)
Authors: VanHook Annalisa M.
Published: November 2017

This week’s articles highlight a newly identified component of methionine sensing; a mechanism by which nutrient depletion prevents the efflux of essential amino acids from lysosomes; how reactive oxygen species promote genome stability during metabolic stress; co-option of the cell cycle regulatory machinery to time the differentiation of multiciliated cells; and connections between olfaction, organismal metabolism, and longevity.
Optimisation of intravenous fluid prescribing: framework for changing practice through education and audits
Authors: Forryan James , Mishra Vinita
Published: November 2017

Introduction

Intravenous fluids are one of the most commonly prescribed drugs in the hospital setting and yet the practice continues to fall short of National Institute for Health and Care Excellence (NICE) guidelines, with significant gaps in staff knowledge exposing patients to heightened morbidity and mortality.

Aim

Following the 2013 publishing of updated NICE guidelines on intravenous fluid prescribing, an intravenous fluid team was formed within the Royal Liverpool University Hospital (RLUH). Their role has been (and continues to be) to overhaul the culture of suboptimal intravenous fluid prescribing within the hospital and, ultimately, to improve patient outcomes. A framework to engender this change has been developed and is offered as an example to other Trusts within which improvement of guideline-compliant intravenous fluid prescribing remains stagnant.

Method

There have been three principal stages of the project to this point which are best demonstrated in a chronological manner. The period of 2010–2014 allowed for assessment of the issue of intravenous fluid prescribing and analysis of its causes through serial audits and a staff-wide survey. From 2015, there has been implementation of several measures (educative, managerial, administrative and technological) within the hospital to foster reproducible and positive change with regards to intravenous fluid prescribing. Finally, between 2016 and 2017, three cycles of a rolling audit based on NICE guidelines have been completed to allow measurement of improvement in intravenous fluid prescribing practice.

Conclusion

Results have demonstrated a significant improvement in the appropriateness of the intravenous maintenance and replacement fluids prescribed in the hospital since the March 2016 audit. Moreover, a 29-fold increase has been observed in the use of 4% dextrose/0.18% sodium chloride as maintenance fluid (gold standard as per NICE guidelines) since the staff-wide survey of 2015. Despite progress however, adherence to NICE guidelines remains below the recommended 100% and therefore further work remains to be done.
Impact of NaCl on drying shrinkage behavior of low-plasticity soil in earthen heritages
Authors: Zhang Yue , Ye Weimin , Chen Yonggui , Chen Bao
Published: November 2017

Cracking of wall surface crusts on salt-laden earthen remains at the site of Yar City, northwest China, is a serious concern. This widespread pathology is closely related to the drying shrinkage behavior of soil and the fundamental mechanisms should be investigated to better interpret the deterioration of these precious heritages. In this paper, tests were conducted on specimens that were initially slurries with NaCl contents of 0%, 2%, and 5%. The soil shrinkage characteristic curve (SSCC) was measured using the fluid displacement method during a slow air-drying process. The drying branch of the soil-water retention curve was also established by combining three common techniques (pressure plate, vapor equilibrium, and filter paper). The microstructure of specimens with varying water and NaCl contents was characterized through mercury intrusion porosimetry (MIP) testing. Results show that NaCl had negligible impact on the SSCC, which was composed of three shrinkage zones. With increasing NaCl content, matric suction was hardly influenced while the total suction increased significantly due to the pore fluid osmotic suction. The analysis indicated that drying shrinkage was actually a process of consolidation governed predominantly by matric suction. MIP test results were consistent with the macroscale observations for specimens that were initially slurries: that the total volume of pores decreased upon drying. In addition, pore-size distribution was unimodal and no significant difference was observed among specimens with different NaCl contents.
Clogging of pervious concrete pile caused by soil piping: an approximate experimental study
Authors: Cui Xinzhuang , Zhang Jiong , Chen Darhao , Li Shucai , Jin Qing , Zheng Yingjie , Cui Sheqiang
Published: November 2017

Due to their high permeability and high strength, pervious concrete piles (PCPs) can improve ground bearing capacity. However, clogging of pervious concrete in practice is a potential disadvantage. To investigate the clogging mechanism of PCPs due to sand piping, a series of laboratory simulation tests is conducted on a developed hydraulic conductivity test system. This testing demonstrates the effects of pervious concrete porosity, grading of fine movable particles, mix ratio of skeleton particles to movable particles, relative density of soil, and distance between PCPs on PCP clogging. The experimental test results show that the hydraulic conductivity of PCP decreases for approximately 70 min and then becomes relatively stable. In addition, it is observed that PCP clogging rarely occurs in cases of low pervious concrete porosity, small movable sand particle size, high sand relative density, and large pile distance. The results also show that measurement of electrical conductivity can be an alternative method of hydraulic conductivity measurement. Based on the test results, preliminary clogging models are proposed.