bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplex Methods for Optimal Control of Unmanned Aircraft Flight Trajectories
Authors: Zollars Michael D. , Cobb Richard G.
Published: November 2017

The feasibility of using a constrained Delaunay triangulation method for determining optimal flight trajectories of unmanned air vehicles in a constrained environment is explored. Current methods for developing optimal flight trajectories have yet to achieve computational times that allow for real-time implementation. The proposed method alleviates the dependency of problem specific parameters while eliminating constraints on the Non-Linear Program. Given an input of obstacles with n vertices, a constrained Delaunay triangulation is performed on the space. Converting the vertices of the triangulation to barycentric coordinates on a phased approach defines the state bounds and max time for each phase. With two-dimensional aircraft dynamics, direct orthogonal collocation methods are performed to compute the optimal flight trajectory. Results illustrate computational times and feasibility of Small Unmanned Aircraft System flight trajectories through polygon constraints.
Tristable Energy Harvesters With Asymmetric Potential Wells: Analytical Study
Authors: Zhou Shengxi , Zuo Lei
Published: November 2017

In order to reveal the nonlinear response characteristics of asymmetric tristable energy harvesters, this paper originally deduces their complete harmonic balance solutions. In addition, the Jacobian matrix for determining the stability of these analytical solutions is presented. Under different harmonic excitation conditions, the multi-solution response characteristics of asymmetric tristable energy harvesters are analyzed. In detail, asymmetric tristable energy harvesters are found to have seven solutions (four stable solutions) under the appropriate excitation condition. The influence mechanism of asymmetry of potential wells on tristable energy harvesting performance is studied. The results show that the potential barrier is a main factor to influence high-energy interwell oscillation orbit height, which determines the output voltage amplitude and the overall energy harvesting performance. The influence essence of asymmetry for tristable energy harvesters is to change their potential wells and adjust the distribution of their potential barriers.
Collision Cone Based Lane Changing Model for Collision Avoidance
Authors: An Gihyeob , Langari Reza
Published: November 2017

In this paper, we propose a lane changing model based on the collision cone approach. Specifically, we show how a vehicle decides whether to change lanes using the collision cone algorithm based on the information of the velocity and the location of surrounding vehicles. The model compares the current and target lane with a new measure of driving advantages. It determines if there are any existing driving advantages such as free space and speed by lane changing. Moreover, a new methodology of lane changing for collision avoidance, which is based on line of sight (LOS) with a new leader in a target lane, is suggested with a model predictive control (MPC) controller. Additionally, we show that the model makes reliable decisions and generates acceptable lane changing trajectories.
Optimization and Design Principles of a Minimal-Weight, Wearable Hydraulic Power Supply
Authors: Nath Jonathan D. , Durfee William K.
Published: November 2017

The field of wearable hydraulics for human-assistive devices is expanding. One of the major challenges facing development of these systems is creating lightweight, portable power units. This project’s goal was to develop design strategies and guidelines with the use of analytical modeling to minimize the weight of portable hydraulic power supplies in the range of 50–300 W. Steady-state, analytical models were developed and validated for a system containing a lithium-polymer battery, brushless DC motor, and axial-piston pump. Component parameters such as motor size, pump size, and swashplate angle were varied to explore and develop four main design guidelines that can be used by designers to minimize overall system weight. First, it is often not beneficial to select the smallest sized electric motor that can provide the required torque and speed. Second, cooling systems generally do not help reduce overall system weight. Third, the gearbox between the electric motor and pump should be eliminated to reduce system weight. Fourth, iterative modeling is necessary to determine the various range of particular component parameters necessary to result in a minimal-weight system. The analytical model developed takes inputs of desired flowrate, pressure, and runtime, and outputs the combination of pump size, swashplate angle, and motor size that results in a minimal-weight system. The four design principles and the computer simulation are tools that can be used to either design a fully custom, weight-optimized power supply or to aid in the selection of commercially available components for a low-weight power supply.
A Single Leg Model With a Novel Variable Stiffness Element Based on the Dynamics Analysis and its Dynamic Characteristics
Authors: Li Zhang , Tan Yuegang , Hong Liu , Dhupia Jaspreet Singh , Zeng Shun , Huang Linkao
Published: November 2017

This paper presents a bio-inspired dynamic leg model with a novel variable stiffness element to create a normal body motion during stance phase. The variable stiffness in the model is implemented through structure-controlled stiffness. It allows to decouple the stiffness from joint motion, which makes the stiffness a independent variable. Sensitivity of leg model to the variable stiffness element is investigated through dynamics analysis. Because of the decoupled structure of dynamics equations, the deflection of ankle joint related to variable stiffness element is planned based on generalized forced vibration motion in order to create the leg’s motion. A detailed study to investigate the dynamic characteristics under different generalized vibration parameters, and the desired variable stiffness function are evaluated. It is found that under the effects of variable stiffness, the ground reaction forces of leg model during stance motion have similar characteristics to those observed for mammals. Furthermore, in order to create a normal motion during stance phase, linear stiffness variation characteristics and small stiffness range are needed for the proposed variable stiffness actuator.
Simulation Research on Dynamic Coordinated Control of Engine-Motor in Dual-Mode Power-Split Hybrid System
Authors: Zhao Wenqiang , Huang Ying , Zhao Yu , Ge Yanwu , Li Huan
Published: November 2017

For hybrid electric vehicles, there are output shaft torque fluctuations during the working condition switching process, which reduce the driving comfort of the vehicle. Therefore, corresponding control is necessary to eliminate the torque fluctuations. In this paper, for a dual-mode power-split hybrid system, the steady state energy management strategy under the typical power flow in two modes is studied and an operational condition switching control strategy based on engine torque control and motor speed control is proposed for the system characteristics. Meanwhile, the reason for fluctuations on the switching process based on engine torque control is found out to be the too large inertia moment in the coupling power mechanism. Considering the characteristics of fast speed and torque response of the motor, dynamic coordinated control strategy is proposed to eliminate the torque fluctuations and improve the accuracy of the actual torque relative to the target torque for the two models (i.e., the motor torque compensation control strategies). The model of dual-mode hybrid system was built and the simulation results show that the proposed control strategy has a positive effect on eliminating the torque fluctuations and the target torque of the driver can be accurately tracked.
Resilient Control of Linear Time-Invariant Networked Multiagent Systems
Authors: Peterson J. Daniel , De La Torre Gerardo , Yucelen Tansel , Tran Dzung , Dogan K. Merve , McNeely Drew
Published: November 2017

A local state emulator-based adaptive control law is proposed for multiagent systems with agents having linear time-invariant dynamics. Specifically, we present and analyze a distributed adaptive control architecture, where agents achieve system-level goals in the presence of exogenous disturbances. Apart from existing relevant literature that makes specific assumptions on network topologies, agent dynamics, and/or the fraction of agents subjected to disturbances, the proposed approach allows agents to achieve system-level goals — even when all agents are subject to exogenous disturbances. Several numerical examples are provided to demonstrate the efficacy of our approach.
A New Result on Distributed Input and State Estimation for Heterogeneous Sensor Networks
Authors: Tran Dzung , Yucelen Tansel , Jagannathan Sarangapani
Published: November 2017

An important research area in sensor networks is the design and analysis of distributed estimation algorithms for dynamic information fusion in the presence of heterogeneity resulting from (i) nonidentical information roles of nodes and (ii) nonidentical modalities of nodes. In particular, (i) implies that both active (i.e., subject to observations of a process of interest) and passive (i.e., subject to no observations) nodes can be present in the sensor network. Furthermore, (ii) implies that active nodes can observe different measurements from a process (e.g., a subset of active nodes can observe position measurements and the rest can observe velocity measurements for a target tracking problem). In this paper, we focus on heterogeneous sensor networks, sensor networks with (i) and (ii), and present a new distributed input and state estimation approach. In addition to the presented theoretical contribution including the stability and performance of the proposed estimation approach, an illustrative numerical example is also given to demonstrate its efficacy.
An Observer-Free Output Feedback Cooperative Control Architecture for Multivehicle Systems
Authors: Albattat Ali , Yucelen Tansel , Gruenwald Benjamin C. , Jagannathan S.
Published: November 2017

The contribution of this paper is a new, observer-free output feedback cooperative control architecture for continuous-time, minimum phase, and high-order multivehicle systems in the context of a containment problem (i.e., outputs of the follower vehicles convergence to the convex hull spanned by those of the leader vehicles). The proposed architecture is predicated on a nonminimal state-space realization that generates an expanded set of states only using the filtered input and filtered output and their derivatives for each follower vehicle, without the need for designing an observer for each vehicle. Specifically, the proposed observer-free output feedback control law consists of a vehicle-level controller and a local cooperative controller for each vehicle, where the former addresses internal stability of vehicles and the latter addresses the containment problem. Two illustrative numerical examples complement the proposed theoretical contribution.
A New Powertrain Design Approach for Power-Split Hybrid Tracked Vehicles
Authors: Qin Zhaobo , Luo Yugong , Li Keqiang , Peng Huei
Published: November 2017

Powertrain design for power-split hybrid vehicles using planetary gears has been widely researched. As proved, the total number of candidate designs is large due to the diversity of connection ways between devices and planetary gears. In this paper, a new powertrain design approach is developed and applied to power-split hybrid tracked vehicles. The three-step approach that uses constraint-based configuration selection, automated dynamic modeling, drivability screening and fuel economy screening can further reduce computation load and rapidly converge to superior designs. A case study is conducted to identify better designs compared with current designs for hybrid tracked dozers.
Optimal Control of a Hydrostatic Wind Turbine Drivetrain for Efficiency Improvements
Authors: Deldar Majid , Anwar Sohel
Published: November 2017

To increase productivity of a wind power plant, the overall loss of its drivetrain should be minimized. For hydrostatic transmission wind turbine (HTSWT), aerodynamic efficiency of the rotor and the hydrostatic efficiency of pump and motor determine the overall loss. In this study, optimal control theory is utilized to develop a control law that minimizes the overall loss. A nonlinear model is considered for the drivetrain and a performance index (PI) is defined for the overall loss subject to system constraints which were then used to derive the optimal control law based on Pontryagin Minimum Principle (PMP),. Simulation results verified that the controller was able to maximize the drive-train efficiency. At very low wind speed, a trade-off is observed between aerodynamic and hydrostatic efficiency. For higher wind speed where the hydrostatic efficiency asymptotically reaches its maximum efficiency maximum output power coincided with maximum power point tracking of input wind power.
Modeling and Validation of a Constant Flux Magnetostrictive Impact Sensor
Authors: Weld Kevin , Uras Mehmet , Ulsoy A. Galip
Published: November 2017

A constant flux magnetostrictive impact sensor is presented along with a discussion of prior applications and previous work on modeling of magnetostrictive sensors. A constant flux magnetostrictive impact sensor, which uses a permanent magnet, is modeled and the system in which it operates is overviewed. A detailed analytical model of the operation of the constant flux magnetostrictive impact sensor is developed. Prototype sensors were tested in both dynamic gap and magnetostrictive modes of operation. The model is validated through comparison of modeling and experimental results.
Trajectory Tracking Control for a Robotic Manipulator Using Nonlinear Active Disturbance Rejection Control
Authors: Ali Mohammed , Alexander Charles K.
Published: November 2017

The tracking performance of a robot manipulator is controlled using nonlinear active disturbance rejection control (ADRC). The proposed method does not require the complete knowledge of the plant’s parameters, and external disturbances since it is based on the rejection and estimation of the unknown internal dynamics and external disturbances. The proposed method is simple and has minimal tuning parameters. The robustness of the proposed method is discussed against parameter uncertainties and disturbances. First, the mathematical model of the manipulator is developed. ADRC theory is explained. The manipulator is represented in ADRC form. ADRC’s tracking performance for the joints and end-effector is compared to the tracking performance of the robust passivity (RP) control. The simulations prove that the proposed control method achieves good tracking performance compared to RP control. It is shown that ADRC has a lower energy consumption compared to RP control by calculating the power in the input signals.
SCR Control System Design Based on On-Line Radial Basis Function and Backpropagation Neural Networks
Authors: Sui Wenbo , Hall Carrie M.
Published: November 2017

Because of its high NOx reduction efficiency, selective catalyst reduction (SCR) has become an indispensable part of diesel vehicle aftertreatment. This paper presents a control strategy for SCR systems that is based on an on-line radial basis function neural network (RBFNN) and an on-line backpropagation neural network (BPNN). In this control structure, the radial basis function neural network is employed as an estimator to provide Jacobian information for the controller; and the backpropagation neural network is utilized as a controller, which dictates the appropriate urea-solution to be injected into the SCR system. This design is tested by simulations based in Gamma Technologies software (GT-ISE) as well as MATLAB Simulink. The results show that the RBF-BPNN control technique achieves a 1–5 % higher NOx reduction efficiency than a PID controller.
Identification of Resonance Frequencies in Dual-Stage Hard Disk Drives: A Practical Strategy
Authors: Zheng Minghui , Zhou Shiying , Tomizuka Masayoshi
Published: November 2017

In hard disk drives (HDDs), there exist multiple mechanical resonances whose central frequencies may shift due to the change of environmental conditions such as the temperature. Such slowly varying resonance frequencies, if not handled properly, may degrade the positioning accuracy and even result in the instability of the closed-loop HDD system. Therefore, it is important to identify these resonance frequencies efficiently without interrupting the reading/writing process in HDDs. One main challenge of the frequency identification in a dual-stage HDD lies in the fact that it is a double-input-single-output (DISO) system. The outputs of the voice coil motor (VCM) and the piezoelectric microactuator (PZT) are coupled together. This paper proposes a practical strategy to identify the resonance frequencies in both the VCM and the PZT without disabling the PZT control process. Bandpass filters are utilized to separate the overall position error signal (PES) into several frequency segments based on priorly-known frequency range for each resonance. Two standard parameter adaptation algorithms are studied and discussed. Simulation results validate the effectiveness of proposed identification strategy.
Regenerative Base Isolation With Multi-Resonant Electromagnetic Shunt Dampers
Authors: Pei Yalu , Liu Yilun , Zuo Lei
Published: November 2017

Electromagnetic (EM) shunt damping has been recently proposed for dual-functional vibration isolation and energy harvesting. This paper proposed two multi-resonant electromagnetic shunt damper configurations, namely in parallel and in series, with application to the building base isolation system. The electromagnetic shunt circuit parameters were optimized based on the H2 criteria to minimize the RMS relative displacement for the concern of building safety subjected to broad bandwidth ground acceleration excitations. The performance of the proposed multi-resonant electromagnetic shunt dampers was compared with traditional multiple tuned mass dampers (TMDs). It shows that, for multiple TMDs and multi-resonant electromagnetic shunt dampers with 5% total stiffness ratio, the parallel electromagnetic shunt damper can achieve the best vibration isolation performance. Case study of a base-isolated structure was analyzed in both the time and frequency domain to investigate the effectiveness of the multimode electromagnetic shunt resonances. It shows that both multimode shunt circuits outperform the single mode shunt circuit by suppressing the primary and the second vibration modes simultaneously. Comparatively, the parallel shunt damper is more effective in vibration isolation and energy harvesting, and is also more robust in parameter mistuning than the series shunt damper. This paper further experimentally validated the effectiveness of the multi-resonant electromagnetic shunt damper on a scaled-down base-isolated building.
Multiform Adaptive Robot Skill Learning From Humans
Authors: Zhao Leidi , Lawhorn Raheem , Patil Siddharth , Susanibar Steve , Lu Lu , Wang Cong , Ouyang Bo
Published: November 2017

Object manipulation is a basic element in everyday human lives. Robotic manipulation has progressed from maneuvering single-rigid-body objects with firm grasping to maneuvering soft objects and handling contact-rich actions. Meanwhile, technologies such as robot learning from demonstration have enabled humans to intuitively train robots. This paper discusses a new level of robotic learning-based manipulation. In contrast to the single form of learning from demonstration, we propose a multiform learning approach that integrates additional forms of skill acquisition, including adaptive learning from definition and evaluation. Moreover, going beyond state-of-the-art technologies of handling purely rigid or soft objects in a pseudo-static manner, our work allows robots to learn to handle partly rigid partly soft objects with time-critical skills and sophisticated contact control. Such capability of robotic manipulation offers a variety of new possibilities in human-robot interaction.
Casimir Effect on Frequency Response of Superharmonic Resonance of NEMS Resonators
Authors: Botello Martin , Reyes Christian , Beatriz Julio , Caruntu Dumitru I.
Published: November 2017

This paper investigates the frequency response of superharmonic resonance of the second order of electrostatically actuated nano-electro-mechanical system (NEMS) resonator sensor. The structure of the MEMS device is a resonator cantilever over a ground plate under Alternating Current (AC) voltage. Superharmonic resonance insinuates that the AC voltage is operating in a frequency near one-fourth the natural frequency of the resonator. The forces acting on the system are electrostatic, damping and Casimir force. For the electrostatic force, the AC voltage is in the category of hard excitation in order to induce a bifurcation phenomenon. For Casimir forces to affect the system, the gap distance between the cantilever resonator and base plate is in the range of 20 nm to 1 μm. The differential equation of motion is converted to dimensionless by choosing the gap as reference length for deflections, the length of the resonator for the axial coordinate, and reference time based on the characteristics of the structure. The Method of Multiple Scales (MMS) is used to model the characteristic of the system. MMS transforms the nonlinear partial differential equation of motion into two simpler problems, namely zero-order and first-order. The influences of parameters (i.e. Casimir, damping, second voltage and fringe) were also investigated.
Parametric Resonance of Electrostatically Actuated MEMS Cantilever Resonators Using Method of Multiple Scales and Homotopy Perturbation Method
Authors: Reyes Christopher , Caruntu Dumitru I.
Published: November 2017

This paper investigates the dynamics governing the behavior of electrostatically actuated MEMS cantilever resonators. The cantilever is held parallel to a ground plate (electrode) with an AC voltage between the plate and the electrode causing the electrostatic actuation (excitation). For the purposes of this paper this is soft excitation. The frequency of the excitation is near the natural frequency of the cantilever leading to what is known as parametric resonance. The electrostatic force in the problem investigated throughout the paper is nonlinear in nature and includes the fringe effect. Two methods are used in investigating this problem: the method of multiple scales (MMS) and the homotopy perturbation method (HPM). The two methods work well for small non-linearities and small amplitudes. The influence of voltage, fringe, damping, Casimir, and Van der Waals parameters will be investigated in this paper using MMS and HPM as a means of verifying the results obtained.
Dynamic Modelling of Updraft Gasifiers: Incidence of Feedstock Quality and Operational Variables in the Transient Model Structure
Authors: Narváez Cueva Ricardo , Blanchard R. , Guerrón G. , Chulde Diego , Dixon R.
Published: November 2017

This paper describes the definition of the transient model structure for an updraft gasifier and the input variables related to the process and the feedstock quality with the most significant influence on the dynamic models and the transient behaviour.

For such purpose, a set of open-loop dynamics experiments were carried out in the gasifier. Moreover, the output variables performance was recorded together with the composition analysis of the municipal solid waste batch (MSW).

The output and operational variables record was used as base information for performing regressions of transient models with the purpose of determining the model type choice that achieves the largest occurrence frequency of fitting percentage figures above 50%. In addition, the dataset of regression parameters is analysed through feature selection in order to establish the influence of feedstock quality parameters and independent dynamic operational variables in dynamic changes.

The model structure selection determined that underdamped, second order with one zero transfer function (P2ZU) is the most accurate case for updraft gasifiers.

Regarding the influence of feedstock-related information, feature selection results show that ultimate composition is the group of quality parameters with the most significant influence on transient behaviour.

Results also show that recirculation flow rate is the operational variable whose effect in the output variables is the most likely to be predicted and potentially controlled. The results for this variable show that 64.3% of the performed regressions achieved a fitting percentage value above 50%.
Vehicle Rollover Prevention Through a Novel Active Rollover Preventer
Authors: Wang Fengchen , Chen Yan
Published: November 2017

To assist vehicle rollover prevention and enhance vehicle roll motion safety, this paper proposes a novel active rollover preventer (ARPer) system, which consists of an in-wheel motor system moving along an orbit at the back of a vehicle. The roll and lateral dynamics of the vehicle equipped with the ARPer are modeled and mechanics analysis of the ARPer is presented as well. Based on the developed models, a Lyapunov nonlinear controller is designed for tracking a desired roll angle and a yaw rate when the impending rollover is detected. For a typical fishhook maneuver, two simulation cases are studied for different vehicle roof cargo loads, which represents different vehicle rollover properties without control. The CarSim®-Simulink co-simulation results show that compared with active front steering and differential braking control strategies, the APRer can successfully prevent the rollover propensity and maintain the vehicle lateral stability simultaneously.
Vehicle Lateral Motion Control Based on Estimated Stability Regions
Authors: Huang Yiwen , Chen Yan
Published: November 2017

This paper presents a novel vehicle lateral stability control method based on an estimated lateral stability region on the phase plane of vehicle yaw rate and lateral speed, which is obtained through a local linearization method. Since the estimated stability region does not only describe vehicle local stability, but also define the oversteering and understeering characteristics, the proposed control method can achieve both local stability and vehicle handling stability. Considering the irregular geometric shape of the estimated stability region, a stability analysis algorithm is designed to determine the distance between vehicle states and stability region boundaries. State estimation or measurement errors are also incorporated in the distance calculation. Based on the calculated shortest distance between vehicle states and stability boundaries, a direct yaw moment controller is designed to maintain vehicle states stay within the stability region. CarSim® and Simulink® co-simulation is applied to verify the control design through a cornering maneuver. The simulation results show that the proposed control method can make the vehicle stay within the stability region successfully and thus always operate in a safe manner.
Data Collection for Robust End-to-End Lateral Vehicle Control
Authors: Geist A. René , Hansen Andreas , Solowjow Eugen , Yang Shun , Kreuzer Edwin
Published: November 2017

This paper proposes a strategy for collecting road frames and steering data for training deep end-to-end control policies for robust lateral vehicle control. During the data collection phase, one camera is deployed in the vehicle and two steering controllers are operated simultaneously. While one controller operates in closed-loop and keeps the vehicle on a desired perturbed trajectory, a second controller computes the nominal steering wheel angle required to drive the vehicle to the center of the desired lane. With this approach, it is possible to train a convolutional neural network to act as an end-to-end lateral vehicle controller that is capable of rejecting unforeseen disturbances. We implement our approach by incorporating the deep learning framework Caffe and the vehicle simulation software TORCS in Matlab/Simulink and analyze the robustness of the trained end-to-end control policy in closed-loop simulations.
Design of Propulsive Virtual Holonomic Constraints for Planar Snake Robots
Authors: Mohammadi Alireza
Published: November 2017

Virtual holonomic constraints (VHCs) framework is a recent control paradigm for systematic design of motion controllers for wheel-less biologically inspired snake robots. Despite recent developments for VHC-based control systems for ground and underwater robotic snakes, they employ only two families of propulsive virtual holonomic constraints, i.e., lateral undulatory and eel-like virtual constraints. In this paper we extend the family of propulsive virtual constraints that can be used with VHC-based controllers by presenting a VHC analysis and synthesis methodology for planar snake robots that are subject to ground friction forces. In particular, we present a nonlinear differential inequality that guarantees forward motion of planar snake robots under the influence of VHCs. Furthermore, we provide a family of hyperbolic partial differential equations that can be employed to generate propulsive virtual holonomic constraints for these biologically inspired robots. Simulations are presented to verify the proposed analysis/synthesis methodology.
A Design Optimization Model for an Alternating Flow (AF) Hydraulic Pump Based on First Principles
Authors: Li Mengtang , Foss Ryan , Stelson Kim A. , Van de Ven James D. , Barth Eric J.
Published: November 2017

Although current state of the art hydraulic variable displacement pumps are highly efficiently at high displacement, they have poor efficiency at low displacement. Besides, different operating speed and load pressure conditions also strongly affect their performance. This paper proposed a novel alternating flow (AF) hydraulic variable displacement pump to 1) eliminate throttling loss by acting as a high-bandwidth pump for displacement control, 2) achieve high efficiency across a wide range of operating conditions and displacements, and 3) allow multiple units to be easily common-shaft mounted for a compact multi-actuator displacement control system from a single prime-mover. This paper presents a simple closed form model for the AF hydraulic pump and shows the model validation with a first generation prototype. The simple closed form model captures input motor energy, output fluid energy and associated energy losses. With the closed form model validated, it can then be used to drive optimal design for future generation prototypes using a dimensionless group method.
An Inverse-Free Disturbance Observer for Adaptive Narrow-Band Disturbance Rejection With Application to Selective Laser Sintering
Authors: Jiang Tianyu , Xiao Hui , Chen Xu
Published: November 2017

Selective laser sintering (SLS) is an additive manufacturing (AM) process that builds 3-dimensional (3D) parts by scanning a laser beam over powder materials in a layerwise fashion. Due to its capability of processing a broad range of materials, the rapidly developing SLS has attracted wide research attention. The increasing demands on part quality and repeatability are urging the applications of customized controls in SLS. In this work, a Youla-Kucera parameterization based forward-model selective disturbance observer (FMSDOB) is proposed for flexible servo control with application to SLS. The proposed method employs the advantages of a conventional disturbance observer but avoids the need of an explicit inversion of the plant, which is not always feasible in practice. Advanced filter designs are proposed to control the waterbed effect. In addition, parameter adaptation algorithm is constructed to identify the disturbance frequencies online. Simulation and experimentation are conducted on a galvo scanner in SLS system.
Developing Moving Horizon Estimation Based Ranging Measurement for Supporting Vision-Aided Inertial Navigation System
Authors: Nguyen Trung , Mann George K. I. , Vardy Andrew , Gosine Raymond G.
Published: November 2017

The objective of this paper is to develop an advanced Vision-and-Ranging-aided Inertial Navigation System (VRINS), which combines a Vision-aided Inertial Navigation System (VINS) with Moving Horizon Estimation (MHE) based ranging measurement update. The traditional VINS estimate suffers the error accumulation from the camera observation, which makes the system diverge and fails to track the vehicle trajectory in long-term operation. Hence, a ranging sensor is integrated with VINS in the sequential-sensor-update structure, which allows the filter to operate for longer duration. The ranging measurement update is developed with the MHE, which directly incorporates the system constraints into the optimization process. The VINS is developed with Cubature Multi-State Constraint Kalman Filter (MSCKF), which has 30-dimension filter state, tight constraints of state transition and observability. Those elements need to be considered in the design of MHE optimization. The implementation of MHE is conducted with CASADI library. The proposed VRINS will be validated using KITTI dataset and compared against the VINS.
Limitations of Torque Vectoring As a Backup Safety Strategy for Steer-by-Wire Vehicles due to Vehicle Stability Control
Authors: Kirli Ahmet , Okwudire Chinedum E. , Ulsoy A. Galip
Published: November 2017

There is growing interest in steer-by-wire (SBW) systems because they provide significant benefits to classical vehicles, and are indispensable to autonomous vehicles. However, an emergency backup strategy is needed to steer a vehicle to safety if its SBW actuators fail completely. Differential drive assisted steering (DDAS), which uses torque vectoring to steer a vehicle, has been proposed as a backup strategy for SBW systems. However, vehicle stability control (VSC) — a required feature in most modern vehicles — also relies on torque vectoring. This paper demonstrates, for the first time, through simulations, that conflicts may arise between VSC and DDAS, rendering DDAS ineffective as a SBW system backup strategy. This preliminary study motivates the need to pay attention to, and develop strategies for addressing these conflicts. As an example, the addition of speed control to DDAS is shown as a potential strategy for mitigating these conflicts.
A Generalized Approach for Commercial and Industrial Load Shifting Control
Authors: Rogers Austin , Rasmussen Bryan
Published: November 2017

Load shifting is one means whereby buildings may reduce their peak demand and provide other services to the electric grid. Current rate tariffs penalize facility peak demand, and large commercial and industrial buildings may realize cost savings by reducing this facility peak demand. The successful shifting of electric load requires some knowledge or prediction of the peak demand. This prediction is generally imperfect, and the resulting load shifting control is sub-optimal. This paper develops the optimal load shifting operations using a battery energy storage system under certain assumptions. This optimal solution is then used to develop a generalized strategy for load shifting battery control with the purpose of reducing peak 15-minute demand. This generalized strategy involves a prediction of the target demand level and a prediction of the current 15 minute period. The method whereby these predictions are made is critical to the success of load shifting. The general control logic may be used to analyze the sensitivity of load shifting to prediction error and sampling rate..
Wind Turbine Collective and Individual Pitch Control Using Quantitative Feedback Theory
Authors: Wheeler Laura H. , Garcia-Sanz Mario
Published: November 2017

Individual pitch control is an innovative technique in wind turbine control. It has the potential of reducing the asymmetric mechanical loads on the blades in large multi-megawatt turbines. As the mechanical fatigue is reduced, the lifetime of the turbine can be significantly extended. This work develops an individual pitch control for the National Renewable Energy Laboratory’s (NREL) 5 MW reference wind turbine. The individual pitch controller works along with a collective pitch controller, designed using Quantitative Feedback Theory (QFT) robust control. Simulations of the complete individual and collective pitch control system are conducted with the NREL’s computer-aided engineering tool for horizontal axis wind turbines (FAST). They show that the addition of the individual pitch controller significantly reduces the loads on the tilt and yaw directions in the nacelle and tower of the turbine at 1P and 3P frequencies, and on the blades at the 2P harmonic frequency.
Mechanical Motion Rectifier Based Efficient Power Takeoff for Ocean Wave Energy Harvesting
Authors: Yin Xiuxing , Li Xiaofan , Boontanom Vicky , Zuo Lei
Published: November 2017

This paper proposes a novel mechanical-motion-rectifier (MMR) based power-takeoff (PTO) for ocean wave energy harvesting. The proposed PTO directly converts irregular oscillatory wave motion into regular unidirectional rotation of the generator. It is mainly composed of two ball screws, three bevel gears, two one-way clutches, and a generator. The two one-way clutches and the bevel gears change the bi-directional rotation of the two ball screws into unidirectional ration of the generator. The MMR rectifies the irregular reciprocating motion into unidirectional rotation; similar to the way the electric voltage rectifier regulates an AC voltage. The proposed PTO can be integrated into a heaving point wave energy converter (WEC). The dynamics and modelling of the PTO are presented. The frequency-domain dynamics of the WEC are then formulated for operating condition and control. The power generation capability of the proposed WEC has been evaluated in MATLAB and WAMIT. The simulation results demonstrate that the power generation capability can be improved by using the MMR method.
Control and Design Optimization of a Novel Hybrid Electric Powertrain System
Authors: Yi Chenyu , Epureanu Bogdan
Published: November 2017

Control and design optimization of hybrid electric powertrains is necessary to maximize the benefits of novel architectures. Previous studies have proposed multiple optimal and near-optimal control methods, approaches for design optimization, and ways to solve coupled design and control optimization problems for hybrid electric powertrains. This study presents control and design optimization of a novel hybrid electric powertrain architecture to evaluate its performance and potential using physics-based models for the electric machines, the battery and a near-optimal control, namely the equivalent consumption minimization strategy. Design optimization in this paper refers to optimizing the sizes of the powertrain components, i.e. electric machines, battery and final drive. The control and design optimization problem is formulated using nested approach with sequential quadratic programming as design optimization method. Metamodeling is applied to abstract the near-optimal powertrain control model to reduce the computational cost. Fuel economy, sizes of components, and consistency of city and highway fuel economy are reported to evaluate the performance of the powertrain designs. The results suggest an optimal powertrain design and control that grants good performance. The optimal design is shown to be robust and non-sensitive to slight component size changes when evaluated for the near-optimal control.
Autonomous Mobile Sensing Platform for Spatio-Temporal Plant Phenotyping
Authors: Saha Homagni , Gao Tianshuang , Emadi Hamid , Jiang Zhanhong , Singh Arti , Ganapathysubramanian Baskar , Sarkar Soumik , Singh Asheesh , Bhattacharya Sourabh
Published: November 2017

This paper presents the design, modeling, control and navigation for a novel ground-based mobile sensing platform that can collect multi-modal data in agricultural research farms for high throughput modular plant phenotyping. The platform will have the following capabilities (i) Navigate in a row-crop farm to collect data with minimal human intervention during operation (ii) Autonomous decision making i.e, it can take its own decisions for maximizing the value of information of the acquired data and (iii) Scalable in terms of the size of the farmland. The design requirements for such a platform or robot is formulated, and a detailed discussion on realizing such a design is presented. The dynamics of the robot is presented in the state space form and it is abstracted in the form of a control flow diagram for the automatic steering system. An adaptive sampling approach has been taken to generate an estimated belief-space which is leveraged in the proposed opportunistic sensing scheme to generate way-points for navigation.
High Frequency Analysis of a Dynamically Coupled Parallel Plate System
Authors: Culver Dean R. , Dowell Earl
Published: November 2017

The behavior of a system comprised of two parallel plates coupled by a discrete, linear spring and damper is studied. Classical Modal Analysis (CMA) is used to illustrate this behavior, while specifically observing the effects of varying the stiffness and damping ratio of the coupling elements. Conditions under which the coupling may be approximated as rigid are identified. Additionally, conditions under which the coupling displacement reaches its maximum and minimum values are identified. This work also lays the groundwork for extending Asymptotic Modal Analysis (AMA) to systems with discrete, elastic, and dissipative coupling.
Nonlinear Robust Path Control for a Field Robot Scouting in Strawberry Orchards
Authors: Freese Douglas , Xu Yunjun
Published: November 2017

In recent years, the interests of introducing autonomous robots by growers into agriculture fields are rejuvenated due to the ever-increasing labor cost and the recent declining numbers of seasonal agricultural workers. Among all the enabling technologies used in robot operations for agricultural products with shallow structures, controlling a robot to traverse throughout a field is challenging. In this study the motion control of a robot, custom-designed for strawberry fields, is separated into multiple phases to deal with the over-bed and cross-bed operation needs. Different sensors are used for different control phases. In particular, nonlinear robust controllers are designed for the cross-bed motion, purely relying on vision feedback. The proposed sensing and control methods are successfully validated in a commercial farm.
Optimization of Wind Turbine Torsional Mitigation Procedures for Different Generator Classes
Authors: White Warren N. , Currence Justin , Aththanayaka Buddhika , Fateh Fariba , Gruenbacher Don
Published: November 2017

Wind turbine vibrations can result from periodic excitation caused by the wind and by both wind and seas for the case of offshore units. In particular, the turbine drivetrain is subject to torsional vibrations caused by both changes in the wind and grid disturbances. This paper uses a collection of different control schemes to damp the vibrations and seeks the best controller by optimizing each in terms of gain selection. Two 750 kW wind turbine models, one with a DFIG (doubly fed induction generator) and the other with a PMSG (permanent magnet synchronous generator) are used in the investigation. Numerical simulations of the wind turbines using the NREL developed software FAST 8 are the means of conducting the tests. In varying the gains, the work discovers that the best controller for a DFIG differs greatly from the best controller for a PMSG. In addition, the work found that the vibration damping in a DFIG turbine is different when the source of the vibration-causing disturbance is considered. The paper reports both the optimized gains and a set of questions raised by the behavior of the DFIG turbine where the response of the shaft torsion differs according to the source of the disturbance, i.e. either grid side or wind side.
An Improved Dynamic Friction Model Using a Data-Based Approach
Authors: Weir Nathan A. , Alleyne Andrew G.
Published: November 2017

A significant challenge associated with the development of precision motion control systems is the identification and modeling of friction. In particular, dynamic (presliding) friction is often difficult to accurately model in both the time domain and frequency domain simultaneously. We present a data-based modification to an existing friction model, known as the Dahl Dynamic Hysteresis Model (DHM), which incorporates an empirical friction slope function to provide a more accurate representation of arbitrarily shaped hysteresis curves. This data-based approach avoids the added complexity of identifying or fitting model parameters, and can be implemented with a simple look up table. Simulation results are validated with measured friction data collected from an experimental testbed. We show that the data-based approach significantly improves the friction model accuracy in both the time and frequency domains.
Qualitative and Quantitative Study of the Flow Physics in the Vicinity of an Oscillating Plate in Viscous Fluids
Authors: Shrestha Bishwash , Ahsan Syed N. , Aureli Matteo
Published: November 2017

In this paper, we report on a comprehensive experimental study on the fluid-structure interactions of a submerged rigid plate undergoing harmonic oscillations in a quiescent, Newtonian, viscous fluid. We conduct a detailed qualitative and quantitative analysis of the problem for broad ranges of oscillation parameters, including frequency and amplitude, to highlight the fluid-structure interaction mechanisms responsible for the hydrodynamic forces acting on the plate. The primary objective of this study is to understand the effect of the oscillation parameters on the resulting qualitative flow patterns and analyze their relation with vortex shedding and hydrodynamic forces. We classify different flow regimes depending on the behavior of the flow in the vicinity of the structure, with particular focus on vortex shedding and symmetry breaking phenomena, and analyze the forces in each regime by using particle image velocimetry and direct force measurement via a load cell. Comparison of the obtained experimental results against values predicted from numerical and semi-analytical models shows good agreement between our approach and the literature. Fundamental findings from this work have direct relevance to various engineering applications, including energy harvesting devices, biomimetic robotic system, and micro-mechanical sensors and actuators.
Placing Minimum Phase Zeros to Shape Transient Response: Generalization From Control of Hybrid Power Systems
Authors: Salih Bilal S. , Das Tuhin K.
Published: November 2017

Conservation of energy can be applied in designing control of hybrid power systems to manage power demand and supply. In practice, it can be used for designing decentralized controllers. In this paper, this idea is analyzed in a generalized theoretical framework. The problem is transformed to that of using minimum phase zeros to generate a specific type of transient response admitted by dynamical systems. Here, the transient step response is shaped using an underlying conservation principle. In this paper, emphasis is placed on second order systems. However, the analysis can be extended to higher order transfer functions. Analytical results relating zero location to the matched/ mismatched areas of the transient response are established for a class of second order systems. A combination of feedback and feedforward actions are shown to achieve the desired zero placement/addition and the desired transient response. The proposed analysis promises extension to nonlinear systems. Optimization studies also seem appropriate, especially for higher order transfer functions.