Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME

Small unmanned aerial vehicles (UAVs) have the potential to revolutionize various applications in civilian domain such as disaster management, search and rescue operations, law enforcement, precision agriculture, and package delivery. As the number of such UAVs rise, a robust and reliable traffic management is needed for their integration in national airspace system (NAS) to enable real-time, reliable, and safe operation. Management of UAVs traffic in NAS becomes quite challenging due to issues such as real-time path planning of large number of UAVs, communication delays, operational uncertainties, failures, and noncooperating agents. In this work, we present a novel UAV traffic management (UTM) architecture that enables the integration of such UAVs in NAS. A combined A*–mixed integer linear programming (MILP)-based solution is presented for initial path planning of multiple UAVs with individual mission requirements and dynamic constraints. We also present a distributed detect-and-avoid (DAA) algorithm based on the concept of resource allocation using a market-based approach. The results demonstrate the scalability, optimality, and ability of the proposed approach to provide feasible solutions that are versatile in dynamic environments.

Two methods are presented for investigating reachable sets for nonlinear control systems. One method, based on a reachability maximum principle, lacks appropriate boundary conditions if the reachable set is not closed. The main result of the paper is an approximate method employing a Lyapunov-type function and an associated optimization problem, both involving a parameter vector. For each value of the parameter vector the resulting estimate for the reachable set (and the intersection of all such estimates) is guaranteed to contain the actual reachable set. The method is applicable to systems of any dimension and does not require integration of the equations of motion.

Real-time estimation of battery internal states and physical parameters is of the utmost importance for intelligent battery management systems (BMS). Electrochemical models, derived from the principles of electrochemistry, are arguably more accurate in capturing the physical mechanism of the battery cells than their counterpart data-driven or equivalent circuit models (ECM). Moreover, the electrochemical phenomena inside the battery cells are coupled with the thermal dynamics of the cells. Therefore, consideration of the coupling between electrochemical and thermal dynamics inside the battery cell can be potentially advantageous for improving the accuracy of the estimation. In this paper, a nonlinear adaptive observer scheme is developed based on a coupled electrochemical–thermal model of a Li-ion battery cell. The proposed adaptive observer scheme estimates the distributed Li-ion concentration and temperature states inside the electrode, and some of the electrochemical model parameters, simultaneously. These states and parameters determine the state of charge (SOC) and state of health (SOH) of the battery cell. The adaptive scheme is split into two separate but coupled observers, which simplifies the design and gain tuning procedures. The design relies on a Lyapunov's stability analysis of the observers, which guarantees the convergence of the combined state-parameter estimates. To validate the effectiveness of the scheme, both simulation and experimental studies are performed. The results show that the adaptive scheme is able to estimate the desired variables with reasonable accuracy. Finally, some scenarios are described where the performance of the scheme degrades.

Trong bài báo này, chúng tôi nghiên cứu mô hình hóa và điều khiển các robot manipulators có khớp nún. Đầu tiên, chúng tôi suy diễn một mô hình đơn giản để mô tả động lực học của các manipulators có khớp nún. Mô hình được suy diễn dưới hai giả định về sự kết nối động lực giữa các bộ truyền động và các thanh nối, và mô hình này hữu ích trong các trường hợp mà độ đàn hồi trong các khớp quan trọng hơn so với sự tương tác quán tính giữa các động cơ và các thanh nối. Khi độ cứng của khớp tiến đến vô cùng, mô hình của chúng tôi sẽ giảm thành mô hình cứng thông thường được tìm thấy trong tài liệu, cho thấy tính hợp lý của các giả định mô hình của chúng tôi. Chúng tôi chỉ ra rằng mô hình của chúng tôi có tính khả thi cao hơn đáng kể trong việc thiết kế bộ điều khiển hơn so với các mô hình phi tuyến trước đó đã được sử dụng để mô hình hóa các robot manipulators có khớp nún. Cụ thể, các phương trình chuyển động phi tuyến mà chúng tôi suy diễn được chứng minh là có thể tuyến tính hóa toàn cầu thông qua biến đổi tọa độ khả vi và phản hồi tĩnh phi tuyến, một kết quả không áp dụng được cho các mô hình đã được suy diễn trước đó của các robot manipulators có khớp nún. Chúng tôi cũng chi tiết một phương pháp thay thế để điều khiển phi tuyến dựa trên một hình thức rối số của các phương trình chuyển động và khái niệm về đa tạp tích phân. Chúng tôi chỉ ra rằng bằng cách sử dụng phản hồi phi tuyến thích hợp, đa tạp trong không gian trạng thái mà mô tả động lực học của robot manipulators cứng, tức là robot không có độ đàn hồi của khớp, có thể được làm bất biến dưới các nghiệm của hệ thống khớp nún. Các hệ quả của kết quả này đối với việc điều khiển các robot có khớp nún được thảo luận.

Improvements have been made to the nonlinear wheel / rail force prediction method of Elkins and Gostling. These improvements are described, along with the experimental equipment used in order to provide input data for the predictions, and to validate them. A further series of curving tests, using a Laboratory Coach equipped with bogies having variable suspension parameters, has been carried out, and shown to give excellent agreement with the improved theory. The prediction method is now used on a regular basis within British Rail, and its use for vehicle design is considered, together with planned extensions to cover calculation of wheel and rail wear and dynamic behavior of railway vehicles on curve and switch entry.

Sloshing of liquid in a tank is critical in several areas, including launch vehicles carrying liquid fuel, satellites, industrial packaging of liquids, systems handling molten metal, and so on. Hence modeling, characterization, and control of nonlinear slosh phenomena are important in these applications. To study slosh dynamics, develop useful identification schemes, and design and verify slosh control algorithms, a new 2DOF actuation slosh rig is reported in this paper considering the fact that most of the times these tanks are subjected to linear as well as pitching excitation/control inputs. The paper discusses mechatronic design and several advantages that the new design offers. A slosh phenomenon of beating observed when both lateral and pitching excitations are provided is simulated using a model based on pendulum approximation to slosh and is further verified in experiments. The results confirm that the effects of both excitations together can be detrimental against separate excitations of the same amplitude. Moreover, slosh compensation in open loop is demonstrated by giving excitation in pitching and developing a compensatory input in the lateral direction. Furthermore, active slosh control strategy is developed and its effectiveness is demonstrated with control in translation and disturbance in pitching. Thus the proposed rig is an ideal tool for the study, identification, and control development of slosh in the presence of two excitations/inputs.

In this paper, we discuss the problem of how a free-floating space manipulator can be mapped to a conventional, fixed-base manipulator which preserves both its dynamic and kinematic properties. This manipulator is called Dynamically Equivalent Manipulator (DEM). The DEM concept not only allows us to model a free-floating space manipulator system with simple, well-understood methods, but also to build a conventional manipulator system to experimentally study the dynamic performance and task execution of a space manipulator system, without having to resort to complicated experimental set-ups to simulate the space environment. This paper presents the theoretical development of the DEM concept, demonstrates the dynamic and kinematic equivalence, and presents simulation results to illustrate the equivalence under open-loop and closed-loop control strategies.

The problem of robust Kalman filter synthesis is considered in this present study for discrete multiple time-delay stochastic systems with parametric and noise uncertainties. A discrete multiple time-delay uncertain stochastic system can be transformed into another uncertain stochastic system with no delay by properly defining state variables. Minimax theory and Bellman-Gronwall lemma are employed on the basis of the upper norm-bounds of parametric uncertainties and noise uncertainties. A robust criterion can consequently be derived which guarantees the asymptotic stability of the uncertain stochastic system. Designed procedures are finally elaborated upon with an illustrative example.

This paper introduces a navigation system based on combined global positioning system (GPS) and laser-scanner measurements for outdoor ground vehicles. Using carrier-phase differential GPS, centimeter-level positioning is achievable when cycle ambiguities are resolved. However, GPS signals are easily attenuated or blocked, so their use is generally restricted to open-sky areas. In response, in this work we augment GPS with two-dimensional laser-scanner measurements. The latter is available when GPS is not and further enables obstacle detection. The two sensors are integrated in the range domain for optimal navigation performance. Nonlinear laser observations and time-correlated code and carrier-phase GPS signals are processed in a unified and compact measurement-differencing extended Kalman filter. The resulting algorithm performs real-time carrier-phase cycle ambiguity estimation and provides absolute vehicle positioning throughout GPS outages, without a priori knowledge of the surrounding landmark locations. Covariance analysis, Monte Carlo simulations, and experimental testing in the streets of Chicago demonstrate that the performance of the range-domain integrated system far exceeds that of a simpler position-domain implementation, in that it not only achieves meter-level precision over extended GPS-obstructed areas, but also improves the robustness of laser-based simultaneous localization and mapping.

A fundamental time-scaling property of manipulator dynamics has been identified that allows modification of movement speed without complete dynamics recalculation. By exploiting this property, it can be determined whether a planned trajectory is dynamically realizable given actuator torque limits, and if not, how to modify the trajectory to bring it within dynamic and actuating constraints.