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

This paper proposes a robust control strategy for uncertain LTI systems. The strategy is based on an uncertainty and disturbance estimator (UDE). It brings similar performance as the time-delay control (TDC). The advantages over TDC are: (i) no delay is introduced into the system; (ii) there are no oscillations in the control signal; and (iii) there is no need of measuring the derivatives of the state vector. The robust stability of LTI-SISO systems is analyzed, and simulations are given to show the effectiveness of the UDE-based control with a comparison made with TDC.

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 paper presents the results of an ongoing research project where the objectives are to evaluate medium access control (MAC) protocols in view of the requirements for distributed digital flight control systems (DDFCS) of advanced aircraft and to recommend a specific protocol for their prototype development. The selection of an appropriate MAC protocol is critical for the dynamic performance of an aircraft because the DDFCS, in addition to the sampling time delay, is subject to time-varying transport delays due to data latency of messages at different terminals of the control loop. The SAE linear token bus, SAE token ring and the conventional MIL-STD-1553B protocols have been analyzed using combined discrete-event and continuous-time simulation techniques. The impact of data latency on the dynamic performance of an advanced aircraft is illustrated by simulation of the closed loop DDFCS.

Design of a stable adaptive controller and observer for a class of nonlinear systems that contain product of unmeasurable states and unknown parameters is considered. The nonlinear system is cast into a suitable form based on which a stable adaptive controller and observer are designed using a parameter dependent Lyapunov function. The class of nonlinear systems considered is practically relevant; mechanical systems with dynamic friction fall into this category. Experimental results on a single-link mechanical system with dynamic friction are shown for the proposed design.

A method is presented for generating shaped command inputs which significantly reduce or eliminate endpoint vibration. Desired system inputs are altered so that the system completes the requested move without residual vibration. A short move time penalty is incurred (on the order of one period of the first mode of vibration). The preshaping technique is robust under system parameter uncertainty and may be applied to both open and closed loop systems. The Draper Laboratory’s Space Shuttle Remote Manipulator System simulator (DRS) is used to evaluate the method. Results show a factor of 25 reduction in endpoint residual vibration for typical moves of the DRS.

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.