We propose a high-gain disturbance observer (HGDOB)-based backstepping control with position tracking error constraint for electro-hydraulic systems to improve the position tracking performance in ...the presence of disturbances. The HGDOB is designed to estimate the disturbances that include the friction, the load force, and the parameter uncertainties. Auxiliary state variables are proposed to avoid amplification of the measurement noise in the HGDOB. To compensate for the disturbances while guaranteeing tolerance of the position tracking error, the backstepping controller is proposed by using the barrier Lyapunov function. As a result, the proposed method satisfies the output constraint and improves the position tracking performance in the presence of disturbances. Its performance is validated via simulations and experiments.
The driving motor of the electric vehicle (EV) can recover the kinetic energy during normal braking maneuvers by a regenerative function. At the same time, its dynamic torque response proves to be ...accurate and fast for an emergency braking, namely an anti-lock braking, with the coordinated control of the frictional braking system. However, vehicle transmission properties will deteriorate the control performance of the motor, especially in the anti-lock braking process. A novel permanent magnet synchronous motor (PMSM) control method is proposed considering the transmission influence on this high-dynamic braking process of the pure EV. First, the EV's dynamic model, which includes the PMSM field-oriented control model, the transmission dynamic model, and the hydraulic braking system, is built, and the influences of transmission elasticity and backlash non-linearity on the motor-braking torque are analyzed. Then, based on the wheel slip ratio target of the anti-lock braking, the novel mode-switching method for the motor-torque control between the backlash sliding-mode compensation and the elasticity double-closed-loop PID compensation is put forward. Two state-of-the-art anti-lock braking algorithms, which simplify the transmission properties, the slip ratio phase-plane theory, and the sliding-mode control, are compared with the proposed method. Simulation and test-bench experiment results show that, on different test-road surfaces, the mode-switching PMSM control can effectively compensate for transmission effects and significantly improve the EV's anti-lock braking comfort, stability, and maneuverability with fast and accurate motor-torque regulating.
This paper focuses on the high accuracy synchronous control issue of multiple electro‐hydraulic systems (MEHS). For the parametric uncertainty and external load disturbance of electro‐hydraulic ...systems (EHS), a type of terminal sliding mode observer (TSMO) is introduced for MEHS in this paper, which able to estimate the parametric uncertainty and external load disturbance in finite time. Then, based on the proposed fast uncertainty estimation strategy, a synchronous controller is designed for MEHS, in which both dynamic surface design and barrier Lyapunov function (BLF) method has been adopted to realize a better tracking performance of MEHS. The feasibility and effectiveness of proposed algorithms in this paper are verified by simulation. Then, a series of comparative experimental results are provided to illustrate the advantages of both disturbance estimation capacity of TSMO and synchronous tracking control performance of proposed control strategy for MEHS.
This paper concerns high-accuracy tracking control for hydraulic actuators with nonlinear friction compensation. Typically, LuGre model-based friction compensation has been widely employed in sundry ...industrial servomechanisms. However, due to the piecewise continuous property, it is difficult to be integrated with backstepping design, which needs the time derivation of the employed friction model. Hence, nonlinear model-based hydraulic control rarely sets foot in friction compensation with nondifferentiable friction models, such as LuGre model, Stribeck effects, although they can give excellent friction description and prediction. In this paper, a novel continuously differentiable nonlinear friction model is first derived by modifying the traditional piecewise continuous LuGre model, then an adaptive backstepping controller is proposed for precise tracking control of hydraulic systems to handle parametric uncertainties along with nonlinear friction compensation. In the formulated nonlinear hydraulic system model, friction parameters, servovalve null shift, and orifice-type internal leakage are all uniformly considered in the proposed controller. The controller theoretically guarantees asymptotic tracking performance in the presence of parametric uncertainties, and the robustness against unconsidered dynamics, as well as external disturbances, is also ensured via Lyapunov analysis. The effectiveness of the proposed controller is demonstrated via comparative experimental results.
Summary
In the stems of terrestrial vascular plants studied to date, the diameter of xylem water‐conducting conduits D widens predictably with distance from the stem tip L approximating D ∝ Lb, with ...b ≈ 0.2. Because conduit diameter is central for conductance, it is essential to understand the cause of this remarkably pervasive pattern. We give reason to suspect that tip‐to‐base conduit widening is an adaptation, favored by natural selection because widening helps minimize the increase in hydraulic resistance that would otherwise occur as an individual stem grows longer and conductive path length increases. Evidence consistent with adaptation includes optimality models that predict the 0.2 exponent. The fact that this prediction can be made with a simple model of a single capillary, omitting much biological detail, itself makes numerous important predictions, e.g. that pit resistance must scale isometrically with conduit resistance. The idea that tip‐to‐base conduit widening has a nonadaptive cause, with temperature, drought, or turgor limiting the conduit diameters that plants are able to produce, is less consistent with the data than an adaptive explanation. We identify empirical priorities for testing the cause of tip‐to‐base conduit widening and underscore the need to study plant hydraulic systems leaf to root as integrated wholes.
In this article, a novel neural network (NN)-based adaptive dynamic surface asymptotic tracking controller with guaranteed transient performance is proposed for <inline-formula> <tex-math ...notation="LaTeX">n </tex-math></inline-formula>-degrees of freedom (DOF) hydraulic manipulators. To fulfill the work, the entire manipulator system model, including hydraulic actuator dynamics, is first established. Then, the neural adaptive dynamic surface controller is designed, in which the NN is utilized to approximate the unknown joint coupling dynamics, while the approximation error and uncertainties of the actuator dynamics are addressed by the nonlinear robust control law with adaptive gains. In addition, a modified funnel function that ensures the joint tracking errors remains within a predefined funnel boundary and is skillfully incorporated into the adaptive dynamic surface control (ADSC) design to achieve a guaranteed transient tracking performance. The theoretical analysis reveals that both the guaranteed transient tracking performance and asymptotic stability can be achieved with the proposed controller. Contrastive simulations are performed on a 2-DOF hydraulic manipulator to demonstrate the superiority of the proposed controller.
In this paper, an adaptive output feedback prescribed performance controller is proposed for a hydraulic system with matched and mismatched uncertainties (including parametric uncertainties and ...uncertain nonlinearities), which always exist in physical hydraulic systems, and degrade the internal state stability and tracking response performance. By integrating the adaptive control and disturbance observer into the extended state observer, the matched and mismatched uncertainties can be feedforward compensated in the output feedback control. Then, based on the fusion of prescribed performance function and barrier Lyapunov function, the proposed practical method is designed via backstepping method for hydraulic systems, all states are maintained within a preset range by constraining the upper bound of the control errors and the output tracking error is kept within a predetermined boundary that decreases with time. Moreover, the stability of closed-loop system is analyzed by Lyapunov theory. Finally, comparative experimental results are obtained to verify the control performance of the proposed control strategy.
Aiming at the tough requirements for safety and maintainability in mobile hydraulic systems, in this article, an active fault-tolerant control (FTC) system is proposed against the valve faults of an ...independent metering valve. Not only moderate faults of activated valves, but also significant faults and unactivated valve faults are considered. Without additional hardware redundancy, analytical redundancy is derived by the coordinate control of other fault-free valves. Accordingly, an FTC system in parallel with a normal controller is designed based on the pressure feedback. It consists of a set of reconfigurable controllers and a decision mechanism. The control signals, control loops, and operating modes can all be precisely reconfigured to adaptively match unmodeled fault dynamics. A bumpless transfer controller based on a latent tracking loop is designed to smooth the switching between the normal controller and FTC. Consequently, random valve faults can be tolerated with minor degradations in motion tracking and energy-saving performance. The feasibility of the FTC system is evaluated by a 2-ton excavator.
The More-Electric Aircraft and Beyond Buticchi, Giampaolo; Wheeler, Pat; Boroyevich, Dushan
Proceedings of the IEEE,
04/2023, Letnik:
111, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Aviation is a significant contributor to greenhouse gas (GHG) emissions in the transportation sector. As the adoption of electric cars increases and GHG emissions due to other modes of transport ...decrease, the impact of air travel on environmental pollution has become even more significant. To reduce pollution and maintenance, and ensure cheaper and more convenient flights, industry and academia have directed their efforts toward aircraft electrification. Considering various types of aircraft, several frameworks have been proposed: more-electric aircraft (MEA), hybrid electric aircraft (HEA), and all-electric aircraft (AEA). In the MEA framework, propulsion is generated by a conventional jet engine; however, all secondary systems (hydraulic, pneumatic, and actuation) are electrified. By further increasing electrification, electric motors can provide propulsion with the electric power supplied by the conventional engine (i.e., HEA) or from electrical energy storage (i.e., AEA). Power electronics and electrical machines play a key role in this scenario in which electric power must be efficiently generated, distributed, and consumed to satisfy extremely high requirements of aviation safety. This article provides an overview of recent advancements in aircraft electrification, and trends and future developments referenced to the global aviation roadmap.
Given increasing water deficits across numerous ecosystems world-wide, it is urgent to understand the sequence of failure of leaf function during dehydration.
We assessed dehydration-induced losses ...of rehydration capacity and maximum quantum yield of the photosystem II (F
v/F
m) in the leaves of 10 diverse angiosperm species, and tested when these occurred relative to turgor loss, declines of stomatal conductance g
s, and hydraulic conductance K
leaf, including xylem and outside xylem pathways for the same study plants. We resolved the sequences of relative water content and leaf water potential Ψleaf thresholds of functional impairment.
On average, losses of leaf rehydration capacity occurred at dehydration beyond 50% declines of g
s, K
leaf and turgor loss point. Losses of F
v/F
m occurred after much stronger dehydration and were not recovered with leaf rehydration. Across species, tissue dehydration thresholds were intercorrelated, suggesting trait co-selection. Thresholds for each type of functional decline were much less variable across species in terms of relative water content than Ψleaf.
The stomatal and leaf hydraulic systems show early functional declines before cell integrity is lost. Substantial damage to the photochemical apparatus occurs at extreme dehydration, after complete stomatal closure, and seems to be irreversible.
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