This article proposes a new robust control design framework for uncertain mechanical systems, which may be fully actuated or underactuated. The uncertainty is (possibly fast) time varying, which lies ...in prescribed fuzzy sets (hence fuzzy mechanical systems) and may be unbounded. The control goal is formulated as servo constraints (hence constraint-following control), which may be holonomic or nonholonomic. We introduce the possibility theory into the Lyapunov stability analysis (LSA), proposing possibility-based LSA (PBLSA), which allows a maximum failure possibility (generally small) prescribed by designers. It can be viewed as a generalization of the conventional LSA, and the resultant performance is interpreted in the context of possibility. By the PBLSA, a class of robust constraint-following controls that is not IF-THEN heuristic rules based is proposed, which renders approximate constraint following for the system performance with a prescribed maximal failure possibility. Optimal design of a control parameter considering both system performance and control cost is investigated. The benefits of the proposed design framework are discussed and simulations on two applications are given for demonstrations.
•Mismatched uncertainty in underactuated systems is targeted by constraint-following.•A novel uncertainty decomposition method is proposed for robust control design.•Uniform boundedness and uniform ...ultimate boundedness are guaranteed by the control.•The robust constraint-following control can tolerate large mismatched uncertainty.•The control is successfully applied to an underactuated mobile robot by simulations.
The mismatched uncertainty makes the control for underactuated systems an intractable problem in the control field. This paper targets this problem based on constraint-following. The uncertainty is (possibly fast) time-varying and bounded. The control goal is to drive underactuated systems to follow prescribed constraints, which may be holonomic or nonholonomic, linear or nonlinear with respect to the velocity. The control is designed in two steps. First, the nominal control without addressing uncertainties and initial condition deviations is investigated. Second, we meticulously decompose uncertainty into matched and mismatched portions. This decomposition makes the mismatched uncertainty “disappear” in the stability analysis. Consequently, we are able to design a class of robust constraint-following controls free from mismatched uncertainty and only based on matched uncertainty. By the Lyapunov approach, we show that the proposed robust controls guarantee uniform boundedness and uniform ultimate boundedness for underactuated systems. Simulation results on a mobile robot are given for demonstrations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Aquaculture is the fastest-growing farmed food sector and will soon become the primary source of fish and shellfish for human diets. In contrast to crop and livestock production, aquaculture ...production is derived from numerous, exceptionally diverse species that are typically in the early stages of domestication. Genetic improvement of production traits via well-designed, managed breeding programmes has great potential to help meet the rising seafood demand driven by human population growth. Supported by continuous advances in sequencing and bioinformatics, genomics is increasingly being applied across the broad range of aquaculture species and at all stages of the domestication process to optimize selective breeding. In the future, combining genomic selection with biotechnological innovations, such as genome editing and surrogate broodstock technologies, may further expedite genetic improvement in aquaculture.
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A spatial-dependent robust control strategy is proposed for the on-ramp merging problem based on the coordination of the connected and automated vehicles. In the proposed strategy, the planning stage ...of the merging coordination is weakened while the control stage is strengthened. More specifically, the planning stage mainly forms a virtual platoon containing all vehicles inside the communication zone. In the control stage, the time-varying parameter uncertainties in the model are considered. A spatial-dependent controller with uniform boundedness, uniform ultimate boundedness and robustness is delicately designed for each vehicle in the virtual platoon to analytically calculate the control force in real time. The spatial-dependence means that the safety-related performances of the controller are directly and explicitly bonded with spatial locations such that the collision-avoidance safety is ensured at the most dangerous conflicting merging zone. Since spatial locations in the traffic environment are static, this spatial-dependence endows the proposed strategy more stability and reliability. The effectiveness of the proposed strategy is demonstrated through the verification, ablation and comparison simulation cases.
A novel analytical modeling and dynamic manipulation control method of the multi-fingered hand robot has been proposed in the paper. Based on the contact constraints, the explicit dynamics modeling ...of the hand robot manipulating an object is hierarchically established by Udwadia–Kalaba equation with no auxiliary variable (e.g., Lagrange multipliers or quasi-generalized variables). Through the second order of the contact constraints, the grasping forces of the hand robot in the manipulation work space are derived explicitly and decoupled with the control torques of the finger joints. Consider the hand robot and the object as an entire system in the control design. Motivated by Udwadia’s work, the manipulation task of the grasped object is novelly used to formulate a set of servo constraints. In virtue of following the servo constraints, the hand robot can manipulate the object to accomplish the desired task. With the formulated contact forces model, a model-based dynamic control method is proposed for the hand robot to handle the object, which does not depend on the force feedback from the fingertips sensors (force sensorless). The system performance under the proposed control can be guaranteed by the theoretical proofs and demonstrated by the simulation of a three-fingered hand robot in the three-dimensional work space.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, the dynamic modeling and collaborative control of a multi-vehicle cooperative transportation system for load carrying is explored. A hierarchical modeling and constraint-following ...control scheme is creatively proposed. In the dynamic modeling stage, the separate models of system components including the load and vehicle carriers are firstly established at the lower level. Then the internal and external constraints corresponding to the system topology and the transportation task are designed to integrate separate models at a higher level. In the system control stage, a distributed collaborative control law is proposed based on the closed-form constraint forces, with which the load can follow the external constraints actively and the carriers can maintain the internal constraints passively. In order to overcome the influence of time-varying multi-source uncertainties of the system on control effectiveness and stability, an adaptive robust control term is designed based on the Lyapunov min-max approach. Both uniform boundedness and uniform ultimate boundedness of the constraint-following error are guaranteed. Comprehensive validations show that our propose scheme can significantly reduce the modeling complexity despite the strongly coupled topology and nonlinearity of the system, as well as achieving more precise and robust trajectory following control compared with the baseline methods.
•Underactuated ASS control with equality and inequality constraints is considered.•Diffeomorphism is employed for the constraint-following control design.•The approach is validated by theoretical ...proof, experiments and simulations.
We formulate the control problem of active suspension systems (ASSs) that are underactuated as constraint-following. The objective is to drive the system to follow a series of servo constraints or control goals which include both equality constraint of the reference trajectory and inequality constraint of the boundary restriction on the sprung mass displacement. The equality constraints may be holonomic or nonholonomic. The control design is implemented in two steps. First, a constraint-following control (CFC) is applied to drive ASSs to follow equality constraints, under the premise of ignoring inequality constraints. No auxiliary variables or pseudo variables are required for the control design. Second, diffeomorphism is employed to integrate inequality constraints into equality constraints, by which a novel CFC is proposed to deal with both equality and inequality constraints. The effectiveness of the proposed approach is demonstrated by rigorous proof. Furthermore, we investigate an ASS control problem in which the equality constraint is determined by the skyhook model, and the inequality contraint of the sprung mass displacement is determined by the suspension deflection and the tire dynamic displacement. Experimental and numerical simulation results on this case are presented for demonstrations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Accurate tracking control of autonomous cooperative transportation systems (CTS) remains challenging owing to the complexity of the mechanisms and the high requirements of coordination between ...carriers. In this paper, the trajectory tracking control of a CTS with a pair of autonomous vehicles serving as carriers is investigated. A novel constraint-oriented hierarchical modeling method is proposed to describe the dynamics of the system. By dividing the system dynamics into two portions: the lower-level individual modeling and the upper-level constraints abstraction, the modeling process is significantly simplified. Then an innovative constraint-following control law is designed to address the tracking control problem under the special system topology, based on the internal and external constraints designed in the modeling process. The asymptotic convergence of the tracking error is theoretically guaranteed. To reduce potential damage of the payload during transportation, a payload force optimization method is creatively proposed. It relies on the closed-form relationship between the control input and payload forces established by the constraint-oriented modeling. The normal and shear stress on the payload is successfully limited, without affecting the trajectory tracking performance. Simulation results show that the proposed control method and the payload force optimization strategy can help achieve accurate and safe autonomous cooperative transportation simultaneously.
Path tracking for autonomous vehicles is one of the most critical tasks in intelligent transportation systems (ITS). The ITS performance, including efficiency, safety, flexibility, and resilience, ...are all based on it. The two central issues for a successful path tracking are resilience and smoothness. We endeavor to adopt a neural-activation based constraint-following approach to resolve these two issues concurrently. First, an adaptive robust constraint-following control scheme is proposed. The control tracks a desired trajectory with guaranteed performance even in the presence of uncertainty. Second, a neural-activation mechanism is proposed, which generates desired trajectory effectively based on traffic pattern with sufficiently smoothness. Third, the trajectory is embedded into the control scheme to ensure that the control conforms to any changing traffic pattern while in motion. As a result, the control can rapidly adapt to the changing traffic condition with smoothness and resilience.
The application of genome engineering techniques to understand the mechanisms that regulate germ cell development opens promising new avenues to develop methods to control sexual maturation and ...mitigate associated detrimental effects in fish. In this study, the functional role of piwil2 in primordial germ cells (PGCs) was investigated in Nile tilapia using CRISPR/Cas9 and the resultant genotypes were further explored. piwil2 is a gonad-specific and maternally deposited gene in Nile tilapia eggs which is known to play a role in repression of transposon elements and is therefore thought to be important for maintaining germline cell fate. A functional domain of piwil2, PIWI domain, was targeted by injecting Cas9 mRNA and sgRNAs into Nile tilapia embryos at 1 cell stage. Results showed 54% of injected mutant larvae had no or less putative PGCs compared to control fish, suggesting an essential role of piwil2 in survival of PGCs. The genotypic features of the different phenotypic groups were explored by next generation sequencing (NGS) and other mutant screening methods including T7 endonuclease 1 (T7E1), CRISPR/Cas-derived RNA-guided engineered nuclease (RGEN), high resolution melt curve analysis (HRMA) and fragment analysis. Linking phenotypes to genotypes in F0 was hindered by the complex mosacism and wide indel spectrum revealed by NGS and fragment analysis. This study strongly suggests the functional importance of piwil2 in PGCs survival. Further studies should focus on reducing mosaicism when using CRISPR/Cas9 system to facilitate direct functional analysis in F0.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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