Catastrophe Models for Cognitive Workload and Fatigue

We reconceptualised several problems concerning the measurement of cognitive workload – fixed versus variable limits on channel capacity, work volume versus time pressure, adaptive strategies, resources demanded by tasks when performed simultaneously, and unclear distinctions between workload and fatigue effects – as two cusp catastrophe models: buckling stress resulting from acute workload, and fatigue resulting from extended engagement. Experimental participants completed a task that was intensive on non-verbal episodic memory and had an automatically speeded component. For buckling stress, the epoch of maximum (speeded) performance was the asymmetry parameter; however, anxiety did not contribute to bifurcation as expected. For fatigue, the bifurcation factor was the total work accomplished, and arithmetic, a compensatory ability, was the asymmetry parameter; R2 for the cusp models outperformed the linear comparison models in both cases. A research programme is outlined that revolves around the two models with different types of task and resource configurations

Cusp Catastrophe Models for Cognitive Workload and Fatigue in a Verbally Cued Pictorial Memory Task

Objective: The aim of this study was to evaluate two cusp catastrophe models for cognitive workload and fatigue. They share similar cubic polynomial structures but derive from different underlying processes and contain variables that contribute to flexibility with respect to load and the ability to compensate for fatigue. Background: Cognitive workload and fatigue both have a negative impact on performance and have been difficult to separate. Extended time on task can produce fatigue, but it can also produce a positive effect from learning or automaticity. Method: In this two-part experiment, 129 undergraduates performed tasks involving spelling, arithmetic, memory, and visual search. Results: The fatigue cusp for the central memory task was supported with the quantity of work performed and performance on an episodic memory task acting as the control parameters. There was a strong linear effect, however. The load manipulations for the central task were competition with another participant for rewards, incentive conditions, and time pressure. Results supported the workload cusp in which trait anxiety and the incentive manipulation acted as the control parameters. Conclusion: The cusps are generally better than linear models for analyzing workload and fatigue phenomena; practice effects can override fatigue. Future research should investigate multitasking and task sequencing issues, physical-cognitive task combinations, and a broader range of variables that contribute to flexibility with respect to load or compensate for fatigue. Applications: The new experimental medium and analytic strategy can be generalized to virtually any realworld cognitively demanding tasks. The particular results are generalizable to tasks involving visual search

Solar Sail Spaceflight Simulation

The Solar Sail Spaceflight Simulation Software (S5) toolkit provides solar-sail designers with an integrated environment for designing optimal solar-sail trajectories, and then studying the attitude dynamics/control, navigation, and trajectory control/correction of sails during realistic mission simulations. Unique features include a high-fidelity solar radiation pressure model suitable for arbitrarily-shaped solar sails, a solar-sail trajectory optimizer, capability to develop solar-sail navigation filter simulations, solar-sail attitude control models, and solar-sail high-fidelity force models

Force-Assemblability: Insertion of a Workpiece into a Fixture Guided by Contact Forces Alone

The authors describe the concept of force-assemblability, which may be applied to fixture insertion as well as other assembly tasks. They define a linear force assemblable fixture to be one for which there exists a linear motion control law (examples of which include compliance and accommodation) which necessarily results in workpiece contact with all fixture elements (fixels) despite initial positional error. For reliable insertion, the fixture should have the property that contact with all fixels insures a unique workpiece position (i.e. the fixture should be deterministic) and the property that, after the inserting motion terminates, contact with all fixels is insured. It is shown that all deterministic fixtures are force-assemblable when friction is less than some value dictated by the workpiece/fixture geometry. It is also shown how to generate a motion control law that satisfies force-assemblability at this value of friction

Force-assembly with friction

If an admittance control law is properly designed, a workpiece can be guided into a fixture using only the contact forces for guidance (force-assembly). Previously, we have shown that: 1) a space of accommodation control laws that will ensure force-assembly without friction always exists, and 2) as friction is increased, a control law that allows force-assembly can be obtained as long as the forces associated with positional misalignment are characteristic. A single accommodation control law that allows force-assembly at the maximum value of friction can be obtained by an optimization procedure. The single accommodation control law obtained by the optimization procedure, however, is not unique. There exists a space of accommodation control laws that will allow force-assembly at, or below, the value of friction that marginally violates the characteristic forces condition. Here, for the purpose of the accommodation control law design, a set of linear sufficient conditions is used to generate accommodation basis matrices. Any nonnegative linear combination of the accommodation basis matrices that, when combined, yields a positive definite accommodation matrix is guaranteed to provide force-assembly at or below a specified value of friction. (Basi

Admittance Matrix Design for Force-guided Assembly

The authors address the design of manipulator admittance for reliable force-guided assembly. Their goal is to design the admittance of the manipulator so that, at all possible bounded part misalignments, the contact forces always lead to error-reducing motions. If this objective can be accomplished for a given pair of mating parts, the parts are called force-assemblable. As a testbed application of manipulator admittance design for force-guided assembly, the authors investigate the insertion of a workpiece into a fixture consisting of multiple rigid fixture to be one for which there exists an admittance matrix that ensures the unique positioning of a workpiece despite initial positional error. It is shown that, in the absence of friction, all deterministic fixtures are linearly force-assemblable. How to design an admittance matrix that guarantees that the workpiece will be guided into the deterministic fixture by the fixel contact forces alone is shown

The Space of Admittance Control Laws that Guarantees Force-Assembly with Friction

If an admittance control law is properly designed, a workpiece can be guided into a fixture using only the contact forces for guidance (force-assembly). Using an optimization procedure, a single accommodation control law that allows force-assembly at the maximum value of friction is obtained. For the purpose of the accommodation control law design, a set of linear sufficient conditions is used to generate accommodation basis matrices. Any nonnegative linear combination of the accommodation basis matrices that, when combined, yields a positive definite accommodation matrix, is guaranteed to provide force-assembly at (or below) the value of friction specified

Synthesis and Validation of Nondiagonal Accommodation Matrices for Error-Corrective Assembly

A methodology is described by which erroneous contact configurations for a given task are used to synthesize an appropriate accommodation matrix (either diagonal or nondiagonal) such that the motions which result from contact with the environment are error corrective. The methodology is verified by the synthesis and experimental validation of a nondiagonal accommodation matrix sufficient for an error-corrective place-in-detent robotic assembly operation, an operation that fails if a diagonal accommodation matrix is used

The Robustness of an Admittance Control Law Designed for Force Guided Assembly to the Disturbance of Contact Friction

The design of an admittance control law for reliable force-guided assembly is addressed. The overall objective is to design the manipulator\u27s mechanical performance so that, at each possible bounded part misalignment, the contact force always leads to a motion that alleviates the misalignment. The implementation of such an approach using a single nominal velocity and a single admittance function is referred to as force-assembly. Previous work addressing force-assembly of a workpiece into a fixture has shown that when workpiece/fixture contact is frictionless there always exists an admittance control law that ensures the proper insertion of a workpiece into a deterministic future. The authors discuss the identification of the condition that must be satisfied for force-assembly with friction and the optimization of the admittance control law to obtain the maximum value of friction that satisfies the force-assembly conditions for a given workpiece-fixture combination

American Academy of Nursing Expert Panel Consensus Statement on leveraging equity in policy to improve recognition and treatment of mental health, substance use disorders, and nurse suicide.

Rates of nurse mental health and substance use disorders are high. Heightened by the COVID-19 pandemic, nurses are challenged to care for patients in ways that often jeopardize their own health and increase risks for their families. These trends exacerbate the epidemic of suicide in nursing underscored by several professional organization clarion calls to nurses' risk. Principles of health equity and trauma-informed care dictate urgent action. The purpose of this paper is to establish consensus among clinical and policy leaders from Expert Panels of the American Academy of Nursing about actions to address risks to mental health and factors contributing to nurse suicide. Recommendations for mitigating barriers drew from the CDC's 2022 Suicide Prevention Resource for Action strategies to guide the nursing community to inform policy, education, research, and clinical practice with the goals of greater health promotion, risk reduction, and sustainment of nurses' health and well-being are provided