Understanding and Modeling Perceived Cognitive and Physical Strain Dynamics for Planning-Oriented Human-Robot Collaboration in Prefabricated Construction
Authors: Yifan Wang, Bo Xiao, Shane T. Mueller
Organizations: Ph.D. Candidate, Department of Civil, Environmental, and Geospatial Engineering, Michigan Technological University, Houghton, 49931 MI, USA. · Assistant Professor, Department of Civil, Environmental, and Geospatial Engineering, Michigan Technological University, Houghton, 49931 MI, USA. · Professor, Department of Psychology and Human Factors, Michigan Technological University, Houghton, 49931 MI, USA.
Human-robot collaboration (HRC) in prefabricated construction requires planning approaches that consider not only productivity but also time-dependent worker states during repeated work and rest. Existing planning models often rely on simplified assumptions about fatigue, workload, or recovery, with limited domain-specific empirical evidence on how perceived strain evolves. This study develops an empirically grounded, planning-oriented approach to characterize perceived strain accumulation and recovery in prefabricated construction HRC. A controlled repeated work-rest experiment assessed perceived cognitive and physical strain using the Rating Scale for Mental Effort and Borg's Rating of Perceived Exertion. Linear and exponential functional forms were evaluated, followed by mixed-effects modeling to examine collaborative conditions, session effects, and inter-individual variability. Results indicate that cognitive strain accumulation is best represented by a linear mixed-effects model, whereas rest-phase recovery follows nonlinear decay. The resulting planning-oriented models may inform future human-state-aware task allocation and scheduling research.
The introduction of human-robot collaboration (HRC) in industrial assembly operations is revolutionizing the manufacturing landscape. In this evolving environment, operators are required to seamlessly coordinate their manual tasks with real-time task information and robotic behaviors. These demands fluctuate during operation, yet conventional workload assessments depend on body-worn physiological sensors that complicate practical deployment. Here, we present a vision-based attention--action framework for continuous and interpretable workload-related assessment in HRC assembly. The framework combines RGB-D observations with robot states and calibrated task-related areas to construct a temporally confirmed representation of operator behavior. This representation identifies where task demand is concentrated and explains how it develops when attention and action diverge, the task context changes, or the operator hesitates. We evaluated the framework in a three-level collaborative gearbox assembly experiment with ten participants, using subjective ratings and synchronized physiological signals as independent references. Raw NASA-TLX ratings confirmed increasing perceived workload across conditions, with significant effects on overall workload and its mental and temporal dimensions. The vision-derived HRC-CWL output was significantly associated with ECG-derived features in seven of nine participants with complete correlation data. Synchronized interaction episodes further showed temporal correspondence between detected hesitation and physiological activity. Real-time deployment demonstrated that the framework can operate without requiring operators to wear additional sensors. These findings support HRC-CWL as an interpretable behavioral proxy for cognitive ergonomics analysis and adaptive robot assistance, rather than a direct psychophysiological measure of workload.
Understanding why some sequential planning problems are harder than others requires models that go beyond average performance. They should capture the specific pattern of which problems are hard, and ideally fail in the same way people do when planning capacity is reduced. We apply AICON, a reactive gradient-descent framework developed for robotic manipulation, to the Tower of London test, a cognitive test used to assess planning in Parkinson's disease, mild cognitive impairment, and stroke. Without any lookahead planning or knowledge of human cognition, AICON reproduces the fine-grained human difficulty ordering across 24 problems better than structural task parameters and generalizes to held-out problems in a leave-two-out evaluation. Crucially, AICON outperforms a planning baseline for groups with reduced planning capacity while the planning baseline better captures healthy controls. This dissociation was predicted by the original AICON paper, which noted that the model's failure modes resemble those of Parkinson's patients who struggle with goal hierarchies but not move counts. This suggests that as planning capacity is reduced, human behavior shifts toward the reactive mode AICON models. The finding extends a broader pattern: AICON, originally built for robotics, now captures aspects of biological behavior across perception, eye movements, and sequential planning, suggesting its core abstraction reflects something real about how biological systems are organized.
Michael Migacev, Vito Mengers, Antonia Köngeter +1
Human-robot collaboration in construction is often challenged by limited robot-to-human communication and the need to adapt to tolerance accumulation arising from material and assembly uncertainties. We present an adaptive human-robot collaborative workflow for masonry construction that addresses communication limitations and tolerance accumulation, demonstrated through a brickwork case study in which a robot places bricks while a human applies adhesive. This workflow is enabled by two complementary mechanisms: 1) an end-effector-mounted projector that provides spatially registered, just-in-time projection guidance for manual adhesive application, and 2) laser scanning for feedback-driven grasping and placement pose correction. Together, these mechanisms enable adjustment of human and robotic actions in response to material variability and accumulated assembly tolerances. Full-scale experiments across conventional running-bond and nonstandard configurations demonstrate that projection guidance improves adhesive application consistency and reduces application time, while laser-based correction maintains level courses and avoids collision-prone failures associated with open-loop execution. These results indicate that integrating spatial projection with feedback-driven adaptation, enabled by material and as-built sensing, can mitigate tolerance accumulation and improve precision and robustness in human-robot collaborative construction.