  In hybrid industrial environments, workers' comfort and positive perception
of safety are essential requirements for successful acceptance and usage of
collaborative robots. This paper proposes a novel human-robot interaction
framework in which the robot behaviour is adapted online according to the
operator's cognitive workload and stress. The method exploits the generation of
B-spline trajectories in the joint space and formulation of a multi-objective
optimisation problem to online adjust the total execution time and smoothness
of the robot trajectories. The former ensures human efficiency and productivity
of the workplace, while the latter contributes to safeguarding the user's
comfort and cognitive ergonomics. The performance of the proposed framework was
evaluated in a typical industrial task. Results demonstrated its capability to
enhance the productivity of the human-robot dyad while mitigating the cognitive
workload induced in the worker.
