A probabilistic approach to the degrees of freedom problem in human movements

Date

2024-4

Author

İmir, Mehmet

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Humans possess a wide range of solutions in terms of musculoskeletal actions they can perform and diverse task-space approaches they can employ to accomplish the same objective. The excessive number of degrees of freedom inherent in the multi-joint human movement is mathematically expressed by modeling the human body as a kinematic chain. Joint angles are treated as random variables rather than deterministically as traditionally done. In the study, we propose a probabilistic forward kinematic model based on the convolution of the random joint angles to analyze the degrees of freedom problem in multi-joint human movements. A series of experiments was conducted to test the validity of the model, with multiple trials involving reaching movements while standing. The joint angles data obtained from experiments were used to determine the empirical distributions of joint angles. The probabilistic forward kinematic model is employed to calculate all possible joint configurations that maintain the endpoint of the hand within a task-specific region. These joint configurations are then used to estimate an expected joint configuration, which should match the mean joint configuration used by the person during the movement. The difference between the expected joint configuration and the mean joint configuration was deemed to be within an acceptable range. Furthermore, the proposed probabilistic framework accounts for the variability in joint configurations and task-space movements that are observed during the repetition of multi-joint movements.

Subject Keywords

Degrees of freedom problem in movements, Redundancy in movements, Multi-joint movements, Movement variability, Probabilistic forward kinematic

URI

https://hdl.handle.net/11511/109734

Collections

Graduate School of Natural and Applied Sciences, Thesis