On the automatic extraction of biomechanical information from handwriting signals

The analysis and synthesis of handwriting are discussed. In the context of a new generation model, a transfer function is proposed to describe the biomechanics of the system involved. This approach allows the extraction of specific movement parameters that reflect the active and passive states of the muscle network (generalized time constant, global gain factor) and the schematic description of the actualized motor program used to generate specific lines (timing and amplitude of the input stimuli). The model is validated with the automatic analysis and synthesis of more than 1500 straight lines written in eight directions by 11 subjects. The parameters extracted during this experiment are analyzed statistically as a function of the direction of movement and of the presence or absence of precue information about these directions. It is shown that asymmetries do exist at different levels in the system. A few directions can be distinguished from the others, but no independent and specific classes of principal directions clearly appear. The most efficient ones correspond to the range of directions of up and down strokes in normal cursive script