Motion Hacking

―Understanding by Controlling Animals―

抄録

Insects adapt their locomotor behavior in response to changes in environment and context by altering both inter- and intra-leg coordination. To elucidate underlying mechanisms in the leg coordination, we apply an external and precise method of interference with neural motion control, based on the electrostimulation of leg muscles. Here, we propose the method, called “Motion Hacking”, based on engineering techniques. First, we investigated externally controlled joint torques induced by stimulating one out of three leg muscles (protractor, retractor, and levator) in the stick insect Carausius morosus. For a given parameter set of a burst of pulse-width modulated electrostimulation, we found a piecewise linear relationship between the burst duration and the generated joint torque. Linearity holds for a burst duration range between 100 and 500 ms, corresponding to the typical values of swing and stance durations of walking in stick insects. The result suggests that the extent and timing of movement generated by joint torques of a single leg can be controlled. This is a necessary prerequisite for hacking the motion of a leg via external muscle stimulation in free walking insects.