Leg Trajectory Research Articles

The stick insect, Obrimus asperrimus (Phasmida, Bacillidae) walking on different surfaces

Unrestrained adult stick insects ( Obrimus asperrimus) walked below a tread wheel 4 or 30 mm wide in the upside-down position or above a ‘bridge’ 30 or 60 cm wide in the upright position. They were recorded on video and the positions of reference points on the legs and on the body were measured on still frames. Step parameters such as step amplitude, step duration, swing duration, body height and ground width are given for broad and narrow footing as well as for leg trajectories and the course of leg joint angles. Joint angles were calculated directly between the leg segment vectors. Walking with a narrow footing, the stick insect used the same slow metachronal gait as on a broad footing. Adjustment to the narrow footing was accomplished by narrowing the ground base, raising the body distance, depressing the femora (by 40–45 °) and flexing the tibiae (20–25 ° in the front and middle legs). The upper turningpoint of the swing movement seems to be determined by a constant amplitude of the vertical movement component rather than a given position in a body-fixed coordinate system. Walking on a horizontal rod of circular cross-section, the insects preferred to walk upside down below the rod for small diameters, but preferred to walk upright above the rod if its diameter was great enough.

Walking cycle recording and analysis for FNS-assisted paraplegic walking

In closed-loop functional neuromuscular stimulation (FNS)-assisted paraplegic walking, there is a need for reference leg motion trajectories that describe the desired walking cycle. These reference trajectories were defined as the angular changes between the leg segments, as measured by an electrogoniometer system. For each leg, the hip, knee and ankle trajectories of normal individuals during slow walking were measured and sampled over a number of cycles. Additionally, foot contact with the ground was measured to synchronise the various walking trajectories. Each joint's angular trajectory was averaged over a number of walking cycles, using an interpolation method based on a discrete Fourier transform (DFT) and inverse DFT technique, to expand all the signals to the same length. In this way an average walking cycle was obtained for each trial, representing the six averaged leg motion trajectories for one walking cycle. Angular trajectories and walking parameters for slow and normal walking were compared so as to investigate principles of walking cycle adaptation necessary to stabilise the body during slow walking. In general, angular trajectories were similar for different subjects, but different for different walking speeds, due to the greater demands on maintaining stability during slow walking. It can be concluded that normal speed walking consists of separate, unstable phases, whereas slow speed walking, relevant for paraplegic walking, requires stabilising each separate phase of the walking cycle.

4足歩行機械の一般化基準脚軌道

4足歩行機械の一般化基準脚軌道