Auto walking mode

To proof motor have ability to help human walking. We observe power, which obtain by product of driving current and driving voltage, within gait cycle as figure below. Here power is negative means current flow in different direction to let motor rotate different direction. We can discover that power would have two peaks, which happen on angle position change from upper limit to lower limit and vice versa. Peaks did not happen when angle position around limit so that we can make sure knee cylinder would not trig limit switch, which means overshoot problem would not happen during walking. In addition, motor supply enough power to support human rotate hip angle position from command max value to min value, vice versa.

Fig. 8-2 Power consumption within gait cycle.

We would show result for normal human wearing exoskeleton. We use camera to capture video for human walking with exoskeleton assisting. We put three times gait cycle results for image processing. Capturing data on angle and time relation as below figure. We can observe that normal human natural walking, which is solid line result, would have higher speed than assisting with exoskeleton. With exoskeleton assisting, frequency for human walk gait cycle is 0.37Hz, which is not high enough to catch normal human walking speed, but this frequency is high enough for supporting human, whose lower limb muscle has weak ability. We would illustrate this point more clearly latter.

Fig. 8-3 Normal human wearing result for angle time relation.

We pick up data with each gait cycle. Putting different gait cycle data together and calculate average for these three angle rotating position data. We can get average hip rotation data, which are on free walking and assisted walking for normal human respectively.

Fig. 8-4 Normal human free walking gait.

Fig. 8-5 Normal human gait assisted by exoskeleton.

After getting average rotating angle data on free and assisted walking, we sort them with command as below figure. We can observe that rotating angle range would not change after assisting. With exoskeleton assisting, position control is still accurate for tracking command gait cycle. However, assisted walking would have slower speed to reach upper rotation limit at end of gait cycle than free walking. This slower speed would let normal human speed decrease than free walking.

Fig. 8-6 Normal human wearing result for gait cycle representation.

We have already known that our exoskeleton have ability to assist human walk as command gait roughly. However, above testing we choose user, who has normal muscle ability. It is not enough to proof our exoskeleton has ability to assist old man or weak muscle ability human. In addition, normal human perform lower speed after assisting.

Therefore, we make a wood beam barrier fixing on user leg as below figure. We define user with below figure situation as physically challenged human. Then testing exoskeleton assist effect on physically challenged human.

Fig. 8-7 Normal human with barrier.

Same as above method, we use camera to capture video for physically challenged walking with exoskeleton assisting. We put three times gait cycle results for image processing. Capturing data on angle and time relation as below figure. We can observe that first free and assisted peak would happen at same time, but assisted would lead free on second peak and latter, which means our exoskeleton can speed up physical challenge human walking unless first gait cycle. With exoskeleton assisting, frequency for human walk gait cycle is 0.39Hz. This frequency is high enough to catch general physically challenged human walking speed.

Fig. 8-8 physically challenged human wearing for angle time relation.

Again, we pick up data with each gait cycle. Putting different gait cycle data together and calculate average for these three angle rotating position data. We can get average hip rotation data, which are on free walking and assisted walking for physically challenged human respectively.

Fig. 8-9 physically challenged human free walking gait.

Fig. 8-10 physically challenged human gait assisted by exoskeleton.

After getting average rotating angle data on free and assisted walking, we sort them with command as below figure. We can observe that assisted rotating range would bigger than free walking, which means our exoskeleton have ability to enlarge hip rotating range for physically challenged human. This enlarge rotating range can help physically challenged human modify their gait to normal gait. In addition, we can observe that assisted rotating angle can pursuit command gait roughly as above. With exoskeleton assisting, position control is still accurate for tracking command gait cycle.

Fig. 8-11 physically challenged human wearing for gait cycle representation.

We comparing normal human free walking and physically challenged human result as below figure. Here we use solid line show normal human free walking result. Dot line and dash line is free and assisted walking on physically challenged human respectively. We can discover that assisted gait would fit normal walking more than free gait at stance phase, which is first 60% gait cycle. At swing phase, which is post 40%

gait cycle, assisted gait would perform higher max value than free gait, which means rotating range enlarge would be explained again. This enlarge rotating range can help physically challenged human modify their gait to normal gait. Sum up, physically challenged human with our exoskeleton assisting can reach normal human free walking gait cycle.

Fig. 8-12 physically challenged human wearing for gait cycle comparison.