These four movies represent the movements of the Northeastern Ambulatory Actuator during walking in the four directions. The ambulatory actuator segments move around three joints which are organized from the base of the leg out as:

During forward and backward walking translational propulsive forces are generated by the thoraco-coxal joint while during lateral walking they are generated by the mero-carpopodite joint. The four walking directions illustrated in the figure are:

0. Forward Walking (upper left)
1. Backward Walking (upper right)
2. Lateral Walking on the Leading (Pulling) Side (lower left) and
3. Lateral Walking on the Trailing (Pushing) Side (lower right)

All that differs between these behavioral acts is the coordination pattern of current signals applied to the shape memory alloy (Nitinol) acturators which control the three different joints of the leg. The current is regulated by the INM (Integrated Nick Machine) which is in the upper left corner of the rear view of each frame.. The INM receives control signals from the ambulation controller through a serial line interface and generates current pulses to activate the SMA actuators which control the different limb joints. If you look closely, you will notice that the LEDS on the INM are active in three different patterns:

0. Elevator of the Coxo-basal joint
1. small Depressor of the Coxo-basal joint
2. medium Depressor of the Coxo-basal joint
3. large Depressor of the Coxo-basal joint
4. small Protractor of the Thoraco-coxal joint
5. medium Protractor of the Thoraco-coxal joint
6. large Protractor of the Thoraco-coxal joint
7. small Retractor of the Thoraco-coxal joint
8. medium Retractor of the Thoraco-coxal joint
9. large Retractor of the Thoraco-coxal joint
10. small Extensor of the Mero-carpopodite joint
11. medium Extensor of the Mero-carpopodite joint
12. large Extensor of the Mero-carpopodite joint
13. small Flexor of the Mero-carpopodite joint
14. medium Flexor of the Mero-carpopodite joint
15. large Flexor of the Mero-carpopodite joint