Exhausted and strange behavior

ALLBOT ALLBOT - Four legs (VR408)
1

if i connect the robot to 4 batteries, there is no problem until the batteries get not enough power which i understand.
if i remove the batteries and directly connect the VRBS1 shield over the SK1 to a lab power supply :

  • set on 4.5V = the robot can move but it can"t stand on his legs nor stay on them. it seems exhausted.
  • set on 6V = the robot doesn’t respect the sketch (the velleman exemple). His legs are stuck in strange position or try to force to move.

Should i use batteries on the VRBS1 shield and connect the VRSSM shield to the power supply ?

2

Try attaching power to the VRSSM SHIELD

3

not better.
If i plug the power supply (4.5V) on the VRSSM shield and i unplug the VRBS1, the legs move for 1s and stop. The sketch is not play (no beep).
On 6V, nothing move, the 4 blue lights switch on for 1s.

If i also plug the VRBS1 shield, all legs try to move to impossible positions (the strange behavior).