Specification:
This mechanism is a differential gear train whose gears are all spur gears.
It is basically a combination of two planetary gear trains on which the two sun gears are coaxial.
The function of this mechanism is similar to the previous differential gear train.
This mechanism is applicable for the situation that requires two controllable inputs.
When the mechanism is driven and both wheels are releasing free, all
spur gears are running; when the right wheel is held, the right sun gear
will become fixed but the other gears are still rotatable; when the
left wheel is held, the left sun gear will become fixed but the other
gears are still rotatable.
