In the differential gear train of the hybrid mechanism, the adjustable-speed amplitude is the most basic and the most important technology parameter. It not only determines the matching relationship of the speed of the two input axes, but also decides the matching relationship of the installed capacity of the servomotor and the conventional motor. 4.2.2 Differential-speed ratio. The differential-speed ratio is usually used to express adjustable speed technology performance in the differential gear train. It is an important technology parameter of the differential effect in the differential system. The differential-speed ratio equals the reciprocal value of the adjustable-speed amplitude. It can be expressed as