Both the steps and the handrail are driven by the motor and the transmission mechanism, and the installation positions of the driving wheels of the handrail are different.
Usually the running speed of the handrail should be the same as that of the steps, but there will inevitably be a little error when the handrail and the steps are driven separately.
It is also reasonable to allow fast and not slow. After all, the structure of the human body determines that the range of motion of the arm forward is larger than that of the back. In other words, if the handrail is slower than the stairs, and the body is twisted backward, it is relatively easier to stand unsteady.
Since it is allowed to be fast and not slow, it is better to be faster.
The escalators in subway stations are often ten or even tens of meters long. Even if the handrail is 1% faster than the pedal, your hand can be pulled out a foot away.
The structure of the handrail is a grooved rubber.
Then think about how the drive wheel drives the handrail: the handrail is stretched on the drive wheel and driven by friction
Due to the elastic deformation of the material, due to the different tension in each area of the arc, there will inevitably be sliding (the tension at the leaving end is small, and the belt tends to shrink), the degree of tightness and load will affect the size of the sliding arc, the specific principle you can Find out about "belt transmission + elastic sliding". In short, due to the existence of elastic slip (and other reasons), the speed of belt rotation cannot be completely precisely controlled, but can only be controlled within a range. This is physically inevitable.
