PLS unit

This article provides an online calculator for the Belt or Roller Mechanism to quickly find the servo’s electronic gear ratio and provide additional simulation information to evaluate whether the system parameters meet the requirements. The steps are as follows:

1. Define user units(PUU), eg, How many PUUs correspond to 1 mm
2. Enter the mechanical Reduction ratio (1:1 without deceleration)
3. Enter the diameter(D) or circumference of the pully, including the belt.
4. Enter Encoder Resolution(PLS), PLS number per turn of the Encoder,ie,when the electronic gear ratio is 1:1, how many PUUs the drive has to receive in order to rotate 1 turn.
5. Press the “Calculate” button to get the numerator and denominator of the E-Gear Ratio
6. Select “Significant digit number“: to specify the numeric width of the numerator,  suggest 6 or above [Note 1].
7. Enter the Line Speed(​​V) of the machine to check if the simulation results meet the requirements ?

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In this article, the formula for the electronic gear ratio of the servo drive for the screw mechanism is derived. The principle of deciding the gear ratio is to first determine the position unit PUU (Pos of User Unit), must be easily observed, usually PUU = 1 or 10 μm, and then calculate the corresponding Gear ratio. Instead of deciding on the gear ratio and then calculating the length of a PUU, otherwise it is asking for trouble (refer to the PUU concept). First, the symbol is defined as follows :

• PUU corresponding to 1 mm (P): How many PUUs respect to 1 mm
• Mechanical reduction ratio (N1 : N2): N1 <= N2 for Deceleration
• Turns of screw rotates (REV): uppercase
• Turns of motor rotates(rev): lowercase, rev = REV ×(N2/N1)
• Pitch of the screw(Pitch): the mechanical movement corresponds to 1 turn of the screw(mm/REV)
• Encoder resolution (R): PLS number per turn of encoder(PLS/rev )
• Electronic Gear Ratio (Num/Den): Scaling factor from PUU to PLS

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