One picture to understand all pulse sources-A2 servo block diagram

Delta A2 servo has many pulse sources, such as main encoder, auxiliary encoder, pulse command, which can be used for positioning command (PT mode), high-speed capture/comparison, E-CAM master pulse and so on. In addition, the various pulse sources can be also output from CN1 for the host controller to count. Due to the large number of parameters, it is often confusing. This article draws the relevant functions and parameters into a block diagram to facilitate quick and comprehensive understanding for readers’ reference.

Driver pulse input source

As shown in the figure above, the pulse input source is on the left, which are explained as follows:

  • Main encoder:input from the CN 2 interface, the driver obtains the position of the encoder through communication, the unit is PLS, used to indicate the position of the motor, mainly used for servo position loop/speed loop control, because the resolution is too high, it is not suitable for users observe. The user can define the unit by himself, called PUU (Position of User Unit) [Note 1] , and then calculate the corresponding electronic gear ratio (P1-45/P1-44) , and convert the PLS unit to the PUU unit to suit the user (host controller) use. After homing to the origin, the PUU position coordinate is established, which can be known from the monitoring variable V00h, which is the position unit used in the PR/CANopen mode.
  • Auxiliary encoder:input from the CN5 interface (observe P5-17), which is mainly used to connect to an optical scale as a fully closed loop control. When the feedback direction of the optical scale is reversed, the fully closed loop will be unstable. You can swap the CN 5 A/B phase signal line or modify the parameter P1-74.Z. This pulse signal can also be used for high-speed capture/comparison, or as a E-CAM master source.
  • Pulse command:input from the CN1 interface (observe P5-18). It is mainly used as a position command in PT mode. It can also be used for high-speed capture/comparison, or as a E-CAM master source. Delta A2-M/U Servo CN 1 contains two sets of pulse command sources [Note 2] , divided into general group (PULSE/SIGN) and high-speed group (HPULSE/HSIGN). The general group can be connected to open-collector or differential signals, while the high-speed group can only be connected to differential signals, but the acceptable pulse frequency is higher. It is said that the anti-interference is better than the general group. The pulse wave type (CW/CCW, pulse wave/direction, A/B phase) can be selected through parameter P1-00.X. Normal/high-speed group pulse wave can be selected through parameter P1-00.U. When the pulse direction is reversed, it can only be corrected by rewiring, not by changing the parameters.

Driver pulse output selection

As shown on the right side of the above figure, the driver outputs pulse wave through the OA/OB contact of CN 1. When the direction of the pulse wave is reversed, it can be modified by parameter P1-03.Y, it is not necessary to modify the wiring. The above three pulse sources can be selected for output by parameter P1-74.Y.

  • 0:CN 2 Main encoder:Because it is through communication, there is no physical pulse, and it cannot be directly output from CN 1. Therefore, the drive will generate (P1-46 x 4) pulses per motor revolution to output. This pulse is also used for high-speed comparison when the main encoder is selected as the comparison source.
  • 1:CN 5 Auxiliary encoder:When using full closed loop control, it is more reasonable to choose to output the position pulse of the optical scale to the host controller for counting.
  • 2:CN 1 Pulse command:When the same pulse command needs to be output to multiple drives, the pulse can be output through CN 1 and connected to the pulse input of the next drive in series to avoid signal attenuation and easier wiring, called pulse bypass.

[Note 1] To calculate the corresponding electronic gear ratio according to PUU, please refer to the calculation tool:

[Note 2] The CN1 of Delta A3-L/M servo has only one set of pulse input, which supports open collector (single-phase up to 200 KHz) and differential signals (single-phase up to 4 MHz).


Leave a Reply