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ASDA-A3

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Motion Control

7.1.2 Monitoring variables of PR mode

The PR mode provides four monitoring variables for the servo command and feedback:

command position (PUU), PR command end register, feedback position (PUU), and position

error (PUU). These are described as follows:

1. Command position (PUU): monitoring variable code 001. The target position of the motion

command generated per scan cycle during servo operation (updated every 1 ms),

simplified as Cmd_O (Command Operation).

2. PR command end register: monitoring variable code 064. The target position of the PR

command, simplified as Cmd_E (Command End). When a command is triggered, the

servo drive calculates the target position and then updates to PR command end register.

3. Feedback position (PUU): monitoring variable code 000. The encoder feedback position

(coordinates), simplified as Fb_PUU (Feedback PUU).

4. Position error (PUU): monitoring variable code 002. The deviation between the command

position (PUU) and the feedback position (PUU), simplified as Err_PUU (Error PUU).

How these four monitoring variables work is shown in Figure 7.1.2.1. After the servo issues a

Position command, the servo sets the position of Cmd_E once the target position data is

acquired. The motor operates to the target position based on the PR path setting. Cmd_O

calculates the amount of command deviation in each fixed cycle and sends it to the servo drive,

where it is treated as a dynamic command. Fb_PUU is encoder feedback position and Err_PUU

is the deviation of Cmd_O minus Fb_PUU.

Before

command

issued

After

command

issued

Err_PUU

Fb_PUU

Cmd_O

Cmd_E

Err_PUU

Fb_PUU

Cmd_O

Command in

execution

Err_PUU

Fb_PUU

Cmd_O

Command

completed

Motor

positioned

Cmd_E

Cmd_E

Err_PUU

Fb_PUU

Cmd_O

Cmd_E

Err_PUU

Fb_PUU

Cmd_O

Cmd_E

Figure 7.1.2.1 Timing diagram for PR mode monitoring variables

7

7-7

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