1. Core Concepts of Positioning Control
1. Relative Positioning (Incremental Positioning)
Definition: Move a specified number of steps based on the current position
Instruction: PLSY (Pulse Frequency Output)
– Requires manual origin point recording
– Suitable for repeated relative movements
– Weaker anti-interference capability
2. Absolute Positioning (Absolute Positioning)
Definition: Directly move to a preset absolute coordinate position
Instruction: DZRN (Return to Origin with DOG Search)
– Relies on origin point sensor (DOG signal)
– High positional accuracy
– Supports power-off memory
2. Comparison of Core Instructions
|
Comparison Item |
Relative Positioning |
Absolute Positioning |
|
Instruction |
PLSY K Frequency Y0 |
DZRN K Target Position Y0 Y1 |
|
Reference Point |
Current Position |
Origin Point Sensor (X1) |
|
Control Method |
Pulse Count |
Target Coordinate |
|
Typical Application |
Material Handling on Production Lines |
Tool Positioning on Machine Tools |
|
Accuracy |
Depends on Encoder Resolution |
1 Pulse |
3. Practical Case of Relative Positioning
Case 1: Material Handling on Production Line
Control Requirements:
– Move 5000 pulses for each material handling
– Speed 1000Hz
// Initialization
MOV K0 D8140 // Clear pulse count
// Relative Positioning
PLSY K1000 Y0 // Output 1000Hz pulses
MOV K5000 D8142 // Set pulse count
Parameter Explanation:
– D8140: Current value of pulse output (low byte)
– D8142: Current value of pulse output (high byte)
4. Practical Case of Absolute Positioning
Case 2: Robot Arm Return to Origin
Control Requirements:
– Automatically find the origin after startup (X1 sensor)
– Position to absolute location of 100000 pulses
// Return to Origin
DZRN K100000 Y0 Y1 // Target position, pulse output Y0, direction Y1
LD X1 // Origin sensor signal
OUT Y2 // Positioning complete signal
Parameter Explanation:
– K100000: Absolute target position
– Y1: Direction control (0=forward, 1=reverse)
5. Advanced Application Techniques
1. Dynamic Speed Adjustment
// Change speed in real-time based on the value of D100
MOV D100 D8140 // Modify pulse frequency register
2. Multi-Axis Synchronous Positioning
// Move two axes to target position simultaneously
DZRN K200000 Y0 Y1 // First axis
DZRN K300000 Y2 Y3 // Second axis
3. Acceleration and Deceleration Control
// Smooth start and stop (acceleration/deceleration time 500ms)
PLSR K2000 K500 D10 Y0 // Maximum frequency 2000Hz, acceleration/deceleration time 500ms
6. Common Problems and Solutions
Problem 1: Positioning Overrun
Cause: Target position exceeds mechanical travel
Solution:1. Check limit switches (X2/X3).2. Adjust D8142 pulse count
Problem 2: Return to Origin Failure
Cause: Abnormal origin sensor signal
Solution:1. Confirm correct wiring of X1.2. Adjust DOG signal trigger position
Problem 3: Pulse Loss
Cause: Excessive load or high speed
Solution:1. Reduce operating speed (K value).2. Increase mechanical rigidity
7. Selection and Configuration Recommendations
1. Hardware Selection
|
Requirement |
Recommended Model |
Description |
|
High-Speed Positioning |
FX3U-32MT/ES-A |
Transistor output, 100kHz |
|
High Precision Control |
QD75P4 |
Dedicated positioning module |
|
Multi-Axis Control |
L Series/L02CPU |
Supports up to 16 axes |
2. Parameter Settings
|
Parameter Number |
Function |
Recommended Value |
|
D8140 |
Pulse Frequency (Hz) |
1000-10000 |
|
D8141 |
Pulse Frequency (Hz) |
High byte 0 |
|
D8142 |
Pulse Count (low byte) |
Target Position |
|
D8143 |
Pulse Count (high byte) |
0 |
8. Summary and Expansion
✅ Relative Positioning: Suitable for simple repetitive movements, flexible programming
✅ Absolute Positioning: Suitable for high-precision fixed position control, requires origin calibration
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