Units for Position, Velocity, Acceleration and Deceleration

The PLCopen definition uses as unit for position an abstract unit u, for velocity u/s (u per second) and for acceleration u/s2 (u per squared second). So it does not matter which unit is selected, but they need to be in certain relations. To get more information, Technical Units (Link setzen). The ACSM1 supports this strategy. Adjustments have to be made in group 60. As a constraint, it has to be considered that although the values are in LREAL-Format at the Function Block, they will be transferred as 32-Bit Integer so the 32-Bit Integer defines the limits.

Parameters for unit adjustment
Parameter Name Value Mnemonic Comment
POS FEEDBACK
60.01 POS ACT SEL 0, 1   Depends on the drive configuration.
60.02 POS AXIS MODE 0, 1   Depends on the drive configuration.
60.03 LOAD GEAR MUL     Realization with ACSM1 on PROFIBUS-DP network
60.04 LOAD GEAR DIV     Realization with ACSM1 on PROFIBUS-DP network
60.05 POS UNIT 0, 1, 2, 3 REVOLUTION, DEGREE, METER, INCH Determines the abstract unit u.
60.06 FEED CONST NUM     Scaling for speed.
60.07 FEED CONST DEN    
60.08 POS2INT SCALE   Power of ten Scaling for position (u/s)
60.09 POS RESOLUTION     Determines the number of bits used for one revolution. Should be at least 16. The Bits remaining of the 32 Bit integer is used for the count of whole revolutions.
60.10 POS SPEED UNIT 0 u/s Speed in units per second or minute or hour.
60.11 POS SPEED2INT   Power of ten Scaling for speed (rev/s)
60.12 POS SPEED SCALE 1   Scaling for speed, acceleration and deceleration.
60.13 MAXIMUM POS     Depends on the drive configuration.
60.14 MINIMUM POS     Depends on the drive configuration.
60.15 POS THRESHOLD     Depends on the drive configuration.

Some examples:

  • The encoder has 1024 Bits per evolution, that are 10 Bits (not relevant for PLCopen),
  • The load moves 40 mm per revolution,
  • The abstract unit u should be mm.

The following table shows the adjustment which are relevant for this configuration:

Example for Unit Adjustment
Parameter Name Value Mnemonic Comment
60.05 POS UNIT 2 METER Determines the abstract unit u.
60.06 FEED CONST NUM 40   Scaling for speed.
60.07 FEED CONST DEN 1000  
60.08 POS2INT SCALE 1000 1000 (Power of Ten). Scaling for position.
60.09 POS RESOLUTION 16 18 Determines the number of Bits used per revolution. (Should be at least 16). Bits used for number of whole revolutions is (32 -18 =14) No influence on PLCopen.
60.10 POS SPEED UNIT 0 u/s Units per Seconde (per minute, per hour).
60.11 POS SPEED2INT 1000 1000 (Power of Ten) Scaling for speed.