Selecting Units for Your Application

Units are configured independently for each axis on the drive. The WorkBench Units view (accessible from the View Tree under Axis > Settings) helps to select the correct units for the axis mechanics.

There are three primary measures of motion: position, velocity, and acceleration. You must first choose units of measurement for each of these, and then enter the details of the mechanics in order to scale the chosen units appropriately.

The settings for units are automatically applied. The unit settings in the drive will reflect last settings made in the Units screen before exiting. To save settings into the non-volatile memory of the drive, click the Save to Device button in the toolbar.

Type of Mechanics

To set the units in the drive for a particular application, first select the type of mechanics present.

Mechanical Details

Once the chosen units of measurement is selected, the details of the mechanics need to be entered to set the scaling of the chosen units.

In this example, a lead screw with a 10 mm lead and a 5:1 gearbox has been selected. A 10 mm lead means the load will traverse 10 mm for every turn of the screw. A scale factor is applied based on the values entered for the chosen mechanics. This scaling is done through AXIS#.UNIT.PIN and AXIS#.UNIT.POUT , which are automatically adjusted when the mechanics values are entered.

AXIS#.UNIT.PIN is calculated as follows:

10 mm/screw turn  * 1 screw turn/5 motor turns  = 2 mm/motor turn

Position Units

AXIS#.UNIT.PROTARY sets the position units for rotary motor types.

Rotary Position Units

Value

Units

0

counts

1

rad

2

degs

3

Custom Units

4

counts 16-bit

Linear Position Units

Type

Description

0

counts

1

Millimeters (mm)

2

Micrometers (µm)

3

Custom Units (PIN/POUT) per revolution

4

counts 16-bit

Position Range

Min/Max position range depends on the units used.

Units

Min

Max

counts

-9,007,199,254,740,992

9,007,199,254,740,992

counts 16-bit

-137,438,953,472

137,438,953,472

rads

-13,176,794.633

13,176,794.633

degs

-754,974,720

754,974,720

Custom Units

varies

varies

mm

-67,108,864

67,108,864

µm

-67,108,864,000

67,108,864,000

Velocity Units

AXIS#.UNIT.VROTARY sets the velocity units for rotary motor types.

Rotary Velocity Units

Value

Units

0

RPM

1

RPS

2

deg/s

3

(custom units)/s

4

rad/s

Linear Velocity Units

Type

Description

0

counts/s

1

Millimeters/s (mm/s)

2

Micrometers/s (µm/s)

3

(custom units)/s

Velocity Range

Min/Max velocity range depends on the units used.


  • This limit needs to account for overshoot and velocity ripple. The largest commanded value should be no more than 90% of the velocity limit

Units

Min

Max

RPM

-30,000

30,000

RPS

-500

500

deg/s

-180,000

180,000

Custom Units

varies

varies

counts/s

-2,147,483,648

2,147,483,648

mm/s

-16,000

16,000

µm/s -16,000,000 16,000,000
Rad/s -3,141.593 3,141.593

Acceleration Units

AXIS#.UNIT.ACCROTARY sets the acceleration units for rotary motor types.

Rotary Acceleration Units

Type Description

0

RPM/s  

1

RPS/s  

2

deg/s2

3

(Custom Units)/s2

4

rad/s2

Linear Acceleration Units

Type

Description

0

counts/s2

1

mm/s2

2

µm/s2

3

(Custom Units)/s2

Acceleration Range

Min/Max acceleration range depends on the units used.

Units

Min

Max

RPM/s

0.224

240,000,008.192

RPS/s

0.004 4,000,000

deg/s2

1.341 1,439,999,938.616

(Custom Units)/s2

varies

varies

rad/s2 0.023 25,132,740.608

counts/s2

16,000,000 17,179,869,184,000,000

mm/s2

0.119 128,000,000

µm/s2

119.209 127,999,999,475.712

Custom Units

The drive uses full 32-bit quantization for internal calculations regardless of unit settings. User units settings will not affect performance, resolution, or accuracy of the servo system.

Choose “3-Custom”, and then select your desired position units, for example, millimeters.

Related Parameters

AXIS#.UNIT Parameters

DRV.NVSAVE  

AXIS#.MOTOR.TYPE