Selecting Units for Your Application

Units are configured independently for each axis on the drive. The WorkBench Units view (accessible from the axis Settings tree) 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 nonvolatile 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 are established, the details of the mechanics need to be entered to establish 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

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

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

Velocity Range

Min/Max velocity range depends on the units used.

Units

Min

Max

RPM

-15,000

15,000

RPS

-250

250

deg/s

-90,000

90,000

Custom Units

varies

varies

counts/s

1,073,741,824,000

1,073,741,824,000

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

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

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