6.1.2 Positioning speed at the interpolation control. Mitsubishi MOTION CONTROLLERS Q172DCPU

6 POSITIONING CONTROL

6.1.2 Positioning speed at the interpolation control

The positioning speed of the Motion CPU sets the travel speed of the control system.

(1) 1 axis linear control

Travel speed is the positioning speed of the specified axis at the 1 axis positioning control.

(2) Linear interpolation control

Positioning is controlled with the speed which had the control system specified at the interpolation control.

The positioning speed can be set using one of the following three methods at the

2 to 4 axes linear interpolation control:

• Vector speed specification

• Long-axis speed specification

• Reference-axis speed specification

Control method of the Motion CPU control for every specified method is shown below.

(a) Vector speed specification

The Motion CPU calculates the positioning speed of each axis (V 1 to V 2 ) using the travel value (D 1 to D 4 ) of each axis based on the positioning speed

(V) of the setting control system.

Positioning speed of the control system is called the vector speed.

Set the vector speed and the travel value of each axis in the servo program.

Example

2 axes linear interpolation control is shown below.

Axis 2

V

2

V

(10000, 15000)

[Program example]

<K 50>

ABS-2

Axis

Axis

Vector speed

1,

2,

10000

15000

7000

[PLS]

[PLS]

[PLS/s]

0

0

V

1 Axis 1

Axis 1 travel value: D 1 = 10000[PLS]

Axis 2 travel value: D 2 = 15000[PLS]

Vector speed: V = 7000[PLS/s]

The Motion CPU calculates the positioning speed of each axis using the following calculation formulas in the above condition:

Axis 1 positioning speed :

Axis 2 positioning speed :

V = V D / D + D

2

2

V = V D / D + D

2

2

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6 POSITIONING CONTROL

(b) Long-axis speed specification

It is controlled based on the positioning speed (Long-axis speed: V) of the largest travel value axis among address set as each axis.

The Motion CPU calculates the positioning speed of other axes (V 1 to V 3 ) using the each axis travel value (D 1 to D 4) .

Set the long-axis speed and the travel value of each axis using the servo program.

Example

4 axes linear interpolation control is shown below.

Axis 1 travel value: D 1 = 10000[PLS]

Axis 2 travel value: D 2 = 15000[PLS]

Axis 3 travel value: D 3 = 5000[PLS]

Axis 4 travel value: D 4 = 20000[PLS]

[Program example]

<K 51>

Long-axis speed: V = 7000[PLS/s]

In this example, since the reference axis is axis 4 of the largest travel value, it is

ABS-4

Axis

Axis

Axis

1,

2,

Axis

3,

4,

Long-axis speed controlled with the positioning speed specified with axis 4.

The Motion CPU calculates the positioning speed of other axes using the following calculation formulas:

10000

15000

5000

20000

7000

[PLS]

[PLS]

[PLS]

[PLS]

[PLS/s]

Axis 1 positioning speed :

Axis 2 positioning speed :

Axis 3 positioning speed : V = D / D V

The following conversions are performed if the control units of each axis differ.

1) Combination of axes set in [mm] and [inch] a) If the interpolation control units are [mm]

• Travel value: Convert the travel value of axis set in [inch] into [mm] using the formula: inch setting value 25.4.

• Speed : The largest travel value axis is controlled with the longaxis speed and the other axes are controlled with the speed based on the long-axis speed, as the result of conversion. b) If the interpolation control units are [inch]

• Travel value: Convert the travel value of axis set in [mm] into [inch] using the formula: mm setting value 25.4.

• Speed : The largest travel value axis is controlled with the longaxis speed and the other axes are controlled with the speed based on the long-axis speed, as the result of conversion.

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6 POSITIONING CONTROL

2) Discrepancy between interpolation control units and control units

• Travel value: The travel value of each axis is converted into [PLS] unit with the electronic gear of self axis.

• Speed : The largest travel value axis is controlled with the longaxis speed and the other axes are controlled with the speed based on the long-axis speed, as the result of conversion.

The positioning speed is converted into [PLS/s] unit as the long-axis speed with the electronic gear that the interpolation control units correspond to control units.

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6 POSITIONING CONTROL

POINTS

(1) Speed limit value and positioning speed

• The setting speed limit value applies to the long-axis speed.

• Be careful that the vector speed may exceed the speed limit value at the longaxis speed specification.

Example

The following settings at the 2 axes linear interpolation, the vector speed exceeds the speed limit value.

Axis 1 travel value : 100 [PLS]

Axis 2 travel value : 200 [PLS]

Long-axis speed : 50 [PLS/s]

Speed limit value : 55 [PLS/s]

In this example, since the reference-axis is axis 2 of the largest travel value, it is controlled with the speed limit value specified with axis 2.

The positioning speed and vector speed for each axis are as follows:

Axis 1 positioning speed : 100/ 200 50 =

25 [PLS/s]

Axis 2 positioning speed : 50 [PLS/s]

Vector speed :

<K 2>

INC-2

Axis

Axis

Long-axis speed

1,

2,

100

200

50

[PLS]

[PLS]

[PLS/s]

Axis 1 positioning speed

Vector speed

Axis 2 positioning speed

The vector speed exceeds the speed limit value setting of 55.

(2) Relationship between speed limit value, acceleration time, deceleration time

and rapid stop deceleration time.

• The real acceleration time, deceleration time and rapid stop deceleration

time are set by the setting long-axis speed.

Speed limit value

Speed

Positioning speed(long-axis speed)

Rapid stop cause occurrence

1)

2)

5)

6)

3)

4)

Time

1) Real acceleration time

2) Setting acceleration time

3) Real deceleration time

4) Setting deceleration time

5) Real rapid stop deceleration time

6) Setting rapid stop deceleration time

(c) Reference-axis speed specification

The Motion CPU calculates the positioning speed of other axes (V 1 to V 3 ) based on the positioning speed (reference-axis speed : V) of the setting reference-axis using the each axis travel value (D 1 to D 4).

Set the reference-axis No., reference-axis speed and each axis travel value using the servo program.

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6 POSITIONING CONTROL

Example

4 axes linear interpolation control is shown below.

[Program example]

Axis 1 travel value: D 1 = 10000 [PLS]

Axis 2 travel value: D 2 = 15000 [PLS]

Axis 3 travel value: D 3 = 5000 [PLS]

Axis 4 travel value: D 4 = 20000 [PLS]

<K 52>

Reference axis speed: V = 7000 [PLS/s]

Reference axis: Axis 4

In this example, since the reference-axis

ABS-4

Axis

Axis

Axis

Reference-axis

1,

2,

Axis

3,

4,

Reference-axis speed is axis 4, it is controlled with the positioning speed specified with axis 4.

The Motion CPU calculates the positioning speed of other axes using the following calculation formulas:

Axis 1 positioning speed :

Axis 2 positioning speed :

Axis 3 positioning speed :

10000

15000

5000

20000

70000

4

[PLS]

[PLS]

[PLS]

[PLS]

[PLS/s]

POINTS

(1) Reference-axis speed and positioning speed of other axes

• Be careful that the positioning speed of an axis for a larger travel value than the reference-axis may exceed the setting reference-axis speed.

(2) Indirect specification of the reference-axis

• The reference-axis can be set indirectly using the word devices.

(Refer to Section 5.4.2.)

(3) Relationship between speed limit value, acceleration time, deceleration time and rapid stop deceleration time.

• The real acceleration time, deceleration time and rapid stop deceleration time are set by the reference-axis speed setting

Speed

Speed limit value

Positioning speed (reference-axis speed)

Rapid stop cause occurrence

1)

2)

5)

6)

3)

4)

Time

1) Real acceleration time

2) Setting acceleration time

3) Real deceleration time

4) Setting deceleration time

5) Real rapid stop deceleration time

6) Set rapid stop deceleration time

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