Equipments (Devices) > PLC200 > Program > Motion

Block for speed control with ramp generation and specified number of pulses.

Ladder Representation

MW_PlcSpeed2_G0

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	EN/Execute	BOOL	Block enabling
	AxisNumber	CONST	Selected axis
	Direction	BOOL	Movement direction
	TargetFrequency	DWORD DINT	Final pulse frequency [Hz]
	DeltaTime	DWORD	Step time until reaching the target frequency [ms]
	DeltaFrequency	DWORD DINT	Frequency variation of each step [Hz]
VAR_OUTPUT	DONE	BOOL	Output enabling
	Active	BOOL	Indicates that the block is active
	Busy	BOOL	Indicates that another block is using the selected output
	Error	BOOL	Indicates that an error occurred when calling the block
	ErrorID	BYTE	Indicates the error generated
VAR	MW_PlcSpeed2_INST_0	MW_PlcSpeed2	Instance of access to block structure

Operation

This block, when it detects a rising edge on the EN input, starts generating pulses for the selected axis with a frequency starting from 0 Hz up to the desired frequency (targetFrequency) (between 0 and 300 kHz).

At each time step (deltaTime), the frequency is incremented by deltaFrequency until it reaches the desired frequency (targetFrequency).

The pulses are only interrupted when a Stop block is called.

While a Stop block is not called, the "Active" output remains at a high level.

When EN is FALSE, DONE remains FALSE. The DONE output is activated when the block successfully completes execution (Stop block called), remaining at a TRUE level until EN becomes FALSE.

The minimum number of pulses that can be generated is 2.

If this limitation is not respected, no pulse is generated.

The minimum number of pulses that can be generated per step is 2.

If this limitation is not respected, the frequency ramp is not generated; in other words, upon enabling the block, the pulse frequency starts directly at the targetFrequency value.

The MW_PlcChangeSpeed block can be used in conjunction to change the output frequency during the execution of this block. Refer to the help section of the MW_PlcChangeSpeed block for more information.

NOTE!

If other PWM blocks running use the same output, the one called first will have priority and the "Busy" output is set.

The figure below shows the default operation of the block, without using the MW_PlcChangeSpeed block together.

MW_PlcSpeed_example04

If there is any error in the execution, the Error output is enabled and ErrorID displays an error code according to the table below.

Code	Description
0	Executed successfully
1	Axis control not enabled
2	Invalid number of steps
3	Invalid ramp
4	Configuration error

NOTE!

Stepper motor control must be enabled for the selected axis. Look at the user manual and parameter manual.

Example in Ladder

MW_PlcSpeed_example01

In the example above, the "start" contact enables a pulse signal on axis 1 with an initial frequency of 0 Hz and a duty cycle of 50%. The frequency will be incremented by 2000 Hz every 100ms until it reaches 20000 Hz, meaning the total ramp time will be 1 second. After that, the block will continue generating pulses until a "Stop" block is called.

MW_PlcSpeed_example02

In the example above, the "start" contact enables a pulse signal on axis 1 with an initial frequency equal to targetFreq. The ramp will not be generated because it is not possible to produce 2 pulses at 10 Hz within the 100ms step time. After that, the block will continue generating pulses until a "Stop" block is called.

Example in ST

The example below displays instructions for applying the functional example in ST language.

VAR

start : BOOL := 0;

nPulses : DWORD := 100000;

targetFreq : DWORD := 20000;

stepTime : DWORD := 100;

stepFreq : DWORD := 2000;

MW_PlcSpeed2_INST_0 : FB_MW_PlcSpeed2;

END_VAR

MW_PlcSpeed2_INST_0.EN := start;

MW_PlcSpeed2_INST_0(

AxisNumber:=1,

Direction:=false,

TargetFrequency:=targetFreq,

DeltaTime:=stepTime,

DeltaFrequency:=stepFreq);

COIL := MW_PlcSpeed2_INST_0.DONE;