Pulse Train Output (PTO)

Introduction

The PTO function provides up to four pulse train output channels for a specified number of pulses and a specified velocity (frequency). The PTO function is used to control the positioning or speed of up to four independent linear single-axis stepper or servo drives in open loop mode (for example, with Lexium 28).

The PTO function does not have any position feedback information from the process.

The PTO function can be configured on any output channel of the logic controller not already configured for use by another expert function.

Each PTO channel can use up to:

Six inputs, if optional interface signals for homing (ref/index), event (probe), limits (limP, limN), or drive interface (driveReady) are used,
Three physical outputs, if optional drive interface signal is used (driveEnable).

Automatic origin offset and backlash compensation are also managed to improve positioning accuracy. Diagnostics are available for status monitoring, providing comprehensive and quick troubleshooting.

Supported Functions

The four PTO channels support the following functions:

Four output modes, including quadrature
Single axis moves (velocity and position)
Relative and absolute positioning
Automatic trapezoidal and S-curve acceleration and deceleration
Homing (seven modes with offset compensation)
Dynamic acceleration, deceleration, velocity, and position modification
Switch from velocity to position mode and vice versa
Move queuing (buffer of one move)
Position capture and move trigger on event (using probe input)
Backlash compensation (in quadrature mode)
Limits (hardware and software)
Diagnostics

PTO Function Blocks

The PTO function is programmed in EcoStruxure Machine Expert using the following function blocks, available in the M241 PTOPWM library:

Category	Subcategory	Function Block
Motion (single axis)	Power	`MC_Power_PTO`
	Discrete	`MC_MoveAbsolute_PTO`
		`MC_MoveRelative_PTO`
		`MC_Halt_PTO`
		`MC_SetPosition_PTO`
	Continuous	`MC_MoveVelocity_PTO`
	Homing	`MC_Home_PTO`
	Stopping	`MC_Stop_PTO`
Administrative	Status	`MC_ReadActualVelocity_PTO`
		`MC_ReadActualPosition_PTO`
		`MC_ReadStatus_PTO`
		`MC_ReadMotionState_PTO`
	Parameters	`MC_ReadParameter_PTO`
		`MC_WriteParameter_PTO`
		`MC_ReadBoolParameter_PTO`
		`MC_WriteBoolParameter_PTO`
	Probe	`MC_TouchProbe_PTO`
	Probe	`MC_AbortTrigger_PTO`
	Error handling	`MC_ReadAxisError_PTO`
	Error handling	`MC_Reset_PTO`

NOTE: The motion function blocks act on the position of the axis according to the motion state diagram. The administrative function blocks do not influence the motion state.

NOTE: MC_Power_PTO function block is mandatory before a move command can be issued.

WARNING
	UNINTENDED EQUIPMENT OPERATION Do not use the same function block instance in different program tasks. Do not change the function block reference (AXIS) while the function block is executing. Failure to follow these instructions can result in death, serious injury, or equipment damage.

PTO Characteristics

The PTO function has the following characteristics:

Characteristic	Value
Number of channels	4
Number of axes	1 per channel
Position range	-2,147,483,648...2,147,483,647 (32 bits)
Minimum velocity	1 Hz
Maximum velocity	For a 40/60 duty cycle and maximum 200 mA: Fast outputs (Q0...Q3): 100 kHz Regular outputs (Q4...Q7): 1 kHz
Minimum step	1 Hz
Minimum acceleration / deceleration	1 Hz/ms
Maximum acceleration / deceleration	100,000 Hz/ms
Start move IEC	300 µs + 1 pulse output time
Start move on probe event
Change move parameter
Accuracy on velocity	0.5 %
Accuracy in position	Depends on the pulse output time