Travel distance control

The travel distance control function can be activated in the CoE. Starting from the current counter value, a target counter value is automatically approached via ramps, taking into account a maximum driving frequency, and the corresponding pulses are output at the outputs. The output frequency thereby changes in accordance with the current counter value.
When the preset counter value is reached, the terminal switches the frequency to zero. The output of an exact number of pulses is only possible with this "travel distance control" function.

The sequence is determined by several factors, see figure. Before parameterizing the travel distance control, it is recommended to carry out a CoE reset "Restoring the delivery state" in order to rule out side effects.

The sequence and the associated parameters are listed in following table; in enhanced operation mode some parameters are no longer in the CoE, but can be linked as process data.

Phase

Normal operation mode

Enhanced operation mode

Parameterization

Activate travel distance control

0x8000:0A = TRUE

0x8010:0A = TRUE

Basic ramp frequency (10 Hz / 1 kHz)

0x8000:07 = ?

0x8010:07 = ?

Ramp time constant "rising" t1 [Δ/sec]

0x8001:04 = ?

0x8010:14 = ?

Maximum driving frequency f1

0x8800:02 = ?

---

Ramp time constant "falling" t3 [Δ/sec]

(> 1.1 * ramp time constant “rising” t1 see note!)

0x8001:05 = ?

0x8010:15 = ?

Output frequency f2

0x8001:07 = ?

0x8010:17 = ?

Trip

Specify target position

0x8800:01 = ?

PDO: TargetCounterValue = ?

Trip start

CW.2 = TRUE

PDO: Control.GoCounter = TRUE

Maximum driving frequency f1

---

PDO: FrequencyValue <> 0

Reset

 

CW.2 = FALSE

PDO: FrequencyValue = 0

 

 

PDO: Control.GoCounter = FALSE

Travel distance control 1:

Setting of “Go counter” in enhanced operation mode

In the case of travel distance control in enhanced operation mode, the "Go counter" bit must be set at the same time or before specifying the "Frequency value".

If the "Go counter" bit is not set and the "Frequency value" is not equal to 0, then travel distance control is not active and clock pulses are already output!

Travel distance control 2:

Ramp time constant

The "real" ramp time results from the multiplication of the basic ramp frequency with that of the rising/falling ramp time constant.

Travel distance control 3:

Steepness of the falling ramp

In order to travel to a destination with precision, it is necessary that the time constant for the falling ramp is greater than that of the rising ramp by a certain factor. This is necessary so that the slowing down frequency is reached before the final counter state, so that the terminal does not drive up to the end point at full speed.

To explain in more detail:
The EL2521 calculates the number of steps that are still to be taken in time t2 from time t1 and from the number of steps that have been taken. The calculation for stopping assumes the same number of steps as that found for starting up.
The downward ramp must be a little steeper, approx. 10 %, so that it is possible to reach the destination exactly in the remaining time t3 + t4 + t5. This relationship changes with the maximum frequency.

Example of a travel distance ramp

Travel distance control 4:
Phases of the travel distance control

By way of example, the recording of a short real travel distance ramp is shown here together with the sample program used for it:
Travel distance control 5:download
The short step sequence resets the current counter value to 0 and then drives to the target position 65. In the System Manager file the EL2521-xxxx is set to the appropriate CoE values for this example via the StartUp parameters.

Travel distance control 6:
Sample travel distance control program

The result is the output of a variable frequency up to the target position 65.

Travel distance control 7:
Oscilloscope recording of the pulse sequence