Motion engine control

AN4355

10/25

DocID025240 Rev 2

2.3

Stop commands

The motor can be stopped through the stop commands. These commands can be sent at

any time and they are executed immediately.

The SoftStop command stops the motor fitting the deceleration value of the speed profile

whereas HardStop command stops the motor immediately (infinite deceleration).

The SoftHiZ and HardHiZ commands operate similarly, but the power bridges are disabled

as soon as the zero speed is reached (the high impedance status is forced).

2.4

Initializing position using GoUntil and ReleaseSW

commands

The Information stored into the ABS_POS register can be initialized according to an

external position sensor. In this way a relation between ABS_POS value and mechanical

position of the motor is established.

The position initialization sequence, as shown in Figure 7, is the following:

1.

In power-up status, the load position is unknown.

2.

Using GoUntil command the load is moved to the limit switch at high speed.

3.

When the load reaches the limit switch the SW input of the device is forced low. The

motor decelerates and then stops.

4.

Considering the high speed used to approach the load to the limit switch, a significant

error in the positioning could happen.

5.

Using ReleaseSW command the load is moved away from the limit switch at low

speed.

6.

As soon as the threshold position of the limit switch is crossed by the load the SW input

of the device is forced high. The motor stops immediately.

7.

The load is positioned in correspondence to the threshold position of the limit switch

with high precision.