Elmo HARmonica 190, 14.9.3Device failures, and the CPU dump, Sensor faults Motor cannot move

HARSFEN0602ElmoHARmonicaSoftwareManual	PRELIMINARYDRAFT
RM=1 with modulo-counting position feedback.

14.9.3Device failures, and the CPU dump

Programming• errors may also lead to CPU overloading. In that case the CPU will not be able to complete its control tasks on time, and the internal CPU stack shall overflow.

Humans have programmed the Amplifier. The programmers, however hard they try, cannot completely avoid bugs in their code. Programming bugs may lead to CPU exceptions, like an attempt to divide in zero,

or an attempt to access variable that does not exist.

For this reason, the Amplifier has traps for CPU exceptions and for stack overflow. When the Amplifier traps an exception (hope it never does), it does the following: Shut off all the controller activity. Any motion is aborted to freewheeling.

It writes down the exact trap that was activated, and the address in the firmware that caused the exception. After the exception, communication is still enabled, so the Amplifier can be asked what had happened. Them motor, however, cannot be set again to work until the Amplifier is rebooted.

A CPU exception is detected using the CD and the SR command. The SR command only indicates that an exception occurred. The CD (CPU dump) command gives the details.

The CD command reports as follows:

Null Address	The code address in the firmware when the exception occurred (0 if o.k.)
Failure address	The code address in the firmware when the stack overflow has been detected (0
	if o.k.)
Called Handler	A string describing the type of exception. This may be:
	A divide by zero attempt
	An attempt to access a non existing variable
	Many other possible exceptions.
	This string is “none” if no exception was trapped.
	Table 14-3 - CD Reported Elements

The CPU dump also returns the database status, as described above.

14.10Sensor faults

14.10.1The motor cannot move

When the motor is commanded to move to somewhere, and it for some reason it cannot do it, the reasons may be:

The motion sensor is faulty – the motor moves but motion is not detected. In this case AC motors will be generally stop, since the stator field will remain stationary.

The motor is faulty, or there is other mechanical failure that prevents the motor from moving. The controller filter is poorly tuned. In this case the motor torque may wildly oscillate in high frequency, but the motor will hardly move at all.

These situations are identified by:

The motor average torque is high

•The motor is stationary, or the movement is very slow.

The facts that the motor is commanded to high torque but is not moving are not always an error indication. In some applications, as thread fastening, it is perfectly legitimate for the motor to reach a mechanical motion limit.

The Amplifier user is asked to define whether a high torque stopped motor is a fault or not. If the parameter CL[2] is less than 2, a high torque that does not lead to motion is not considered a fault. If the parameter CL[2] is 2 or more, then a high torque stopped motor, detected for at least 3 continuous seconds, is considered a fault. The motor is set to off (MO=0) and MF=0x200000. The time constant of 3 seconds is

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