User manual

TMCM-1180 and PD86-1180 TMCL Firmware V4.42 Manual (Rev. 1.08 / 2012-NOV-20) 105
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8.3 stallGuard2
The module is equipped with TMC262A-PC motor driver chip. The TMC262A-PC features load measurement that
can be used for stall detection. stallGuard2™ delivers a sensorless load measurement of the motor as well as
a stall detection signal. The measured value changes linear with the load on the motor in a wide range of
load, velocity and current settings. At maximum motor load the stallGuard™ value goes to zero. This
corresponds to a load angle of 90° between the magnetic field of the stator and magnets in the rotor. This
also is the most energy efficient point of operation for the motor.
Figure 8.4: Principle function of stallGuard2
Stall detection means that the motor will be stopped when the load gets too high. It is configured by axis
parameter #174.
Stall detection can also be used for finding the reference point. Do not use RFS in this case.
Mixed decay should be switched off when stallGuard2™ operational in order to get usable results.
8.4 Using the RS485 interface
With most RS485 converters that can be attached to the COM port of a PC the data direction is controlled by
the RTS pin of the COM port. Please note that this will only work with Windows 2000, Windows XP or
Windows NT4, not with Windows 95, Windows 98 or Windows ME (due to a bug in these operating systems).
Another problem is that Windows 2000/XP/NT4 switches the direction back to receive too late. To overcome
this problem, set the telegram pause time (global parameter #75) of the module to 15 (or more if needed) by
issuing an SGP 75, 0, 15 command in direct mode. The parameter will automatically be stored in the
configuration EEPROM.
For RS232 set the telegram pause time to zero for maximum data throughput
motor load
(% max. torque)
stallGuard2
reading
100
200
300
400
500
600
700
800
900
1000
0 10 20 30 40 50 60 70 80 90 100
Start value depends
on motor and
operating conditions
Motor stalls above this point.
Load angle exceeds 90° and
available torque sinks.
stallGuard value reaches zero
and indicates danger of stall.
This point is set by stallGuard
threshold value SGT.