Delta Computer Systems TMC 188/40 Series Manual page 25

TMC 188/40 Motion Control Module
This bit indicates the transducer is not responding with valid data at least once every 10
milliseconds. The transducer data received is compared with previous data. If the two
readings differ by more than 500 counts (1600 if the Q is option used), the new reading is
assumed to be an error. When an error is detected the MCM makes an emergency stop,
putting the axis in open loop and setting the drive output to the null value for that axis. It also
makes the corresponding front panel axis LED (light emitting diode) glow red. Since the axis
is in open loop mode, it will drift due to changes in the valves null value.
NOTE: The TRANSDUCER NOT RESPONDING bit (bit 6 of the STATUS word) is NOT latched.
Transducer errors will always cause emergency stops, but with intermittent errors bit 6 may
be cleared before the P/C detects it. In this case the HALTED bit will be set, but the axis
will drift because of null changes in the valve.
Bit 5 - VALVE OUT OF NULL
Normally, when the drive output is zero volts or zero mA, the axis will not move. In hydraulic
applications valves sometimes get dirty and the axis will move even when the drive output is
zero. The Motion Control Module compensates for this problem, but if more than 10 percent
of maximum drive output (±205 counts) is required to hold a static position this error bit is set.
Bit 4 - OVERDRIVE
This bit is set when the calculated drive output exceeds the output range. Usually this error
means the system does not have enough power to drive the axis at the requested speed.
During the error the TMC 188/40 sets the drive output to maximum. The OVERDRIVE bit is
latched and is cleared when a new command is issued.
Bit 3 - LEAD ERROR
LEAD is the condition where the ACTUAL POSITION gets ahead of the TARGET POSITION.
This bit is set when the ACTUAL POSITION leads the TARGET POSITION by more than the
amount specified by the MAXIMUM ERROR parameter. Lead errors can occur if the FEED
FORWARD is too high or the axis response is too slow to respond to the output while
ramping down. In the first case, the FEED FORWARD should be decreased. In the second
case, the FEED FORWARD ADVANCE should be increased, or the DECELERATION RAMP
should be lengthened. The LEAD ERROR bit is latched and is cleared when any new
command is issued.
Bit 2 - LAG ERROR
LAG is the condition where the ACTUAL POSITION falls behind the TARGET POSITION.
This bit will be set when the ACTUAL POSITION lags the TARGET POSITION by more than
the amount specified by the MAXIMUM ERROR parameter. Lag errors can occur if the
FEED FORWARD is too low or the FEED FORWARD ADVANCE is set too high. In the first
case, the FEED FORWARD should be increased. In the second case, the FEED FORWARD
ADVANCE should be decreased. The LAG ERROR bit is latched and is cleared when a new
command is issued.
Bit 1 - PARAMETERS INITIALIZED
This bit is set after a parameter or 'P' command is sent to the TMC 188/40. Until this bit is set
the axis will not respond to any GO or „G‟ commands. This bit is reset whenever the module
is reset.
Delta Computer Systems, Inc. 360/254-8688
Motion Control Parameters
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