DSP resolver user manual
User Manual
Version 1.15
index
sub
type
access
variable
possible
values
notes
0x2106
0
U8
RW
co_CAN_period
2, 5, 10
Internal timer interval
in milliseconds
Table 7.5: Object dictionary variables related internal timing configuration
7.1.5
Speed calculation
The device calculates the electrical rotational speed of the sensor. The speed information is
available in
co_speed_value[1]
object (signed 16 bit variable in sub 1 of 0x6030) and in
co_32bit_speed_value
object
(0x2010). The latter object is an addition to the device profile
to allow using bigger resolution also with high rotation speeds.
Unit of the speed value is measuring units per second. The value range for the calculated
speed is -32768 to 32767 for 16 bit object and -2147483648 ... 2147483647 for 32 bit
object. If the default resolution (36000) is used the maximum measurable speeds are +-0,91
and +-59652 electrical revolutions per second. The latter one exceeds naturally sensor's
maximum allowed rotation speed.
The measureable speed range can be widened by decreasing the
co_units_per_revolution,
which decreases also the resolution.
User can smoothen the output of the speed calculation by increasing the length of the
co_speed_buffer
(unsigned 16 bit variable at 0x2003 in the object dictionary). The
co_speed_buffer
object defines how many internal timer periods (
co_CAN_period
) are used
as a difference time for the speed calculation. The actual difference time of the speed
calculation can be read from the
co_speed_difference_time
object (unsigned 16 bit variable
at 0x2002 in the object dictionary). The difference time is a calculated as
co_speed_buffer
times
co_CAN_period.
Ensure that the
co_speed_difference_time
newer exceeds the minimum time that the half
electrical revolution of the sensor consumes. Otherwise negative speed may suddenly
change to positive! With 2 ms
co_CAN_period
and 30 slots
co_speed_buffer
the difference
time is 60ms. For single speed (1X) sensor with resolution of 36000 this means that the
maximum mechanical rotational speed is then 3000 degrees/sec. For 3x sensor the electrical
rotational speed is one third of the mechanical speed. This means that the maximum
mechanical speed for 3X is 1000 degrees with the same settings.
To use the speed value in real time either of the speed objects should be mapped to a
transmit PDO. See PDO mapping for instructions on how this can be done.
Copyright
©
Axiomatic Technologies Oy
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