Servosila-Device-Reference-0xA020192

6
Servo: Kp Hz/
rad
The "Servo: Kp" parameter defines a proportional relationship between a
speed of servo motion and a distance to a target position the servo is
commanded to move to. The closer the servo approaches the target
position, the slower it moves. This proportional relationship is governed by
the "Servo: Kp" parameter. The speed becomes 0.0 whenever the target
position is reached, and the motor stops.
Example: lets assume that "Servo: Kp" is configured as 20 Hz/rad. If the
current distance to the target is 2.0 rad, the servo starts traveling with a
speed of 20 * 2.0 = 40 Hz. As the servo's shaft travels along, the distance to
the target position eventually gets reduced to 0.5 rad, so the speed at that
point drops to 20 * 0.5 = 10 Hz. Whenever the servo reaches its
destination, the distance to the target becomes 0.0 rad, so the speed drops to
0.0 Hz, and the motor stops.
The distance to the destination (measured in encoder counts), is first
normalized by dividing it by the encoder's resolution and then by
multiplying it by (2*PI) rad. This is done for both ROTARY and LINEAR
encoders. For example, if a servo encoder has a resolution of 65536 counts,
and the distance to the destination is 1000 counts, then the normalized
distance would be 1000 / 65536 * (2*PI) = 0.095873799 rad. This
normalized distance is multiplied by the pre-configured "Servo: Kp" factor
to determine the speed with which the servo should travel at that point (as
explained above).
The speed is then clamped by comparing it to "Servo: Speed Limit",
another configuration parameter. For example, if the "Servo: Speed Limit"
is set to be 20Hz, then the speed with which the servo travels never gets
higher than 20Hz. In fact, most of the time, the servo travels at this speed
limit until the speed starts dropping linearly upon approaching a target.
All the speeds here are defined in electrical revolutions per second (Hz). To
convert the electrical revolutions per second to servo shaft's revolutions per
second, divide it by the number of pole pairs and then divide it by the
gearbox's reduction ratio. For example, assuming the speed is 20 Hz
(electrical), Poles Number is 8, and the gearbox reduction ratio is 100, then
the corresponding speed in servo shaft's revolutions per second is 20 / (8/2)
/ 100 = 0.05 revolutions per second, which is 0.05 * 60 = 3.0 RPM.
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7
Servo: Speed Limit
(Electrical
Frequency)
Hz The "Servo: Speed Limit" parameter sets a maximum speed with which the
servo travels to its target position. The servo moves at this speed limit most
of the time, only linearly reducing the speed before arriving to its target
destination. The period when servo is moving with this maximum speed is
called a "constant speed" segment of the servo motion. The limit is used to
clamp the speed computed using "Servo: Kp" parameter. Note that the
speed is defined in electrical Hz (electrical revolutions per second).
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8 Direct Drive & Hz The "Direct Drive: Speed Limit" parameter defines a speed at which the FLOAT32,
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