time
power
OFF
ON
basic period
50µs
ON period
time
power
OFF
ON
basic period
95%
ON period
time
power
OFF
ON
basic period
5%
ON period
Figure 3.6: The “Pulse Width Modulation”(PWM) motor supply mode is
based on a ratio between the ON time and the total time. The basic switch-
ing frequency is constant.
Each motor controller can perform the control of the speed or the position
of the motor, setting the correct PWM value according to the real speed or
position read on the incremental encoders.
Both DC motors can be controlled by a PID controller. Every term of
this controller(Proportional, Integral, Derivative) is associated to a constant,
setting the weight of the corresponding term: Kp for the proportional, Ki
for the integral, Kd for the derivative.
The motor controller can be used in two control modes: the speed or
position mode. The active control mode is set according to the kind of
command received. If the controller receives a speed control command, it
switches to the speed mode. If the controller receives a position control
command, the control mode is automatically switched to the position mode.
Different control parameters (Kp, Ki and Kd) can be set for each of the two
control modes.
Khepera III manual ver 2.2
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