Biomedical Engineering Reference
In-Depth Information
Desired trajectory
Real trajectory
Planning &
trajectory
formation
Control
element
Actuators
Load
Force
feedback
Control feedback
Positional
feedback
Figure 17.5
Typical block diagram of feedback control. Sensory feedback has a direct control
action.
Figure 17.6
Bode diagram of a feedback controlled spring-mass model. The phase margin is
computed by considering the frequency at which the log-magnitude plot intersects
the 0 dB line and measuring the difference between the critical phase value (180
◦
)
and the actual phase, derived from the phase plot. Stability requires a positive phase
margin and a value greater that 45
◦
is required for suitable damping.
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