Page 286 - Understanding Automotive Electronics

2735 | CH 8 Page 273 Tuesday, March 10, 1998 1:19 PM

VEHICLE MOTION CONTROL 8

Stepper Motor-Based Actuator

For example, in the case of a stepper motor actuator, the actuator driver
electronics reads this number and then generates a sequence of pulses to the
pair of windings on the stepper motor (with the correct relative phasing) to
cause the stepper motor to either advance or retard the throttle setting as
required to bring the error toward zero.
An illustrative example of driver circuitry for a stepper motor actuator is
shown in Figure 8.9.The basic idea for this circuitry is to continuously drive
the stepper motor to advance or retard the throttle in accordance with the
control signal that is stored in memory. Just as the controller periodically
updates the actuator control signal, the stepper motor driver electronics
continually adjusts the throttle by an amount determined by the actuator
signal.

Figure 8.9
Stepper Motor Actuator for Cruise Control

UNDERSTANDING AUTOMOTIVE ELECTRONICS 273