Freescale Semiconductor M68HC08 series, Designer Reference Manual

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LIN Stepper Software Description
Designer Reference Manual DRM047 — Rev 0
54 LIN Stepper Software Description MOTOROLA
6.1.2 Position and Speed Control
The Position and Speed Control provides stepper motor control to a
defined absolute position
positionReq with the following functions:
• linear acceleration and deceleration ramps from frequencyStart
to frequencyReq with ramp steepness
acceleration = deceleration
• handles changes after required positionReq position update
• handles changes after actual position positionAct update
• handles changes after required frequency frequencyReq update
• ads time instant PERIOD_STOP_TIMEOUT_MS after
deceleration ramp
The functionality of the Position and Speed Control Processes can be
explained using
Figure 6-2 , Figure 6-3 , and Figure 6-4 .
NOTE:
Speed (frequency) control is based on the fact that identical constant
acceleration is used for acceleration as for deceleration. Therefore, the
number of steps for speed acceleration is almost the same as for speed
deceleration.
1. Before the motor stops, the speed must be at frequencyStart , in
order not to lose the position.
In addition, according to dynamic behav ior (oscillation), the motor is
better stabilized at stop if it provides few steps with the frequencyStart
speed.
2. Therefore we apply the reserve constant
DECEL_AFTERRAMP_RESERVE.
The last issue is a numerical reserve DECEL_NUMERICAL_RESERVE.
Because acceleration and deceleration ramps are calculated from
previous commutation step reserve, the number of steps for acceleration
ramp is higher than deceleration ramps steps. In order to fulfil condition
1 , there is
3. DECEL_NUMERICAL_RESERVE
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