Freescale Semiconductor M68HC08 series, Руководство по проектированию

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DRM047 — Rev 0 Designer Reference Manual
MOTOROLA Conclusion 87
Designer Reference Manual — DRM047
Section 8. Conclusion
One of the aims of this reference design was to show that the LIN-bus is
suitable for HID headlamp levelling control and its communication speed
is fully sufficient for this application.
The dynamic behavior of the HID lamp levelling system has some
limitations due to mechanical parts. The bus communication system
(LIN-bus) should not be the limitation for the system dynamic.
This is demonstrated below using the PC master recorder (see
Section 7.5. Recorder ). The figures below are measured using the PC
master software. Control Loop1 controls automatically the levelling of a
standard HID lamp according to signals pre-programmed in LIN Master.
The horizontal levelling is set for Axis1.
All Axis1 frames are being sent. Control Loop2 is also enabled and
controls Axis2. All Axis2 frames are being sent (see
Section 7.4. Slave
Control ). All frames are sent with constant period periodeSend = 30ms.
According with the stepper motor and mechanical parts of the HID lamp,
the following setting is provided:
• start speed = 200rpm
• max. speed frequencyReq = 700rpm
• and position range positionReq +/-128steps
Figure 8-1 shows that a slow sinusoidal signal of required position
positionReq can be followed by the actualPosition signal. If the signal
frequency increases, the HID lamp mechanics are not able to copy the
required position. The LIN-bus is able to provide enough samples.
The system mechanics are the limiting factor.
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