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Wireless communication provides speed and convenience for automobile
technicians. AeroComm transceivers embedded in wheel-heads take
information from the alignment sensors and communicate that data
to the server radio located in the console. The server polls each
wheel several times per second to responsively capture adjustments.
- Eliminates the long
cables running from each wheel to the console.
- Facilitates quicker,
easier wheel-head attachment; reduces clutter.
- Reduces cost of repairing/replacing
cables.
- TTL interface to wheel-heads,
with optional RS232 to PC consoles.
AeroComm transceivers are integrated into each
of four wheel heads, and another server transceiver is integrated
into the central control console to enable wireless communication
to each wheel. However, before RF could replace wires, several
capabilities had to be integrated into a small, low power, cost
effective transceiver.
A specific attribute required for wheel alignment applications
meant that the system had to be globally acceptable, including
the use of an unlicensed radio frequency, as manufacturers of
wheel alignment systems are typically large corporations with
global marketing strategies. This necessitates a transceiver with
virtual worldwide acceptance.
Also a requirement was for a low latency, wire-like communication
performance. Wheel alignment systems are comprised of a control
loop. The mechanic makes an adjustment; the sensor reads that
adjustment and sends the data to the control console. The system
must also be fast enough to enable frequent updates from four
different wheels.
In operation, the system communicates sensor data read by each
wheel head to the central console, where the information is displayed
on the screen. The central console may also provide the mechanic
with voice instructions to adjust wheel alignment.
Typically the system uses an integral antenna as transmission
ranges are short, and large external antennas are not necessary.
The server transceiver within the central console may connect
to custom base station electronics, or optionally it may connect
to a RS232 port on a 'PC based' central console.
The AeroComm receivers operate using client/server architecture
where the server radio controls the network. The server informs
the client transceivers when and where to hop to. This pseudorandom
hop table is identified by a 'channel' number. To co-locate multiple
wheel alignment systems, they are simply set to different channels.
The system then hops to different frequencies, avoiding interference
and enabling multiple independent networks. This flexibility also
enables other equipment such as brake repair and tire changers
to incorporate wireless communication without interference.
The use of AeroComm's wireless solution for wheel alignment offers
several advantages for OEMs. Frequency hopping, spread spectrum
(FHSS) techniques employed ensure excellent interference rejection,
overcome multipath problems, and allow variable power outputs.
Integral antenna versions reduce cost and eliminate external antennas
that might get damaged in a workshop environment. The transmitting
format; point to multipoint communication, is supported with AeroComm
standard configurations and it supports addressed or broadcast
packets. The OEM is able to use the address embedded in the RF-module,
alternatively their own addressing scheme.
The system architecture supports both polled or random communication,
and ACK and retry protocol are embedded for data integrity. The
fast RF rates used support frequent sensor updates. Versatility
is enhanced by the use of multiple channels that allow larger
workshops to operate more than one wheel alignment system at the
same time.
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