GB2348349A

GB2348349A - A control system

Info

Publication number: GB2348349A
Application number: GB9906397A
Authority: GB
Inventors: Kevin Trevor Talbot
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1999-03-20
Filing date: 1999-03-20
Publication date: 2000-09-27
Also published as: GB9906397D0

Abstract

A control system for a vehicle is disclosed which includes local multiplex control of electrical services provided in a door 10 of the vehicle. A switch pack 18 acts as a master node for controlling a series of slave nodes 22, 24, 26 comprising a window lift motor unit 22, a mirror motor unit 24 and a door latch mechanism 26. The nodes 18, 22, 24, 26 are supplied by a common power line 12 and are provided with a common ground-line 14, the power line 12 including a series inductor 32, 40 on the input side of each node 18, 22, 24, 26 so as to isolate the node from interference on the power line 12 and to prevent interference generated in or by the nodes from getting onto the power line 12. The master node communicates with the slave nodes by generating a carrier frequency on the power line and amplitude modulating that carrier wave.

Description

A Control Svstem This invention relates to control systems and in particular to a control system for a vehicle.

The proliferation in electrical systems on vehicles in recent years has resulted vehicle manufacturers being faced with increased packaging problems in trying to fit in all the wires required. Some manufacturers have resorted to the use of multiplexed systems which can reduce the wiring by sharing one or more of a common power bus, a ground and a controller area network (CAN) bus between a family of nodes.

It is an object of this invention to provide an improved control system.

According to the invention there is provided a control system comprising an area network having at least one local master node arranged in use to receive signals via an information bus, the master node being supplied with a power line, wherein the master node further comprises a transceiver which is arranged in use to generate a carrier wave on the power line and to communicate with at least one slave node by modulation of said carrier wave. Said modulation may comprise amplitude modulation.

The power line may include an inductor in series with a power input of the master node, the inductor being arranged in use to provide local isolation of the master node from interference on the power line.

The or each slave node may be arranged to draw its power supply from the power line of the master node, wherein the or each slave node includes an inductor in series with its power input, so as to substantially prevent noise generated within or by the or each slave node from feeding back on to said power line.

The or each slave node may be connected to the power line in parallel with the master node and on the locally isolated side of the master node power line.

A said slave node may be arranged to be capable of modulating said carrier wave so as to be capable of sending a signal to the master node.

The master node may be provided with a ground connection which includes a series inductor, such that signals placed by the master node onto the power line comprise balanced signals.

The or each slave node may be isolated from ground. In this case communication with the master node may appear to be unbalanced but, because the signals placed on the power bus by the master node are substantially balanced, the communication with the master node is substantially balanced.

The frequency of said carrier wave may be in the order of 40 MHz.

The control system may comprise the control system of a vehicle and may comprise the control system of a closure member of the vehicle. The master node may comprise a switch pack of said closure member and the slave nodes may comprise at least one of a window lift means, a door mirror control means and a door latch means.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a door of a vehicle including a control system according to the invention; Figure 2 is a circuit diagram of part of the control system of Figure 1; and Figure 3 is a schematic diagram of part of the control system of Figure 1 in accordance with a modification to the invention.

Referring to Figures 1 and 2, a vehicle (not shown further) includes a closure member in the form of a door 10. The door 10 is supplied with a vehicle power line 12 and a vehicle ground 14. Instructions to electrical services in the door 10 are provided from a vehicle body control module (not shown) along a controller area network (CAN) bus 16.

The power line 12, ground-line 14 and CAN bus 16 all feed into a switch pack 18 forming part of the door assembly 10. The switch pack 18 includes a set of switches 20 for local control of a window lift motor unit 22, while control signals for a mirror motor unit 24 and a central locking door latch 26 are supplied from remote controls (not shown) by instructions passed along the CAN bus 16.

The switch pack 18 acts as a master node for the electrical services incorporated in the door 10 and includes a logic circuit 28 for performing local control of slave units which perform those services. The slave units comprise the window lift motor unit 22, the mirror motor unit 24 and the door latch 26.

The logic unit 28 interfaces instructions from the CAN bus 16 and the switches 20 to the slave nodes 22,24,26 by sending signals from a transceiver 30 included within the master node switch pack 18. The master node transceiver 30 generates a carrier frequency in the region of 40 MHz and the instructions from the master node 18 to the slave nodes 22,24,26 are communicated using amplitude modulation (AM) of the carrier frequency.

The vehicle power line 12 includes a series inductor 32 on the input side of the switch pack 18, after which the vehicle power line 12 becomes a door power bus 34 from which the rest of the nodes 22,24,26 also draw their power. The vehicle ground 14 also passes through the switch pack 18 and then becomes a door ground 36, through which the rest of the nodes 22,24,26 are also provided with a ground connection.

The slave nodes 22,24,26 are all similar in construction and each includes a transceiver 38 for de-modulating signals from the switch pack transceiver 30 passed to them 38 along the door power bus 34.

The slave nodes 22, 24,26 are further arranged to be capable of sending signals, such as status or fault signals, to the master node by amplitude modulating the carrier frequency themselves. For example, the switch pack 18 may tell the slave nodes 22,24,26 when to transmit by initiating a cycle of transmission by each slave node 22,24,26 in sequence (e. g. every 50 milliseconds the switch pack 18 transmits, on completion the window unit 22 replies followed by the mirror unit 24 and then the door latch 26).

Each slave node 22,24,26 includes an inductor 40 in series with its power line 42 drawn from the door power bus 34. The inductor 40 on the power input to individual slave nodes 22, 24,26 substantially prevents noise generated within or by the nodes 22,24,26 from being fed back onto the door power bus 34 and therefrom back into the master node switch pack 18, or another slave node.

By providing the power inductor 32 on the vehicle power line 12, the susceptibility of the door 10 to noise present on the power line 12 is reduced. The likelihood of noise generated in the door 10 from being fed back onto the power line 12 is reduced by the provision of the inductors 40 on the door power bus inputs 34 to each of the door nodes 22,24,26. The inductors 32,40 are arranged to provide a high impedance to RF signals and noise on the power lines 12, 34.

Referring now to Figure 3, in a modification to the invention the switch pack ground 360 is isolated from the vehicle ground 14 by an inductor 320, such that the signal from the RF oscillator/driver 300 (forming part of the transceiver 30) is applied as a balanced signal. The slave nodes 22,24,26 remain isolated from the ground metalwork 140 of the door 10.

In this manner, communication with the master node 18 may appear to be unbalanced but, because the signals placed on the power bus 340 by the master node 18 are substantially balanced, communication between the slave nodes 22, 24,26 and the master node 18 is substantially balanced. This modification reduces the tendency of the system to emit RF noise.

Claims

CLAIMS 1. A control system comprising an area network having at least one local master node arranged in use to receive signals via an information bus, the master node being supplied with a power line, wherein the master node further comprises a transceiver which is arranged in use to generate a carrier wave on the power line and to communicate with at least one slave node by modulation of said carrier wave.
2. A control system according to Claim 1, said modulation comprising amplitude modulation.
3. A control system according to Claim 1 or Claim 2, wherein the power line includes an inductor in series with a power input of the master node, the inductor being arranged in use to provide local isolation of the master node from interference on the power line.
4. A control system according to any preceding claim, the or each slave node being arranged to draw its power supply from the power line of the master node, wherein the or each slave node includes an inductor in series with its power input, so as to substantially prevent noise generated within or by the or each slave node from feeding back on to said power line.
5. A control system according to any preceding claim, wherein the or each slave node is connected to the power line in parallel with the master node and on the locally isolated side of the master node power line.
6. A control system according to any preceding claim, wherein a said slave node is arranged to be capable of modulating said carrier wave so as to be capable of sending a signal to the master node.
7. A control system according to any preceding claim, wherein the master node is provided with a ground connection which includes a series inductor, such that signals placed by the master node onto the power line comprise balanced signals.
8. A control system according to Claim 7, wherein the or each slave node is isolated from ground.
9. A control system according to any preceding claim, wherein the frequency of said carrier wave is in the order of 40 MHz.
10. A control system substantially as described herein with reference to the accompanying drawings.
11. A control system according to any preceding claim comprising a control system of a vehicle.
12. A control system according to Claim 11 comprising a control system of a closure member of the vehicle.
13. A control system according to Claim 12, the master node comprising a switch pack of said closure member.
14. A control system according to Claim 12 or Claim 13, the slave nodes comprising at least one of a window lift means, a door mirror control means and a door latch means.