Failure detection and communication system for electrically driv

Details Failure detection and communication system for electrically driv Failure detection and communication system for electrically driv

1995-03-17

1998-03-10

Wysocki, Jonathan

Electricity: motive power systems

Supplied or controlled by space-transmitted electromagnetic...

361 23, 318479, H02P 300

Patent

active

057265410

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to controllers for electrically driven vehicles, particularly wheelchairs, scooters and the like. Particularly, although not exclusively, the invention relates to a modular control system in which the modules are connected by a digital serial bus.


BACKGROUND TO THE INVENTION

To the present time wheelchair controllers have typically consisted of a single unit containing all control circuitry which receives control commands from a joy stick. Should the controller fail then the whole unit must be replaced. Further, the addition of additional modules or features typically required physical modification of the controller.
European patent EP 0345785 discloses a wheelchair controller comprising a command module and a control unit linked by a serial connection. Both the command module and control module include processing units. A key PROM contains a code to enable an operator to use the chair as well as user defined parameters setting the operational characteristics of the chair. This specification does not however contemplate an expandible modular system. The serial connection is merely a means of linking the command module to the control module and does not suggest the use of a serial bus interconnecting a number of modules. The programmable features provided are merely to allow user requirements to be set, not to enable configuration for different hardware configurations.
Safety features are of concern to wheelchair manufacturers as faulty operation of a controller can result in personal injury. Prior art wheelchair controllers have offered limited safeguards. Typically all that is provided is a switch allowing the power supply or the motors to be disconnected from the controller. This may result in undesirably rapid stopping of the wheelchair or in a wheelchair malfunctioning from a fault which could have been detected. A particular concern with wheelchair controllers is that should a malfunction occur the driving and actuating modules should assume a safe state.
A problem has also existed in that the less expensive microcomputer chips only include eight bit pulse width modulators. When the output of an eight bit pulse width modulator is used to control a DC motor of a wheelchair, the resolution is noticeably coarser than for analogue control. To date it has not been possible to obtain similar performance to analogue controllers using microcomputers having eight bit pulse width modulators.
Further, the mounting of components, such as semi-conductors, in casings has been labour intensive, as has been the need to connect wires from a circuit board to a component secured to the casing. Servicing and replacement is also difficult.


DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a control means for electrically driven vehicles which overcomes at least some of the above problems or at least provides the public with a useful choice.
According to a first aspect of the invention there is provided a control means for an electrically driven vehicle comprising two or more modules interconnected by a serial bus, said serial bus including one or more data lines, wherein one or more module includes means to shift a DC bias voltage on a data line of said serial bus and one or more module includes means which monitors the DC voltage on said data line of serial bus and disables functions of the module when the detected DC bias voltage is outside a set voltage range. Preferably the serial bus has two data lines, only one of which is biased by the DC bias voltage. Preferably all safety related modules are disabled when the DC bias voltage is outside the set voltage range and all modules can vary the DC bias voltage on the serial bus.
The invention further provides a module for use in a modular control means for an electrically driven vehicle, the modules of said modular control means being interconnected by a serial bus, wherein the module includes kill means to disable functions of the module upon detecting that the DC bias level on a data line of the

REFERENCES:
patent: 3641488 (1972-02-01), Mullin
patent: 4130787 (1978-12-01), Allaire et al.
patent: 4136329 (1979-01-01), Trobert
patent: 4934477 (1990-06-01), Dai
patent: 5117218 (1992-05-01), Sasaki et al.
patent: 5163001 (1992-11-01), Luke Jr.
patent: 5384522 (1995-01-01), Toriyama et al.

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