Data processing: generic control systems or specific application – Specific application – apparatus or process – Article handling
Reexamination Certificate
1999-01-28
2001-05-22
Ellis, Christopher P. (Department: 3651)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Article handling
C700S217000, C700S228000, C706S904000, C706S905000, C706S910000, C706S012000, C706S008000
Reexamination Certificate
active
06236905
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of vehicular wheelchair lifts which enable persons who are physically challenged or otherwise have limited mobility to board and leave a vehicle. More particularly, the present invention relates to the field of providing correction to the positioning movement of a platform of the wheelchair lift.
2. Description of the Prior Art
Vehicle lifts are widely used for enabling persons who are physically challenged or otherwise have limited mobility to board and leave vehicles. In using the wheelchair lift, it is important that the platform of the lift is accurately positioned.
One of the common arrangements of a vehicular wheelchair lift is shown in FIG.
1
. Referring to
FIG. 1
, there is illustrated a vehicle
2
, such as a bus, with a powered vehicular wheelchair lift
10
mounted underneath one of the access doors of the bus
2
. The platform
12
of the lift
10
is illustrated in one of its various operating positions, which typically include a ground level position “G”, a stow level position “S”, and a floor level position “F” (the floor and ground level positions are designated in dashed lines as shown).
In control the movement of the platform
12
, it is critical that the platform
12
can be positioned accurately at a “target” level. For example, if the platform needs to be at the stow level “S”, then the target level is the stow level “S” and as the platform
12
moves toward the stow level “S” either from the ground level “G” below or from the floor level “F” above, the control mechanisms of the lift
10
should stop the platform
12
at the stow level “S”. The movement of the platform
12
toward the stow level “S” is a positioning movement of the platform
12
, which should end when the platform
12
arrives at the stow level “S”.
However, since the positioning movement of the platform
12
is powered by the hydraulic, electric or other types of power mechanisms of the lift
10
and controlled by the positioning mechanisms of the lift
10
, in real practice there is often an error between the target level and the actual level of the platform
12
. This error will vary in a predicable manner by environment changes and mechanical wear. In the example shown in
FIG. 1
, the target level is the stow level “S”, which is the level the platform
12
shoots for, but the platform does not come to a full stop at level “S”. Rather, the actual position of the platform
12
is at level “P”. The distance “&Dgr;” between the target level “S” and the actual level “P” is the error of the positioning movement of platform
12
. If the error is corrected in the same cycle in which it occurs, the cycle will be necessary increases. This is an undesirable side effect of a non-learning error correction system.
It is desirable to have a method of and apparatus for providing correction to the error in the positioning movement of the platform of a wheelchair lift. It is also desirable to have such a system respond to the variance of the error, due to the environment and/or mechanical changes. It is also desirable to provide for error correction while keeping cycle time at a minimum.
SUMMARY OF THE INVENTION
The present invention is a method of and apparatus for providing self-learning correction to the platform positioning movement in a vehicular wheelchair lift.
The present invention is used in conjunction with a positioning device and control mechanism of a wheelchair lift. The positioning device operates to determine the position of the platform, and the control mechanism operates to control the positioning movement of the platform.
Described generally, the present invention is a method of providing error correction to the positioning movement of a platform in a vehicular wheelchair lift. The present invention method includes the steps of programming the platform to stop at a target position, calculating an error between the programmed target position and an actual stop position of the platform, and deriving a new target position to stop the platform based on the calculated error to compensate the overshoot or shortcoming of the actual stop position of the platform.
In the present invention method, the value of the error is recalculated each time based on the difference between the new target position and the next actual stop position of the platform. The error value is stored and used for the next similar positioning movement of the platform.
The present invention is also an apparatus for providing error correction to the movement of a platform in a vehicular wheelchair lift. The present invention apparatus includes a programmable control mechanism capable of controlling the platform positioning movement and directing the platform to stop at a programmed target position. The programmable control mechanism may be a microprocessor. It can calculate the error between the programmed target position and the actual stop position of the platform, and derive a new target position to stop the platform based on the calculated error to compensate the overshoot or shortcoming of the actual stop position of the platform. The present invention apparatus may also include a memory device for storing the final error value which is used for the next similar positioning movement of the platform.
The application of the present invention method is not limited to vehicular wheelchair lift. In fact, it can be utilized to provide self-learning error correction to the positioning movement of any moving member in machinery or an equipment. Further novel features and other objects of the present invention will become apparent from the following detailed description, discussion and the appended claims, taken in conjunction with the drawings.
REFERENCES:
patent: 4813125 (1989-03-01), Dace, Jr.
patent: 5632593 (1997-05-01), Aoki
patent: 5672041 (1997-09-01), Ringhdahl et al.
patent: 5899655 (1999-05-01), Miller et al.
patent: 6043741 (2000-03-01), Whitmarsh
patent: 6064165 (2000-05-01), Boisvert et al.
patent: 6078849 (2000-06-01), Brady et al.
patent: 6086314 (2000-07-01), Savaria
Butler Michael E.
Chen Tony D.
Ellis Christopher P.
Fong Jerry
Ricon Corporation
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