Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-06-04
2001-07-03
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231150, C074S409000
Reexamination Certificate
active
06255645
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to measurement of backlash in systems of gears in drive trains and, more particularly, to the optical measurement of backlash in systems of gears in drive trains.
BACKGROUND OF THE INVENTION
The precise positioning of one mechanism with respect to a reference device is often accomplished by utilizing a system of gears. Power, often supplied by an electric motor, is transferred via the gears to move the mechanism. Precise positioning is dependent upon so called backlash or the looseness in the coupling between the gears. The greater the backlash, the less precise is the positioning of the mechanism with respect to the reference device. Some backlash is inevitable as it is impossible to manufacture gears that exactly mate with one another.
Backlash can be measured in gear systems by blocking movement of the driven gear and measuring the movement of the drive gear between its resulting limits of motion. This method is, however, time consuming, labor intensive, and not conducive to mass production of identical systems. Often backlash is measured in a representative number of systems and the average of these measurements is used as the backlash for all similar systems. This nominal backlash is then used as an offset in the control system. This method suffers from several disadvantages. In particular, unit-to-unit variations in backlash are not accounted for, and backlash changes over time are not accounted for.
SUMMARY OF THE INVENTION
In representative embodiments, the present invention discloses methods and apparatus for quantifying the amount of backlash present in drive trains. The techniques discussed lend themselves to self diagnosis of these systems. Optical methods are used. Such technique are useful in autochanger drive systems, but are applicable to all systems involving the driven motion of devices.
Typically during the life of driven motion devices the magnitude of the backlash increases due to the wear inherent in mechanical systems. The backlash problem is found in gear train systems, as well as other forms of driven motion devices. The invention is not limited to gear trains, but is applicable to all forms of driven motion devices. The driven system could be, but not limited to, Digital Linear Tape systems.
A movable device is positioned in front of an optical target, and the drive train is biased in one direction. The imaging system then looks at a target located on a fixed frame and measures its location. The drive train is then reversed and the angle of rotation measured as the number of counts on an encoder disk is counted by a second optical system. The target located on the fixed frame is used to determine the actual movement of the moveable device.
A primary advantage of the embodiments as described in the present patent document over prior methods lies in the fact that these methods lend themselves to self diagnosis, since measurement of the backlash in a robotic system can be performed periodically throughout the life of the drive train. If the degree of the backlash reaches a predefined limit, the robotic system can inform the user that the drive train is wearing out.
A further advantage is that these methods also lend themselves to adaptive control. The robotic system can accurately compensate for changes in backlash with time. This ability allows for accurate positioning throughout the life of the drive train.
REFERENCES:
patent: 5819588 (1998-10-01), Deane et al.
patent: 6194697 (2001-02-01), Gardner, Jr.
Gardner, Jr Richard L
Irwin Richard A
Mueller Robert L
Hewlett--Packard Company
Lee John R.
Pyo Kevin
LandOfFree
Method and apparatus for optically measuring drive train... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for optically measuring drive train..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for optically measuring drive train... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2487270