Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1998-05-08
2000-07-04
Martin, David
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318601, 36447422, 36447424, 3644743, G05B 1918
Patent
active
060843756
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to control of multiple drive/multiple output machines for cycle based processes.
BACKGROUND ART
A variety of increasingly sophisticated mechanisms and control systems are now being used in manufacturing, processing, and handling industries to automatically control parts-handling and forming machines. Many of these machines utilize complicated mechanisms to feed and process materials. Furthermore, there exist many different mechanisms to feed, sort, convey, manipulate, and/or form materials. In some cases, all these features are provided in a single machine capable of fast and efficient operation. Such sorting, feeding, work handling and processing mechanisms typically utilize drive control systems to articulate complex kinematic linkages in order to move working elements of the machine to desired positions. A drive control system includes an electric motor, such as an AC servomotor, and a servo drive motor controller. However, for the case of a multiple mechanism machine it becomes necessary to choreograph operation of each drive and element. Such a combination of mechanisms provides a multiple drive/multiple output machine suitable for a number of cycle based processes. Typically, a control system directs operation of the drive controls to impart desirable cooperative motions to all of the linkages. In this manner, a part can be manipulated through a series of operating steps.
One way of imparting desirable kinematic properties to a multiple drive/multiple output machine is to design each mechanism with combinations of kinematic linkages that have well-understood properties. Ratchets, cams, gears, chain and sprocket drives, linkages, toggles, and various coupling devices are typically used to create a linkage that produces a desired displacement-based movement of a part or element. For example, a Watts linkage is one device utilized to produce a substantially straight line motion of an element in a machine. Various other exemplary linkages are known for producing straight-line, or nearly straight-line motion. Additionally, other similar linkage designs are known for producing desired arcuate, circular, and rotary motions of a machine element. However, a machine having single dedicated motion cannot be easily modified in order to suit a particular desired machine application.
Another way of imparting desirable kinematic properties to a multiple drive-multiple output machine is to utilize robotic arms to form each moving mechanism. Such arms are capable of manipulating an element or part according to nearly any desired path of motion. Additionally, the robotic arms can usually be easily reprogrammed. Typically, a computerized control system directs operation of the robotic arm, enabling production of such a desired path-wise motion. Such robotic machines are choreographed according to a desired path-wise, or position-based motion of each mechanism. In this manner, clearance between elements during an operation can be ensured. Furthermore, desired positioning of a part being operated on can be ensured, in relation to a machine element doing the operating. However, robotic arms are not well suited for machines using repetitive cycle-based processes.
One problem encountered with utilizing kinematic linkages to position a working element is the inability to vary the positioning of the element or part over time and distance without redesigning the linkage. Redesign of the linkages typically takes a significant amount of machine setup time. For example, a cam on a cam follower mechanism must typically be changed in order to vary kinematic characteristics of a particular machine element using the cam follower mechanism. The only possible variation available is to speed up or slow down operation of the cam, which complicates control of the device. However, movement is still directly related to the shape of the cam, which remains the same. Therefore, there is a need to better control kinematics of machine elements in a way that allows for relative changes in velocity of the
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Curry Gary A.
Fisk Marian J.
Irwin Jere F.
Roberts David L.
Roberts Stephanie L.
Martin David
The Vision Limited Partnership
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