Actuator with translational and rotational control

An actuator for precisely moving and positioning a manufacturing component includes a housing on which a magnet is mounted. An electrical coil is wound around a coil piston which is slidingly mounted on the housing for movement within the magnetic field generated by the magnet. A rod, having a member for gripping the component, is attached for translational movement with the coil piston, and a source of electrical current is connected to the coil which is wrapped around the coil piston. A drive motor is mounted on the device, and a linkage connects the drive motor to the grip for rotation of the grip as desired. In the operation of the actuator, a current is selectively passed through the coil. This current in the coil then moves the coil piston and the attached grip within the magnetic field to position the component as desired in translation. Also, the drive motor can be activated to move the grip in rotation as desired. Additionally, position sensors can be mounted on the device to determine the location of the coil piston and a controller can be incorporated in the actuator to use this position determination for controlling movement of the coil piston and the attached grip in translation and rotation.

FIELD OF THE INVENTION 
The present invention pertains generally to machines which are useful for 
the automated assembly of products. More specifically, the present 
invention pertains to apparatus and devices which are useful for 
inspecting, assembling and positioning component parts in a product 
assembly process. The present invention is particularly, but not 
exclusively, useful as an actuator for the quick movement and precise 
positioning of relatively fragile component parts, in an appropriate 
translational and rotational alignment, during an automated assembly 
procedure while generating both extremely light forces and normal forces 
on the component parts. 
BACKGROUND OF THE INVENTION 
Numerous devices which are useful for the automated assembly of products 
have been successfully used for many years. In each instance, automated 
assembly devices have been employed with a view toward increasing the 
efficiencies and accuracies of the methods, procedures and processes which 
are followed during the manufacture and the assembly of a completed 
product. Indeed, the vast majority of consumer products are now 
manufactured on assembly lines which incorporate automated assembly 
devices. 
It is easy to appreciate that as the complexity of a manufactured product 
increases, there may also be a commensurate increase in the complexity of 
the machines that are required to manufacture the product. This is 
particularly so where the component parts are delicate or fragile and 
precision is important. For example, many products require the precise 
positioning and assembly of extremely small and light weight components in 
their manufacture. More specifically, these operations require precision 
in both the movement of the component into position and in the force with 
which the component is moved and assembled with other components. 
Furthermore, for quality control purposes it is often necessary that there 
be some way to obtain a real time check on the precision with which the 
component was positioned during the assembly of the product. Where very 
small, fragile or light weight components are being used in the 
manufacturing process, and where either very light forces or normal forces 
are required for the assembly of these components these considerations 
become very important. 
Of the known devices which are typically used for automated assembly, 
pneumatic devices are notoriously imprecise. This is so due primarily to 
the poor damping achieved by pneumatic systems. On the other hand, systems 
incorporating solenoids can be quite precise. However, the forces which 
solenoids impose on components during their handling of the component can 
be destructive to the component or be otherwise unacceptable. One other 
general type device, the well-known stepper motor, also deserves some 
mention. Generally, stepper-motor systems can be spatially precise in 
their operation, and the forces which they generate can be effectively 
controlled. Steppermotors, however, are bulky items and do not have good 
light force generation characteristics. In some manufacturing procedures 
these factors can be of significant disadvantage. Consequently, the 
present invention has recognized that an electronically operated system 
can be effective for the precise placement of a product component during 
assembly without encountering the force and spatial problems confronted by 
the above discussed types of systems. More specifically, the present 
invention recognizes that a voice coil linear motor can be applied for 
these purposes. 
While U.S. Pat. No. 4,498,023 which issued to Stout for an invention 
entitled "Voice Coil Linear Motor with Integral Capacitor" addresses some 
of the issues which are of concern to the present invention, it does not 
address all of the important issues. For example, the present invention is 
concerned with maintaining precise concentricity between the parts of the 
actuator device as they move relative to each other. Stout does not 
precisely address this problem. Further, the present invention envisions a 
compact configuration for the actuator which may not be attainable with 
the cylindrical coil disclosed for the Stout device. Additionally, due to 
the suggested magnet strengths, a device such as the one disclosed in U.S. 
Pat. No. 4,498,023 can expect to have heat generation problems which 
drastically effect the proposed sensors accuracy thereby rendering the 
device ineffective. 
The present invention also recognizes there are instances when it is 
important that a work product be both properly moved in a translational 
motion, and properly oriented rotationally. Further, there are instances 
when it is necessary for the work product to be rotated to join the work 
product to another component such as when it is necessary to thread or 
screw one component into another. In the event it may be necessary, in 
order for the system to precisely position the work piece, that the work 
piece be moved both in translation and in rotation. 
In addition to the advantages alluded to above, an electronic system has 
other characteristics which can be advantageous for a device which is to 
be used in the automated assembly of an end product. For example, some 
electronic system can rather easily lend itself to compact configurations. 
Further, an electronic system is responsive and can be configured to 
provide signals which can be used to monitor and control the operation of 
the system. 
In light of the above, it is an object of the present invention to provide 
a device for moving, inspecting and positioning a component in an 
automated assembly operation which is capable of picking-up, transporting 
and depositing fragile and light weight components. It is another object 
of the present invention to provide a device for moving and positioning a 
component in an automated assembly operation which has effective control 
of either extremely small forces or normal forces, and which can control 
such forces within a relatively fast response time. Yet another object of 
the present invention is to provide a device which can transport assembly 
components with minimal bounce (i.e. little, if any, changes in linear 
direction) at the end of a component placement operation. Still another 
object of the present invention is to provide a device for moving, 
inspecting and positioning a component in an automated assembly operation 
which can be effectively monitored for real time verification of 
operational accuracy. Yet another object of the present invention is to 
provide a device for moving and positioning a component in an automated 
assembly operation wherein there is effective control over both the 
translational and rotational positioning of the work piece being 
transported. Another object of the present invention is to provide an 
automated assembly device which is relatively simple to use, is relatively 
easy to manufacture and is comparatively cost effective. 
SUMMARY OF THE INVENTION 
An actuator for transporting and positioning a workpiece in an automated 
assembly procedure includes a housing, with a magnet fixedly mounted on 
the housing to establish a magnetic field within the housing. The magnet 
is preferably a rare earth magnet and is formed with a projection that 
extends through the central chamber of the housing. A coil piston, formed 
with an open passageway, is slidingly mounted on the housing and is 
positioned to surround the magnet with the projection of the magnet 
extending through the passageway. For an alternate embodiment of the 
present invention, a plurality of magnets can be mounted on the housing 
and the coil piston can be slidingly mounted on the housing for 
reciprocation in the magnetic field between the magnets. In either case, a 
conductive wire is wrapped around the coil piston to create a coil 
assembly. 
In accordance with the present invention, the actuator also includes a grip 
which is mounted on the coil piston to hold the workpiece or product 
component during its transfer from a supply source into position for 
product assembly. Preferably, the grip is a hollow rod which is mounted on 
the coil piston for linear movement with the coil piston and for rotation 
on the coil piston about the longitudinal axis of the rod. For one 
embodiment of the actuator the grip can have an end piece which is 
operable to grasp the workpiece or component to be moved. In an alternate 
embodiment for the actuator, a vacuum source can be operatively connected 
with the rod to create a suction through the hollow rod that holds the 
workpiece or product component against the rod during transport. 
For the operation of the actuator of the present invention, a source of 
electrical current is provided and is connected directly to the coil of 
the coil assembly. Electrical currents from this source are passed through 
the coil as desired by the operator. Because the coil is disposed in the 
magnetic field that is generated by the magnet, current flow through the 
coil creates a force on the coil piston. This force then moves the coil 
piston and the grip relative to the housing. Additionally, the actuator 
itself can be moved in any manner well known in the art, and the concerted 
action of actuator movement and the movement of the grip relative to the 
rest of the actuator can be used to transport a workpiece or a product 
component from one location to another. 
A position sensor can be mounted on the housing of the actuator to detect 
the location of the coil piston, and hence the translation position of the 
grip, relative to the housing. As intended for the present invention, the 
sensor can be either a relatively uncomplicated capacitive type sensor or, 
preferably, a more sophisticated optical encoder. In any case, the 
translational position sensor can be used to calibrate movement of the 
grip and to establish its start and stop points. Further, signals 
generated by the translational position sensor can be used to control the 
operation and translational movement of the coil piston and to inspect the 
result of the actuator's operation. To do so, the actuator can be modified 
to include a microprocessor which compares the actual position of the coil 
piston (as indicated by the position sensor) with a preset desired 
position of the coil piston (in accordance with programmed input). This 
comparison will generate an error signal. Depending on the magnitude of 
this error signal, control of the coil piston can be accomplished by 
moving the coil piston in a manner which will reduce the error signal to 
zero. This, of course, is done if control is the objective. On the other 
hand, if inspection and quality control are the objectives, the error 
signal can be maintained and the assembled product rejected if the error 
signal exceeds the established tolerance. 
In accordance with the preferred embodiment of the present invention, the 
actuator provides for both translational and rotational control over both 
the movement and positioning of the product component. The intent here is 
not only to properly align the product component, but to also provide for 
the capability of screwing or threading the product component into another 
component of the product begin assembled. In order to provide a rotational 
capability for the grip, one embodiment of the present invention includes 
an electric drive motor which is mounted on the coil piston for 
translational movement with the coil piston. The drive shaft of the drive 
motor is connected to the grip of the actuator by a linkage which will 
cause rotation of the grip upon activation of the drive motor. For an 
alternate embodiment of the present invention, the electric drive motor is 
mounted on the housing. With this alternate embodiment, as with the other 
embodiment of the present invention, the drive motor is also connected to 
the grip of the actuator by a linkage which will cause rotation of the 
grip upon activation of the drive motor. 
An encoder is also provided which is positioned to detect the angular 
displacement of the grip relative to a predetermined reference. More 
specifically, an encoder wheel is attached to the grip rod and an optical 
encoder is mounted on the coil piston. The microprocessor is 
electronically connected to the optical encoder and uses signals generated 
by the optical encoder to ascertain the angular position of the grip rod. 
In accordance with signals from the microprocessor, the drive motor is 
actuated to rotate the grip rod. Thus, signals from the microprocessor can 
be used to rotationally orient the product component. Further, in 
accordance with predetermined instructions concerning number or rotations 
or allowable torque limits, signals from the microprocessor can be used to 
rotate the product component to thread or screw the work component into 
another component. 
The novel features of this invention, as well as the invention itself, both 
as to its structure and its operation will be best understood from the 
accompanying drawings, taken in conjunction with the accompanying 
description, in which similar reference characters refer to similar parts, 
and in which:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring initially to FIG. 1, the actuator device of the present 
invention, for moving and positioning an assembly component in an 
automated assembly operation, is shown in its intended environment and is 
designated 11. As shown, the device 11 is operatively mounted on an 
automated assembly machine 12 for movement between a position wherein the 
device (designated 11) retrieves a component 14 from a conveyor 16 and 
transports the component 14 to a position wherein the device (designated 
11') places the component 14 into engagement with another end product 
component 18. After their assembly, the combination of components 14 and 
18 is then taken by a conveyor 20 to a subsequent workstation where it is 
packaged or further combined with other components (not shown). As far as 
the device 11 and its operation is concerned, it is to be appreciated that 
the machine 12 shown in FIG. 1 is only exemplary. Indeed, the device 11 
can be mounted on a variety of machines (not shown) for movement between a 
plurality of preselected positions. 
In FIG. 2 it is seen that the actuator device 11 includes a housing 22 
which is relatively compact, and is configured and dimensioned to be 
comparatively flat. Importantly, though not shown in the Figures, this 
configuration allows the actuator device 11 to be easily stacked with 
other such devices for improved efficiency in an automated assembly 
operation. FIG. 2 also shows that a grip (or rod) 24 is mounted on the 
housing 22. Specifically, for the present invention, the rod 24 is 
preferably an elongated tubular member which is slidingly mounted on the 
housing 22 and which extends through the housing 22 substantially as 
shown. It will also be seen in FIG. 2 that the housing 22 is provided with 
an attachment 26, and with an electrical connector 28 and a sensor 
connector 30. Insofar as the rod 24 is specifically concerned, the rod 24 
is slidingly mounted on the housing 22 between the attachment 26 and a 
bearing 27 (see FIG. 4) which is located on the housing 22 opposite from 
the attachment 26. Further, as so mounted, the rod 24 can be rotated about 
its longitudinal axis if desired. 
Referring to FIG. 3, the preferred embodiment of the actuator for the 
present invention is shown and generally designated 100. This embodiment 
of actuator 100 includes an electrical coil 102 which is shown here to be 
in a substantially flattened configuration. The actual shape of coil 102, 
however, is of minimal importance and will in large part be determined by 
the desires of the manufacturer. In fact, coil 102 could have been shown 
to be cylindrically configured. In any case, the windings of coil 102 must 
somehow be configured to surround a hollow space. 
FIG. 3 shows the coil 102 wrapped around an extension 104 of a coil piston 
106. Although this embodiment of actuator 100 shows a particular structure 
around which the coil 102 is wrapped, the skilled artisan will appreciate 
that coils are commercially available which do not require such structure. 
Such coils may, of course, be used with the present invention. Regardless, 
it is important that the coil 102 be physically attached to the coil 
piston 106 and able to move with the coil piston 106. Further, it is 
important for the present invention that the grip 24 be operatively 
attached to the coil piston 106 and able to move with the coil piston 106. 
A magnet 108 is shown attached to the housing 22 of actuator 100 and a 
magnet return 110 is also shown attached to the housing 22 and distanced 
from the magnet 108 so that an effective flux field is established as the 
environment for the coil 102. Preferably, magnet 108 is a rare earth 
magnet having a permanent magnetic capability of 35 MEG oersted. As 
intended for the present invention, the coil 102 may either surround the 
magnet 108 or, as discussed below for an alternate embodiment of the 
invention, the coil 102 may be positioned for movement between a plurality 
of magnets. This establishes a cooperation between the coil 102, the 
magnet 108 and the magnet return 110 in which a portion of the coil 102 is 
able to move between the magnet 108 and the magnet return 110. 
The coil piston 106 is fixedly attached to a linear bearing 112 and the 
linear bearing 112 is slidingly mounted on a bearing rail 114. The bearing 
rail 114, in turn, is fixedly mounted to the housing 22. This arrangement 
allows the linear bearing 112 with its attached coil piston 106 and coil 
102 to slidingly move within the housing 22. Consequently, because the 
windings of coil 102 are oriented substantially perpendicular to the flux 
field generated by the magnet 108, the application of an electrical 
current to the coil 102 will generate a force on the coil piston which 
causes the coil assembly (i.e. coil 102 and coil piston 106) to move 
within housing 22. This movement needs to be monitored and controlled. 
Additionally, as indicated above, for the embodiment of an actuator 11 
having the capability of moving grip/rod 24 in both translation and 
rotation, there needs to be some means for independently controlling these 
movements. The translational movement and control of grip/rod 24 is 
discussed first, the rotational movement and control of grip/rod 24 is 
discussed subsequently. 
Control over the movement of coil 102, and thus control over the grip 24, 
is achieved by monitoring the position of coil piston 106 relative to the 
housing 22. This is done using an encoder 122, such as a model SRL 4 
encoder manufactured by Dynamics Research Corporation which is fixedly 
attached to the housing 22. More specifically, for actuator 100, a bracket 
116 is fixedly attached to linear bearing 112 and a glass encoder slide 
118, with a scale 120 etched or printed thereon, is fixedly attached to 
the bracket 116. Accordingly, glass encoder slide 116 moves together with 
both linear bearing 112 and coil piston 106. In a manner to be 
subsequently discussed in greater detail, the actuator 100 uses 
information from the encoder 122 regarding the position of glass slide 118 
to precisely fix the position of coil piston 106, and thus the position of 
grip 24, relative to housing 22. Using this arrangement, accuracies on the 
order of five hundredths of a millimeter (0.05 mm) have been attained for 
determining the actual position of rod 24. Additionally, rod 24 can have a 
magnet (not shown) which is mounted on the rod 24 for movement therewith. 
Another magnet 124, shown fixedly mounted on the housing 22 is 
electrically activated to magnetically engage with the magnet on rod 24 to 
hold the rod 24 and its associated coil assembly in a detent or withdrawn 
configuration during the idle time for the actuator 100. The position of 
either the magnet on rod 24 or the magnet 124 can be adjusted to allow 
proper engagement of the rod 24 with the housing 22 in the detent position 
for rod 24. 
The details for an alternate embodiment of the actuator device 11 will be 
appreciated with reference to FIG. 4 wherein it is seen that the device 11 
includes a bobbin 32 (similar to coil piston 106 for the preferred 
embodiment) which is formed with a hollow 34. Indeed, in most respects the 
alternate embodiment is similar to the preferred embodiment and the 
purposes are the same. As shown, the bobbin 32 is relatively flat, like 
housing 22, and is generally box shaped. Further, the bobbin 32 is 
slidingly attached to a slide mechanism 36 which is itself fixedly 
attached to the housing 22. Preferably, this mechanism 36 is a very light 
precision way which creates minimal friction forces during movement of the 
bobbin 32. The mechanism 36 can be established in any of several ways, all 
known in the pertinent art, and can be provided with travel stops which 
will limit the distance through which bobbin 32 can travel along the 
mechanism 36. Preferably, the extent of this travel is in the range of 
between two and four inches (2-4 inches). Consequently, the bobbin 32 is 
able to slide freely along the mechanism 36 and to reciprocate within the 
housing 22 through this distance. It is also important to recognize that 
the grip 24 is attached to the bobbin 32 for linear movement with the 
bobbin 32. 
FIG. 4 also shows that a magnet 38 is mounted inside the housing 22. 
Specifically, the magnet 38 is formed with a projection 40 and is 
positioned inside the housing 22 so that the projection 40 of magnet 38 
extends into the hollow 34 of the bobbin 32. Preferably, the magnet 38 is 
of a commercially available type which is made of a rare earth element. 
For example, a Neodenium 35 megagaussoersted magnet is suitable for use in 
the present invention. Further, it is preferable that the magnet 38 be a 
permanent magnet which is capable of operating with a magnetic intensity 
on the order of approximately thirty-five MEG oersted (35 MOe). When the 
magnet 38 is positioned in housing 22 as shown in FIG. 4, it will be 
appreciated by the skilled artisan that the poles of magnet 38 can be 
oriented on the housing 22 to effectively establish a magnetic field 
having flux lines that are aligned substantially perpendicular to the 
directions along which the bobbin 32 reciprocates in the housing 22. 
The device 11 also includes a coil 42 which is made from an electrical wire 
44 that is wound around the bobbin 32. Importantly, the winding of coil 42 
around the bobbin 32 should be sufficiently tight to effectively join coil 
42 to the bobbin 32. The ends 44a and 44b of the electrical wire 44 are 
electrically attached to the connector 28 so that an external voltage 
source 46 (shown in FIG. 7) can be used to energize the coil 42. As will 
be appreciated by those skilled in the pertinent art, with the coil 42 
located in the magnetic field that is generated by the magnet 38, when a 
current from voltage source 46 is passed through the coil 42 a force is 
imposed on the bobbin 32 that will move the bobbin 32 within the housing 
22. Depending on the amount, the direction, and the duration of the 
current which is passed through coil 42, the force which is generated on 
the bobbin 32 can be controlled. Preferably, the magnitude of the forces 
generated on the bobbin 32 will be in a range from zero to ten thousand 
grams (0-10000 grams). As intended for the present invention the actuator 
11 (FIGS. 2 and 4) as well as the actuator 100 (FIG. 3) will likely 
operate in a range where approximately zero to two thousand grams (0-2,000 
gm) variable of force are selectively applied with a deviation of only 
plus or minus one gram (.+-.1 gm). Further, as is well known in the 
pertinent art and as indicated above, the position and direction of travel 
of the bobbin 32 can be controlled by the magnitude and direction of flow 
of current through the coil 42. 
For the operation of the device 11, it is important to be able to determine 
the positional relationship between the bobbin 32 and the housing 22. To 
do this, several position sensors can be suggested. Referring for the 
moment to FIG. 7, it will be seen that a sensor 48 is incorporated into 
the device and is operatively connected through a line 50 to the sensor 
connector 30 located on housing 22 of device 11. Further, line 50 
completes the connection between sensor connector 30 and microprocessor 
70. In one embodiment the position sensing function can be accomplished 
using a capacitance inductance (LVDT) sensor like the one shown in FIG. 5. 
There it will be seen that the device 11 can include a middle plate 52 
which is fixedly mounted to the bobbin 32 for movement with the bobbin 32 
in the housing 22. This middle plate 52 is then disposed between a plate 
54 and a plate 56 which are each fixedly connected to the housing 22 of 
device 11. Further, the plates 54 and 56 are respectively connected to 
lines 58 and 60 which, together, constitute the line 50 in this 
embodiment. Consequently, as middle plate 52 moves with the bobbin 32, the 
electrical capacitance between the plate 54 and 56 will be changed. This 
change in capacitance can be determined by the sensor 48 by means well 
known in the art to ascertain the position of the bobbin 32 relative to 
the housing 22. The flat plates remove concentricity problems and, as they 
are located away from the coil [a heat source], the sensor will be 
accurate. 
In an alternate embodiment of the sensor 48, the capacitive elements 
comprising the plates 52, 54 and 56 are removed and, instead, a 
photo-electric system much like the encoder 122 previously discussed in 
conjunction with the actuator 100 is incorporated. Specifically, a scale 
62 is fixedly attached to the housing 22 and, as indicated by 
cross-referencing FIGS. 5 and 6, the scale 62 is generally located in the 
same position as was the plate 54 in the embodiment previously disclosed 
for the sensor 48. Additionally, a photoelectric detector 64 is fixedly 
mounted on the bobbin 32 for movement therewith. The detector 64 can 
include photodiode elements 66 and 68 which, either individually or 
collectively, will interact optically with the scale 62, in a manner well 
known in the pertinent art, to provide information about the position of 
the bobbin 32 relative to the housing 22. 
Referring now to FIG. 9, it will be seen that one of the preferred 
embodiments of the present invention includes components which allow for 
both translational and rotational control over a work component 14 which 
is being moved by the rod/grip 24. Specifically, as with other embodiments 
of the present invention, a magnet 108 is mounted in the housing 22 and a 
coil 102 is disposed in the magnetic field established by the magnet 108. 
Also, as before, the coil 102 is fixedly attached to a coil piston 106 so 
that the coil piston 106 moves with coil 102 under the influences of 
forces which are generated on the coil in the magnetic field as a current 
is passed through the coil 102. 
FIG. 9 also shows that a casing 200 is attached to the coil piston, and 
that the casing 200 is slidably attached to housing 22. This attachment 
between casing 200 and housing 22 is established through the interaction 
of bearings 112' on casing 200 with bearing rail 114' on housing 22. It is 
also shown in FIG. 9 that the rod/grip 24 is rotatably mounted on the 
casing 200 for translational motion with the casing 200 and coil piston 
106. Additionally, an electrical servo motor 202, of any type well known 
in the pertinent art, is mounted in casing 200 for translational movement 
with coil piston 106. 
The electrical servo motor 202 is shown to be connected to the grip/rod 24 
by a linkage 204. More specifically, as more fully disclosed below, the 
linkage 204 is used for the purpose of transferring power from motor 202 
into a rotational motion of the grip/rod 24. Specifically, the interest 
here is in rotation of the grip/rod 24 about its longitudinal axis as 
indicated by the arrows 205 in FIG. 9. An optical encoder 206 is also 
mounted in the casing 202 for translational movement with motor 20 and 
coil piston 106. As shown, optical encoder 206 includes a light source 208 
and a light detector 210. Further, FIG. 9 shows that an encoder wheel 212 
is fixedly mounted on the grip/rod 24 for rotational movement with the 
grip/rod 24. Consequently, movement of the encoder wheel 212 due to 
rotation of the grip/rod 24 can be detected by interruption of the light 
beam passing between light source 208 and light detector 210. These 
interruptions can then be sent as signals via control cable 214 to 
microprocessor 70 for purposes to be more fully discussed below. It is to 
be appreciated, that the particular optical encoder 206 and encoder wheel 
212, and their operative interaction, can be duplicated by other means 
well known in the pertinent art. 
For the present invention, the linkage 214 can have several configurations. 
More specifically, FIGS. 10A, 10B and 10C show three possible 
configurations for linkage 214. In FIG. 10A, a belt drive mechanism is 
shown. For this particular configuration of linkage 214, the drive shaft 
216 of servo motor 202 has a pulley 218 attached to it. Similarly, a 
pulley 220 is attached to grip/rod 24 and a belt 222 passes around the 
edges of the pulleys 220 and 222. Consequently, rotation of the drive 
shaft 216 by servo motor 202 is transmitted via pulley 218 and through 
belt 222 to pulley 220 for rotation of grip/rod 24. 
FIG. 10B shows another embodiment for the linkage 214 wherein a gear 224 
having a plurality of teeth 226 on its peripheral edge is attached to the 
drive shaft 216 of servo motor 202. Also, for this embodiment a gear 228 
having a plurality of teeth 230 on its peripheral edge is attache to 
grip/rod 24. As shown, the teeth 226 of gear 224 mesh with teeth 230 of 
gear 228 so that rotation of drive shaft 216 by servo motor 202 is 
translated into a rotational movement of grip/rod 24. As between the 
embodiment of linkage 214 shown in FIG. 10A and the embodiment shown in 
FIG. 10B, the gears 224, 226 of the FIG. 10B embodiment are more likely to 
resist slippage. On the other hand, the embodiment for a linkage 214 shown 
in FIG. 10C allows for rotation of the grip/rod 24 without requiring 
physical contact with the grip/rod 24 and, thus, avoids mechanical 
backlash. 
For the embodiment of linkage 214 shown in FIG. 10C, grip/rod 24 is 
surrounded by a stator 232 and the servo electric drive motor 202 is 
replaced with an electronic drive 234. Also, a wiring harness 236 is used 
to electrically connect electronic drive 234 which each of the electrical 
coil magnets 238a-f which are mounted in stator 232. As intended for the 
present invention, electronic drive 234 will drive current through the 
electrical coil magnets 238a-f in a predetermined sequence to alternately 
change the polarization of the coil magnets 238 a-f. More specifically, 
while electrical coil magnets 238 a,c,e are established with a North (N) 
polarization, the electrical coil magnets 238 b,d,f will be established 
with a South (S) polarization. The reverse is also true. If magnets 238 
a,c,e have a South polarization, then magnets 238 b,d,f will have a North 
polarization. As will be appreciated by the skilled artisan, the 
polarization and the strength of the polarization of each magnet 238a-f 
can be controlled by current from electronic drive 234. 
In order for the embodiment of the linkage 214 shown in FIG. 10C to 
function, the portion of grip/rod 24 which is surrounded by stator 232 
must also be magnetized. For example, as shown in FIG. 10C, the grip/rod 
24 is magnetized with one side 240 being a North (N) pole and the other 
side 242 being a South (S) pole. Consequently, the magnetized grip/rod 24 
will react to changes in the magnetic polarity of the magnets 238a-f to 
cause the grip/rod 24 to rotate. Of course, while there is no change in 
current flow through the magnets 238a-f, and thus no change in polarity of 
the magnets 238a-f, grip/rod 24 will remain rotationally stationary. 
For an alternate embodiment of the present invention of the device 11 or 
100, the drive motor for rotating the grip/rod 24 is mounted directly on 
the housing 22. This drive motor 250 and a drive shaft 252 which extends 
from the drive motor 250 are shown in FIG. 11. For the particular 
embodiment shown in FIG. 11, and as perhaps best appreciated with cross 
reference to FIG. 10D, a belt 254 is used to connect a pulley 256 which is 
mounted on the drive shaft 252 with a pulley 258 which is also rotaionally 
mounted on the housing 22. FIGS. 11 and 10D both show that the grip/rod 
24' for this embodiment includes a plurality of splines 260, of which the 
splines 260a and 260b are merely exemplary. In a manner well known in the 
pertinent art, the splines 260 interact with the pulley 258 to allow the 
grip/rod 24' to slide through the pulley 258 while also requiring the 
grip/rod 24' to rotate with the pulley 258. A cable 262 is electrically 
connected to the central cable 214 to provide electrical power for the 
operation of drive motor 250. In all important respects the operation of 
drive motor 250 is the same as the operation of drive motor 202. Further 
the operation of the optical encoder 206 remains the same regardless of 
the location of the drive motor 202/250. 
Although the linkage between drive motor 250 and grip/rod 24' has so far 
focussed on the structure shown in FIG. 10D, it is to be appreciated that 
a linkage such as shown in FIG. 10B using toothed gears can also be 
incorporated. Similarly, the structure shown in FIG. 10C can be used 
together with an externally mounted drive motor 250. 
FIG. 12 shows an alternate arrangement for the cooperation between the 
magnets and coil of the device 11/100. For this embodiment a plurality of 
magnetic segments 264 and 266 are mounted on the housing 22 with the coil 
42 positioned between the segments 264 and 266. More specifically, as 
shown in FIG. 12 a series of magnetic segments 264a, b and can be stacked 
with their respective North (N) and South (S) poles located as shown to 
establish a magnet having a strength which can be varied according to the 
number of magnetic segments 264 used. Here the magnetic segment 264 a, b 
and c are only exemplary. Likewise, a series of magnetic segments 266, of 
which the magnetic segments 266a and b are exemplary, can be stacked as 
shown to help in the creation of a magnetic field. When the magnetic 
segments 264 and 266 are arranged as shown in FIG. 12, it will be 
appreciated that the coil 42 is effectively surrounded by magnets and 
that, contrary to the embodiment disclosed above for the device 11, the 
coil 42 is mounted on the housing 22 for reciprocal movement between the 
magnet segments 264 and 266, rather than having the coil 42 reciprocate 
over a projection of the magnet. 
OPERATION 
The general operation of the actuator device 11 or 100 will, perhaps, be 
best understood by reference to FIG. 7 and FIG. 8. In FIG. 7 it will be 
seen that a microprocessor 70, of any type well known in the pertinent 
art, is connected to both the voltage source 46 and the sensor 48. 
Additionally, microprocessor 70 is connected to a vacuum pump 72 which 
can, in turn, be operatively connected with the grip 24. Through these 
connections, the microprocessor 70 will interact with the voltage source 
46, the sensor 48 and the pump 72 in accordance with preprogrammed 
instructions. Although references here may be directed to the embodiment 
of the device 11 shown in FIGS. 2 and 4, it is to be understood that 
corresponding components of the actuator 100 operate in substantially the 
same manner. Their operation is considered to be equivalent. 
Initially, the device 11 (actuator 100) can be incorporated into the 
automated assembly machine 12 and calibrated to locate the end 74 of grip 
24 at a preselected distance from the conveyor 16. This establishes a 
reference datum for the cycle from which movement of the grip can be 
measured. Actually, as will be appreciated by the skilled artisan, any 
other appropriate reference may be used for this purpose. Regardless what 
reference is used, once a reference datum from which measurements can be 
made has been selected, the sensor 48 can be set for this datum. In 
accordance with preprogrammed instructions, the microprocessor 70 then 
activates the voltage source 46 to send an electrical current through the 
coil 42. Because the coil 42 is in the magnetic field of the magnet 38, 
the current which passes through the coil 42 causes bobbin 32 (or coil 
piston 106 for actuator 100) to move a distance which is proportionately 
determined and controlled by the amount, duration and direction of the 
current. It is known, for example, that with this disclosed arrangement, 
the grip 24 can be linearly moved through a distance of approximately two 
inches (2 in.) in around seventy milliseconds (70 ms) with effectively no 
bounce at the end of the stroke. State differently, movements of this 
nature can be made without noticeable changes in the direction of linear 
movement at the conclusion of the movement. 
Rotational movement of grip/rod 24 is also controlled by microprocessor 70. 
Specifically, microprocessor 70 can be preprogrammed to initiate rotation 
of product component 18 as desired by the operator. For instance, in some 
operations it is necessary to align the product component 14 both linearly 
and angularly before it is positioned or engaged with another component of 
the product being manufactured. Therefore, in addition to the linear 
alignment of the work component 14 discussed above, actuator 11 must 
sometimes be capable of rotating the component 14 into a proper alignment. 
To do this, signals from optical encoder 206 which are indicative of the 
angular position of wheel 212 and work component 14 are sent to 
microprocessor 70. Any difference between the actual angular orientation 
and a desired angular orientation is then corrected by signals from 
microprocessor 70 to servo motor 202 which accordingly rotates grip/rod 24 
to move work component 18 into a proper alignment. Similarly, in cases 
where it is necessary to rotate the product component 18 in order to screw 
or thread the component 14 into place, microprocessor 70 can activate 
servo motor 202 (or electronic drive 234) to rotate the component 14 as 
necessary. Further, it will be appreciated by the skilled artisan that 
grip/rod 24 can be either rotated through a desired angular rotation, or 
the grip/rod 24 can be rotated until there is a preselected torque 
resistance to further rotation. 
The microprocessor 70 can also be used to control the operation of a vacuum 
pump 72. This may be helpful for an embodiment of the device 11 which uses 
the creation of a partial vacuum in the lumen (not shown) of the tubular 
grip 24 to hold a component 14 against the end 74 of the grip 24. It is to 
be recognized that other gripping arrangements may also be used. The 
partial vacuum system disclosed herein is only exemplary. 
As intended for a representative cycle in the operation of the present 
invention, the device 11 is initially position as shown in FIG. 1 with the 
grip 24 positioned over a component 14 which is being taken into position 
for retrieval by the conveyor 16. Voltage source 46 is then activated in 
accordance with a preprogrammed sequence from microprocessor 70 to lower 
the end 74 of grip 24 into a position indicated for end 74'. In accordance 
with previous disclosure, this movement is accomplished by passing a 
predetermined current through the coil 42. Pump 72 is then activated to 
generate a partial vacuum within the lumen of grip 24 to suck and hold the 
component 14 against the end 74. Grip 24, with component 14 attached, is 
then withdrawn into the housing 22, by the activation of coil 42, and the 
device 11' is positioned over conveyor 20. Again, coil 42 is activated by 
the voltage source 46 to precisely lower component 14 to a desired stop 
point and into position on the component 18. This placement can be 
accomplished with great precision. For example, tolerances on the order of 
one one-hundredths of a millimeter (0.01 mm) have been accomplished using 
the device 11 of the present invention. Importantly, sensor 48 can be used 
to monitor this placement and thereby provide a real-time verification of 
proper assembly. 
In a similar manner, the angular rotation of the component 14 can be 
checked. In a manner similar to the linear positioning of the component 
14, the optical encoder 206 is useful for ensuring proper angular 
positioning of the component 14. As indicated above, microprocessor 70 is 
electrically connected to optical encoder 206 and, based upon signals 
received by microprocessor 70 from the optical encoder 206, errors in 
angular alignment can be corrected. This is done is a conventional manner 
by determining any error signals which are generated because of a 
difference between the actual and the desired angular orientation of the 
work component 14. 
Once component 14 has been properly positioned on the component 18, 
microprocessor 70 can be used to control the pump 72 to relieve the vacuum 
created in the grip 24 to release the component 14 from the grip 24. 
Again, the grip 24 is withdrawn into the housing 22 and the device 11 is 
repositioned over the conveyor 16 for another cycle of operation. 
An actual time history response for the position of rod 24 during a series 
of cycles is shown in FIG. 8 and is designated 130. The response 130 is, 
in fact, only exemplary. Indeed, rod 24 may be moved through greater or 
lesser distances and the time for each cycle may be varied. Nevertheless, 
response 130 is considered typical for the actuator 100 and is used here 
for discussion purposes. For the specific case illustrated in FIG. 8, the 
response 130 is shown over a one second period of time and indicates that 
the actuator 100 has moved rod 24 through four complete cycles during this 
one second interval. Further, FIG. 8 shows that rod 24 was reciprocally 
moved through a distance of approximately one and one tenth inches (1.1 
in) in each cycle. As indicated above, the position of rod 24 at any time 
during the cycle can be determined by encoder 122 to an accuracy within 
five thousandths of a millimeter (0.005 mm). Consequently, the completion 
of a cycle within a preprogrammed dimensional envelope can be used to 
indicate whether the work has been successfully completed. Additionally, 
with this control, and in view of the extremely small masses which are 
moved during the operation of actuator 100, the forces which are generated 
on a workpiece as it is being handled by actuator 100 will be very light. 
Tests have indicated that forces as small as five grams (5 gm) can be 
generated with actuator 100 and that forces of this small magnitude can be 
generated with an accuracy of plus or minus one gram (.+-.1 gm). 
For a more complete appreciation of the operational aspects of the actuator 
100, consider the idealized curve 132 which has been superimposed over the 
first cycle of the response 130. The curve 132 for this cycle begins at 
time zero with the rod 24 in its withdrawn position and ends approximately 
one quarter second later (0.25 sec) when the rod 24 has returned to its 
withdrawn position. A discussion of this cyclic operation is appropriately 
discussed by considering individual time intervals within a particular 
cycle. 
The beginning of the cycle is indicated in FIG. 8 by the top dead center 
portion 134 of curve 132. In practice, top dead center portion 134 
corresponds to the position 74 shown in FIG. 7 and, as shown, rod 24 stays 
in this position during approximately the 0.00-0.04 seconds interval of 
the cycle. A positioning stroke 136 for curve 132, which immediately 
follows top dead center portion 134, indicates that rod 24 is quickly 
moved through a distance of approximately one inch during the cycle 
interval from 0.04-0.09 seconds. This rapid movement of the rod 24 is 
possible due to the relatively small mass of the components in actuator 
100 which must move with the rod 24. A deceleration period during the 
interval 0.09-0.17 seconds of the cycle is provided to steadily move the 
rod 24 into proper position with precision and minimal inertial forces. 
Once contact has been established between the workpiece being carried by 
rod 24, and the substrate onto which the workpiece is being placed, there 
is an interval between approximately 0.17-0.21 seconds in the cycle 
wherein force is applied to attach or position the workpiece on the 
substrate. This interval is indicated as the force application period 140 
in FIG. 8. During period 140, the successful completion of the work can be 
verified by monitoring signals from encoder 122. Specifically, by 
comparing signals from encoder 122, which indicate the actual position of 
the rod 24 at this point in the work cycle, with a reference for the 
programmed position for rod 24 at this point during a successful work 
cycle, operational deviations can be determined. If this comparison 
indicates only minor deviations in the position of rod 24, and these 
deviations are within acceptable tolerances, the work cycle can be 
considered successful. 
After the force application period 140, the rod 24 is withdrawn back to a 
top dead center position during an interval in the cycle during 
approximately 0.21-0.25 seconds. The cycle is then repeated as necessary 
and the same intervals are used. As indicated above, the cycle discussed 
here in relation to the idealized curve 132 is only exemplary. The 
parameters which establish the operational envelope for actuator 100 and 
device 11 can be varied according to the desires of the operator. 
While the particular device for moving and positioning an assembly 
component in an automated assembly operation as herein shown and disclosed 
in detail is fully capable of obtaining the objects and providing the 
advantages herein before stated, it is to be understood that it is merely 
illustrative of the presently preferred embodiments of the invention and 
that no limitations are intended to the details of the construction or 
design herein shown other than as defined in the appended claims.