U.S. patent application number 13/593366 was filed with the patent office on 2012-12-13 for actuator system with a motor assembly and latch for extending and flexing a joint.
This patent application is currently assigned to TIBION CORPORATION. Invention is credited to Kern Bhugra, Robert W. Horst, Richard R. Marcus, Jonathan Smith.
Application Number | 20120316475 13/593366 |
Document ID | / |
Family ID | 41680833 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120316475 |
Kind Code |
A1 |
Bhugra; Kern ; et
al. |
December 13, 2012 |
ACTUATOR SYSTEM WITH A MOTOR ASSEMBLY AND LATCH FOR EXTENDING AND
FLEXING A JOINT
Abstract
An actuator system for assisting extension of a biological joint
is provided with a motor assembly, a rotary-to-linear mechanism,
and an extension stop. The rotary-to-linear mechanism includes a
screw that accepts rotational output of the motor assembly, and a
nut that cooperates with the screw to convert rotational movement
of the screw to linear movement of the nut. The extension stop is
driven by linear movement of the nut in an extension direction to
cause extension of the biological joint. The motor assembly, the
rotary-to-linear mechanism and the extension stop cooperate to
allow unpowered flexion of the joint. The system is configured
without a flexion stop, and is configured such that the nut cannot
drive the joint in a flexion direction. Methods of use are also
disclosed.
Inventors: |
Bhugra; Kern; (San Jose,
CA) ; Horst; Robert W.; (San Jose, CA) ;
Marcus; Richard R.; (Mountain View, CA) ; Smith;
Jonathan; (New Brunswick, CA) |
Assignee: |
TIBION CORPORATION
Sunnyvale
CA
|
Family ID: |
41680833 |
Appl. No.: |
13/593366 |
Filed: |
August 23, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12363577 |
Jan 30, 2009 |
8274244 |
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13593366 |
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12191837 |
Aug 14, 2008 |
8058823 |
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12363577 |
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Current U.S.
Class: |
601/33 ;
74/89.23 |
Current CPC
Class: |
A61H 1/0237 20130101;
H02K 7/06 20130101; A61H 1/0274 20130101; Y10T 74/18576 20150115;
A61H 2201/5064 20130101; A61F 2002/5066 20130101; A61F 2002/701
20130101; A61F 2/70 20130101; A61F 2/6607 20130101; A61H 2201/5061
20130101 |
Class at
Publication: |
601/33 ;
74/89.23 |
International
Class: |
A61H 1/02 20060101
A61H001/02; F16H 19/02 20060101 F16H019/02 |
Claims
1. An actuator system for extending and flexing a joint,
comprising: a motor assembly that provides a rotational output; a
rotary-to-linear mechanism including a screw that accepts the
rotational output of the motor assembly, and a nut that cooperates
with the screw to convert rotational movement of the screw to
linear movement of the nut; and a latch that selectively allows at
least one of the following: linear movement of the nut in an
extension direction to cause extension of the joint, and a linear
movement of the nut in a flexion direction to cause flexion of the
joint.
2. The actuator system of claim 1, further comprising a moving rail
that moves linearly to cause flexion and extension of the joint;
wherein the latch is mounted to the moving rail.
3. The actuator system of claim 2, wherein the latch includes an
extension stop surface that translates linear movement of the nut
in an extension direction into linear movement of the moving rail
in the extension direction.
4. The actuator system of claim 3, wherein linear movement of the
moving rail in an extension direction causes an extension of the
joint.
5. The actuator system of claim 3, wherein the moving rail includes
a flexion stop that translates linear movement of the nut in a
flexion direction into linear movement of the moving rail in a
flexion direction.
6. The actuator system of claim 3, wherein the latch is movable
between an engaged position that allows the nut to apply force
against the extension stop surface of the latch and a disengaged
position that prevents the nut from applying force against the
extension stop surface of the latch.
7. The actuator system of claim 6, wherein the latch is movable
between the engaged position and disengaged position by sliding
relative to the nut to engage and disengage the nut.
8. The actuator system of claim 7, further comprising a switch
coupled to the latch, wherein the latch is selectable between the
engaged position and disengaged position by rotating the
switch.
9. The actuator system of claim 2, wherein the latch includes a
flexion stop surface that translates linear movement of the nut in
a flexion direction into linear movement of the moving rail in the
flexion direction.
10. The actuator system of claim 9, wherein linear movement of the
moving rail in a flexion direction causes a flexion of the
joint.
11. The actuator system of claim 9, wherein the moving rail
includes an extension stop that translates linear movement of the
nut in an extension direction into linear movement of the moving
rail in an extension direction.
12. The actuator system of claim 9, wherein the latch is movable
between an engaged position that allows the nut to apply force
against the flexion stop surface of the latch and a disengaged
position that prevents the nut from applying force against the
flexion stop surface of the latch.
13. The actuator system of claim 12, wherein the latch is movable
between the engaged position and disengaged position by sliding
relative to the nut to engage and disengage the nut.
14. The actuator system of claim 13, further comprising a switch
coupled to the latch, wherein the latch is selectable between the
engaged positing and disengaged position by rotating the
switch.
15. The actuator system of claim 2, wherein the latch includes: an
extension stop surface that translates linear movement of the nut
in an extension direction into linear movement of the moving rail
in the extension direction; and a flexion stop surface that
translates linear movement of the nut in a flexion direction into
linear movement of the moving rail in the flexion direction.
16. The actuator system of claim 15, wherein linear movement of the
moving rail in an extension direction causes an extension of the
joint; and linear movement of the moving rail in a flexion
direction causes a flexion of the joint.
17. The actuator system of claim 15, wherein the latch is movable
between an engaged position that allows the nut to apply force
against the latch and a disengaged position that prevents the nut
from applying force against the latch.
18. The actuator system of claim 17, wherein the latch is movable
between the engaged position and disengaged position by sliding
relative to the nut to engage and disengage the nut.
19. The actuator system of claim 18, further comprising a switch
coupled to the latch, wherein the latch is selectable between the
engaged position and disengaged position by rotating the
switch.
20. The actuator system of claim 15, wherein the extension stop
surface of the latch and the flexion stop surface of the latch are
located such that they allow significant movement of the moving
rail back and forth between the extension stop surface and the
flexion stop surface without moving the nut or back-driving the
multi-motor assembly.
21. The actuator system of claim 1, wherein the motor assembly
includes: a drive shaft that provides rotational output, a first
motor subsystem having a first output shaft and a first
transmission connecting the first output shaft to the drive shaft,
and a second motor subsystem having a second output shaft and a
second transmission coupling the second output shaft to the drive
shaft.
22. An actuator system for extending and flexing a joint,
comprising: a motor assembly that provides a rotational output; a
rotary-to-linear mechanism including a screw that accepts the
rotational output of the motor assembly, and a nut that cooperates
with the screw to convert rotational movement of the screw to
linear movement of the nut; a moving rail having an extension stop
that translates linear movement of the nut in an extension
direction into extension of the joint; and a latch that selectively
couples the nut and the moving rail and that includes a flexion
stop surface, wherein the latch is movable between a disengaged
position that prevents the nut from applying force against the
flexion stop surface of the latch and an engaged position that
allows the nut to apply force against the flexion stop surface of
the latch thereby translating linear movement of the nut in a
flexion direction into a flexion of the joint.
23. A method of assisting extension of a joint during a movement
cycle, the method comprising: attaching an actuator system to a
joint of a user; during one portion of the cycle, driving an
actuator of the system in an extension direction to deliver a high
force to the joint at a relatively low speed; and during another
portion of the cycle, allowing a limb associated with the joint to
move freely by driving the actuator with a smaller force and at a
higher speed.
24. The method of claim 23, wherein the user does not back-drive
the actuator during the free moving portion of the cycle.
25. The method of claim 23, wherein the actuator comprises at least
one motor that provides a rotational output, and a rotary-to-linear
mechanism that functions to convert the rotational output from the
motor into a linear movement that ultimately extends the joint of
the user.
26. The method of claim 25, wherein the actuator comprises two
motors, and the rotary-to-linear mechanism converts the rotational
output from both of the motors into the linear movement.
27. The method of claim 26, wherein one of the motors is used to
deliver high forces to the joint at relatively low speeds, and the
other motor is used to deliver smaller forces at higher speeds.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/363,577, filed Jan. 30, 2009, entitled
"ACTUATOR SYSTEM WITH A MOTOR ASSEMBLY AND LATCH FOR EXTENDING AND
FLEXING A JOINT", which is a continuation-in-part of U.S. patent
application Ser. No. 12/191,837, filed Aug. 14, 2008, entitled
"ACTUATOR SYSTEM WITH A MULTI-MOTOR ASSEMBLY FOR EXTENDING AND
FLEXING A JOINT", which are incorporated in their entirety by this
reference.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
TECHNICAL FIELD
[0003] This invention relates generally to the actuator field, and
more specifically to a new and useful actuator system with a motor
assembly in the actuator field.
BACKGROUND OF THE INVENTION
[0004] Motors and actuators are used in a wide variety of
applications. Many applications, including robotics and active
orthotics, require characteristics similar to human muscles. The
characteristics include the ability to deliver high force at a
relatively low speed and to allow free-movement when power is
removed, thereby allowing a limb to swing freely during portions of
the movement cycle. This may call for an actuator that can supply
larger forces at slower speeds and smaller forces at higher speeds,
or a variable ratio transmission (VRT) between the primary driver
input and the output of an actuator.
[0005] VRTs have been conventionally implemented as Continuously
Variable Transmissions (CVTs). The underlying principle of most
previous CVTs is to change the ratio of one or more gears by
changing the diameter of the gear, changing the place where a belt
rides on a conical pulley, or by coupling forces between rotating
disks with the radius of the intersection point varying based on
the desired ratio. Prior art CVTs have drawbacks in efficiency and
mechanical complexity.
[0006] Motors have been used in a variety of applications, but
typically a single motor is directly or indirectly coupled to
provide motion for each output direction. Use of a single motor
limits the speed/torque range or requires the extra cost and
complexity of a transmission between the motor and output. Thus,
there is a need in the actuator field to create a new and useful
actuator system that can supply larger forces at slower speeds and
smaller forces at higher speeds, but that minimizes or avoids the
disadvantages of the conventional CVTs. This invention provides
such a new and useful actuator system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic of the actuator system of the
preferred embodiment in an orthotic that extends and flexes a joint
of a user.
[0008] FIG. 2 is a schematic of the actuator system of the
preferred embodiment, with the first variation of the multi-motor
assembly and with both the extension stop and the flexion stop of
the rotary-to-linear mechanism in the force positions.
[0009] FIG. 3 is a schematic of the actuator system of the
preferred embodiment, with the second variation of the multi-motor
assembly.
[0010] FIG. 4a is a schematic of the actuator system of the
preferred embodiment, with the extension stop in the pass
position.
[0011] FIG. 4b is a schematic of the actuator system of a first
variation, with the flexion stop in the pass position.
[0012] FIG. 4c is a schematic of the actuator system of a second
variation, with the latch in the engaged position.
[0013] FIG. 4d is a schematic of the actuator system of a third
variation with both the flexion stop and extension stop in the
force positions.
[0014] FIG. 4e is a schematic of a side view, top view, and end
view of the flexion stop and extension stop in the force positions
in the actuator system of the third variation.
[0015] FIG. 4f is a schematic of the actuator system, with the
preferred variation of the moving rail.
[0016] FIG. 5 is a flow diagram of the operation modes for the
controller of the actuator system of the preferred embodiment.
[0017] FIG. 6 is an exemplary current ramping scheme for the
controller of the actuator system of the preferred embodiment.
[0018] FIG. 7 is a chart of the speed/force profile of the first
motor subsystem, the second motor subsystem, and the combination of
the first and second motor subsystems.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The following description of the preferred embodiments of
the invention is not intended to limit the invention to these
preferred embodiments, but rather to enable any person skilled in
the art of actuator systems to make and use this invention.
[0020] As shown in FIGS. 1 and 2, the actuator system 100 of the
preferred embodiments for extending and flexing a joint 110 of a
user includes a multi-motor assembly 120 for providing a rotational
output, a rotary-to-linear mechanism 150 for converting the
rotational output from the multi-motor assembly 120 into a linear
motion that ultimately extends and flexes the joint, and a
controller for operating the actuator system 100 in several
operational modes. The multi-motor assembly 120 preferably combines
power from two different sources, such that the multi-motor
assembly 120 can supply larger forces at slower speeds ("Low Gear")
and smaller forces at higher speeds ("High Gear"). The actuator has
been specifically designed for extending and flexing a joint 110
(such as an ankle, a knee, an elbow, or a shoulder) of a human or
robot. The actuator system 100 may, however, be used to move any
suitable object through any suitable movement (linear, rotational,
or otherwise).
1. Multi-Motor Assembly
[0021] As shown in FIG. 2, the multi-motor assembly 120 of the
preferred embodiments functions to provide rotational output to the
rotary-to-linear mechanism 150. The multi-motor assembly 120
includes a drive shaft 122, a first motor subsystem 124, and a
second motor subsystem 126. The drive shaft 122 functions to
deliver the rotational output from the multi-motor assembly 120.
The first motor subsystem 124 functions to provide a component of
the rotational output of the multi-motor assembly 120. The first
motor subsystem 124 includes a first motor 128, a first output
shaft 130, and a first transmission 132. The second motor subsystem
126 functions to provide another component of the rotational output
of the multi-motor assembly 120. The second motor subsystem 126
includes a second motor 134, a second output shaft 136, and a
second transmission 138.
[0022] The first motor 128 of the first motor subsystem 124
functions to provide a first source of power, and the first output
shaft 130 functions to deliver this power to the other elements of
the first motor subsystem 124. The first motor 128 is preferably a
three phase brushless electric motor with an outer rotor and seven
pole pairs. The first motor 128, which is preferably supplied by
Hyperion under the model number G2220-14, has a peak current of 35
A and a peak power of 388 W. The first motor 128 may, of course, be
a different type with different specifications and parameters
depending on the design of the actuator system 100.
[0023] The first transmission 132 of the first motor subsystem 124
functions to transmit the power from the first output shaft 130 to
the drive shaft 122. The first transmission 132 preferably includes
two pulleys (one mounted on the first output shaft 130 and one
mounted on the drive shaft 122) and a belt or chain connecting the
two pulleys. The first transmission 132 may alternatively include
gears or any other suitable device or method that transmits the
power from the first output shaft 130 to the drive shaft 122. The
first transmission 132 also preferably functions to define a first
gear ratio of the rotation of the drive shaft 122 to the rotation
of the first output shaft 130. In the preferred embodiment, the
pulley (or gear) mounted to the first output shaft 130 is smaller
than the pulley (or gear) mounted to the drive shaft 122, such that
the first gear ratio is less than 1:1 (e.g., 1:4). In alternative
embodiments, the first gear ratio may be 1:1 or may be greater than
1:1 (e.g., 4:1) depending on the design of the actuator system
100.
[0024] The second motor 134 of the second motor subsystem 126
functions to provide a second source of power, and the second
output shaft 136 functions to deliver this power to the other
elements of the second motor subsystem 126. The second motor 134,
like the first motor 128, is preferably a three phase brushless
electric motor with an outer rotor and seven pole pairs. The second
motor 134, which is preferably supplied by Hyperion under the model
number G2220-14, has a peak current of 35 A and a peak power of 388
W. The second motor 134 is preferably identical to the first motor
128 in design and performance characteristics, which functions to
reduce part count and manufacturing complexity. The second motor
134 may, however, be a different type with different specifications
and parameters depending on the design of the actuator system 100.
The second output shaft 136 functions to deliver the power of the
second motor 134 to the other elements of the second motor
subsystem 126.
[0025] The second transmission 138 of the second motor subsystem
126 functions to transmit the power from the second output shaft
136 to the drive shaft 122. The second transmission 138 preferably
includes two pulleys (one mounted on the second output shaft 136
and one mounted on the drive shaft 122) and a belt or chain
connecting the two pulleys. The second transmission 138 may
alternatively include gears or any other suitable device or method
that transmits the power from the second output shaft 136 to the
drive shaft 122. The second transmission 138 also preferably
functions to at least partially define the second gear ratio of the
rotation of the drive shaft 122 to the rotation of the second
output shaft 136. In the preferred embodiment, the pulley (or gear)
mounted to the second output shaft 136 is smaller than the pulley
(or gear) mounted to the drive shaft 122, such that the second gear
ratio is less than 1:1 (e.g., 1:4). In alternative embodiments, the
second gear ratio may be 1:1 or may be greater than 1:1 (e.g., 4:1)
depending on the design of the actuator system 100.
[0026] The power from the first motor subsystem 124 and the power
from the second motor subsystem 126 preferably have different
characteristics, such that the multi-motor assembly 120 can supply
larger forces at slower speeds ("Low Gear") and smaller forces at
higher speeds ("High Gear"). This may be accomplished by using
different motors in the first motor subsystem 124 and the second
motor subsystem 126. In the preferred embodiment, however, this is
accomplished by using identical motors, but with transmissions that
define different gear ratios for the first motor subsystem 124 and
the second motor subsystem 126. The second gear ratio is preferably
lower than the first gear ratio, but the actuator system 100 may be
re-arranged such that the second gear ratio is higher than the
first gear ratio.
[0027] The second transmission 138 of the second motor subsystem
126 preferably connects the second output shaft 136 to the first
output shaft 130. With this arrangement, the power from the second
motor 134 is transmitted through both the second transmission 138
and the first transmission 132 before reaching the drive shaft 122.
Thus, the second transmission 138 and the first transmission 132
cooperatively define the second gear ratio. The effective gear
ratio from motor 134 to the drive shaft 122 is a product of the
first transmission 132 and the second transmission 138. For
example, if the gear ratios of both the first transmission 132 and
the second transmission 138 were 1:3, then the effective gear ratio
from motor 134 to the drive shaft 122 would be 1:9. By leveraging
the first transmission 132, this variation provides a compact form
factor. Using the example, the system would be able to provide an
effective gear ratio of 1:9 without the need for a large pulley or
gear system.
[0028] As shown in FIG. 3, a second transmission 238 of a variation
of the second motor subsystem 226 connects the second output shaft
236 to the drive shaft 122. In this variation, the power from the
second motor 234 is transmitted through only the second
transmission 238 before reaching the drive shaft 122 (and, thus,
the second transmission 238 defines the second gear ratio). By
separately connecting the first motor 128 and the second motor 234
to the drive shaft 122, the first gear ratio and the second gear
ratio may be specifically tailored for the actuator system 100.
[0029] As shown in FIG. 2, the multi-motor assembly 120 of the
preferred embodiment also includes a one-way clutch 140 located
between the second motor 134 and the drive shaft 122. The one-way
clutch 140 functions to facilitate the following motor modes:
[0029]High Gear motor mode--the first motor subsystem 124 provides
powers in a first direction without spinning the second output
shaft 136 and imparting drag from the second motor subsystem 126,
[0030]Low Gear motor mode--the second motor subsystem 126 provides
power in the first direction (with drag from the first motor
subsystem 124), [0031 ]Combined motor mode--the first motor
subsystem 124 and the second motor subsystem 126 provide power in
the first direction, and [0032]High Gear motor mode--the first
motor subsystem 124 provides power in an opposite direction (with
drag from the second motor subsystem 126).
[0030] In a first variation of the multi-motor assembly 120, as
introduced above, the one-way clutch 140 is preferably located
within the second transmission 138 and, more specifically, in the
pulley mounted on the first output shaft 130. In other variations,
the one-way clutch 140 may be mounted in any suitable location
between the second motor 134 and the drive shaft 122.
[0031] The multi-motor assembly 120 of the preferred embodiment
also includes a power source (not shown). The power source is
preferably six lithium polymer battery cells, supplied by Emerging
Power under the model number 603462H1. The battery cells are
preferably arranged in both series and parallel (3S2P) to provide a
voltage of 11.1V (nominal) and a capacity of 2640 maH. The power
source may, however, be any suitable type, including both power
supplied by the power grid and other portable sources (e.g., fuel
cells), depending on the design of the actuator system 100.
2. Rotary-to-Linear Mechanism
[0032] The rotary-to-linear mechanism 150 of the preferred
embodiment functions to convert the rotational output from the
multi-motor assembly 120 into a linear movement that ultimately
extends and flexes the joint of the user. In the preferred
embodiment, the rotary-to-linear mechanism 150 includes a ball
screw 152 that accepts the rotational output of the multi-motor
assembly 120 and a ball nut 154 that connects to the ball screw 152
and cooperates with the ball screw 152 to convert rotational
movement of the ball screw 152 to linear movement of the ball nut
154. The drive shaft 122 of the multi-motor assembly 120 and the
ball screw 152 of the rotary-to-linear mechanism 150 are preferably
different sections of the same shaft. One section includes a pulley
(or gear) from the first transmission 132, while another section
includes a semi-circular, helical groove of the ball screw 152. The
drive shaft 122 and the ball screw 152 may, however, be separate
shafts connected in any suitable manner, such as through a pulley
or gear arrangement. In alternative embodiments, the
rotary-to-linear mechanism 150 may include any suitable device or
method that converts the rotational output from the multi-motor
assembly 120 into an extension and flexion of the joint.
[0033] The rotary-to-linear mechanism 150 of the preferred
embodiment also includes a linear slide 156 with a moving rail 158
that moves in a flexion direction and an extension direction. The
linear slide 156 functions to provide a supported structure when
the joint is fully flexed, and a compact structure when the joint
is fully extended. The linear slide 156 preferably includes
stationary wheels and moving wheels, but may alternatively include
any suitable device or method to allow the moving rail 158 to move
in the flex and extended directions.
[0034] As shown in FIGS. 2 and 4a, the moving rail 158 of the
linear slide 156 preferably includes an extension stop 160, which
functions to translate linear movement of the ball nut 154 in an
extension direction into an extension of the joint. In the
preferred embodiment, the extension stop 160 is movable between a
force position (shown in FIG. 2) that allows the ball nut 154 to
apply force against the extension stop 160, and a pass position
(shown in FIG. 4a) that prevents the ball nut 154 from applying
force against the extension stop 160. In the force position, the
extension stop 160 preferably applies a symmetric force to the ball
nut 154 to avoid damaging or obstructing the ball nut. The
extension stop 160 is preferably U-shaped and pivotally mounted on
the moving rail 158, but may alternatively be shaped and mounted in
any manner to allow movement from the force position to the pass
position. In an alternative embodiment, the extension stop 160 may
be permanently (or semi-permanently) fixed or fastened in the force
position.
[0035] In a first variation, as shown in FIGS. 2 and 4b, the moving
rail 158 of the linear slide 156 also includes a flexion stop 162,
which functions to translate linear movement of the ball nut 154 in
a flexion direction into a flexion of the joint. The flexion stop
162 is preferably movable between a force position (shown in FIG.
2) that allows the ball nut 154 to apply force against the flexion
stop 162, and a pass position (shown in FIG. 4b) that prevents the
ball nut 154 from applying force against the flexion stop 162. Like
the extension stop 160, the flexion stop 162 preferably applies a
symmetric force to the ball nut 154 when in the force position, to
avoid damaging or obstructing the ball nut. The flexion stop 162,
like the extension stop 160, is preferably U-shaped and pivotally
mounted on the moving rail 158. In another variation, the flexion
stop 162 is pivotally mounted on the extension stop 160 (as shown
in FIG. 4d) to be movable between a force position (as shown in
FIGS. 4d and 4e) and a pass position. The flexion stop 162 may,
however, alternatively be shaped and mounted in any manner to allow
movement from the force position to the pass position. The flexion
stop 162 may alternatively be permanently (or semi-permanently)
fixed or fastened in the force position.
[0036] In a second variation, as shown in FIG. 4c, the moving rail
158 of the linear slide 156 may additionally or alternatively
include a latch 262, which functions to translate linear movement
of the ball nut 154 in both the flexion and extension directions
into a flexion and extension of the joint. In the preferred
embodiment, the latch 262 includes a flexion stop surface and an
extension stop surface. Similar to the flexion stop 162 in the
first variation, the flexion stop surface of the latch functions to
translate linear movement of the ball nut 154 in a flexion
direction into a flexion of the joint. Similar to the extension
stop 160 in the first variation, the extension stop surface of the
latch functions to translate linear movement of the ball nut 154 in
an extension direction into an extension of the joint. The latch
262 is preferably movable between an engaged position (shown in
FIG. 4c) that allows the ball nut 154 to apply force against the
extension stop surface and/or flexion stop surface of the latch to
move the latch 262 and the moving rail, and a disengaged position
(not shown) that prevents the ball nut 154 from applying force
against the latch 262. Similar to the extension stop 160 and
flexion stop 162 in the force position, the latch 262 preferably
applies a symmetric force to the ball nut 154 when in the engaged
position, to avoid damaging or obstructing the ball nut. The latch
262, unlike the extension stop 160, is preferably mounted to engage
and disengage in a slidable manner towards and away from the ball
nut 154. The extension stop surface and flexion stop surface of the
latch 262 preferably are sides of a rectangular side cutout 262 in
the moving rail 158 (shown in FIG. 4f, into which an extended arm
254 coupled to the ball nut 154 engages and disengages in a
slidable manner. The extended arm 254, which is spring-loaded to
default to the engaged position, slides into the side cutout to
move into the engaged position, and slides out of the side cutout
to move into the disengaged position. The latch 262 is preferably
selected in the engaged position or disengaged position with a knob
264 (shown in FIG. 4f)coupled to the latch with a linkage mechanism
266 that pushes the extended arm 254 into the disengaged position
and releases the extended arm 254 into the engaged position. The
knob 264 is preferably movable between two discrete positions, one
for latch engagement and one for latch disengagement, with the use
of a ball plunger pressing against two discrete indentations,
positioning a pin in one of a hole corresponding to latch
engagement and a hole corresponding to latch disengagement, or any
suitable mechanism.
[0037] The latch 262 may alternatively engage and disengage the
ball nut 154 in a pivoting manner in a direction that is lateral to
the moving rail 158, or be shaped and mounted in any manner to
allow movement from the engaged position to the disengaged
position. The latch 262 may also alternatively be selected with a
lever, manual handle, switch, an electronic switch, and/or any
other suitable means of moving the latch between the engaged
position and the disengaged position.
[0038] In another variation, the latch 262 is coupled to the ball
nut 154 in an engaged position and free of the ball nut 154 in a
disengaged position. Similar to the second variation, the latch 262
is movable between the engaged position and the disengaged
position. When the latch 262 is in the engaged position, the latch
262 is coupled to the ball nut 154 such that linear movement of the
nut in flexion and extension directions causes the latch 262 to
move in flexion and extension directions and translate flexion and
extension directions into a flexion and extension of the joint.
When the latch 262 is in the disengaged position, the ball nut 154
moves independently of the latch 262 such that linear movement of
the ball nut 154 does not cause the latch 262 to move.
[0039] In another variation, the flexion stop 162 and latch 262 may
be omitted to allow unpowered flexion of the joint. In yet another
variation, the extension stop 160 and flexion stop 162 may be
omitted to allow unpowered extension and flexion of the joint.
[0040] The extension stop 160 and the flexion stop 162 are
preferably located relatively far from each other, which allows the
joint of the user to experience "free movement", essentially moving
the moving rail 158 back and forth between the extension stop 160
and the flexion stop 162 without the need to move the ball nut 154
or back-drive the multi-motor assembly 120. In a variation, the
extension stop 160 and the flexion stop 162 are located relatively
close to each other, which prevents the joint of the user from
experiencing little or no "free movement". In other words, movement
of the moving rail 158 will move the ball nut 154 and back-drive
the multi-motor assembly 120. Similar to the extension stop 160 and
flexion stop 162, the extension stop surface and flexion stop
surface of latch 262 are preferably located relatively far from
each other, but in a variation, the extension stop surface and
flexion stop surface of the latch are located relatively close to
each other.
[0041] As shown in FIG. 1, the actuator system 100 of the preferred
embodiments for extending and flexing a joint 110 of a user
includes a rotary-to-linear mechanism that functions to convert the
linear movement of the moving rail into an extension and flexion
(both rotational movements) of the joint of the user. In other
variations, the actuator system 100 may include gears, pulleys, or
any other suitable mechanism to ultimately extend and flex the
joint of the user.
3. Controller
[0042] The controller of the preferred embodiment functions to
operate the actuator system 100 in one of several operation modes.
The controller preferably includes sensors to estimate the position
of the moving rail 158, and a sensor on the motor 129 to maintain
the position of the ball nut 154. Additional sensors estimate the
force either provided by the multi-motor assembly 120 (for
instance, via current sensors) or the total force applied to the
joint via force sensors coupled to the thrust bearings (not shown)
supporting drive shaft 122. The controller may also include other
sensors to predict or determine future forces applied to the joint
or needed by the multi-motor assembly 120. The controller may,
however, use any suitable method or device to estimate the position
of the moving rail 158 and the torque required from the multi-motor
assembly 120.
[0043] Based on the position of the moving rail 158 and the force
needed by the multi-motor assembly 120, the controller provides
current to the first motor subsystem 124, the second motor
subsystem 126, or both the first motor subsystem 124 and the second
motor subsystem 126. As shown in FIG. 5, the controller preferably
operates the multi-motor assembly 120 of the actuator system 100 in
the following operation modes: High Gear Flexion mode, High Gear
Extension mode, Low Gear Extension mode, and Continuously Variable
Transmission Extension mode.
[0044] In the High Gear Flexion mode, the controller provides
current only to the first motor subsystem 124 such that the
multi-motor assembly 120 provides a rotational output to the
rotary-to-linear mechanism 150. The ball screw 152 is driven in the
direction such that the ball nut 154 applies a force against the
flexion stop 162 (if positioned in the force position) and drives
the moving rail 158 in the flexion direction. The High Gear Flexion
mode supplies a smaller force at a higher speed to quickly flex the
joint of the user.
[0045] The High Gear Extension mode is similar to the High Gear
Flexion mode, except the first motor subsystem 124 is driven in the
opposite direction. In the High Gear Extension mode, the controller
provides current only to the first motor subsystem 124 such that
the multi-motor assembly 120 provides a rotational output to the
rotary-to-linear mechanism 150 and the ball nut 154 applies a force
against the extension stop 160. The ball screw 152 is driven in the
direction such that the ball nut 154 applies a force against the
extension stop 160 (if positioned in the force position) and drives
the moving rail 158 in the extension direction. The High Gear
Extension mode supplies a smaller force at a higher speed to
quickly extend the joint of the user.
[0046] The Low Gear Extension mode is similar to the High Gear
Extension mode, except the second motor subsystem 126 is driven
instead of the first motor subsystem 124. In the Low Gear Extension
mode, the controller provides current only to the second motor
subsystem 126 such that the multi-motor assembly 120 provides a
rotational output to the rotary-to-linear mechanism 150 and the
ball nut 154 applies a force against the extension stop 160. The
ball screw 152 is driven in the direction such that the ball nut
154 applies a force against the extension stop 160 (if positioned
in the force position) and drives the moving rail 158 in the
extension direction. The Low Gear Extension mode supplies a larger
force at a lower speed to forcefully extend the joint of the
user.
[0047] In the Continuously Variable Transmission Extension mode,
the controller provides current to both the first motor subsystem
124 and the second motor subsystem 126 such that the multi-motor
assembly 120 provides a rotational output to the rotary-to-linear
mechanism 150 and the ball nut 154 applies a force against the
extension stop 160. In this mode, as exemplified in FIG. 6, the
controller varies the ratio of current provided to the first motor
subsystem 124 and current provided to the second motor subsystem
126 to achieve a desired rotational output in the Continuously
Variable Transmission Extension mode. As the controller senses an
increased force needed by the multi-motor assembly 120, the
controller preferably first ramps up the current to the first motor
subsystem 124 (the High Gear or "HG"), then ramps down the current
to the first motor subsystem 124 while ramping up the current to
the second motor subsystem 126 (the Low Gear or "LG"). The
Continuously Variable Transmission Extension mode can supply both a
smaller force at a higher speed to quickly extend the joint of the
user ("High Gear"), and a larger force at a lower speed to
forcefully extend the joint of the user ("Low Gear"). More
importantly, as shown in FIG. 7, by varying the ratio of current
provided to the first motor subsystem 124 and current provided to
the second motor subsystem 126, the controller can achieve a
desired force and speed from the multi-motor subsystem that is
outside the range of possible forces and speeds supplied by just
the first motor 128 or the second motor 134. The actuator system
100 provides these advantages and features without providing a
conventional multi-gear transmission or conventional CTV (with
gears, conical pulleys, etc.).
[0048] As shown in FIG. 5, the controller of the preferred
embodiment also operates the actuator system 100 in a Free Movement
mode. In one variation of the Free Movement mode, the controller
provides current to the first motor subsystem 124 such that the
multi-motor assembly 120 provides a rotational output to the
rotary-to-linear mechanism 150 and the ball nut 154 moves away from
the extension stop 160. In another variation of the Free Movement
mode, the controller provides current to the first motor subsystem
124 such that the multi-motor assembly 120 provides a rotational
output to the rotary-to-linear mechanism 150 and the ball nut 154
maintains a general position between--but not contacting--the
extension stop 160 or the flexion stop 162.
4. Further Embodiments
[0049] As a person skilled in the art of actuator system 100s will
recognize from the previous detailed description and from the
figures and claims, modifications and changes can be made to the
preferred embodiments of the invention without departing from the
scope of this invention defined in the following claims. As a first
example, while the actuator system 100 has been described to
include a multi-motor assembly 120 with a first motor 128 and a
second motor 134, the multi-motor assembly 120 may include
additional motors (with or without additional one-way clutches
140). As an additional example, while the actuator system 100 has
been described to include a rotary-to-linear mechanism 150, it is
possible that the rotational output of the multi-motor assembly 120
may be used without a mechanism that converts the rotational output
to a linear output.
* * * * *