ACTUATOR SYSTEM WITH A MULTI-MOTOR ASSEMBLY FOR EXTENDING AND FLEXING A JOINT

• US 20100039052A1
• Filed: 08/14/2008
• Published: 02/18/2010
• Est. Priority Date: 08/14/2008
• Status: Active Grant

• Current Assignee: AlterG, Inc.
• Original Assignee: Tibion Corporation (AlterG, Inc.)
• Inventors: Jardine, Robert L., Bhugra, Kern, Horst, Robert W.
• Granted Patent: US 8,058,823 B2
• Time in Patent Office: Days
• US Class Current: 318/8
• CPC Class Codes: A61H 1/0237 for the lower limbs
• CPC Class Codes: A61H 1/024 Knee A61H1/0255 takes precedence
• CPC Class Codes: A61H 1/0266 Foot
• CPC Class Codes: A61H 1/0274 for the upper limbs
• CPC Class Codes: A61H 1/0277 Elbow
• CPC Class Codes: A61H 1/0281 Shoulder
• CPC Class Codes: A61H 2201/1215 Rotary drive
• CPC Class Codes: A61H 2201/1445 Overrunning clutches; One-way clutches
• CPC Class Codes: A61H 2201/1463 Special speed variation means, i.e. speed reducer
• CPC Class Codes: A61H 2201/149 rotation-linear or vice versa
• CPC Class Codes: A61H 2201/5061 Force sensors
• CPC Class Codes: A61H 2201/5064 Position sensors
• CPC Class Codes: F16H 2025/2081 Parallel arrangement of drive motor to screw axis
• CPC Class Codes: F16H 25/20 Screw mechanisms with automatic reversal F16H25/12

Abstract

An actuator system for extending and flexing a joint, including a multi-motor assembly for providing a rotational output, a rotary-to-linear mechanism for converting the rotational output from the multi-motor assembly into an extension and flexion of the joint, and a controller for operating the actuator system in several operational modes. The multi-motor assembly preferably combines power from two different sources, such that the multi-motor assembly 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 (such as an ankle, a knee, an elbow, or a shoulder) of a human. The actuator system may, however, be used to move any suitable object through any suitable movement (linear, rotational, or otherwise).

Claims

1. An actuator system for extending and flexing a joint, comprising:

a multi-motor assembly for providing a rotational output;

a rotary-to-linear mechanism for converting the rotational output from the multi-motor assembly into an extension and flexion of the joint; and

a controller for operating the actuator system in several operational modes.

2. The actuator system of claim 1, wherein the multi-motor assembly includes:

a drive shaft that provides the rotational output to the rotary-to-linear mechanism;

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.

3. The actuator system of claim 2, wherein the first transmission defines a first gear ratio of the rotation of the drive shaft to the rotation of the first output shaft, and wherein the second transmission at least partially defines a second gear ratio of the rotation of the drive shaft to the rotation of the second output shaft, wherein the second gear ratio is different than the first gear ratio.

4. The actuator system of claim 3, wherein the second gear ratio is lower than the first gear ratio.

5. The actuator system of claim 3, wherein the second transmission connects the second output shaft to the first output shaft, and wherein the second transmission and the first transmission cooperatively define the second gear ratio.

6. The actuator system of claim 5, wherein the second motor subsystem further includes a one-way clutch located between the second motor and the first motor.

7. The actuator system of claim 3, wherein the second transmission connects the second output shaft to the drive shaft, and wherein the second transmission defines the second gear ratio.

8. The actuator system of claim 7, wherein the first motor subsystem includes a first motor, wherein the second motor subsystem includes a second motor, and wherein the first motor and the second motor have substantially identical performance characteristics.

9. The actuator system of claim 3, wherein the controller operates the actuator system in the following motor modes:

Continuously Variable Transmission motor mode—

in which the controller provides current to both the first motor subsystem and the second motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism; and

High Gear motor mode—

in which the controller provides current only to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism.

10. The actuator system of claim 9, wherein the controller varies the ratio of current provided to the first motor subsystem and current provided to the second motor subsystem to achieve a desired rotational output in the Continuously Variable Transmission motor mode.

11. The actuator system of claim 1, wherein the rotary-to-linear mechanism includes a screw that accepts the rotational output of the multi-motor assembly;

a nut that connects to the screw;

wherein the screw and the nut cooperate to convert rotational movement of the screw to linear movement of the nut.

12. The actuator system of claim 11, further comprising a moving rail having 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.

13. The actuator system of claim 12, wherein linear movement of the moving rail in the extension direction causes an extension of the joint.

14. The actuator system of claim 12, wherein the extension stop is movable between a force position that allows the nut to apply force against the extension stop, and a pass position that prevents the nut from applying force against the extension stop.

15. The actuator system of claim 12, wherein the moving rail also has 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.

16. The actuator system of claim 15, wherein linear movement of the moving rail in the flexion direction causes a flexion of the joint.

17. The actuator system of claim 15, wherein the flexion stop is movable between a force position that allows the nut to apply force against the flexion stop, and a pass position that prevents the nut from applying force against the flexion stop.

18. The actuator system of claim 15, wherein the extension stop and the flexion stop are located such that they allow significant movement of the moving rail back and forth between the extension stop and the flexion stop without moving the ball nut or back-driving the multi-motor assembly.

19. The actuator system of claim 12,

wherein the multi-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;

wherein the controller operates the actuator system in the following operational modes;

Continuously Variable Transmission Extension mode—

in which the controller provides current to both the first motor subsystem and the second motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the extension stop; and

High Gear Flexion mode—

in which the controller provides current only to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the flexion stop.

20. The actuator system of claim 19, wherein the controller varies the ratio of current provided to the first motor subsystem and current provided to the second motor subsystem to achieve a desired rotational output in the Continuously Variable Transmission Extension mode.

21. The actuator system of claim 19, wherein the controller also operates the actuator system in the following operational modes:

Low Gear Extension mode—

in which the controller provides current only to the second motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the extension stop;

High Gear Extension mode—

in which the controller provides current only to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the extension stop.

22. The actuator system of claim 19, wherein the controller also operates the actuator system in the following operational mode:

Free Movement mode—

in which the controller provides current to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut moves away from the extension stop.

23. An actuator system for extending and flexing a joint, comprising:

a multi-motor assembly including 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, wherein the first transmission defines a first gear ratio of the rotation of the drive shaft to the rotation of the first output shaft, and wherein the second transmission at least partially defines a second gear ratio of the rotation of the drive shaft to the rotation of the second output shaft, wherein the second gear ratio is lower than the first gear ratio;

a rotary-to-linear mechanism including a screw that accepts the rotational output of the drive shaft, a nut that cooperates with the screw to convert rotational movement of the screw to linear movement of the nut;

a moving rail including an extension stop that translates linear movement of the nut in an extension direction into an extension of the joint, and a flexion stop that translates linear movement of the nut in a flexion direction into a flexion of the joint,

a controller for operating the actuator system in the following operational modes;

Continuously Variable Transmission Extension mode—

in which the controller provides current to both the first motor subsystem and the second motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the extension stop; and

High Gear Flexion mode—

in which the controller provides current only to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the flexion stop.

24. The actuator system of claim 23, wherein the second transmission connects the second output shaft to the first output shaft, wherein the second motor subsystem further includes a one-way clutch located between the second motor and the first motor, wherein the second transmission and the first transmission cooperatively define the second gear ratio, and wherein the drive shaft and the screw are axially connected as a unitary part.

25. The actuator system of claim 23, wherein the controller varies the ratio of current provided to the first motor subsystem and current provided to the second motor subsystem to achieve a desired rotational output in the Continuously Variable Transmission Extension mode.

26. The actuator system of claim 23, wherein the controller also operates the actuator system in the following operational modes:

Low Gear Extension mode—

in which the controller provides current only to the second motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the extension stop;

High Gear Extension mode—

in which the controller provides current only to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut applies a force against the extension stop.

27. The actuator system of claim 23, wherein the controller also operates the actuator system in the following operational mode:

Free Movement mode—

in which the controller provides current to the first motor subsystem such that the multi-motor assembly provides a rotational output to the rotary-to-linear mechanism and the nut moves away from the extension stop.

28. A method for controlling an actuator system that extends and flexes a joint, the method comprising the steps of:

providing a multi-motor assembly including a drive shaft, a first motor subsystem having a first output shaft, and a second motor subsystem having a second output shaft;

coupling the first output shaft to the drive shaft with a first transmission;

coupling the second output shaft to the drive shaft with a second transmission;

providing current only to the first motor subsystem in High Gear mode; and

providing current to both the first motor subsystem and the second motor subsystem in a Continuously Variable Transmission mode.

29. The method of claim 28, wherein the step of providing current to both the first motor subsystem and the second motor subsystem includes varying the ratio of current provided to the first motor subsystem and current provided to the second motor subsystem to achieve a desired output.