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EP-4741682-A2 - LINEAR ACTUATOR AND HUMANOID ROBOT COMPRISING THE SAME

EP4741682A2EP 4741682 A2EP4741682 A2EP 4741682A2EP-4741682-A2

Abstract

A linear actuator includes a housing; a motor module that includes a motor; and a drivetrain module coupled to the motor module. The drivetrain module includes a ball screw coupled to the motor, a ball nut coupled to and configured to linearly ride on the ball screw during rotation of the ball screw, a rod coupled to the ball nut and configured to extend or retract from the housing based on the ball nut linearly riding on the ball screw during rotation of the ball screw, and an anti-rotation bushing coupled to the rod and including at least one slot configured to engage with and linearly ride on a key coupled to an inner surface of the housing based on the ball nut linearly riding on the ball screw during rotation of the ball screw. The anti-rotation bushing is further configured to restrain the rod against rotation during extension and retraction.

Inventors

  • RESH, Bradley Aaron
  • FLEURY, Paul Gloninger
  • Paine, Nicholas Arden
  • FOX, Jonas Alexan
  • MITCHELL, Daniel Stephen
  • Cobau, James Cornelius

Assignees

  • Apptronik, Inc.

Dates

Publication Date
20260513
Application Date
20240308

Claims (15)

  1. A humanoid robot (400), comprising: at least one body assembly that comprises at least one body joint assembly; and at least one pair of linear actuators (100) that form the at least one body joint, the at least one pair of linear actuators configured to operate in combination to adjust the at least one body joint assembly in two degrees of freedom through differential linear actuation, each of the linear actuators comprising: a motor module (104) that comprises a motor (114); and a drivetrain module (102) coupled to the motor module and comprising: a ball screw (112) coupled to the motor, a ball nut (132) coupled to and configured to linearly ride on the ball screw during rotation of the ball screw, a rod (150) coupled to the ball nut and configured to extend or retract from the housing based on the ball nut linearly riding on the ball screw during rotation of the ball screw, and an anti-rotation bushing (122) coupled to the rod and comprising at least one slot (140) configured to engage with and linearly ride on a key (120) coupled to an inner surface of the housing based on the ball nut linearly riding on the ball screw during rotation of the ball screw, the anti-rotation bushing further configured to restrain the rod against rotation during extension and retraction.
  2. The humanoid robot of claim 1, wherein the at least one body assembly is an upper body assembly (404), and the at least one body joint assembly comprises at least one of a shoulder assembly (408), an upper arm assembly (410), or a lower arm assembly (412).
  3. The humanoid robot of claim 1 or 2, wherein the at least one body assembly is a lower body assembly (406), and the at least one body joint assembly comprises at least one of a hip assembly (422), an upper leg assembly (414), or a lower leg assembly (416).
  4. The humanoid robot of any of claims 1 to 3, wherein the body joint assembly comprises the upper leg assembly, and the at least one pair of joint linear actuators comprises: a first linear actuator of a first size; a second linear actuator of the first size; and a third linear actuator of a second size larger than the first size.
  5. The humanoid robot of any of claims 1 to 4, wherein the motor comprises a direct current, DC, motor, or wherein the motor comprises a direct current, DC, brushless and frameless motor.
  6. The humanoid robot of any of claims 1 to 5, wherein the anti-rotation bushing comprises a bore (142) configured to receive the rod.
  7. The humanoid robot of any of claims 1 to 6, wherein the anti-rotation bushing comprises at least one groove (144) formed on an inner radial surface of the anti-rotation bushing and configured to engage the rod.
  8. The humanoid robot of any of claims 1 to 7, wherein each of the linear actuators further comprises a sealed angular contact bearing (116) positioned in the housing between the motor module and the drivetrain module.
  9. The humanoid robot of any of claims 1 to 8, wherein each of the linear actuators further comprises a first bumper (118a) positioned in the housing between the motor module and the drivetrain module.
  10. The humanoid robot of any of claims 1 to 9, wherein each of the linear actuators further comprises a second bumper (118b) positioned in the housing at an end of the drivetrain module opposite the motor module.
  11. The humanoid robot of claim 9 or 10, wherein each of the first and second bumpers comprise urethane bumpers.
  12. The humanoid robot of any of claims 9 to 11, wherein the first bumper comprises a first stop that defines a retracted position of the rod when the ball nut is adjacent or abutting the first bumper, and/or wherein the second bumper comprises a second stop that defines an extended position of the rod when the ball nut is adjacent or abutting the second bumper.
  13. The humanoid robot of any of claims 1 to 12, wherein the anti-rotation bushing comprises a rigid, non-metallic material, and optionally wherein the rigid, non-metallic material comprises a plastic material.
  14. The humanoid robot of any of claims 1 to 13, wherein each of the linear actuators further comprises an encoder (124) configured to determine a number of rotations of the motor.
  15. The humanoid robot of any of claims 1 to 14, wherein a gear ratio of each of the linear actuators is between 40:1 and 50:1, or wherein a gear ratio of each of the linear actuators is no more than 100:1.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Contract Number 80NSSC22CA190 awarded by The National Aeronautics and Space Administration (NASA). The government has certain rights in the invention. TECHNICAL FIELD The present disclosure describes example implementations of a linear actuator and, more particularly, a linear ball screw actuator used in a humanoid robot. BACKGROUND Linear actuators are used in many different technologies in order to move a load or object bi-directionally in a linear fashion. Many linear actuators have a relatively large weight to performance ratio, i.e., they are heavy given their output linear force. Further, many linear actuators use a leadscrew as a drivetrain, which often results in high friction. For these reasons and others, conventional linear actuators are often unsuitable for mobile robots, such as quadruped robots and humanoid robots. SUMMARY In an example implementation, a linear actuator includes a housing; a motor module that includes a motor; and a drivetrain module coupled to the motor module. The drivetrain module includes a ball screw coupled to the motor, a ball nut coupled to and configured to linearly ride on the ball screw during rotation of the ball screw, a rod coupled to the ball nut and configured to extend or retract from the housing based on the ball nut linearly riding on the ball screw during rotation of the ball screw, and an anti-rotation bushing coupled to the rod and including at least one slot configured to engage with and linearly ride on a key coupled to an inner surface of the housing based on the ball nut linearly riding on the ball screw during rotation of the ball screw. The anti-rotation bushing is further configured to restrain the rod against rotation during extension and retraction. In an aspect combinable with the example implementation, the motor includes a direct current (DC) motor. In another aspect combinable with the any of the previous aspects, the motor includes a direct current (DC) brushless and frameless motor. In another aspect combinable with the any of the previous aspects, the anti-rotation bushing includes a bore configured to receive the rod. In another aspect combinable with the any of the previous aspects, the anti-rotation bushing includes at least one groove formed on an inner radial surface of the anti-rotation bushing and configured to engage the rod. Another aspect combinable with the any of the previous aspects further includes a sealed angular contact bearing positioned in the housing between the motor module and the drivetrain module. Another aspect combinable with the any of the previous aspects further includes a first bumper positioned in the housing between the motor module and the drivetrain module. Another aspect combinable with the any of the previous aspects further includes a second bumper positioned in the housing at an end of the drivetrain module opposite the motor module. In another aspect combinable with the any of the previous aspects, each of the first and second bumpers include urethane bumpers. In another aspect combinable with the any of the previous aspects, the first bumper includes a first stop that defines a retracted position of the rod when the ball nut is adjacent or abutting the first bumper. In another aspect combinable with the any of the previous aspects, the second bumper includes a second stop that defines an extended position of the rod when the ball nut is adjacent or abutting the second bumper. In another aspect combinable with the any of the previous aspects, the anti-rotation bushing includes a rigid, non-metallic material. In another aspect combinable with the any of the previous aspects, the rigid, non-metallic material includes a plastic material. Another aspect combinable with the any of the previous aspects further includes an encoder configured to determine a number of rotations of the motor. In another aspect combinable with the any of the previous aspects, a gear ratio is between 40:1 and 50:1. In another aspect combinable with the any of the previous aspects, a gear ratio is no more than 100:1. In another example implementation, a humanoid robot includes at least one body assembly that includes at least one body joint assembly; and at least one pair of linear actuators that form the at least one body joint, the at least one pair of linear actuators configured to operate in combination to adjust the at least one body joint assembly in two degrees of freedom through differential linear actuation. Each of the linear actuators includes a motor module that includes a motor; and a drivetrain module coupled to the motor module. The drivetrain module includes a ball screw coupled to the motor, a ball nut coupled to and configured to linearly ride on the ball screw during rotation of the ball screw, a rod coupled to the ball nut and configured to extend or retract from the housing based on the ball nu