Elastic actuator for precise force control

• US 5,650,704 A
• Filed: 06/29/1995
• Issued: 07/22/1997
• Est. Priority Date: 06/29/1995
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Pratt, Gill A., Williamson, Matthew M.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US08/496,419
• Time in Patent Office: 754 Days
• Field of Search: 318/560-696, 901/20-47, 395/95, 294/106-111, 74/501 M, 73/862.48
• US Class Current: 318/623
• CPC Class Codes: B25J 9/10 characterised by positioning means for manipulator elements
• CPC Class Codes: H02K 11/00 Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection casings, enclosures or supports H02K5/00
• CPC Class Codes: H02K 26/00 Machines adapted to function as torque motors, i.e. to exert a torque when stalled
• CPC Class Codes: H02K 41/00 Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path electromagnetic launchers F41B6/00
• CPC Class Codes: H02K 7/003 Couplings; Details of shafts means for mounting rotors on shafts H02K1/28

Abstract

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section.

Claims

1. An elastic actuator having gone control, the actuator comprising:

a motor;

a motor drive transmission connected at an output of the motor;

at least one elastic element connected in series with the motor drive transmission, the at least one elastic element positioned to fully support along either direction of an actuation axis, a load connected at at least one output of the actuator, as the load is actuated along either direction of the actuation axis,

a single force transducer positioned at a point between a mount for the motor and at least one output of the actuator, the force transducer generating a force signal indicating force applied by the elastic element to at least one output of the actuator; and

an active feedback force controller connected between the force transducer and the motor for controlling the motor, based on the force signal, to deflect the elastic element an amount that produces a desired actuator output force, the output force being substantially independent of load motion.

2. The elastic actuator of claim 1 wherein the force transducer comprises a strain gauge.

3. The elastic actuator of claim 1 wherein the force transducer comprises a strain gauge positioned on the elastic element.

4. The elastic actuator of claim 1 wherein the force transducer comprises a potentiometer.

5. The elastic actuator of claim 1 wherein the elastic element comprises a linear spring.

6. The elastic actuator of claim 1 wherein elastic element comprises a torsional spring.

7. The elastic actuator of claim 1 wherein the force signal generated by the force transducer is based on deflection of the elastic element.

8. The elastic actuator of claim 1 wherein the force transducer comprises a magnetic position transducer.

9. The elastic actuator of claim 1 wherein the force transducer comprises an optical position sensor.