Current controller for a magnetorheological actuator
AssigneeOssur Iceland Ehf
InventorJón Trausti Kristmundsson
Life of this patent
Estimating the term…
Abstract
A prosthetic or orthotic device has an elongate frame that houses electronics and an actuator rotatably mounted to the frame. The actuator can rotate in an anterior-posterior direction about a medial-lateral axis and includes magnetorheological (MR) fluid and a coil operable to selectively apply a magnetic field to the MR fluid to vary its viscosity and thereby vary a torsional resistance of the actuator about the medial-lateral axis. Circuitry controls an amplitude of a current applied to the coil, and employs a gains schedule to accelerate a change in the current amplitude based on an error amplitude between a current set point and a measured current to reduce a response time for varying the torsional resistance of the actuator.
Claims20
A prosthetic or orthotic device, comprising:
- a frame configured to house electronics;
- an actuator movably coupled to the frame, the actuator configured to rotate in an anterior-posterior direction about a medial-lateral axis, the actuator comprising a magnetorheological (MR) fluid and a coil operable to selectively apply a magnetic field to the MR fluid to vary its viscosity and thereby vary a torsional resistance of the actuator about the medial-lateral axis;
- and
- circuitry configured to control an amplitude of a current applied to the coil, the circuitry configured to employ a gains schedule to accelerate a change in the current amplitude based on an error amplitude between a current set point and a measured current to reduce a response time for varying the torsional resistance of the actuator.
A method for controlling a prosthetic or orthotic device having a magnetorheological (MR) actuator, comprising:
- operating with a microprocessor a coil driver circuit to apply a current to a coil to selectively apply a magnetic field to a MR fluid in the MR actuator to vary its viscosity and thereby vary a resistance of the MR actuator, comprising
- determining a magnitude of a current to be applied to the coil,
- applying the current magnitude to the coil,
- measuring a current applied to the coil,
- comparing the measured current magnitude with the applied current magnitude, and
- adjusting the magnitude of the current applied to the coil so that an error corresponding to a difference between the measured current magnitude and the applied current magnitude decreases.
Dependencies are inferred from the claim text.