Positive feedback position servo
AssigneeAmpex Corporation
InventorsJeffrey L. Fincher, Lauren V. Merritt, Gordon D. Svendsen
Life of this patent
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Abstract
A position servo system is described for positioning a member mounted on a spring. The spring provides a force opposing the motion of the member from an initial position. A position actuator, for example a motor, applies a force in response to a position request signal for moving the member to a desired position. A portion of the position feedback signal is applied from a position sensor to the motor as a positive feedback signal to compensate for the force of the spring. A steady state position error of the servo system is thereby substantially reduced to zero. A circuit and method for calibrating the positive feedback signal are also described.
Claims28
A position servo system for positioning a member by means of a position actuator, said member being attached to a spring means, said spring means providing a force opposing a motion of said member from an initial position, comprising:
- sensor means for detecting an actual position of said member and providing a corresponding position feedback signal;
- summing means coupled to receive a position request signal and said position feedback signal, and to provide an error signal as a difference of said received signals;
- said position actuator coupled to receive said error signal and to apply a force necessary to overcome said force provided by said spring means and to move said member to a desired position;
- means coupled to apply a portion of said position feedback signal as a positive feedback signal to said position actuator to compensate for said force provided by said spring means;
- and
- programmable digital control means coupled to vary a magnitude of said positive feedback signal to obtain a substantially zero steady state error.
A system for positioning a magnetic transducer in response to a position request signal, said transducer being mounted on a moveable mount attached to a spring means, said spring means providing a force opposing a motion of said transducer from an initial position, comprising:
- first means for detecting an actual position of said transducer and providing a corresponding position feedback signal;
- second means for receiving said position request signal and said position feedback signal and providing a difference of said signals to obtain an error signal;
- motor means coupled to apply a force necessary to overcome said force provided by said spring means and to move said transducer to a desired position;
- third means coupled to provide a portion of said position feedback signal as a positive feedback signal to compensate for said force provided by said spring means;
- and
- fourth means for receiving said error signal and said positive feedback signal, providing a sum of said signals and applying said sum as a drive signal to said motor.
A position servo system for positioning a member by means of a position actuator, said member being attached to a spring means, said spring means providing a force opposing a motion of said member from an initial position, comprising:
- sensor means for detecting an actual position of said member and providing a corresponding position feedback signal;
- summing means coupled to receive a position request signal and said position feedback signal, and to provide an error signal as a difference of said received signals;
- said position actuator coupled to receive said error signal and to apply a force necessary to overcome said force provided by said spring means and to move said member to a desired position;
- means coupled to calibrate a portion of said position feedback signal and apply said calibrated signal as a positive feedback signal to said position actuator to compensate for said force provided by said spring means
- to obtain a substantially zero steady state error signal.
A system for positioning a magnetic transducer in response to a position request signal, said transducer being mounted on a moveable mount attached to a spring means, said spring means opposing a motion of said transducer from an initial position, comprising:
- first means for detecting an actual position of said transducer and providing a corresponding position feedback signal;
- second means for receiving said position request signal and said position feedback signal and providing a difference of said signals to obtain an error signal;
- motor means coupled to apply a force necessary to overcome said force provided by said spring means and to move said transducer to a desired position;
- third means coupled to provide a portion of said position feedback signal as a positive feedback signal path to said motor means to compensate for said force provided by said spring means, said third means having a variable gain;
- fourth means for receiving said error signal and said positive feedback signal, providing a sum of said signals and applying said sum as a drive signal to said motor;
- and
- programmable digital control means coupled to vary said variable gain of said positive feedback signal path to obtain a substantially zero steady state error.
A method of providing compensation for a force of a spring utilized in a position servo system for positioning a member, wherein said spring force opposes a motion of said member from an initial position, comprising the steps of:
- detecting an actual position of said member and providing a corresponding position feedback signal;
- receiving a position request signal and said position feedback signal, and providing an error signal as a difference of said signals;
- providing a force necessary to overcome said spring force, and to move said member to a desired position in response to said error signal;
- applying a portion of said position feedback signal as a positive feedback signal compensating for said spring force;
- calibrating said positive feedback signal to obtain a substantially zero steady state error signal by varying a magnitude of said positive feedback signal and detecting a positive feedback signal value corresponding to a minimum error signal value when a known position request signal is received by said system;
- and
- summing said calibrated positive feedback signal with said error signal.
A method of providing compensation for a force of a spring utilized in a position servo system for positioning a member, wherein said spring force opposes a motion of said member from an initial position, comprising the steps of:
- detecting an actual position of said member and providing a corresponding position feedback signal;
- receiving a position request signal and said position feedback signal, and providing an error signal as a difference of said signals;
- providing a force necessary to overcome said spring force and to move said member to a desired position in response to said error signal;
- and
- calibrating a portion of said position feedback signal to compensate for said spring force and applying said calibrated signal as a positive feedback signal compensating for said spring force to obtain a substantially zero steady state error signal.
Dependencies are inferred from the claim text.