US 4,263,537 A · Controlled positioning of a motor shaft

Abstract

A method for positioning the shaft of a motor which can be subject to a rotation force in either direction of rotation by application of drive current of a respective polarity, in order to bring the shaft to a target angular position by the action of a digital control and a position sensor associated with the motor shaft for emitting a displacement step signal in response to each movement of the the shaft through an incremental angle constituting a given fraction of one cycle of shaft rotation, which includes giving the displacement step signal the form of a signal cycle of sinus-like waveform in response to each incremental angle of shaft movement, deriving from the displacement step signal a shaft movement signal having a value represented by the sum of a component proportional to the displacement step signal and a component proportional to the time derivative thereof, and, after the motor shaft has reached a defined angular speed and at the moment when the shaft position is spaced from the target position by one-half of the incremental angle, initiating a control signal having a value which decreases with time, comparing the shaft movement signal with the control signal, and varying the polarity of motor drive current in dependence on the polarity of the comparison result.

Claims17

Dependent claims

In a method for positioning the shaft of a motor which can be subject to a rotation force in either direction of rotation by application of drive current of a respective polarity, in order to bring the shaft to a target angular position by the action of a digital control and a position sensor associated with the motor shaft for emitting a displacement step signal in response to each movement of the shaft through an incremental angle constituting a given fraction of one cycle of shaft rotation, which method includes comprising a signal derived from such step signal with a control signal and utilizing the result of the comparison to control the motor drive current, the improvement wherein:

the displacement step signal produced by said sensor in response to each incremental angle of shaft movement is a signal cycle of sinus-like waveform;
said method comprises deriving from the displacement step signal a shaft movement signal having a value represented by the sum of a component proportional to the displacement step signal and a component proportional to the time derivative thereof for the last half of the associated step signal cycle, and, after the shaft has reached a predetermined angular speed and at the moment when the shaft reaches a position spaced from the target position by one-half of the incremental angle, causing the control signal to have a value which decreases with time;
said step of comparing comprises comparing the shaft movement signal with the control signal;
and said step of utilizing the comparison result comprises varying the polarity of motor drive current in dependence on the polarity of the comparison result.

1 more element

A circuit for controlling the position of the shaft of a motor which can be subject to a rotation force in either direction of rotation by application of drive current of a respective polarity, by bringing the shaft to a target angular, comprising:

a position sensor responsive to rotation of the motor shaft for producing a displacement step signal in the form of a cycle of sinus-like waveform in response to each movement of the shaft through an incremental angle constituting a given fraction of one cycle of shaft rotation;
control means connected to receive the signal produced by said sensor for monitoring the path traversed by, and the angular speed of, the motor shaft;
a control switch connected between the motor and said control means to operate under control of said control means for controlling the delivery of drive current to the motor;
a signal shaping member connected to said sensor for providing a shaft movement signal formed by the sum of a component proportional to the displacement step signal and a component proportional to the time derivative thereof;
a control signal generator connected to said control means for providing, in response to signals from said control means, a control signal having a value which decreases with time;
comparison means connected to receive the shaft movement signal and the control signal for producing a comparison signal dependent on the polarity of the difference between the two signals which it receives;
and means for initiating the control signal and supplying the resulting comparison signal from said comparison means to said control switch for controlling the polarity of drive current applied to the motor as a function of the comparison signal when the motor shaft reaches a predetermined angular speed and an angular position within the incremental angle from the target position.

4 more elements

Dependencies are inferred from the claim text.

Controlled positioning of a motor shaft

Life of this patent

Controlled positioning of a motor shaft

Life of this patent

Abstract

Claims17