US 5,132,602 A · Actuator positioning apparatus

Abstract

A method and apparatus for accurately and reliably positioning an actuator arm (12) is disclosed. The actuator arm (12) is driven by a conventional DC motor (38). The conductors which supply current to the motor (38) serve as primary windings (60) of a current transformer (58). The signal induced on secondary windings (62) of the transformer (58) responds to fluctuations in average current flowing in the motor (38). These fluctuations are amplified (64) and filtered (66) so that an AC burst (68) is produced in response to each commutation of the motor (38). The AC burst (68) triggers a one-shot timing circuit (72), which generates a pulse that remains active until the AC burst (68) has decayed. The pulse disappears prior to a subsequent commutation of the motor (38). Thus, one pulse is generated for each commutation of motor (38). A counter (76) is clocked by these pulses. The counter (76) increments when the motor (38) moves in one direction and decrements when the motor (38) moves in the opposing direction. Thus, the counter (76) maintains a current count which describes the position of the motor (38). A controller (16) compares this current count with an input signal (14) and controls the operation of the motor (38) based on the results of the comparison. Accordingly, the motor (38) moves until the current count reaches a value corresponding to information presented in the input signal (14).

Claims20

Dependent claims

A method of operating a CD motor to position a member, said method comprising the steps of:

receiving a position signal defining a desired position for said member;
applying a DC voltage to said motor, said applying step causing a current to flow through said motor;
sensing fluctuations in said current, said fluctuations being caused by commutations of said motor;
activating pulses in response to said current fluctuations;
for each of said activated pulses, deactivating said pulse a predetermined duration after said pulse is activated, said predetermined duration being determined independently from said current fluctuations;
counting said pulses to maintain a current count;
comparing said current count with said position signal;
and
removing said CD voltage from said motor when said comparing step indicates that said member has substantially reached said desired position.

6 more elements

An actuating apparatus for causing a member to move to a desired position, said apparatus comprising:

means, having a control input, for selectively applying a DC voltage in response to a signal presented at said control input;
a DC motor physically coupled to said member and electrically coupled to said selectively applying means so that commutations of said motor occur and a current flows through said motor while said DC voltage is applied;
means, coupled to said motor, for sensing fluctuations in said current and producing a representative signal corresponding to said fluctuations in said current;
a pulse generator having an input coupled to said sensing means and having an output, said pulse generator being configured to produce a pulse for each commutation of said motor, each pulse beginning when said representative signal exceeds a predetermined threshold and continuing for a predetermined duration, said predetermined duration being determined independently from said representative signal;
means, coupled to said pulse generator, for counting said pulses to obtain a current count;
and
feedback means, coupled to said counting means and to said control input of said voltage applying means, for controlling application of said DC voltage in response to said current count.

4 more elements

An actuating apparatus for fusing a member to move to a desired position, said apparatus comprising:

means, having a control input, for selectively applying a DC voltage in response to a signal presented at said control input;
a DC motor physically coupled to said member and electrically coupled to said selectively applying means so that a current flows through said motor while said DC voltage is applied and so that said current fluctuates as a result of motor commutations;
a transformer having a primary winding coupled in series between said motor and said voltage applying means and having a secondary winding, said primary and secondary windings being wound around a toroid core;
a counter, coupled to said secondary winding, for counting commutations of said motor to obtain a current count;
and
feedback means, coupled to said counter and to said control input of said voltage applying means, for controlling application of said CD voltage in response to said current count.

3 more elements

Dependencies are inferred from the claim text.

Actuator positioning apparatus

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Actuator positioning apparatus

Life of this patent

Abstract

Claims20