Electricity: motive power systems – Positional servo systems – With particular 'error-detecting' means
Reexamination Certificate
2002-08-21
2003-04-08
Leykin, Rita (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular 'error-detecting' means
C318S560000, C318S671000
Reexamination Certificate
active
06545441
ABSTRACT:
TECHNICAL FIELD
This invention relates to actuator systems of the type having a motor and a feedback device when the feedback device is connected to an output shaft of the motor.
BACKGROUND
Actuator systems are used for driving a driven member in a wide variety of applications. By way of example, actuators are used in automotive climate controls to adjust the various air duct doors. Further, these doors are used to blend heated, cooled or ambient air according to a selected temperature setting and to direct the air to the selected vents.
Actuators are generally part of a control system that accepts instructions from a user and directs the movement of the actuators according to those instructions. The control system often needs to have information regarding the current position of the output shaft of the motor. The position of the output shaft is provided by the feedback device. The feedback device may be a potentiometer having a wiper that is mechanically coupled and driven by the output shaft of the motor.
As shown in
FIG. 1A
, earlier prior art solutions utilized a five-wire actuator system. Typical applications have a processor (not shown), two motor drivers (not shown) and an analog-to-digital converter (not shown). A motor
10
is connected to the two drivers through a first port
12
and a fifth port
20
. It will be understood that the motor has an output shaft connected to the device to be driven. The output shaft also carries a wiper
22
of a potentiometer
24
. Wiper
22
is connected to the analog-to-digital converter through a third port
16
. A power supply (not shown) is connected to one side of potentiometer
24
through a second port
14
while the other side is grounded through a fourth port
18
. A motor power supply (not shown) is connected to the two motor drivers.
In this system, five wires are needed to connect motor
10
and potentiometer
24
to first port
12
, second port
14
, third port
16
, fourth port
18
, and fifth port
20
. The output voltage of third port
16
is proportional to a position of the output shaft. Note that potentiometer
24
requires a potentiometer power supply (not shown), separate from the power supply. The potentiometer power supply and its associated wiring add cost and complexity to the system. The three-wire and four-wire systems of the present invention have been developed to minimize these costs.
While the device of U.S. Pat. No. 5,389,864 issued to Tryan et al, achieves its intended purpose of eliminating the potentiometer power supply, significant disadvantages still exist. As shown in
FIG. 1B
, the actuator system consists of a first port
26
, a second port
28
, a third port
30
, a motor
32
, and a potentiometer
34
. First port
26
and third port
30
connect a power supply (not shown) to motor
32
and potentiometer
34
. Second port
28
is connected to an analog-to-digital converter (not shown) with the purpose of providing a voltage indicative of the position of the output shaft, The disadvantages of this system are that second port
28
will only provide voltage indicative of the position of the output shaft when motor
32
is powered by the power supply. To solve this problem, a short pulse must be produced by the power supply long enough to produce a voltage indicative of position of the output shaft, but short enough not to move motor
32
, which may cause an error in the voltage indicative of the position of the output shaft. Last, complex software must be developed to differentiate which direction motor
32
is moving to correctly interpret the voltage indicative of the position of the output shaft.
Furthermore, in the device disclosed in U.S. Pat. No. 5,744,925 issued to Madsen, achieves its intended purpose of eliminating the potentiometer power supply, however significant disadvantages still exist. As shown in
FIG. 1C
, the actuator system consists of a first port
36
, a second port
38
, a motor
40
, a potentiometer
42
, a resistor
44
, a first zener diode
46
, and a second zener diode
48
. Potentiometer
42
and resistor
44
are connected in series across first port
36
and second port
38
and will produce a voltage indicative of the position of the output shaft when a current passes through potentiometer
42
and resistor
44
. Motor
40
, first zener diode
46
and second zener diode
48
are connected in series across first port
36
and second port
38
. More specifically, first zener diode
46
and second zener diode
48
are connected in a back-to-back configuration. The back-to-back configuration will only allow a flow of current through motor
40
when the voltage across first port
36
and second port
38
reaches a threshold voltage. A voltage reading can be taken across potentiometer
42
and resistor
44
without moving the motor when the voltage across first port
36
and second port
38
is below the threshold voltage. The disadvantages of this system are that a voltage reading across potentiometer
42
and resistor
44
can only be taken when the voltage across first port
36
and second port
38
are below the threshold voltage. Next, motor
40
will need to be a larger motor due to a greater voltage required to exceed the threshold voltage. Last, first zener diode
46
and second zener diode
48
are components that are not commonly found on an actuator and would increase manufacturing costs.
Therefore, there is a need for a new and improved device that allows a reading of the position of the output shaft without requiring the motor to move, does not require a larger, more costly motor, and does not require any components not commonly found on an actuator. At the same time, the device should be less costly than devices currently used.
SUMMARY
In an aspect of the present invention, an actuator and controller is provided. The actuator has a motor and a potentiometer. The motor has an output shaft, a first drive contact and a second drive contact. The potentiometer has a first potentiometer contact, a second potentiometer contact and a potentiometer feedback contact. The first potentiometer contact is connected to one of the first drive contact, the second drive contact and a grounded contact, the second potentiometer contact is connected to the potentiometer feedback contact, thereby producing a feedback signal indicative of a position of the output shaft. The controller has a feedback port, a first motor control port, and a second motor control port. The feedback port is connected to the second potentiometer contact and the potentiometer feedback contact. The first motor control port is connected to the first drive contact and the second motor control port is connected to the second drive contact.
In accordance with another aspect of the present invention, the feedback signal is indicative of an electrical impedance.
In accordance with another aspect of the present invention, the first potentiometer contact is connected to the first drive contact.
In accordance with another aspect of the present invention, the first potentiometer contact is connected to the second drive contact.
In accordance with another aspect of the present invention, the first potentiometer contact is connected to the grounded contact.
In accordance with another aspect of the present invention, the controller further comprises a pull-up resistor connected to the feedback port.
In accordance with another aspect of the present invention, the controller further comprises a pull-down resistor connected to the first motor control port.
In accordance with another aspect of the present invention, the controller further comprises an analog-to-digital converter. The analog-to-digital converter has an analog input and a digital output. The analog input is connected to the feedback port. The digital output is connected to the processor.
In accordance with another aspect of the present invention, the digital-to-analog converter is integrated within the processor.
In accordance with another aspect of the present invention, the controller further comprises a first motor driver and a second motor driver. The f
Brinks Hofer Gilson & Lione
Leykin Rita
Visteon Global Technologies Inc.
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