Abstract:
An actuator system having a controller, a motor, and a feedback device, wherein an output shaft of the motor is connected to the feedback device. The controller directs the application of power to the motor and the feedback device produces a signal indicative of the position of the output shaft. Advantageously, the signal may be read by the controller when the motor is not in motion.

Description:
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 first motor driver has a first motor driver output and a first motor driver input and the second motor driver has a second motor driver output and a second motor driver input. The first motor driver output is connected to the first motor control port and a second motor driver output is connected to the second motor control port. The first motor driver input is connected to the processor and the second motor driver input is connected to the processor. 
     In accordance with another aspect of the present invention, the controller further comprises a differential amplifier. The differential amplifier has a first differential input, a second differential input and a differential output. The first differential input is connected to the feedback port. The second differential input is connected to the second 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 differential output. The digital input is connected to the processor 
     In accordance with another aspect of the present invention, the digital-to-analog converter is integrated within the processor. 
     These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description of the invention in combination with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1A is a schematic of a five wire actuator, in accordance with the prior art; 
     FIG. 1B is a schematic of a three wire actuator, in accordance with the prior art; 
     FIG. 1C is a schematic of a two wire actuator, in accordance with the prior art; 
     FIG. 2 is a schematic of a controller and an actuator, in accordance with the present invention; 
     FIG. 3 is a schematic of a controller and an actuator with the potentiometer connected to the second drive contact, in accordance with the present invention; 
     FIG. 4 is a schematic of a controller and an actuator with the potentiometer connected to a grounded contact, in accordance with the present invention; 
     FIG. 5 is a schematic of a controller and an actuator with a feedback signal device, in accordance with the present invention; and 
     FIG. 6 is a schematic of a controller and an actuator, wherein the controller has a differential amplifier, in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 2, a system  49  having an actuator  50  and a controller  52  is shown, in accordance with the present invention. Actuator  50  includes a motor  54  and a potentiometer  56 . Motor  54  has an output shaft (not shown), a stator (not shown), a rotor (not shown), a first drive contact  58 , and a second drive contact  60 . Actuator  50  may be a Bühler Platform 1.61.072 actuator or similar device. Potentiometer  56  has a first potentiometer contact  62 , a second potentiometer contact  64 , a potentiometer feedback contact  66  and a wiper  67 . 
     In an embodiment of the present invention, controller  52  includes a processor  68 , a first motor driver  70 , a second motor driver  72 , an analog-to-digital converter  74 , a pull-up resistor  76 , a first motor control port  78 , a second motor control port  80 , and a feedback port  82 . Processor  68  may be a Motorola 68HC12 or similar device. First motor driver  70  and second motor driver  72  may be a Toshiba TA8083 or similar device. First motor driver  70  has a motor driver input  84  and a motor driver output  86 . Second motor driver  72  has a motor driver input  88  and a motor driver output  90 . Analog-to-digital converter  74  has an analog input  92  and a digital output  94 . 
     Generally, first motor driver  70  has a first transistor  96 , a second transistor  98 , and a transistor controller  100 . First transistor  96  and second transistor  98  are connected in series in a conventional manner. Transistor controller  100  has a first base control line  101  and a second base control line  103 . First base control line  101  is connected to a base of first transistor  96 . Second base control line  103  is connected to a base of second transistor  98 . The input of first transistor controller  100  is connected to motor driver input  84 . An output of first transistor  96  and second transistor  98  is connected to motor driver output  86 . 
     Generally, second motor driver  72  has a first transistor  102 , a second transistor  104 , and a transistor controller  106 . First transistor  102  and second transistor  104  are connected in series in a conventional manner. Transistor controller  106  has a first base control line  105  and a second base control line  107 . First base control line  105  is connected to a base of first transistor  102 . Second base control line  107  is connected to a base of second transistor  104 . The input of first transistor controller  106  is connected to motor driver input  88 . An output of first transistor  102  and second transistor  104  is connected to motor driver output  90 . 
     First potentiometer contact  62  is connected to first drive contact  58  and to first motor control port  78 . First drive contact  58  is connected to first motor control port  78 . Second potentiometer contact  64  is connected to potentiometer feedback contact  66  and to feedback port  82 . Second motor drive contact  60  is connected to second motor control port  80 . The output shaft of motor  54  is mechanically connected to wiper  67 . 
     Motor driver output  86  is connected to first motor control port  78 . Second motor driver output  90  is connected to second motor control port  80 . Pull-up resistor  76  is connected to feedback control port  82 . Analog input  92  is connected to feedback control port  82 . Motor driver input  84  is connected to processor  68 . Motor driver input  88  is connected to processor  68 . Digital output  94  is connected to processor  68 . 
     To rotate the rotor of motor  54  in a first direction, processor  68  sends a command signal instruction to first motor driver  70  and second motor driver  72  to set first transistor  96  of first motor driver  70  and second transistor  104  of second motor driver  72  in an on position and to set second transistor  98  of first motor driver  70  and first transistor  102  of second motor driver  72  in a off position. Processor  68  communicates the command signals to first motor control driver  70  through first motor driver input  84  and to second motor control driver  72  through second motor driver input  88 . First motor driver  70  provides a driving voltage to first drive contact  58  through first motor control port  78 . Second motor driver  72  provides a ground for second drive contact  60  through second motor control port  80 . 
     To rotate the rotor of motor  54  in a second direction, processor  68  sends a command signal instruction to first motor driver  70  and second motor driver  72  to set second transistor  98  of first motor driver  70  and first transistor  102  of second motor driver  72  in an on position and to set first transistor  96  of first motor driver  70  and second transistor  104  of second motor driver  72  in a off position. Processor  68  communicates the command signals to first motor control driver  70  through first motor driver input  84  and to second motor control driver  72  through second motor driver input  88 . First motor driver  70  provides a ground to first drive contact  58  through first motor control port  78 . Second motor driver  72  provides a driving voltage for second drive contact  60  through second motor control port  80 . 
     Generally, when the rotor of motor  54  rotates in the first direction or rotates in the second direction, the output shaft rotates in the same direction as the rotor of motor  54 . When the output shaft rotates, wiper  67  swipes across potentiometer  56 . Movement of wiper  67  changes an impedance of potentiometer  56 . For feedback to occur, processor  68  instructs first motor driver  70  to set second transistor  98  of first motor driver  70  in an on position. 
     When second transistor  98  of first motor driver  70  is in an on position, a current will flow through pull-up resistor  76  and through potentiometer  56 . The current flows from pull-up resistor  76  through potentiometer  56  by way of feedback port  82 . A voltage is created at feedback port  82  indicative of a position of the output shaft. The voltage is present at analog input  92 . Analog-to-digital converter  74  will convert the voltage into a digital signal indicative of the position of the output shaft. The digital signal will be outputted to digital output  94 . The digital signal will be interpreted by processor  68 . 
     Referring now to FIG. 3, a system  51  having an actuator  50 ′ and the controller  52  is shown, in accordance with the present invention. First potentiometer contact  62  is connected to second motor drive contact  60 . All other elements in this embodiment that are designated by like reference numerals are the same as the embodiment shown in FIG.  2 . In this embodiment, to rotate the rotor of motor  54  in the first direction or in the second direction is the same as in the embodiment shown in FIG.  2 . When the rotor of motor  54  rotates in the first direction or rotates in the second direction, the output shaft rotates in the same direction as motor  54 . When the output shaft rotates, the wiper swipes across potentiometer  56 . Movement of wiper  67  changes the impedance of potentiometer  56 . For feedback to occur, processor  68  instructs second motor driver  72  to set second transistor  104  in an on position. Processor  68  will communicate with the second motor control driver  72  through second motor driver input  88 . 
     When second transistor  104  of second motor driver  72  is in an on position, a current will flow through pull-up resistor  76  and through potentiometer  56 . The current will flow from pull-up resistor  76  through potentiometer  56  by way of feedback port  82 . A voltage is present at feedback port  82  indicative of the position of the output shaft. The voltage is received by analog input  92 . Analog-to-digital converter  74  will convert the voltage into a digital signal indicative of the position of the output shaft. The digital signal will be outputted to digital output  94 . The digital signal will be interpreted by processor  68 . 
     Referring now to FIG. 4, a system  53  having an actuator  50 ″ and the controller  52  is shown, in accordance with the present invention. The first potentiometer contact  62  is connected to a grounded contact  107 . All other elements having like reference numerals in this embodiment are the same as the embodiment shown in FIG.  2 . In this embodiment, to rotate the rotor of motor  54  in the first direction or in the second direction is the same as in the embodiment shown in FIG.  2 . When the rotor of motor  54  rotates in the first direction or rotates in the second direction, the output shaft rotates in the same direction as motor  54 . When the output shaft rotates, wiper  67  swipes across potentiometer  56 . Movement of wiper  67  changes the impedance of potentiometer  56 . 
     For feedback to occur, a current flows through pull-up resistor  76  and through potentiometer  56 . The current flows from pull-up resistor  76  through potentiometer  56  by way of feedback port  82 . A voltage is developed at feedback port  82  indicative of the position of the output shaft. The voltage is present at analog input  92 . Analog-to-digital converter  74  will convert the voltage into a digital signal indicative of the position of the output shaft. The digital signal will be outputted to digital output  94 . The digital signal will be interpreted by processor  68 . 
     Referring now to FIG. 5, a system  55  having an actuator  50 ′″ and the controller  52  is shown, in accordance with the present invention. A feedback signal device  108  is shown. Feedback signal device  108  has a first feedback device end  110 , a second feedback device end  112 , an output feedback device end  114  and an adjustment input (not shown). First feedback device end  110  is connected to first motor drive contact  58 . Second feedback device end  112  is connected to output feedback device end  114  and feedback port  82 . The adjustment input is mechanically connected to the output shaft of motor  54 . All other elements in this embodiment are the same as the embodiment shown in FIG.  2 . 
     In this embodiment, to rotate the rotor of motor  54  in the first direction or in the second direction is the same as in the embodiment shown in FIG.  2 . When the rotor of motor  54  rotates in the first direction or rotates in the second direction, the output shaft rotates in the same direction as the rotor in motor  54 . When the output shaft rotates, the adjustment input is altered. Movement of the adjustment input changes the impedance across feedback signal device  108 . 
     For feedback to occur, a current will flow through pull-up resistor  76  and through feedback signal device  108 . The current will be able to flow from pull-up resistor  76  through feedback signal device  108  by way of feedback port  82 . A voltage will be created at the feedback port  82  indicative of a position of the output shaft. The voltage will be inputted into analog input  92 . Analog-to-digital converter  74  will convert the voltage into a digital signal indicative of the position of the output shaft. The digital signal will be outputted to digital output  94 . The digital signal will be interpreted by processor  68 . 
     Referring now to FIG. 6, a system  57  having the actuator  50  and the controller  52  is shown, in accordance with the present invention. A differential amplifier  116 , an analog-to-digital converter  118  and a pull down resistor  120  are provided. Differential amplifier  116  has a first differential input  122 , a second differential input  124 , and a differential output  126 . Analog-to-digital converter  118  has a second analog input  128  and a second digital output  130 . 
     First differential input  122  is connected to feedback port  82 . Second differential input is connected to first motor control port  78 . Differential output  126  is connected to second analog input  128 . Second digital output  130  is connected to processor  68 . Pull down resistor  120  is connected to first motor control port  78 . All other elements in this embodiment are the same as the embodiment shown in FIG.  2 . 
     In this embodiment, to rotate the rotor of the motor  54  in the first direction or in the second direction is the same as in the embodiment shown in FIG.  2 . When the rotor of motor  54  rotates in the first direction or rotates in the second direction, the output shaft rotates in the same direction as motor  54 . When the output shaft rotates, wiper  67  swipes over potentiometer  56 . Movement of wiper  67  across potentiometer  56  changes the impedance of potentiometer  56 . 
     For feedback to occur, current flows through pull-up resistor  76 , potentiometer  56 , and pull down resistor  120 . The current flows from pull-up resistor  76  through potentiometer  56  and pull down resistor  120  by way of feedback port  82  and first motor control port  78 . A first voltage is created at feedback port  82  and a second voltage is developed at first motor control port  78 . Differential amplifier  116  will take the difference of the first voltage and the second voltage and output a difference voltage to differential output  126 . The difference voltage is indicative of the position of the output shaft. Analog-to-digital converter  118  receives the difference voltage through second analog input  128 . Analog-to-digital converter  118  outputs a digital signal indicative of the position of the output shaft to second digital output  130 . Finally, the digital signal is interpreted by processor  68  to determine the location of the output shaft of motor  54 . 
     As any person skilled in the art of actuators will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.