Abstract:
A motor control system includes a piston chamber and a piston assembly disposed within the piston chamber to move therein between first and second positions. A magnet is coupled to the piston assembly to move therewith and a sensor is axially mounted with respect to the piston assembly to generate a continuous output signal corresponding to a position of the magnet relative to the sensor. The motor control system also includes a controller for processing the output signal from the sensor to monitor continuously the position of the piston assembly within the piston chamber and for actuating the piston assembly to move in an upstroke toward the first position and in a downstroke toward the second position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is directed to a motor control and, more specifically, to a motor control that is configured to track the position of a piston in a motor. 
         [0003]    2. Background of the Invention 
         [0004]    Motors that include a piston actuated or energized to move within a piston chamber to perform mechanical work are known. Further, control systems for controlling the actuation of the piston within the piston chamber are known. In one example, a photoelectronic sensor is configured to generate a signal when the piston reaches one end of the piston chamber. In the present example, the signal generated by the photoelectronic sensor is a digital signal that provides only discrete, discontinuous position data when the piston has reached the end of the piston chamber. 
         [0005]    In another example, a magnetic hall sensor is disposed on a circumferential wall that defines the piston chamber and a magnet is coupled to the piston. In the present example, the hall sensor functions similarly to the example above, wherein the hall sensor generates a discrete signal when the magnet passes by the hall sensor to determine an instantaneous position of the piston as it passes by the hall sensor. For some applications, such discrete data is sufficient for satisfactory control the motor. 
         [0006]    However, other applications require or at least could be benefitted by greater precision and reliability in controlling the actuation of the piston within the piston chamber. In such applications, improved tracking of the piston is one consideration to facilitate the greater precision and reliability in controlling the actuation of the piston. The present disclosure is directed to such a control with improved tracking of a piston. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one example, a motor control system includes a piston chamber and a piston assembly disposed within the piston chamber to move therein between first and second positions. A magnet is coupled to the piston assembly to move therewith and a sensor is axially mounted with respect to the piston assembly to generate a continuous output signal corresponding to a position of the magnet relative to the sensor. The motor control system also includes a controller for processing the output signal from the sensor to monitor continuously the position of the piston assembly within the piston chamber and for actuating the piston assembly to move in an upstroke toward the first position and in a downstroke toward the second position. 
         [0008]    According to another example, a motor control system includes an end cap housing for mounting on an axial end of a piston chamber and a sensor coupled to the housing. The sensor is configured to generate a continuous output signal corresponding to a position of a piston assembly within the piston chamber. Further, a controller is coupled to the sensor for processing the output signal from the sensor and monitoring continuously the position of the piston assembly. 
         [0009]    According to a further example, a motor control system includes a piston chamber, a piston assembly disposed within the piston chamber to move therein between first and second positions, and a sensor axially mounted with respect to the piston assembly to generate an output signal corresponding to a position of piston assembly relative to the sensor. The system also includes a controller for processing the output signal from the sensor to monitor the position and velocity of the piston assembly as the piston assembly is moved between the first and second positions and for actuating the piston assembly to move in an upstroke toward the first position and in a downstroke toward the second position. 
         [0010]    These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Details of the present invention, including non-limiting benefits and advantages, will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein: 
           [0012]      FIG. 1  is a diagrammatic, side elevational, and partially cross-sectional view of a motor assembly according to one embodiment; 
           [0013]      FIG. 2  is a flowchart illustrating a procedure performed to calibrate the motor assembly of  FIG. 1 ; and 
           [0014]      FIG. 3  is a flowchart illustrating a normal operating mode of the motor assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described one or more embodiments with the understanding that the present disclosure is to be considered illustrative only and is not intended to limit the invention to any specific embodiment disclosed herein. 
         [0016]      FIG. 1  illustrates a motor assembly  10  that includes a piston chamber  12  defined by a circumferential sidewall  14  having first and second opposing ends  16 ,  18 , respectively. A piston assembly  20  is disposed within the piston chamber  12  and is energized or actuated within the piston chamber to move therein. In one example, the piston chamber  12  is substantially cylindrical and the piston assembly  20  is configured to move axially within the chamber. The piston assembly  20  includes a piston head  22  coupled to a pump shaft  24 . The first end  16  of the piston chamber  12  is sealed by an end cap housing  26  that can be configured to provide an easily maintained and replaced single housing for all of the control components of the motor assembly  10 , as is shown in  FIG. 1  and as will be described in more detail hereinafter. The second end  18  of the piston chamber is sealed by an end wall  28 . An opening  30  in the end wall  28  allows the pump shaft  24  to extend therethrough so that the pump shaft can be coupled to a separate system  32  to perform work thereon. In one example intended without limitation, the separate system  32  can be an adhesive dispensing system and the pump shaft  24  can be coupled thereto to precisely meter and dispense adhesive from the system  32 . A seal (not shown) may be disposed between the opening  30  in the end wall  28  and the pump shaft  24  to provide a substantially fluid-tight seal, as would be apparent to one of ordinary skill. 
         [0017]    The end cap housing  26  includes a fluid port  34  for coupling to a fluid supply. In the present embodiment, the fluid port  34  functions as a fluid inlet designated generally by the arrow  36 . The end cap housing  26  also includes an exhaust outlet port  38 . According to one non-limiting example, the fluid port  34  can be coupled to a supply of pressurized air. In other examples, the fluid port  34  may be coupled to a supply of other suitable fluids, such as oil, water, and the like. The end cap housing  26  also includes a valve mechanism  40  fluidly coupled to the port  34  for directing a fluid flow to actuate and move the piston assembly  20  within the chamber  12  and to the exhaust outlet  38  to allow fluid to exit the chamber, as will be described in more detail hereinafter. The valve mechanism  40  may include one or more electrically actuated valves. In one example, the valve mechanism  40  includes one or more single or multi-port solenoid valves, such as one or more three-way and four-way solenoid valves, as would be apparent to one of ordinary skill in the art. 
         [0018]    The circumferential sidewall  14  includes a first duct  42  and a second duct  44 . The first duct  42  includes a first inlet  46  coupled to the valve  40  and a first outlet  48  into the piston chamber  12  at a point generally proximate the first end  16  of the piston chamber. The second duct  44  includes a second inlet  50  coupled to the valve  40  and a second outlet  52  into the piston chamber  12  at a point generally proximate the second end  18  of the piston chamber. 
         [0019]    The end cap  26  housing also includes a printed circuit board (“PCB”)  54  that controls the valve  40  to direct a flow of fluid, such as pressurized air, to drive the piston assembly  20  in a downstroke toward the second end  18  of the piston chamber  12  and in an upstroke toward the first end  16  of the piston chamber. More particularly, during the downstroke, the valve  40  opens a fluid flow path represented by an arrow  56  between the port  34  and the first inlet  46  of the first duct  42  to allow the fluid to flow out through the first outlet  48  into the piston chamber  12  and drive the piston assembly  20  toward the second end  18 . During the downstroke, the valve  40  may also open a fluid flow path represented by an arrow  58  between the second duct  44  and the exhaust outlet  38  to allow fluid to exit the chamber  12  as the piston assembly is moved toward the second end  18 . Similarly, during the upstroke, the valve  40  opens a fluid flow path represented by an arrow  60  between the port  34  and the second inlet  50  of the second duct  44  to allow the fluid to flow out through the second outlet  52  into the piston chamber  12  and drive the piston assembly  20  toward the first end  16 . During the upstroke, the valve  40  may also open a fluid flow path represented by an arrow  62  between the first duct  42  and the exhaust outlet  38  to allow fluid to exit the chamber  12  as the piston assembly is moved toward the first end  16 . 
         [0020]    An electrical connection  64  may also be disposed on the end cap housing  26  for supplying electrical power to the PCB  54 , the valve  40 , and/or any other electrical or electromechanical components of the motor assembly  10 . 
         [0021]    The motor assembly  10  further includes a sensor  66 , such as a hall sensor, capable of generating a continuous, analog signal corresponding to a position of a magnet  68  disposed on the piston assembly  20 . The magnet  68  may be ring-shaped, disk-shaped, or any other appropriate shape and is disposed on the piston assembly  20  in any known manner, such as by adhesive, screws, clamps, an interference fit, etc. In  FIG. 1 , the sensor  66  is coupled to the end cap housing  26  and is disposed axially in relation to the movement of the piston assembly  20  within the piston chamber  12 . The sensor  66  is further coupled to the PCB  54 , which processes signals from the sensor to track continuously the position of the magnet  68  and the piston assembly  20  within the piston chamber  12 . The placement of the sensor  66  at an axial end of the chamber  12  facilitates the continuous tracking of the magnet  68  and piston assembly  20 . 
         [0022]    Referring now to  FIG. 2 , the PCB  54  and/or some other control system may perform a calibration mode or procedure  80  to collect relevant data before, during, and/or after the motor assembly  10  is utilized in a given application. The calibration procedure  80  begins at a block  82 , whereby the piston assembly  20  is energized or actuated to move in an upstroke towards the first end  16  of the piston chamber  12 , as described above. The piston assembly  20  is moved in the upstroke until the piston head  22  stops at a block  84 . In one example, the piston head  22  is mechanically stopped at the block  84 , such as when the piston head reaches the end of the chamber  12 . Thereafter, at a block  86 , the PCB  54  collects and stores data, such as the position of the piston assembly  20  when it is stopped at the block  84 . Position data collected at the block  86  may correspond to an upper limitation of the piston head  20  within the piston chamber  12 . 
         [0023]    After the block  86 , control passes to a block  88 , and the piston assembly  20  is energized to move in a downstroke towards the second end  18  of the piston chamber  12 , as described above. The piston assembly  20  is moved in the downstroke until the piston head  22  stops at a block  90 . Similarly to the block  84 , the piston head can be mechanically stopped at the block  90 , such as by reaching the end of the chamber  12 . Thereafter, at a block  92 , the PCB  54  collects and stores data, such as the position of the piston assembly  20  when it is stopped at the block  90 . The position data collected at the block  92  may correspond to a lower limitation of the piston head  20  within the piston chamber  12 . 
         [0024]    Various modifications can be made to the calibration procedure  80  of  FIG. 2  without departing from the spirit of the present disclosure. For example, the blocks  82 ,  88  may be performed in any order to collect data regarding the upper and lower limitations. Further, data can be collected continuously as the piston assembly  20  is moved between the upper and lower limitations and the collected data may include the position, velocity, acceleration, and other parameters of the motor assembly  10  in use. 
         [0025]      FIG. 3  illustrates one example of a normal operating mode or procedure  100  during which the piston assembly  20  is energized or actuated to cause the piston assembly to travel between the upper and lower limitations. More particularly, the piston assembly  20  is energized to move in an upstroke at a block  102  until the piston assembly  20  is stopped at a block  104 . In one example, the PCB  54  stops the piston assembly  20  at the block  104  utilizing the calibration data, instead of a mechanical stop similar to the blocks  84  and  90 . After the block  104 , the piston assembly is energized to move in a downstroke at a block  106  until the piston assembly is stopped at a block  108 . Similarly to the block  104 , the PCB  54  can stop the piston assembly at the block  108  utilizing the calibration data, instead of a mechanical stop. After the block  108 , control passes back to the block  102  and the process of driving the piston assembly  20  within the piston chamber  12  is repeated. The blocks  104 ,  108  utilize the calibration data, such as the positions of the piston assembly  20  at the upper and lower limitations, and may stop the piston assembly  20  at any position within the piston chamber  12 , such as at the upper and lower limitations or anywhere therebetween. In one embodiment, the blocks  102 - 108  energize the piston assembly  20  to travel between the upper and lower limitations minus a small margin to compensate for tolerances and drifts of the motor assembly  10 . Further, the blocks  104 ,  108  may stop the piston assembly  20  instantaneously as the piston assembly is transitioned between the upstroke and downstroke or may stop the piston assembly for a longer period of time. 
         [0026]    During the actuation of the piston assembly  20  to move within the chamber  12  at the blocks  102 - 108 , the sensor  66  can continuously generate position data for the magnet  68  and the piston assembly  20 . The PCB  54  can use this continuous position data to accurately control actuation of the piston assembly  20  and operation of the motor assembly  10 . Further, the continuous tracking of the position of the piston assembly  20  allows the PCB  54  to determine a velocity and acceleration thereof as the assembly moves within the piston chamber  12 . The velocity and/or acceleration data can be used to check the proper operation of the valve mechanism  40  that directs fluid flow through the first and second ducts  42 ,  44 . For example, a direction of quick stroking based on the velocity and/or acceleration data may indicate one or more fluid flow paths being stuck open. 
         [0027]    The PCB  54  can also use the position data to log strokes or cycles of the piston assembly  20  and provide maintenance reminders and stroke/cycle limiting functions for portions of the motor assembly  10  or the separate system  32 . Further, the PCB  54  can use the position data to adjust a stroke length and/or timing of the piston assembly  20  within the piston chamber  12  in applications, such as, but not limited to adhesive pattern control. Another potential benefit is the ability to precisely detect and correct for stalling of the piston assembly  20  mid stroke. Still further, the position data can be used to calculate a flow rate and consumption of a substance, such as an adhesive. Another possible benefit or application is to tie the position data with a melt rate of the adhesive or glue and to control the piston speed and strokes per minute accordingly. 
         [0028]    The PCB  54  can also control the valve  40  to direct a fluid flow, such as pressurized air, through the first and second ducts  42 ,  44  simultaneously. In one example, the block  104  controls the transition between the upstroke (block  102 ) and the downstroke (block  106 ). During the block  104 , the PCB  54  can control the valve  40  to begin opening the fluid flow path  56  so that fluid begins to flow into the piston chamber  12  from the first end  16  even as fluid is flowing through the second duct  44  to drive the piston assembly  20  upward. As the piston assembly  20  nears the stop position of the block  104 , the PCB  54  can control the valve  40  to continue opening the fluid flow path  56  as the valve closes the fluid flow path  60  between the port  34  and the second duct  44 . This control of fluid through both the first and second ducts  42 ,  44  helps provide a smooth transition between upstrokes and downstrokes and helps compensate for switching times between upstrokes and downstrokes. 
         [0029]    Likewise, the block  106  controls the transition between the downstroke (block  106 ) and the upstroke (block  102 ). During the block  106 , the PCB  54  can control the valve  40  to begin opening the fluid flow path  60  so that fluid begins to flow into the piston chamber  12  from the second end  18  even as fluid is flowing through the first duct  42  to drive the piston assembly  20  downward. As the piston assembly  20  nears the stop position of the block  108 , the PCB  54  can control the valve  40  to continue opening the fluid flow path  60  as the valve closes the fluid flow path  56  between the port  34  and the first duct  42 . 
         [0030]    Other embodiments include all of the various combinations of individual features of each of the embodiments and examples described and/or claimed herein. 
         [0031]    In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
       INDUSTRIAL APPLICABILITY 
       [0032]    The motor control disclosed herein is configured to track accurately and continuously a position of a piston within a motor to provide greater precision and reliability in controlling the actuation of the piston. According to one example, the motor control can be used in an adhesive dispensing system to precisely meter and dispense the adhesive 
         [0033]    Numerous modifications to the present disclosure will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the invention and to teach the best mode of carrying out same. The exclusive rights to all modifications which come within the scope of the appended claims are reserved.