Motor control

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.

BACKGROUND OF THE INVENTION

1. Field of the Invention

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.

2. Background of the Invention

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.

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.

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

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.

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.

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.

DETAILED DESCRIPTION

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.

FIG. 1illustrates a motor assembly10that includes a piston chamber12defined by a circumferential sidewall14having first and second opposing ends16,18, respectively. A piston assembly20is disposed within the piston chamber12and is energized or actuated within the piston chamber to move therein. In one example, the piston chamber12is substantially cylindrical and the piston assembly20is configured to move axially within the chamber. The piston assembly20includes a piston head22coupled to a pump shaft24. The first end16of the piston chamber12is sealed by an end cap housing26that can be configured to provide an easily maintained and replaced single housing for all of the control components of the motor assembly10, as is shown inFIG. 1and as will be described in more detail hereinafter. The second end18of the piston chamber is sealed by an end wall28. An opening30in the end wall28allows the pump shaft24to extend therethrough so that the pump shaft can be coupled to a separate system32to perform work thereon. In one example intended without limitation, the separate system32can be an adhesive dispensing system and the pump shaft24can be coupled thereto to precisely meter and dispense adhesive from the system32. A seal (not shown) may be disposed between the opening30in the end wall28and the pump shaft24to provide a substantially fluid-tight seal, as would be apparent to one of ordinary skill.

The end cap housing26includes a fluid port34for coupling to a fluid supply. In the present embodiment, the fluid port34functions as a fluid inlet designated generally by the arrow36. The end cap housing26also includes an exhaust outlet port38. According to one non-limiting example, the fluid port34can be coupled to a supply of pressurized air. In other examples, the fluid port34may be coupled to a supply of other suitable fluids, such as oil, water, and the like. The end cap housing26also includes a valve mechanism40fluidly coupled to the port34for directing a fluid flow to actuate and move the piston assembly20within the chamber12and to the exhaust outlet38to allow fluid to exit the chamber, as will be described in more detail hereinafter. The valve mechanism40may include one or more electrically actuated valves. In one example, the valve mechanism40includes 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.

The circumferential sidewall14includes a first duct42and a second duct44. The first duct42includes a first inlet46coupled to the valve40and a first outlet48into the piston chamber12at a point generally proximate the first end16of the piston chamber. The second duct44includes a second inlet50coupled to the valve40and a second outlet52into the piston chamber12at a point generally proximate the second end18of the piston chamber.

The end cap26housing also includes a printed circuit board (“PCB”)54that controls the valve40to direct a flow of fluid, such as pressurized air, to drive the piston assembly20in a downstroke toward the second end18of the piston chamber12and in an upstroke toward the first end16of the piston chamber. More particularly, during the downstroke, the valve40opens a fluid flow path represented by an arrow56between the port34and the first inlet46of the first duct42to allow the fluid to flow out through the first outlet48into the piston chamber12and drive the piston assembly20toward the second end18. During the downstroke, the valve40may also open a fluid flow path represented by an arrow58between the second duct44and the exhaust outlet38to allow fluid to exit the chamber12as the piston assembly is moved toward the second end18. Similarly, during the upstroke, the valve40opens a fluid flow path represented by an arrow60between the port34and the second inlet50of the second duct44to allow the fluid to flow out through the second outlet52into the piston chamber12and drive the piston assembly20toward the first end16. During the upstroke, the valve40may also open a fluid flow path represented by an arrow62between the first duct42and the exhaust outlet38to allow fluid to exit the chamber12as the piston assembly is moved toward the first end16.

An electrical connection64may also be disposed on the end cap housing26for supplying electrical power to the PCB54, the valve40, and/or any other electrical or electromechanical components of the motor assembly10.

The motor assembly10further includes a sensor66, such as a hall sensor, capable of generating a continuous, analog signal corresponding to a position of a magnet68disposed on the piston assembly20. The magnet68may be ring-shaped, disk-shaped, or any other appropriate shape and is disposed on the piston assembly20in any known manner, such as by adhesive, screws, clamps, an interference fit, etc. InFIG. 1, the sensor66is coupled to the end cap housing26and is disposed axially in relation to the movement of the piston assembly20within the piston chamber12. The sensor66is further coupled to the PCB54, which processes signals from the sensor to track continuously the position of the magnet68and the piston assembly20within the piston chamber12. The placement of the sensor66at an axial end of the chamber12facilitates the continuous tracking of the magnet68and piston assembly20.

Referring now toFIG. 2, the PCB54and/or some other control system may perform a calibration mode or procedure80to collect relevant data before, during, and/or after the motor assembly10is utilized in a given application. The calibration procedure80begins at a block82, whereby the piston assembly20is energized or actuated to move in an upstroke towards the first end16of the piston chamber12, as described above. The piston assembly20is moved in the upstroke until the piston head22stops at a block84. In one example, the piston head22is mechanically stopped at the block84, such as when the piston head reaches the end of the chamber12. Thereafter, at a block86, the PCB54collects and stores data, such as the position of the piston assembly20when it is stopped at the block84. Position data collected at the block86may correspond to an upper limitation of the piston head20within the piston chamber12.

After the block86, control passes to a block88, and the piston assembly20is energized to move in a downstroke towards the second end18of the piston chamber12, as described above. The piston assembly20is moved in the downstroke until the piston head22stops at a block90. Similarly to the block84, the piston head can be mechanically stopped at the block90, such as by reaching the end of the chamber12. Thereafter, at a block92, the PCB54collects and stores data, such as the position of the piston assembly20when it is stopped at the block90. The position data collected at the block92may correspond to a lower limitation of the piston head20within the piston chamber12.

Various modifications can be made to the calibration procedure80ofFIG. 2without departing from the spirit of the present disclosure. For example, the blocks82,88may be performed in any order to collect data regarding the upper and lower limitations. Further, data can be collected continuously as the piston assembly20is moved between the upper and lower limitations and the collected data may include the position, velocity, acceleration, and other parameters of the motor assembly10in use.

FIG. 3illustrates one example of a normal operating mode or procedure100during which the piston assembly20is energized or actuated to cause the piston assembly to travel between the upper and lower limitations. More particularly, the piston assembly20is energized to move in an upstroke at a block102until the piston assembly20is stopped at a block104. In one example, the PCB54stops the piston assembly20at the block104utilizing the calibration data, instead of a mechanical stop similar to the blocks84and90. After the block104, the piston assembly is energized to move in a downstroke at a block106until the piston assembly is stopped at a block108. Similarly to the block104, the PCB54can stop the piston assembly at the block108utilizing the calibration data, instead of a mechanical stop. After the block108, control passes back to the block102and the process of driving the piston assembly20within the piston chamber12is repeated. The blocks104,108utilize the calibration data, such as the positions of the piston assembly20at the upper and lower limitations, and may stop the piston assembly20at any position within the piston chamber12, such as at the upper and lower limitations or anywhere therebetween. In one embodiment, the blocks102-108energize the piston assembly20to travel between the upper and lower limitations minus a small margin to compensate for tolerances and drifts of the motor assembly10. Further, the blocks104,108may stop the piston assembly20instantaneously as the piston assembly is transitioned between the upstroke and downstroke or may stop the piston assembly for a longer period of time.

During the actuation of the piston assembly20to move within the chamber12at the blocks102-108, the sensor66can continuously generate position data for the magnet68and the piston assembly20. The PCB54can use this continuous position data to accurately control actuation of the piston assembly20and operation of the motor assembly10. Further, the continuous tracking of the position of the piston assembly20allows the PCB54to determine a velocity and acceleration thereof as the assembly moves within the piston chamber12. The velocity and/or acceleration data can be used to check the proper operation of the valve mechanism40that directs fluid flow through the first and second ducts42,44. 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.

The PCB54can also use the position data to log strokes or cycles of the piston assembly20and provide maintenance reminders and stroke/cycle limiting functions for portions of the motor assembly10or the separate system32. Further, the PCB54can use the position data to adjust a stroke length and/or timing of the piston assembly20within the piston chamber12in 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 assembly20mid 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.

The PCB54can also control the valve40to direct a fluid flow, such as pressurized air, through the first and second ducts42,44simultaneously. In one example, the block104controls the transition between the upstroke (block102) and the downstroke (block106). During the block104, the PCB54can control the valve40to begin opening the fluid flow path56so that fluid begins to flow into the piston chamber12from the first end16even as fluid is flowing through the second duct44to drive the piston assembly20upward. As the piston assembly20nears the stop position of the block104, the PCB54can control the valve40to continue opening the fluid flow path56as the valve closes the fluid flow path60between the port34and the second duct44. This control of fluid through both the first and second ducts42,44helps provide a smooth transition between upstrokes and downstrokes and helps compensate for switching times between upstrokes and downstrokes.

Likewise, the block106controls the transition between the downstroke (block106) and the upstroke (block102). During the block106, the PCB54can control the valve40to begin opening the fluid flow path60so that fluid begins to flow into the piston chamber12from the second end18even as fluid is flowing through the first duct42to drive the piston assembly20downward. As the piston assembly20nears the stop position of the block108, the PCB54can control the valve40to continue opening the fluid flow path60as the valve closes the fluid flow path56between the port34and the first duct42.

Other embodiments include all of the various combinations of individual features of each of the embodiments and examples described and/or claimed herein.

INDUSTRIAL APPLICABILITY

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