Cargo handling system

Disclosed is a cargo handling system, and a power drive unit (PDU) for a cargo handling system, wherein the PDU comprises a permanent magnet motor (PMM) and is designed to provide a first static restraint braking function effectuated by designing the PMM to have a high cogging torque, and a second dynamic control braking function effectuated by motor regeneration.

BACKGROUND

Cargo handling systems, such as those used by aircraft for transport of heavy containerized cargo or pallets, (also referred to as unit load devices (ULDs)) typically include roller trays containing transport rollers which rollably support the cargo, and a power drive unit (PDU) for facilitating loading and unloading operations.

Conventionally, braking function may be provided in the PDU and/or by adding braking rollers to the trays. To achieve braking function in the PDU, solenoid brakes may be utilized. However, solenoid brakes are typically biased to engage or alternatively disengage in a power-off state, with typical systems being designed to lose braking function in the power-off state.

Accordingly, such cargo handling systems typically utilize additional braking rollers to provide braking force in the power-off state. Therefore, in typical lower deck applications, which may contain between about 48 to 64 PDUs, the number of braking rollers may equal about 70% of the number of PDUs. Such braking rollers may react with a braking force in one or both directions, and may impose undesired resistance in normal operation. Additionally, such braking rollers take up space that may otherwise be utilized for transport rollers or restraint devices in the system.

SUMMARY

In accordance with various embodiments, disclosed is a cargo handling system, and a power drive unit (PDU) for a cargo handling system, wherein the PDU comprises a permanent magnet motor (PMM). According to various embodiments the PDU is designed to provide a first braking function for a static state which is a static restraint braking function effectuated by designing the PMM to have a high cogging torque; and a second braking function for a dynamic state which is a dynamic control braking function effectuated by motor regeneration. Thus, the PDU may allow for substantially reducing or eliminating braking rollers from cargo handling system.

In accordance with various embodiments, disclosed is a cargo handling system comprising a power drive unit (PDU), said PDU comprising a permanent magnet motor (PMM) having a power drive function, a first braking function, and a second braking function; and a wheel component in power driving engagement with said PMM, wherein said first braking function comprises a static restraint braking function, and said second braking function comprises a dynamic control braking function.

According to one embodiment, the PMM has a cogging torque of at least 16 ounce inch. According to one embodiment, the PMM has an output torque of at least 76 ounce inches. According to yet another embodiment, said second braking function comprises regenerative braking. According to yet another embodiment, the cargo handling system of claim further comprises a tray comprising a plurality of transport rollers supported on said tray, and retaining said PDU. According to yet another embodiment, the cargo handling system further comprises a cargo restraint device in said tray. According to yet another embodiment, the PMM comprises a magnet component including a magnet pole arc of approximately between 120 and 160 electrical degrees. According to one embodiment, the PMM comprises a magnet component including a magnet pole arc of approximately 140 electrical degrees.

According to one embodiment, the second braking function is triggered when the cargo handling system is in a powered off state.

According to one embodiment, the PMM comprises a resistance load effectuating said second braking function. According to another embodiment, the second braking function comprises a linear increasing force or a non-linear increasing force.

According to various embodiments, disclosed is a power drive unit (PDU), comprising: a permanent magnet motor (PMM) including a power drive function, a first braking function, and a second braking function; and a wheel component in power driving engagement with said PMM, wherein said first braking function comprises a static restraint braking function, and said second braking function comprises a dynamic control braking function. According to one embodiment, the PMM has a cogging torque of at least 16 ounce inch. According to one embodiment, the PMM has an output torque of at least 76 ounce inches. According to one embodiment, said second braking function comprises regenerative braking. According to one embodiment, the PMM comprises a magnet component including a magnet pole arc of approximately between 120 and 160 electrical degrees. According to one embodiment, the PMM comprises a resistance load effectuating said second braking function. According to yet another embodiment, said second braking function comprising a linear increasing force or a non-linear increasing force.

According to various embodiments, disclosed is a method of retrofitting a powered transport cargo system comprising braking rollers, the method comprising: replacing a power drive unit (PDU) of the powered transport cargo system with a PDU including a permanent magnet motor (PMM); and removing a braking roller from the powered transport cargo system. According to one embodiment, the method further comprises replacing said braking roller with at least one of a transport roller or a cargo restraint device.

DETAILED DESCRIPTION

All ranges and ratio limits disclosed herein may be combined. It is to be understood that unless specifically stated otherwise, references to “a,” “an,” and/or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural.

According to various embodiments, and with reference toFIGS. 1A and 1B, disclosed is a cargo handling system102, and a power drive unit (PDU)100for a cargo handling system102, wherein PDU100comprises a permanent magnet motor (PMM)200in power driving engagement with a wheel component103through, for example, a gear train assembly. According to various embodiments, PDU100comprising PMM200is designed to provide a first braking function110for a static state112, which is a static restraint braking function effectuated PMM200's high cogging torque, and a second braking function116for a dynamic state114which is a dynamic control braking function effectuated by motor regeneration (“dynamic braking function” or “regenerative braking”), in addition to its primary power driving function111. Thus, PDU100comprising PMM200may allow for substantially reducing or eliminating braking rollers from cargo handling system102.

Cargo handling system102, comprising PDU100, is illustrated inFIG. 1B, in accordance with various embodiments. According to various embodiments, cargo handling system102comprises a cargo system platform105, which supports trays104. Each tray104supports a plurality transport rollers106and retains at least one PDU100including wheel component103in each tray104. Trays104are configured to support cargo107, which is typically containerized in pallets or ULDs. According to various embodiments, trays104of cargo handling system102contain no braking rollers. According to various embodiments, cargo handling system102may comprise a plurality of spaced apart trays104positioned longitudinally throughout cargo system platform105. According to various embodiments, cargo handling system102may configured to transport cargo107at a transport speed of approximately between 45 feet per minute to 60 feet per minute (0.23 m/s to 0.30 m/s). Additionally, cargo handling system102may include cargo restraint devices108in trays104, such as end stops, and the like. As will be apparent to one skilled in the art, the size and operational parameters of cargo handling system102, including operating transport speed, number of trays, rollers, and PDUs, etc. may vary depending on the type of aircraft, operational conditions and requirements, etc.

Cargo handling system102may be employed for powered transport of cargo, typically heavy cargo, typically in lower deck aircraft operations, typically by wide body aircraft, but may also be employed in main deck operations, by smaller aircraft, according to various embodiments.

FIG. 1Cillustrates a method of retrofitting130a powered transport cargo system including braking rollers, according to various embodiments. The method130comprises replacing at least one power drive unit132with a PDU including a PMM. The method130further comprises removing at least some of the braking rollers134. The method further comprises replacing a portion or all of the braking rollers136with transport rollers and/or cargo restraint devices.

According to various embodiments, PMM200is designed to have a cogging torque sufficient to effectuate first braking function110or the static restraint braking function in static state112. In static state112, PMM200, and wheel component103, are generally stationary, which may be the case, for example, when power has been removed (e.g. in a power failure and/or manual loading operations, or when the system is not being used). In static state112first braking function110may be required to prevent a stationary or nearly stationary container positioned upon rollers106of the tray104from moving. For example, a container may start sliding due to tilting of the cargo platform, an undone restraint, etc. Typically, first braking function110is useful in a power off state caused by, for example, power failure and/or manual loading operations, according to various embodiments. Accordingly, the PDU100will hold a container starting to move in place.

FIG. 2is a cross section of a PMM200in accordance with various embodiments, generally comprising a magnet component202, a rotor204, and a stator component206. According to various embodiments, PMM200is designed to have a high cogging torque (i.e at least 16 ounce inches (113 Nm)). Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a PMM. Typically, cogging torque is an undesirable component for the operation of a PMM. It is especially prominent at lower speeds, and is associated with jerkiness. Cogging torque results in torque as well as speed ripple; however, as at high speed the motor moment of inertia filters out the effect of cogging torque, while maintaining a functional motor output torque. According to various embodiments, PMM200has a cogging torque of at least 16 ounce inches (113 Nm), and a motor output torque of at least 76 ounce inches (536 Nm). According to various embodiments, the desired parameters are achieved by adjusting the machine inductance as a function of rotor angle. According to various embodiments, the magnet pole arc (arc length of the magnetic pole) of magnet component202may be adjusted to meet these parameters.

Simulated studies on the effect of arc length on cogging torque and motor output torque values show that while the cogging torque is increased with arc length, the motor output torque is decreased, indicating a general trade off between the motor output torque and cogging torque. Thus, magnet component202may be designed with a magnet pole arc of about between 120 and 160 electrical degrees, and, in various embodiments, about 140 electrical degrees. Further simulated studies adjusting other parameters such as the slot opening205and air-gap207between the rotor and stator with the magnetic arc to effectuate a desired cogging torque and motor output values found magnet component202of PMM200may be designated at about 137 electrical degrees, with a slot opening205of about 0.06 inches (0.152 cm), and air gap207of about 0.014 inches (0.036 cm), according to various embodiments.

Additionally, the effective cogging resistance, which is the resistance produced at wheel component103by the cogging torque multiplied by the gear ratio from the wheel component103to PMM200. Thus, the effective cogging resistance can thus be adjusted based on the desired resistance, which may be determined by the angle of the aircraft.

As will be apparent to one skilled in the art, other parameters of PMM200may be adjusted for achieving desired cogging torque and motor output values such as the number of magnetic poles, the number of stator teeth, rotor angle, etc.

In addition to the first braking function110, PMM200also acts as a regenerative brake in order to effectuate second braking function116(dynamic control braking) in dynamic state114. In dynamic state114, cargo107is in motion, and first braking function110cannot control the motion. As illustrated inFIG. 3A, second braking function116is triggered in response to1) PDU100switching from a power on state300(seeFIG. 3A) to a power off state302(seeFIGS. 3A and 3C); and2) the first braking function110provided by the motor cogging torque being overridden (e.g. by an operator providing manual force to move a container, a sudden loss of power while a container is in motion and/or tilting of cargo system platform105, etc.). The triggering regenerative brake functionality occurs in response to the power supply being cut from the system (indicated by the open circuit at “S2” inFIG. 3C), and the simultaneous closing of “S1” reverses power flow (motor regeneration) from PDU100for activating second braking function116.

With reference toFIG. 4. according to various embodiments, the reaction force of second braking function116is tailored by adjusting the resistance load400applied at the terminals of PMM200to react based on the specific commands of cargo handling system102. According to various embodiments, the reaction force401of second braking function116may be tailored to provide a linear increasing force402which increases linearly with container velocity, or a non-linear increasing force404, and may preferably take into account factors such as maximum transport speed, tilt of cargo system platform105, container weight, etc. to provide sufficient restraint for a run away container, according to various embodiments. Such resistance force may be between about 40 pounds (18.1 kg) and 65 pounds (29.4), depending on system requirements. According to various embodiments, the resistance can be tailored through the gear train of wheel component103to generate a fixed value at the drive wheels for a specific speed value of the motor (i.e. speed of motor overridden by a moving container).

Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the invention. The scope of the invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.