Patent Description:
Electrical rotating machines, such as electric motors or generators, have become widespread and are found in numerous applications and configurations. Electric machines include a stationary component (i.e., the stator) and a rotating component (i.e., the rotor). In electric motors, a magnetic field is established in the rotor, for example via magnets mounted to the rotor or via an electrical current applied to or induced in a coil wound on the rotor. A second, rotating magnetic field is established as a result of the application of a controlled voltage to the stator, and the rotation of the magnetic field in the stator causes the magnetic field in the rotor to rotate, thereby causing rotation of the rotor. A shaft or other drive member is mounted to the rotor and extends outside the rotor housing providing a mechanical coupling to a device, such as a gearbox, pump, or fan that is to be driven as the rotor rotates. In some applications, the mechanical coupling may be made with a drive belt extending between the drive shaft of the motor and a drive pulley on the belt-driven equipment.

Belt drives may be used in a number of different industrial applications. The belt drive may be, for example, a timing belt, a V-belt, a ribbed belt, an open-ended belt, or an endless belt. The belt drive may be used to transfer power from a motor to a load, provide a direct coupling to a load for limited linear travel applications, or provide an indirect coupling to a load for conveying material in an endless loop. Applications include machine tools, printing, packaging, synchronous conveyors, separators, accumulators, and the like.

During installation, the belt is looped around one or more pulleys to transfer power from the motor to the load. The belt is looped around a drive shaft of the motor, or around a pulley mounted to the drive shaft, and similarly looped around a second pulley or a driven shaft at the belt-driven equipment. One or more additional pulleys or driven members may be included between the motor and the belt-driven equipment to drive additional pieces of equipment, route the belt, change rotation direction, and/or to provide tension in the belt. As the belt is looped around each pulley, the belt may be misaligned either via an offset to one side of the pulley or angularly with respect to the axis of rotation of the pulley on which it is mounted. Further, if tension in the belt-drive system is not properly set, either over or under tension of the belt will be present in the system. Both misalignment and improper tension may lead to excessive wear and/or premature failure of a component in the belt-drive system.

Thus, it would be desirable to detect misalignment, improper tension, or a combination thereof during installation or replacement of a belt in belt-driven equipment.

Due to the rotational nature of an electric machine and the components in the belt-drive system, misalignment and/or improper tension may generate an imbalance in the system due either directly to misalignment or indirectly to excessive wear of components caused by improper tension. During operation of the motor and belt-driven equipment, imbalances can result in vibrations or resonance being generated within the belt-drive system. These vibrations or resonances may not occur throughout the operating range of the motor but may occur at specific operating frequencies. The vibrations may cause excessive wear and/or premature failure of a component in the belt-driven system.

Thus, it would be desirable to monitor operation of drive members in a belt-driven application to detect vibrations present in the system to identify the potential failure of components prior to failure.

In addition to the wear caused by vibration, a shock load applied to the belt-drive system can cause catastrophic failure. If a single shock load does not cause catastrophic failure, it may still cause vibration and/or excessive wear of the belt-drive system. Repeated shock loads may, in turn, result in premature failure.

Thus, it would be desirable to provide a system to monitor operation of drive members in a belt-driven application to detect shock loads occurring in the system. <CIT> relates to techniques for monitoring the condition of pulley and belt assemblies. In an assembly, a belt is trained to move around two pulleys, a drive pulley and a driven pulley. An exciter device is arranged to introduce a controlled vibration into a span of the moving belt. The exciter device is in the form of a reciprocable piston, operated by a solenoid. The exciter device is arranged such that when the piston extends, it will strike the belt and thus impart an impulse causing the belt span to oscillate transversely. When a belt span vibrates in this way, the tension of the span fluctuates with a frequency twice that of the transverse oscillations. Vibration sensors are arranged near the belt so as to detect vibrations in the belt in its tight span and slack span respectively. A data processing unit is arranged to receive signals from the sensors.

The subject matter disclosed herein describes an improved system for monitoring drive members in a belt-driven application during installation and during operation and for detecting common failure modes in belt-driven equipment. Sensors are positioned within or proximate to the motor housing to detect vibrations on the belt or in the electric machine. The vibration signals are used to monitor operating conditions and/or to identify the failure modes in belt-driven equipment. The vibration signals may be used, for example, to determine tension on a belt, detect either a static or dynamic force applied along the belt, a misalignment between a pulley and the belt, or a shock load applied to the belt during operation. By monitoring the various operating conditions of the belt-driven equipment, a controller may identify an existing failure mode or predict a premature failure mode.

According to one embodiment, a system for monitoring operation of drive members in a belt-driven system includes at least one sensor configured to generate a signal corresponding to a vibration present on a belt in the belt-driven system and a motor controller. A motor is connected to and is operative to drive the belt, and the motor controller is configured to control operation of the motor. The motor controller includes an input configured to receive the signal corresponding to the vibration present on the belt from the at least one sensor, a memory device operative to store a plurality of configuration parameters and a plurality of instructions, and a processor configured to execute the plurality of instructions. The processor is configured to execute the instructions to receive the signal from the at least one sensor corresponding to the vibration present on the belt and to determine a tension present on the belt as a function of the signal corresponding to the vibration present on the motor.

According to another embodiment of the invention, a method for monitoring operation of drive members in a belt-driven system is disclosed. A signal is received at an input of a motor controller from at least one sensor corresponding to a vibration present on a belt in the belt-driven system. A motor is connected to and controlled by the motor controller, and the motor is operative to drive the belt. The motor controller determines a frequency of vibration present in the belt-driven system as a function of the signal received at the motor controller and determines a tension present on the belt as a function of the frequency of vibration present in the belt-driven system.

These and other advantages and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention, and the invention includes all such modifications.

Turning initially to <FIG>, an exemplary motor <NUM> incorporated in one embodiment of a belt-drive system and configured to aid in monitoring operation of and detecting common failure modes in belt-driven equipment is illustrated. The motor <NUM> includes a frame <NUM> open at each end. A front end cap <NUM> and a rear end cap <NUM> enclose each end and, in combination with the frame <NUM>, define a housing for the motor <NUM>. The motor <NUM> includes a stator assembly <NUM>, configured to receive a voltage to control operation of the motor <NUM>, and a rotor assembly <NUM> configured to rotate as a function of the voltage applied to the stator assembly <NUM>. A junction box <NUM> is mounted to the frame <NUM> and is configured to receive motor leads <NUM> from a motor controller <NUM> (as shown in <FIG>) which are, in turn, connected to leads <NUM> from the stator assembly <NUM> within the junction box <NUM>, establishing an electrical connection between the stator assembly <NUM> and the motor controller <NUM>.

The rotor assembly <NUM> includes a rotor <NUM> and a motor shaft <NUM>. The motor shaft <NUM> may extend all the way through the rotor <NUM> or, optionally, a first portion of the shaft may extend from the front of the rotor assembly <NUM> and a second portion may extend from the rear of the rotor assembly <NUM>. The shaft <NUM> extends through an opening in the front end cap <NUM> for mechanical coupling to a driven machine. A pulley may be mounted to the shaft <NUM> on which a belt may, in turn, be mounted. The rotor assembly <NUM> is supported for rotation within the housing by a front bearing set <NUM> and a rear bearing set <NUM>, located within the front end cap <NUM> and the rear end cap <NUM>, respectively. In the illustrated embodiment, a cooling fan <NUM> draws air in through the openings in the rear end cap <NUM> which passes over and cools both the stator assembly <NUM> and the rotor assembly <NUM>. The rotor assembly <NUM> may include magnets mounted on the surface or embedded within the rotor <NUM> to generate a magnetic field. Optionally, the rotor <NUM> may include a coil or a set of coils configured to receive a voltage, for example, via slip rings mounted to the rotor assembly <NUM> or via induction from the voltage applied to the stator assembly <NUM>. It is contemplated that the various other configurations and arrangements of the motor <NUM> may be utilized without deviating from the scope of the invention.

Control of the motor <NUM> may be accomplished with a motor controller <NUM>. Referring next to <FIG>, a motor controller <NUM> according to one embodiment of the invention includes a power input <NUM> configured to be connected to a power source. According to the illustrated embodiment, a three-phase alternating current (AC) power source is connected to the power input <NUM>. Optionally, the motor controller <NUM> may be connected to a single-phase AC power source or to a direct current (DC) power source. A rectifier section <NUM> converts the three-phase AC power to a DC voltage present on the DC bus <NUM>. The rectifier section <NUM> may be a passive rectifier, including, for example, diode bridge rectification, or an active rectifier, including, for example, semiconductor switching devices such as an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field-effect transistor (MOSFET), a silicon-controlled rectifier (SCR), a thyristor, or any other suitable controlled switching device. The rectifier section <NUM> may transmit or receive signals <NUM> with the processor <NUM> including, but not limited to, feedback signals generated by sensors located in the rectifier section <NUM> corresponding to a current and/or a voltage present at the input to or output from the rectifier section <NUM> or switching signals generated by the processor <NUM> to control switching devices in an active rectifier. The DC bus <NUM> includes a capacitance <NUM> connected between a positive rail and a negative rail across which the DC voltage potential is present. It is contemplated that the positive rail and the negative rail may each have a positive voltage potential, a negative voltage potential, or be connected to a common voltage potential. Typically, the positive rail has a greater voltage potential than the negative rail. The processor <NUM> may also receive signals <NUM> from a sensor connected to the DC bus including, for example, a signal corresponding to the voltage and/or current present on the positive rail, the negative rail, or between the two rails. An inverter section <NUM> converts the DC voltage present on the DC bus <NUM> to an AC voltage having a variable frequency and a variable magnitude. The inverter section <NUM> includes, for example, semiconductor switching devices such as IGBTs, MOSFETs, SCRs, thyristors, or any other suitable controlled switching device. The inverter section <NUM> may transmit or receive signals <NUM> with the processor <NUM> including, but not limited to, feedback signals generated by sensors located in the inverter section <NUM> corresponding to a current and/or a voltage present at the input to or output from the inverter section <NUM> or switching signals generated by the processor <NUM> to control operation of the switching devices. The motor controller <NUM> includes a processor <NUM> configured to execute a series of instructions stored on a memory device <NUM>. The processor <NUM> may be a single processing device or multiple processing devices executing in parallel. The processor <NUM> may be a field programmable gate array (FPGA), application specific integrated circuit (ASIC), digital signal processor (DSP), general purpose microprocessor, dedicated processor, or a combination thereof. The memory device <NUM> may be a single device or multiple devices and may include volatile memory, non-volatile memory or a combination thereof. The motor controller <NUM> also includes at least one input <NUM> configured to receive at least one feedback signal <NUM> from the motor <NUM>. The processor <NUM> receives each feedback signal <NUM> from the input(s) <NUM>, where the feedback signal may be, but is not limited to an angular position signal, an angular velocity signal, a current signal, a voltage signal, and a signal corresponding to an amplitude of vibration present in the motor <NUM>.

Referring again to <FIG>, the motor <NUM> includes at least one sensor <NUM> which is configured to generate a signal corresponding to the vibration present in the motor <NUM>. According to the illustrated embodiment, the sensor <NUM> is mounted within the housing of the motor <NUM>. Optionally, the sensor <NUM> may be mounted on the exterior of the housing or on a mechanical member coupled to the motor <NUM> such that the vibration detected in the sensor <NUM> corresponds to the vibration present in the motor <NUM>. The sensor <NUM> may be, for example, an accelerometer, generating a signal corresponding to the acceleration in one or more axes of the motor <NUM>, an acoustic sensor, detecting a frequency of noise generated due to a vibration in the system, or an ultrasonic measuring sensor, detecting variation in a distance of a surface from the sensor as a result in vibration. In one embodiment of the invention, the sensor is a microelectromechanical system (MEMS). In a belt-driven system, such as the system <NUM> illustrated in <FIG>, the vibration in the motor <NUM> may be a result of vibration in a belt <NUM> coupled to the motor, where the vibration is transferred through the coupling or drive elements between the motor and the belt.

Referring also to <FIG>, another exemplary motor <NUM> incorporated into a belt-drive system is illustrated. The motor <NUM> includes a mounting plate <NUM> on one end of the frame <NUM> by which the motor <NUM> is connected to a drive train. As illustrated, the mounting plate <NUM> includes a recessed portion <NUM> within which a circuit board <NUM> is mounted. The circuit board <NUM> includes a first sensor 40a mounted on the top and a second sensor 40b mounted on the bottom of the board. Optionally, the circuit board <NUM> may include a single sensor <NUM> or include still additional sensors located, for example, on the left and right sides of the motor shaft <NUM>.

According to another embodiment of the invention, illustrated in <FIG>, a first sensor <NUM> may be mounted on and rotate with the shaft <NUM> to directly detect vibration on the shaft <NUM>. The motor <NUM> is illustrated in block diagram form by a series of concentric circles with the stator assembly <NUM> as the outermost circle, the rotor <NUM> as the intermediate circle, and the motor shaft <NUM> as the innermost circle. Optionally, the sensor <NUM> may also include a transceiver portion (not shown) mounted to a non-rotational location proximate to the shaft <NUM> and configured to receive the signal corresponding to the acceleration in each axis. The signal may be communicated, for example, from the rotating portion of the sensor <NUM> via wireless communications or via a slip ring configuration to the transceiver portion, which, in turn, transmits the signal to a controller. It is also contemplated that the signal may be communicated directly to another controller, such as the motor controller <NUM>. The motor <NUM> may also include a second sensor <NUM> mounted to the non-rotational portion of the motor <NUM>. As illustrated, the second sensor <NUM> is mounted to the stator assembly <NUM>. However, it could similarly be mounted, for example, to an internal surface of the housing or to a bearing set within the motor <NUM>. A signal corresponding to the vibration experienced by the housing of the motor <NUM> may be generated by the second sensor <NUM>. With signals generated both by the sensor <NUM> mounted on the shaft <NUM>, or another rotational portion of the motor <NUM>, and the sensor <NUM> mounted to the non-rotational portion of the motor <NUM>, a controller may differentiate between vibrations experienced generally by the motor <NUM> from vibrations present only on the motor shaft <NUM>.

According to another embodiment of the invention, two sensors <NUM> may be mounted to non-rotational portions of the motor <NUM>. Referring also to <FIG>, a first sensor <NUM> is located at a first position <NUM> within the motor <NUM> and a second sensor <NUM> is located at a second position <NUM> within the motor <NUM>. The motor <NUM> is illustrated in block diagram form by a series of concentric circles with the stator assembly <NUM> as the outermost circle, the rotor <NUM> as the intermediate circle, and the motor shaft <NUM> as the innermost circle. According to one embodiment of the invention, both the first and second sensors <NUM> are mounted on a bearing set <NUM> by which the rotor <NUM> is rotatably mounted to the housing. Each of the sensors <NUM> may be mounted on opposite sides of the shaft <NUM> or of the portion of the rotor <NUM> supported by the bearing set <NUM>.

A plane <NUM> orthogonal to the rotor shaft <NUM> and axes of each sensor and of the motor is also shown in <FIG>. A first, central axis <NUM> defines the axis about which the motor shaft <NUM> rotates and extends through the motor <NUM>. A second axis <NUM> is defined as orthogonal to the central axis <NUM> and extends between a top and a bottom of the motor <NUM>. A third axis <NUM> is defined as orthogonal to both the central axis <NUM> and the second axis <NUM>, extending between the sides of the motor <NUM>. The second axis <NUM> and the third axis <NUM> exist within plane <NUM>. Additionally, references to the top, bottom, and/or sides or for illustration only. It is contemplated that the second axis <NUM> and the third axis <NUM> may be rotated within the plane <NUM> orthogonal to the rotor shaft <NUM> without deviating from the scope of the invention. As illustrated, the central axis <NUM> is defined as a "Z" axis, the second axis <NUM> is defined as a "X" axis, and the third axis <NUM> is defined as a "Y' axis of the motor <NUM>. Each of the sensors <NUM> similarly has three axes illustrated. The sensor <NUM> at the first position <NUM> is shown with a Z axis <NUM> with a positive magnitude in the Z axis illustrated, Z), an X axis <NUM> with a positive magnitude in the X axis illustrated, X<NUM>, and a Y axis <NUM> with a positive magnitude in the Y axis illustrated, Yt. The sensor <NUM> at the second position <NUM> is shown with a Z axis <NUM> with a positive magnitude in the Z axis illustrated, Z<NUM>, an X axis <NUM> with a positive magnitude in the X axis illustrated, X<NUM>, and a Y axis <NUM> with a positive magnitude in the Y axis illustrated, Y<NUM>. It is contemplated that each sensor <NUM> may detect vibration in either fewer or greater number of axes without deviating from the scope of the invention. Similarly, multiple sensors <NUM>, each detecting vibration in a single axis may be used to detect vibration of the motor <NUM> in multiple axes. A positive magnitude of vibration for each axis of each of the sensors <NUM> is illustrated by the direction of the vectors, X<NUM>, Y<NUM>, Z<NUM>, X<NUM>, Y<NUM>, and Z<NUM>. Thus, the first sensor <NUM> and the second sensor <NUM> are mounted such that a vibration in the motor which generates a signal in the first sensor <NUM> having a positive magnitude will generate a signal in the second sensor <NUM> having a negative magnitude.

According to one embodiment of the invention, the two X axes, X<NUM> and X<NUM>, are configured to measure vibrational forces tangential to the motor shaft <NUM> and in opposite directions. The two Y axes, Y<NUM>, and Y<NUM>, are configured to measure vibrational forces orthogonal to the central axis <NUM> of the motor shaft <NUM> surface and directed in opposite directions away from the motor shaft <NUM>. The two Z axes, Z<NUM> and Z<NUM>, are configured to measure vibrational forces aligned with but offset from the central axis <NUM> of the motor shaft <NUM> and in opposite directions. It is contemplated that each pair of sensors is positioned within the plane <NUM> orthogonal to the motor shaft <NUM> and such that each sensor <NUM> is positioned <NUM> degrees around the motor shaft <NUM> from the other sensor <NUM>. Optionally, the sensors <NUM> may be positioned other than <NUM> degrees around the motor shaft <NUM> from each other. However, additional computation may be required to compensate for the sensor position if the sensors <NUM> are positioned other than <NUM> degrees around the motor shaft <NUM> from each other.

It is contemplated that the controller receiving the signals may be the processor <NUM> in the motor controller <NUM> or a second controller, such as a programmable logic controller (PLC) or other industrial controller. Referring, for example, to <FIG>, a controller <NUM> is connected to multiple vibration sensors <NUM>. A first vibration sensor <NUM> is illustrated on a circuit board <NUM> mounted within a motor <NUM>. Additional vibration sensors <NUM> are shown without reference to a specific location, but may be mounted at different locations on the circuit board <NUM>, at other locations within or on the motor <NUM>, or may be mounted, for example, on a structural member to which the motor <NUM> is mounted. The controller <NUM> includes a logic circuit <NUM> configured to receive the data signals from the vibration sensors. The logic circuit <NUM> may include an analog to digital converter to convert the signals to a value suitable for input to a processor <NUM> on the controller <NUM>. Optionally, the logic circuit <NUM> may include additional signal processing capabilities and may, for example, perform some initial processing such as adding or subtracting signals corresponding to the same axis of vibration and generated from vibration sensors <NUM>. The controller <NUM> further includes a memory device <NUM> in communication with the processor <NUM>. The processor may be further configured to execute instructions stored on the memory device <NUM> to perform additional processing of the signals and to generate command signals to control operation of the motor controller <NUM> as a function of the vibration signals. Similarly, the controller <NUM> may be configured to identify a vibration source in the belt-driven system as a function of the vibration signals.

According to the embodiment illustrated in <FIG>, the controller <NUM> is an industrial controller, such as a programmable logic controller (PLC). The PLC includes a power supply and a processor module <NUM> housed in a rack <NUM> with multiple slots <NUM>. A backplane extends between the processor module <NUM> and each slot <NUM> for communication with modules inserted into the slot. Various modules may be provided with each having different capabilities, including, but not limited to, an input module, an output module, a communication module, and the like. Input modules may each include a logic circuit <NUM> for receiving a signal from a vibration sensor <NUM>. The input modules are configured to receive the analog vibration signals and include an analog to digital converter circuit and/or additional processing capabilities to transfer a digital value of the analog feedback signal to the processor module <NUM> via the backplane in the PLC.

According to the embodiment illustrated in <FIG>, the motor controller <NUM> is illustrated with modules <NUM>, <NUM>, <NUM> executing on the processor <NUM>, where the different modules act on the vibration signals as will be discussed in more detail below. It is contemplated that the controller <NUM> may also execute modules <NUM>, <NUM>, <NUM> to act on the vibration signals and the motor controller <NUM> may be configured to pass the vibration signals through to the controller <NUM> without additional processing. Optionally, a portion of the modules <NUM>, <NUM>, <NUM> may execute on the motor controller <NUM> and a portion of the modules may execute on the PLC <NUM>. In still other embodiments of the invention, an industrial system or process controlled by the PLC may include multiple motors <NUM> and multiple motor controllers <NUM>. A portion of the motor controllers <NUM> may execute the modules to act on the vibration signals corresponding to one or more belts in a first portion of the controlled system and the PLC <NUM> may execute similar modules to act on vibration signals corresponding to one or belts in a second portion of the controlled system.

Referring next to <FIG>, an exemplary belt-driven system <NUM> includes a first pulley <NUM> and a second pulley <NUM> connected via a belt <NUM>. According to the exemplary system <NUM>, the belt <NUM> includes teeth <NUM> configured to engage complementary gear teeth extending around the periphery of each pulley. The drive shaft <NUM> of a motor <NUM> may be mechanically coupled to either the first pulley <NUM> or to the second pulley <NUM> (i.e., the driver pulley) and the belt <NUM> is configured to drive the other pulley not coupled to the motor (i.e., the driven pulley). Varying the diameter of each pulley causes the speed and torque at each pulley to vary as is understood in the art.

Turning next to <FIG>, a second exemplary belt-driven system <NUM> includes a segment of a conveyor system moving objects <NUM> along a series of driven belts <NUM>. The segment of the conveyor system includes a first conveyor pulley <NUM> and a second conveyor pulley <NUM>. In the illustrated embodiment, it is contemplated that each conveyor pulley includes two grooves in which a belt <NUM> may run. In the first conveyor pulley <NUM> a first belt 214a engages a first groove and a second belt 214b engages a second groove. In the second conveyor pulley <NUM>, the second belt 214b engages the second groove such that the belts <NUM> extend in a linear manner aligned with the pulleys <NUM>, <NUM> along the length of the conveyor system. A third belt 214c engages the first groove of the second conveyor pulley <NUM>. Additional belts <NUM> may extend along the length of the conveyor system alternately engaging the first and second grooves. In another embodiment of the invention, a single belt <NUM>, or multiple lengths of belt spliced together, may extend along the length of the belt-drive system <NUM> or across more than two pulleys. Further, it is contemplated that a single motor may drive one of the conveyor pulleys <NUM>, <NUM> while the remaining conveyor pulleys are driven by the series of belts <NUM>. Optionally, each of the pulleys <NUM>, <NUM> may be driven by separate motors operating in coordination with each other. In still other embodiments, a portion of the pulleys may be driven by a motor and a portion of the pulleys may be driven by the belts <NUM>. It is contemplated that the present invention may be incorporated on still other configurations of belt driven systems where the belt driven system may be utilized to change the direction of rotation of a pulley, convert rotational motion to a linear or reciprocating motion, and the like.

In operation, the sensors <NUM> provide an improved system for monitoring operation of or detecting and identifying the source of vibration in a belt in a belt-driven system <NUM>. The belt <NUM> is operatively connected to and driven by a motor <NUM> via a pulley <NUM> and drive shaft <NUM>. The motor <NUM> is, in turn, controlled by a motor controller <NUM>. Vibration in the belt <NUM> is translated to the motor <NUM> and/or to a mechanical structure on which the motor <NUM> is mounted. Sensors <NUM> placed within, on the surface of, or proximate to the motor <NUM> detect the vibration. The vibration may be caused by numerous sources including, but not limited to, mechanical resonance, shaft misalignment, belt misalignment, improper tension in a belt-driven system, or shock loading. It is contemplated that the motor controller may use the measured vibrations to determine a frequency of vibration present in the belt <NUM> and, in turn, determine a level of tension present on the belt <NUM> or determine the type.

During commissioning, the system may be used to monitor and adjust operation of drive members in the belt-driven system <NUM>. After a belt <NUM> has been installed around the drive member(s) and the driven member(s), the tension present on the belt <NUM> needs to be verified. The belt-driven system is designed such that the belt has sufficient tension to transfer power between a drive member and a driven member, yet not too much tension which may result in premature wear and/or failure of the belt.

For illustration purposes, the belt-driven system <NUM> of <FIG> will be referenced. The second pulley <NUM> will be described as the drive pulley and is connected to a motor shaft <NUM>. The first pulley <NUM> will be described as the driven pulley and is connected to a controlled device or process. The belt <NUM> is fit around the two pulleys and one of the two pulleys <NUM>, <NUM> includes a movable mount such that the position of the pulley is changed to apply tension to the belt <NUM>. Optionally, a tensioner pulley (not shown) may be included in the belt-driven system <NUM>, where the tensioner pulley is movably mounted and is configured to engage the belt <NUM> with different amounts of force to vary the tension on the belt <NUM>.

Once the belt <NUM> is installed, an impulse force is applied to the belt <NUM>. The impulse force may be applied manually by striking the belt. Optionally, the motor controller <NUM> is configured to apply an impulse, or short current pulse, to the motor <NUM> controlling the drive pulley <NUM>. The impulse applied to the motor <NUM>, in turn, generates a torque pulse on the drive shaft <NUM> and along the belt <NUM> operatively connected to the drive shaft via the drive pulley <NUM>. During commissioning, it may be desirable to apply the impulse while the drive pulley <NUM> is in a static, or non-spinning, operational state because the controlled system may not be fully ready to run or it may be dangerous to apply full energy. If the motor controller <NUM> is utilized to apply an impulse, the impulse applies a momentary torque to the drive shaft <NUM> and, subsequently, the motor controller <NUM> commands the motor <NUM> to hold zero speed. As a result, the motor <NUM> receives and transfers the impulse to the drive pulley <NUM> and drive belt <NUM> but does not begin rotation of the pulley or belt.

After applying the impulse, the motor controller <NUM> monitors the feedback signal(s) corresponding to the vibration present along the belt <NUM>. With reference to <FIG>, a belt tension module <NUM> may be used to determine a tension present on the belt <NUM>. As previously discussed, in one embodiment of the invention, the belt tension module <NUM> as well as the other illustrated modules <NUM>, <NUM>, execute on the motor controller <NUM>. In another embodiment of the invention, the belt tension module <NUM> and other illustrate modules <NUM>, <NUM> execute on the industrial controller <NUM>. In still another embodiment, the modules <NUM>, <NUM>, <NUM> may execute on a combination of the motor controller <NUM> and the industrial controller <NUM>. For ease of discussion, the modules will be discussed generally as executing on a controller, where the controller may be either the motor controller <NUM> or the industrial controller <NUM>. The controller is operative to detect tension applied to the belt by measuring at least one characteristic of the vibration signal generated by the vibration sensor(s) <NUM> mounted proximate to or within the motor <NUM>. The characteristics of the vibration signal to be monitored may include the belt natural frequency, an rms or a peak value of the vibration signal, the kurtosis of the vibration signal, or the crest factor of the vibration signal. According to the illustrated embodiment, a frequency response module <NUM> is provided which determines frequency components present in the vibration signal using, for example, a Fourier transform, a discrete Fourier transform (DFT), a Goertzel algorithm, or a combination or modification thereof. An exemplary embodiment of the frequency response module <NUM> is discussed in more detail below. An additional processing module <NUM> may be used to execute other routines that determine the peak, rms, kurtosis, or crest-factor values of the vibration signal. Each of the frequency response module <NUM> and additional processing module <NUM> may be called, for example, on a periodic interval or from the belt tension module <NUM>. It is understood that illustrated division of modules is exemplary and not intended to be limiting. The functions performed by the various modules <NUM>, <NUM>, <NUM> may be executed in whole or in part by other modules or other combinations of modules.

If one, single-axis sensor <NUM> is provided, a single vibration feedback signal <NUM> is provided to the motor controller <NUM>. If multiple sensors <NUM> or a multi-axis sensor <NUM> is provided, multiple vibration feedback signals <NUM> are present. Referring also to <FIG>, a first vibration feedback signal 76a is illustrated in the top plot and a second vibration feedback signal 76b is illustrated in the lower plot. The two vibration feedback signals may each correspond to a single axis output from separate sensors <NUM> or may correspond to different axes output from a multi-axis sensor <NUM>. The signals illustrated in <FIG>, represent, for example, the response to an impulse applied to the belt <NUM>.

According to one embodiment of the invention, the motor controller <NUM> may include a parameter stored in the memory device <NUM> defining a threshold above which the motor controller <NUM> recognizes an impulse was applied to the belt. According to the illustrated embodiment, it is contemplated that the threshold is set equal to one. At the start of each vibration signal 76a, 76b, the amplitude exceeds a positive and negative one and, therefore, the motor controller <NUM> detects the application of an impulse.

According to another embodiment of the invention, the motor controller <NUM> applies the impulse by controlling operation of the motor <NUM> with the motor and belt in a static condition. Because, there is no initial operation of the belt <NUM> prior to applying the impulse, the motor controller <NUM> monitors the vibration feedback signals <NUM> for any amplitude of vibration and attributes the measured vibration to the impulse.

After detecting the vibration resulting from application of the impulse, the motor controller <NUM> determines a tension on the belt as a result of the monitored vibration feedback signal 76a, 76b. The motor controller <NUM> may utilize any suitable technique to identify the frequency present on the vibration signal. According to one aspect of the invention, the motor controller <NUM> utilizes the frequency response module <NUM> stored in the memory device <NUM> of the motor controller <NUM>. The frequency response module <NUM> may be configured to execute a Discrete Fourier Transform(DFT). An exemplary DFT routine is presented below in Eq. <NUM>. The DFT routine transforms a sampled time signal into a complex vector, containing magnitude and phase information, for a number of evenly spaced frequency bins between zero hertz and the sampling frequency of the vibration feedback signal <NUM>. <MAT> where:.

The frequency response includes an amplitude for each frequency component at the evenly spaced frequencies. The amplitude of the frequency content at each of the evenly spaced frequencies with the greatest amplitude responsive to the applied impulse is identified as the natural frequency of the belt <NUM>. The natural frequency of the belt <NUM> is a function of and varies with the tension applied to the belt. As a result, Eq. <NUM>, presented below, may be used to determine the tension of the belt as a function of the natural frequency of the belt. <MAT> where:.

The belt tension monitor module <NUM> in the motor controller <NUM> may further be configured to provide an output signal corresponding to the tension, Fr, present on the belt <NUM>. According to one embodiment of the invention, the belt tension monitor module <NUM> outputs a signal that includes the amplitude of the tension determined. The output signal may be a data frame in which the value of the tension, Ft, is inserted into the payload. Optionally, the motor controller <NUM> may include a user interface with a display on which the output signal is presented to provide a visual indication of the tension, Fr, on the belt <NUM> to a technician. According to another embodiment of the invention, the belt tension monitor module <NUM> may be configured to output one or more logic signals corresponding to the amplitude of tension determined. Configuration parameters stored in the memory <NUM> of the motor controller <NUM> define a desired level of tension and an upper and lower limit of the acceptable tension, or, optionally, the configuration parameters may store just an acceptable range of tension. The belt tension monitor module <NUM> compares the measured amplitude of tension to the configuration parameters and outputs a logic signal identifying whether the tension is at the desired setpoint or outside of the acceptable range. The belt tension monitor module <NUM> may be further configured to output one or more additional logic signals indicating whether the tension is above the acceptable range or below the acceptable range. After receiving the output signal corresponding to the tension present on the belt <NUM>, the technician may increase or decrease the tension and repeat the process of applying an impulse and monitoring the output signal from the motor controller <NUM> until the tension has been properly set for the belt <NUM>. Utilizing the motor controller <NUM> to apply an impulse and measure tension on the belt <NUM> simplifies the commissioning process and eliminates the need for a separate tension meter.

During commissioning, it is further contemplated that the controller may be trained to measure vibration data and to predict belt tension as a function of the measured vibration data. As an initial step in the training, the motor controller <NUM> obtains data corresponding to known operation of the belt-driven system <NUM>. The tension on the belt <NUM> is set to a known value and the motor controller <NUM> is configured to operate the motor <NUM> at multiple speeds. As the motor <NUM> runs, the motor controller <NUM> monitors the magnitude of the vibration signals or the magnitude of frequency components detected in the vibration signals. Further, the motor controller <NUM> monitors the speed at which the motor <NUM> is rotating either via a speed command internal to the motor controller or by monitoring the feedback signal from the position feedback sensor <NUM> from which the speed is determined. Optionally, the motor controller <NUM> may also monitor the magnitude of current being supplied to the motor. During operation at each of the multiple speeds, the motor controller <NUM> stores the monitored data in a data log <NUM> in the memory <NUM> of the motor controller. The motor controller <NUM> uses the data corresponding to known operation which was obtained during normal operation of the motor <NUM> to predict the tension present on the belt <NUM>. After commissioning, the system continues to monitor operation of drive members in the belt-driven system <NUM>. The memory device <NUM> in the motor controller <NUM> may store the tension measured during the application of the impulse discussed above in a configuration parameter. Optionally, a configuration parameter may be set to a desired tension from a user interface or via a set of configuration parameters loaded into the memory device <NUM>. The motor controller <NUM> receives the feedback signal(s) corresponding to vibration present on the belt and periodically determines a tension present on the belt <NUM> using, for example, the DFT routine discussed above. The belt tension monitor module <NUM> in the controller compares the current value of tension present on the belt to the previously stored value of tension. If the current value of tension present on the belt varies from the previously stored value of tension beyond a predefined amount, the tension has changed during operation and the belt tension monitor module <NUM> generates a notification indicating that the tension has changed. The belt tension monitor module <NUM> may set an internal alarm or fault bit within the motor controller <NUM> or transmit the notification to the industrial controller <NUM>. Optionally, the notification may be transmitted, alternately or additionally, via a data message to a remote terminal, for example, to alert maintenance personnel that the belt <NUM> needs to be inspected. With reference to <FIG>, the remote terminal may be, for example, a computer <NUM> located either proximate to or remote from the industrial controller <NUM> via a wired connection, a wireless connection, or a combination thereof. Optionally, the remote terminal may be a mobile device <NUM>, such as a mobile phone, tablet, or laptop computer in communication with the industrial controller <NUM> via a wired connection, a wireless connection, or a combination thereof. After receiving notification of improper tension on the belt, the maintenance personnel may adjust the tension and/or replace the belt <NUM> as needed.

If the motor controller <NUM> has training data stored in the data log <NUM>, the training data is used to predict the tension present on the belt <NUM>. The measured vibration signals vary as a function of the speed at which the motor <NUM> connected to the belt-driven equipment is operating and as a function of the tension present on the belt <NUM>. With the training data stored in the data log <NUM>, the motor controller can compare the present value of vibration detected and the speed at which the motor <NUM> is operating against the training data stored in the data log <NUM> to determine whether the present value of vibration is within an expected range of vibration for the speed of the motor <NUM>. The belt tension monitor module <NUM> may generate a logic signal identifying whether the tension is at the desired setpoint or outside of the acceptable range. The belt tension monitor module <NUM> may be further configured to generate one or more additional logic signals indicating whether the tension is above the acceptable range or below the acceptable range. These signals are output to the industrial controller <NUM>, the computer <NUM>, the mobile device <NUM>, or a combination thereof to alert a technician of the status of the belt-driven equipment. After receiving notification of improper tension on the belt, the technician may adjust the tension and/or replace the belt <NUM> as needed.

According to still another aspect of the invention, the motor controller <NUM> may detect shock loads occurring in the belt-driven system <NUM> during operation. A configuration parameter stored in the memory device <NUM> of the motor controller <NUM> stores a preset value for vibration. The preset value identifies a threshold of vibration, above which, is indicative of a shock load occurring in the belt-driven system <NUM>. The motor controller <NUM> receives the feedback signal(s) corresponding to vibration present on the belt and periodically determines a magnitude of vibration present on the belt <NUM> using, for example, the DFT routine discussed above. The motor controller <NUM> compares the magnitude of vibration present on the belt to the previously stored threshold of vibration indicative of the occurrence of a shock load. If the magnitude of vibration present on the belt exceeds the threshold, the motor controller <NUM> generates a notification indicating that a shock load has occurred. The notification may be transmitted via a data message to a remote terminal, for example, to alert maintenance personnel of the shock loading. It is further contemplated that the magnitude of vibration present on the belt may also be stored in the memory device <NUM>. The memory device <NUM> may include a buffer where a number of values of the magnitude of vibration may be stored. The magnitude of vibration may be transmitted along with the notification of the shock load occurrence such that a technician or maintenance personnel may determine the severity of the shock loading. Optionally, the buffer may be accessed via a remote terminal or via a display on the motor controller to view the severity of each shock load occurrence.

According to another aspect of the invention, the motor controller <NUM> may be configured to track a number of occurrences of shock loading. A configuration parameter in the memory device <NUM> of the motor controller <NUM> may serve as a counter. Each time the motor controller <NUM> detects the occurrence of a shock load, the motor controller <NUM> increments the value in the counter. Still another configuration parameter may be configured to store a counter threshold value. Rather than generating a notification for each occurrence of a shock load, the motor controller <NUM> may be configured to generate a notification when the number of shock loads exceeds the counter threshold value. In still other embodiments of the invention, multiple thresholds may be configured to detect shock loads of varying magnitude. Different reporting requirements may be established based on the severity of the shock load detected.

According to yet another aspect of the invention, the motor controller <NUM> may be configured to identify different causes of potential belt failure and provide diagnostic information prior to a failure occurring. With reference also to <FIG>, two potential causes of belt failure are indicated. In <FIG>, a belt-driven system <NUM> is illustrated in which an offset <NUM> between the center axes <NUM>, <NUM> of two pulleys <NUM>, <NUM> is present. Due to manufacturing tolerances and/or assembly error, the center axes <NUM>, <NUM> which should be aligned within the system <NUM> are offset <NUM> from each other. The offset <NUM> may introduce unwanted vibration on the belt <NUM> extending between the two pulleys <NUM>. In <FIG>, a segment of a belt-driven system <NUM> illustrates a belt <NUM> routed over a pulley <NUM> where the belt is mis-aligned with the pulley. An angle offset, θ, <NUM> exists between the actual alignment of the belt <NUM> and the desired alignment of the belt, where the desired alignment of the belt is parallel to the rotation of the pulley <NUM>. The angle offset, θ, <NUM> may similarly introduce unwanted vibration on the belt <NUM>. In either of the illustrated systems <NUM>, <NUM>, the motor controller <NUM> may be configured to detect vibration resulting from the offset and generate a notification of the identified vibration. Parallel offset <NUM> and angular offset <NUM> introduce vibrations in the belt <NUM>, <NUM> either along the radial or axial directions. In one embodiment of the invention, a pair of sensors <NUM> are mounted to a non-rotational portion of the motor <NUM> to isolate sources of vibration in the belt. The sensors <NUM> are configured as discussed above with respect to <FIG>. The motor controller <NUM> utilizes signals from both the sensor <NUM> at the first position <NUM> and the sensor <NUM> at the second position <NUM> along at least one of the axes, X, Y, or Z, to isolate different vibrations. Using signals from both sensors <NUM> helps cancel electrical noise that may be generated within the motor <NUM> and/or by the motor controller <NUM> and received by the sensors <NUM> and/or transmitted along the electrical conductors carrying the vibration signals. With reference to Table I, included below, the motor controller utilizes the vibration signals along the different axes, X, Y, or Z, to isolate different vibrations. Based on the magnitude of vibrations present along each axis, the motor controller <NUM> determines whether the vibration is radial or axial and may identify whether a parallel offset <NUM> and/or an angular offset <NUM> is present in the belt-driven system.

According to yet another aspect of the invention, the motor controller <NUM> is configured to drive the motor according to an excitation profile stored in the memory <NUM> of the motor controller <NUM>. The excitation profile includes a predefined speed or speeds at which the motor is to operate. The excitation profile may further include one or more acceleration profiles to vary the rate at which belt-driven changes speeds. As the motor controller <NUM> commands the motor <NUM> to operate according to the excitation profile, the signal(s) from the vibration sensor(s) <NUM> corresponding to vibration present on the belt is monitored by the motor controller <NUM>. The motor controller <NUM> may determine tension of the belt and monitor the tension and/or the magnitude of vibration present on the belt as the motor executes the excitation profile. Changes in the magnitude of vibration or tension in the belt correspond to dynamic variation or stretch of the belt. The motor controller <NUM> may monitor the changes in the magnitude of vibration or tension in the belt and generate a notification if the changes exceed a predefined threshold.

The frequency of some vibration signals is static and does not change with rotational speed of the rotor. Other vibration signals are dynamic and are related to the rotational speed of the motor. Identifying the source of a dynamic vibration may require rotating the vibration signals to a reference frame that is synchronous with the rotational speed and direction of the rotor. It is, therefore, another aspect of the invention that the motor controller <NUM> is configured to sample a feedback signal corresponding to an angular position and/or and angular speed of the rotor. The feedback signal may be generated by a position feedback sensor <NUM>, such as an encoder, resolver, or the like, operatively coupled to the motor <NUM>. The position or speed feedback signal may be sampled in tandem with sampling the feedback signal corresponding to vibration. Further, the signals may be time stamped with reference to a unified time reference to allow subsequent processing and detection of causes of vibration in the controller. Sampling the position or speed feedback signal in tandem with sampling the feedback signal corresponding to vibration allows the motor controller <NUM> to compare the magnitude of vibration or tension to the rotational speed of the rotor and also to convert the vibration signal to a reference frame that is synchronous with the rotational speed and direction of the rotor. Thus, the position or speed feedback signal allows the motor controller <NUM> to determine dynamic operating characteristics of the belt-driven system.

The motor controller <NUM> is operative to maintain a record of operating conditions over time. The log of operating conditions includes tension measurements, magnitudes of vibration, generation of notifications for any specific operating condition, or a combination thereof. The log may be used to detect changes in the belt tension over the operating life of the motor/load due to natural wear (stretch) of the belt and to alert users to readjust the tension in the belt to prevent premature failure of belt due to inadequate tension.

It is further contemplated that the log may be used to determine a remaining useful life of a belt in the belt-driven system. Some level of vibration may be acceptable or unavoidable in the system. The motor controller <NUM> may monitor the magnitude of vibration over time to determine an expected amount of wear on the belt. The memory device <NUM> of the motor controller <NUM> may include, for example, a look up table that corresponds a level of magnitude of vibration to a level of wear in a belt. As the magnitude of vibration or tension present on the belt varies over time the motor controller <NUM> determines the remaining useful life of the belt and generates a notification for maintenance personnel indicating when the belt needs to be replaced.

Claim 1:
A system for monitoring operation of drive members in a belt-driven system, comprising:
at least one sensor (<NUM>) configured to generate a signal corresponding to a vibration present in a motor (<NUM>) in the belt-driven system, wherein the motor is connected to and is operative to drive a belt, and wherein the at least one sensor is mounted within a housing of the motor, on the motor or on a structural member to which the motor is mounted; and
a motor controller (<NUM>) configured to control operation of the motor, the motor controller including:
an input (<NUM>) configured to receive the signal corresponding to the vibration present in the motor from the at least one sensor;
a memory device (<NUM>) operative to store a plurality of configuration parameters and a plurality of instructions; and
a processor (<NUM>) configured to execute the plurality of instructions to:
receive the signal from the at least one sensor corresponding to the vibration present in the motor, and
determine a tension present on the belt as a function of the signal corresponding to the vibration present in the motor.