WO2015116161A1

WO2015116161A1 - Predictive maintenance notifications based on motor voltage and motor current

Info

Publication number: WO2015116161A1
Application number: PCT/US2014/014137
Authority: WO
Inventors: Emilio LOPEZ MATOS; Fernando BAYONA ALCOLEA; Bhishma HERNANDEZ MARTINEZ
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2014-01-31
Filing date: 2014-01-31
Publication date: 2015-08-06

Abstract

In examples provided herein, a voltage circuit is to be coupled in parallel with a motor to identify a motor voltage. A current circuit is to be coupled in series with the motor to identify a motor current that is to pass through the current circuit. The current circuit is to identify the motor current independently of the motor voltage identified by the voltage circuit. A controller is to provide a predictive maintenance notification based on a first status of the motor voltage and the motor current.

Description

PREDICTIVE MAINTENANCE NOTIFICATIONS BASED ON MOTOR VOLTAGE AND MOTOR CURRENT

BACKGROUND

[0001] A printer may be used to print in a high-productivity environment, where it is desirable to avoid halting print production. Keeping such printers working reliably may involve periodic/routine maintenance, which may cause the printer to be taken offline during the maintenance, and cause the printers to be subjected to maintenance that may not be necessary at the scheduled time.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0002] FIG. 1 is a block diagram of a device including a voltage circuit and a current circuit according to an example.

[0003] FIG. 2 is a block diagram of a device including a voltage circuit and a current circuit according to an example.

[0004] FIG. 3 is a chart of motor voltage and motor current over time, according to an example.

[0005] FIG. 4 is a flow chart based on providing a predictive maintenance notification according to an example.

[0006] FIG. 5 is a flow chart based on a maintenance routine according to an example.

DETAILED DESCRIPTION

[0007] In examples provided herein, a device may provide predictive notifications regarding a need for maintenance or other attention. Accordingly, a user does not need to attempt to anticipate when maintenance is needed, or apply routine maintenance regardless of a condition of the device. Predictive notifications may be based on identifying motor voltage and current independently. The device may predict whether a maintenance task is needed, and prevent damage to components by warning for service/replacements in advance. Accordingly, example devices may avoid stopping printer operations based on a predictive maintenance strategy, in contrast to a preventive maintenance schedule. Furthermore, examples may address maintenance needs on a custom basis, tailored to each situation at an installation site, regardless of the many environmental factors (duty cycle use, ambient temperature, humidity, etc.) that can cause actual maintenance needs to deviate from a set preventive maintenance schedule. Thus, example devices may avoid performing maintenance too frequently, and avoid excessive application of maintenance procedures. Conversely, examples may provide notifications when they are appropriate, without causing a user to ignore a routine maintenance message that may or may not yet apply, leading to user complacency and risk of missing legitimate issues and causing permanent damage and/or failure.

[0008] Examples may predict whether components should be serviced, greased, tightened, loosened, adjusted, re-seated, etc., or whether any mechanical part is nearing damage. Circuits may accurately measure voltage and current flowing through a motor, in both rotation directions, including current generated by the motor working like a generator, e.g., during a braking sequence, generating back-electromotive force (EMF) energy. Initial measurements may be taken (e.g., at the end of the manufacturing line) and stored in memory, enabling comparisons to measurements taken throughout the lifetime of the printer. The measured properties are proportional to mechanical friction, enabling the device to deduce mechanical parameters based on the electric measurements. Deviations of the measurements, compared to a brand new device, may be observed throughout the printer lifetime. Predictive maintenance notifications may react to conditions as they develop, saving maintenance costs, extending lifetimes of mechanical parts, avoiding downtime, and providing other benefits as compared to a preventive maintenance schedule.

[0009] FIG. 1 is a block diagram of a device 100 including a voltage circuit 1 10 and a current circuit 120 according to an example. The voltage circuit 1 10 is to identify a motor voltage 1 12, and the current circuit 120 is to identify a motor current 122. The controller 130 is to identify a first status 132 of the device 100, based on the motor voltage 1 12 and the motor current 122. The controller 130 may provide a predictive maintenance notification 136 based on the first status 132.

[0010] Measuring the motor voltage 1 12, at leads of the motor 102, and the motor current 122 flowing through the motor windings, independent of the motor voltage 1 12, enables the controller 130 to identify details of operation of the motor 102. The motor current 122 may be measured in both rotation directions of the motor 102, and it may be determined whether the motor is acting as a generator (braking). In an example, the controller 130 can detect the motor working like a generator based on the motor voltage 1 12 and motor current 122 having different signs, i.e., when motor voltage 1 12 is positive and motor current 122 is negative, or when motor voltage 1 12 is negative and motor current 122 is positive. It is possible to detect when these values have different signs, based on the independent measurements of the voltage circuit 1 10 and current circuit 120. The controller 130 may take measurements in real-time and/or over a period of time. The controller 130 may use the measured data to implement current limitation. Such features, and accuracy in measurements, also can improve short-circuit, open-circuit, and driver circuit fault detection.

[0011] Voltage circuit 1 10 and current circuit 120 may be based on various types of sensors, such as voltage dividers, shunt resistors, Hall Effect current sensors, and so on. The controller 130 may be a microprocessor, microcontroller, digital signal processor (DSP), field programmable gate array (FPGA), and so on. The controller 130 is to determine whether the device 100 is operating based on a first status 132. For example, the first status 132 may correspond with increased motor current 122 consistent with a need for lubrication. Accordingly, controller 130 may provide predictive maintenance notification 136, to warn a user that early maintenance of the mechanical subsystem may be needed. The notification 136 may be provided when actually needed, without being based on a preventive maintenance approach having fixed periodic intervals.

[0012] High accuracy is achievable by including two circuits, to measure the motor voltage 1 12 applied to the motor leads, and to measure motor current 122 flowing through the motor windings. In an example, the motor voltage 1 12 and the motor current 122 may be measured simultaneously. Device 100 does not merely use the motor voltage 1 12 alone to indirectly infer a motor current. Instead, the device 100 may use measurements of motor current 122 together with motor voltage 1 12 to obtain highly accurate and precise results. Thus, controller 130 can identify precisely the moment at which the motor 102 changes from working like a motor being powered to working like a generator.

[0013] Motor 102 may include various types of motors, and may include motors specific to printers. In an example, motor 102 may be a carriage motor, a paper load motor, a paper advance motor, etc. Notifications, such as predictive maintenance notification 136, may be provided by controller 130 as tailored to various different types of applications associated with the corresponding type of motor 102. Motor 102 may be of a type that is a continuous rotation motor (e.g., in contrast to a stepper motor). A continuous rotation direct current (DC) motor can have varying speed based on application of a Pulsed Width Modulated (PWM) signal. The PWM signal may have its duty cycle varied to change speed, and is not confined to a series of discrete steps, in contrast to a stepper motor. Accordingly, circuits 1 10, 120 to measure continuous motors are more accurate and may operate according to a closed loop, in contrast to circuits to measure stepper motors (e.g., open loop). In particular, a continuous direct current motor may serve as a carriage motor of a large format printer, unlike a small printer that may accommodate a stepper motor.

[0014] FIG. 2 is a block diagram of a device 200 including a voltage circuit 210 and a current circuit 220 according to an example. A drive circuit 204 is to drive the motor 202. The voltage circuit 210 is to identify a motor voltage, and includes a voltage divider 214. A first analog-to-digital converter (ADC) couples output from the voltage circuit 210 to the controller 230. The current circuit 220 is to identify a motor current, and includes a shunt resistor 224, amplifier 226, voltage reference 260, and filter 228. A second analog-to-digital converter (ADC) couples output from the current circuit 220 to the controller 230. The controller 230 is to identify a first status 232 and a second status 234 of the device 200, based on output from the voltage circuit 210 and the current circuit 220. The controller 230 may provide a predictive maintenance notification 236 and an error notification 238, based on the first status 232 and/or the second status 234.

[0015] The drive circuit 204 may be a circuit to provide current and voltage to the motor 202. An H-bridge is shown as the drive circuit 204, capable of driving the motor 202 in both rotation directions. The drive circuit 204 may be powered from a high voltage rail V1 . In general, V1 » V2, where V2 is a power supply voltage rail for logic control. In an example, V1 = 42 Volts, and V2 = 5 Volts. The H-bridge drive circuit 204 contains four switches Q1 , Q2, Q3, and Q4. The switches may be transistors, such as metal-oxide-semiconductor field-effect transistors (MOSFETs) driven by pulse-width modulation (PWM) signals, which may be generated by the controller 230. The motor 202 may be connected to the drive circuit 204 between Q1 -Q4 and Q2-Q3. The shunt resistor 224 is coupled in series with the motor 202 to directly experience the current passing through the motor 202. The current circuit 220 may measure a voltage drop, even an extremely small amount, across the shunt resistor 224 directly with high accuracy, based on amplifier 226, without a need to indirectly infer a motor current based on a motor voltage across the leads of the motor 202.

[0016] The voltage circuit 210 is to identify electric voltage at the DC motor leads, based on two combined voltage dividers and first ADC 240. The various components of the first ADC 240 may be embedded into a microcontroller, Application Specific Integrated Circuit (ASIC), or other component type. ADCs 240, 242 may be provided by a microcontroller, microprocessor, ASIC, or other components capable of ADC functionality. The controller 230 may receive the output from the ADCs 240, 242, and convert to proper units (e.g., volts and amps) corresponding to the desired measurement of their sources.

[0017] The current circuit 220 is to identify the motor current flowing through the motor windings of the, e.g., DC motor 202, based on shunt resistor 224. The current circuit 220 also may include amplifier 226. In an example, amplifier 226 is an instrumentation amplifier having a high Common Mode Rejection Ratio (CMRR). Output is read by a second ADC 242, different from the first ADC 240 associated with obtaining a motor voltage measurement. Thus, measurement by the current circuit 220 is in contrast to a low-side current measurement that might be taken at the base of the drive circuit 204 (which would not detect current when the motor is working as a generator, due to the switching configuration of the H-bridge drive circuit 204). In contrast, the current circuit 220 measures a high-side of the device 200, obtaining high common mode voltage values at the shunt resistor 224 (the differential voltage drop between resistor leads may be small, e.g., 42.000 V at one lead and 41 .920 V at the other when flowing 10 Amps). This high-side current measurement enables measuring currents through the motor windings, regardless of rotating direction, and regardless of whether the motor 202 is rotating as a generator (in either direction). When working like a generator, current would not typically flow back to ground at the base of the H-bridge drive circuit 204. Thus, a low-side current measurement taken there may miss such information, in contrast to the high-side current circuit 220 having direct access to motor current.

[0018] The shunt resistor 224 is connected in series with windings of the motor 202, and may be chosen to have a low resistance on the order of milliohms (e.g., 0.008 Ohms), along with a high accuracy (e.g., 1 %). In an example, the shunt resistor is a discrete, high precision, resistor. Voltage drop across the shunt resistor 224 is correspondingly very low, and is to be amplified. Amplification may be used while rejecting as much circuit noise as practical. Hence, the resistor is connected to a high CMRR instrumentation amplifier block 226, having enough gain (G) to adapt the voltage drop to a dynamic range of the second ADC 242. The amplifier 226 may be chosen to support bidirectional current measurement, to identify the motor current regardless of in which direction and/or mode the motor 202 is operating.

[0019] The sensitivity of the shunt resistor 224 is such that layout of the device 200, e.g., based on a printed circuit board (PCB) layout, can affect the shunt resistor 224. Thus, the PCB layout may accommodate the principle of avoiding electrical noise, based on careful alignment of the electrical traces.

[0020] The amplifier 226 may be an instrumentation amplifier, or other type of amplifier having a high CMRR. In an example, the amplifier 226 may be formed by a plurality of operational amplifiers integrated in a monolithic integrated circuit. The amplifier 226 may be associated with a specific, low offset input voltage, and other desired characteristics consistent with principles described herein. The amplifier 226 may be coupled to a voltage reference.

[0021] The voltage reference 260 is to facilitate bidirectional current measurement by the amplifier 226. The amplifier may include a voltage reference 260 (such as V2/2), which is received at an offset input of the amplifier 226. When the motor is not running (e.g., motor current is 0 amps), amplifier output will be half of the dynamic range (V2/2 volts), based on the voltage reference 260. For example, a power supply of V2 = 5 volts will result in an offset voltage of 2.5 volts under these conditions. This offset is generated by a stable voltage reference 260, which includes temperature compensation to avoid temperature deviation, and stability against V2 voltage drops. The reference voltage 260 may be provided as an integrated circuit.

[0022] Using a voltage reference 260 of 2.5 V, the amplifier 226 may be operated from zero to 5 V. Furthermore, the range of amplifier output is indicative of which direction the motor current is flowing, in view of the voltage reference 260. For example, an amplifier 226 output value between 2.5 V and 5 V indicates that the current measured at the shunt resistor is flowing in a first direction. If the value obtained is between 0 V and 2.5 V, the motor current is flowing in the other direction. Thus, the offset is associated with measuring the bipolar nature of the motor current (e.g., having two directions), and capturing the value and the direction. [0023] The filter 228 is coupled to receive an output of the amplifier 226. The filter 228 is shown as a low pass filter, to reject high frequency noise (e.g., that comes from the PWM switching signals for the switches in the drive circuit). The filter 228 may be a second-order active low-pass filter. In an example, the active filter may be implemented based on an operational amplifier, in a Sallen- Key second-order topology, although other low-pass filters may be used.

[0024] The controller 230 may identify first status 232 and second status 234. In an example, the first status 232 may be whether motor current has risen above nominal values by an appreciable amount corresponding to a first threshold where lubrication may be needed. The second status 234 may be whether motor current has risen above nominal values by a large amount corresponding to a second threshold where damage is likely. The controller 230 may provide the predictive maintenance notification 236, to warn the user, based on reaching the first threshold. The controller 230 may provide the error notification 238 based on reaching the second threshold, and may stop the printer 200 based on predicting a malfunction, to avoid breakage. The controller 230 is coupled to non-volatile memory 250, which may be used to store various measurements and other information. The controller 230 and memory 250 may be part of a main engine of a printer, such as the printer engine where the controller 230 and memory 250 may be based. In an example, the controller 230, memory 250, and other various components/circuits may be housed in the same circuit board. In an alternate example, the printer engine (controller 230 and memory 250) may be housed on one board, and the printer mechatronics (circuit components, motor) may be housed on another separate board. Other such arrangements are possible.

[0025] Accordingly, device 200 enables high accuracy and precision, based on the low-noise amplifier 226 and filter 228. Once the motor voltage at the motor 202 leads is read, and the motor current flowing through the motor 202 windings is measured and conditioned, the information is ready to be processed by the printer controller 230. The controller may perform a routine for printer carriage maintenance. [0026] FIG. 3 is a chart 300 of motor voltage 312 and motor current 322 over time, according to an example. Chart 300 also shows values for power supply voltage rail 360. Chart 300 is identified by first region 370, second region 372, third region 374, fourth region 376, and fifth region 378.

[0027] The motor current 322 is shown initially peaking at first region 370. The peak in motor current 322 corresponds with motor acceleration. The approximately constant motor current in the second region 372 corresponds to a constant motor speed (e.g., for constant speed of travel for a printer carriage). Third region 374 illustrates a decrease in motor current 322, corresponding to motor deceleration, followed by fourth region 376 where motor current 322 rises but motor voltage 312 falls. Thus, fourth region 376 corresponds to the motor working like a generator, e.g., during braking (where motor current 322 rises back up to a positive value, and motor voltage 312 remains negative). Thus, the different signs (positive, negates) of the motor voltage 312 and motor current 322 indicate that the motor is working like a generator.

[0028] In an example, FIG. 3 may represent a carriage motor of a printer. In the second region 372, the motor current 322 is approximately steady at around 2 amps, corresponding to a slew of the printer carriage movement, when the carriage is moving from one side of the printer to the other at a constant speed to lay down ink on the page. The first and last parts of the movement are the acceleration and deceleration, respectively. When decelerating (braking), with a high load current, back-EMF will appear as shown by chart 300.

[0029] The slew may be measured and correlated, to enable a printer controller to identify whether a threshold is met, and/or if a notification or other action is needed. Chart 300 indicates that slew corresponds to approximately 2 amps, which is a motor current value that may be observed at initial measurement of the motor, e.g., on the day of manufacturing of the printer. During slew (the second region 372), the motor voltage corresponds to approximately 24 volts.

[0030] After the passage of time during which the printer is used, the slew value at the second region 372 may show a motor current of approximately 4 amps, e.g., when the printer is in use at the customer site. This may represent the motor encountering additional resistance in attempting to move the carriage, perhaps caused by wear or accumulation of debris etc. Upon measuring that motor current, the printer controller can determine that there is an issue in view of the motor current reaching a threshold, e.g., 4 amps. Accordingly, the controller may determine that the printer is operating according to a first status, corresponding to a predictive maintenance notification. That notification may indicate that that printer needs to be checked, that lubrication is needed, or other maintenance should be performed to avoid the operation that is causing the behavior. The maintenance notification may be informative, such as indicating that lubrication is needed, and that the motor current is deviating from its initial value by 2 amps (alternatively, deviating by 100%, or other informative numerical value). It is possible that the printer may tolerate a much higher motor current without damaging itself, but the printer may provide the notification at this pre-damage stage to allow the maintenance to be performed. As the motor current increases, additional thresholds/statuses may be met, resulting in additional notifications. If the motor current reaches a high enough value, (e.g., 5 amps), the printer may halt itself to avoid damage, and inform the user with an error notification and operate in a second status.

[0031] The notifications may be provided when actually needed, predictively signaling to the user that there is a high level of confidence that there is a legitimate issue that need attention. Accordingly, the user is freed from a need to blindly perform regular preventive maintenance, regardless of whether it is actually needed (e.g., cleaning the printer after every 72 hours of operation and/or hundreds of pages). Predictive notifications, based on identifying independent behavior of the motor current and motor voltage, provide a freedom for the user to avoid unnecessary preventive maintenance, thereby optimizing maintenance costs and enjoying maximum uptime and productivity by performing maintenance at times when there is a legitimate need for it. The thresholds of 4 amps and 2 amps provided above are just example parameters, and may be varied as desired (e.g., based on user preference, trends in printer behavior/reliability, and so on). In an alternate example, 2.3 amps may be taken as the initial baseline/nominal value for the motor current, and 3 amps may be used for the first threshold of predictive notification, and 5 amps may be a second threshold where the controller halts the printer and gives an error notification to avoid costly damage to the printer. The motor current and motor voltage are related to mechanical parameters, and affected in generally predictable ways according to known values of friction, inertia, and the like. Such values are correlated to the motor voltage and motor current for a DC motor in a device/printer.

[0032] A printer controller may rely on additional information, besides the motor voltage and the motor current, when identifying printer behavior. The voltage rail 360 is available for monitoring, and is a voltage corresponding to a supply from a printer power supply unit (PSU). The value for the voltage rail 360 shows an increase corresponding to times when the motor works like a generator, e.g., at fourth region 376 and fifth region 378. The increased value for voltage rail 360 is caused by energy from the motor's back-EMF associated with working like a generator. Thus, the controller also may monitor the voltage rail 360 to determine motor behavior, and may use the voltage rail 360 to fine- tune voltage values. More specifically, the nominal value of the voltage rail 360 may be indicated as being 42 volts, but the actual measurement of the voltage rail may be slightly different (e.g., 41 .9 V, 42.1 V, etc.). Using the actual, measured value enables the controller to operate with additional accuracy. Thus, the controller may use the steady state value of the voltage rail 360, and use that value as a parameter for determining other values (such as motor voltage and motor current, that may be dependent on and affected by the value of the voltage rail 360). Although indicated as 42V, the voltage rail 360 may use other values such as 30 V, 35 V, etc.

[0033] Accordingly, the motor voltage 312 and motor current 322 (and voltage rail 360) as measured by circuits described herein, provide accurate and precise information that is usable by the controller to determine specific motor behavior, allowing for insights not available in the absence of separate motor voltage and motor current measurements (e.g., when motor current is simply derived from motor voltage, and not measured independently). [0034] Referring to Figures 4 and 5, flow diagrams are illustrated in accordance with various examples of the present disclosure. The flow diagrams represent processes that may be utilized in conjunction with various systems and devices as discussed with reference to the preceding figures. While illustrated in a particular order, the disclosure is not intended to be so limited. Rather, it is expressly contemplated that various processes may occur in different orders and/or simultaneously with other processes than those illustrated.

[0035] FIG. 4 is a flow chart 400 based on providing a predictive maintenance notification according to an example. In block 410, a motor voltage is identified based on a voltage circuit coupled in parallel with a motor. In an example, the voltage circuit identifies a voltage across the leads of the motor, based on the use of a voltage divider. In block 420, a motor current is identified, based on a current circuit coupled in series with the motor. The motor current is to pass through the current circuit, and the motor current is identified independent of identifying the motor voltage by the voltage circuit. For example, the current circuit includes a shunt resistor that is coupled in series with motor windings of the motor. In block 430, a controller is to provide a predictive maintenance notification based on a first status of the motor voltage and the motor current. For example, the controller includes a plurality of notifications and statuses (e.g., associated with thresholds), and predicts when to provide a notification based on actual conditions measured at the printer, in contrast to a blind imposition of a routine maintenance schedule.

[0036] FIG. 5 is a flow chart 500 based on a maintenance routine according to an example. Features described herein enable example devices to provide guidance when to perform maintenance, based on motor voltages and motor currents stored and compared with initial values. Controllers may perform the techniques with consistency and automatically, without needing user intervention, on a predictive basis (for instance, every time the printer is initialized).

[0037] Flow starts at block 510. In block 515, it is determined whether an initial test is to be performed. For example, a device/printer may perform an initial test at the end of the printer line manufacturing (e.g., once in the printer life at the end of the line manufacturing at the factory). Such values may be stored in non-volatile memory of the printer, and may be used to check manufactured printers against each other for quality control/consistency during and after manufacturing, to see if the values are representative of many printers in a manufacturing population. If the printer is running an initial test, flow proceeds to block 520. In block 520, the controller measures an average initial current and an average motor reference voltage. In an alternate example, the printer may include a table of pre-populated values corresponding to parameters, thereby bypassing a need to specifically obtain the values by measuring them. However, the initial measurements are very precise and affected greatly by the unique printer characteristics of a printer, which may be unique down to a single printer's variation from default nominal values for various parameters. In an example, at the first start-up of the printer at the manufacturing line, the printer's controller may perform a first measurement of the motor voltage (V_MOT REF AVE) and motor current (l₀ AVE) present during a carriage movement. These measurements may be computed based on average values during multiple test movements. In block 525, VMOT REF AVE and I_O AVE are stored. These measurements may be stored in a non-volatile memory, to be available for reference during a lifetime of the printer. These measurements may be used as a reference of how the new printer behaved when it exited the manufacturing line. The initial test may be performed at any location/time, and is not limited to a place of manufacture. In an example, the printer may be set up at an onsite installation, and upon power-on, will perform an initial test. In an alternate example, the printer may allow for an initial test to be performed on demand, regardless of whether the printer has already been turned on. For example, if a printer is turned on while having a misconfiguration, the initial measurements may be incorrect until the misconfiguration may be corrected and the initial test re-run. The initial measurements may be compared throughout the printer's life. If the printer identifies deviations from these initial measurement values, the printer controller may provide a notification such as a system error/warning to the user during use, advising the performance of maintenance or even halting printing. After storing the measurements at block 525, flow ends at block 530.

[0038] If, at block 515, the printer is not performing an initial test (e.g., already operating on site), flow proceeds to block 535. In an example, this "No" branch of block 515 may be run during the life of printer, as part of the predictive maintenance routine to establish reference value(s), while still being able to refer back to initial values from the initial test that are stored in memory. In block 535, the printer carriage is moved. For example, the carriage is moved at approximately constant velocity. In block 540, the slew current is recorded as a reference. This value may between iterations, due to friction or other linear and/or non-linear effects, including wear. At block 545, blocks 535, 540, and 545 are repeated N times. In an example, blocks 535, 540, 545 enable a printer to record reference measurements while the printer motor is moving. In an example, the printer motor is a carriage motor that moves the inkjet printer carriage left to right, repeating N = 10 times, for example. The value for N may be adjusted based on the printer characteristics and expectation of an acceptable number of iterations to approach a reliable reference measurement. In an example, for the life of the printer, when the printer starts up, it may perform a new measurement, to average the motor voltage and motor current for N samples. These measurements may be taken while the printer is performing carriage movement tests, for example. In block 550, _VE is computed. V_AVE also may be computed. In block 555, it is determined whether an average measured value (UV_E, V_AV_E, or others) is within an error percentage of the corresponding initial value (e.g., I₀). Thus, if the measured value is not within the initial value l₀ plus or minus an allowable error value E, then the printer carriage is out of specifications, and flow proceeds to block 560. In block 560, the controller determines that the printer carriage (or other printer component, such as paper loader, or whatever component corresponds with the printer motor in question) is out of spec. In an example, a measurement of the motor voltage is performed, while moving the carriage (or other corresponding printer function). Attempting to actuate the component in question is done to confirm whether there is a motor issue. If the component moves successfully, there is no motor issue. In block 565, it is determined whether the motor voltage is greater than the reference motor voltage. If not, then the controller can deduce that there is a motor issue that is to be solved first, and flow proceeds to block 570. This situation may occur, for example, when providing a voltage value, the current flowing is greater than before. This indicates that the motor windings have less resistance, therefore the motor is almost burned out, but it is unlikely to be caused by a mechanical issue. In block 575, a predictive maintenance notification is provided, and flow ends. If, in block 565, it is determined that the motor voltage is greater than the reference motor voltage, flow proceeds to block 580. To arrive at this branch of the flow diagram, at block 580, the conditions may be that the motor current exceeds l₀, and the motor voltage exceeds the reference V_MOT REF, SO the controller may generate a notification asking for mechanical maintenance. The need for mechanical maintenance has been inferred from the situation that both mechanical parameters (motor current and motor voltage) have changed, e.g., the pair may have kept the same expected proportion.

[0039] Over time, if such maintenance tasks are not performed after many warning occurrences (which may be counted and stored as a notification iteration value), and if the measured parameters continue to worsen with new measurements, the controller may halt the printer and output a system error, preventing damage/permanent failure in a mechanical part. Thus, in block 585, an error notification may be provided and/or the printer may be halted. Accordingly, even if no singular halt event occurs, the device may be halted in view of an accumulation of disregarded notifications, or other accumulated deviations etc. Flow ends at block 595. If, in block 555 it was determined that the measured value I_AVE (or other measured value) was within range of the initial value(s), then flow proceeds to block 590. In block 590, the printer is OK, and flow ends at block 595.

[0040] Examples provided herein (e.g., methods) may be implemented in hardware, software, or a combination of both. Example systems (e.g., printers) can include a controller/processor and memory resources for executing instructions stored in a tangible non-transitory medium (e.g., volatile memory, non-volatile memory, and/or computer readable media). Non-transitory computer-readable medium can be tangible and have computer-readable instructions stored thereon that are executable by a processor to implement examples according to the present disclosure.

[0041] An example system can include and/or receive a tangible non- transitory computer-readable medium storing a set of computer-readable instructions (e.g., software). As used herein, the controller/processor can include one or a plurality of processors such as in a parallel processing system. The memory can include memory addressable by the processor for execution of computer readable instructions. The computer readable medium can include volatile and/or non-volatile memory such as a random access memory ("RAM"), magnetic memory such as a hard disk, floppy disk, and/or tape memory, a solid state drive ("SSD"), flash memory, phase change memory, and so on.

Claims

WHAT IS CLAIMED IS:

1 . A device comprising:

a voltage circuit to be coupled in parallel with a motor to identify a motor voltage;

a current circuit to be coupled in series with the motor to identify a motor current that is to pass through the current circuit, wherein the current circuit is to identify the motor current independently of the motor voltage identified by the voltage circuit; and

a controller to provide a predictive maintenance notification based on a first status of the motor voltage and the motor current.

2. The device of claim 1 , wherein the controller is to halt operation of the motor and provide an error notification based on a second status of the motor voltage and the motor current.

3. The device of claim 1 , further comprising an H-bridge coupled to the current circuit to provide power to the motor through the current circuit, wherein the current circuit is to identify the motor current regardless of a status of the H-bridge, including whether the motor is rotating in either direction, whether the motor is to consume the motor current, and whether the motor is working as a generator to generate the motor current.

4. The device of claim 1 , wherein the voltage circuit includes a voltage divider to monitor the motor voltage.

5. The device of claim 1 , wherein the controller is to identify that the motor is working as a generator, based on the voltage circuit identifying the motor voltage having a first sign, among positive and negative, that is different from a second sign, identified by the current circuit and corresponding to the motor current; wherein the predictive maintenance notification is based on the identification of the motor working as a generator.

6. The device of claim 1 , wherein the motor is a continuous rotation direct current (DC) motor, and the controller is to monitor the motor voltage and the motor current based on a closed loop arrangement associated with assessing rotational characteristics of the continuous rotation DC motor.

7. The device of claim 1 , wherein the current circuit further comprises an instrumentation amplifier to reject noise and amplify a resulting voltage.

8. The device of claim 7, further comprising an analog-to-digital converter (ADC) coupled to the instrumentation amplifier, wherein the instrumentation amplifier supports bidirectional current measurement and is associated with a gain value to adapt the resulting voltage to a dynamic range of the ADC.

9. The device of claim 7, wherein the current circuit further comprises a stable voltage reference coupled to the instrumentation amplifier, wherein the stable voltage reference includes temperature compensation.

10. The device of claim 7, further comprising a low pass filter coupled to the instrumentation amplifier to reject high frequency noise.

1 1 . A printer comprising:

a printer motor;

a voltage circuit coupled in parallel with the printer motor to identify a motor voltage;

a current circuit coupled in series with the printer motor to identify a motor current that is to pass through the current circuit, wherein the current circuit is to identify the motor current independently of the motor voltage identified by the voltage circuit; and

12. The printer of claim 1 1 , wherein the controller is to identify that the motor current corresponds with printer motor operation of a carriage during printer carriage slew, and provide a maintenance notification corresponding to lubrication being needed, based on the motor current exceeding a first threshold.

13. The printer of claim 1 1 , wherein the controller is to perform a plurality of measurements of the motor voltage and motor current at printer startup, based on movement tests, to determine an average motor voltage and motor current based on a plurality of sampled motor voltages and motor currents.

14. A method, comprising:

identifying a motor voltage based on a voltage circuit coupled in parallel with a motor;

identifying, based on a current circuit coupled in series with the motor, a motor current that is to pass through the current circuit, wherein the motor current is identified independent of identifying the motor voltage by the voltage circuit; and

providing, by a controller, a predictive maintenance notification based on a first status of the motor voltage and the motor current.

15. The method of claim 14, further comprising:

identifying an initial motor voltage and initial motor current based on an initial motor test; and

comparing the identified motor voltage and identified motor current to the initial motor voltage and initial motor current, to determine whether the first status is met.