WO2017162307A1

WO2017162307A1 - Fault detection

Info

Publication number: WO2017162307A1
Application number: PCT/EP2016/056674
Authority: WO
Inventors: David SORIANO FOSAS; Vicente GRANADOS ASENSIO; Juan Manuel ZAMORANO
Original assignee: Hewlett-Packard Development Company L.P.
Priority date: 2016-03-24
Filing date: 2016-03-24
Publication date: 2017-09-28

Abstract

Certain examples described herein relate to fault detection. In response to receipt of a status signal over a first communication channel indicating that a device comprising an element satisfies an operability condition, a first control signal is outputted via a second communication channel to the device, the second communication channel being separate from the first communication channel. The first control signal comprises an instruction that the element be in an activated state. In the absence of receipt of the status signal on the first communication channel indicating that the device satisfies the operability condition, a second control signal is outputted via the second communication channel. The second control signal comprises an instruction that the element be in a deactivated state. In response to a subsequent absence of receipt of the status signal indicating that the device satisfies the operability condition, an occurrence of a fault is detected.

Description

FAULT DETECTION

BACKGROUND

[0001] Many systems include potentially hazardous elements. Such systems include latex-based printers and 3D printers, which may use, for example, high power heating elements for curing and fusion processes. Design constraints may lead to potentially hazardous elements be physically placed in user-accessible locations. The placing of potentially hazardous elements in user-accessible locations may be performed in accordance with particular safety regulations. Safety regulations may relate to providing mechanisms for robust fault detection, in order to minimize risk from potentially hazardous elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Various features of the present disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example only, features of the present disclosure, and wherein:

[0003] Figure 1 is a schematic illustration showing a fault detection system according to an example;

[0004] Figure 2 is a schematic illustration showing a fault detection system according to an example;

[0005] Figure 3 is a schematic illustration showing a fault detection system according to an example;

[0006] Figure 4 is a schematic illustration showing signaling channels used and events occurring during normal operation of a fault detection system versus time, according to an example;

[0007] Figure 5 is a table showing possible faults and resulting behavior in a system according to an example;

[0008] Figure 6 is a flow diagram showing a method of facilitating fault detection according to an example; [0009] Figure 7 is a flow diagram showing a method of facilitating fault detection according to an example;

[0010] Figure 8 is a signaling diagram showing a method of facilitating fault detection according to an example;

[0011] Figure 9 is a signaling diagram showing a method of facilitating fault detection according to an example;

[0012] Figure 10 is a signaling diagram showing a method of facilitating fault detection according to an example; and

[0013] Figure 1 1 is a schematic illustration showing a processor and a computer readable storage medium with instructions stored thereon according to an example.

DETAILED DESCRIPTION

[0014] In the following description, for purposes of explanation, numerous specific details of certain examples are set forth. Reference in the specification to "an example" or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least that one example, but not necessarily in other examples.

[0015] Certain examples provide a robust fault detection mechanism for safe operation in systems which comprise at least one element which can be controlled. The element could be, for example, a potentially hazardous element, e.g. an element that could potentially be hazardous to a user if the user should come into contact with the element when the element is in an activated state. The potential hazard may relate, for example, to a potential electrical hazard and/or a potential thermal hazard.

[0016] Certain examples provide a fault tolerant communication network in place of a single on/off wire. Tolerance against single faults and detectability in case of single failure may be provided. Consequently, physical configurations which would otherwise not be safely implementable may be provided. For example, a potentially hazardous element may be safely located in a user-accessible area.

[0017] Certain examples provide a reliable communication network between a device comprising a potentially hazardous element and a printing system. Certain examples provide an assurance that the potentially hazardous element cannot be enabled by a single fault in a communication channel between the printing system and the device during certain moments of time, for example when a cover is open, thus exposing a user to the potentially hazardous element. Certain examples enable remedial action to be taken upon detection of a fault. Certain examples reduce a risk that a potentially hazardous element may be improperly turned on or left in an activated state.

[0018] Certain examples provide a high level of thermal performance in paper- based printing systems. Many industrial printing systems, such as latex-based printing systems, involve drying and curing processes which produce a high temperature environment.

[0019] Certain examples enable the use of thermal ink-jet print heads in applications such as 3D printers. Such applications may involve maintaining a high operating temperature environment in user-accessible locations.

[0020] Figure 1 shows a fault detection system 100 according to an example. The fault detection system 100 may, in some examples, be incorporated at least in part in a printing system. The printing system may, for example, comprise a latex ink-based printer. In some examples, the fault detection system 100 may be incorporated at least in part in an additive manufacturing system, commonly known as a 3D printer. The fault detection system 100 may comprise further components, however these are omitted in the present description for ease of explanation.

[0021] The fault detection system 100 comprises a remote device 1 10. The remote device 1 10 comprises an element 120 and a remote controller 130. The remote controller 130 may comprise a processor 170 and a memory 175. The remote controller 130 may comprise at least once microcontroller. The fault detection system also comprises a host controller 140. The host controller 140 may comprise a processor 180 and a memory 185. The remote device 1 10 may be positioned remotely, in other words at a remote location, relative to the host controller 140. The remote device 1 10 may be arranged, for example, in a print zone. The host controller 140 may be arranged, for example, within a body of a printing system. In some examples, the host controller 140 is arranged within a computer control system for a printing system. In some examples, the fault detection system 100 comprises a plurality of remote devices 1 10. [0022] The remote controller 130 is communicatively coupled to the host controller 140 via a first communication channel 150 and a second communication channel 1 60. The first communication channel 150 is separate from the second communication channel 1 60. The first communication channel 150 and/or the second communication channel 160 may be wired channels. In other words, the first communication channel 150 and the second communication channel 1 60 may comprise at least one wire. In some examples, the first communication channel 150 and/or the second communication channel 1 60 comprise at least one wireless component. The first communication channel 150 and/or the second communication channel 1 60 may be arranged to enable the remote controller 130 and the host controller 140 to transmit and receive signals and/or data. In some examples, the first communication channel 150 and the second communication channel 160 are at least partially arranged within a shared cable. The shared cable may be arranged to connect the host controller 140 with the remote device 1 10 and/or the remote controller 130. The shared cable may additionally comprise at least one further channel. The at least one further channel may, for example, comprise a ground channel. The at least one further channel may, for example, comprise a power supply channel. In some examples, the first communication channel 150 and the second communication channel 1 60 are at least partially arranged to share an interconnect system, the interconnect system being arranged to connect the host controller 140 with the remote device 1 10 and/or the remote controller 130. The interconnect system may comprise the at least one shared cable.

[0023] The element 120 may comprise any element or component which has an on/off control. The element 120 may comprise a potentially hazardous element. The elements may, for example, be associated with high voltages and/or with high temperatures. The element 120 may be, for example, a high power heating element. High power heating elements may be used in many printing systems for curing or fusion processes, for example. Due to their function, such high power heating elements may be located near to a print zone, where a user may have frequent access. Consequently, the location of high power heating elements in printing systems may present a safety risk. The element 120 may be configured to receive at least one control signal from the remote controller 130. In some examples, the element 120 is configured to receive a binary-type on/off control signal. In some examples, the element 120 is configured to receive a control signal indicating a particular output power.

[0024] In the present example, the remote controller 130 is configured to determine whether the remote device 1 10 conforms to an operability criterion. In some examples, the operability criterion relates to a state of the element 120. The operability criterion may relate to a state of at least one component of the remote device 1 10 other than the element, according to some examples. In some examples, the operability criterion relates to a state of the remote device 1 10 as a whole. The remote controller 130 is configured to transmit at least one status signal via the first communication channel 150. The at least one status signal comprises an indication of whether the remote device 1 10 conforms to the operability criterion. The at least one status signal may, according to one example, comprise an indication of whether the remote device 1 10 passes an operability test performed by the remote controller 130.

[0025] In the present example, the host controller 140 is configured to monitor the first communication channel 150 for a status signal from the remote device 1 10. In response to receipt of a status signal on the first communication channel 150 indicating that the remote device 1 10 conforms to the operability criterion, the host controller 140 is configured to transmit a first control signal via the second communication channel 1 60 to the remote device 1 10. The first control signal indicates a request that the element 120 be in an activated state. In the absence of receipt of a status signal on the first communication channel 150 indicating that the remote device 1 10 conforms to the operability criterion, the host controller 140 is configured to transmit a second control signal via the second communication channel 1 60 to the remote device 1 10. The second control signal indicates a request that the element 120 be in a deactivated state. In response to transmitting the second control signal and a subsequent absence of receipt of a status signal indicating that the remote device conforms to the operability condition, the host controller 140 is configured to detect an incidence of a fault. In some examples, the host controller 140 is configured to determine a possibility of a fault based on monitoring the first communication channel 150. A possibility of a fault may be determined in response to absence of receipt of a status signal on the first communication channel 150 indicating that the remote device 1 10 conforms to the operability criterion. The host controller 140 may be configured to detect an incidence of a fault in response to a determined possibility of a fault, transmitting the second control signal indicating a request that the element 120 be in a deactivated state, and a subsequent absence of receipt of a status signal indicating that the remote device conforms with the operability criterion.

[0026] In some examples, in response to receipt of a status signal indicating that the remote device 1 10 conforms to the operability criterion, the host controller 140 is configured to further transmit a second control signal via the second communication channel 160 to the remote device 1 10. The second control signal indicates a request that the element be in a deactivated state. In response to the further transmitting of the second control signal and a subsequent absence of receipt of a status signal indicating that the remote device 1 10 conforms to the operability criterion, the host controller 140 may be configured to detect an incidence of a fault.

[0027] In some examples, the remote controller 130 is configured to transmit at least one status signal via the first communication channel 150, the at least one status signal comprising an indication that the remote device 1 10 conforms to the operability criterion. In such examples, the absence of receipt at the host controller 140 of a status signal on the first communication channel 150 indicating that the remote device 1 10 conforms to the operability criterion may be due to a failure in the first communication channel 150. A failure in the first communication channel 150 may be related to a short circuit, according to some examples. In one example, the failure in the first communication channel 150 is related to the first communication channel 150 connecting with a ground channel. In another example, the failure in the first communication channel 150 is related to the first communication channel 150 connecting with a power channel. In a further example, the failure in the first communication channel 150 is related to the first communication channel 150 connecting with the second communication channel 1 60. In one example, the failure in the first communication channel 150 is related to a severing of the first communication channel 150, for example due to a wiring disconnection. The host controller 140 may be configured to determine a cause of the detected failure. The cause of the detected failure may be determined based on monitoring the first communication channel 150.

[0028] In some examples, the absence of receipt of a status signal on the first communication channel 150 indicating that the remote device 1 10 conforms to the operability criterion is due to a failure in the remote device 1 10. The failure in the remote device 1 10 may be related to the remote device 1 10 failing an operability test performed by the remote controller. The failure in the remote device 1 10 may, according to one example, be related to the inability of the remote controller 130 to properly perform an operability test on the remote device 1 10 in order to determine whether the remote device 1 10 conforms to an operability criterion. In another example, the failure in the remote device 1 10 may be related to the inability of the remote controller 130 to transmit a signal indicating whether the remote device 1 10 conforms to the operability criterion. In a further example, the failure in the remote device 1 10 may be related to a failure of the element 120. Other possible failures in the remote device 1 10 are envisaged but are not described for conciseness.

[0029] Figure 2 shows a fault detection system 200 according to an example. The fault detection system 200 comprises a host device 210 and a remote device 1 10. The remote device 1 10 corresponds to that shown in Figure 1 and comprises an element 120 and a remote controller 130. The host device 210 comprises a host controller 140, corresponding to that shown in Figure 1 . The host device 210 further comprises a power supplier 220, communicatively coupled to the host controller 140. The host device 140 is communicatively coupled to the remote device 1 10 via a first communication channel 150 and a second communication channel 1 60, similarly to those shown in Figure 1 .

[0030] In the present example, power is supplied to the remote device 1 10 via a third communication channel 230. The third communication channel 230 is separate from the first communication channel 150 and the second communication channel 160. In Figure 2, the power supplier 220 is configured to supply power to the remote device 1 10 via the third communication channel 230. The power supplier 220 may be a power source for the remote device 1 10, according to some examples. In some examples, the power supplier 220 may be a power regulator for the remote device 1 10. [0031] In the present example, the remote controller 130 is configured to determine whether the remote device 1 10 conforms to an operability criterion and to transmit at least one status signal via the first communication channel 150, the status signal comprising an indication of whether the remote device 1 10 conforms to the operability criterion. The host controller 140 is configured to monitor the first communication channel 150 for a status signal from the remote device 1 10. In the absence of receipt of a status signal on the first communication channel 150 indicating that the remote device 1 10 conforms to the operability condition, the host controller 140 is configured to transmit a control signal via the second communication channel 160. The control signal indicates a request that the element 120 be in a deactivated state. In response to transmitting the control signal and a subsequent absence of receipt of a status signal indicating that the remote device 1 10 conforms to the operability condition, the host controller 140 is configured to detect an incidence of a fault.

[0032] In the present example, in response to detecting the incidence of the fault, the host controller 140 is configured to cause a cessation of the power supplied to the remote device 1 10 via the third communication channel 230. In some examples, the host controller 140 causes the cessation of the power supplied to the remote device 1 10 by transmitting a power control signal to the power supplier 220. The power supplier 220 may be configured to terminate the power supplied to the remote device 1 10 via the third communication channel 230 in response to receiving the power control signal from the host controller 140. In one example, the power control signal may cause the power supplier 220 to be switched off. In other examples, the power control signal may cause the power supplier 220 to regulate the power supplied to the remote device 1 10.

[0033] In Figure 2, the power supplier 220 is arranged within the host device 210. In other examples, the power supplier 220 may be arranged externally to the host device 210, e.g. between the host device 210 and the remote device 1 10. Therefore, the cessation of the power supplied to the remote device 1 10 may occur between the host device 210 and the remote device 1 10.

[0034] In some examples, the remote device 1 10 and the host device 210 may comprise separate modules within a single device. In other examples the remote device 1 10 and the host device 210 may comprise separate modules within separate devices.

[0035] Figure 3 shows a fault detection system 300 according to an example. The fault detection system 300 comprises a remote device 1 10 as described above, the remote device comprising a remote controller 130 and an element 120. The fault detection system 300 further comprises a host device 210, the host device 210 comprising a host controller 140 and a power supplier 220, as described above. The host device 210 and the remote device 1 10 are communicatively coupled via a first communication channel 150, a second communication channel 160 and a third communication channel 230, as described above. In the present example, the first communication channel 150, the second communication channel 1 60 and the third communication channel 230 are at least partially arranged within a shared cable 360. In some examples, the third communication channel 230, used to supply and/or regulate power to the remote device 1 10, may be arranged within a separate cable. The shared cable 360 may include at least one further channel (not shown). The at least one further channel may comprise a ground line.

[0036] In the example shown in Figure 3, the host device 210 further comprises a watchdog unit 310. In other examples, the watchdog 310 forms part of the host controller 140. The watchdog 310 may be configured to monitor the first communication channel 150. In some examples, receiving a status signal on the first communication channel 150 indicating that the remote device 1 10 satisfies an operability condition causes the watchdog 310 to refresh (shown as "refresh" in Figure 3). In the absence of receipt of a status signal on the first communication channel 150 indicating that the remote device 1 10 satisfies the operability condition, the watchdog 310 may be prevented from refreshing and may, in consequence, be configured to perform at least one remedial action. In some examples, the watchdog 310 is configured to receive a control signal from the host controller 140. The control signal may comprise an instruction (shown as "disable" in Figure 3) to perform at least one remedial action. The control signal may be generated by the host controller 140 in response to an absence of receipt of a status signal indicating that the remote device 1 10 satisfies the operability condition, according to one example. The at least one remedial action performed by the watchdog 310 may comprise the generating of a system reset signal. The system reset signal may, for example, cause the power supplier 220 to be deactivated. In some examples, the system reset signal causes the power supplier 220 to terminate the power supplied to the remote device 1 10 via the third communication channel 230. In some examples, the system reset signal causes an interlock (not shown) to be activated. An interlock may comprise at least one device configured to prevent exposure to a hazard. The activation of the interlock may, for example, cause a prevention of user entry to the componentry of the remote device 1 10. An interlock may operate through use of one or more electromechanical switches, magnetic switches, sensors, actuators, etc. In other examples, the system reset signal causes at least one cooling fan (not shown) to be activated. The remedial action performed by the watchdog 310 enables the element 120, which may be a potentially hazardous element, to be made safe for user access to the device 1 10.

[0037] In the present example, the fault detection system 300 comprises metal- oxide semiconductor field-effect transistors (MOSFETs) 320, 330. The MOSFETs 320, 330 are arranged within the host device 210. The MOSFETs 320, 330 may be series high-voltage MOSFETs. In this example, a first MOSFET 320 is arranged on the first communication channel 150, and a second MOSFET 330 is arranged on the second communication channel 1 60. Further MOSFETs (not shown) may be incorporated into the fault detection system 300 in other examples. The fault detection system 300 may further comprise at least one buffer amplifier 340. The buffer amplifier 340 may be a voltage buffer or a current buffer, according to various examples. In this example, the buffer amplifier 340 is arranged on the second communication channel 160. In other examples, the buffer amplifier 340 may be arranged additionally or alternatively on the first communication channel 150. The MOSFETs 320, 330 and the buffer amplifier 340 isolate the internal signals of the host device 210 from potential high voltage short circuits occurring in the cable 360, which could otherwise damage or destroy the circuitry of the host device 210.

[0038] In the present example, the host device 210 comprises at least one pulldown resistor 350. In this example, the pull-down resistor 350 is arranged on the first communication channel 150. In other examples, the pull-down resistor 350 is arranged additionally or alternatively on the second communication channel 1 60. In some examples, the remote device 1 10 comprises at least one pull-down resistor. The pull-down resistor 350 may be connected to ground. The pull-down resistor 350 can enable a signal, e.g. a signal on the first communication channel 150, to be received at a valid logic level.

[0039] Figure 4 shows signaling channels used and events occurring 400 during normal operation of a fault detection system, such as the fault detection systems 100, 200, 300 described above, versus time (from left to right) according to an example. The channels and events depicted in Figure 4 are included for illustrative purposes only and are not to be seen as exhaustive.

[0040] Control channel 410 is an example of a channel used to transmit one or more control signals, for example via the second communication channel 160 from the host controller 140 to the remote controller 130. Initially, after the system is powered on, a constant logic level is transmitted on the control channel 410. To instruct the remote controller 130 to enable the element 120, a specific enable sequence is transmitted on the control channel 410. As shown in Figure 4, the enable sequence may comprise a series of logic changes separated by predetermined time periods, T1 , T2 and T3. The remote controller 130 may be configured such that only the specific enable sequence results in the element being activated. After transmitting the enable sequence on the control channel 410, a constant logic level is transmitted for the time period in which it is desired to keep the element in an activated state. To deactivate the element, a signal change is transmitted on the control channel 410. The signal change may be a signal drop, according to one example. In another example, the signal change is a signal increase.

[0041] Status channel 420 is an example of a channel used to transmit one or more status signals, for example via the first communication channel 150 from the remote controller 130 to the host controller 140. Initially, after the system is powered on, a constant logic level is transmitted on the status channel 420. When an operability test 450 is performed on the remote device 1 10 and such a test is passed, a signal change of pre-determined duration is transmitted on the status channel 420 to indicate that the remote device 1 10 has passed the operability test. In some examples, the operability test 450 and/or the transmitting the signal change on the status channel 420 may not occur during the same time period as the enable sequence being transmitted on the control channel 410. In some examples, the operability test 450 and/or the transmitting the signal change on the status channel 420 may not occur while the element is in an activated state. The operability test 450 may be performed periodically. In some examples, the operability test 450 may be performed by the remote controller 130 following the expiration of a predetermined time period.

[0042] ON/OFF channel 430 indicates whether the element is in an activated or a deactivated state at a particular instance in time. For example, once the enable sequence is received on the control channel 410, the remote controller 130 may transmit a control signal to the element to cause the element to be switched to being in an activated state. In response to the signal change after the enable sequence on the control channel 410, the remote controller 130 may transmit a control signal to the element 120 to cause the element to be switched to being in a deactivated state. In some examples, the element may be momentarily turned on and off during an operability test 450. In some examples, the operability test 450 may be performed without the element being turned on or off.

[0043] System nReset channel 440 is an example of a system reset signal generated by watchdog 310 and/or host controller 140. The System nReset channel 440 responds to a signal change on the status channel 420 indicating that the remote device 1 10 satisfies an operability criterion. If these characteristic signal changes on the status channel 420 are received, a constant logic level may be transmitted on the System nReset channel 440. In the absence of a signal on the status channel 420 indicating that the remote device 1 10 satisfies an operability criterion, a signal change on the System nReset channel 440 causes at least one remedial action to be taken. For example, a signal change on the System nReset channel 440 may cause the power supply to the remote device 1 10 to be terminated.

[0044] Figure 5 shows a table showing possible faults and resulting behavior in a fault detection system according to an example. The examples of possible faults and resulting behavior shown in Figure 5 are associated with the components of the fault detection systems 100, 200, 300 and from the signals 400 depicted in Figures 1 , 2 3 and 4, respectively, and described above. The table shown in Figure 5 is included for illustrative purposes only and is not to be seen as exhaustive. Other fault types and resulting behaviors are envisaged.

[0045] In Figure 5, failures 1 to 8 relate to faults in control signals as received via the second communication channel 1 60 by a remote device such as remote device 1 10 shown in Figure 1 . In other words, failures 1 to 8 relate to faults associated with the second communication channel. Failure 1 relates to a scenario in which a control signal comprising an instruction that an element be disabled is left floating. In this case, pull-down in the remote device 1 10 pulls the received signal down to a logic level indicating the correct disabled state. The element is therefore in a disabled state. Failure 2 relates to a scenario in which a control signal comprising an instruction that the element be enabled is left floating. In this case, pull-down in the remote device 1 10 pulls the received signal down to a logic level indicating a disabled state. The remote controller 130 cannot enable the element without the correct enable sequence. Therefore, the element remains in a disabled state. Failure 3 relates to a scenario in which a control signal comprising an instruction that an element be disabled is stuck at ground. In this case, the received signal is always zero. Therefore, the element is in a disabled state. Failure 4 relates to a scenario in which a control signal comprising an instruction that an element be enabled is stuck at ground. In this case, the received signal is zero. The remote controller 130 cannot enable the element without the correct enable sequence. Therefore, the element is in a disabled state.

[0046] Failure 5 relates to a scenario in which a control signal comprising an instruction that an element be disabled is stuck at logical high. In this case, the host controller 140 will not receive a status signal indicating that the remote device 1 10 satisfies an operability condition. Consequently, the host controller 140 detects a fault, and may cause remedial action to disable the element, e.g. by interrupting the power supply to the remote device 1 10. Failure 6 relates to a scenario in which a control signal comprising an instruction that an element be enabled is stuck at logical high. In this case, the remote controller 130 cannot enable the element without the correct enable sequence. Therefore, the element is in a disabled state. Failure 7 relates to a scenario in which a control signal comprising an instruction that an element be disabled is stuck at power supply level. In this case, MOSFET 330 prevents the high voltage short circuit from damaging the circuitry of the host device 210. The subsequent behavior corresponds to that of Failure 5, to disable the element. Failure 8 relates to a scenario in which a control signal comprising an instruction that an element be enabled is stuck at power supply level. In this case, MOSFET 330 prevents the high voltage short circuit from damaging the circuitry of the host device 210. The subsequent behavior corresponds to that of Failure 6. Therefore, the element is in a disabled state.

[0047] In Figure 5, failures 9 to 16 relate to faults in status signals as received via the first communication channel 150 by a host controller, such as host controller 140 shown in Figure 1 . In other words, failures 9 to 1 6 relate to faults associated with the first communication channel 150. The status signals may be transmitted by a remote controller, such as remote controller 130 shown in Figure 1 . The host controller 140 may also transmit control signals via the second communication channel 160 to the remote controller 130. Failure 9 relates to a scenario in which a control signal requesting that the element be disabled is transmitted and a subsequent status signal is left floating. In this case, pull-down in the host device 210, for example due to at least one pull-down resistor 350, pulls the status signal down to logical low. Consequently, no pulses are received to indicate that the remote device 1 10 satisfies the operability condition. Therefore, a fault is detected, and remedial action may be taken, for example by interrupting a power supply to the remote device 1 10. Failure 10 relates to a scenario in which a control signal requesting that the element be enabled is transmitted and a subsequent status signal is left floating. In this case, a fault is detected once a control signal is transmitted to request that the element be disabled. Failure 1 1 relates to a scenario in which a control signal requesting that the element be disabled is transmitted and a subsequent status signal is stuck at ground. In this case, no pulses are received to indicate that the remote device 1 10 satisfies the operability condition. Therefore, a fault is detected, and remedial action may be taken. Failure 12 relates to a scenario in which a control signal requesting that the element be enabled is transmitted and a subsequent status signal is stuck at ground. In this case, a fault is detected once a control signal is transmitted to request that the element be disabled. [0048] Failure 13 relates to a scenario in which a control signal requesting that the element be disabled is transmitted and a subsequent status signal is stuck at logical high. In this case, no pulses are received to indicate that the remote device 1 10 satisfies the operability condition. Therefore, a fault is detected, and remedial action may be taken. Failure 14 relates to a scenario in which a control signal requesting that the element be enabled is transmitted and a subsequent status signal is stuck at logical high. In this case, a fault is detected once a control signal is transmitted to request that the element be disabled. Failure 15 relates to a scenario in which a control signal requesting that the element be disabled is transmitted and a subsequent status signal is stuck at power level. In this case, MOSFET 320 prevents the high voltage short circuit from damaging the circuitry of the host device 210. No pulses are received to indicate that the remote device 1 10 satisfies the operability condition. Therefore, a fault is detected, and remedial action may be taken. Failure 1 6 relates to a scenario in which a control signal requesting that the element be enabled is transmitted and a subsequent status signal is stuck at power level. In this case, MOSFET 320 prevents the high voltage short circuit from damaging the circuitry of the host device 210. A fault is detected once a control signal is transmitted to request that the element be disabled.

[0049] The examples of Figures 1 , 2 and 3 show components of a fault detection system that facilitates the detection of faults in systems which include at least one element. A number of example methods are described below that may make use of the components of one or more of these examples.

[0050] Figure 6 shows a method 600 of facilitating fault detection in a system comprising at least one hazardous element, according to an example. The system may comprise one of the fault detection systems 100, 200 and 300 as previously described. The method 600 may be performed by the host controller 140, as previously described.

[0051] At block 610, a first communication channel is monitored for at least one status signal comprising an indication of an operability condition of a device comprising the at least one element.

[0052] At block 620, it is determined whether at least one status signal indicating that the device satisfies the operability condition is received. [0053] In response to receipt of the at least one status signal indicating that the device satisfies the operability condition, a first control signal is outputted at block 630 for transmission via a second communication channel to the device. The second communication channel is separate from the first communication channel. The first control signal comprises an instruction that the at least one element be in an activated state.

[0054] In the absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, a second control signal is outputted at block 640 for transmission via the second communication channel to the device. The second control signal comprises an instruction that the at least one element be in a deactivated state.

[0055] At block 650, it is again determined whether a status signal indicating that the device satisfies the operability condition is received.

[0056] In response to the outputting of the second control signal at block 640 and a subsequent absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, an occurrence of a fault is detected at block 660.

[0057] If, at block 650, it is determined that a status signal indicating that the device satisfies the operability condition is received, the method 600 returns to monitoring the first communication channel at block 610, according to some examples.

[0058] Figure 7 shows a method 700 of facilitating fault detection in a system comprising at least one element, according to an example. The method 700 may be performed by the host controller 140, as previously described.

[0059] At block 710, a first communication channel is monitored for at least one status signal comprising an indication of an operability condition of a device comprising the at least one element.

[0060] At block 720, it is determined whether at least one status signal indicating that the device satisfies the operability condition is received.

[0061] In response to receipt of the at least one status signal indicating that the device satisfies the operability condition, it is determined at block 730 whether to output a first control signal or a second control signal for transmission via a second communication channel to the device. The second communication channel is separate from the first communication channel. The first control signal comprises an instruction that the at least one element be in an activated state. The second control signal comprises an instruction that the at least one element be in a deactivated state. The chosen control signal is then outputted for transmission.

[0062] In the absence of receipt of the at least one status signal indicating that the device satisfies the operability condition, a second control signal is outputted at block 740 for transmission via the second communication to the device. The second control signal comprises an instruction that the at least one element be in a deactivated state.

[0063] If, at block 730 or at block 740, the second control signal is outputted, it is again determined at block 750 whether a status signal indicating that the device satisfies the operability condition is received.

[0064] In response to the outputting of the second control signal at block 730 or at block 740 and a subsequent absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, an occurrence of a fault is detected at block 760.

[0065] If, at block 730, the first control signal is outputted, or if at block 750, it is determined that a status signal indicating that the device satisfies the operability condition is received, the method 700 returns to monitoring the first communication channel at block 710.

[0066] Figure 8 shows a signaling diagram depicting a method 800 of facilitating fault detection in a system comprising at least one element, according to an example. The method 800 may be employed by a fault detection system 100 such as that depicted in Figure 1 and described above, which comprises a remote device 1 10 and a host controller 140. The remote device 1 10 comprises an element and a remote controller.

[0067] At action S8a, the host controller 140 receives from the remote device, via a first communication channel, a status signal. The status signal comprises an indication of an operability condition of the remote device 1 10.

[0068] At action S8b, the host controller 140 determines that the received status signal does not indicate that the remote device 1 10 satisfies the operability condition. [0069] At action S8c, the host controller 140 transmits a control signal via a second communication channel to the remote device 1 10. The control signal comprises a request that the element be in a deactivated state.

[0070] At action S8d, the host controller 140 receives from the remote device, via a first communication channel, a further status signal.

[0071] At action S8e, the host controller 140 determines that the received further status signal does not indicate that the remote device 1 10 satisfies the operability condition.

[0072] At action S8f, the host controller 140 detects the occurrence of a fault, based on the transmitted control signal and the subsequent absence of receipt of a status signal indicating that the remote device 1 10 satisfies the operability condition.

[0073] Figure 9 shows a signaling diagram depicting a method 900 of facilitating fault detection in a system comprising at least one element, according to an example. The method 900 may be employed by a fault detection system 100 such as that depicted in Figure 1 and described above, which comprises a remote device 1 10 and a host controller 140. The remote device 1 10 comprises an element 120 and a remote controller 130.

[0074] At action S9a, the remote controller 130 performs an operability test on the remote device 1 10. The operability test may, for example, relate to the functionality of the element 120 and/or to the functionality of any other component of the remote device 1 10.

[0075] At action S9b, the remote controller 130 transmits a status signal via a first communication channel to the host controller 140. The status signal comprises an indication of whether the remote device 1 10 conforms to an operability criterion.

[0076] At action S9c, the host controller 140 determines that a status signal indicating that the device conforms to the operability criterion has not been received.

[0077] At action S9d, the host controller 140 transmits a control signal via a second communication channel to the remote controller 130. The control signal comprises an instruction that the element 120 be in a disabled state.

[0078] At action S9e, the remote controller 130 performs a further operability test on the remote device 1 10. [0079] At action S9f, the remote controller 130 transmits a further status signal via the first communication channel to the host controller 140, the further status signal comprising an indication of whether the remote device 1 10 conforms to an operability criterion.

[0080] At action S9g, the host controller 140 determines that a status signal indicating that the device conforms to the operability criterion has not been received.

[0081] At action S9h, the host controller 140 detects the occurrence of a fault.

[0082] Figure 10 shows a signaling diagram depicting a method 1000 of facilitating fault detection in a system comprising at least one element, according to an example. The method 1000 may be employed by a remote controller 130 such as that depicted in Figure 1 and described above. The remote controller 130 may be associated with an element 120 in a remote device 1 10. The remote controller 130 may be communicatively coupled to a host controller 140 via a first communication channel 150 and via a second communication channel 1 60.

[0083] At action S10a, the remote controller 130 performs an operability test on the remote device 1 10. The operability test may involve temporarily activating and deactivating the element 120. As a result of the operability test, the remote controller 130 can determine whether or not the remote device 1 10 conforms to an operability standard.

[0084] At action S10b, the remote controller 130 outputs a status signal on the first communication channel 150 for transmission towards the host controller 140. The status signal comprises an indication of whether the remote device 1 10 conforms to the operability standard.

[0085] At action S10c, the remote controller 130 receives a control signal on the second communication channel 1 60 from the host controller 140. The control signal comprises an instruction that the element 120 be in a disabled state.

[0086] At action S1 Od, the remote controller 130 ensures that the element 120 is in a disabled state. This may involve the remote controller 130 transmitting a control signal to the element 120. In some examples, the remote controller 130 switches the element 120 from being in an enabled state to being in a disabled state. In other examples, the remote controller 130 maintains the element 120 in a disabled stable. [0087] At action S10e, the remote controller 130 performs a further operability test on the remote device 1 10. As a result of the operability test, the remote controller 130 can determine whether or not the remote device 1 10 conforms to the operability standard.

[0088] At action S1 Of, the remote controller 130 outputs a further status signal on the first communication channel 150 for transmission towards the host controller 140. The further status signal comprises an indication of whether the remote device 1 10 conforms to the operability standard. A fault may subsequently be detected by the host controller 140 in response to an absence of receipt of a status signal indicating that the remote device 130 conforms to the operability standard.

[0089] As depicted in Figure 10, the remote device 1 10, remote controller 130 and element 120 may all be functioning properly. However, faults may still occur in at least one of the communication channels between the remote device 1 10 and the host controller 140. For example, short circuits can occur along the path between the two end-points. In such cases, the host controller 140 is still able to detect the occurrence of a fault, even if the remote device 1 10 itself is functioning properly, due to the absence of receipt of an acceptable status signal.

[0090] Figure 1 1 shows example components of a host device 1 100, which may be arranged to implement certain examples described herein. In some examples, the host device 1 100 may correspond to the host device 210 as depicted in Figure 2 and described above. A processor 1 1 10 of the host device 1 100 is connectably coupled to a computer-readable storage medium 1 120 comprising a set of computer-readable instructions 1 130 stored thereon, which may be executed by the processor 1 1 10.

[0091] Instruction 1 140 instructs the processor to, responsive to receipt of at least one status signal on a first communication channel indicating that a device comprising at least one element satisfies an operability condition, output a first control signal for transmission via a second communication channel to the device, the second communication channel being separate from the first communication channel, the first control signal comprising an instruction that the at least one element be enabled. [0092] Instruction 1 150 instructs the processor to, in the absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, output a second control signal for transmission via the second communication to the device, the second control signal comprising an instruction that the at least one element be disabled.

[0093] Instruction 1 160 instructs the processor to, in response to outputting the second control signal and a subsequent absence of receipt of the at least one status signal indicating that the device satisfies the operability condition, detect an occurrence of a fault.

[0094] Processor 1 1 10 can include a microprocessor, microcontroller, processor module or subsystem, programmable integrated circuit, programmable gate array, or another control or computing device. The computer-readable storage medium 1 120 can be implemented as one or multiple computer-readable storage media. The computer-readable storage medium 1 120 may include different forms of memory including semiconductor memory devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable and programmable read-only memories (EPROMs), electrically erasable and programmable read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy and removable disks; other magnetic media including tape; optical media such as compact disks (CDs) or digital video disks (DVDs); or other types of storage devices. The computer-readable instructions 1 130 can be stored on one computer-readable storage medium, or alternatively, can be stored on multiple computer-readable storage media. The computer-readable storage medium 1 120 or media can be located either in the printing system 1 100 or located at a remote site from which computer-readable instructions can be downloaded over a network for execution by the processor 1 1 10.

[0095] The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.

Claims

CLAIMS What is claimed is:

1 . A method of facilitating fault detection in a system comprising at least one element, the method comprising:

monitoring a first communication channel for at least one status signal comprising an indication of an operability condition of a device comprising the at least one element;

in response to receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, outputting a first control signal for transmission via a second communication channel to the device, the second communication channel being separate from the first communication channel, the first control signal comprising an instruction that the at least one element be in an activated state;

in the absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, outputting a second control signal for transmission via the second communication channel to the device, the second control signal comprising an instruction that the at least one element be in a deactivated state; and

in response to outputting of the second control signal and a subsequent absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, detecting an occurrence of a fault.

2. The method of claim 1 , the method comprising:

in response to receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, further outputting a second control signal for transmission via the second communication channel to the device, the second control signal comprising an instruction that the at least one element be in a deactivated state; and

in response to the further outputting of the second control signal and a subsequent absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, detecting an occurrence of a fault.

3. The method of claim 2, the method comprising:

in response to the further outputting of the second control signal and a subsequent receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, further outputting a first control signal for transmission via the second communication, the first control signal comprising an instruction that the at least one element be in an activated state.

4. The method of claim 1 , comprising, in response to the detecting the occurrence of the fault, causing a power supply associated with the device to be interrupted.

5. The method of claim 1 , wherein power is supplied to the device via a third communication channel separate from the first communication channel and the second communication channel, the method comprising,

in response to the detecting the occurrence of the fault, causing a discontinuation of the power supplied to the device via the third communication channel.

6. The method of claim 1 , the method being performed by a host controller, wherein the device is located remotely relative to the host controller and wherein the first communication channel and/or the second communication channel comprise at least one wire.

7. A fault detection system comprising:

a remote device, comprising:

an element; and

a remote controller to: determine whether the remote device conforms to an operability criterion; and

transmit at least one status signal via a first communication channel, the status signal comprising an indication of whether the remote device conforms to the operability criterion; and

a host controller to:

monitor the first communication channel for a status signal from the remote device;

in response to receipt of a status signal on the first communication channel indicating that the remote device conforms to the operability criterion, transmit a first control signal via a second communication channel to the remote device, the second communication channel being separate from the first communication channel, the first control signal indicating a request that the element be in an activated state;

in the absence of receipt of a status signal on the first communication channel indicating that the remote device conforms to the operability criterion, transmit a second control signal via the second communication channel to the remote device, the second control signal indicating a request that the element be in a deactivated state; and

in response to transmitting the second control signal and a subsequent absence of receipt of a status signal indicating that the remote device conforms to the operability criterion, detect an incidence of a fault.

8. The system of claim 7, wherein the host controller, in response to receipt of a status signal indicating that the remote device conforms to the operability criterion, further transmits a second control signal via the second communication channel to the remote device, the second control signal indicating a request that the element be in a deactivated state; and

in response to the further transmitting of the second control signal and a subsequent absence of receipt of a status signal indicating that the remote device conforms to the operability criterion, detects an incidence of a fault.

9. The system of claim 7,

wherein power is supplied to the remote device via a third communication channel separate from the first communication channel and the second communication channel, and

wherein the host controller, in response to the detecting the incidence of the fault, causes a cessation of the power supplied to the remote device via the third communication channel.

10. The system of claim 9, further comprising a power supplier to supply power to the remote device via the third communication channel,

wherein the host controller, in response to the detecting the incidence of the fault, transmits a power control signal to the power supplier, and

wherein the power supplier, in response to receiving the power control signal from the host controller, terminates the power supplied to the remote device via the third communication channel.

1 1 . The system of claim 10,

wherein the host controller and the power supplier are arranged within a host device, and

wherein the remote device is arranged remotely to the host device.

12. The system of claim 7, wherein the system comprises a printing system, the element comprises at least one heating element, and wherein the first communication channel and/or the second communication channel comprise at least one wire.

13. The system of claim 7,

wherein the remote controller transmits at least one status signal via the first communication channel, the at least one status signal comprising an indication that the remote device conforms to the operability criterion, and wherein the absence of receipt of a status signal on the first communication channel indicating that the remote device conforms to the operability criterion is due to a failure in the first communication channel.

14. The system of claim 7, wherein the absence of receipt of a status signal on the first communication channel indicating that the remote device conforms to the operability criterion is due to a failure in the remote device.

15. A non-transitory computer-readable storage medium comprising a set of computer-readable instructions stored thereon, which, when executed by a processor, cause the processor to:

responsive to receipt of at least one status signal on a first communication channel indicating that a device comprising at least one element satisfies an operability condition, output a first control signal for transmission via a second communication channel to the device, the second communication channel being separate from the first communication channel, the first control signal comprising an instruction that the at least one element be enabled;

in the absence of receipt of the at least one status signal on the first communication channel indicating that the device satisfies the operability condition, output a second control signal for transmission via the second communication channel to the device, the second control signal comprising an instruction that the at least one element be disabled; and

in response to outputting the second control signal and a subsequent absence of receipt of the at least one status signal indicating that the device satisfies the operability condition, detect an occurrence of a fault.