Abstract:
A reagent injector control system includes a pulse width modulation (PWM) control module and an injector driver module. The PWM control module monitors current through a reagent injector during an injection control cycle, generates a PWM signal based on an amount of reagent to be injected during the injection control cycle, and at least one of selectively increases and selectively decreases a duty cycle of a PWM signal during the injection control cycle based on the current. The injector driver module selectively enables and disables the current based on the PWM signal. The reagent injector opens and injects a reagent into an exhaust system based on the current. The exhaust system receives exhaust output from an engine. The reagent reacts with nitrogen oxides (NOx).

Description:
FIELD 
     The present application relates to exhaust treatment systems and more particularly to reagent injector control systems and methods. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     To reduce the quantity of undesirable particulate matter and NOx emitted to the atmosphere during internal combustion engine operation, a number of exhaust aftertreatment systems have been developed. The need for exhaust aftertreatment systems particularly arises when diesel combustion processes are implemented. 
     One method used to reduce NOx emissions from internal combustion engines is known as selective catalytic reduction (SCR). SCR may include injecting a reagent into the exhaust stream of the engine to form a reagent and exhaust gas mixture that is subsequently passed through a reactor containing a catalyst capable of reducing the nitrogen oxides (NOx) concentration in the presence of the reagent. For example only, the catalyst may include activated carbon or metals, such as platinum, vanadium, or tungsten. 
     An aqueous urea solution is known to be an effective reagent in SCR systems for diesel engines. However, use of an aqueous solution and other reagents may have disadvantages. Urea is highly corrosive and may attack mechanical components of the SCR system. Urea also tends to solidify upon prolonged exposure to high temperatures, such as encountered in diesel exhaust systems. A concern exists because the reagent creates a deposit that is not used to reduce the NOx. 
     Urea injection systems for the treatment of diesel engine exhaust vary substantially in that different original equipment manufacturers (OEMs) specify reagent injectors having different ranges of injection flow rates. When reviewing several different OEM specifications together, the entire range of reagent injection flow rates to be provided may be expansive. As such, manufacturers of reagent injectors presently provide several different injectors each having a similar total flow rate range but sized such that the maximum and minimum values are spaced apart from one another. 
     A reagent injector includes a pintle that actuates axially within the reagent injector to open and close the reagent injector. A solenoid coil of the reagent injector produces a magnetic field based on current flow through the solenoid coil. The pintle compresses a return spring based on the magnetic field to open the reagent injector. When the magnetic field collapses, the return spring biases the pintle to close the reagent injector. 
     The pintle, however, may become magnetized over time. If the pintle becomes magnetized, the reagent injector may close at a slower rate. Additionally, current flowing through the solenoid coil generates heat. As described above, the reagent may react negatively to heat. As such, a need exists to minimize heat generated for opening a reagent injector. A need also exists to minimize a probability of the pintle becoming permanently magnetized. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     A reagent injector control system includes a pulse width modulation (PWM) control module and an injector driver module. The PWM control module monitors current through a reagent injector during an injection control cycle, generates a PWM signal based on an amount of reagent to be injected during the injection control cycle, and at least one of selectively increases and selectively decreases a duty cycle of a PWM signal during the injection control cycle based on the current. The injector driver module selectively enables and disables the current based on the PWM signal. The reagent injector opens and injects a reagent into an exhaust system based on the current. The exhaust system receives exhaust output from an engine. The reagent reacts with nitrogen oxides (NOx). 
     In other features, a reagent injector control system includes a pulse width modulation (PWM) control module and an injector driver module. The PWM control module sets a duty cycle of a PWM signal to 100 percent to open a reagent injector during an injection control cycle and selectively sets the duty cycle of the PWM signal to less than 100 percent to hold the reagent injector open during the injection control cycle. The injector driver module outputs current to the reagent injector based on the duty cycle of the PWM signal. The reagent injector opens and injects a reagent into an exhaust system based on the current. The exhaust system receives exhaust output from an engine. The reagent reacts with nitrogen oxides (NOx). 
     In still other features, a reagent injector includes a reagent inlet, a coil and a pintle. The reagent inlet is for receiving a reagent for injection into an exhaust system. The exhaust system receives exhaust output from an engine. The reagent reacts with nitrogen oxides (NOx). The coil generates a magnetic field based on current flow through the coil. The pintle moves axially based on the magnetic field. The pintle includes a pintle head and a pintle shaft. The pintle head includes a solenoid grade material having at least 1 percent silicon per unit weight. The pintle shaft is coupled to the pintle head. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram of an example internal combustion engine with an emissions control system equipped with a reagent dosing system; 
         FIG. 2  is a cross-sectional diagram of an example reagent injector; 
         FIG. 3  is a functional block diagram of an example injector control system according to the present disclosure; 
         FIG. 4  includes example graphs of a state of a reagent injector and a pulse width modulation (PWM) signal according to the present disclosure; and 
         FIGS. 5 and 6  are schematics of example injector control systems according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood that although the present teachings may be described in connection with diesel engines and the reduction of NOx emissions, the present teachings can be used in connection with any one of a number of exhaust streams, such as, by way of non-limiting example, those from diesel, gasoline, turbine, fuel cell, jet or any other power source outputting a discharge stream. Moreover, the present teachings may be used in connection with the reduction of any one of a number of undesired emissions. For example, injection of hydrocarbons for the regeneration of diesel particulate filters is also within the scope of the present disclosure. For additional description, attention should be directed to commonly-assigned U.S. Patent Application Publication No. 2009/0179087A1, filed Nov. 21, 2008, entitled “Method And Apparatus For Injecting Atomized Fluids”, which is incorporated herein by reference. 
     With reference to  FIG. 1 , an exhaust control system  8  for reducing NOx in exhaust output by a diesel engine  21  is presented. In  FIG. 1 , solid lines between elements of the system  8  denote fluid lines for reagent, and dashed lines between elements denote electrical connections. 
     The system  8  may include a reagent tank  10  for holding the reagent and a delivery module  12  for delivering the reagent from the tank  10 . The reagent may be a urea solution, a hydrocarbon, an alkyl ester, alcohol, an organic compound, water, or the like and can be a blend or combination thereof. It should also be appreciated that one or more reagents can be available in the system  8  and can be used singly or in combination. 
     The tank  10  and the delivery module  12  may form an integrated reagent tank/delivery module. The system  8  also includes an electronic injection controller  14 , a reagent injector  16 , and an exhaust system  19 . The exhaust system  19  includes an exhaust conduit  18  providing exhaust output by the diesel engine  21  to a catalyst  17 . The catalyst  17  may include a selective catalytic reduction (SCR) catalyst. The exhaust system  19  may include one or more other catalysts, such as an oxidation catalyst. 
     The delivery module  12  may comprise a pump that supplies reagent from the tank  10  via a supply line  9 . The tank  10  may be polypropylene, epoxy coated carbon steel, PVC, or stainless steel and sized according to the application (e.g., vehicle size, intended use of the vehicle, and the like). A pressure regulator (not shown) may be provided to maintain the pressure of the reagent supplied to the reagent injector  16  at predetermined pressure setpoint (e.g., relatively low pressures of approximately 60-80 psi, or in some embodiments a pressure of approximately 60-150 psi). The pressure regulator may be located in a return line  35  from the reagent injector  16  to the tank  10 . A pressure sensor may be provided in the supply line  9  leading to the reagent injector  16 . The system may also incorporate various freeze protection strategies to thaw frozen reagent or to prevent the reagent from freezing. 
     During system operation, regardless of whether or not the reagent injector  16  is injecting reagent into the exhaust stream, reagent may be circulated continuously between the tank  10  and the reagent injector  16  to cool the reagent injector  16  and minimize the dwell time of the reagent in the reagent injector  16  so that the reagent remains cool. Continuous reagent circulation may be necessary for temperature-sensitive reagents, such as aqueous urea, which may solidify upon exposure to temperatures of 300° C. to 650° C. as may be experienced in an engine exhaust system. 
     Furthermore, it may be desirable to keep the reagent mixture below 140° C. and preferably in a lower operating range between 5° C. and 95° C. to ensure that solidification of the reagent is prevented. Solidified reagent, if allowed to form, may foul the moving parts and openings of the reagent injector  16 . 
     The amount of reagent to be injected may be varied based on engine load, engine speed, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NOx reduction, barometric pressure, relative humidity, EGR (exhaust gas recirculation) flow rate, and/or engine coolant temperature. A NOx sensor or meter  25  is positioned downstream from the catalyst  17 . The NOx sensor  25  is operable to output a signal indicative of the amount of NOx in the exhaust to an engine control unit  27 . 
     Exhaust gas temperature, exhaust gas flow and exhaust back pressure and other operating parameters may be measured by various sensors. All or some of the operating parameters may be supplied from the engine control unit  27  to the electronic injection controller  14  via an engine/vehicle databus. The electronic injection controller  14  could also be included as part of the engine control unit  27 . 
     Referring now to  FIG. 2 , a cross-sectional diagram of an example of the reagent injector  16  is presented. The reagent injector  16  is coupled to the exhaust conduit  18  by a retainer, such as a retainer nut  100 . The reagent injector  16  is coupled to the exhaust conduit  18  upstream of the catalyst  17 . The reagent injector  16  includes an inlet conduit  104  where the reagent injector  16  receives reagent for injection. A reagent path  108  is formed in a lower body  112  of the reagent injector  16 . 
     Reagent flows through the reagent path  108  and is injected into the exhaust conduit  18  via an orifice  116  in an orifice plate  118 . The reagent is injected when a pintle shaft  120  of the reagent injector  16  is in an open position. When the pintle shaft  120  is in a closed position, the orifice  116  is blocked such that the reagent is not injected. The pintle shaft  120  may be made of, for example, CPM S90V type stainless steel. 
     The pintle shaft  120  is mechanically coupled with a pintle head  124 . A magnetic field that is produced by a solenoid coil  128  as current flows through the solenoid coil  128  actuates the pintle head  124  axially within a chamber  132 . Because the pintle head  124  and the pintle shaft  120  are mechanically coupled, actuation of the pintle head  124  also causes the pintle shaft to move axially. 
     A return spring  136  applies a force to the pintle head  124  in the direction of the orifice  116 . When current is not applied to the solenoid coil  128 , the return spring  136  biases the pintle shaft  120  to the closed position to prevent reagent injection. Current flowing through the solenoid coil  128  produces a magnetic field that can overcome the force of the return spring  136  and compress the return spring  136 . The return spring  136  may be compressed until the pintle head  124  contacts a bottom face of a pole piece  140 , at which point the pintle shaft  120  is in the open position. When current through the solenoid coil  128  is removed, the return spring  136  returns the pintle shaft  120  to the closed position to close the reagent injector  16 . 
     The pintle head  124  may be made of 430F type stainless steel or 430FR type stainless steel. The pintle head  124  may be made of another suitable type of solenoid grade stainless steel or another suitable type of stainless steel having at least 1 percent silicon. The pintle head  124  being made of such a material may aid in preventing the pintle head  124  from being permanently magnetized. Permanent magnetization of the pintle head  124  may increase (slow) the period necessary for the return spring  136  to actuate the pintle shaft  120  from the open position to the closed position. As the period to actuate the pintle shaft  120  from the open position to the closed position increases, the amount of reagent injected by the reagent injector  16  during closing of the reagent injector  16  also increases. The pintle shaft  120  and the pintle head  124  will be collectively referred to as the pintle. 
     Referring now to  FIG. 3 , a functional block diagram of an example injection control system is presented. The electronic injection controller  14  may include a pulse width modulation (PWM) control module  204  and an injector driver module  208 . 
     The PWM control module  204  generates a PWM signal  216 . The PWM control module  204  may generate the PWM signal  216  for a given PWM control cycle based on a target reagent injection amount  220  determined for an injection control cycle. When the reagent is supplied to the reagent injector  16  at approximately a constant pressure, the target reagent injection amount  220  can be injected when the reagent injector  16  is open for a predetermined period during the injection control cycle. 
     The target reagent injection amount  220  is determined/updated for each injection control cycle. An injection control cycle may refer to the predetermined period between the times when two consecutive reagent injections begin. A PWM control cycle may refer to the predetermined period between two consecutive times when the PWM control module  204  generates/updates the PWM signal  216 . The PWM control cycles are less than the injection control cycles. In other words, the PWM control module  204  generates/updates the PWM signal  216  more frequently than the target reagent injection amount  220  is determined/updated. The frequency at which the target reagent injection amount  220  is determined/updated may be, for example, between 1 Hertz (Hz) and 10 Hz or another suitable frequency. A frequency of 5 Hz corresponds to 200 millisecond injection control cycles. By way of contrast, the frequency at which the PWM control module  204  generates/updates the PWM signal  216  may be, for example, 100 Hz (corresponding to PWM control cycles of 10 ms) or more. The target reagent injection amount  220  for a given injection control may be set, for example, based on one or more operating parameters, such as temperature of the catalyst  17 , engine load, an amount of NOx in the exhaust, and/or one or more other operating parameters. 
     The injector driver module  208  (e.g., see  FIGS. 5 and 6 ) includes one or more switches that switch based on the state of the PWM signal  216 . The injector driver module  208  receives power from one or more sources, such as a battery  224 . The injector driver module  208  regulates a voltage  228  that is applied to a terminal of the reagent injector  16 . Current flows through the reagent injector  16  based on the voltage  228 . The reagent injector  16  opens and closes based on the current through the reagent injector  16 . 
       FIG. 4  includes example graphs of the PWM signal  216  and state  232  of the reagent injector  16  as functions of time  236 . The example graphs of  FIG. 4  are based on an injection control frequency of 5 Hz, but the injection control frequency can be another suitable frequency. 
     One injection control cycle (200 ms) occurs between time T 1  and time T 2  in the upper graph. During the one injection control cycle, the reagent injector  16  may be open between time T 1  and time T 3  to achieve the target reagent injection amount  220  for the injection control cycle. 
     Referring now to  FIGS. 3 and 4 , the PWM control module  204  sets the PWM signal  216  to one of an active state (e.g., 5 Volts) and an inactive state (e.g., 0 Volts) at a given time. The PWM control module  204  controls the duty cycle of the PWM signal  216  to control the voltage  228  and therefore the current through the reagent injector  16 . The duty cycle of the PWM signal  216  may refer to the ratio of the period that the PWM signal  216  is in the active state during a PWM control cycle to the length (period) of the PWM control cycle. 
     Each injection control cycle includes a period during which the reagent injector  16  is open (an open period) and a period during which the reagent injector is closed (a closed period). In the upper graph of  FIG. 4 , the injection control cycle between times T 1  and T 2  includes an example open period between times T 1  and T 3  and an example closed period between times T 3  and T 2 . As the target reagent injection amount  220  for an injection control cycle increases, the open period of the injection control cycle also increases. 
     The open period of each injection control cycle includes an opening period and a holding period. The reagent injector  16  transitions from closed to open during the opening period. The reagent injector  16  is held open during the holding period. When the holding period ends, a closing period begins. The reagent injector  16  transitions from open to closed during the closing period. The closed period begins when the reagent injector  16  is closed. The reagent injector  16  remains closed until, at the earliest, a next injection control cycle begins. 
     In the lower graph of  FIG. 4 , the example open period occurs between times T 1  and T 3  as in the upper graph of  FIG. 3 . In the lower graph, an example opening period occurs between times T 1  and T 4 , and an example holding period occurs between times T 4  and T 3 . The opening period is a predetermined period. For example only, the predetermined period may be set based on characteristics of the reagent injector  16  (e.g., the return spring  136 ) and may be, for example, between 2 ms and 10 ms or another suitable period. 
     During the opening period, the PWM control module  204  sets the duty cycle of the PWM signal  216  to 100 percent. In this manner, the PWM signal  216  is maintained in the active state throughout the opening period. Maintaining the PWM signal  216  in the active state causes current through the reagent injector  16  to be greater than a predetermined holding current. In particular, the duty cycle of the PWM signal  216  controls the voltage  228 , and current flows through the reagent injector  16  based on the voltage  228 . The predetermined holding current may refer to current necessary to maintain the reagent injector  16  open when the reagent injector  16  is already open. The predetermined holding current flowing through the reagent injector  16  may impose a force on the pintle that is slightly greater than the force applied by the return spring  136  (in the opposite direction) when the reagent injector  16  is open. 
     During the holding period, the PWM control module  204  regulates the duty cycle of the PWM signal  216  to maintain the current through the reagent injector  16  at approximately the predetermined holding current. A sense resistor  240 , a current sensor, etc. may be used to measure the current through the reagent injector  16 . The PWM control module  204  may vary the duty cycle of the PWM signal  216  during the holding period based on the measured current to maintain the current at approximately the predetermined holding current. The PWM module  204  may limit the duty cycle of the PWM signal  216  to between 20 percent and 80 percent or another suitable range during the holding period. 
     The current through the reagent injector  16  during the holding period is less than the current through the reagent injector  16  during the opening period. This aids in minimizing the likelihood that the pintle head  124  will become permanently magnetized. Additionally, as the reagent injector  16  generates resistive (I 2 R) heat when current is applied, the lower current may minimize the temperature of the reagent injector  16 . 
     A flyback diode  244  is connected in parallel with the reagent injector  16 . When the PWM signal  216  is in the inactive state, the injector driver module  208  blocks current flow to the reagent injector  16  and the flyback diode  244  discharges current (and collapses the magnetic field). For example only, the flyback diode  244  may include a zener diode, a low voltage diode, or another suitable type of diode. Using a zener diode as the flyback diode  244  may collapse the magnetic field and discharge current faster than other types of diodes. 
     Referring now to  FIG. 5 , a schematic of an example injector control system  300  is presented. The injector driver module  208  may include a first switching device  304 , a second switching device  308 , a diode  312 , and a capacitor  316 . 
     A DC supply voltage  320  may be applied to a first terminal of the first switching device  304 , and a second terminal of the first switching device  304  may be connected to a node  324 . The PWM signal  216  is connected to the control terminal of the first switching device  304 . For example only, the first switching device  304  may include a PNP transistor as shown in the example of  FIG. 5  or another suitable type of switching device. The DC supply voltage  320  may be generated from power from the battery  224  (e.g., using a voltage regulator) or another suitable source. The DC supply voltage  320  may be 24 Volts DC or another suitable voltage. 
     A DC hold voltage  328  is applied to the anode of the diode  312 , and the cathode terminal of the diode  312  is connected to the node  324 . The DC hold voltage  328  is less than the DC supply voltage  320 . The DC hold voltage  328  may be generated from power from the battery  224  (e.g., using a voltage regulator) or another suitable source. For example only, the DC hold voltage may be approximately 13.5 Volts DC or another suitable voltage. A first terminal of the capacitor  316  is connected to the node  324 , and a second terminal of the capacitor  316  is connected to a ground potential  332 . 
     A first terminal of the second switching device  308  is connected to the node  324 , and a second terminal of the second switching device  308  may be connected to a second node  336 . The PWM signal  216  is also connected to the control terminal of the second switching device  308 . For example only, the second switching device  308  may include a NPN transistor as shown in the example of  FIG. 5  or another suitable type of switching device. 
     A first terminal of the sense resistor  240  may be connected to the second node  336 , and a second terminal of the sense resistor  240  may be connected to a first terminal of the reagent injector  16 . Current through the reagent injector  16  may be measured based on the voltage across the sense resistor  240  and the resistance of the sense resistor  240 . 
     The reagent injector  16  can be represented as an inductor  340  and a resistor  344  connected in series. A second terminal of the reagent injector  16  is connected to the ground potential  332 . The anode of the flyback diode  244  may be connected to the ground potential  332 , and the cathode of the flyback diode  244  may be connected to the second node  336 . 
     When the PWM signal  216  is in the inactive state, the first switching device  304  is ON, and the second switching device  308  is OFF. The capacitor  316  therefore charges toward the DC supply voltage  320  when the PWM signal  216  is in the inactive state. Thus, when the PWM signal  216  is transitioned from the inactive state to the active state, the voltage  228  will be greater than the DC hold voltage  328 . 
     When the PWM signal  216  is in the active state, the first switching device  304  is OFF, and the second switching device  308  is ON. The capacitor  316  therefore discharges, and current flows through the reagent injector  16 . As the capacitor  316  discharges, the voltage  228  ramps down toward the DC hold voltage  328 . The voltage  228  may eventually be approximately equal to the DC hold voltage  328 . 
     Referring now to  FIG. 6 , another schematic of an example injector control system  400  is presented. The injector driver module  208  may include a first switching device  404 , a second switching device  408 , a third switching device  412 , a diode  416 , and a capacitor  420 . 
     A first terminal of the second switching device  408  may be connected to a DC supply voltage  424 , and a second terminal of the second switching device  408  may be connected to a node  428 . A first terminal of the third switching device  412  may be connected to the node  428 , and a second terminal of the third switching device  412  may be connected to a ground potential  432 . The anode of the diode  416  may be connected to the DC supply voltage  424 , and the cathode of the diode  416  may be connected to a node  436 . The capacitor may be connected at one terminal to the node  436  and at another terminal to the node  428 . 
     A first terminal of the first switching device  404  may be connected to the node  436 , and a second terminal of the first switching device  404  may be connected to the second node  336 . The PWM signal  216  is connected to the control terminals of the first, second, and third switching devices  404 ,  408 , and  412 . For example only, as shown in  FIG. 6 , the first, second, and third switching devices  404 ,  408 , and  412  may be NPN, NPN, and PNP switches, respectively, or other suitable switching devices. 
     When the PWM signal  216  is in the inactive state, the first switching device  404  is OFF and blocks current flow to the reagent injector  16 . The second switching device  408  is also OFF when the PWM signal  216  is in the inactive state. The third switching device  412 , however, is ON when the PWM signal  216  is in the inactive state. The capacitor  420  therefore charges toward the DC supply voltage  424  when the PWM signal  216  is in the inactive state. 
     When the PWM signal  216  is in the active state, the first switching device  404  is ON, the second switching device  408  is ON, and the third switching device  412  is OFF. Therefore, when the PWM signal  216  is in the active state, the capacitor  420  and the DC supply voltage  424  appear to the reagent injector  16  as being in series such that the voltage  228  is approximately equal to the sum of the DC supply voltage  424  and the voltage on the capacitor  420 . The capacitor  420  discharges while the PWM signal  216  is in the active state and the voltage  228  decreases toward the DC supply voltage  424 . 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
     As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories. 
     The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage.