Method and system for controlling a power engine cooling system

Abstract

Engine coolant system (101) comprising: a coolant overflow reservoir (208) having an inner recess for holding a fluid; a vertical hollow tube (210, 310, 1304) positioned outside the reservoir (208) and containing an inner recess for holding a fluid, wherein a lowest level of the recess is positioned vertically below a lowest level of the inner recess of the reservoir (208); and a sensor (362) coupled to the lowest level of the inner recess of the tube (210, 310, 1304), the system (101) further comprising a first hose (214) fluidically coupling an upper section of the reservoir (208) to an upper section of the vertical tube (210, 310, 1304);and a second hose (216) which fluidically couples the lowest level of the container (208) to a lowest level of the vertical pipe (210, 310, 1304), so that a level of fluid in the container (208) is equalized with a level of fluid in the vertical pipe (210, 310, 1304).

Description

Field of InterestThe present application relates to methods and systems for infer a fluid level in a coolant spillover reservoir (or a degassing bottle) and adjusting engine operation based on a fluid level estimated in a vertical hollow standpipe fluidly coupled to the spillover reservoir.Background and SummaryVehicles may include cooling systems configured to reduce engine overheating by transferring heat to ambient air. Therein, the coolant circulates through the engine block to remove the heat from the engine, and then the heated coolant circulates through a radiator to release the heat. The cooling system may include various components, such as a coolant reservoir coupled to the system for degassing and storing the coolant. A pressurized container that also serves to separate the entrained air from the refrigerant is typically referred to as a degassing bottle. As the temperature of the coolant rises anywhere in the system, thermal expansion of the coolant causes the pressure in the degassing bottle to increase as the trapped air volume decreases. Depressurization can be achieved by releasing the air from the degassing bottle through a valve typically mounted in the fill cap. Then, when the temperature and pressure of the refrigerant in the degassing bottle fall below atmospheric pressure, air can be drawn back into the bottle through another valve often mounted in the filler cap.If the coolant level in the bottle is too low, the volume of air is too high to build up sufficient pressure to prevent boiling and cavitation at the water pump inlet. In addition, at low fluid levels, the degassing bottle is no longer capable of separating the air from the coolant, which air can be drawn into the cooling system, which again leads to poor cooling performance. If an overflow system is used instead of an active degassing system, a similar loss of cooling system performance may be realized when the fluid levels are low.Various approaches may be used to estimate a fluid level in a reservoir. An example approach described by Murphy in U.S. Pat. No. 8,583,387 B2 uses an ultrasonic fluid level sensor installed at the bottom of a container to estimate a fluid level of the container. However, the inventors herein have recognized that in such a cooling system, the dimensions of the coolant reservoir may vary based on the temperature of the coolant contained in the reservoir. As a result, there may be inconsistencies in the estimated coolant level. In addition, due to the location of the sensor at the bottom of the container at low coolant levels, it may be unclear whether the fluid level in the container is low or empty. Still further, it may be difficult to distinguish actual low coolant levels from a false estimate of coolant level due to sensor degradation. In another example approach described by Gordon, et al. in US 2013 / 0 103 284 A1, the sensor is coupled to a hose of the coolant reservoir. One problem with such an approach is that the sensor can only detect the presence of the coolant at that location in the circuit. Key components of the powertrain cannot receive coolant regardless of the presence of coolant in one of the hoses of the coolant reservoir, particularly if that hose is isolated from the cooling system by a valve (e.g., the engine thermostat hose). Further, while an indication of a low fluid level of the coolant is received, control of engine temperature may already be degraded due to significant purging of the coolant reservoir.Further prior art is disclosed in documents DE 10 2009 045 667 A1, JP S56-61 619 A, FR 1 250 563 A, DE 103 12 102 A1, CN 2 513 088 Y, DE 10 2013 227 196 A1 and DE 692 02 189 T2.It is an object of the present invention to provide an advantageous engine coolant system, a vehicle coolant system and a method for an engine coolant system.In one example, some of the above issues may be addressed by an engine coolant system comprising: a coolant spill reservoir having an inner recess to retain a fluid; a vertical hollow tube positioned outside the reservoir and including an inner recess to retain a fluid, a lowermost level of the recess positioned vertically below a lowermost level of the inner recess of the reservoir; and a sensor coupled to the lowermost level of the inner recess of the tube. In this way, the fluid level in the coolant reservoir may be inferred more reliably based on the fluid level in the vertical tube, thereby reducing the likelihood of engine overheating.As one example, an engine coolant system may include a degassing bottle for separating entrained air from the coolant and regulating system pressure. The degassing bottle is fluidically coupled to a vertical standpipe via an upper and a lower hose, wherein the upper hose couples to the upper part of the degassing bottle at a highest level of the standpipe and the lower hose couples to the lowest level of the degassing bottle at a lowest level of the standpipe. The bottom of the vertical tube may be positioned below the bottom of the degassing bottle such that a lower threshold level of fluid trapped in the vertical tube, measurable by a coolant level sensor, may indicate an almost empty degassing bottle. The vertical tube may comprise a material that is resistant to thermal expansion such that the dimensions of the tube do not vary with the temperature of the coolant. During vehicle movement, a fluid transfer can take place between the degassing bottle and the standpipe. An ultrasonic sensor may be coupled to the standpipe within an internal recess at the lowermost level of the standpipe. The sensor may include a processor to locally process an output generated by the sensor, the processor further communicating the output to an engine controller. The sensor may be configured to periodically transmit a series of ultrasonic pulses at a predetermined frequency and energy output at the top level of the standpipe. Moreover, the sensor may be configured to receive an echo of the transmitted pulses after the reflection of the pulses from the surface of the liquid. Based on an elapsed time period between the sending of the pulses and the detection of the pulses, the local processor may estimate a level of fluid in the standpipe. Due to the unique configuration of the standpipe fluidly coupled to the degassing bottle at both the top and bottom locations, there may be a trade-off between the fluid levels between the standpipe and the degassing bottle. Thus, in addition to estimating the stand raw fluid level using the sensor output, a refrigerant volume level in the degassing bottle may also be inferred based on the fluid level in the stand pipe. An engine controller may compare the inferred coolant volume level to one or more thresholds to estimate a state of the coolant level and adjust engine operation accordingly.In this way, an accuracy and reliability of determining a coolant level of a coolant spillover tank may be increased. By inferring the coolant level of the canister based on an estimated coolant level of a standpipe coupled to the canister, inaccuracies in the estimation of the coolant level due to distortion of an output of the sensor in the tank due to thermal fluctuations are reduced. By relying on an ultrasonic sensor and the local processor to estimate the standpipe coolant level based on an echo time, the estimation of the coolant level may be accelerated and better compensated for fluid level variations due to coolant sloshing. Overall, engine overheating may be reduced due to inaccurate estimation of coolant level.It should be understood that the summary above is provided to introduce a selection of the concepts in simplified form that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Moreover, the claimed subject matter is not limited to implementations that eliminate all of the disadvantages recited above or in any part of this disclosure.Brief Description of the FiguresFIG. 1 shows an engine system including an engine cooling system. FIG. 2 shows a block diagram of an engine cooling system. FIG. 3 shows a portion of an example cooling system including a coolant reservoir fluidly coupled to a standpipe, the standpipe secured to the vehicle frame. FIG. 4 shows an alternative view of the portion of the cooling system in FIG. 3 highlighting the features of fluidly coupling and mounting the standpipe. Figure 5 shows a second alternative view of the part of the cooling system in Figure 3. FIG. 6 shows a third alternative view of the portion of the cooling system of FIG. 3 emphasizing mounting of the standpipe to the vehicle frame. FIG. 7 shows a fourth alternative view of the portion of the cooling system in FIG. 3 highlighting an ultrasonic level sensor within the standpipe and securing the standpipe to the vehicle frame. Figure 8 shows a lid configured to fit on top of a vertical standpipe. FIG. 9 shows a high order flow chart for estimating a level of the fluid in the coolant reservoir. FIG. 10 illustrates an example method for adjusting an amount of power supplied to an ultrasonic level sensor in a vertical standpipe of a cooling system. FIG. 11 illustrates an example method for estimating a fluid level in a vertical standpipe based on the information from an ultrasonic level sensor. FIG. 12 illustrates an example method for estimating a fluid level in a vertical standpipe based on the echo times and an estimate of the fluid composition. FIGS. 13A-13C show the divergence of the fluid levels in the vertical standpipe and the coolant reservoir based on the position of the vehicle. FIG. 14 illustrates an example method for determining a slosh term and adjusting an estimate of the standpipe fluid level based on the slosh term. FIG. 15 illustrates an example method for detecting degradation of an ultrasonic level sensor based on the accumulated slosh terms. FIG. 16 illustrates an example control system for determining a slosh term and adjusting an estimate of a coolant volume level based on the slosh term. FIG. 17 shows four cases of slosh within a standpipe compared to the predicted amounts of slosh. FIG. 18 illustrates an example method for determining a coolant level based on comparing an estimate of the coolant volume level to various thresholds. FIG. 19 illustrates determining a coolant condition based on a history of coolant levels and coolant conditions.DETAILED DESCRIPTIONThe following description relates to systems and methods for controlling an engine of a vehicle, the engine having a cooling system, such as that of FIGS. 1-2. The cooling system may include a coolant spillover tank, also referred to herein as a degassing bottle, fluidly connected to a narrow vertical standpipe as discussed in FIGS. 3-8. The vertical standpipe may include a level sensor that broadcasts information to an engine controller for determining an amount of coolant within the standpipe, as elaborated at FIGS. 9-12. The controller may also estimate an amount of the coolant within the degassing bottle (also referred to herein as a volume coolant level) based on the amount of the coolant within the standpipe (also referred to herein as a local coolant level) and various motion parameters as described in FIGS. 13-17. Based on the estimation of the coolant, the controller may indicate a coolant state, and based on the coolant state, restrictions may be imposed on engine operating parameters, as discussed in FIGS. 18-19. In this manner, the refrigerant volume levels can be more accurately inferred even during slosh events. In addition, low coolant levels may be more reliably detected and engine operating parameters may be correspondingly constrained to prevent overheating of the engine.FIG. 1 shows an example embodiment of a vehicle system 100 including a vehicle cooling system 101 in a motor vehicle 102. The vehicle 102 includes drive wheels 106, a passenger compartment 104 (also referred to herein as a passenger cabin), and an under-hood compartment 103. Under-hood compartment 103 may house various under-hood components under the engine hood (not shown) of motor vehicle 102. Under-hood compartment 103 may house, for example, an internal combustion engine 10. The internal combustion engine 10 has a combustion chamber that can receive intake air via an intake passage 44 and exhaust the combustion gases via an exhaust passage 48. The engine 10 as illustrated and described herein may be included in a vehicle, such as a road motor vehicle, among other types of vehicles. While the example applications of engine 10 are described with respect to a vehicle, it should be appreciated that various types of engines and vehicle propulsion systems may be used, including passenger cars, trucks, etc.Under-hood compartment 103 may further include a cooling system 101 that circulates the coolant through engine 10 to absorb the waste heat and distributes the heated coolant to a radiator 80 and / or radiator 90 via coolant lines (or loops) 82, 84, respectively. In one example, cooling system 101 may be coupled to engine 10 and may circulate engine coolant from engine 10 via engine driven water pump 86 to radiator 80 and back to engine 10 via coolant line 82, as shown. The engine-driven water pump 86 may be coupled to the engine via a front end accessory drive (FEAD) 36 and rotated via a belt, chain, etc., in proportion to engine speed. Specifically, the engine-driven pump 86 may circulate the coolant through the passages in the engine block, head, etc. to absorb the engine heat, which is then transferred to ambient air via the radiator 80. In an example where the pump 86 is a centrifugal pump, the pressure (and resulting flow) generated by the pump may be increased as the speed of the crankshaft increases, which in the example of FIG. 1 may be directly associated with the engine speed. In some examples, the engine-driven pump 86 may operate to circulate the coolant through both coolant lines 82 and 84.The temperature of the coolant may be controlled via a thermostat 38. Thermostat 38 may include a temperature sensing element 238 located at the junction of cooling conduits 82, 85, and 84. Further, thermostat 38 may include a thermostat valve 240 located in cooling line 82. As elaborated in greater detail in FIG. 2, the thermostat valve may remain closed until the coolant reaches a threshold temperature, thereby limiting coolant flow through the radiator until the threshold temperature is reached.The coolant may flow through the coolant line 84 to the radiator 90, where the heat may be transferred to the passenger compartment 104. Then, the coolant flows back to the engine 10 through the valve 122, Specifically, the heater core 90, configured as a water-to-air heat exchanger, may exchange the heat with the circulating coolant and transfer the heat to the vehicle cabin 104 based on the operator's heating requirements. As such, the radiator may also be coupled to an HVAC (heating, ventilation, and air conditioning) system of the vehicle that includes other components, such as a heating fan and an air conditioner (not shown).Based on the cabin heating / cooling request received from the operator, the HVAC system may heat the cabin air using the heated coolant in the radiator to increase the cabin temperatures and provide the cabin heating. One or more fans and cooling fans (not shown) may be included in the cooling system 101 to provide airflow assistance and to increase cooling airflow through the components under the engine hood. For example, the cooling fan 92 coupled to the radiator 80 may be operated to provide assistance to the flow of cooling air through the radiator 80. The cooling fan 92 may draw a cooling air flow into the under-hood compartment 103 through an opening in the front portion of the vehicle 102, such as through a grille shutter system 112. Such cooling air flow may then be used through the radiator 80 and other components under the engine hood (e.g., the components of the fuel system, the batteries, etc.) to keep the engine and / or transmission cool. Further, the air flow may be used to reject the heat from an air conditioning system of the vehicle. Still further, airflow may be used to improve performance of a turbo / supercharger engine equipped with intercoolers that reduce the temperature of air entering the intake manifold / engine. In one example, the grille shutter system 112 may be configured with multiple louvers (or fins, blades, or shutters), wherein a controller may adjust a position of the louvers to control airflow through the grille shutter system.The cooling fan 92 may be coupled to the engine 10 and driven by the engine 10 via an alternator 72 and a system battery 74. The cooling fan 92 may also be mechanically coupled to the engine 10 via an optional clutch (not shown). During engine operation, the torque generated by the engine may be transmitted to alternator 72 along a driveshaft (not shown). The generated torque may be used by alternator 72 to generate electrical power that may be stored in an electrical energy storage device, such as system battery 74. The battery 74 may then be used to power an electric motor 94 of the cooling fan.The vehicle system 100 may further include a transmission 40 for transmitting the power generated in the engine 10 to the vehicle wheels 106. The transmission 40, including various gears and clutches, may be configured to reduce the high speed of the engine to a lower speed of the wheel while increasing torque in the process. To enable temperature control of the various transmission components, the cooling system 101 may also be communicatively coupled to a transmission cooling system 45. The transmission cooling system 45 includes a transmission oil cooler 125 (or an oil-to-water transmission heat exchanger) located within the transmission 40 or integral with the transmission 40, e.g., in the area of the transmission sump, at a location below and / or offset from the rotating elements of the transmission. The transmission oil cooler (TOC) 125 may include multiple plate or fin elements for maximum heat transfer purposes. Coolant from coolant line 84 may be in communication with transmission oil cooler 125 via line 46. In comparison, coolant from coolant line 82 and radiator 80 may be in communication with transmission oil cooler 125 via line 48.FIG. 1 further shows a control system 14. the control system 14 may be communicatively coupled to various components of the engine 10 to execute the control routines and acts described herein. The control system 14 may include, for example, an electronic digital controller 12 as shown in FIG. 1. The controller 12 may be a microcomputer including a microprocessor unit, input / output ports, an electronic storage medium for executable programs and calibration values, a random access memory, a keep alive memory, and a data bus. As shown, the controller 12 may receive inputs from a plurality of sensors 16, which may include user inputs and / or sensors (such as transmission gear position, accelerator pedal input, brake input, automatic shift lever position, vehicle speed, vehicle acceleration, vehicle position, engine speed, mass airflow through the engine, ambient temperature, intake air temperature, etc.), cooling system sensors (such as coolant temperature, coolant level, coolant level sensor circuit board temperature, cylinder head temperature, blower speed, passenger compartment temperature, ambient humidity, thermostat output, etc.), and others. Further, the controller 12 may communicate with various actuators 18, which may include engine actuators (such as fuel injectors, an electronically controlled intake air throttle plate, spark plugs, etc.), cooling system actuators (such as the various valves of the cooling system), and others. In some examples, the storage medium may be programmed with computer readable data representing instructions executable by the processor for executing both the methods described below and other variants that are expected but not specifically listed.FIG. 2 shows an example embodiment 200 of the cooling system of FIG. 1 with various valves, loops, and heat exchangers.The coolant may circulate from various loops on the thermostat 38. As such, thermostat 38 is configured with a temperature sensing element 238 for estimating a temperature of coolant circulating at the thermostat, while thermostat valve 240 communicatively coupled to the temperature sensing element is configured to open only when the temperature is above a threshold. In one example, the thermostat valve 240 may be a mechanically actuated valve, such as a wax plug for actuation force / displacement, that opens when the coolant sensed at the temperature sensing element (wax) is above the threshold temperature.The coolant may circulate from the engine 10 to the thermostat 38 along a first bypass loop 220. From there, the coolant may be pumped back to the engine by pump 86. Coolant may also circulate from engine 10 to thermostat 38 along a second heater loop 222 via radiator 90 and engine oil cooler (EOC) 225. From there, the coolant may be pumped back to the engine by pump 86. Coolant may also circulate from engine 10 through radiator 80 to thermostat 38 via a third loop 224 based on the state of thermostat valve 240. Specifically, when the thermostat valve 240 is open, the coolant may circulate through the radiator 80 and then through the thermostat valve 240. The flow of coolant through the radiator may allow the heat from the circulating hot coolant to be dissipated to the ambient air through the radiator fan. After flowing through the thermostat valve, coolant may be pumped back to the engine by pump 86. The coolant may circulate along a fourth coolant loop 226 from either the radiator 80 or the water outlet 204, through the transmission oil cooler 125, and then to the engine oil cooler 225.The coolant may flow from the water outlet 204 and the radiator 80 to the degassing bottle 208, which may serve as a coolant reservoir within the cooling system 200. The degassing bottle 208 may be fluidly connected to the vertically oriented standpipe 210 via an upper level sensor hose 214 and a lower level sensor hose 216, as will be further described with respect to FIGS. 3-7. The upper level sensor hose may connect the top of the degassing bottle 208 to the top of the vertical standpipe 210 and may be configured to allow air to flow between the two. The lower level sensor tube 216 may be connected to the degassing bottle 208 via a degassing bottle outlet tube 216, and may be configured to allow the coolant to flow between the degassing bottle 208 and the vertical standpipe 210. The vertical standpipe 210 may include a piezoelectric coolant level sensor (PZT) 212 electronically connected to the controller 12.As the fluid in the cooling system heats up, it expands causing the pressure to build. For cooling systems with overflow bottles, the cooler cover can be the only place where this pressure can escape. The adjustment of the spring of the cooler cover as such determines the maximum pressure in the cooling system. For example, when the pressure reaches 15 psi, the pressure pushes a valve of the radiator cover, allowing the pressurized coolant to escape the cooling system. This coolant flows through the overflow pipe of the cooler into the overflow bottle. Thus, this arrangement keeps air out of the refrigerant system. When the cooler cools back, a vacuum is generated in the cooling system, which draws up a spring-loaded valve, the coolant being sucked from the bottom of the overflow bottle back into the cooler.While the spill systems control pressure by allowing the refrigerant to be exchanged via a valve, active degassing systems control pressure by allowing air to be exchanged via a valve. In the degassing systems, thermal expansion of the coolant causes the fluid to flow into the degassing bottle, thereby increasing the air pressure inside the degassing bottle. When the air pressure within the bottle exceeds an upper threshold pressure, e.g., 21 psi, the pressure opens a valve, allowing the air to escape. In one example, this valve may be located in the fill cap of the container (e.g., the cover 304 of the degassing bottle of FIG. 3 ). If the air has been released from the system, the pressure in the degassing bottle is below atmospheric pressure as the system cools back to ambient temperatures the next time. Under this condition, another valve located in the fill cap opens to allow ambient air to re-enter the degassing bottle. The degassing bottle has been given its name due to the fact that it separates the air entrained in the refrigerant. Some refrigerant from various locally high points in the cooling system is allowed to flow through the vent tubes back to the degassing bottle.The cooling system 200 may further include a turbocharger 206. The coolant may circulate from the water outlet 204, through the turbocharger 206, and via a turbo outlet hose 208 to the degassing bottle outlet hose 219. Turbo outlet hose 218 may be connected to degassing bottle outlet hose 219 downstream of the connection between lower level sensor hose 216 and degassing bottle outlet hose 219. In this manner, the high temperature coolant and / or vapor passing through the turbo outlet hose 218 may not affect fluid transfer between the degassing bottle 208 and the vertical standpipe 210.One or more temperature sensors may be coupled to the cooling system at the hot water outlet of the engine to estimate a coolant temperature. The coolant temperature may be estimated, for example, by an engine coolant temperature (ECT) sensor positioned to be in contact with the heated coolant. Alternatively, the coolant temperature may be estimated by a cylinder head temperature (CHT) sensor positioned on the engine block, e.g., a few millimeters aluminum, away from flowing engine coolant in the cylinder head. The coolant temperature may also be estimated within the vertical standpipe 210, where a circuit board temperature within the circuit board of the coolant level sensor 212 may be estimated, as further described with respect to FIG. 7.As worked out herein, the vertical standpipe may be fluidly coupled to the coolant spillover reservoir such that a level of coolant in the reservoir balances the level of coolant in the vertical standpipe. Thus, a controller may be configured to infer the level of the coolant in the degassing bottle based on the level of the coolant in the vertical standpipe. This allows for accurate estimation of the coolant level without incurring the problems associated with using a level sensor in the degassing bottle. Further, the coolant level in the vertical standpipe may be used to adjust engine operation to reduce engine overheating resulting from low coolant levels in the degassing bottle.FIG. 3 provides a view of positioning the vertical standpipe relative to the degassing bottle and the vehicle frame. The vertical standpipe, generally indicated at 310, is secured to the frame 302 via a plurality of components within a standpipe mounting bracket 310, as will be described in more detail with respect to FIGS. 4, 5, 6, and 7. The vertical standpipe 310 may be further secured to the frame 302 via the lower standpipe mounting brackets 321 aand 321 b. The position of the vertical standpipe 310 within the environment below the engine hood is based on several criteria including ensuring space for directing the upper level sensor tube 314 and the lower level sensor tube 316 between the vertical standpipe 310 and the degassing bottle 308 and attaching the standpipe to a solid and rigid support to avoid damaging oscillations. In addition, a distance between the standpipe and the degassing bottle is minimized to reduce the effect of vehicle acceleration and vehicle position on the difference between the standpipe fluid level and the degassing bottle fluid level. In this preferred embodiment, the standpipe is aligned with the side centerline of the degassing bottle, thereby minimizing the influence of lateral acceleration and lateral slopes on the difference in fluid levels between the standpipe and the degassing bottle. As shown in Fig. 3, the transverse direction runs in and out of the page. Additionally, the longitudinal distance (from left to right in FIG. 3 ) between the degassing bottle and the vertical standpipe may be such that the longitudinal acceleration and the hill / hill positions provide fluctuations in the fluid level of the vertical standpipe, thereby providing the ability to confirm the continuous sensor function.The vertical standpipe mounting brackets 320, 321 may be included as a part of the standpipe wall 382. Alternatively, the standpipe may be secured to the standpipe wall 382 via one or more bolts, welding, etc. The vertical standpipe 310 is mounted so that its principal axis is aligned with the gravitational force when the vehicle is at rest on a horizontal plane. The vertical standpipe 310 and the degassing bottle 308 have a fixed relative positioning. The orientation of the vertical standpipe 310 is configured such that the major axis of the vertical standpipe is parallel to the vertical axis of the degassing bottle. That is, the vertical standpipe 310 and the degassing bottle 308 may be configured to have a common horizontal plane on their tops. However, an underside of the vertical standpipe may be arranged to be positioned lower than the underside of the degassing bottle. This particular configuration can ensure that there is a minimum threshold level of refrigerant in the standpipe even when the refrigerant level in the degassing bottle is nearly empty. Such a configuration may be used because ultrasonic level sensors cannot measure below a minimum level. If the sensor is positioned so that its minimum level is below the outlet of the degassing bottle, any coolant in the degassing bottle is within the measurement range of the sensor. As such, the risk of the degassing bottle idling and causing engine overheating is reduced. In this manner, a coolant level may be defined by a common horizontal plane that intersects both the degassing bottle 308 and the vertical standpipe 310 when the vehicle is at rest on a horizontal plane (as will be further described with respect to FIG. 4 ).The vertical standpipe 310 may include a standpipe cap 312, an ultrasonic level sensor for measuring a coolant level (not shown), and a sensor housing 360. The vertical standpipe 310 is fluidly coupled to the degassing bottle 308 via the upper level sensor hose 314 and the lower level sensor hose 316. Specifically, the upper level sensor hose 314 is positioned to allow air to flow between the top of the vertical standpipe 310 and the top of the degassing bottle 308, while the lower level sensor hose 316 is positioned to allow coolant to flow between the bottom of the vertical standpipe 310 and the bottom of the degassing bottle 308. In this manner, the fluid level between the vertical standpipe 310 and the degassing bottle 308 may reach an equilibrium level when the vehicle is at rest, which facilitates comparison of a coolant level within the vertical standpipe and a coolant level in the degassing bottle.The degassing bottle 308 includes, in addition to the upper level sensor hose 314, a degassing bottle cap 304, a degassing inlet hose 306, and a degassing outlet hose 319. The degassing bottle 308 may include an upper piece 311 and a lower piece 313. In alternative embodiments, the degassing bottle 308 may comprise a single piece or more than two pieces. The degassing bottle 308 may be attached to any high and rigid structure in such a manner that the degassing bottle 308 is substantially horizontal. The upper surface may be substantially horizontal and may be substantially vertical, such as within 5 degrees of the vertical along each axis of the extent. As an example, the degassing bottle 308 may be secured to an inner bumper via a degassing bottle mounting bracket 309. In one example, the degassing bottle attachment support 309 may be included as a part of the degassing bottle bottom piece 313. In other examples, the degassing bottle attachment support 309 may be attached to the degassing bottle bottom piece 313 via an attachment mechanism. In further examples, the degassing bottle attachment support 309 may instead be attached to the degassing bottle top piece 311, or included as a portion of the degassing bottle top piece 311. When attached to the degassing bottle 308, the degassing bottle cap 304 may prevent the refrigerant in the refrigerant container from evaporating and escaping into the atmosphere. When the degassing bottle cap 304 is removed from the degassing bottle 308, an opening in the top of the degassing bottle 308 may be exposed for supplying further coolant to the system. The coolant may also be introduced from other components of the cooling system into the degassing bottle 308 via the degassing bottle inlet hose 306. The inlet hose can, for example, conduct the coolant from the cooler into the degassing bottle. In some examples, the degassing bottle cap 304 may include a valve, such as a pressure relief valve or a spring activated valve. As the fluid in the radiator warms up, such as due to extensive engine warming, the coolant expands causing the pressure in the cooling system to increase. The pressure of the cooling system may escape via the degassing bottle fill cap 304. Specifically, the maximum pressure in the degassing bottle may be determined via a spring-loaded valve in the degassing bottle filler cap 304. When the pressure reaches a threshold, such as 21 psi, the pressure pushes the valve open in the degassing bottle fill cap 304, allowing the pressurized air to escape the degassing bottle to the environment below the engine hood. As the system cools back, a vacuum is created that draws air back from the environment under the engine hood via another valve in the degassing bottle filler cap 304.FIG. 4 provides an alternative view of a portion of a cooling system, further describing the fluidic coupling of the degassing bottle 308 and the vertical standpipe 310. A sensor 340 may be attached to the bottom of the degassing bottle 308 to directly measure the fluid levels in the degassing bottle. The sensor 340 may be positioned within the sensor housing 342. The sensor 340 may be connected to the electronic control system and may be enabled to communicate with the controller 12 via the controller area network (not shown).The lower level sensor tube 316 is coupled to the degassing bottle outlet tube 319 via a T-joint 332. T-junction 332 is oriented so that the 90 degree branch is directed downward from outlet hose 319 so that any entrained bubbles in hose 319 tend to bypass hose 316. Further, if the coolant is absent from the degassing bottle 308 and the degassing bottle outlet hose 319, a volume of coolant may remain "trapped" in the lower level sensor hose 314 and the vertical standpipe 310. This trapped coolant volume may be measurable by the ultrasonic level sensor 362. Additionally, a connection may be established between a turbo outlet hose (218 of FIG. 2 ) and the degassing bottle outlet hose 319 downstream of the T-connection 332 (hidden by the vertical standpipe 310 in FIG. 4 ). This connection may be made by a second T-connection 334 oriented such that the 90 degree branch is upwardly directed from the degassing bottle outlet hose 319 and antiparallel to the branch of the T-connection 332. In this manner, the hot and / or vaporized coolant generated by the return flow from the turbo exhaust hose 218 (where the return flow changes as a function of engine speed) may not affect the difference in coolant level between the degassing bottle 308 and the vertical standpipe 310. The lower level sensor hose 316 may be further coupled to the side of the vertical standpipe 310 at a level below a blanking distance associated with the ultrasonic level sensor 362 (as will be discussed further below with respect to FIGS. 7 and 11).The vertical standpipe 310 is positioned such that the bottom of the standpipe 310 is below the bottom of the degassing bottle 308 and below the T-junction 332. As a result, if the coolant level in the degassing bottle 308 approaches or falls below the bottom of the bottle, the corresponding local coolant level in the standpipe 310 may remain at a specified level substantially above the ultrasonic level sensor (ULS) 362. The specified level may be based on the level of a horizontal plane extending from the top of the T-junction 332. In this manner, if it is estimated that the local coolant level in the standpipe is zero, degradation of the coolant system, such as a separate hose, may be indicated, while if it is estimated that the local coolant level in the standpipe is within a threshold distance of the specified level, an empty degassing bottle may be indicated.As shown in FIG. 4, the vertical standpipe 310 is secured to the frame 302 in such a manner that the top of the vertical standpipe occupies the same horizontal plane as the top of the degassing bottle 308. The vertical standpipe 310 has a greater vertical extent than the degassing bottle 308, and consequently the bottom of the vertical standpipe 310 is below the bottom of the degassing bottle 308. As such, when the degassing bottle 308 is empty, a level of coolant may remain in the vertical standpipe 310, providing a medium interface at which the ultrasonic pulses may be reflected from the ULS 362. In fluid equilibrium, the local coolant level in the vertical standpipe 310 corresponding to an empty degassing bottle may be defined by a horizontal plane extending the top of the T-junction 332, as illustrated by the coolant level line 333 in FIG. 4. In this manner, a specified level measurement in the vertical standpipe 310 may be associated with an empty refrigerant volume level in the degassing bottle 308, allowing a measurement of an empty refrigerant volume level to be distinguished from a condition, such as a separate hose, that may cause an empty local refrigerant level in the vertical standpipe 310.The vertical standpipe 310 may be equipped with a standpipe cap 312. The standpipe lid 312 may be configured to fit into the top of the vertical standpipe 310 such that the major axis of the standpipe lid 312 is parallel to the major axis of the vertical standpipe 312. The standpipe cap 312 may have a smooth surface 380 that may aid in the reflection of sound waves, such as those emitted by the ultrasonic level sensor 362. In one example, the standpipe cap 312 may be manufactured via a friction welding technique. The vertical standpipe 310 may be a cylindrical shell having a sufficiently small horizontal cross-section to serve as a waveguide for the ultrasonic sound waves. As a non-limiting example, the horizontal cross-section of the vertical standpipe 310 may be about 17.25 millimeters in diameter and slightly larger than the sensing element of the ultrasonic level sensor. The vertical standpipe wall 382 may be made of a smooth, rigid plastic, e.g., a 30% glass fill PA66 material.The ultrasonic level sensor (ULS) 362 may be a piezoelectric pickup element that can both transmit and receive ultrasonic pulse signals. The ULS 362 may be fixedly secured to the bottom of the vertical standpipe 310 within the sensor housing 360 and configured to emit acoustic pulses upward through the cavity of the pipe. The ULS 362 may be electronically connected to a ULS circuit board 364. The ULS circuit board 364 may physically extend across the extent of the ULS 362 and may be electronically connected to an engine controller (e.g., 12 of FIGS. 1-2 ). In a non-limiting example, the sensor 340 may also be an ultrasonic level sensor configured to perform direct estimates of the coolant level in the degassing bottle 308. Sensor housing 360 may be sealed to a standpipe top wall 382 with an O-ring and held with a metal spring clip 336 to allow for quick assembly of the two standpipe wall halves. The sensor housing 360 may be made of a material having a coefficient of thermal expansion that is closer to that of the ULS 362 compared to that of the upper standpipe 382, e.g., PPS GF30. The standpipe bottom cover 368 may be attached to the bottom of the sensor housing 360 and protect any sensor components from the environment. The cavity surrounding the circuit board 364 and the ULS 362 may be filled with a flexible potting compound to further improve isolation from the environment.Further, in FIG. 5, a bird's eye view illustrating the relative positioning of the degassing bottle 308, the vertical standpipe 310, and the frame 302 is provided. The degassing bottle mounting bracket, shown here as being attached to the degassing bottle bottom piece 313, may include a multi-tooth hole to allow sufficient compliance for assembly while maintaining an interference fit after assembly. The upper level sensor hose 314 is shown to extend horizontally between the degassing bottle top 314 and the top of the vertical standpipe 310.As shown, the vertical standpipe 310 may include an upper mounting bracket 320 extending horizontally across the frame 302 and one or more lower mounting brackets (not shown) extending horizontally below the frame 302, while the vertical standpipe is mounted adjacent a vertical end surface of the frame 302. A mounting member 322 for mounting the standpipe is shown extending vertically from the interior of the upper mounting bracket 320 and through the frame 302 and restricting movement of the vertical standpipe 310. The mounting member 322 for mounting the standpipe may extend through a metal load limiter 324 over the frame 302 and thereby avoid a common clamping load reduction that may occur over time due to creep in the upper mounting bracket 320.A spring retaining bracket 336 located at the upper portion of the vertical standpipe 310 may be configured to provide the robust retention and rapid assembly of the two halves of the vertical standpipe 310. The down tube bottom cover 368 is shown attached to the bottom of the vertical down tube 310, and may shield the ULS 362 and the ULS circuit board 364 from the environment. As shown herein, the lower level sensor tube 316 is coupled to the vertical standpipe 310 below the spring support bracket 336 and above the standpipe bottom cover 368.In Figure 6, the attachment of the vertical standpipe 310 to the frame 302 is shown in more detail. The frame 302 includes a plurality of cross-shaped support structures 303 between a top and a bottom of the frame. A mounting wedge 326 may be inserted within a cavity of one of the cross-shaped support structures 303 to assist in attaching the vertical standpipe 310 to the frame 302. The mounting wedge 326 may be configured to fit within an inner grid of the cross-shaped support structure. For example, if the inner grid has a substantially triangular shape, the attachment wedge may also be configured to have a matching triangular shape such that a tight fit is achieved. The top of the attachment wedge 326 may be in direct contact with the bottom of a top of the frame 302. The riser attachment fastener 322 may extend vertically from above the frame 302, through the metal load limiter 324, through the riser attachment post 320, through a cavity in the frame 302, and through a cavity in the attachment wedge 326. The mounting member 322 for mounting the standpipe may be coupled to the mounting wedge 368 via a J-clip 328. In this way, by coupling the standpipe mounting support 320 to the mounting wedge 326 housed within a cross-shaped support structure 303, the stability of the position of the vertical standpipe 310 relative to the frame 302 may be improved.As shown, the vertical standpipe 310 may extend substantially below the portion of the frame 302 to which it is attached. The sensor housing 360 may extend horizontally from the vertical standpipe 310 below the frame 302. Sensor housing 360 may include a cavity to receive lower level sensor tube 316, and may include an electrical connection to controller 12.FIG. 7 provides a cross-sectional view of the vertical standpipe 310, the configuration of the ULS 362 and sensor housing 360, and the configuration of the upper mounting structure including the mounting bracket 320 and the mounting member 322 for attachment. The vertical standpipe 310 is configured to be coupled to the upper level sensor hose 314 adjacent the standpipe cover 312 along the standpipe wall 382. The vertical standpipe 310 is further configured to be coupled to the lower level sensor hose 316 just above the ULS printed circuit board 364.The mounting bracket 320 may be included as a portion of the vertical standpipe wall 382 as shown. The attachment fastener 322 may be oriented perpendicular to the bottom of the attachment post 320 and the top of the attachment wedge 326. The attachment member 322 may be any suitable attachment mechanism such as a bolt or a screw.Transitioning to the lower portion of the vertical standpipe 310, the ULS circuit board 364 is shown electrically connected to the ULS 362, the coolant temperature sensor 367 (shown in FIG. 4 ), and the circuit board temperature sensor 369. The coolant temperature sensor 367 may be positioned over the ULS circuit board 364 while the ULS circuit board temperature sensor 369 may be positioned under the ULS circuit board 364. The temperature sensors 367 and 369 may be configured to periodically or continuously estimate the temperatures of the coolant within the vertical standpipe 310 and the ULS circuit board 364, respectively. In one example, the temperature sensor 369 of the ULS circuit board may be a surface mounted thermistor that is attached to the surface of the ULS circuit board 364.The ultrasonic level sensor 362 is configured to periodically generate sound waves for developing usable sensor data. In some embodiments, the ULS 362 may be configured to generate a set of multiple ultrasonic pulses (e.g., five pulses) spaced far enough apart that the pulses have sufficient time to traverse the length of the standpipe and return to the sensor (based on the length and speed of sound in the fluid) before another pulse is emitted (e.g., 5-8 milliseconds between the pulses), and periodically generate a set every total period of the pulses (e.g., every 100 milliseconds). The ULS 362 may continuously generate these sound signals during conditions when the ignition state is in a running mode of the engine. The ULS 362 is a transmitting / receiving device and is configured to receive sound waves. When the ULS 362 is disposed in the vertical standpipe 310 and a fluid is present in the standpipe, the pulses generated by the ULS 362 are reflected by a fluid-air interface or by a vertical standpipe lid 312, moving back toward the ULS 362. If the energy of the returning pulse is above a lower threshold energy, the returning pulse transmits a portion of its energy and may be received by the ULS 362. The term first order echo may also be used herein to refer to this returning pulse. The term echo may refer to this returning pulse herein unless otherwise specified. In some sensors, the returning pulses are reflected at the bottom of the fluid cavity, moving to the fluid-air interface and being reflected a second time. These waves then travel back to the ULS 362. This second harmonic return, also referred to herein as a second order echo, may also be detected and used for signal verification and more complex operation.The ultrasonic level sensor circuit board 364 may include a memory with instructions to adjust the power level supplied to the ULS 364 based on the energy associated with the ultrasonic pulse signals received by the ULS 362. For example, as described in more detail with respect to FIG. 10, if the energy associated with a set of ultrasonic pulse signals is greater than an upper threshold, or if the number of second order echoes associated with a set of pulses is greater than a threshold number, the ULS board 364 may be controlled (e.g., by the engine controller 12 of FIG. 1 ) to reduce the power supplied to the ULS 362 for emitting ultrasonic pulses. As another example, if the energy associated with a set of ultrasonic pulse signals is less than a lower threshold, the ULS board 364 may be controlled (e.g., by the engine controller 12 of FIG. 1 ), the power supplied to the ULS 362 for emitting ultrasonic pulses may increase. The pulse energy less than a lower threshold may include that an ultrasonic pulse is not detected when a pulse is expected to be detected. The ULS circuit board 364 is configured to measure time and may include programs in memory configured to capture the time stamps of the ultrasonic pulses received by the ULS 362. The ULS circuit board 364 is further configured to estimate the temperatures of the assembly and fluid via the temperature sensors 367 and 369, respectively (e.g., via the thermistor voltage measurements from the sensors 367 and 369). In this manner, the ULS circuit board 364 may generate improved estimates of standpipe coolant level based on the times of the ultrasonic pulses and the temperature estimates. The ULS board 364 may be configured to send the data to the controller 12 over a CAN bus, including, but not limited to, the temperature estimates from the sensors 367 and 369, the ultrasonic pulse time stamps, the ultrasonic pulse energy levels, and the sensor processed estimates of standpipe coolant level (as further described with respect to FIG. 11).The ULS 362 may be further configured to broadcast the information to an engine controller (such as controller 12 of FIG. 1 ) via a controller area network, as indicated. In one example, the ULS 362 may be a one-way or broadcast-only device in the CAN.FIG. 8 illustrates a detailed view of the standpipe cap 312. The standpipe cap 312 may be manufactured via friction welding. The standpipe cap 312 may be cylindrical and include a circumferential groove 384 configured to receive the top of the vertical standpipe wall 382 and rest on top of the vertical standpipe wall 382. The riser cap surface 380 may be within the area surrounded by the circumferential groove 384. The riser cap surface 380 may be configured to be smooth, flat, and parallel to the emission surface of the ULS 362. In this manner, the surface 380 of the standpipe cap may efficiently reflect the sound waves emitted by the ULS at the bottom of the standpipe. By improving the sound reflection efficiency, the accuracy of estimates of the fluid level in the vertical standpipe is increased when the standpipe is full of fluid. If the lid surface 380 is rough or angled with respect to the ULS 362, the reflected sound may be scattered away from the ULS 362 so that the standpipe would appear empty. As such, this improves the reliability of estimating the refrigerant level in the degassing bottle.FIG. 9 provides a high level routine 900 for determining a refrigerant volume level in a degassing bottle based on a measurement of the level sensor in a fluidly coupled vertical standpipe, such as degassing bottle 308 and vertical standpipe 310. The routine further depicts adjusting engine parameters based on the coolant volume level. Routine 900 may be continuously executed during engine operation to ensure that there is a sufficient level of coolant in the coolant system to prevent overheating of any engine components. Each iteration of routine 900 may be referred to herein as a measurement period. The routine includes estimating a coolant level in the vertical standpipe based on the data from the ultrasonic level sensor, adjusting the estimate of the coolant level in the vertical standpipe based on the sloshing parameters such as vehicle speed, vehicle position, and the previous coolant levels to determine the current coolant level in the degassing bottle, adjusting a long term coolant volume level based on the estimate of the current level in the degassing bottle, and adjusting the engine operating parameters based on the long term coolant volume level.Routine 900 begins at 902 where an ultrasonic level sensor may periodically emit a set of ultrasonic pulses upward from the bottom of the vertical standpipe. For example, as described above, a ULS may emit a set of 5 successive ultrasonic pulses at a specified energy, each pulse spaced 5-8 milliseconds apart. The energy of the emitted pulses may be determined based on several factors including feedback from the energy of the previously received pulses. Specifically, the energy of the pulses may be increased if the previous returning pulses were below a threshold amount of energy or were not detected, while it may be decreased if more than a threshold number of second and / or third order harmonic echoes were detected. The time interval between each pulse set may be determined based on the expected values of the acoustic velocity of the fluid and the total length of the standpipe to be measured such that the time period therebetween is at least longer than the first harmonic time period of the pipe / fluid. For example, the ULS may emit a set of pulses every 100 milliseconds.Once an ultrasonic pulse is emitted from the ULS, it may move up through the coolant in the standpipe until it reaches a medium interface, such as a coolant-air interface, or an air-solid interface if the standpipe does not have coolant in it. Some of the energy associated with the ultrasonic pulse may be reflected at the interface, generating an echo pulse, while the remainder of the energy associated with the ultrasonic pulse may be transmitted or refracted through the interface or dissipated in some other manner. The echo pulse may travel back to the ultrasonic level sensor and may be detected by the ultrasonic sensor at 904. This echo may be referred to as a first order echo. In some examples, an echo pulse may be at or below a lower threshold energy and as such may not be detectable by the sensor. In further examples, the echo received by the ultrasonic level sensor may be a second echo associated with an emitted pulse. Each echo that is detected may be assigned a time stamp, as will be described in more detail below.If multiple successive echoes are returned with sufficient energy, the associated time stamps for the primary, secondary and tertiary echoes may be compared compared to each other and to multiples for the primary echo. These echoes are correlated with the expected harmonic response. These time stamps are provided with sufficient time resolution for the accurate signal analysis and indicate the time period elapsed between the emission and the reception of this echo. This time stamp may also be referred to herein as an echo time. In some examples, a timestamp may be assigned only to pulses having an energy at or above a lower threshold energy. If a single ULS is configured to both transmit and receive the signals within the standpipe, the sensor may be configured to ignore the received pulses during a threshold duration after the emitted excitation has been stopped. This threshold duration may be referred to herein as a "blanking period" that is correlated with a potential reflection that may occur at the bottom of the fluid interface and may indicate a false indication of a low fluid level. The blanking period may be determined based on various factors such as the materials used of the sensor housing, the coupling materials that assist in transferring from the receiver to the housing, and other geometric features present in the standpipe. The internal computer or processor of the ULS board may also refer to the echoes as first order echoes or higher order echoes, such as second order echoes.At 906, the ULS internal computer may determine an echo time for each received pulse. Based on these echo times, the ULS computer may also determine an internal estimate for the local coolant level in the standpipe. The internal estimate of the coolant height may be based on an estimated speed of sound in the coolant including a temperature compensation factor and an echo time. A coolant level may be estimated in a measurement period for each received first order echo. An average of the coolant levels in a given measurement period may be determined to achieve a final sensor-processed local coolant level in the vertical standpipe. A comparison is made between these signals to ensure that the signal is a true detection of the fluid level. During conditions where excessive fluid flow or fluid-air motion within the pulse could be confused with less accurate readings, a more complex statistical condition than an arithmetic mean may be necessary to analyze the time stamps of the first order echoes. Thus, determining an average may comprise determining one or more of an average, a modal, a median, a weighted average, another statistical function, and a standard deviation, and then processing the coolant levels using an appropriate average or median based on the outliers of the data samples. For example, if the primary echo times within the set of pulses are all within 1 millisecond of each other, a high quality signal may be specified. However, if a primary echo time is significantly different than the other, a lower confidence level may be indicated.At 908, the amount of power supplied to the ULS for pulse emission may be adjusted based on the energies and / or the number of pulses of the first and second echo times for the current measurement period. In one example, a routine 1000 (in FIG. 10 ) may be executed to adjust the supply of power. Adjusting the power supplied to the ULS for pulse emission may include selectively increasing the power when a first threshold number of the received pulses is below a lower threshold energy and selectively decreasing the power when a second threshold number of the higher order echoes is received in the measurement period. The threshold number of the received pulses may be based on the presence of any primary echo data (e.g., the threshold number may be the size of the pulse set), while the threshold number of the higher order echoes may be based on the available second order echo times. The adjustment of the power supplied to the ULS will be further described below with reference to FIG. 10.The ULS may broadcast the information associated with the emitted and received pulses of the current measurement period to the engine controller (such as controller 12) at 910. For example, the ULS may broadcast a number of the received echoes above the lower threshold energy, a sensor-processed estimate of the local coolant level, the time stamps for the first and second order echoes of each emitted pulse in the measurement period, and the estimates of the temperatures of the sensor circuit and the standpipe coolant. The estimates of the temperature of the ULS circuit board and the temperature of the standpipe coolant may be determined via sensors 367 and 369, respectively. The engine controller may then determine a coolant level in the vertical tube based on this information. The coolant level in the vertical pipe may be referred to herein as a local coolant level or a local level. Determining a local coolant level may include applying the sensor-processed estimate of the local coolant level as the estimate of the local coolant level, or alternatively may include calculating a level based on the echo times, a blanking distance, and the physical extent of the standpipe. Determining a local coolant level is described in more detail with respect to FIG. 11.The coolant level in the standpipe may not directly correspond to the coolant level in the degassing bottle, the latter level also being referred to herein as the coolant volume level or the volume level. For example, if the vehicle is accelerating or decelerating or in a position, the local coolant level may deviate from the coolant volume level due to sloshing. To account for the deviation of the volume level from the local level due to sloshing, a compensation term may be calculated by the engine controller. This compensation term may be used to adjust the local coolant level estimate to a volume coolant level estimate at 914, e.g., via routine 1400 of FIG. 14. Applying the compensation to the local coolant level estimate to adjust for sloshing is described in more detail with respect to FIG. 14.After a set local coolant level estimate is determined for the measurement period at 914, routine 900 proceeds to 916 where the coolant volume level estimate may be set based on the set local coolant level estimate. Adjusting the coolant volume level estimate may include filtering the adjusted local coolant level estimate into the coolant volume level estimate. Adjusting the coolant volume level estimate is described in more detail below with respect to FIGS. 14 and 16. The coolant volume level estimate may not be adjusted during measurement periods where a local coolant level estimate is not determined. An estimate of the coolant volume level may correspond to one or more coolant volume conditions, the coolant volume conditions being defined by one or more level thresholds.Then, routine 900 proceeds to 918 where the vehicle coolant state may be adjusted based on the coolant volume level estimate. The vehicle may have a fixed number of possible coolant conditions, e.g., EMPTY, LOW, OK, FAILED, and UNKNOWN / DEGRADED. The coolant conditions may directly correspond to a coolant volume level or may indicate degradation of hardware components, such as an ultrasonic level sensor. In some cases, adjusting the coolant state may only occur when a coolant level indicating a new coolant state has passed for a threshold duration.Based on the coolant state, at 920, engine operating parameters may be adjusted. For example, if the coolant level is below a lower threshold for longer than a threshold duration and the vehicle's operating parameters indicate that an accurate coolant level may be detected, a low coolant state may be assumed. This may result in limiting operation in which engine loads may be constrained to be below an upper threshold to ensure that the engine components maintain designated operation. In another example, if the coolant state is LOW, the controller may display a message to the engine operator indicating a low coolant level. Adjusting the coolant state will be described in more detail with respect to FIG. 18. In some cases, at 922, a system diagnostic may be performed based on the coolant state, e.g., a sensor degradation may be determined based on the coolant state and the change in coolant state during a duration of vehicle operation. Routine 900 then ends.FIG. 10 illustrates a routine 1000 for adjusting the power supplied to the ultrasonic level sensor for pulse emission based on feedback from the energy of the received pulses. The power supplied to the ultrasonic level sensor for pulse emission may also be referred to herein as the transmission energy. Routine 1000 may be executed during each measurement period after the set of pulses is received and may increase the energy efficiency of the ultrasonic level sensor.Routine 1000 begins at 1002 where the number of first order echoes within the set of measurements is determined with an amount of energy above a lower threshold and compared to a threshold number. The lower energy threshold may be determined based on a fixed minimum value. This minimum threshold number may be determined based on providing sufficient function under most steady state operating conditions. For example, if 5 pulses were emitted during the measurement period, the threshold number may be 4 pulses of 5 having an amount of energy above the lower threshold. If the number of echoes with sufficient energy is higher than a threshold, it may be determined that the energy output of the sensor is sufficiently high. It may also be determined that further optimization of the energy output may be possible. In particular, if the energy output is sufficiently high, then the energy output of the sensor can be reduced without suffering a considerable drop in the number of echoes with sufficient energy. By reducing the energy output without affecting the echo efficiency, the advantages of power reduction can be achieved. Moreover, when operating at high pulse emission energies, unexpected additional pulses may be detected due to the improperly reflected energy leading to false data being provided to the measurement system. Consequently, it is advantageous to provide a reduced ultrasonic energy whenever the conditions allow.In one example, in response to receiving a sufficiently small number of valid first harmonic echoes (e.g., 0 or 1), the energy output level may be increased to attempt to obtain sufficient energy quickly enough to recover sufficient 1 / 2nd-order retransmissions (e.g., an increase of 10%-20%). In another example, if all of the first order harmonics are present and if more than a high number of second harmonics are validly returned (e.g., more than 4 or 5 second harmonics), the amount of pulse energy transfer is decreased by a small amount of decrement (e.g., a 1% decrease). In other examples, some conditions may indicate maintaining the current transmit energy when all transmitted pulses provide clear first and second echo times.Accordingly, if the number of echoes having an amount of energy above the lower threshold is at or above the threshold number, routine 1000 proceeds to 1004 where the energy supplied to the ULS for emitting pulses may be decreased. Otherwise, if the number of echoes having an amount of energy above the lower threshold is below the threshold number, routine 1000 proceeds to 1006 where the energy supplied to the ULS for emitting pulses may be increased. Here, based on the number of echoes with sufficient energy lower than the threshold, it may be determined that the energy output of the sensor is not high enough. It may also be determined that further optimization of the energy output is necessary. Accordingly, the energy output of the ULS is increased to improve the number of echoes that have sufficient energy.Decreasing the transmit energy at 1004 may include decreasing the transmit energy at a first rate under a first set of conditions and decreasing the transmit energy at a second rate under a second set of conditions, the second rate less fast than the first rate. For example, the first set of conditions may include receiving a threshold number of first order echoes above the lower energy threshold while also receiving a number of higher order pulses above an upper threshold number. In this example, the transmit energy may be decreased at a first slow rate, the rate being intended to ensure continuity of the signals that return and have a controlled decrease in power. An excessive reduction rate may result in dithering of the sufficient and insufficient data in alternating cycles. This dithering behavior can then be incorrectly detected as a loss of an exact signal function, which leads to superfluous conditions of the vehicle reaction. The second set of conditions may include each first order echo in the measurement period that is above the lower threshold energy and a number of higher order pulses below the upper threshold number. In this example, the transmit energy may be decreased at a second slow rate, the second rate being slower than the first. In another example, the first set of conditions may include the transmit energy being at the physically maximum level and the number of first order echoes above the lower threshold energy being above the threshold number. In comparison, the second set of conditions may include the transmit energy being at the physically maximum level and the number of first order echoes above the lower threshold energy being below the threshold number.Increasing the transmit energy at 1006 may include, under a first set of conditions, increasing the transmit energy at a first rate and under a second set of conditions, increasing the transmit energy at a second rate, the second rate being less fast than the first rate. In some examples, under a third set of conditions, the transmit energy may jump to the physically maximum level and be maintained at the physically maximum level until such conditions are no longer detected. For example, the first set of conditions may include the number of first order echoes having an amount of energy above the lower energy threshold that is below a lower threshold number but is not zero. In this example, the transmit energy may be increased at a faster rate, the rate determined based on the number of re-transmissions of valid first order pulses that is less than a threshold (e.g., the threshold may be 3 pulses). The second set of conditions may include there being a small number of retransmissions of second order harmonic pulses (e.g., less than 3), in which case the transmission energy may be increased at a lower rate, the rate being determined based on the balance between the retransmissions of valid first and second harmonic pulses. The third set of conditions may include the number of first order echoes having an amount of energy above the lower energy threshold that is zero. In this example, the transmit energy may be increased to a maximum level. In some examples, if either the first or second set of conditions is detected but the transmit energy is at an upper threshold, where the upper threshold is below the maximum level, the transmit energy may be maintained and not increased. In another example, the transmit energy may be maintained when either the first or second set of conditions is detected but the transmit energy is above the upper threshold and below the maximum level.FIG. 11 provides an example routine 1100 from beginning 1101 to end 1144 for estimating the local coolant level in the standpipe based on the information from the ultrasonic level sensor and the operating conditions of the engine and adjusting this estimate with a compensation term. During a first set of conditions, an estimate of the local coolant level may be calculated based on a sensor-processed level estimate, wherein during a second set of conditions, the controller may calculate a level estimate based on the time stamps of the first order echoes and / or the estimates of coolant and ULS circuit temperatures and / or an estimated coolant mixture and / or the measurements of vehicle acceleration and position and / or the physical parameters of the standpipe. Routine 1100 may be executed during each measurement period.At 1102, in addition to receiving the sensor-processed coolant level estimate 1108, the controller receives the raw data from the ultrasonic level sensor including, but not limited to, a number of echoes above the lower threshold energy at 1104, the echo time stamps 1106 for the first order and higher order echoes, and the coolant temperature and ULS board temperature estimates 1110. At 1112, the engine may determine whether the engine conditions are quiet, and if so, may apply the sensor-processed coolant level estimate 1108 as the unprocessed fluid level in the standpipe at 1114. Determining whether the engine conditions are quiet may include determining whether a dynamic acceleration of the vehicle, the grade / grade of the vehicle, and / or the engine speed change by more than threshold amounts. These parameters may be determined based on both the information from the vehicle's accelerometers (e.g., the roll stability or airbag module) and the engine's operating parameters from a powertrain / engine control module.If it is not determined at 1112 that the engine conditions are quiet, the controller may proceed to calculate the local coolant level based on the echo times 1106 and the temperatures 1110. At 1116, the controller checks the number of received first order echoes that are at or above a threshold amount of energy. In some cases, the threshold amount of energy may be the energy levels at which a signal may be distinguished from noise. If the number of first order echoes is at or above the threshold amount of energy above a threshold number of echoes, routine 1100 proceeds to 1124 to calculate a coolant level based on these first order echo times. The threshold number of echoes may be determined based on the data collected for a base fraction of the valid first harmonic echoes seen at the flat-bottomed steady-state idle conditions. For example, if the measurement period comprises 5 emitted pulses, the threshold may be 4.In some examples, a first order echo may have been misidentified as a higher order echo by the internal processor of the ULS board. Accordingly, at 1118, the controller may check the time stamps of the higher order echoes and determine whether one or more first order echoes have been misidentified by the sensor as higher order echoes. Determining whether a first order echo has been misidentified may be based on comparing the return time stamps of the reported first order echoes with the calculated 2ndor 3rdorganization times that might occur (calculated based on the speed of sound and 4 standpipe lengths (2ndorganization) or 6 standpipe lengths (3rdorganization)). If no first order echoes were misidentified, then the number of first order echoes is still below the threshold number. In this case, at 1128, the controller may identify an invalid measurement value for the measurement period because there are not enough data points to perform a more reliable estimate of the coolant level in the standpipe. Identifying an invalid measurement period also includes not updating the coolant volume level at 1130 based on the data from the current measurement period and using the volume level data from the latest valid measurement period at 1132.If it is determined at 1118 that one or more first order echoes have been incorrectly identified as higher order echoes, these echoes may be re-allocated as first order echoes at 1120. The controller may then again check whether the number of first order echoes is at or above the threshold amount of energy above the threshold number of echoes. If the number is still below the threshold number, routine 1100 may proceed to 1128, 1130, 1132, as described above. If the number is at or above the threshold number, routine 1100 proceeds to 1124 where an estimate of the local coolant level may be determined, e.g., via routine 1200 of FIG. 12.In FIG. 12, routine 1200 provides an example routine for calculating an estimate of the local coolant level based on the echo times and a number of temperature estimates. The calculation is based on the assumption that an ultrasonic pulse moves from the sensor to a coolant-air medium interface and back to the ultrasonic level sensor in the time period indicated by its respective time stamp. An estimate of the distance travelled by the ultrasonic pulse is calculated based on the echo time and an estimate of the speed of sound in the coolant.Routine 1200 begins at 1202 where the raw first order echo times and coolant temperatures are received by the controller. At 1204, a composition of the coolant mixture may be estimated based on comparing an estimate of the speed of sound (estimated based on an average local standpipe level on flat ground) and a currently measured speed of sound. An estimate for the speed of sound in the coolant may then be determined at 1206 based on both the estimated temperatures of the coolant and the ULS circuit and the estimated coolant mixture. For an estimated speed of sound and a time stamp, the distance travelled for each pulse may be calculated at 1208 based on the following formula: where v_sound is the estimated speed of sound, t_0 is the first order echo time, and the product of these two is multiplied by one half to account for the fact that the pulse must travel the length of the coolant level twice to return to the sensor. A distance may be estimated for each first order echo in the set that is above the lower threshold energy.Returning to FIG. 11, at 1126, the standpipe coolant level estimates of routine 1200 may be compared to the physical range of the standpipe. For example, the memory of the controller may include an upper threshold for a maximum level of coolant level based on the distance between the ULS sensor and the top of the vertical sensor, and may include a lower threshold for a minimum level of coolant based on the distance between the ULS sensor and the lower level sensor hose ( 316 in FIG. 3 ). In other examples, the lower threshold may be based on the blanking distance of the sensor. The physical range of the standpipe may then be any level between the upper physical threshold and the lower physical threshold. If the estimates of local level are not within the physical range of the standpipe, routine 1100 proceeds to 1128. In some examples, the presence within the physical range of the standpipe may include the presence within a threshold margin below the lower physical threshold or within a threshold margin above the upper physical threshold. In these examples, the threshold clearances may be determined based on the worst case expected part tolerances and further based on the upper and lower physical thresholds themselves.However, if the estimated standpipe levels are within the physical range of the standpipe, routine 1100 proceeds to 1134, where a decision is made based on whether the estimated standpipe levels are within the standpipe range or within the threshold clearances outside of the unprocessed standpipe. If the unprocessed standpipe level is outside the standpipe range and within the threshold clearances, the unprocessed standpipe level is trimmed at 1136 to be within the physical range. If the unprocessed standpipe level is within the physical range at 1134, cropping may not be necessary, and routine 1100 may proceed at 1138.At 1138, an average of the calculated and cropped level estimates may be determined. Determining an average may include one or more of checking an average, median, and standard deviation, and then processing the coolant levels using an appropriate average or median based on the outliers of the data samples. For example, if one or more of the samples are outside the physical range, determining an average may only include the points measured as originally within the range. This average may be applied as the raw local coolant level estimate or the raw standpipe coolant level estimate for the measurement period. This average may then be applied at 1140 as the raw estimate of the standpipe coolant level. At 1142, a separate routine may be executed to estimate the volume coolant level based on the raw estimate of the standpipe coolant level and other factors such as vehicle acceleration and position. For example, routine 1400 of FIG. 14 may be executed to estimate a coolant volume level. This process is described in more detail with respect to Figures 13-16.FIGS. 13A-13C provide illustrations of a coolant reservoir (degassing bottle 1302) fluidly coupled to a vertical standpipe 1304 and oriented at three different angles with respect to a horizontal plane. Degassing bottle 1302 is shown with degassing bottle cap 1328. An upper fluidic connection is established between the degassing bottle 1302 and the vertical standpipe 1304 via an upper level sensor hose 1326, and may allow air to be transferred between the top of the degassing bottle 1302 and the top of the vertical standpipe 1304. When the degassing bottle 1302 and the vertical standpipe 1304 are horizontal, the upper level sensor tube 1326 may extend horizontally between the two vessels, as illustrated in FIG. 13A. A lower fluidic connection is established between the degassing bottle 1302 and the vertical standpipe 1304 via the lower level sensor hose 1318 and may allow for a transfer of coolant 1306 between the degassing bottle 1302 and the vertical standpipe 1304. The lower level sensor hose is coupled to the degassing bottle outlet hose 1316 via a T-joint 1320 oriented such that the lower level sensor hose 1318 deviates from the outlet hose 1316 in a downward direction. The lower level sensor tube 1318 is coupled to the degassing bottle outlet 1316 below the bottom of the degassing bottle 1302 and upstream of the turbo outlet 1322. The vertical standpipe 1304 may include a ULS 1308 for estimating a local coolant level. The ULS 1308 may be connected to a controller area network (not shown).By establishing a fluidic connection between a larger vessel, such as the degassing bottle 1302, and a smaller, narrow vessel, such as the vertical standpipe 1304, transfer of fluid between the two vessels produces a greater effect on the refrigerant level of the smaller vessel than that of the larger vessel. During some conditions, the local coolant level 1314 and the volume coolant level 1312 may be the same or at least within a lower threshold of each other, e.g., as illustrated in FIG. 13A. The conditions where the local coolant level 1314 and the volume coolant level 1312 are within a lower threshold of each other may include when the vehicle is not accelerating and when the vehicle is in a horizontal position. During other conditions, fluid transfer between the degassing bottle 1302 and the vertical standpipe 1304 may cause the local coolant level 1314 to be greater than the volume coolant level 1312 by at least a threshold amount. Example conditions that may cause such fluid transfer may include when the vehicle decelerates and when the vehicle has a bow down position in the embodiment where the standpipe is located in front of the degassing bottle in the vehicle.During still other conditions, fluid transfer between the degassing bottle 1302 and the vertical standpipe 1304 may cause the local coolant level 1314 to be less than a volume coolant level 1302 by at least a threshold amount. Example conditions that may cause such fluid transfer may include when the vehicle is accelerating and when the vehicle is in a bow-up position in the embodiment where the standpipe is in front of the degassing bottle in the vehicle.To adjust an estimate of the local coolant level to an estimate of the coolant volume level, the estimates of vehicle acceleration and position may be used to estimate the direction and magnitude of the difference in coolant levels, e.g., via routine 1400 of FIG. 14. Adjusting the local coolant level to reflect the coolant volume level includes determining a compensation term as an estimate of the deviation between the local standpipe level and the coolant volume level. This compensation term may be referred to herein as a slosh or slosh term. The slosh term may have an associated sign and magnitude and may be added to the unprocessed standpipe level to form a set estimate of the standpipe level. That is, the slosh term may be subtracted from the unprocessed standpipe level or added to the unprocessed standpipe level to form the adjusted estimate of the standpipe level that estimates how the standpipe level would be if the vehicle were horizontal and the standpipe and volume levels were in balance. Therefore, the adjusted standpipe level serves as an instantaneous estimate of the refrigerant level in the degassing bottle. The coolant volume level estimate may then be updated based on the adjusted standpipe level estimate. Executing routine 1400 during a measurement period may be based on whether a valid coolant level measurement is present for the measurement period. For example, routine 1400 may be executed during measurement periods where an unprocessed standpipe coolant level has been determined, while it may not be executed during measurement periods where the coolant level measurements have been flagged as invalid, such as at 1128 in routine 1100.Routine 1400 begins at 1402, where the engine controller receives an unprocessed estimate of the local coolant level for the current measurement period. The raw estimate of the local coolant level may be determined by a separate routine, such as routine 1100 of FIG. 11. The raw level estimate is later used in routine 1400 in combination with a slosh term to determine an estimate of the refrigerant volume level. After receiving the raw coolant level estimate, routine 1400 proceeds to 1404 where the longitudinal acceleration and position estimates may be determined. The estimates of the longitudinal acceleration may be based on the data from an accelerometer or alternatively from a time derivative of the measurements of the speed sensor. The estimates of the longitudinal position may be based on the data from various sensors. Similarly, at 1406, the controller may determine the estimates for the lateral acceleration and position of the vehicle. The estimates of lateral acceleration may be based on the data from an accelerometer or alternatively may be calculated from the measurements of speed and wheel speed. The estimates of the lateral position can be based on the data from various sensors.Based on the estimates of acceleration and position in both the longitudinal and transverse directions performed at 1404 and 1406, an expected or predicted slosh term may be determined via a transfer function. In one example, the transfer function may be expressed by the following equation: where Long. Gain and Lat. Gain weighting factors for the longitudinal and transverse slosh estimates are Long. Acc.% and Lat. Acc.% are weighting factors that weight the relative contributions of acceleration and position in the slosh estimate for each direction, Long. Acc. is an estimated longitudinal acceleration, Long. Att. is an estimated longitudinal position, Lat. Acc. is an estimated lateral acceleration and Lat. Att. is an estimated lateral position. The estimates of acceleration may be in units of distance per squared unit time, while the estimates of attitude may be in units of degrees of slope or static percent of slope in that axis. The determination of the longitudinal and lateral gains may be based on a correlation with the non-acceleration flat-bottom data against the data of a tilt table or may be based on the vehicle data determined at a range of accelerations and static positions, and may be each in units of the percentage contribution of the correlation. The relative weight of the acceleration and the posture may be determined based on the same correlation data using a method of data matching (e.g., least squares estimation).After determining a predicted slosh term, the adjusted estimate of the standpipe coolant level (i.e., the raw estimate of the level plus the predicted slosh term) may be above or below the physical range of the standpipe (as described earlier with respect to FIG. 11 ). In these examples, the predicted slosh may be adjusted based on the physical area of the standpipe. In one example, if the predicted slosh and the raw estimate of standpipe level are added to be greater than the height of the standpipe, adjusting the predicted slosh based on the physical range of the standpipe may include cropping the predicted slosh such that the adjusted estimate of standpipe coolant level is at the upper physical range threshold. In another example, if the predicted slosh plus the raw standpipe level estimate are added to be less than the canister height, adjusting the predicted slosh may include clipping the slosh estimate such that the adjusted standpipe coolant level estimate is at the lower physical region threshold.In addition to an expected slosh term, an actual slosh term may be estimated at 1412. An estimate of the actual slosh may be determined based on a comparison of the raw estimate of the standpipe coolant level with an estimate of the volume level. In one example, the actual slosh may be the difference between the unprocessed standpipe coolant level in the current measurement period and the latest estimate of the volume level.Based on a comparison between an expected slosh and an actual slosh, an assumed slosh term may be determined at 1414. In one example, determining an assumed slosh in the signed direction of the expected slosh may include selecting the lower absolute value of the actual slosh and the compensated level as the assumed slosh. This example will be further explained below with reference to Fig. 16. In another example, if both the uncut expected slosh and the actual slosh are within the physical range of the standpipe and the magnitude of the expected slosh is greater than the magnitude of the actual slosh, then the expected slosh may be trimmed based on the actual slosh and then applied as the assumed slosh. This example will be further explained below with reference to Fig. 17.After determining an assumed slosh for the measurement period, the assumed slosh may be applied to the raw standpipe level estimate at 1416 to determine the adjusted standpipe coolant level estimate. The coolant volume level estimate may then be updated at 1418 based on the adjusted standpipe coolant level estimate. In one example, a filter may be used to integrate the adjusted estimate of the standpipe coolant level from the current measurement period into the estimate of the long term coolant volume level. The filtering of the adjusted estimate of the standpipe level may include filtering by a low pass filter based on a variable time constant, the time constant determined based on both the sign and magnitude of the difference between the current slosh compensated measurement and the estimate of the long term volume level and the time period between the last valid measurement and the current valid and slosh compensated measurement. In this manner, the transient changes in the coolant level can be smoothed, and a more stable estimation of the coolant volume level can be formed.Routine 1400 then proceeds to 1420 where a sensor diagnostic may be performed based on a comparison of the terms of the expected slosh and the actual slosh for the measurement. In one example, the integral of the expected slosh and the integral of the actual slosh may each be updated based on the term of the expected slosh and the actual slosh for the measurement period. These integrals may be incremented whenever an expected slosh or actual slosh is detected and may be decremented by a fixed amount in each measurement period. The sensor degradation may be made based on the ratio of the two integrals and will be further described with reference to FIG. 15.FIG. 15 provides routine 1500 for determining whether an ultrasonic level sensor in a vertical standpipe (such as ULS 362 of FIG. 3 ) is degraded. The routine is based on a comparison of the amounts of expected slosh and actual slosh accumulated over time. The accumulations of the amounts of expected sloshing and actual sloshing may be characterized by an integral of the expected sloshing and an integral of the actual sloshing. By comparing these integrals, an engine controller may determine whether more or less slosh than expected has been detected during the time period, and may indicate degradation of the sensor based on this comparison under some conditions.Routine 1500 begins at 1502 where the value of the integral of the expected slosh may be incremented if an expected slosh has been detected during the measurement period. For example, at 1408 in FIG. 14, the motion parameters may indicate an amount of expected slosh, and the integral of the expected slosh may be incremented by an amount based on the amount of expected slosh in the measurement period. Similarly, if an actual slosh has been detected during the measurement period, the value of the integral of the actual slosh may be incremented at 1504. The amount by which the integral of the actual slosh is incremented may be based on the amount of the detected actual slosh. Based on the comparison of the two integrals, it may be determined that the ultrasonic level sensor is degraded due to excessive noise if a first set of conditions is met, while it may be determined that it is degraded due to a stuck measurement if a second set of conditions is met.At 1506, both the expected slosh integral and the actual slosh integral may be decremented by a predetermined amount. In one example, each integral may be decremented by the same fixed amount in each measurement period, the fixed amount determined based on a base amount of integration per loop measured under verified horizontal conditions without acceleration where there is less than a lower threshold amount of slosh, thereby establishing a base noise level of the calculation. In another example, the integral of the actual slosh in each measurement period may be decremented by a first fixed amount, while the integral of the expected slosh in each measurement period may be decremented by a second fixed amount, the first amount determined based on a base amount of integration per loop measured under verified horizontal conditions without acceleration where there is no or limited slosh, thereby establishing a base noise level of the calculation while the second amount is a smaller fraction (e.g., 80%) of the first amount. In this manner, the decrement rate of the expected integral for expecting any amount of slosh during each measurement period is affected. In another example, each integral may be decremented by the same variable amount in each measurement period, the variable amount determined for each measurement period based on the same conditions as above to determine a basis, and further including varying the decrement rate based on an amount of expected slosh that is immediately calculated based on the weighted combination of changes in longitudinal and lateral acceleration and position. In yet another example, the integral of the expected slosh may be decremented by a first variable amount in each measurement period, while the integral of the actual slosh may be decremented by a second variable amount in each measurement period, the first and second amounts determined based on the same principles as the other combination examples above. Other decrementing possibilities may include decrementing one integral by a fixed amount while decrementing the second integral by a variable amount.After each integral is incremented based on the amounts of slosh detected during the measurement period and decremented based on one of the above example noise base compensations or similar compensation, a ratio of the integral of the actual slosh and the integral of the expected slosh may be determined at 1508. In one example, the amount of the integral of the actual slosh may be divided by the amount of the integral of the expected slosh, which number may be applied as the ratio of the two.At 1510, this ratio is compared to an upper threshold. The upper threshold ratio may be determined based on measuring the greatest ratios seen in a test that physically highlights the amount of slosh within the standpipe (e.g., positioning the vehicle on a shaker table and operating the table at different amplitudes / frequencies to find the worst case resonant with the measurement of slosh). Alternatively, the upper threshold ratio may be determined based on directly introducing an electrical noise signal into the level sensor input into the electronic control module. The ratio being greater than the upper threshold may indicate that more slosh was detected than was expected by more than a threshold amount. If the ratio is greater than the upper threshold, routine 1500 may proceed to 1512 where the controller may indicate that the ultrasonic level sensor is degraded due to noise mitigation. After indicating the degradation of the sensor due to the noise stick, routine 1500 ends.If the ratio is not greater than the upper threshold, routine 1500 proceeds to 1514, where the ratio of 1508 may be compared to a lower threshold. The lower threshold may be determined based on executing one or more drive cycles (e.g., either the FTP or the US06) that occur at near empty, full, and half full level standpipe / degassing bottle, respectively, on a flat ground prior to each test. These tests involve completely closing either the upper or lower standpipe tubing to prevent gas or fluid exchange during the drive cycle. Thus, the lower threshold may represent a base noise level. The lowest ratios seen from these tests are used to set the lower threshold level. The ratio less than a lower threshold may indicate that less slosh was detected than was expected by more than a threshold amount.If the ratio is less than the lower threshold, routine 1500 may proceed to 1516, where the controller may indicate that the ultrasonic level sensor may be blocked or that fluid transfer between the degassing bottle and the vertical standpipe may be physically prevented. The controller may distinguish between these two degradations based on waiting until both a predetermined time period and a predetermined distance have been traveled before determining whether the fault has disappeared and thus suggest that the ratio is low due to the blockage. If the ratio is not less than the lower threshold, routine 1500 proceeds to 1518 where sensor degradation is not indicated, and routine 1500 then ends.FIG. 16 provides a control scheme 1600 for determining an assumed slosh, applying the assumed slosh to the unprocessed standpipe coolant level to determine a adjusted standpipe coolant level, and updating a volume coolant level based on the adjusted standpipe coolant level. The data from motion sensors such as an accelerometer 1602, a position sensor 1604, a vehicle speed sensor 1606, and a wheel speed sensor 1608 may be used at 1610 to determine the longitudinal acceleration, the lateral acceleration, the longitudinal position, and the lateral position. In some examples, both longitudinal and lateral accelerations may be determined based on the data from a single acceleration. In other examples, the longitudinal and lateral accelerations may be determined by separate acceleration sensors.Similarly, the longitudinal and lateral positions may be determined by one or more position sensors. At 1612, the variable 1610 is used as input to a function that determines an expected slosh 1614. In one example, function 1612 may be expressed by the equation described above with respect to FIG. 14. The expected slosh 1614 may then be trimmed at 1620, and an integral 1644 of the expected slosh may also be incremented based on the expected slosh 1614. The expected slosh integral 1644 will be described in more detail below. Cropping 1620 may be based on the physical area of standpipe 1618, as described above with respect to FIG. 14, which may be stored in the memory of controller 1616 and which may be retrieved from the memory of controller 1616. Cropping the expected slosh 1614 at 1620 results in a rationalized expected slosh 1622.In addition to rationalized expected slosh 1622, an actual slosh 1628 may be determined based on the difference 1626 between the unprocessed standpipe coolant level 1624 and the coolant volume level 1625. Coolant levels 1624 and 1625 may be accessed via controller 1616. The actual slosh integral 1646 may be incremented based on the actual slosh 1628. The integral of the actual sloshing is described in more detail below. Rationalized expected slosh 1622 and actual slosh 1628 may serve as inputs to compensator 1630. Compensator 1630 may determine an assumed slosh 1632 based on inputs 1622 and 1628.In an example, compensator 1630 may compare sloshes 1622 and 1628, apply rationalized expected slosh 1622 as the assumed slosh 1632 under a first set of conditions, and apply actual slosh 1628 as the assumed slosh 1632 under a second set of conditions. For example, the first set of conditions may include that the sloshes 1622 and 1628 have the same sign (i.e., both are an estimate of a positive amount of slosh or both are an estimate of a negative amount of slosh) and that both sloshes are within the physical range of the standpipe 1618, but the rationalized expected slosh 1622 is of a smaller magnitude than the actual slosh 1628. The second set of conditions may include that the sloshes 1622 and 1628 have the same sign and that both sloshes are within the physical range of the standpipe 1618, but the actual slosh 1628 is of a smaller size than the rationalized expected slosh 1622.In another example, the compensator 1630 may set the rationalized expected slosh 1622 based on the actual slosh 1628, and apply the set amount of slosh as the assumed slosh 1632. Setting the rationalized expected slosh 1622 based on the actual slosh 1628 may include applying only a portion of the rationalized expected slosh 1622 as the assumed slosh 1632 if the expected slosh 1622 is greater than the actual slosh 1628. The actual slosh 1628 may be less than the rationalized expected slosh 1622 if fluid exchange between the degassing bottle and the standpipe is physically prevented. By applying only a portion of the rationalized expected slosh as the assumed slosh when the rationalized expected slosh is greater than the actual slosh, the accuracy of an estimate of the coolant volume level may be improved. If the expected slosh 1622 is less than the actual slosh 1628, adjusting the rationalized expected slosh 1622 based on the actual slosh 1628 may include compensating only the expected amount, where the expected amount is a conservative amount based on a predetermined mapping of the tendency of the vehicles to slosh.The assumed slosh 1632 may be applied to the unprocessed standpipe coolant level 1634 to determine the adjusted standpipe coolant level 1638. In an example, applying the accepted slosh 1632 to the unprocessed standpipe coolant level 1634 may include adding the accepted slosh 1632 to the unprocessed standpipe coolant level 1638. The filter 1640 may update the coolant volume level 1639 (accessible via the controller 1616) based on the adjusted standpipe coolant level 1638, and thereby determine the updated coolant volume level estimate 1642. Filtering the coolant volume level 1639 based on the adjusted standpipe coolant level 1638 may include determining a time constant based on the total size of slosh compensation applied to the current level measurement (e.g., more filtering if more compensation is applied) and further based on the signed magnitudes of the level measurement of the adjusted standpipe coolant level 1638 and the coolant volume level 1639. The coolant state 1660 may then be updated based on the updated coolant volume level estimate 1642, as described in more detail with respect to FIG. 18.Returning to the expected slosh integral 1644, the integral may be incremented based on the expected slosh size 1614. For example, the expected slosh integral 1644 may be incremented by an amount directly proportional to the expected slosh 1614. Similarly, the actual slosh integral 1646 may be incremented based on the actual slosh size 1628. The expected slosh integral 1644 and the actual slosh integral 1646 may be decremented at 1645 and 1647, respectively. In one example, each integral may be decremented by the same fixed amount in each measurement period, the fixed amount determined based on the compensation methods described at 1506 of FIG. 15. After integrals 1644 and 1646 are decremented at 1645 and 1647, sensor state 1650 may be determined based at least in part on the integrals. In one example, the ratio of the actual slosh integral 1646, the amount of the actual slosh integral, may be divided by the amount of the expected slosh integral, and determining the state of the sensor may be based on a comparison of this ratio to both an upper threshold and a lower threshold.FIG. 17 provides illustrations of various slosh conditions that the compensator 1630 of FIG. 16 may address. Plots 1710, 1720, 1730, 1740, show fluid levels based on the estimated sloshes (the dashed lines) and the actual sloshes (the solid lines). At 1710, the expected slosh 1712 is positive and greater than the maximum physical level of the standpipe, while the actual slosh 1714 is positive and is at the maximum physical level of the standpipe. During such a condition, the actual slosh 1714 may be applied as the presumed slosh for the measurement period because it may be the case that a temporary blockage in a hose (e.g., a fluid trap) or the actual end of the vertical standpipe (e.g., due to stack-up) has physically limited the amount of slosh.At 1720, both the expected slosh 1722 and the actual slosh 1724 are positive and are within the physical range of the standpipe, with the size of the expected slosh 1722 being greater than the size of the actual slosh 1724. Under such a condition, only a portion of the expected slosh may be applied as the presumed slosh for the measurement period.At 1730, both the expected slosh 1732 and the actual slosh 1734 are positive, with the size of the expected slosh 1732 being less than that of the actual slosh 1734. Under such a condition, the expected slosh 1732 may be applied as the assumed slosh for the measurement period.At 1740, both the expected slosh 1742 and the actual slosh 1744 are negative and are within the physical range of the standpipe. During such a condition, the actual slosh 1744 may be applied as the presumed slosh for the measurement period because there may be temporary blockage of the hose (e.g., a fluid trap). By selecting the slosh with the lower magnitude, preventing overcompensation for an expected slosh model can be achieved with inaccurate estimates of acceleration gain or position for slosh or for a temporarily clogged hose.FIG. 18 illustrates a routine 1800 for updating a coolant state based on the estimation of the coolant volume level and the current coolant state. The updated coolant volume level estimate may correspond to one or more coolant conditions. The coolant volume level estimate may be, for example, one of OK, LOW, EMPTY, UNKNOWN / DEGRADED, and DISTURBED. In this example, the coolant volume level estimate may be OK if it is above a higher threshold level, and may be LOW if it is below the higher threshold but above a lower threshold. Additionally, the coolant volume level estimate may be EMPTY if it is below a lower threshold. Additionally, an intermediate threshold may be included, as described below with respect to 1822 and 1826. In some examples, routine 1800 may only update the coolant state if an estimate of the coolant volume level corresponding to another coolant state has passed for longer than a threshold duration. Routine 1800 may be executed with a coolant system such as that described in FIGS. 2-9, and may be executed during each measurement period in which a valid estimate of the coolant volume level is determined after the estimate of the coolant volume level has been updated (such as via routine 1400 or control scheme 1600).Routine 1800 begins at 1802, where the estimate 1804 of the coolant volume level, the current coolant state 1806, and the temperature data 1808 are received from an engine controller. At 1810, the controller may determine whether the coolant system is faulty. The conditions indicating that the coolant system is out of order may include a lost connection to the controller area network that no echoes are received during the measurement period or an engine temperature that is above an upper threshold. If it is determined at 1810 that the coolant system is out of order, routine 1800 proceeds to 1812, where the controller may indicate that the coolant level is OUT OF ORDER. Routine 1800 may then update the coolant state based on the current coolant level and current coolant state at 1832. If it is determined at 1810 that the coolant system is not faulty, routine 1800 proceeds to 1814.Continuing at 1814, the controller may determine whether the ultrasonic level sensor is degraded or whether the coolant level is unknown during the current measurement period. Both conditions may correspond to a coolant level of UNKNOWN / DEGRADED. An ultrasonic level sensor may be determined to be degraded if, for example, the engine controller previously indicated a noisy sensor or a stuck sensor at 1512 or 1516 in routine 1500. Alternatively, sensor degradation may be determined if the expected amount of slosh indicates that the level of acceleration / position of the vehicle currently occurring is too high to compensate for (i.e., if the expected slosh indicates a transient out-of-range measurement). The coolant level may be determined to be UNKNOWN / DEGRADED if, for example, the raw estimate of the standpipe coolant level has been outside the physical range of the standpipe by more than a threshold amount, as described with respect to 1126 of FIG. 11, or alternatively if the expected slosh for the measurement period is greater than a threshold amount, the threshold amount determined based on the expected slosh being greater than a percentage of the total height of the standpipe (e.g., plus or minus 25 mm in a 100 mm standpipe). Additionally, the coolant level may be determined to be UNKNOWN if an insufficient number of valid pulse echoes have returned, but not for sufficient measurement periods to set the coolant level to a detected FAILED state for the sensor. If it is determined that the ultrasonic level sensor is degraded, or if it is determined that the estimate of the coolant volume level during the measurement period is unknown, the controller may indicate that the coolant level is UNKNOWN / DEGRADED at 1816. Routine 1800 may then update the coolant state based on the current coolant level and current coolant state at 1832, as described in more detail below. Returning to 1814, if the conditions do not indicate that the ultrasonic sensor is degraded and the estimate of the coolant volume level is known, routine 1800 proceeds to 1818.At 1818, the coolant volume level estimate is compared to an upper threshold level to determine if the coolant level is OK. The upper threshold level may be determined based on the predetermined correlation of the sensor measurement when a vehicle stationary on a horizontal ground is filled to the lowest acceptable factory recommended fill level. If the coolant volume level estimate is above the upper threshold level, the current coolant level may be indicated as OK at 1820. In some examples, the current coolant level may be indicated as OK only if the estimate of the coolant volume level is greater than the upper threshold level by more than a predetermined amount. Routine 1800 may then update the coolant state based on the current coolant level and current coolant state at 1832, as described in more detail below. Returning to 1818, if it is not determined that the coolant volume level estimate is above the upper threshold level, routine 1800 proceeds to 1822.At 1822, the coolant volume level estimate is compared to a mean threshold level to determine if the coolant level is LOW. It is noted that at 1822, it has already been determined that the coolant volume level estimate is below the upper threshold level. The average threshold level may also be referred to herein as the LOW threshold level. If it is determined that the coolant volume level estimate is above the LOW threshold, it may be indicated at 1824 that the coolant level is LOW. Routine 1800 may then update the coolant state based on the current coolant level and current coolant state at 1832, as described in more detail below. Returning to 1822, if it is not determined that the coolant volume level estimate is above the average threshold level, routine 1800 proceeds to 1826.At 1826, the coolant volume level estimate is compared to a lower threshold level to determine whether the coolant level is LOW or EMPTY. The lower threshold level may also be referred to herein as the EMPTY threshold level. It is indicated that at 1826, the coolant volume level estimate has been determined to be below the LOW threshold level. Thus, at 1826, it is determined whether the coolant volume level estimate is between the LOW and EMPTY threshold levels or is below the EMPTY threshold level. If the coolant volume level estimate is below the EMPTY threshold level, it is indicated at 1830 that the coolant level is EMPTY. Routine 1800 may then update the coolant state based on the current coolant level and current coolant state at 1832, as described in more detail below. Returning to 1826, if the estimate of the coolant volume level is determined to be above the lower threshold level, routine 1800 proceeds to 1828, where the coolant level is determined based on the coolant state.Specifically, at 1828, the controller may indicate that the coolant level is EMPTY if the coolant volume level estimate is above the EMPTY threshold level but is less than the OK threshold and the coolant state is EMPTY. If the coolant volume level estimate is above the EMPTY threshold and the coolant state is OK, the controller may indicate that the coolant level is OK. In this way, the coolant state may not be changed from EMPTY to LOW until the coolant volume level estimate is above the OK threshold.At 1832, the coolant state may be updated based on the coolant level. In some examples, the coolant state may only change after a coolant level indicating a new coolant state has passed during a threshold duration. In this way, the consistency of the coolant state may be improved by not changing the coolant state by a threshold based on short term fluctuations in coolant level. Because changing a coolant state may include adjusting engine parameters, a consistent coolant state may improve engine operating conditions. In one example, the threshold duration may be based on a threshold number of measurement periods. This threshold duration may be different for each coolant state or, alternatively, for each set of coolant states. As a non-limiting example, adjusting the coolant state from OK to LOW may require indicating a LOW coolant volume level during a different threshold number of measurement periods than adjusting the coolant state from LOW to EMPTY requires indicating an EMPTY coolant volume level.In some examples, restrictions may be imposed on changing coolant conditions. For example, the coolant state may only change to EMPTY if the coolant level has been indicated as EMPTY during a first threshold number of measurement periods, not indicated as either LOW or OK during a second threshold number of measurement periods, the second threshold number being greater than the first. In this way, transient wastes in an EMPTY area can be discarded from erroneously detecting an EMPTY state. Additionally, the coolant state may only change to EMPTY after the vehicle motion is detected and it is determined that the vehicle has an engaged gear during the current key cycle. In this manner, an operator of the vehicle may fill the system with coolant and allow it to move to a detected full OK state without having to continuously reset the control module to exit the EMPTY state if so a request.At 1834, engine operating parameters are adjusted based on the updated coolant state. In some examples, the coolant state may not have been updated during the measurement period, and engine parameters may have been maintained from the previous measurement period. However, if the coolant state has been updated, restrictions may be imposed or placed upon the engine's operating parameters. For example, if the coolant state has been updated from OK to EMPTY, commands for engine loads above a threshold load may not be permitted while the coolant state remains EMPTY to prevent overheating of the engine components. Adjusting engine operating parameters based on coolant state is described in more detail below with respect to FIG. 19. Then, routine 1800 ends.FIG. 19 provides routine 1900 for limiting engine operating parameters based on the coolant state determined by routine 1800. Routine 1900 may be executed for each measurement period, e.g., at 1834 of routine 1800. An engine controller may include a set of restriction modes and may select one mode from the set of modes based on the coolant state and the duration that the coolant system was in that coolant state. Selecting a restriction mode may include restricting an engine load to be below an upper threshold, and / or decreasing an injection pulse width for one or more fuel injectors by a threshold amount, and / or completely eliminating fuel injection for one or more fuel injectors and / or forcing the engine to operate in an idle mode, and / or displaying messages indicative of volumetric coolant level and selected restriction mode information to the vehicle operator. Displaying the messages to the vehicle operator may include both indicating any limitations imposed on engine / transmission operation (e.g., limits on power, torque, engine speed, available gears, etc.) and indicating that replenishment of coolant is required if it is in a LOW level state or indicating an immediate need to stop and add coolant if it is in an EMPTY level state. Selecting a restriction mode may also include tracking the duration during which the engine has operated under the current restriction mode.Routine 1900 begins at 1902 where the coolant state is retrieved from the engine controller. Retrieving the coolant state may include retrieving a duration during which the current coolant state has been active. At 1904, it is determined whether the coolant state has been changed during the current measurement period. If the coolant state has been changed, routine 1900 proceeds to 1908 where a restriction mode may be selected based on the coolant state and duration in the coolant state. Selecting the restriction mode is described in more detail below. If the coolant state was not changed during the current measurement period, routine 1900 proceeds to 1906.At 1906, the duration during which the current coolant state has been active is compared to one or more threshold durations. Additionally, the duration during which the current restriction mode has been active may be compared to one or more threshold durations. If a threshold duration has not been reached, routine 1900 proceeds to 1910 where operation in the current restriction mode may be maintained. Then, routine 1900 may end.Returning to 1906, if a threshold duration has been reached, routine 1900 proceeds to 1908 where a restriction mode may be selected based on the coolant state and the duration in the coolant state. It is noted that 1908 may also be reached if the coolant state was changed during the current measurement period. In one example, the set of constraint modes from which the engine controller may select may include at least a first, a second, and a third mode. In the first restriction mode, the engine controller may only indicate to the operator of the vehicle that the coolant volume level is low and that the vehicle should be brought to dealer omission without imposing restrictions on engine operating parameters such as engine load and fuel injection. Selecting the second constraint mode may include setting an upper threshold for engine loads and cutting fuel injection from one or more cylinders by eliminating fuel injection pulse width for those cylinders. The third restriction mode may include the second mode restrictions and may further restrict the engine to operate in an idle mode only.In some examples, operation in a particular constraint mode may not be exited until certain conditions are met. In one example, the second restriction mode may be exited only upon engine restart. Such an example may also include exiting operation in the third restriction mode upon visited a dealer lease. In such examples, selecting a constraint mode at 1908 may also be based on the current constraint mode. For example, the engine may operate in the second restriction mode, and the current coolant state may indicate operating in the first restriction mode. However, the engine controller may not choose to operate in the first mode based on the current operating in the second restraint mode.Selecting a restriction mode at 1908 may include selecting the above-mentioned first restriction mode if the coolant state is LOW or EMPTY. Selecting the first restriction mode may include operating in the first restriction mode during a threshold duration and selecting one of the second and third restriction modes based on engine conditions after a threshold duration.Selecting a restriction mode at 1908 may alternatively include operating in the second restriction mode if the coolant state has been EMPTY for more than a threshold duration. Selecting the second restriction mode may include operating in the second restriction mode during a threshold duration and selecting the third restriction mode after the threshold duration. The engine controller may also choose to operate in the second constraint mode if the last known state of the system was EMPTY and the current state was UNKNOWN / DEGRADED during a threshold duration, as this condition may be considered functionally equivalent to EMPTY.Selecting a restriction mode at 1908 may further include operating in the third restriction mode if the coolant state has been EMPTY for more than a threshold duration. Selecting the third restriction mode may include operating in the third restriction mode until the vehicle is brought to a dealer discharge. The controller may only choose to operate in the third restriction mode when the coolant state has been confirmed to be EMPTY. In this way, engine operating parameters may be constrained to avoid overheating in the engine.The technical effect of using a system configured with a coolant spill reservoir having an inner recess to hold a fluid and a vertical hollow tube positioned outside the reservoir and containing an inner recess to hold a fluid, wherein a lowermost level of the recess is positioned vertically below a lowermost level of the inner recess of the reservoir, and having a sensor coupled to the lowermost level of the inner recess of the tube is that the coolant level in the reservoir can be inferred more accurately. By fluidly coupling the standpipe to the spillover reservoir, fluid levels are allowed to level out in the two reservoirs, allowing the fluid height in the reservoir to be reflected in the fluid height of the vertical tube. By estimating the fluid height in the vertical tube using the transmission of ultrasonic signals and detecting their echoes, the sensor output is not grossly affected by the distortions that can affect the volume fluid reservoirs, such as the variations in temperature and motion. In addition, the technical effect of adjusting an estimate of the fluid level in the vertical hollow standpipe based on the motion parameters of the vehicle is that the fluid level may be better compensated for variations due to sloshing and that a vehicle actuator may be adjusted in response to the more accurate estimate of the fluid level. This also reduces erratic fluid level estimates produced due to fluid slosh. By limiting engine power based on the estimated fluid level over a duration, engine overheating due to low coolant levels in the reservoir may be reduced. In addition, undesired triggering of fault modes due to incorrect low measured values can likewise be avoided. By allowing a processor to estimate the fluid level in the standpipe based on the raw data and / or the processed data generated by the ultrasonic sensor, the accuracy and reliability of the estimation is improved. More specifically, the technical effect of receiving both the unprocessed, unprocessed echo times and the processed fluid level data from the sensor coupled to the vertical tube and generating an estimate of the fluid level based on the unprocessed echo times and the vehicle sensor data during some conditions, while during other conditions the estimate of the fluid level is generated based on the processed data is that the unprocessed data that is unreliable can be discarded and not used to estimate the fluid level. This increases the weight of the reliable data in the final estimate. Additionally, the sensor output power may be optimized based on the type of raw data collected at the sensor. Specifically, the technical effect of periodically transmitting a sensor signal from a bottom to a top of the vertical pipe, receiving an echo of the transmitted signal at the sensor, and adjusting a power of the periodically transmitted signals based on an average duration elapsed between the transmission and the receiving is that the sensor power may be adjusted to improve the number and quality of the first-order echoes generated while reducing the number of the second-order echoes generated. This improves the accuracy and reliability of estimating the fluid level while also providing the advantages of power reduction. Overall, coolant levels in an engine cooling system may be better monitored, improving engine performance.It should be noted that the example control and estimation routines included herein may be used with various configurations of the engine and / or vehicle system. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, the various acts, operations, and / or functions illustrated may be performed in the order illustrated, performed in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and / or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the engine control system, wherein the described acts are performed by executing the instructions in a system including the various components of the engine hardware in combination with the electronic controller.It is understood that the configurations and routines disclosed herein are exemplary in nature and that these specific embodiments are not to be considered in a limiting sense because numerous variations are possible. The above technique can be applied to, for example, V-6, I-4, I-6, V-12, Boxer-4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or characteristics disclosed herein.The following claims particularly point out certain combinations and sub-combinations which are considered novel and not obvious. These claims may refer to "a" element or "a first" element or its equivalent. Such claims should be understood to include inclusion of one or more such elements and neither require nor exclude two or more such elements. Further combinations and sub-combinations of the disclosed features, functions, elements and / or characteristics may be claimed through alteration of the present claims or through presentation of novel claims in this or a related application. Such claims, whether broader than, narrower than, or equal to the scope of the original claims, or different from the scope of the original claims, are also considered to be included within the scope of the present disclosure.Explanation of CharactersFIG. 11 1101 Beginning 1102 Sensor data receives 1104 number of qualified echoes 1106 first and second order echo times 1108 Sensor processed level estimate 1110 Sensor circuit and standpipe 1112 coolant temperatures quiescent conditions and a high number of qualified echoes? 1114 An estimate from the sensor as an unprocessed fluid level in standpipe apply 1116 Sufficient first order echoes to qualify locally? 1118 False identified second order echoes? 1120 The second order echoes in misidentified sets use 1122 Sufficient first order echoes to qualify locally? 1124 The unprocessed sensor data process, To determine the level (FIG. 12 ) 1126 Estimated level within physical range threshold? 1128 Invalid measurement for data period flag 1130 The level estimate based on the current data period does not update 1132 The latest estimate of the volume level uses 1134 estimation slightly outside the physical range? 1136 The estimate based on physical range clip 1138 Determine 1140 Average as the unprocessed fluid level in standpipe 1142 Estimate the volume level based on the unprocessed level and the accepted slosh (FIG. 14 ) 1144 end

Claims

An engine coolant system (101) comprising: a coolant spill reservoir (208) having an inner recess to retain a fluid; a vertical hollow tube (210, 310, 1304) positioned outside the reservoir (208) and including an inner recess to retain a fluid, a lowermost level of the recess being positioned vertically below a lowermost level of the inner recess of the reservoir (208); and a sensor (362) coupled to the lowermost level of the inner recess of the tube (210, 310, 1304), the system (101) further comprising a first hose (214) fluidly coupling an upper portion of the reservoir (208) to an upper portion of the vertical tube (210, 310, 1304); and a second hose (216) fluidly coupling the lowermost level of the container (208) to a lowermost level of the vertical tube (210, 310, 1304) such that a level of the fluid in the container (208) balances a level of the fluid in the vertical tube (210, 310, 1304).The system (101) of claim 1, further comprising a sensor (362) positioned within the internal recess of the tube (210, 310, 1304); and a processor communicatively coupled to the sensor (362) in the internal recess for estimating the fluid level in the vertical tube (210, 310, 1304) based on a sensor output.The system (101) of claim 1, wherein the first hose (214) is positioned perpendicular to a longitudinal axis of the vertical tube (210, 310, 1304), wherein the first hose (214) directly couples the top portion of the vertical tube (210, 310, 1304) to the top portion of the container (208) without an interposer.The system (101) of claim 3, wherein the second hose (216) directly couples the lowermost level of the vertical tube (210, 310, 1304) to the lowermost level of the container (208) via an intermediate connector such that a first portion of the second hose (216) on a connector side is oriented parallel to the vertical tube (210, 310, 1304), while a second portion of the second hose (216) on a tube side is oriented perpendicular to the vertical tube (210, 310, 1304).The system (101) of claim 1, wherein the coolant spillover reservoir (208) is a degassing bottle fluidly coupled to a cooler (80) via a relief valve, the degassing bottle (208) receiving coolant from the cooler (80) when a pressure in the cooler (80) is above a threshold, the degassing bottle (208) flowing coolant to the cooler (80) when the pressure in the cooler (80) is below a threshold.The system (101) of claim 2, wherein the sensor (362) is an ultrasonic sensor configured to transmit and receive an ultrasonic signal.The system (101) of claim 6, wherein the processor is configured to estimate the fluid level in the vertical tube (210, 310, 1304) based on an elapsed time since the sensor (362) sent the ultrasonic signal and the sensor (362) received an echo of the sent ultrasonic signal.The system (101) of claim 1, wherein a diameter of the upper portion of the vertical tube (210, 310, 1304) is less than a diameter of the lowermost level of the vertical tube (210, 310, 1304).The system (101) of claim 1, wherein the second tube (216) is coupled to the vertical tube (210, 310, 1304) at a location above the interior recess where the sensor (362) is housed.The system (101) of claim 2, wherein the interior cavity of the vertical tube (210, 310, 1304) is configured as a downward guiding structure, the cavity coupled via a spring retaining bracket (336) in the vertical tube (210, 310, 1304), the downward guiding structure positioned coaxial to the vertical tube (210, 310, 1304), wherein the sensor (362) and the processor are each positioned in a cavity of the downward guiding structure.The system (101) of claim 1, wherein the upper portion of the vertical tube (210, 310, 1304) comprises a protrusion offset on one side from the vertical tube (210, 310, 1304), wherein an axis of the protrusion is at an angle to the longitudinal axis of the vertical tube (210, 310, 1304), the angle being based on an angle of the vertical tube (210, 310, 1304) relative to a cross car beam, the protrusion comprising a receptacle for receiving a fastener (322), wherein the fastener (322) couples the vertical tube (210, 310, 1304) to the cross car beam.The system (101) of claim 11, further comprising a triangular wedge (326), the wedge (326) secured in a grid of the cross car beam at a location where the vertical tube (210, 310, 1304) is secured to the cross car beam, the wedge (326) secured by a bracket, the bracket comprising an opening for receiving the fastener (322) coupling the vertical tube (210, 310, 1304) to the cross car beam.A vehicle coolant system (101) comprising: a degassing bottle (208); a hollow vertically oriented tube (210, 310, 1304) comprising: an outer structure having a narrower diameter at an upper portion and a wider diameter at a lower portion; an inner structure coupled to the lower portion of the outer structure via a spring retainer bracket (336), the inner structure being coaxial with the outer structure and having a recess for accommodating a processor, an ultrasonic sensor (362), and a temperature sensor (367); a protrusion coupled on a side of the tube (210, 310, 1304) facing the degassing bottle (208) for securing the tube (210, 310, 1304) to a cross member of the vehicle (100); a circular lid (312) coupled to the upper portion of the outer structure, wherein an inner surface of the circular lid (312) has a smooth surface; a first hose (214) coupling the upper portion of the outer structure to an upper portion of the degassing bottle (208); a second hose (216) coupling the inner structure to a lower portion of the degassing bottle (208) via a T-connector, wherein a fluid level in the degassing bottle (208) balances with a fluid level in the vertical tube (210, 310, 1304) by fluid transfer through the first (214) and the second hose (216), and wherein the lower portion of the degassing bottle (208) is positioned higher than a lower portion of the inner structure of the vertical tube (210, 310, 1304); and a controller (12) having computer readable instructions stored in non-transitory memory for: receiving an indication of the fluid level in the degassing bottle (208) from the processor; and adjusting engine operation in response to the indication.The system (101) of claim 13, wherein the ultrasonic sensor (362) is configured to: transmit an ultrasonic signal to the top portion of the vertical pipe (210, 310, 1304); and receive an echo of the transmitted signal after reflection from a coolant-air interface.The system (101) of claim 14, wherein the processor is configured with code to: estimate the fluid level in the vertical tube (210, 310, 1304) based on an elapsed time period since the ultrasonic sensor (362) sends the ultrasonic signal and receives the echo at the ultrasonic sensor (362); and infer the fluid level in the degassing bottle (208) based on the estimated fluid level in the vertical tube (210, 310, 1304).A method for an engine coolant system (101), comprising: transmitting an ultrasonic signal from a sensor (362) located within a recess at a lowermost level of a vertical hollow tube (210, 310, 1304) to an upper portion of the tube (210, 310, 1304), the tube (210, 310, 1304) fluidly coupled to a coolant spillover reservoir (208) in a compartment (103) below the engine hood such that the lowermost level of the vertical tube (210, 310, 1304) is above a lowermost level of the coolant spillover reservoir (208); receiving an echo of the ultrasonic signal at the sensor (362) upon reflection from a lid coupled to the upper portion of the vertical tube (210, 310, 1304); estimating a time duration elapsed since the transmission of the ultrasonic signal and the receipt of the echo at the sensor (362); and concluding a coolant level in the reservoir (208) at a processor coupled to the sensor (362) in the vertical tube (210, 310, 1304) based on the estimated time duration.The method of claim 16, wherein the upper portion and the lower portion of the tube (210, 310, 1304) are fluidly coupled to the reservoir (208) via first (214) and second tubes (216), respectively, such that a fluid level in the reservoir (208) balances a fluid level in the tube (210, 310, 1304).The method of claim 17, wherein the inferting comprises inferring, at a processor, the coolant level in the vertical tube (210, 310, 1304) based on the estimated amount of time; and inferring, at the processor, the coolant level in the reservoir (208) based on the inferred coolant level in the vertical tube (210, 310, 1304).The method of claim 18, further comprising passing the inferred coolant level in the reservoir (208) from the processor to an engine controller (12); and adjusting an engine operating parameter in response to the inferred coolant level in the reservoir (208) by the engine controller (12).

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