PI Control Partial Derivative-Based I-Term for Windup Prevention

Abstract

The systems, devices, and methods described herein relate to heating and cooling of fuel cells for automobiles. A proportional-integral-derivative (PID) controller can be used to control the temperature of a fluid in the fuel cell. The PID is configured to calculate and control the saturation limit of the I-term of the PID controller to reduce integral windup.

Description

[Technical field]

[0001] The present disclosure relates to systems, devices, and methods for providing control of a proportional-integral-derivative (PID or PI) controller, and more particularly, to calculating and controlling the saturation limit of the I-term of a PID controller to reduce integral windup. [Background technology]

[0002] The emergence of new fuel cell technology has led to new advances in vehicle design. These advances include new hybrid vehicles that operate using a combination of an internal combustion engine and a motor-generator to further improve fuel efficiency, fully electric vehicles that operate based on power stored in a battery, and fuel cell vehicles that generate electricity by promoting a chemical reaction.

[0003] Many vehicles employ multiple fuel cells in a fuel cell stack. These fuel cells receive fuel, typically containing hydrogen, and oxygen or other oxidant. The fuel cell stack facilitates a chemical reaction between the hydrogen and oxygen. This chemical reaction produces electricity and water as a by-product. The electricity produced by the fuel cell stack is either stored in a battery or fed directly to a motor-generator to generate mechanical power to propel the vehicle. Fuel cell vehicles are a breakthrough in the automotive industry, but because the technology is relatively new, there is room for improvement in the technology.

[0004] It is desirable for fuel cells to operate within a given temperature range. If the temperature is too low, the fuel cell's power output may be relatively low as well. If the temperature is too high, the fuel cell may dry out, potentially damaging or destroying the fuel cell. Some existing fuel cell systems use proportional-integral-derivative (PID or PI) controllers to maintain the fuel cell temperature within an optimal temperature range. However, these systems are not optimized for the highly nonlinear conditions that typically occur in fuel cell systems. In particular, integral (I-term) windup poses serious challenges for these systems.

[0005] Therefore, there is a need in the art for a system and method for accurately controlling the temperature of a fuel cell stack used in a vehicle using a PID controller, and in particular, for a system and method for preventing integral windup. Summary of the Invention [Means for solving the problem]

[0006] In some exemplary aspects, the present disclosure introduces a system for heating or cooling a fuel cell stack of a vehicle, the system may include a fuel cell stack having a plurality of fuel cells, an actuator having an actuator position and configured to increase or decrease a fluid temperature of a fluid in the plurality of fuel cells, and an electronic control unit (ECU) coupled to the actuator, the ECU including a proportional-integral-derivative (PID) controller, wherein the ECU is configured to determine a temperature control signal corresponding to a target temperature of the fluid, perform feedforward control of the actuator such that the actuator increases or decreases the fluid temperature toward the target temperature of the fluid, receive a feedback control signal from the PID controller, the feedback control signal being based on an error signal corresponding to an additional change in the actuator position that increases or decreases the fluid temperature to reduce a temperature difference, the feedback control signal applying an I-term saturation limit, and configured to control the actuator based on a sum of the feedforward control signal and the feedback control signal.

[0007] In some embodiments, the PID controller is configured to generate the feedback control signal taking into account a current error value, a past error value, and a potential future error of the error signal. The PID controller may be configured to apply an I-term saturation limit according to the following equation:

[0008]

number

[0009] The PID controller can be configured to apply the I-term saturation limit to the final PI combined feedback term according to the following equation:

[0010]

number

[0011] The actuator may be a three-way valve, and the target temperature of the fluid and the fluid temperature correspond to the fluid at an inlet to the fuel cell stack.

[0012] An exemplary method for heating or cooling a fuel cell stack of a vehicle is also provided, including providing a fuel cell stack having a plurality of fuel cells; providing an actuator having an actuator position and configured to increase or decrease a fluid temperature of a fluid in the plurality of fuel cells; providing an electronic control unit (ECU) coupled to the actuator, the ECU including a proportional-integral-derivative (PID) controller; the ECU determining a temperature control signal corresponding to a target temperature of the fluid; the ECU performing feedforward control of the actuator such that the actuator increases or decreases the fluid temperature toward the target temperature of the fluid; the ECU receiving a feedback control signal from the PID controller, the feedback control signal increasing or decreasing the fluid temperature based on an error signal corresponding to an additional change in the actuator position to reduce a temperature difference, the feedback control signal applying an I-term saturation limit; and controlling the actuator based on a sum of the feedforward control signal and the feedback control signal.

[0013] In some embodiments, the method further includes generating the feedback control signal with the PID controller considering a current error value, a past error value, and a potential future error of the error signal. The method can include applying an I-term saturation limit with the PID controller according to the following equation:

[0014]

number

[0015] The method can include applying the I-term saturation limit to a final PI combined feedback term using the PID controller according to the following equation:

[0016]

number

[0017] In some embodiments, the actuator may be a three-way valve, and the target temperature of the fluid and the fluid temperature may correspond to the fluid at an inlet to the fuel cell stack.

[0018] An exemplary system for heating or cooling a fuel cell circuit of a vehicle is also provided, including a fuel cell stack having a plurality of fuel cells and configured to receive and heat a fluid; an actuator having an actuator position and configured to increase or decrease a fluid temperature of the fluid; and an electronic control unit (ECU) connected to the actuator, the ECU configured to determine a temperature control signal corresponding to a target temperature of the fluid; perform feedforward control of the actuator such that the actuator increases or decreases the fluid temperature toward the target temperature of the fluid; determine a temperature difference between the fluid temperature of the fluid and the target temperature of the fluid; determine a sensitivity to a change in a parameter value or the actuator position corresponding to a change in the fluid temperature; apply the sensitivity to the temperature difference to determine an error signal corresponding to an additional change in the actuator position to increase or decrease the fluid temperature to reduce the temperature difference; receive a feedback control signal from a PID controller, the feedback control signal based on the error signal, the feedback control signal configured to apply an I-term saturation limit, and control the actuator based on the error signal.

[0019] In some embodiments, the PID controller is part of the ECU. The PID controller may be configured to generate the feedback control signal taking into account a current error value, a past error value, and potential future errors of the error signal. The PID controller may be configured to apply the I-term saturation limit according to the following equation:

[0020]

number

[0021] The PID controller can be configured to apply the I-term saturation limit to the final PI combined feedback term according to the following equation:

[0022]

number

[0023] In some embodiments, the actuator is a three-way valve. The target temperature of the fluid and the fluid temperature may correspond to the fluid at an inlet of the fuel cell stack. The ECU may be further configured to control the actuator based on a sum of the feedforward control signal and the feedback control signal. [Brief description of the drawings]

[0024] Other systems, methods, features, and advantages of the present invention will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. Components illustrated in the drawings are not necessarily to scale and may be exaggerated to better illustrate the key features of the present invention. In the drawings, the same reference numbers refer to the same parts throughout the different views.

[0025] [Figure 1] FIG. 1 is a block diagram showing the components of a vehicle equipped with a fuel cell circuit capable of generating electricity based on a chemical reaction according to one embodiment of the present invention.

[0026] [Diagram 2] FIG. 2 is a block diagram illustrating various features of the fuel cell circuit of FIG. 1 in accordance with one embodiment of the present invention.

[0027] [Diagram 3] FIG. 3 is a block diagram illustrating various logic components of an electronic control unit (ECU) of the vehicle of FIG. 1 for increasing or decreasing the temperature of a fluid in a fuel cell circuit according to one embodiment of the present invention.

[0028] [Figure 4] FIG. 4 is a flow chart illustrating a method for heating or cooling a fuel cell circuit according to one embodiment of the present invention.

[0029] [Diagram 5] FIG. 5 is a block diagram showing a three-way valve controller that feedback controls three valves in a fuel cell circuit according to one embodiment of the present invention.

[0030] [Figure 6] FIG. 6 is a block diagram illustrating control logic for heating or cooling a fuel cell circuit according to one embodiment of the present invention. [Figure 7] FIG. 7 is a block diagram illustrating control logic for heating or cooling a fuel cell circuit according to one embodiment of the present invention. [Figure 8] FIG. 8 is a block diagram illustrating control logic for heating or cooling a fuel cell circuit according to one embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram illustrating control logic for heating or cooling a fuel cell circuit according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present disclosure describes systems and methods for heating and cooling fuel cells in a fuel cell circuit. In particular, the present disclosure describes systems and methods that provide feedback control of actuators in a fuel cell circuit to increase or decrease fluid temperature. The system provides various benefits and advantages, such as adjusting the control of different actuators based on the difference in temperature at different locations, resulting in more accurate control of the actuators. The system further advantageously prevents windup of the I term by calculating and controlling the I term as described herein. In particular, saturation of the I term can be based on system sensitivity (partial derivatives), allowing the limit to be increased / decreased in proportion to the system response. A tolerance learning limit based on the controlled state can be defined, and the partial derivatives translate the limits of the controlled state to PI control states. In addition to saturation of the I term, partial derivative scaling methods can also be applied to the final PI coupled feedback term.

[0032] An exemplary system includes a fuel cell stack and an actuator that can increase or decrease the temperature of a fluid flowing through the fuel cell stack. The system further includes an electronic control unit (ECU). The ECU can include a PID controller. The ECU can determine a desired temperature of the fluid and a feedforward control signal to control the actuator to move the fluid temperature toward the desired temperature. The ECU can also determine a temperature difference between the fluid temperature at a location and a desired temperature at the location, as well as a sensitivity. The ECU then applies a sensitivity to the temperature difference to determine an error signal corresponding to an error in the actuator position, and then controls the actuator based on the error signal to move the fluid temperature toward the desired temperature. The ECU can also receive feedback from the PID controller, including an I-term based on a partial derivative to prevent integral windup. PID feedback control is described in detail in U.S. Pat. No. 10,720,655, which is incorporated by reference herein in its entirety. Further methods for heating and cooling a vehicle fuel cell circuit are described in U.S. Pat. No. 10,777,831, which is incorporated by reference herein in its entirety.

[0033] 1 shows a diagram of a vehicle 100 including components of a system 101 for controlling the temperature of a fuel cell in the vehicle 100. In some embodiments, the vehicle 100 and system 101 include an ECU 102, a memory 104, a speed sensor 106, and a temperature sensor 108. The vehicle 100 also includes a power source 110, which may include at least one of an engine 112, a motor / generator 114, a battery 116, or a fuel cell circuit 118.

[0034] The ECU 102 is connected to each component of the vehicle 100 and may include one or more processors or controllers specifically designed for automotive systems. The functionality of the ECU 102 may be implemented in a single ECU or multiple ECUs. The ECU 102 may receive data from the components of the vehicle 100, make decisions based on the received data, and control the operation of the components based on the decisions. In that regard, the ECU 102 may control various aspects of the system 101 as well as aspects of the vehicle itself (e.g., steering, braking, acceleration, etc.).

[0035] Memory 104 may include any non-transitory memory known in the art, and in that regard, memory 104 may store machine-readable instructions usable by ECU 102, as well as other data as required by ECU 102.

[0036] The speed sensor 106 may be any speed sensor capable of detecting data usable to determine the speed of the vehicle 100. For example, the speed sensor 106 may include a GPS sensor or an IMU sensor. The speed sensor 106 may additionally or alternatively include an angular velocity sensor configured to detect the angular velocity of the wheels or engine of the vehicle 100, a speedometer, or the like.

[0037] Temperature sensor 108 may include one or more temperature sensors capable of detecting data usable to determine an ambient temperature inside a portion of vehicle 100 or outside of vehicle 100. For example, temperature sensor 108 may include a thermocouple, a thermometer, an infrared temperature sensor, a thermistor, etc.

[0038] The engine 112 can convert fuel into mechanical power. In this regard, the engine 112 can be a gasoline engine, a diesel engine, etc. The battery 116 can store electrical energy. In some embodiments, the battery 116 includes one or more energy storage devices, including a battery, a flywheel, a supercapacitor, a thermal storage device, or other energy storage device.

[0039] The fuel cell circuit 118 may include multiple fuel cells that facilitate chemical reactions to generate electrical energy. In that regard, the electrical energy generated by the fuel cell circuit 118 may be stored in the battery 116. In some embodiments, the vehicle 100 may include multiple fuel cell circuits, including the fuel cell circuit 118.

[0040] The motor / generator 114 can convert electrical energy stored in the battery (or electrical energy received directly from the fuel cell circuit 118) into mechanical power that can be used to propel the vehicle. The motor / generator 114 can further convert mechanical power received from the engine 112 or the wheels of the vehicle into electricity, which can be stored as energy in the battery 116 and / or used by other components of the vehicle. In some embodiments, the motor / generator 114 can additionally or instead include a turbine or other device capable of generating thrust.

[0041] Further details of the fuel cell circuit 118 are shown in FIG. 2. In some embodiments, the fuel cell circuit 118 includes a fuel cell stack 200 having a plurality of fuel cells. Each fuel cell can facilitate a chemical reaction to generate electricity. The reaction can generate heat. Additionally, a fluid can flow through the fuel cell stack 200 to allow at least a portion of the heat to escape from the fuel cell stack 200. In this regard, the fuel cell stack 200 can include an inlet 228 for receiving a fluid and an outlet 230 through which the fluid can exit the fuel cell stack 200.

[0042] It may be desirable for the fuel cell stack 200 to operate within a certain temperature range. For example, it may be desirable for the fuel cells in the fuel cell stack 200 to operate in the range of 50 degrees Celsius (50° C., 122 degrees Fahrenheit (122° F.)) to 80° C. (176° F.).

[0043] Fuel cell stack 200 can generate more electrical energy at relatively high temperatures (i.e., when the temperature is closer to 80° C. than 50° C.). However, fuel cell stack 200 may experience undesirable moisture loss (i.e., drying out) when operated at these relatively high temperatures. In this regard, it may be desirable to operate fuel cell stack 200 at temperatures closer to 80° C. when relatively large amounts of electrical energy are required, and closer to 50° C. when relatively small amounts of electrical energy are required. Fuel cell circuit 118 includes various features for increasing or decreasing the temperature of fuel cell stack 200.

[0044] The fuel cell circuit 118 may further include an intercooler 202. The intercooler 202 may be disposed in parallel with the fuel cell stack 200. The intercooler 202 may receive a hot air stream 203 (i.e., an air stream with a higher temperature than the temperature of the fluid in the intercooler 202) and may transfer heat from the hot air stream 203 to the fluid. Thus, the fuel cell stack 200 and the intercooler 202 may be considered heating elements of the fuel cell circuit 118, since they both increase the temperature of the fluid. All fluids in the fuel cell circuit 118 eventually flow through the combination of the fuel cell stack 200 and the intercooler 202, as indicated by arrow 205.

[0045] The fuel cell circuit 118 further includes an actuator, which may be a three-way valve 204. The fuel cell circuit 118 may also include one or more radiators 210 and a bypass branch 206 that bypasses the one or more radiators 210. The three-way valve 204 may divide the fluid between the radiator 210 and the bypass branch 206 based on a valve position of the three-way valve 204. The three-way valve 204 may have multiple valve positions that divide the flow rate between the bypass branch 206 and the radiator 210 in different ratios.

[0046] For example, the three-way valve 204 may have a first position in which 80% of the fluid flows through the bypass branch 206 (indicated by arrow 207) and 20% of the fluid flows through the radiator 210 (indicated by arrow 209). The three-way valve 204 may further have a second position in which 70% of the fluid flows through the bypass branch 206 and 30% of the fluid flows through the radiator 210. The three-way valve 204 may have multiple discrete valve positions or may have an infinite continuous valve position (i.e., any value between 0% and 100% of the fluid may flow through each of the bypass branch 206 or the radiator 210).

[0047] The fluid flowing through the bypass branch 206 may avoid the radiator 210, allowing most of the heat in the fluid to remain within the fluid. The ionizer 208 may receive a portion of the fluid flowing through the bypass branch 206. The ionizer 208 may function as an ion exchanger, removing ions from the fluid to reduce its electrical conductivity. In this respect, the ionizer may be referred to as a deionizer.

[0048] The radiator 210 may transfer heat from a fluid to a gas (such as air) passing over or through the radiator 210. In this regard, the radiator 210 may be referred to as the cooling element of the fuel cell circuit 118.

[0049] In some embodiments, the radiator 210 may include a main radiator 212 and two sub-radiators 214, 216. The fan 218 may be oriented to cause the gas 219 to flow over the radiator 210. In some embodiments, the fan 218 may be oriented to cause the gas 219 to flow only over the main radiator 212. The main radiator 212 has a fluid inlet 232 through which fluid enters the main radiator 212 and a fluid outlet 234 through which fluid exits the main radiator 212. The main radiator 212 may further include an air inlet 236 that receives the gas 219 (i.e., airflow) from the fan 218 and an air outlet 238 through which the airflow exits the main radiator 212.

[0050] 1 and 2, one or more of the radiators 210 may further receive an airflow 122 received through the grille 120 of the vehicle 100. As mentioned above, the speed of the airflow 122 corresponds to the speed of the vehicle 100. As the speed of the vehicle 100 increases, the speed of the airflow 122 further increases, increasing the transfer of heat from the fluid.

[0051] 2, the fuel cell circuit 118 can further include a pump 220. The pump 220 can include any pump capable of forcing a fluid through the fuel cell circuit 118. For example, the pump 220 can include a hydraulic pump, a diaphragm pump, a piston pump, a rotary gear pump, etc.

[0052] The fuel cell circuit 118 may further include a reservoir 240. A reservoir may include a volume for storing a fluid, such as a coolant. The fluid may be supplied to the fuel cell circuit 118 from the reservoir 240. In some embodiments, the reservoir 240 may include a port through which a user of the vehicle can supply fluid to the reservoir 240.

[0053] The fuel cell circuit 118 may further include two temperature sensors, including a first temperature sensor 224 and a second temperature sensor 226. The first temperature sensor 224 may detect the temperature of the fluid exiting the outlet 230 of the fuel cell stack 200. The second temperature sensor 226 may detect the temperature of the mixed fluid exiting the radiator 210. In some embodiments, more or fewer temperature sensors may be used and the temperature sensors may be located in additional or alternative locations.

[0054] 1 and 2, the ECU 102 may determine a target temperature for the fuel cell stack 200 based on the received power request of the vehicle 100. As discussed above, when a relatively large amount of power is requested from the fuel cell stack 200, it may be desirable for the temperature of the fuel cell stack 200 to increase because an increase in temperature corresponds to an increase in the power output of the fuel cell stack 200. Similarly, when a relatively small amount of power is requested from the fuel cell stack 200, it may be desirable for the temperature of the fuel cell stack 200 to decrease in order to retain moisture within the fuel cell stack 200.

[0055] The ECU 102 also receives the detected temperatures from the first temperature sensor 224 and the second temperature sensor 226. The ECU 102 controls the actuators (the three-way valve 204, the fan 218, and the pump 220) of the fuel cell circuit 118 to increase or decrease the temperature of the fuel cell stack 200 (such as the temperature of the fluid at the outlet 230). The ECU 102 increases or decreases the temperature towards the target temperature based on the target temperature and the detected temperature.

[0056] The three-way valve 204 can be used to regulate the temperature of the fluid by allowing more fluid to flow to the bypass branch 206 or to the radiator 210. For example, if the three-way valve 204 increases the flow rate of the fluid through the bypass branch 206, the overall temperature of the fluid may increase because the fluid will flow back to the heating element without significant heat loss. Similarly, if the three-way valve 204 increases the flow rate of the fluid through the radiator 210, the overall temperature of the fluid may decrease because more fluid is forced to the radiator 210, removing thermal energy from the fluid.

[0057] In some embodiments, the three-way valve is driven by the ECU 102, and in particular, is driven according to one or more of a feedforward signal and a feedback signal. The feedback signal may be calculated by a PID controller implementing a partial differential I term to reduce or prevent integral windup during the heating or cooling process, as shown more particularly with reference to FIG.

[0058] The fan 218 may similarly be used to regulate the temperature of the fluid by increasing or decreasing the flow rate of the gas 219 over the main radiator 212. For example, increasing the speed of the fan 218 (increasing the amount of gas 219 flowing over the main radiator 212) may decrease the temperature of the fluid as more thermal energy is transferred from the fluid. Similarly, decreasing the speed of the fan 218 may increase the temperature of the fluid as less thermal energy is transferred from the fluid.

[0059] The pump 220 is also used to indirectly regulate the temperature of the fluid by increasing or decreasing the flow rate, e.g., mass flow rate, of the fluid through the fuel cell circuit 118. Increasing the flow rate increases heat transfer between the fluid and various components, which may increase or decrease the temperature based on the amount of fluid passing through the bypass branch 206 or radiator 210 and the temperature of the fuel cell stack 200. Thus, the temperature of the fluid may correspond to the flow rate of the fluid.

[0060] 2 and 3, the ECU 102 may include a temperature control system 303 that controls the temperature of the fuel cell circuit 118. The temperature control system 303 may be implemented using specially designated hardware in the ECU 102 or may be implemented using general hardware in the ECU 102.

[0061] The temperature control system 303 may include a high-level controller 300, a state mediator 304, a state governor 308, a feedforward control 312, a feedback control 316, a state estimator 320, an observer 322, and an actuator control 330. The temperature control system 303 may receive inputs, such as a power request 301, and generate outputs, such as an actuator control signal 334.

[0062] The upper controller 300 receives a power request 301. The upper controller 300 determines a target temperature for the fuel cell stack 200 based on the power request 301. For example, if the power request is relatively large, the upper controller 300 sets the target temperature to a relatively high temperature, such as 75° C. (167° F.). Similarly, if the power request is relatively small, the upper controller 300 sets the target temperature to a relatively low temperature, such as 55° C. (131° F.). The upper controller 300 outputs an unfiltered target fuel cell temperature 302.

[0063] The state mediator 304 may receive the unfiltered target fuel cell temperature 302. The state mediator 304 may filter the received signal and output the target fuel cell temperature 306. The state mediator 304 may filter the unfiltered target fuel cell temperature 302 for various reasons. For example, filtering may remove noise on the signal or act as a bandpass filter to ensure that the target fuel cell temperature 306 is within a safe temperature range. The safe temperature range is a temperature range that is unlikely to cause damage to components of the fuel cell circuit 118 (i.e., due to overheating or drying out) and may correspond to a temperature range at which the fuel cell circuit 118 can generate power.

[0064] The state governor 308 may receive a target fuel cell temperature 306. The state governor 308 may generally dictate how quickly the temperature of the fluid in the fuel cell circuit 118 responds to a temperature change request (i.e., how quickly the temperature increases or decreases). The state governor 308 may output a temperature change rate 310 that corresponds to a desired rate of temperature change of the fluid (such as at the inlet 228 or outlet 230 of the fuel cell stack 200). For example, the temperature change rate 310 may be measured in degrees (e.g., degrees Celsius) per second.

[0065] The state estimator 320 can receive inputs including sensor values ​​326 and current actuator positions 328 (or commanded actuator positions) to estimate states at various locations in the fuel cell circuit 118. The sensor values ​​include, for example, temperatures detected from the first temperature sensor 224 and the second temperature sensor 226. The actuator positions 328 can be received from the actuators 332 themselves (the pump 220, the three-way valve 204, and the fan 218) or from actuator control signals 334.

[0066] The fuel cell circuit 118 includes a relatively small number of sensors. Additional data is required to optimally control the actuator 332. In this regard, the state estimator 320 can calculate or predict the additional data (i.e., the current state) based on the sensor values ​​326 and the actuator positions 328. For example, the state estimator 320 can calculate or predict the temperature at the positions of the fuel cell circuit 118 where no temperature sensor is present. As another example, the state estimator 320 can calculate or predict the pressure of the fluid at various positions of the fuel cell circuit 118. As yet another example, the state estimator 320 can further calculate or predict the amount of heat added or subtracted from the fluid by various elements of the fuel cell circuit 118. The state estimator 320 can output a calculated or predicted value 324 corresponding to the current state of the fuel cell circuit 118.

[0067] The feedforward control 312 may receive the temperature rate of change 310 from the state governor 308 and the calculated or predicted value 324 from the state estimator 320. In some embodiments, the feedforward control 312 may further receive a detected temperature from a temperature sensor. The feedforward control 312 may determine desired positions of the actuator 332 to achieve a desired temperature rate of change 310 of the fluid in the fuel cell circuit 118. The feedforward control 312 may determine these desired positions based on the received temperature rate of change 310 and the calculated or predicted value 324. The feedforward control 312 may output a feedforward control signal 314 corresponding to the determined desired position of the actuator 332.

[0068] The feedback control 316 may also receive the temperature rate of change 310 from the state governor 308 along with a calculated or predicted value 324 from the state estimator 320. In some embodiments, the feedback control 316 may further receive a detected temperature from a temperature sensor. The feedback control 316 may identify whether the actuator 332 is achieving the desired temperature rate of change 310. The feedback control 316 may further generate a feedback control signal 318 corresponding to an adjustment of the actuator 332 to close a gap between the measured temperature rate of change and the desired temperature rate of change 310.

[0069] The observer 322 may act as a feedback control for the radiator 210. In that regard, the observer may determine the difference between the detected temperature at the outlet 227 of the radiator 210 and the estimated temperature at the outlet 227 as determined by the state estimator 320. The observer 322 may then modify the value determined by the state estimator 320 so that the estimated temperature approaches the detected temperature.

[0070] The actuator control 330 can receive the feedforward control signal 314 and the feedback control signal 318 and generate the actuator control signal 334 based on a combination of the feedforward control signal 314 and the feedback control signal 318. One or more of the actuator control signals 334 can be sent to each actuator 332. For example, the actuator control signal 334 can include a first signal that controls a valve position of the three-way valve 204, a second signal that controls a fan speed of the fan 218, and a third signal that controls a pump speed of the pump 220. In some embodiments, the actuator control 330 can generate the actuator control signal 334 by summing the feedforward control signal 314 and the feedback control signal 318.

[0071] 4 shows a method 400 for feedback-based heating or cooling of a fuel cell circuit. The fuel cell circuit may be the fuel cell circuit shown in Figures 1 and 2. In some embodiments, the method 400 is performed by a feedback control, such as the feedback control 316 of Figure 3.

[0072] Method 400 may include step 402, in which the ECU determines a temperature control signal corresponding to a desired temperature of a fluid in the fuel cell circuit. For example, the temperature control signal may correspond to a desired temperature of the fluid and may include, for example, a rate of temperature change. In some embodiments, the temperature control signal is determined based on a desired temperature of the fluid at one or more locations, such as an inlet to the fuel cell stack. The temperature control signal is determined using a state governor, such as state governor 308 of FIG. 3.

[0073] Method 400 may include step 404, in which the ECU performs feedforward control of an actuator to increase or decrease the fluid temperature based on the temperature control signal. For example, the ECU may determine the feedforward control signal using a feedforward control, such as feedforward control 312 of FIG. 3. The feedforward control may be based on the temperature control signal and an estimate calculated using a state estimator (such as state estimator 320 of FIG. 3). In some embodiments, the ECU uses feedforward control to directly control one or more actuators of the fuel cell circuit. In some embodiments, the ECU uses a combination of feedforward control and feedback control to directly control one or more actuators.

[0074] The method 400 may include a step 406 of sensing a fluid temperature of the fluid at one or more locations by a temperature sensor or calculated by an ECU, such as a state estimator.

[0075] Method 400 may include the ECU determining 408 a temperature difference between a detected or calculated temperature of the fluid at one or more locations and a desired temperature of the fluid. For example, the ECU may determine a temperature difference between a detected or calculated temperature at an outlet of the fuel cell stack and a desired temperature of the fluid at the outlet of the fuel cell stack.

[0076] The method 400 may include a step 410 in which the ECU determines or calculates a sensitivity. The sensitivity may correspond to or relate to a change in actuator position (including a physical change in actuator position, a change in an actuator control signal, or a change in a parameter value used to determine the actuator control signal) and a change in fluid temperature. For example, the sensitivity may indicate the extent to which a change in actuator position of an actuator changes the fluid temperature of a fluid by one degree. As another example, the sensitivity may indicate the extent to which a change in mass flow rate changes the fluid temperature of a fluid by one degree.

[0077] Method 400 may include an optional step 412 in which the ECU divides the sensitivity by a time delay. This is particularly useful when the temperature of the fluid is detected by a sensor because the temperature of the fluid detected by the sensor may be delayed by one or more seconds, for example, one to five seconds. In this regard, if the control of the actuator is based on a time delayed sensor reading, the actuator control may oscillate due to the delayed reading. Dividing the sensitivity by the time delay results in a more gradual change in the actuator control, reducing the possibility of actuator control oscillation.

[0078] In some embodiments, step 412 may be skipped, especially if the fluid temperature is calculated by the ECU rather than detected by a sensor with a time delay, since there may be a relatively small delay, if any, in the calculation of the fluid temperature, and therefore no time delay operation is required since the actuator control is based on a more current reading.

[0079] The temperature difference determined in step 408 may correspond to a temperature error. In other words, the temperature difference corresponds to an error because it is the difference between the desired temperature at the location and the actual temperature. In this regard, in step 414, a sensitivity may be applied to the temperature difference to determine an error signal. The error signal may correspond to or indicate an error in the actuator position or an error in a parameter used to calculate the actuator position that caused the temperature difference. For example, the error signal may indicate that a pump is pumping fluid through the fuel cell circuit at too low or too high a mass flow rate. The error signal may further indicate or correspond to a difference in mass flow rates such that the actual temperature of the fluid is relatively equal to the desired temperature of the fluid.

[0080] Method 400 may include step 416, in which the ECU passes the error signal to a proportional, integral, and derivative (PID or PI) controller to generate a feedback control signal. The PID controller may analyze past and present values ​​of the error signal and generate a feedback control signal based on these values. In particular, the PID controller may analyze a proportional term (P term), which is proportional to the current value of the error signal, an integral term (I term), which takes into account past values ​​of the error signal and integrates them over time, and a derivative term (D term), which provides a potential future error of the error signal based on the current rate of change of the error signal. The controller may balance the effects of the P term, I term, and D term to optimize their control functions.

[0081] Integral windup is a challenging problem for many PID controllers, especially for highly nonlinear systems such as fuel cell temperature control. These systems may have highly nonlinear behavior that is not adequately captured by traditional methods. Existing systems that use PID controllers to manage temperature typically have static upper and lower limits set without including any learning values, which can exacerbate the integral windup problem. In particular, this phenomenon can be triggered by large changes in the set point, which can cause the I term to accumulate large errors over time, resulting in significant overshoot or undershoot.

[0082] In some embodiments, the I term and total PI feedback (including the sum of the P and I terms) are saturated using partial derivative calculations to capture the sensitivity and nonlinearity of the system. In these embodiments, the I term of the PID controller can be calculated by traditional methods and / or partial derivative methods. This allows for scaling of the I term saturation based on the system sensitivity, and the upper and lower limits can be increased or decreased proportionally to the system response. Defining an I term saturation limit can have the effect of optimizing the system for nonlinear systems and can help prevent integral windup in fuel cell control systems, as described herein. Setting the I term saturation limit can be done using the following equation:

[0083]

number

[0084] The partial differential terms (∂I-term state ) / (∂Controlled state ) can be calculated in real time based on the system state. The partial derivative terms represent the system sensitivity at the current system state and can capture the nonlinearity of the system.

[0085] The ΔControlled state allowedThe term represents how much the I term can contribute to eliminating the control state error. This prevents integral windup by limiting the accumulation of the I term error during the calculation process. For example, if the controlled state is the fuel cell (FC) inlet temperature, then ΔControlled state allowed = 10, the I-term can only grow enough to overcome the FC inlet temperature error of ±10°C. In this example, the partial derivative term (∂I-term state ) / (∂Controlled state )) dynamically scales the limit on the I term so that the I term can only accumulate the equivalent of ±10°C error under controlled conditions.

[0086] In some embodiments, the same method of scaling the I term (e.g., according to Equations 1-3) can be applied to the final total PI combined feedback term (also called the PI control value, which may include the sum of the P and I terms), for example using the following equation:

[0087]

number

[0088] Method 400 may include step 418, in which the ECU controls the actuator based on the feedback control signal. For example, the ECU may generate a sum of a feedforward control signal and a feedback control signal and control the actuator based on the sum. In some embodiments, the ECU may control the actuator based only on the feedback control signal. In some exemplary embodiments, method 400 may include returning to step 402 after completing step 418 and performing the steps again.

[0089] Referring to Figure 5, a three-way controller 500 is shown. In some embodiments, the three-way controller 500 may be included in the ECU 102 of Figure 2 and may, among other things, perform the feedback control 316. The three-way valve controller 500 may include logic or dedicated hardware designed to perform a method similar to the method 400 of Figure 4 to perform feedback control of the three-way valve.

[0090] The three-way valve controller 500 may include a number of calculation blocks 502, 510, 524, 532 that receive various input and output signals. These calculation blocks include the measured or calculated fluid temperature (T FC in For example, the fluid temperature 504 may be calculated by a state estimator in the ECU 102. The difference block 502 may include a difference block 502 that receives a desired temperature (T FC in_cmd ) 506. The difference block 502 may further receive a temperature difference (ΔT FC in error ) 508. In some implementations, the temperature difference 502 represents the amount of error compared to an expected fluid temperature.

[0091] The three-way valve controller 500 may further include a second differential block 510. The second differential block 510 calculates a radiator temperature (T rad out ) 512. The second difference block 510 can receive a bypass fluid temperature (T bypass ) 514. In some embodiments, the second difference block 510 outputs a difference 516 between the radiator temperature 512 and the bypass fluid temperature 514.

[0092] The three-way valve controller 500 may further include a sensitivity block 518. The sensitivity block 518 is a function of the difference 516 between the radiator temperature 512 and the bypass fluid temperature 514 and the pump fluid temperature (T pump in ) 520. The sensitivity block 518 determines a sensitivity 522 that corresponds a change in valve position of a three-way valve to a change in fluid temperature of a fluid, such as the fluid temperature at the inlet to a fuel cell stack. For example, the sensitivity 522 indicates the amount that a change in valve position (Z) results in a 1° C. change in the fluid temperature at the inlet to the fuel cell stack. The sensitivity 522 may be calculated using the partial differential I term as described above, and in particular may be calculated based on Equations 1-3 above. Implementing this sensitivity 522 may allow upper and lower limits to be increased or decreased in proportion to the system response, thereby helping to prevent windup of the I term. The control logic 600 associated with the sensitivity block 518 is shown in FIG. 6.

[0093] The three-way valve controller 500 may further include a multiplication block 524. The multiplication block 524 may apply a sensitivity 522 to the temperature difference 508. For example, the multiplication block 524 may multiply the temperature difference 508 by the sensitivity 522. The result of the multiplication block 524 is an error signal 526, which may indicate an error in the position of the three-way valve (e.g., measured in a value corresponding to a fluid split ratio).

[0094] The three-way valve controller 500 may further include a proportional-integral-derivative (PID) controller 528. The PID controller 528 may receive the error signal 526 and generate a feedback control signal 530 by considering a current error value, a past error value, and potential future errors of the error signal 526. In some implementations, the PID controller 528 is configured to apply the steps of the method 400 to prevent I-term windup by limiting the total allowed contribution of state errors. The PID controller 528 applies equations 4-7 above to the error signal 526 to generate a feedback control signal (ΔZ FB) 530 may be generated. Control logic 700 associated with the PID controller 528 is shown in FIG.

[0095] The ECU 102 may further include a combination block 532 that receives the feedback control signal 530 and a feedforward control signal 534. The feedforward control signal 534 may correspond to a feedforward control of the three-way valve as determined or calculated by a feedforward control, such as the feedforward control 312 of FIG.

[0096] The combination block 532 may generate a sum of the feedback control signal 530 and the feedforward control signal 534. The combination block 532 may output a combined control signal 536 that corresponds to a final desired valve position of the three-way valve 500 based on the feedforward control and the feedback control. The ECU 102 may control the three-way valve based on the final desired valve position.

[0097] Referring to Figure 6, control logic 600 for sensitivity block 518 of Figure 5 is shown. In this example, an equation is shown that represents the correction for the flow resistance (Z) of the bypass path. The flow resistance (Z) is then used to calculate the flow resistance of the valve. From there, the valve resistance is converted to an equivalent valve position. Other relevant inputs 602, 604, 606, 614, 616, 618, outputs 617, 624, and comparison blocks 610, 612 are also shown in control logic 600.

[0098] Referring to Figure 7, control logic 700 for PID controller 528 of Figure 5 is shown. The control logic 700 includes as input 702 the partial derivative feedback term generated by control logic 600. The control logic also includes input 704 representing the Δ control state tolerance term of equations 5 and 6 above, as well as inputs 706, 708, 713, 714, 724, 726, 728, a comparison block 710, a multiplication block 712, and a calculation block 711. In some implementations, calculation block 720 represents partial derivative based I term windup prevention, and calculation block 730 represents PI term maximum and minimum limits based on the partial derivative terms.

[0099] 8 and 9, there is shown control logic 800 associated with feedback inhibit, hold, and reset functions, and control logic 900 associated with passing feedforward values. In some embodiments, control logic 800 determines the feedforward block 312 of FIG. 3, and control logic 900 determines the feedback block 316.

[0100] The above outlines features of some embodiments to allow those skilled in the art to better understand aspects of the present disclosure. Such features can be replaced by any of a number of equivalent alternatives, only a few of which are disclosed herein. Those skilled in the art will appreciate that the present disclosure can be readily used as a basis for designing or modifying other processes and structures to achieve the same purpose and / or achieve the same advantages as the embodiments introduced herein. Those skilled in the art will also appreciate that such equivalent structures do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations can be made to the present disclosure without departing from the spirit and scope of the present disclosure.

[0101] The Abstract at the end of the disclosure is provided to comply with 37 C.FR § 1.72(b) to allow the reader to quickly ascertain the nature of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0102] Moreover, Applicant expressly intends not to apply 35 U.S.C. 112(f) to any limitations in the claims herein unless the claim expressly uses the word "means" with its associated function.

Claims

1. 1. A system for heating or cooling a fuel cell stack in a vehicle, comprising: a fuel cell stack having a plurality of fuel cells; an actuator having an actuator position and configured to control fluid flow to increase or decrease a fluid temperature of a fluid in the plurality of fuel cells; an electronic control unit (ECU) connected to the actuator, the ECU including a proportional-integral-derivative (PID) controller, wherein the ECU: determining a temperature control signal corresponding to a target temperature of the fluid; performing feedforward control of the actuator using a feedforward control signal, the feedforward control signal configured to cause the actuator to control the flow of the fluid to increase or decrease the fluid temperature of the fluid toward the target temperature of the fluid; receiving a feedback control signal from the PID controller, the feedback control signal being based on an error signal corresponding to an additional change in the actuator position to control the flow of the fluid to increase or decrease the fluid temperature of the fluid to reduce a temperature differential, the feedback control signal applying an I-term saturation limit calculated using partial derivative terms; The system is configured to control the actuator based on a combination of the feedforward control signal and the feedback control signal.

2. The system of claim 1 , wherein the PID controller is configured to generate the feedback control signal by taking into account a current error value, a past error value, and a potential future error of the error signal.

3. The system of claim 1 , wherein the actuator is a three-way valve.

4. The system of claim 1 , wherein the target temperature of the fluid and the fluid temperature of the fluid correspond to the fluid at an inlet of the fuel cell stack.

5. 1. A method for heating or cooling a fuel cell stack in a vehicle, comprising: providing a fuel cell stack having a plurality of fuel cells; providing an actuator having an actuator position and configured to control fluid flow to increase or decrease a fluid temperature of a fluid in the plurality of fuel cells; providing an electronic control unit (ECU) connected to the actuator, the ECU including a proportional-integral-derivative (PID) controller; determining, by the ECU, a temperature control signal corresponding to a target temperature of the fluid; performing feedforward control of the actuator using a feedforward control signal by the ECU, the feedforward control signal being configured to cause the actuator to control the flow of the fluid to increase or decrease the fluid temperature of the fluid towards the target temperature of the fluid; receiving, by the ECU, a feedback control signal from the PID controller, the feedback control signal controlling the flow of the fluid based on an error signal corresponding to an additional change in the actuator position to increase or decrease the fluid temperature of the fluid to reduce a temperature difference, the feedback control signal applying an I-term saturation limit calculated using partial derivative terms; controlling the actuator based on a combination of the feedforward control signal and the feedback control signal.

6. 6. The method of claim 5, further comprising generating, by the PID controller, the feedback control signal taking into account a current error value, a past error value, and a potential future error of the error signal.

7. The method of claim 5 , wherein the actuator is a three-way valve.

8. The method of claim 5 , wherein the target temperature of the fluid and the fluid temperature of the fluid correspond to the fluid at an inlet of the fuel cell stack.

9. 1. A system for heating or cooling a fuel cell circuit of a vehicle, comprising: a fuel cell stack having a plurality of fuel cells and configured to receive and heat a fluid; an actuator having an actuator position and configured to control a flow of a fluid to increase or decrease a fluid temperature of the fluid; an electronic control unit (ECU) connected to the actuator, wherein the ECU: determining a temperature control signal corresponding to a target temperature of the fluid; performing feedforward control of the actuator using a feedforward control signal, the feedforward control signal configured to cause the actuator to control the flow of the fluid to increase or decrease the fluid temperature of the fluid toward the target temperature of the fluid; determining a temperature difference between the fluid temperature of the fluid and the target temperature of the fluid; determining a sensitivity of a change in parameter value or actuator position to a change in fluid temperature of the fluid; applying the sensitivity to the temperature differential to determine an error signal corresponding to an additional change in the actuator position to control the flow of the fluid and increase or decrease the fluid temperature of the fluid to reduce the temperature differential; receiving a feedback control signal from a proportional-integral-derivative (PID) controller, the feedback control signal being based on the error signal, the feedback control signal applying an I-term saturation limit calculated using partial derivative terms; The system is configured to control the actuator based on the error signal.

10. The system of claim 9 wherein the PID controller is part of the ECU.

11. 10. The system of claim 9, wherein the PID controller is configured to generate the feedback control signal by taking into account a current error value, a past error value, and a potential future error of the error signal.

12. The system of claim 9 , wherein the actuator is a three-way valve.

13. The system of claim 9 , wherein the target temperature of the fluid and the fluid temperature of the fluid correspond to the fluid at an inlet of the fuel cell stack.

14. The system of claim 9 , wherein the ECU is further configured to control the actuator based on a combination of the feedforward control signal and the feedback control signal.

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