Abstract: A system for detecting the absolute rotational angle of a shaft rotatable more than one revolution includes a drive wheel connected to the shaft to rotate therewith. The drive wheel includes measurement sectors adjacent to one another in a circumferential direction. First and second driven wheels are engaged to the drive wheel. First and second sensors monitor rotational positions of the driven wheels to thereby detect an absolute rotational angle of the shaft. A third sensor monitors a relative angular position of the shaft in relation to a detected one of the measurement sectors to thereby detect the relative angular position of the shaft within one revolution of the shaft. The detected absolute rotational angle of the shaft is refined with the detected relative angular position of the shaft to thereby generate the absolute rotational angle of the shaft with more precision.

Abstract: A valve for a pressure vessel system includes a housing having a cavity defined by an inner surface of the housing. The housing further includes a rod aperture and a pair of fluid flow ports. An actuator is disposed adjacent the housing. The valve also includes a piston having a rod coupled to a piston head. The piston head is disposed in the cavity of the housing, and the rod disposed through the rod aperture. The rod is also coupled to the actuator. A ring seal is disposed between the piston head and an inner surface of the housing. The ring seal biases the piston head toward one of the fluid flow ports and seals the one of the fluid flow ports to close the valve when the actuator is deactivated. The ring seal is elastically deformed and the fluid flow ports are opened when the actuator is activated.

Abstract: A valve for a pressure vessel system includes a housing including a cavity and a hollow fluid flow portion. A membrane actuator is disposed in the cavity of the housing. A piston is disposed in the cavity and in the hollow fluid flow portion of the housing. A spring is disposed in the hollow fluid flow portion of the housing. The spring biases a piston head toward a fluid flow port formed in the hollow fluid flow portion. The piston head seals the fluid flow port when the biasing of the piston head by the spring is not countered by an opposite deflection of the membrane actuator.

Abstract: A method for operating a cooling system for a fuel cell stack in a vehicle is provided. The method includes the steps of: determining a fan request for a variable speed fan disposed in the cooling system; employing a noise-comfort function to select a fan comfort request; and adjusting a speed of the variable speed fan in response to the fan request; wherein a noise emission by the variable speed fan is militated against. A cooling system for a fuel cell stack in a vehicle that employs the noise-comfort function is also provided.

Abstract: A fuel cell system that does not include a high voltage battery in combination with a fuel cell stack. The fuel cell stack and a bi-directional power module are electrically coupled to a high voltage bus. A first larger capacity 12 volt battery is electrically coupled to the power module opposite to the high voltage bus and a second smaller capacity 12 volt battery is electrically coupled to the first 12 volt battery, where a diode is electrically coupled between the first and second 12 volt batteries and only allows current flow from the first 12 volt battery to the second 12 volt battery. 12 volt battery loads are electrically coupled to the second 12 volt battery.

Abstract: A system and method for determining whether a shut-off valve in a cabin heating by-pass line of a thermal sub-system associated with an engine has failed that uses the pump current for a pump that pumps the cooling fluid through the by-pass line. The method includes setting a predetermined constant speed of the pump and then providing a valve command that opens the by-pass valve. The method then determines if the pump current has increased or remained substantially the same when the by-pass valve is commanded open, and determines that the by-pass valve has not opened if the pump current remains substantially constant when the by-pass valve is commanded open.

Abstract: A system for controlling the power output of a fuel cell stack and a battery in a hybrid fuel cell system. The system includes a power damping filter that receives a power request signal, and damps the request to reduce large changes in the power request. A battery state of charge controller receives the difference between a battery state of charge set-point and the actual battery state of charge, and provides a battery power signal that attempts to maintain the battery state of charge at the set-point. The damped power signal and the battery power signal are added to generate a system power demand signal that satisfies the driver power request using the battery power and fuel cell stack power, and uses the fuel cell stack power to charge the battery during low power transients or if the battery state of charge is below the set-point.

Abstract: A method for operating a cooling system for a fuel cell stack in a vehicle is provided. The method includes the steps of: determining a fan request for a variable speed fan disposed in the cooling system; employing a noise-comfort function to select a fan comfort request; and adjusting a speed of the variable speed fan in response to the fan request; wherein a noise emission by the variable speed fan is militated against. A cooling system for a fuel cell stack in a vehicle that employs the noise-comfort function is also provided.

Abstract: A hybrid fuel cell system that includes a fuel cell stack and a high voltage battery. The fuel cell system also includes a cell voltage controller that controls the average cell voltage of the cells in the fuel cell stack, a damped driver request module that damps a driver power request signal, and a power balancing module. The power balancing module maintains the cell voltage of the cells in the stack within a predetermined range, and uses excess power from the stack beyond what is requested to charge the battery. The power balancing module includes a base load limiter that prevents the cell voltage from going above a predetermined value, unless the battery is at is maximum state of charge.

Abstract: A system and method for reducing RH cycling of the membranes in a fuel cell stack. A control algorithm damps a power request signal using a first order filter during low power transients so that the fuel cell stack continues generating power at a higher rate than is requested. The excess power generated by the stack is used to recharge a battery in the fuel cell system. The damped power signal is weighted so that more fuel cell stack power is provided for a low battery state of charge unless stack power is provided for a high battery state of charge.

Abstract: A technique for controlling the relative humidity of a cathode airflow to a fuel cell stack that includes compensating for valve non-linearities. The cathode input air flows through a water vapor transfer unit where it is humidified. The humidified cathode exhaust from the fuel cell stack is output to the water vapor transfer unit to provide the water vapor for humidifying the cathode input airflow. A first control valve controls the flow of the cathode exhaust through the water vapor transfer unit and a second control valve controls the flow of the cathode exhaust that by-passes the water vapor transfer unit to control both the relative humidity of the cathode input airflow and the pressure within the stack. By compensating for the non-linearity, the first and second valves control the relative humidity of the cathode airflow without changing the cathode output resistance.

Abstract: A hybrid fuel cell system that includes a fuel cell stack and a high voltage battery. The fuel cell system also includes a cell voltage controller that controls the average cell voltage of the cells in the fuel cell stack, a damped driver request module that damps a driver power request signal, and a power balancing module. The power balancing module maintains the cell voltage of the cells in the stack within a predetermined range, and uses excess power from the stack beyond what is requested to charge the battery. The power balancing module includes a base load limiter that prevents the cell voltage from going above a predetermined value, unless the battery is at is maximum state of charge.

Abstract: A method for operating a cooling system for a fuel cell stack in a vehicle is provided. The method includes the steps of: determining a fan request for a variable speed fan disposed in the cooling system; employing a noise-comfort function to select a fan comfort request; and adjusting a speed of the variable speed fan in response to the fan request; wherein a noise emission by the variable speed fan is militated against. A cooling system for a fuel cell stack in a vehicle that employs the noise-comfort function is also provided.

Abstract: An angle sensor includes two measuring pinions which rotate in the same direction in response to a drive pinion rotating. The measuring pinions have different absolute angular positions after rotating. The absolute angular position of the drive pinion is determinable from the absolute angular positions of the measuring pinions. A delta wheel between the measuring pinions has two coaxially arranged rings. One ring engages the second measuring pinion and the other ring engages the first measuring pinion such that the rings rotate relative to one another in the same direction in response to the measuring pinions rotating in the opposite direction. A spring connecting the rings together biases the rings to move in opposite directions toward one another after the rings have been rotated relative to one another in the same direction such that the rings respectively press the measuring pinions against the drive pinion.

Abstract: A sensor determines the absolute angular position of a body that can rotate through rotations. The sensor includes two code wheels which rotate as the body rotates. The code wheels are driven at a different gear ratio such that the code wheels rotate faster than the body and the code wheels rotate at different rates. Two sensor elements respectively determine the rotational angle positions of the code wheels. The difference between the rotational angle positions is a beat angle. The different gear ratio is selected such that beat angle periods are in an angular measuring range of the sensor and the absolute angular positions of the code wheels in the beat angle periods is different. The absolute angular positions of the code wheels in successive beat angle periods is offset by the nth part of the measuring range of a sensor element, where n is number of beat angle periods.

Abstract: A system for controlling the power output of a fuel cell stack and a battery in a hybrid fuel cell system. The system includes a power damping filter that receives a power request signal, and damps the request to reduce large changes in the power request. A battery state of charge controller receives the difference between a battery state of charge set-point and the actual battery state of charge, and provides a battery power signal that attempts to maintain the battery state of charge at the set-point. The damped power signal and the battery power signal are added to generate a system power demand signal that satisfies the driver power request using the battery power and fuel cell stack power, and uses the fuel cell stack power to charge the battery during low power transients or if the battery state of charge is below the set-point.

Abstract: A control algorithm for a by-pass valve in a thermal sub-system of a fuel cell system, where the by-pass valve includes a wax element that is heated by a heating element. A stack power loss is applied to a PDT1 controller that associates a PDT dynamic function to the loss. The difference between the desired temperature of the stack and the actual temperature of the stack is applied to a PI controller that provides an error value of the difference. The actual temperature of the stack is applied to a look-up table that provides a value based on how close the actual temperature is to the opening temperature of the wax element. The values from the PDT1 controller, the PI controller and the look-up table are added to provide an output signal to control the current applied to the heater element, and thus, the heat applied to the wax element.

Abstract: A system for controlling the power output of a fuel cell stack and a battery in a hybrid fuel cell system. The system includes a power damping filter that receives a power request signal, and damps the request to reduce large changes in the power request. A battery state of charge controller receives the difference between a battery state of charge set-point and the actual battery state of charge, and provides a battery power signal that attempts to maintain the battery state of charge at the set-point. The damped power signal and the battery power signal are added to generate a system power demand signal that satisfies the driver power request using the battery power and fuel cell stack power, and uses the fuel cell stack power to charge the battery during low power transients or if the battery state of charge is below the set-point.

Abstract: An angle sensor includes two measuring pinions which rotate in the same direction in response to a drive pinion rotating. The measuring pinions have different absolute angular positions after rotating. The absolute angular position of the drive pinion is determinable from the absolute angular positions of the measuring pinions. A delta wheel between the measuring pinions has two coaxially arranged rings. One ring engages the second measuring pinion and the other ring engages the first measuring pinion such that the rings rotate relative to one another in the same direction in response to the measuring pinions rotating in the opposite direction. A spring connecting the rings together biases the rings to move in opposite directions toward one another after the rings have been rotated relative to one another in the same direction such that the rings respectively press the measuring pinions against the drive pinion.

Abstract: A method of determining a temperature of a coolant in a coolant circulation system is disclosed. The coolant circulation system includes a coolant flow valve having a valve housing and an expansion element provided in the valve housing for controlling flow of the coolant through the valve housing. According to the method, an ohmic resistance of the expansion element is measured. The temperature of the coolant is determined by correlating the ohmic resistance of the expansion element with the temperature of the coolant.