Abstract: A control strategy for bleeding an anode side of fuel cell stack in a fuel cell system that improves water management and addresses durability and performance concerns. The method includes determining when to begin the anode bleed, typically by estimating or measuring the amount of nitrogen in the anode side of the stack. The method also includes determining when to end the anode bleed based on the volume of gas that has been bled. The method determines the mole flow rate of the anode gas flowing through a bleed valve, integrates the mole flow rate to get the number of moles of the gas that have passed through the bleed valve, determines a desired amount of moles to be bled, and ends the bleed when the actual number of moles of the gas equals the desired number of moles of the gas.

Abstract: A system for bleeding the anode side of first and second split fuel cell stacks in a fuel cell system that employs anode flow-shifting, where each split stack includes a bleed valve. The system determines that one or both of the bleed valves is stuck in an open position if there is flow through an orifice and a bleed has not been commanded. A shut-off valve is then used to provide the bleed if the cathode exhaust gas is able to dilute the hydrogen in the bled anode exhaust gas. An outlet valve between the first and second split stacks is used to bleed the anode exhaust gas if the cathode exhaust gas is not significant enough to dilute the hydrogen in the anode exhaust gas. If the first or second bleed valve is stuck in the closed position, then the outlet valve is used to provide the bleed.

Abstract: A method for triggering an anode bleed from split fuel cell stacks in a fuel cell system that employs anode flow-shifting. The method requests the bleed if any one of three different conditions are met. Those conditions include that the concentration of nitrogen in the anode side of the split stacks is above a predetermined percentage, the voltage spread between the maximum cell voltage and the minimum cell voltage of two fuel cells in the split stacks is greater than a predetermined spread voltage and the absolute value of the difference between the overall voltage of the two split stacks is greater than a predetermined voltage. The concentration of nitrogen in the anode can be determined in any suitable manner, such as by a nitrogen cross-over model or a sensor.

Abstract: A fuel cell system that controls an anode exhaust gas bleed during power up-transients. The fuel cell system includes a by-pass valve that allows compressor air to by-pass the fuel cell stack and be directly emitted into the cathode exhaust gas stream. The system detects a power up-transient by monitoring the rate of closing of the by-pass valve and the rate of change of an increase in the compressor airflow set-point. If these parameters pass a certain threshold, then the system determines that a power up-transient is occurring, and prevents an anode exhaust gas bleed for a predetermined period of time. If cathode pulsing is occurring where power up-transients come one after another, then the system will continuously reset the time period for preventing the anode exhaust gas bleed until a second time limit is reached, where the bleed is then forced.

Abstract: A system and method for determining when to provide an anode exhaust gas bleed from a fuel cell stack as the fuel cell stack ages. The method determines the amount of nitrogen flowing from a cathode side to an anode side of the fuel cell stack. The method also determines the amount of nitrogen flowing from the anode side to the cathode side by determining a standard deviation of voltage outputs of the fuel cells, and using the standard deviation as a model for determining the leak rate of nitrogen from the anode side to the cathode side. The method determines the concentration of nitrogen in the anode side based on the nitrogen flow between the cathode and anode side, and opens a bleed valve to bleed the anode exhaust gas if the concentration of nitrogen in the anode side goes above a predetermined value.

Abstract: A system for bleeding the anode side of first and second split fuel cell stacks in a fuel cell system that employs anode flow-shifting, where each split stack includes a bleed valve. The system determines that one or both of the bleed valves is stuck in an open position if there is flow through an orifice and a bleed has not been commanded. A shut-off valve is then used to provide the bleed if the cathode exhaust gas is able to dilute the hydrogen in the bled anode exhaust gas. An outlet valve between the first and second split stacks is used to bleed the anode exhaust gas if the cathode exhaust gas is not significant enough to dilute the hydrogen in the anode exhaust gas. If the first or second bleed valve is stuck in the closed position, then the outlet valve is used to provide the bleed.

Abstract: A method for triggering an anode bleed from split fuel cell stacks in a fuel cell system that employs anode flow-shifting. The method requests the bleed if any one of three different conditions are met. Those conditions include that the concentration of nitrogen in the anode side of the split stacks is above a predetermined percentage, the voltage spread between the maximum cell voltage and the minimum cell voltage of two fuel cells in the split stacks is greater than a predetermined spread voltage and the absolute value of the difference between the overall voltage of the two split stacks is greater than a predetermined voltage. The concentration of nitrogen in the anode can be determined in any suitable manner, such as by a nitrogen cross-over model or a sensor.

Abstract: A control strategy for bleeding an anode side of fuel cell stack in a fuel cell system that improves water management and addresses durability and performance concerns. The method includes determining when to begin the anode bleed, typically by estimating or measuring the amount of nitrogen in the anode side of the stack. The method also includes determining when to end the anode bleed based on the volume of gas that has been bled. The method determines the mole flow rate of the anode gas flowing through a bleed valve, integrates the mole flow rate to get the number of moles of the gas that have passed through the bleed valve, determines a desired amount of moles to be bled, and ends the bleed when the actual number of moles of the gas equals the desired number of moles of the gas.

Abstract: A fuel cell system that controls an anode exhaust gas bleed during power up-transients. The fuel cell system includes a by-pass valve that allows compressor air to by-pass the fuel cell stack and be directly emitted into the cathode exhaust gas stream. The system detects a power up-transient by monitoring the rate of closing of the by-pass valve and the rate of change of an increase in the compressor airflow set-point. If these parameters pass a certain threshold, then the system determines that a power up-transient is occurring, and prevents an anode exhaust gas bleed for a predetermined period of time. If cathode pulsing is occurring where power up-transients come one after another, then the system will continuously reset the time period for preventing the anode exhaust gas bleed until a second time limit is reached, where the bleed is then forced.

Abstract: A diagnostic method of detecting component failures in a fuel cell anode subsystem involves estimating fuel flow through injectors and comparing the estimated flow with a model based upon the system parameters. An observer based model is used to determine a residual value, the difference between the hydrogen input and the hydrogen consumed, and the residual is compared with a threshold range. In alternative embodiments, the stack current and the state of the valves are used to calculate the required hydrogen flow through the injectors and the duty cycle of an injector is compared to a tolerance range.

Abstract: A system and method for determining when to provide an anode exhaust gas bleed from a fuel cell stack as the fuel cell stack ages. The method determines the amount of nitrogen flowing from a cathode side to an anode side of the fuel cell stack. The method also determines the amount of nitrogen flowing from the anode side to the cathode side by determining a standard deviation of voltage outputs of the fuel cells, and using the standard deviation as a model for determining the leak rate of nitrogen from the anode side to the cathode side. The method determines the concentration of nitrogen in the anode side based on the nitrogen flow between the cathode and anode side, and opens a bleed valve to bleed the anode exhaust gas if the concentration of nitrogen in the anode side goes above a predetermined value.

Abstract: A surgical instrument for creation of tissue dissection and creation of space is disclosed. The instrument may be used any place in the body where a physician could or would use finger or instrument dissection to create a tissue pocket or space. The pocket dissector can be used under direct vision, laparoscopically, endoscopically, under fluoroscopic guidance or blindly.

Abstract: A procedure for synthesizing a state-feedback gain matrix for a vehicle suspension system including active suspension components such as continuously variable semi-active dampers is disclosed. Sensors and/or estimation schemes provide feedback to the controller concerning the vehicle states. A set of frequency-weighted metrics are first quantified and used as part of a full car 7 degree of freedom vehicle model to construct a constrained multi-objective optimization problem. Using commercially available software, a mixed H2/H? problem is iteratively solved to minimize a set of body control objectives subject to a set of physical control and wheel control related constraints to obtain data, preferably in the form of a plot of the trade-off curve between optimum wheel control and optimum body control. An initial design point is selected from the trade-off curve to calculate a state-feedback gain matrix that provides a reasonable balance between body and wheel control objectives.

Abstract: A system and method of controlling engine vibration mounted within a vehicle including at least one hydraulic mount, each mount including a fluid chamber. A pair of accelerometers sense relative acceleration across the mount between the engine and the frame and generate a relative acceleration signal. A control unit is electrically connected to the accelerometers. The control unit is adapted to generate an electronic control signal in response to the relative acceleration signal. The control device is responsive to the electric control signal for controlling the damping force of the hydraulic mount. A control algorithm calibrates the control unit such that maximum vibration damping occurs at and around the engine resonance bounce frequency.

Abstract: A system and method for unified vehicle dynamics control is described. A method for determining vehicle dynamics data, determining a vehicle dynamics reference model having at least one reference model parameter, and providing the reference model parameter to a closed-loop sliding mode control system is provided. A sliding mode control system substantially maintains the state of reference model parameters based on the vehicle dynamics reference model and the vehicle dynamics data. A method and system is directed to a computer readable medium containing a computer program comprising computer readable code for determining vehicle dynamics data, determining a vehicle dynamics reference model having at least one reference model parameter, and providing the reference model parameter to a closed-loop sliding mode control system.