Proton exchange membrane fuel cells (PEMFCs) generate electricity from an electrochemical reaction between hydrogen and oxygen. Such PEMFCs provide high power density, reduced weight and volume, and rapid start-up, while having enhanced durability, as compared with other types of fuel cells. Thus, PEMFCs are promising sources of electrical energy for a variety of applications, such as automotive applications, stationary power source applications, such as back-up power source applications, and portable power source applications. As a result, such fuel cells have the ability to reduce the dependence on other energy sources, including the dependence on oil and other fossil fuels.
One key obstacle in the adoption of PEMFCs, and the use of hydrogen as a fuel source, is the cost of manufacturing the PEMFCs themselves. Current-generation PEMFC fuel cells are formed as a stack of a plurality of layered components, which are assembled manually, through a time-consuming, complex and repetitive manufacturing process. As a result of the tedious manual manufacturing process, the occurrence of defects in the completed fuel cells due to human errors is common. In addition, due to the time-consuming nature of the manufacturing process, it is common to take as long as a full day to assemble and leak-test a single PEMFC hydrogen fuel cell stack. However, in order to be commercially viable, fuel cell stacks must be assembled with minimal defects in a time efficient manner.
To overcome the drawbacks associated with the manual assembly of PEMFC fuel cells, automated assembly techniques utilizing robotic systems have been developed. Unfortunately, current automated manufacturing systems have had limited success, due to the difficulty in accurately and precisely aligning each adjacent component layer in the fuel cell stack. For example, such components forming a layer in the fuel cell stack includes thin, flexible membrane electrode assemblies (MEAs), rubber gaskets, graphite paper, graphite bipolar plates, copper current collector plates and top/bottom end-plates. Thus, because these components must be precisely aligned during manufacturing to produce a functional fuel cell and to eliminate overbroad reactant leaks, an automated system for carrying out the manufacture of the PEMFC fuel cell is desirable.
Additional obstacles in achieving precision automated assembly of PEMFC fuel cell stacks relate to the robotic assembly systems themselves. That is, current robotic assembly systems are limited due to their lack of compliance; their lack of flexibility of the joints of the robotic arm; and the inability of the robotic arm to accurately repeat movements, which reduces the ability of the robotic arm to tolerate and compensate for misaligned fuel cell components during the assembly of a completed fuel cell.
Another barrier to the successful operation of automated manufacturing lines of fuel cells is the insufficient integration of the design of the fuel cell components with the design of the automated assembly line, including the end-effector used by the robotic arm, which also contributes to the lack of accuracy and precision during the alignment of the fuel cell components.
Therefore, there is a need for a robotic fuel cell assembly system that includes an end-effector for a robotic arm and fuel cell components that include integrated design features that allow for accurate and precise alignment between adjacent components in a fuel cell stack during automated pick-up and release operations. In addition, there is a need for a robotic fuel cell assembly system that includes an end-effector for a robotic arm that is configured to compensate for the limited accuracy, repeatability and lack of compliance of the robotic arm used to move and the end-effector during the manufacture of a fuel cell.