Embedded systems will become more and more complex in the near future. In Japan, μITRON and embedded Linux are popular for building embedded systems. Since μITRON does not support memory protection, the bugs in an application may cause serious system failure. Also, embedded Linux cannot avoid an application to monopolize the entire CPU capacity due to its bugs. Therefore, we need to increase the robustness of embedded systems at the operating system level for developing future complex embedded systems. We have developed two operating systems to increase the robustness of embedded systems even if applications contain serious bugs. The first operating system supports multiple execution of μITRON. Each application is executed on a different μITRON kernel. Therefore, if an application is crashed, other applications that are in different address spaces have no effect. The second operating system enhances the resource management of embedded Linux. Our system monitors an application's CPU usage and stops the execution if the usage exceeds the specified capacity.