Performing an RBD Analysis

We recommend going through Getting Started with Relyence RBD as a starting point for learning Relyence RBD. From there, you can proceed to building your own RBDs. The following process is intended to be a starting point; you can adapt it as required for your needs.

1. Define the system you want to evaluate

Begin by determining the overall system you want to model. For example, in our Quadcopter Drone sample Analysis, there are two parts to the system: the actual drone and the hand-held controller. For this case, we choose to model just to drone itself as this is most important to us. We could model both parts if we wanted. You can also choose to use RBDs to analyze a particular portion of your system that you deem most critical. In this case, perhaps there is a part of your overall system that fails more often or cannot easily be repaired upon failure. You can use RBD to evaluate how adding redundancy to your system will affect your system reliability.

You can decide to make your RBD analyses as high-level or as granular as needed to meet your particular requirements.

2. Build your reliability block diagram

You begin your RBD by developing a diagrammatic representation of your system. Start by adding in the components of your system and how they are connected together in order to create a successful operational path. Your diagram can include nested subdiagrams that build up to an overall picture of the entire system you are analyzing.

3. Define the failure and repair characteristics of your blocks

Once your diagram is created, you then need to define the failure and repair characteristics of each component. There are various ways you can model the failures and repairs of your blocks, including linking to known failure data gathered from reliability prediction analysis, test data, or failure data from your fielded units. You can also model the components using various types of mathematical distributions, such as exponential or lognormal distributions.

4. Calculate your RBD

Once you have your RBD built and failure and repair characteristics defined, you perform computations to calculate system reliability and availability metrics. The techniques utilized vary in complexity, accuracy, and computational time. To do this part of RBD by hand would be difficult and error prone, which is why using a package designed specifically to perform RBD is important. Relyence RBD has a powerful calculation engine which enables you to quickly and accurately perform RBD calculations.

5. Analyze the results

Once you have the results of your RBD, you then review your overall system reliability, as well as individual component reliability profiles. Depending upon your requirements, you will have to assess if design changes are required. Typically, your goal with an RBD analysis is to assess your reliability and find ways to improve your system as required. 

As you make changes, you can then go back and adjust your RBD accordingly, and recalculate results based on your modifications. RBD allows you to assess design trade-off options without the need to build and test an actual design. RBDs can be part of all phases of your product lifecycle, from early design stage to manufacture, to fielded units, to next generation redesign.