A survey on reducing reconfiguration cost: reconfigurable PID control as a special case ?

Reconfigurable computing is a paradigm in computing architecture that refers to the practice of using interchangeable hardware modules to enhance the performance of conventional Von-Neumann style computing. Despite the numerous advantages of reconfiguration, it is only suitable for quasi-static applications with slowly changing reconfiguration criteria. In general, it is only advantageous to reconfigure if the execution time exceeds reconfiguration time. Since the execution time of real-time systems are quite limited, the control of dynamic non-linear systems are typically not reconfigured. Instead, adaptivity is mostly gained from reading coefficients or gains from memory. Where different controller architectures are required, the route of parallel implementation could be taken, switching between architectures. The drawback of this approach is an increase in area required to implement the controllers. Reconfiguration on the other hand could allow the different control architectures to be swapped on the fly without interrupting operation of the controller, while minimizing the area required. Unfortunately, this process is limited by the overhead introduced by the reconfiguration. Even though various survey papers exist on the topic of reconfiguration, none really focus on methods to reduce the cost of reconfiguration. This survey summarizes different means of reducing configuration overhead in an attempt to allow reconfiguration of applications with limited execution time. A block RAMbased (BRAM) architecture is proposed as the optimal architecture for reconfiguring dynamic applications. As an example, this architecture is used to discuss the methodology used to design a reconfigurable PID controller.