**5.1 Executable specifications**

As designs become larger and more complicated, it becomes necessary to first describe them at a high level of abstraction. For example, Simulink (The MathWork web site) can provide specific block-sets such as signal processing, communication, video and image processing block set to help the designer to build an abstraction model. This model provides a

Potential of Grid Technology for Embedded Systems and Applications 331

behavioral requirements for the system. Once the system engineer submits the executable specification to the development team, the team may need to make modifications to it in order to fit the design into a real world that may have limited resources, such as memory or processing power. These modifications may cause the output of the new design to deviate from the original design. Design engineers should decide if the deviation is acceptable. In this section, modifications in the controlling algorithms will be done to make it suitable for hardware implementation and demonstrate how to continuously verify the design against the executable specifications. For example, if the designers need to change the controlling algorithm to meet the requirements, MBD method provides an environment where the designer can redesign the control algorithms and validate it in very short time comparing to

The modern Model Based Design tools provide automatic generation for both prototype and production codes directly from the model. So, all the design changes automatically flow through the final implementation. This process results in significant time and cost saving due to the inherent reproducibility and testability of the generated codes and elimination of communication errors (Ming-Shan, 2007 & Rautio, 2008). In the Hardware In the Loop (HIL) Testing, the designer can test the real-time behaviors and characteristics of the final system to verify the system control without the need for the physical hardware or operational environment, as shown in Figure 3. HIL Testing can save the time with significant ratio comparing to the traditional design method. As well, it is easy to implement comparing to physical prototype production. Up to this moment, the Model Based Design process does not completely eliminate the need for testing in the actual prototype, but it offers several opportunities to reduce the time needed to the testing stage (Stepner et al., 1999 &

> Hardware-in-the-loop-simulator Truth or physics model

Embedded Computer

HIL Simulator

Input Software

Input hardware (A/D, discrete, serial)

Outputs of embedded system

Input

Inputs of simulator

Mosterman, 2010 & Behboodian, 2006 & Davey and Friedman, 2007).

traditional method of design (Ming-Shan, 2007).

Fig. 3. Hardware In the Loop (HIL) Testing

Output software

Outputs of simulator

Output hardware (A/D, discrete, serial)

Inputs of embedded system

Output Software

**5.3 Implementation and testing** 

Fig. 2. Elements of Model Based Design

documented method for verifying and validating of design before move to the development in actual controllers and hardware (Woodward and Mosterman, 2007 & Manfred, 2006). System engineers usually develop this high-level description for several purposes as listed below:


A key point of shrinking the embedded life cycle by applying the MBD method is to begin developing the embedded control algorithm early in the design cycle as possible (Rautio, 2008). In this stage, the model provides the ability to begin simulation of the control behaviors while the hardware prototype is still under development. In addition, the model can be re-used for further modification of the same product which reduces the effort necessary to build the model again.
