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2.1. REQUIREMENT INTERPRETATION BLOCK
Sometimes, the requirements in a particular application may not be expressed in terms of the control design specifications. In this block, the given requirements from the application are transformed to specifications which can be treated in the control design package. Since the requirements differ from application to application, the requirement interpretation block has specified modules according to each controlled object.
For example, when the controlled object is an industry robot, the requirements in the application are standard cycle-time, positioning accuracy, and tracking accuracy. The control design specifications are crossover frequency, amount of overshoot, and settling time. Acceleration time and deceleration time are calculated, and standard cycle-time is transformed to settling time. The acceptable limit of overshoot is calculated from the positioning accuracy. Crossover frequency is decided according to the required tracking accuracy and maximum speed. The specifications are then passed on to both the analysis/design and the modeling blocks
2.2. MODELING BLOCK
In the modeling block, the model of a controlled object is obtained by an actual measurement or from the design parameters of the controlled object. In case the order of the model is too high for designing a controller, the order of the model needs to be reduced. For example, a three-mass model is approximated by a two-mass model if the resonant frequency of the second vibration mode is much higher than the crossover frequency. The reduced order model is then sent to the analysis/design block.
2.3. ANALYSIS/DESIGN BLOCK
The analysis/design block has six modules: a control structure selection module, a control parameters calculation module, a pre-design analysis module, a post design analysis module, a command signal generation module and a parameter optimizer module. The control structure selection module and the command signal generation module would apply the appropriate module for control system design. All of the modules in the analysis/design block are constructed using MATLAB/SIMULINK.
In this block, the structure and the parameters of a controller are designed according to the interpreted requirements and the system model. In a conventional CACSD system, users need to select the controller structure, such as PID. In addition, the users need to give some of the criteria, such as cost functions, to the CACSD system. The aim of developing the CSDA system is to automate these processes by analyzing the given specifications and the model. Since it is difficult to get the best controller automatically, the system requires some redesigning process. If the results are not satisfactory, the users can modify the design parameters during and/or after this process. If the specifications given by the requirement interpretation block are satisfied, the designed command signal and designed controller are sent to the verification block. If the specifications are not satisfied, redesign demand is sent to the requirement interpretation block.
2.4. DATABASE MANAGEMENT AND KNOWLEDGE BASE BLOCK
2.4.1. Database Management Module
Many control system design packages do not provide any support for database management. Control system design activities are carried out using the package or design environment such as MATLAB. It is then up to the engineer to decide how to store the design results and documents the design activity. Very often, the results are put in a data file in text format, and the file is given a meaningful file name.
Very few design packages has a built-in database management facility as an integral part of the CACSD environment. The database management module in the CSDA system is a built-in facility for the user. The purposes of the facility are:
1. To keep track and to organize the models, design specifications, controllers obtained and analysis results over the control system design life-cycle.
2. To automate the documentation of control system design activities by the engineer. This is to avoid manual organization of the large amount of data and files created during the course of the design process.