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一个很棒的网络控制系统仿真软件

----------------------------------------------
 TrueTime version 1.13
 Example: Simple PID Task Simulation
 Directory: $DIR/examples/simple_pid
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1. INTRODUCTION

These examples are intended to give a basic introduction to the
TrueTime simulation environment. The examples consider simple PID
control of a DC-servo process. The process is controlled by a
controller task implemented in a TrueTime kernel block. Two versions
of the code function are provided, one standard PID implementation and
one that calls a Simulink block diagram to calculate the control
signal in each sample. The example is also extended to the case of
three PID-tasks running concurrently on the same CPU controlling three
different servo systems.


2. COMPILING THE SIMULATION FILES

Before starting Matlab, you must set the environment variable TTKERNEL
to point to the directory with the TrueTime kernel files:

    Unix/Linux: > export TTKERNEL=$DIR/kernel
    Windows:  Control Panel / System / Advanced / Environment Variables

After starting Matlab, you must also add the directories $DIR/kernel and
$DIR/kernel/matlab to your Matlab path. You could for instance do this in
your startup script as follows:

    addpath(getenv('TTKERNEL'))
    addpath([getenv('TTKERNEL') '/matlab'])

As described in the reference manual it is possible to write a
TrueTime simulation (i.e. the code functions for the tasks and the
initialization commands) either as m-files or as C++ functions. Both
approaches are provided for this example and the compilations needed
for the respective alternatives are described below.

2.1 Matlab version
   
    The files for Matlab-simulation of the example are located in the
    directory $DIR/examples/simple_pid/matlab. All necessary
    compilation is performed by the m-file makepid.m. Run this file
    from the Matlab command prompt:

    >> makepid
   
    NOTE: The makepid-file only needs to be run once. No
    re-compilation is needed after changing code functions or
    initialization commands.

2.2 C++ version
    
    The files for C++-simulation of the example are located in the
    directory $DIR/examples/distributed/c++. Compilation of the
    various init scripts is performed by the m-file makepid.m. Run
    this file from the Matlab command prompt:

    >> makepid

    NOTE: If changes are made to the code functions or the
    initialization commands, the corresponding init-file needs to be
    re-compiled.


3. EXPERIMENTS

3.1 Single PID task

    Open the model servo.mdl to run the single PID task simulation. 

    - Run a simulation and verify that the controller behaves as
      expected. Notice the computational delay in the control signal.
      Compare with the code function. Study the schedule plot.

    - Try changing the execution time of the first segment of the code
      function, to simulate the effect of different input-output delays.

    - Also try changing the sampling period and study the resulting
      control performance.

    - A PID controller is implemented in the Simulink block
      controller.mdl. Change the name of the init-file in the parameter
      field of the kernel block to block_init. Now the code function will
      use this Simulink block to compute the control signal in each sample.

3.2 Three PID tasks

    Open the model threeservos.mdl to run the three PID task simulation.

    - Make sure that rate-monotonic scheduling is specified in the
      function ttInitKernel and simulate the system. Study the computer
      schedule and the control performance. Task 1 will miss all its
      deadlines and the corresponding control loop is unstable.

    - Change the scheduling policy to earliest-deadline-first and run a
      new simulation. Again study the computer schedule and the control
      performance. After an initial transient all tasks will miss their
      deadlines, but the overall control performance, however, is
      satisfactory.