faq.htm

国外专家做的求解LMI鲁棒控制的工具箱,可以相对高效的解决LMI问题

        <a name="setclass"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>Is there really a <code>set</code> class?</b></td>
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        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0">No...<code>set</code> is only a wrapper to 
        call the old class <code>lmi</code>. To much work to re-write all code 
        just for a name change.</p>
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    <p style="margin-bottom: 0; margin-top:0">&nbsp;</p>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="normalset"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>Is <code>set</code> related to 
        the &quot;normal&quot; set command in MATLAB</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0">No... The name <code>set</code> 
        was selected since it is short. An alternative would be to define 
        constraints, or feasible sets, using a command named, e.g., <code>
        constraint</code>. However, my keyboard typing speed is too slow to 
        allow for such a long command name. In my opinion, the name <code>set</code> 
        is at-least better than the old name <code>lmi</code>.</p>
        </td>
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    <p style="margin-bottom: 0; margin-top:0">&nbsp;</p>
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        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="lmielement"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>I define a 
      semidefinite constraint, but YALMIP declares it &quot;element-wise&quot;.</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0">YALMIP detects semidefinite 
        constraints by checking symmetry. In some cases (working with very 
        ill-conditioned data), numerical problems may lead to a small violation 
        of symmetry in MATLAB, and YALMIP will declare the constraint as 
        element-wise. To solve this problem, just symmetrize your variable 
        first.</p>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="reallystrict"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>Are  inequalities really 
    strict?</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0">By default, strict (&lt;,&gt;) and 
        non-strict (&lt;=,&gt;=) inequalities are treated in the same way in YALMIP, 
        and the result depends on the solver. However, by using the field <code>
        shift</code> in <a href="reference.htm#sdpsettings">sdpsetttings</a>, 
        inequalities defined using &lt; and &gt; will be treated slightly different. 
        YALMIP will add a small perturbation to these inequalities to 
        increase the likelihood of a strictly feasible solution. Warning : If you 
		have an integer variable, and add a constraint <code>set(x<2)</code>, this will not be interpreted as <code>set(x<=1)</code> 
		. To avoid confusion, use <code>set(x<=1)</code>. The same holds for rank constraints <code>set(rank(x)<2)<n)</code>.</code></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="subasgn"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>Why can I not write <code>X = 
    eye(2); X(1,1)=sdpvar(1,1)</code>?</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
    <p style="margin-bottom: 0; margin-top:0">Work in progress...</p>
        </td>
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    <p style="margin-top: 0; margin-bottom: 0">&nbsp;</p>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="gevp"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>How do I solve generalized 
        eigenvalue problems (like <code>gevp</code> in <a href="solvers.htm#lmilab">LMILAB</a>)?</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
    <p style="margin-bottom: 0; margin-top:0">Two options. The first one is to code your own 
    script based on a simple bisection. This is illustrated in 
    the example <code>decayex.m</code>. An alternative is to install the BMI solver 
    <a href="solvers.htm#penbmi">PENBMI</a>. This solver solves GEVP problems 
    globally.</p>
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        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="foundbug"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>I have found a bug. What to do?</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
    <p style="margin-bottom: 0; margin-top:0">Send a mail to <a href="mailto:[e-mail]">
    [e-mail]</a>. Type <code>ver</code> in MATLAB and include 
    the result in the mail. If possible, include the code (as simple as 
    possible) that generated the fault, otherwise, include at-least the error 
    message etc. The more information the better.</p>
        </td>
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        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="feature"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>I have an idea for a new feature. 
    What to do?</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0">Send a mail to <a href="mailto:[e-mail]">
    [e-mail]</a>. However, I only add new features when I 
    need them my self, but if your idea is good enough, I might realize that I 
    need it!</td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><b><font color="#0000FF">
        <a name="yalmipmeans"></a>Q:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0"><b>What does YALMIP mean?</b></td>
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        <td width="26" valign="top">
        <p style="margin-bottom: 0; margin-top:0"><font color="#0000FF"><b>A</b></font><b><font color="#0000FF">:</font></b></td>
        <td>
        <p style="margin-bottom: 0; margin-top:0">Used to be short for Yet 
        Another LMI Parser. However, since YALMIP is much more than a LMI parser 
        now, it does not mean anything. 
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