【维修案例】西门子医用加速器多叶光栅（MLC）故障维修

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                    <p><span><span><p><img src="image/20201019/db1ed5852b3eb566b89ea7a6bde1b7a5_1.jpg" /></p><br  /></span></span></p><p><span><span><br  /></span></span></p><p><span><span>我院加速器（德国西门子公司）因病人多，每天开机 时间长，且加速器使用已近</span><span> </span><span>7</span><span> </span><span>年，故整机机械、光学、剂量、</span><span> </span><span>电路等系统均开始出现老化现象。加速器故障也由表浅简</span><span> </span><span>单向复杂的元件级故障转移，维修难度逐渐增大。</span></span></p><p><span><br  /></span></p><p><strong><span><span>1</span><span> </span><span>故障现象</span></span></strong></p><p><span><br  /></span></p><p><span><span>某天下午加速器在治疗调强运行过程中，突然出现多 </span><span>叶光</span><span>栅</span><span>（MLC</span><span>）</span><span>显示叶片卡住</span><span>，</span><span>无法自动变化下一治疗子野， 且屏显有叶片变红闪烁报警，加速器无法继续工作。</span></span></p><p><span><br  /></span></p><p><strong><span><span>2</span><span> </span><span>故障检查</span></span></strong></p><p><span><br  /></span></p><p><span><span>经观察发现</span><span> </span><span>：①</span><span> </span><span>技师工作站屏显有叶片变红闪烁报警， </span><span>扭动设备复位钥匙无法复位，进入机器维修模式，软件复位，</span><span> 故障依旧</span><span> </span><span>；② </span><span>进入机房后，操控手控盒功能分别控制叶片</span><span> </span><span>组</span><span> </span><span>X1、X2</span><span> </span><span>工作，X1、X2</span><span> </span><span>叶片组除</span><span> </span><span>29#</span><span> </span><span>两叶片碰死不动外， 其他叶片均可移动，但各叶片位置不对</span><span> </span><span>；③ </span><span>分别单独操作</span><span> </span><span>X1、X2</span><span> </span><span>组的</span><span> </span><span>29#</span><span> </span><span>叶片。X2</span><span> </span><span>组的</span><span> </span><span>29#</span><span> </span><span>叶片可控能移动，但</span><span> 对</span><span> </span><span>X1</span><span> </span><span>组的</span><span> </span><span>29#</span><span> </span><span>叶片控制时不能移动</span><span> </span><span>[1-2]</span><span>。初步结论为</span><span> </span><span>MLC 基本正常，有可能是</span><span> </span><span>X1</span><span> </span><span>叶片组</span><span> </span><span>29#</span><span> </span><span>单叶片偶发过冲，过中 </span><span>线</span><span> </span><span>10</span><span> </span><span>cm</span><span> </span><span>后限位，引发了整个</span><span> </span><span>MLC</span><span> </span><span>位置紊乱，导致故障发生。</span></span></p><p><span><br  /></span></p><p><strong><span><span>3</span><span> </span><span>故障维修</span></span></strong></p><p><span><br  /></span></p><p><span><span>（1）重校 MLC</span><span> </span><span>叶片位置。现场检查没有发现加速器其</span><span>他不正常现象，只能按以往经验试着重校 </span><span>MLC</span><span> 叶片位置。</span><span> </span><span>按标准校正后，故障消失，机器恢复正常工作，当天放疗</span><span> </span><span>工作完成。但第二天下午治疗调强病人，上述故障重现。</span><span> </span><span>观察</span><span> </span><span>MLC</span><span> </span><span>叶片，X1</span><span> </span><span>叶片组</span><span> </span><span>29#</span><span> </span><span>单叶片过中线</span><span> </span><span>10</span><span> </span><span>cm</span><span> </span><span>处有</span><span> 过冲现象。按标准再校</span><span> </span><span>MLC</span><span> </span><span>叶片位置，上电试机正常。但</span><span> </span><span>随后几天此故障反复多次出现。</span></span></p><p><span><br  /></span></p><p><span><span>（2）电路分析。MLC</span><span> </span><span>电路基本工作原理</span><span> </span><span>[3-4]</span><span> </span><span>：MLC</span><span> </span><span>叶 片位置是由</span><span> </span><span>MLC</span><span> </span><span>控制机柜编程后，给出电机驱动信号驱动</span><span> 电机来确定各叶片位置的，叶片电机的转动带动了位置电</span><span> </span><span>位器和位置编码电位器的转动，2</span><span> </span><span>个电位器产生的反馈信</span><span> </span><span>号经过处理后，送到</span><span> </span><span>SENSOR</span><span> </span><span>板上比较，比较结果信号送 </span><span>回</span><span> </span><span>MLC</span><span> </span><span>控制机柜</span><span> </span><span>SLAVE1#</span><span> </span><span>板与实际设定信号比较，来判</span><span> </span><span>断该叶片位置是否正确，再调整该叶片运动到应设位置。</span><span> </span><span>故通过</span><span> </span><span>MLC</span><span> </span><span>电路图仔细分析后，得出可能性判断</span><span> </span><span>：①</span><span> </span><span>控 制</span><span> </span><span>MLC</span><span> </span><span>的</span><span> </span><span>X1</span><span> </span><span>驱动电路板故障，送出不正确控制信号</span><span> </span><span>；②</span><span> </span><span>叶片驱动</span><span> </span><span>29#</span><span> </span><span>电机自身故障或位置电位器和位置译码器有 </span><span>损坏，无法送出有效回馈比较信号</span><span> </span><span>；③</span><span> </span><span>SENSOR</span><span> </span><span>板故障，</span><span> </span><span>实际位置信号与编码位置信号对比错误，给出了错误结果</span><span> </span><span>信号</span><span> </span><span>；④</span><span> </span><span>SLAVE1#</span><span> </span><span>板故障，给出错误判断信号，返回错误 控制了电机驱动板。</span></span></p><p><span><br  /></span></p><p><span><span>（3）故障处理</span><span> </span><span>：采用分段法，以</span><span> </span><span>29#</span><span> </span><span>驱动电机为标记，</span><span>分为驱动和回馈前后两段</span><span> </span><span>；采用更换法，将</span><span> </span><span>29#</span><span> </span><span>驱动电机组与相邻</span><span> </span><span>15#</span><span> </span><span>驱动电机组整体更换，经试验故障现象依然</span><span>出现，且故障叶片位置未转移。可排除</span><span> </span><span>29#</span><span> </span><span>电机组故障。</span><span> </span><span>恢复两机组原来位置，为方便观察故障现象，不盖外壳，</span><span> </span><span>重新校正</span><span> </span><span>MLC</span><span> </span><span>位置，使用了</span><span> </span><span>2</span><span> </span><span>天，故障居然没有重现。</span></span></p><p><span><br  /></span></p><p><span><span>仔细分析维修过程</span><span> </span><span>：①</span><span> </span><span>为判断此故障，仅仅是调换了</span><span> </span><span>X1</span><span> </span><span>叶片组</span><span> </span><span>29#</span><span> </span><span>驱动电机组，没有做其他工作</span><span> </span><span>；② </span><span>便于观察</span><span> </span><span>故障，未盖加速器机头外壳，经位置查看，发现</span><span> </span><span>SENSOR</span><span> </span><span>板</span><span> </span><span>正处在机头最外层，可直接看到</span><span> </span><span>；③</span><span> </span><span>经过近</span><span> </span><span>1</span><span> </span><span>周的追踪观</span><span> </span><span>察记录，发现故障发生时间基本在下午</span><span> </span><span>16:00~19:00</span><span> </span><span>左右，</span><span> </span><span>且故障发生间隔时间越来越短，故障发生频率越来越高</span><span> </span><span>；④</span><span> </span><span>故障发生后，校正 MLC 叶片位置后，基本能正常继续使用</span><span> </span><span>；</span><span>⑤</span><span> </span><span>为验证想法，加速器机头开壳状态下，运行</span><span> </span><span>1</span><span> </span><span>周，加速</span><span>器未发生相同故障</span><span> </span><span>[5]</span><span>。通过实验表明</span><span> </span><span>：基本可判断是加速器 因长时间运行，导致机头内过热，SENSOR </span><span>板上某元器件</span><span> </span><span>热稳定性变差，X1</span><span> </span><span>叶片组</span><span> </span><span>29#</span><span> </span><span>机组的</span><span> </span><span>POTENTIOMETER</span><span> </span><span>返回信号与</span><span> </span><span>ENCODER</span><span> </span><span>返回信号在</span><span> </span><span>SENSOR</span><span> </span><span>板上比较错误，</span><span> </span><span>发出错误信息，从而造成此故障发生。</span></span></p><p><span><br  /></span></p><p><span><span>（4）故障解决</span><span> </span><span>：问题集中到</span><span> </span><span>SENSOR</span><span> </span><span>I/F#1</span><span> </span><span>板上，通</span><span> </span><span>过对</span><span> </span><span>SENSOR</span><span> </span><span>I/F#1</span><span> </span><span>电路分析，发现所有电路几乎都围绕</span><span> 着</span><span> </span><span>CPU#1、CPU#2</span><span> </span><span>芯</span><span> </span><span>片（P80C31BH）</span><span> </span><span>工</span><span> </span><span>作，</span><span> </span><span>且</span><span> </span><span>CPU#1、 CPU#2</span><span> </span><span>为活动插件芯</span><span> </span><span>片，说明这两芯片为易坏</span><span> </span><span>件。因</span><span> </span><span>CPU#1、CPU#2</span><span> </span><span>芯片之间有关联，决定采用更换法再试，</span><span> </span><span>于是网购</span><span> </span><span>2</span><span> </span><span>块</span><span> </span><span>P80C31BH</span><span> </span><span>芯片（购价</span><span> </span><span>118.00</span><span> </span><span>元），更换了</span><span> SENSOR</span><span> </span><span>I/F#1</span><span> </span><span>板上</span><span> </span><span>CPU#1、CPU#2</span><span> </span><span>芯片</span><span> </span><span>，重校</span><span> </span><span>MLC</span><span> </span><span>叶片</span><span> </span><span>位置，试着开壳状态运行，故障未出现。3</span><span> </span><span>天后还原机头</span><span> </span><span>外壳再运行</span><span> </span><span>1</span><span> </span><span>周，故障排除。至今，加速器已使用半年有余，</span><span> 同类故障没有出现。</span></span></p><p><span><br  /></span></p><p><strong><span><span>4 </span><span> </span><span>小结</span></span></strong></p><p><span><br  /></span></p><p><span><span>充分利用大型设备所提供的自检程序和有力条件操作 设备，并有耐心追踪观察故障部位，尽可能缩小故障范围</span><span> </span><span>[6]</span><span>。</span></span></p><p><span><br  /></span></p><p><span><span>不要盲目动手维修，应分析电路图，有针对性的工作，</span><span>做到事半功倍。 </span><span>分段处理问题，近一步缩小故障范围。一定要仔细观</span><span>察设备表现出的故障现象。 对怀疑的易坏部件、要更换的元器件，要做实验验证，</span><span>排除故障可能性。</span><br  /></span></p><p><span> </span></p><p><p><img src="image/20201019/df1c2eb09b3189e573942cb954365e1d_2.png" /></p><br  /></p>