概觀
REPOSITION模式用于驅動過程到約束內芯咧，從而使得階躍測試可能恢復抒痒。在TEST, TEST NO-PULSE或SUSPEND模式下遵倦，當CV在測試限（STCVMIN/ STCVMAX）外STCVDELTA以上時其將自動觸發(fā)该默。（詳情請參閱CORRECTING模式幫助中有關配置CV違反約束時REPOSITION或CORRECTING模式是否會自動觸發(fā)的內容案糙。）當觸發(fā)REPOSITION模式后绊诲，當前的MV階躍測試將被放棄送粱，DMCplus引擎將恢復對該組的控制。為將每個CVs都移動到測試限內掂之，測試組中所有的MVs都將變得活躍抗俄。
REPOSITION模式遵循以下規(guī)則：
?當一個CV超出測試限（STCVMIN和STCVMAX）STCVDELTA以外時將觸發(fā)REPOSITION模式。
?REPOSITION模式觸發(fā)的最少時間由STREPOMAX* SSMINS指定世舰。經過STREPOMIN* SSMINS后如果所有的CVs都在測試限內至少1/2STCVDELTA动雹，測試組將繼續(xù)測試。
?經過STREPOMAX* SSMINS后如果所有的CVs都在測試限內跟压，那么測試組將繼續(xù)測試胰蝠。
REPOSITION模式可以通過手動設置STGREQ至REPOSITION觸發(fā)。這對測試初期或發(fā)生顯著測試限變化時為流程做好準備是非常有用的震蒋。
避免CORRECTING和REPOSITION模式
盡管一些CORRECTING, REPOSTION和CONTROL模式的數據也可用于模型識別茸塞，測試過程中一個主要目標是限制應用處于CORRECTING或REPOSITION模式的時間。在不違反最大MV階躍大小和CV測試限的前提下查剖，智能向導引擎所使用的階躍大小算法將盡可能嘗試最大的階躍輸出钾虐。鑒于各種不確定性，若CV違反約束梗搅，測試人員依然可以進入CORRECTING或REPOSITION模式禾唁。測試人員是不斷將過程推向測試限的，但由于可能使用較差的模型无切，它會經常對限制響應過量或不足。
整定以避免CORRECTING或REPOSITION模式包括以下內容：
?設置適當的測試限(STCVMIN和STCVMAX)丐枉。限制應設置成假設它們很可能被侵犯哆键。
?CV安全裕度(STCVDELTA)是一個指示觸發(fā)REPOSITION模式前超出限制容忍量的整定參數。
?在測試模式中瘦锹，STSTEPFRAC是一個影響所有MV階躍大小的全局參數籍嘹。它反映了你對模型的信心闪盔，以及可以用來避免過多的違反約束。
在測試中一個好的策略是將界限和安全裕度設置在合理的值辱士，然后使用STSTEPFRAC參數盡快動作泪掀。隨著新的，改進的模型被投用颂碘，測試中可以通過增加STSTEPFRAC來最大化階躍尺度异赫。
也可以看看
智能向導應用的校正模式
智能向導應用中的校正動作
智能向導應用的參數整定
附原文：
Overview
REPOSITION mode is used to drive the process within constraints so that step testing may resume. It may be triggered automatically from TEST, TEST NO-PULSE or SUSPEND modes when a CV is more than STCVDELTA outside of the test limits (STCVMIN/STCVMAX). (See CORRECTING mode for help on configuring whether REPOSITION or CORRECTING mode will be triggered automatically by CV violations.) When REPOSITION mode is triggered the current MV step test is abandoned and the DMCplus engine resumes control of the group. This means that all of the MVs in the group may become active with the goal of moving each of the CVs within their test limits.
REPOSITION mode is governed by the following rules:
?REPOSITION mode is triggered by a CV that is more than STCVDELTA outside of its test limits (STCVMIN and STCVMAX).
?REPOSITION mode is triggered for a minimum of time specified by STREPOMAX×SSMINS. After STREPOMIN×SSMINS if all of the CVs are at least ? STCVDELTA inside the test limits then the group will resume testing.
?After STREPOMAX×SSMINS if all the CVs are inside the test limits then the group will resume testing.
REPOSITION mode can be triggered manually by setting the STGREQ to REPOSITION. This can be useful for getting the process ready for testing initially or when significant test limit changes have been made.
Avoiding CORRECTING and REPOSITION mode
Although some CORRECTING, REPOSTION and CONTROL mode data can be used for identification, a major goal during testing is to limit the amount of time the application spends in CORRECTING or REPOSITION mode. The step size algorithms used by the SmartStep engine will try to make the largest step that does not violate either the maximum MV step size or any CV test limits. Because of various uncertainties, the tester may still enter CORRECTING or REPOSITION mode due to CV limit violations. The tester is constantly pushing the process toward test limits, but since it is using potentially poor models, it will frequently overshoot or undershoot the limits.
Tuning to avoid CORRECTING or REPOSITION mode includes the following:
?Setting the test limits appropriately (STCVMIN and STCVMAX). The limits should be set with the assumption that they will likely be violated.
?The CV Safety Margin (STCVDELTA) is the tuning parameter that indicates how much overshooting of the limits will be tolerated before triggering REPOSITION mode.
?STSTEPFRAC is the overall parameter that affects all MV step sizes in test mode. It reflects a confidence in your models, and it can be used to avoid excessive constraint violation.
A good strategy is to set the limits and the safety margins to reasonable values, and then use the STSTEPFRAC parameters to temper moves early in the test. As new, improved models are brought online, STSTEPFRAC can be increased to maximize the step size used during the test.
See Also
CORRECTING mode in a SmartStep application
Correcting moves in a SmartStep application
Tuning parameters in a SmartStep application
2015/10/28
