主要内容

选择Sample Time and Horizons

Sample Time

Duration

Recommended practice is to choose the control interval duration (controller propertyTs）最初，然后在调整其他控制器参数时将其保持不变。如果显而易见的是原始选择很差，您可以修改Ts。如果这样做，则可能需要重新调整其他设置。

定性，如Tsdecreases, rejection of unknown disturbance usually improves and then plateaus. TheTs性能高原取决于植物动态特征的价值。

However, asTsbecomes small, the computational effort increases dramatically. Thus, the optimal choice is a balance of performance and computational effort.

In Model Predictive Control, the prediction horizon,p也是一个重要的考虑因素。如果一个人选择持有预测范围的持续时间（产品p*Ts） 持续的，pmust vary inversely withTs。许多阵列尺寸与p。Thus, aspincreases, the controller memory requirements and QP solution time increase.

选择以下内容Ts:

  • As a rough guideline, setTsbetween 10% and 25% of your minimum desired closed-loop response time.

  • Run at least one simulation to see whether unmeasured disturbance rejection improves significantly whenTsis halved. If so, consider revisingTs。

  • 对于过程控制，Ts>> 1 s is common, especially when MPC supervises lower-level single-loop controllers. Other applications, such as automotive or aerospace, can requireTs<1 s。如果实时解决QP所需的时间超过所需的控制间隔，请考虑Explicit MPC选项。

  • 对于延迟的植物，建模延迟所需的状态变量数量与Ts。

  • 开环不稳定的植物,如果p*Tsis too large, such that the plant step responses become infinite during this amount of time, key parameters needed for MPC calculations become undefined, generating an error message.

单位

这controller inherits its time unit from the plant model. Specifically, the controller uses theTimeUnit植物模型LTI对象的属性。此属性默认为秒。

预测范围

假设当前的控制间隔为k。这prediction horizon,p, is the number of future control intervals the MPC controller must evaluate by prediction when optimizing its MVs at control intervalk。

尖端

  • Recommended practice is to choosepearly in the controller design and then hold it constant while tuning other controller settings, such as the cost function weights. In other words, do not usep调整控制器调整。相反，价值p应该使控制器内部稳定，并尽早预期违规行为以允许纠正措施。

  • 如果所需的闭环响应时间为Tand the control interval isTs， 尝试psuch thatT≈pts。

  • 植物延迟对可能的闭环响应时间施加了下限。选择paccordingly. To check for a violation of this condition, use thereviewcommand.

  • Recommended practice is to increasepuntil further increases have a minor impact on performance. If the plant is open-loop unstable, the maximumpis the number of control intervals required for the open-loop step response of the plant to become infinite.p> 50 is rarely necessary unlessTsis too small.

  • 不利的计划t characteristics combined with a smallpcan generate an internally unstable controller. To check for this condition, use thereview指挥并增加pif possible. Ifpis already large, consider the following:

Control Horizon

控制范围，m, is the number of MV moves to be optimized at control intervalk。控制视野落在1和预测范围之间p。这default ism= 2. Regardless of your choice form，当控制器运行时，使用了地平线开头的优化MV移动，并丢弃任何其他的MV。

尖端

保留的理由m<<pare as follows:

  • Smallmmeans fewer variables to compute in the QP solved at each control interval, which promotes faster computations.

  • If the plant includes delays,m<pis essential. Otherwise, some MV moves might not affect any of the plant outputs before the end of the prediction horizon, leading to a singular QP Hessian matrix. To check for a violation of this condition, use thereviewcommand.

  • Smallmpromotes (but does not guarantee) an internally stable controller.

定义样品时间和视野

您可以在创建一个样本时间，预测范围和控制范围mpccontroller at the command line. After creating a controller,mpcobj, you can modify the sample time and horizons by setting the following controller properties:

  • Sample time —mpcobj。Ts

  • 预测范围 -mpcobj。p

  • 控制视野 -mpcobj。m

Also, when designing an MPC controller using theMPC Designerapp, in theTuning标签，在地平线部分，您可以修改样品时间和视野。

See Also

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