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在两种固体之间建模接触力

当对彼此接触的实心块进行建模时，接触力在固体块的行为方面起着重要作用。正常力，Fn和摩擦力，FF，可能导致模型的行为发生巨大变化。接触部队在许多不同的建模情况下发挥了作用，例如：

  • 包装输送机

  • Robotic movement

  • 赛车动态

这空间接触力基础和追随者框架固体固体之间的块模型。当连接两个实体块时空间接触力块大小相等,方向相反的力量以及适用于有限公司mmon contact plane. These forces conform to Newton's Third Law. The normal force is applied based on the penetration depth and the penetration velocity. If applied, the frictional force is based on the normal force and the relative velocities at the point of contact.

Simscape™ Multibody™使用penalty methodFor modeling contact between bodies, which allows the bodies to penetrate a small amount. Contact forces in the normal direction are computed using a spring-damper force law: the deeper the penetration and the greater the relative velocity in the penetration direction, the greater the normal contact forces.

空间接触力块力

这空间接触力block properties are divided into three expandable nodes:正常力，，，，摩擦力，，，，andSensing。使用时设置这些属性空间接触力block to model the contact forces between two solid bodies.

有关这些属性的更多信息，请参见空间接触力。

正常力

Parameters in the Normal Force section are used to determine the normal force,Fn，两个固体互相施加。You can specify theStiffness，，，，减震，，，，and过渡区域宽度。

摩擦力

摩擦力部分中的参数用于确定摩擦力，即FF，两个固体互相施加。如果您设置方法至光滑的粘滑，，，，then you can specify the静态摩擦系数，，，，Coefficient of Dynamic Friction，，，，andCritical Velocity。当这些选项不可用时方法is set toNone。

Sensing

除了建模两个实体块之间的接触外，您还可以使用空间接触力感觉障碍：

  • Separation Distance—The distance between two solid bodies

  • 正常力 - 每个固体施加的正常力。

  • 摩擦力幅度 - 每个固体施加的摩擦力。

要启用这些选项，请打开空间接触力块属性。在下面Sensing，，，，select the properties that you want the block to sense. For each property, a port is exposed on the block. Connect these ports to a viewer of your choice.

连接到实心块

这空间接触力块并不固有地知道有关两个连接固体的信息。在实心块参数中，启用出口：整个几何形状option.

一旦启用了一个新的几何端口，G，出现在您的实心块上。

Connect the geometry port to the base or follower port on the空间接触力堵塞。按照您的其他实体块的相同步骤，并将其连接到其余端口。要了解有关基础和追随者框架的更多信息，请参阅选择测量框架。

接触建模的考虑因素

Compared to modeling the mechanical relationships in a multibody system, modeling contact presents more choices, and the chosen methods can impact simulation speed, accuracy, and model maintainability.SIMSCAPE多体提供基本的接触建模构造，但是有很多使用它们的方法。

Solver Parameters

这computed normal contact forces are continuous functions of penetration depth and penetration velocity.SIMSCAPE多体当深度小于小于过渡区域宽度。增加过渡区域宽度降低了接触力的清晰度，使系统更容易使求解器前进，但可以允许更多的穿透力。减少过渡区域宽度gives the contact forces a sharper profile, closer to idealized rigid-body contact. However, decreasing the过渡区域宽度也可能降低求解器性能。

将最大步长设置为1E-3秒或更低可提高许多型号的准确性。降低相对求解器的耐受性会产生相似的效果。但是，减小步长也降低了模拟速度。

Explicit solvers, such asode45，，，，are usually better for systems with many rapid collisions or contact changes. Implicit solvers may struggle under such circumstances. If the contact changes are infrequent and more stable, implicit solvers may offer a speed advantage due to their ability to handle the stiffness introduced by the contact forces.

限制穿透深度

这separation distance between two solid blocks is positive when the two geometries are not in contact, zero when they are touching, and negative when there is nontrivial penetration between the geometries. When the separation distance is negative, its magnitude is also known as the穿透深度。穿透深度是几何位置和方向的连续函数。

SIMSCAPE多体使用针对小型接触模型应用调整的几何分析算法。某些算法假设与几何形状的大小相比，穿透深度很小。如果不是这种情况，则计算出的（负）分离距离可能仅是近似值，或可能表现出不连续性，并且所得的接触力可能不稳定。为了获得最佳效果，请限制模型中的渗透深度。

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