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## Kinematics Concepts    Kinematics Commands

FlexSim's kinematics functionality allows you to have a single object perform several travel operations through one common interface. Each travel operation can have its own acceleration, deceleration, startspeed, endspeed, and maximum speed properties. Travel operations can overlap with each other, or be performed in sequence.

Below is a time-based plot of two kinematics performed in sequence:

And a time-based plot of two kinematics that overlap each other:

Kinematics can also be used just to make it easier to handle the math for any logic that involves speeds, rates, accelerations, decelerations, etc.

As an example, an overhead crane usually has several motors that drive it. One motor drives the bridge along a railing, while another motor drives a trolley along the bridge, while another lifts the hook or grabber by a cable. Each of these motors may have their own acceleration, deceleration, and maximum speed properties. Using kinematics, you can define all of these motions through a single kinematics interface, where different motors can work simultaneously, giving the motion of the crane's end effector a very dynamic behavior. Before kinematics were introduced, the simplest way to simulate this behavior was to have three different objects hierarchically ordered in the model tree, each object simulating one motion or kinematic. While this works very well in some cases, in other instances it can become tedious and unfriendly. Kinematic functionality attempts to fix this problem by allowing one object to do several motions or kinematics simultaneously.

### Commands

1. initkinematics - This initializes data for the kinematics, saving things like the start location and rotation of the object you want to apply motion to.
2. addkinematic - This gives travel/rotate operations to the object. For example, you can tell the object, starting in 5 seconds and travel 10 units in the x direction, with a given acceleration, deceleration, and max speed. Then you can tell the object, starting in 7 seconds, travel 10 units in the y direction, with a different acceleration, deceleration, and max speed. The effect of these two operations is that the object will start traveling in the x, then will start simultaneously accelerating in the y, following a parabolic curved path to the destination. Each call to addkinematic will add another operation to the object.
3. updatekinematics - This command should be called when the object is being redrawn. This calculates the current position and rotation of the kinematics based on the current time, and sets the object's location to that position.

Refer to the Commands page for information about kinematics commands.

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