Motion control system
In fact, a motion control system is a relatively large system, much like the communication system mentioned earlier, and it is usually composed of many components. A motion control system integrates signal analysis and processing, automatic control, communication, and other aspects.
Elements of motion
In abstract terms, the elements of motion can be summarized as follows: object, frame of reference, state description, state change, and driving force. Therefore, the motion of an object, simply put, is the change in the state of the object within a specific frame of reference under the action of a force.
In the design phase of a motion system, the first step is to clarify the motion elements mentioned here and their interrelationships, which is the process of "modeling." "Modeling" is the foundation of motion control.
object
An object is the entity we use for motion control. For motion control, the object is usually defined.
Different objects exhibit different characteristics, and therefore will respond differently and move differently when subjected to forces. We usually need a thorough understanding of the object in order to control it, and this process of understanding the object is called "modeling," which involves recognizing the characteristics of the object's state changes when subjected to forces.
In practical applications, the object is described in different simplified ways at different stages of the design of a motion control system, and this is something to be aware of. Sometimes the object is treated as a point mass, sometimes as a rigid body with shape, and sometimes it is described according to its actual shape. This point will be summarized in the following discussion.
Reference frame
In fact, motion is relative; therefore, describing the "motion" of an object presupposes establishing a frame of reference in which the object is viewed. Once the frame of reference is determined, the object's state can be described. "Motion" refers to a change in the object's state within that frame of reference. Therefore, we can see that the description of "motion" always depends on both the frame of reference and the state description.
A frame of reference is the foundation of motion; without a defined frame of reference, it is impossible to perform clear motion control on an object.
The description of "motion" is usually not unique; the same object can be described differently in different frames of reference. Moreover, in practical applications, there is not just one frame of reference for an object; there are many different frames of reference to allow for a reasonable description of the object in different situations. For example, in the motion control of unmanned aerial vehicles (UAVs), the body coordinate system, navigation coordinate system, and airflow coordinate system are frequently used.
In mathematics, a frame of reference is described by a coordinate system. Common coordinate systems include rectangular coordinates and spherical coordinates. Different coordinate systems are suitable for describing different motion scenarios. Among them, the rectangular coordinate system best matches human perception of space and is therefore widely used.
Status Description
Once a frame of reference is determined, the state of an object within that frame can be determined. The state of an object is uniquely determined within the frame of reference; otherwise, it would be impossible to provide a clear description.
We may have different state descriptions in different coordinate systems, but the transformation relationships between these state descriptions must be fixed and explicit, that is, the state descriptions of an object in different coordinate systems can be transformed into each other. Moreover, in typical motion control systems, since different motion control purposes are performed, different coordinate systems are used to describe the motion state for convenience, and then the interrelationship is achieved through coordinate system transformation.
