Time and Motion

Among the difficulties in  mechatronics are the many relationships within any given system.  In most cases we approach each application from a certain perspective and somewhat randomly try to sort out he most important relationships in terms that are familiar to us as individuals.  For the mechanical engineer it is easiest to interpret mechatronics as mechanisms and the motion that is created when forces are applied.  For the electrical engineer* it is about the energy that needs to be supplied to create the necessary force.  For the controls engineer it can be the speed at which the motion is taking place and how to architect the control system in order to deliver the necessary regulation for the motion system to operate as intended.

* in the current era of manufacturing, regardless of the type of energy being used as the prime mover, whether pneumatic, hydraulic, or electric, most stationary systems start with a branch electrical circuit for primary power.  It is generally in mobile systems, farm equipment and off-road vehicles, that we see primarily combustion engine to direct mechanical or hydraulic systems. In recent years more engine to electric systems are finding favor as the increased efficiency available directly converts to 30-40% reduction in operating cost.

The best way to understand all the domains of motion is by relating them back to time.  Time is the only variable that connects everything in the system.

The two relationships of greatest importance are work over time and displacement over time.   Work over time is important because many important relationships can be defined.  What are the worst case operating conditions?  Most often starting the load is the worst case and can be directly defined by the mechanical engineer.  If the starting condition is 110%, which is common for centrifugal loads like pumps and fans, then the incoming electrical supply is known as well.  If there is potential for a stall condition, the engineer can define the limits which will permit precise circuit protection specifications to prevent catastrophic failure.

Displacement over time, how quickly the work must take place, helps define what types of mechanical systems are best suited for moving the load.  Other characteristics such as the need for position feedback, its accuracy and the control system update rates are all directly defined from this understanding.

So from the earliest days of time and motion studies in industrial manufacturing, the basic physics remain the same.

More to come on Time and Motion.

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