One of the most difficult challenges to machine builders is understanding the notion of positioning and how it is reflected in component selection in their equipment design. Positioning an object based on a rotary or linear input can be really simple or really complicated. Everything you need to know is based on the work statement of the load.
There are 3 key elements of any motion control problem that need to be identified;
质量 - 移动的有效载荷有多少重量？有时它不仅仅是重量，但是重心可能是一个要求，即使在一些比较简单的情况下也是如此。考虑在将输送机上放在输送机上的填充，标记和密封的番茄瓶瓶中，以便将它们放入纸箱。不同的瓶子尺寸具有不同的重力。输送机的移动轮廓需要相当大的调整以调整由不同瓶尺寸提出的动量和扭矩臂。
——循环的速度有多快e time? This one is pretty obvious except for the fact that the mass of the object to be moved forces certain constraints on the acceleration required to move the part. As the time requirement decreases the torque required goes up arithmetically. It ain’t pretty when you are shaving milliseconds off of move times. The control system is not capable of making up the time required once the mechanical design is frozen. Simulation of the motion can reveal a great deal of information about where mechanical trade-offs can provide impact to the high speed goal.
Accuracy – what unit of feedback is required? Are we polishing at 50 millionths, or positioning a pallet full of breakfast cereal in an automated storage and retrieval warehouse? Positioning accuracy in these two systems are orders of magnitude apart. Accuracy considerations are also tied to speed. As the velocity increases the rate of feedback goes up in proportion. If the motion requires high speed, high resolution can become a problem for the control system bandwidth. In the real world the position accuracy depends on the sensor, so selecting a feedback device is something you want to spend some time doing carefully.
What is not obvious is that there are trade offs that can be very helpful. Understanding the real world motion and the rate at which things must happen is crucial to decision making in specifying motors, drives and controls. More feedback and higher acceleration capability may not be the right thing for your project. A 1200 pound roll of paper can only accelerate at a certain rate. To go beyond the natural frequency of the load, the motor would have to be bigger than the roll. Not gonna work out well.
Filed Under:Mechatronic Tips
