Smart cams
June 10, 2008
On the other hand it requires a computer system that allows the user to design electronic cams which will need. At the same time it was necessary in most cases to think carefully about cams to load, since the programmer needed each time that it wanted to introduce some modification.
Subsequently, solutions such as the 'teaching' or point clouds have provided more or less good approximations that did not require the presence of the programmer. Today the existence of as powerful as the Matlab mathematical programs, allow to obtain approximations to the curve in polynomial form with great precision. In the case of B & R one can define a single cam with up to 64 sections of consecutive sixth degree polynomials; Thus is done to minimize the error when it comes to the movement that has been designed in a simple way. In this case already we do not need the intervention of the programmer, because that would be sufficient to introduce the terms of polynomials through a user's screen.
Cam on the fly
B & r solution in these cases is very effective because it applies the principle: "Let the servodrive decides the movement in that part of the cam where it is not fixed". In other words, the Acopos or Acoposmulti is responsible for uniting the sections in which we define a behavior-fixed position and/or speed (CAM) with curves that will optimize the movement to make this as smooth as possible. In this way it optimizes the time of the path, the current consumption and extends the life of the engine.
However in the most demanding applications, not only requires great flexibility in the creation of the camshaft, but also in its use. A clear example is the decision-making on the cam to go at any given time. For example, a cut to the very critical flight time would be much more effective if decisions on the exact time of beginning of the movement is carried out by the own servodrive; Thus it is not necessary to wait for the automaton to send the boot order via a field bus. This possibility also offer the Acopos and Acoposmulti, servo, based on some predetermined events, making decisions in only 400 µs. This listing improves the accuracy and speed in responding to external events. The sooner you react, the lower the accelerations necessary to adapt the movement; so also this improvement allows us to improve the dynamics and less abrupt movements.
Virtual axes and axis additives
The contribution of the Acopos and Acoposmulti servo returns to be very interesting, because they have links in which the teacher can change in real time. I.e. that the servodrive can make decisions in real time (as we saw earlier) where also involved cam can be seen with different teachers. This fact allows us to increase very significantly the possibilities for solutions to complex problems, as we can fit us as slave to any of the virtual axes of any other servodrive present in the network.
A step further in the flexibility gives it us the use of slave axes additives and additive master axes. Its use is another way to make corrections and adjust the position of the master and the slave. The scheme of the behavior of the additive additive and master slave axes is that seen in the graphic attached. Once again, any virtual axis or accessible external axis in the network can serve as master, master axis additive or additive slave.
Calculating with the axes
-Arithmetic operations
-Multiplexed
-Tweens
-Filtering
-Limitation
-Delays
These operations conducts the own servodrive internally in a cycle time of 400 µs, which is the same cycle time to the position of the servo loop. In this way operations are executed while is the reading of the positions of encoder and the generation of new slogans.
Much more than a counterpart relationship
However in the servo Acopos and Acoposmulti will use this editor to define any type of relationship that defines us the inner workings. Here are some examples:
-Motto of couple in function of the speed or time
-Motto of speed depending on width of coil
-Limitation of speed depending on the temperature of the engine
-Gain loop speed and position based on the own speed
In these cases the editor of camshaft is not more than a simple way of defining the relationship between two parameters, which can be subsequently assigned to torque, speed, temperature, time, the PID controller parameters or simply the position. Thus the link between master and slave is not only one of many utilities allowing us the use of the editor of camshaft. Or rather, it's one of the many utilities that you can associate with a clever use of own cam editor, whose only limit, now yes, give us it needs and our own creativity.