Rookie learn four-axis Controller 1: What is interpolation?

I've seen the Handbook of motion control chips before, including Nova's MCX314 and PCL6045, and know the concept of interpolation.

But what exactly is interpolation, in fact, has always been a little puzzled, and then silly to ask some experts, their argument is:

Interpolation can be multi-axis output at the same time, fast. And then I don't know what to ask.

Based on my previous experience in stepping motor, as well as my experience in testing stepper motor drivers, I typically use a single-chip microcomputer to send a fixed pulse to test the performance of a drive. If you need to test the torque characteristics of the motor at various speeds, up to the S-plus deceleration curve, in my opinion, to draw a straight line, it is too simple, the direct x-axis and the y-axis at the same time to different speed pulse is not OK?

To draw a circle and a variety of curves, also very similar ah, why to join the concept of interpolation?

Later, in a certain degree to check the concept of interpolation, know that the interpolation algorithm is a data compaction process.

So, yes, I am a super rookie, because:

1, the theory of numerical control and the theory of multi-axis controller, basically is heard.

2, I graduate of electronic information, graduated for many years has been to do is stepping drive this piece of hardware design.

Based on the stepper drive has not much profit, as well as the company's development needs, I intend to start from the rookie, learning the theory of the controller, I hope that they can win a year or so, design a complete, for four-axis control engraving machine controller.

Although it is very food, but there is a little bit of resources:

1, although the controller understanding is not deep, but the stepper drive market and technology have a certain understanding.

2, there are many customers and friends, can use such a controller, if the cost to do down, low-end also has a low-end market, to do which step to calculate which step, one step to the upper arch.

is for my present state.

During the weekend, I plunged into the museum of the old books of Hunan University, and spent two hours on two books:

"CNC technology and application of machine tools": There are two main chapters of the content, it seems very important at present:

1, the control principle of CNC machine tool

2. Servo drive system of CNC machine tool

The second part of the content, a variety of motors are familiar with, especially the stepper and servo familiarity, see what needs to be added to the theoretical knowledge.

What the hell is interpolation?

Interpolation is the core of CNC system!!! And I've never been serious about it before!

Interpolation has a lot of algorithms, mainly can focus on the reference pulse interpolation algorithm and data sampling interpolation algorithm:

1, the reference pulse interpolation:

Open-loop CNC system for stepping and other medium precision.

For stepping: At least what I want to study now is a low-end engraving machine based on stepping.

Medium accuracy: Well, the high-precision I did not pay too much attention, should be used to the servo is high precision bar.

Open-loop CNC system: Well, this is about 2000 yuan of the controller, it should be open-loop CNC system bar.

Output mode: Pulse mode, stepper motor and low-end servo are used in this way to control, engraving machine is in this way, and, MCX314 is this simple reference pulse interpolation method?

The reference pulse interpolation also uses data sampling for fine interpolation.

Two main algorithms for reference pulse interpolation:

1. Comparison by point

2. Digital Integral method

There's something else. Compare points, digital pulse multiplier What, the book said with less.

The question is, MCX314 and PCL6045 use the point-by-bit comparison method in the reference pulse interpolation?

2, Data sampling interpolation:

The output is not a pulse, but a binary data.

This should be used mainly for the control of the network port or can bus and other means.

Data sampling interpolation has two processes, one is coarse interpolation, one is refined interpolation, the process of coarse interpolation, will be processed by the length of L into the T cycle for processing, l=ft, divided into small segments, re-data compaction, for fine interpolation.

The interpolation period is a little longer, including interpolation operations and other real-time operation tasks of the controller, such as display.

Japan Fanuc The interpolation period is 8ms, wherein the sampling period is 4ms, now many manufacturers to achieve 1ms within.

Arc interpolation, secant precision is better, but the calculation of comparative load, less application, so more directly with the chord.

AC/DC closed-loop/semi-closed loop usually used in this way, should be to sample the location of the specific movement, so the calculation is also more complex, so the speed is slower.

The main algorithms of data sampling interpolation include the linear function method and the extended digital integration method.

Four-axis engraving machine used to open-loop system, should not use this data sampling interpolation algorithm.

Rookie learn four-axis Controller 1: What is interpolation?