How can I generate a pulse with variable frequency?

I'm working on a Cable Robot project where I am expected to control the speed of the cables by changing the frequency of the stepper motors integrated in the system. I already sorted out how to generate a pulse with specific amount of steps for position control but I couldn't sort out how to alter with the frequency of the pulse.(For controlling the speed of the stepper motor)

Here is the set of blocks for generating a pulse with specific number of steps;

10 steps is generated in the given example

pulse type is time based and simulation time is used.

Thank you for your time

Answer 1

[Fangjun Jiang]

In this model, the number of pulses and the frequency of the pulse are coupled. The simulation step, the sample time of the counter and the frequency of the pulse generator all need to work together to get the desired output. After you got 10 pulses, if you double or half the frequency of the pulse generator, you won't get the desired output.

Varying the frequency of the pulse is a tough task. Many blocks have frequency as a parameter, not a time-varying input.

I have a suggestion. Make f as an input, multiple it with 2*Pi and then use "Fcn" block to do the sin() operation then you will get sin(2*pi*f) which is a variable-frequency sine wave. Compare it with zero will give you the pulse athough the pulse width is also changing.

Then you will have some blocks to count the pulses. If the pulse signal has a rising edge, add one. Otherwise, do nothing. Compare the counter with your preset number of pulses. Use this comparison to control a Swith, passing either the pulse signal or zero.

Voila

[Fazil Doruk Inanc]

Thank you again for your answer. Could you please provide a step by step instruction with the block types that I should use after obstructing sin(2*pi*f)

[Fangjun Jiang]

triggered subsystem (use rise edge as the trigger), z delay block used as the counter