{"id":217,"date":"2011-12-30T14:30:54","date_gmt":"2011-12-30T14:30:54","guid":{"rendered":"http:\/\/www.emtronics.co.uk\/wp_blog\/?p=217"},"modified":"2017-04-16T15:31:34","modified_gmt":"2017-04-16T15:31:34","slug":"testing-realtime-pid-in-simulink-on-hardware","status":"publish","type":"post","link":"http:\/\/www.emtronics.co.uk\/wp_blog\/?p=217","title":{"rendered":"Testing realtime PID in Simulink on Hardware"},"content":{"rendered":"

This information was contained in my Quatbot project post, but I have moved it here instead.<\/strong><\/p>\n

I decided to test out some PID control of the speed of a wheel in a project I was making. I thought it might be interesting to interface directly with Simulink in Matlab and try and use the provided Toolbox.<\/p>\n

This allowed the ability to capture data, control speed, and used the Simulink control block ‘live’ in real time with the hardware.<\/p>\n

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So in order to do this I connect the motor and optical sensor to an FPGA, the FPGA then connected via a serial link to the computer.<\/p>\n

Below show the setup used:<\/p>\n

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 <\/p>\n

Simulink allows the creation of custom blocks called S-functions. I created 2 S-functions, one for reading serial data – this acted as a Simulink source; and the other which wrote serial data – this acted as a Simulink sink.<\/p>\n

These 2 files are here:<\/p>\n

s_func_serial_input.m<\/a><\/p>\n

s_func_serial_output.m<\/a><\/p>\n

A picture of the hardware is show below:<\/p>\n

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Wheel speed VS PWM duty<\/strong><\/p>\n

Below shows actual wheel speed vs ramped input PWM duty. The flat bit at the start is a programmed dead zone, this was to try and make it slightly more linear. But as you can see, it is still very non-linear!<\/p>\n

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Wheel speed vs ramped input<\/strong><\/p>\n

In order to make the wheel speed linear w.r.t PWM duty, I created a lookup table in Matlab as follows:<\/p>\n