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# The basics of control theory

8/16/2010 12:18 PM EDT
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re: The basics of control theory
9/2/2010 7:29:02 AM
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There are many modifications of PID algotham. Modern PID controlers implement other features in their work.

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re: The basics of control theory
8/27/2010 5:11:25 AM
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arent' the gain terms supposed to be multiplied with the error rather than subtracted

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re: The basics of control theory
8/25/2010 5:36:10 PM
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John thanks for very informative article. I will be more interested in learning about tuning of PID loop. Will you please explain basic steps required. I will also like if you cover auto tune and self tune PID control algorithms. Are they available in library form? Can we employ and adept this PID controller for non-linear systems found in real life control?

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re: The basics of control theory
8/22/2010 6:42:18 AM
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Thanks for this article. This article on PID control basics was like a refresher course for me . I developed PID control algorithms for motion control applications involving control of servo motors back in 90's . What I learnt then was that in Position Control using servo motors a simple position control loop with PID does not always work. To have the smooth motion of the robotic actuator we need to have velocity control loop ( with its PID parameters) along with the interpolation algorithm where the set point command is constantly moved along with the desired path and desired trajectory ( linear/circular) to reach the final position.

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re: The basics of control theory
8/19/2010 4:48:21 PM
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The description reads properly to me. The accumulator is a digital substitution for the amalog integrator or totaliser. The error E times a factor K (the Integral Gain ) is the amount that changes the current value of the integrator(accumulator) at uniform time intervals. K is independent of the error and determines how fast the integrator racks up values from the varying error E. Therefore E is integrated and the overall effect is modified by K to be larger or smaller than if the integral of E were to be applied directly (K=1).

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re: The basics of control theory
8/19/2010 9:26:08 AM
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Great, I liked the bit about pitfalls of the 'I' in particular. One point I don't get though; the text says the following: "The integral term, however, is produced by multiplying the current error by the integral gain and adding the result to an accumulator." To me, the text implies "?(E*Ki)", rather than "Ki * ?E" or am I missing something?

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re: The basics of control theory
8/17/2010 4:37:10 PM
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PID control is still the king in many applications. I still remember developing a simple PID loop on a 8-bit MCU. One of the tricky parts was to tune the parameters Kp, Ki, Kd to achieve the desire performance.