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Develop essential skills in tuning loops, control loop design, and troubleshooting. Gain a fundamental understanding of process dynamics and feedback control using Laplace Transforms. Learn to solve linear ODEs, apply Initial- and Final-Value Theorems, and utilize methods like Partial Fraction Expansions and Heaviside Method.
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Chapter 3 Laplace Transforms
Overall Course Objectives • Develop the skills necessary to function as an industrial process control engineer. • Skills • Tuning loops • Control loop design • Control loop troubleshooting • Command of the terminology • Fundamental understanding • Process dynamics • Feedback control
Laplace Transforms • Provide valuable insight into process dynamics and the dynamics of feedback systems. • Provide a major portion of the terminology of the process control profession.
Laplace Transforms • Useful for solving linear differential equations. • Approach is to apply Laplace transform to differential equation. Then algebraically solve for Y(s). Finally, apply inverse Laplace transform to directly determine y(t). • Tables of Laplace transforms are available.
Final Value Theorem • Allows one to use the Laplace transform of a function to determine the steady-state resting value of the function. • A good consistency check.
Initial-Value Theorem • Allows one to use the Laplace transform of a function to determine the initial conditions of the function. • A good consistency check
Apply Initial- and Final-Value Theorems to this Example • Laplace transform of the function. • Apply final-value theorem • Apply initial-value theorem
Partial Fraction Expansions • Expand into a term for each factor in the denominator. • Recombine RHS • Equate terms in s and constant terms. Solve. • Each term is in a form so that inverse Laplace transforms can be applied.
Example of Solution of an ODE • ODE w/initial conditions • Apply Laplace transform to each term • Solve for Y(s) • Apply partial fraction expansions w/Heaviside • Apply inverse Laplace transform to each term
Overview • Laplace transforms are an effective way to solve linear ODEs.