Optimal Finite Wordlength Digital Control With Skewed Sampling - American Control Conference, 1994

Qptinnrrni controller designs are developed which take account of the digital round-of€ errors in the controller implementation and in the A/D and D/A converters for the case of uniform skewed sampling. Skewing the control samples allows the computational delay in the control computer t o be accommodated in the optimization problem. These results provide a very general extension to the LQG theory since they reduce to the standard LQG controller when infinite precision compiitation is used, and there is no computational delay (the sm!pliiig is synchronous). Penalties are added to the cost liiiictiori to prita.lize the sum of the wordlengths used to compiit(, thc: frnct.iona1 parts of the controller state variables, and t I i c wordlengths of the A/D and D/A converters. Hence, controller complexity is traded with performance. Control design for a. large flexible structure at the Jet Propulsion Laboratory demolistrates the performance improvement of the proposed inet.liodology versus the standard LQG approach.