Fractional - order tilt integral derivative controller design using IMC scheme for unstable time - delay processes

The paper proposes a modified IMC-based Smith predictor (SP) control method for unstable time-delay processes. A novel design method to tune the parameters of a fractional-order tilt integral derivative controller has been developed using fractional-order IMC filter and process model parameters. The tuning parameters of the fractional-order filter are calculated from the new robustness index and desired performance constraint. The expected performance constraint satisfies good setpoint tracking and optimal control signal. The significant feature of the presented method is that the fractional IMC-SP structure provides a better outcome without adding much computational complexity. For a given robustness index, the optimal controller, which minimizes the performance constraint, the combination of control effort and integral time squared error, helps calculate the two tuning parameters. The benefit does verify under parameters’ uncertainties, external load disturbances and noise. The comparative study with various numerical examples from recently reported methods shows better overall servo and regulatory performances

Model reference pi controller tuning for second order inverse response and dead time processesand science

In this paper, a One-Degree-of-Freedom PI controller is optimized using the model reference tuning approach for a Second Order Inverse Response and Dead Time Process operating as a servo control. In addition, a graphic user interface tool that computes the PI optimized controller parameters is presented, also showing the response of the control system operating as a servo-control (the optimized one) and the associated response for the regulatory-control case.Universidad de Costa Rica/[731-B4-213]/UCR/Costa RicaUniversidad de Costa Rica/[322-B4-218]/UCR/Costa RicaConsejo Interinstitucional de Ciencia y Tecnología/[DPI2013-47825-C3-1-R]/CICYT/EspañaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII

A survey on fractional order control techniques for unmanned aerial and ground vehicles

In recent years, numerous applications of science and engineering for modeling and control of unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) systems based on fractional calculus have been realized. The extra fractional order derivative terms allow to optimizing the performance of the systems. The review presented in this paper focuses on the control problems of the UAVs and UGVs that have been addressed by the fractional order techniques over the last decade

Multivariable decoupling set-point approach applied to a wastewater treatment plant

This paper presents a formulation for the inclusion of the second degree of freedom for MIMO system for decoupling purposes. The proposal is specially effective when combined with decentralized feedback controllers. Loop interaction is of the major problems in the control of MIMO systems, as interaction can be considered as a disturbance coming from all other loops, the design of the decentralized feedback controller is better understood as a disturbance rejection design. In this approach the set-point tracking capabilities may be not as good as expected. The proposed Two-Degree-of-Freedom (2-DoF) formulation provides a complement to the existing controller that can be automatically determined in terms of the available process and feedback controller information.Universidad de Costa Rica/[322-B4-218]/UCR/Costa RicaUniversidad de Costa Rica/[731-B4-213]/UCR/Costa RicaMinisterio de Economía, Industria y Competitividad/[DPI2013-47825-C3-1-R]//EspañaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII)UCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería Eléctric

Verification of hardware-in-the-loop as a valid testing method for suspension development

A need for a cost effective, versatile and easy to use suspension component testing method has arisen, following the development of a four-state hydro-pneumatic semi-active spring-damper system. A method known as hardware-in-the-loop (HiL) was investigated, in particular its use and compatibility with tests involving physical systems – previously HiL was used predominantly for Electronic Control Unit (ECU) testing. The suitability of HiL in the development of advanced suspension systems and their control systems, during which various vehicle models can be used, was determined. A first step in vehicle suspension design is estimating a desired spring and damper characteristic, and verifying that characteristic using software simulation. The models used during this step are usually low-order, simple models, which hampers quick development progress. To predict vehicle response before vehicle prototype completion, many researchers have attempted to use complex and advanced damper models to simulate the vehicle’s dynamics, but these models all suffer from some drawback – it is either based on empirical data, giving no indication of the physical parameters of the design sought; it may be overly complex, having many parameters and thus rendering software impractical; or it may be quick but based on the premise that there is no hysteresis in the damping character. It can be seen that an obvious answer exists – use a physical commercially available or prototype damper in the software simulation instead of the mathematical model. In this way the suspension deflection, i.e. the true motion of the damper is used as excitation, and the true damper force is measured using a hydraulic actuator and load cell. The vehicle mass motions are simulated in a software environment. This is basically what HiL simulation does. The HiL method was verified by comparing HiL simulations and tests to globally accepted testing methods, employing widely-used vehicle models: linear single-degree-of-freedom (SDOF) and two-degrees-of-freedom (2DOF) or quarter-car models were used. The HiL method was also compared to a non-linear physical system to verify that the method holds for real vehicle suspension geometries. This meant that HiL had to perform adequately at both ends of the suspension-testing spectrum – base software and real system simulation. The comparison of the HiL and software/real system simulation was done using the “Error Coefficient of Variance” (ECOV) between the compared signals; this quantitative measure proved very sensitive and performed dubiously in the presence of signal offsets, phase lags and scaling errors, but remains a tangible, measurable parameter with which to compare signals. Visual confirmation was also obtained to back the ECOV values. It was found that even using a relatively low-force actuator, the HiL simulation results followed the software/real system responses well. Phase lags and DC offsets in the HiL simulation’s measured signals (as well as the real systems responses) has an adverse effect on the performance of the HiL simulation. Special attention must thus be paid to the zeroing of equipment and the amount/type of filters in the system, as these affect the HiL results dramatically. In all, HiL was proven to be a versatile and easy to use alternative to conventional mass-based suspension testing.Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006.Mechanical and Aeronautical Engineeringunrestricte