Backlash Compensation for Plants With Saturating Actuators

A compensation scheme is proposed for plants subject to both saturation and backlash in series at the actuator. It is shown that the series connection of a backlash inverse, saturation and the backlash itself is equivalent to a saturation function at a different level to the original saturation, and we call this the ‘saturation equivalence’. Therefore, it is proposed to include such a backlash inverse in the compensator. This is shown to be optimal in a sense defined in the article. It is then straightforward to devise a compensator scheme based on traditional anti-windup. This is illustrated in both simulation and on a laboratory scale rig with severe backlash. A correction for the chattering observed in the control signal due to the discontinuous nature of the nonlinearity inverse is also presented. </jats:p

Liquid rocket actuators and operators

All the types of actuators and associated operators used in booster, upper stage, and spacecraft propulsion and reaction-control systems except for chemical-explosive actuators and turbine actuators are discussed. Discussion of static and dynamic seals, mechanical transmission of motion, and instrumentation is included to the extent that actuator or operator design is affected. Selection of the optimum actuator configuration is discussed for specific application which require a tradeoff study that considers all the relevant factors: available energy sources, load capacity, stroke, speed of response, leakage limitations, environmental conditions, chemical compatibility, storage life and conditions, size, weight, and cost. These factors are interrelated with overall control-system design evaluations that are beyond the scope of this monograph; however, literature references are cited for a detailed review of the general considerations. Perinent advanced-state-of-the-art design concepts are surveyed briefly

Hybrid modeling and control of mechatronic systems using a piecewise affine dynamics approach

This thesis investigates the topic of modeling and control of PWA systems based on two experimental cases of an electrical and hydraulic nature with varying complexity that were also built, instrumented and evaluated. A full-order model has been created for both systems, including all dominant system dynamics and non-linearities. The unknown parameters and characteristics have been identi ed via an extensive parameter identi cation. In the following, the non-linear characteristics are linearized at several points, resulting in PWA models for each respective setup. Regarding the closed loop control of the generated models and corresponding experimental setups, a linear control structure comprised of integral error, feed-forward and state-feedback control has been used. Additionally, the hydraulic setup has been controlled in an autonomous hybrid position/force control mode, resulting in a switched system with each mode's dynamics being de ned by the previously derived PWA-based model in combination with the control structure and respective mode-dependent controller gains. The autonomous switch between control modes has been de ned by a switching event capable of consistently switching between modes in a deterministic manner despite the noise-a icted measurements. Several methods were used to obtain suitable controller gains, including optimization routines and pole placement. Validation of the system's fast and accurate response was obtained through simulations and experimental evaluation. The controlled system's local stability was proven for regions in state-space associated with operational points by using pole-zero analysis. The stability of the hybrid control approach was proven by using multiple Lyapunov functions for the investigated test scenarios.publishedVersio

Asymptotic and transient behaviour of nonlinear control systems

In this thesis, the problem of controlling both transient and asymptotic behaviour of solutions of functional differential equations is addressed. The work begins, in Chapter 1, with an introduction to basic control theory principles that will be used throughout. This is followed by the introduction of a class of nonlinear operators in Chapter 2 and the development of suitable existence theories for the associated system classes of functional differential equations and inclusions in Chapter 3. A discussion is provided, in Chapter 2, describing diverse phenomena, such as delays and hysteresis, that can be incorporated in the class of operators. Chapters 4-7 cover four areas of research. Chapter 4 examines the asymptotic and transient behaviour of nonlinearly-perturbed linear systems of known relative degree; a continuous feedback strategy is adopted and an approximate tracking result is presented. In Chapter 5 the class of systems considered is expanded to a large class of nonlinear systems and a continuous feedback strategy is implemented in order to achieve approximate tracking. In Chapters 6 and 7 attention is restricted to systems f relative degree one, but this limitation is compensated for by targeting an exact asymptotic tracking result. The first investigation, in Chapter 6, involves a potentially discontinuous feedback controller applied to a class of nonlinear systems, with comparisons made to an internal model approach. Asymptotic tracking and approximate tracking are developed in unison within a framework of functional differential inclusions. Finally, in Chapter 7, a continuous controller is applied to single-input, single-output, nonlinear systems with input hysteresis.EThOS - Electronic Theses Online ServiceGBUnited Kingdo