OPTIMAL OUTPUT FAST FEEDBACK IN TWO-TIME SCALE CONTROL OF FLEXIBLE ARMS

Control of lightweight flexible arms moving along predefined paths can be successfully synthesized on the basis of a two-time scale approach. A model-following control can be designed for the reduced-order slow subsystem. The fast subsystem is a linear system in which the slow variables act as parameters. The flexible fast variables which model the deflections of the arm along the trajectory can be sensed through strain gage measurements. For full state-feedback design the derivatives of the deflections need to be estimated. The main contribution of this study is the design of an output feedback controller which includes a fixed-order dynamic compensator, based on a recent convergent numerical algorithm for calculating LQ optimal gains. The design procedure is tested by means of simulation results for the one-link flexible arm prototype in the laboratory

Output-feedback 2-time Scale Control of Multilink Flexible Arms

Lightweight flexible arms will most likely constitute the next generation robots. The design key is the adoption of flexible links, rather than rigid links like in today's industrial robots. Despite all the potential advantages achievable with a flexible arm, the control problem is complex, due to the introduction of increasingly more complex dynamics. This paper represents an effort toward the goal of designing efficient control systems for multilink flexible arms. A two-time scale approach is pursued which allows the adoption of a composite control strategy. First a slow control can be designed for the slow (rigid) sybsystem, then a fast stabilizing control for the fast (flexible) subsystem. The main contribution of the paper is to address the problem of lack of full state measurements concerned with the fast control design. An output feedback dynamic compensator of fixed order is designed. Its optimal gains are computed according to a loop transfer recovery technique in order to obtain a robust design. The control is tested by means of simulation results for a nonlinear model of a two-link flexible arm

Robust Control of Hypersonic Vehicles Considering Propulsive and Aeroelastic Effects

The in uence of propulsion system variations and elastic fuselage behavior on the ight control system of an airbreathing hypersonic vehicle is investigated. Thrust vector magnitude and direction changes due to angle of attack variations a ect the pitching moment. Low structural vibration frequencies may occur close to the rigid body modes in uencing the angle of attack and lead to possible cross coupling. These effects are modeled as uncertainties in the context of a robust control study of a hypersonic vehicle model accelerating through Mach 8 using H1 and synthesis techniques. Various levels of uncertainty are introduced into the system. Both individual and simultaneous appearance of uncertainty are considered. The results indicate that the chosen design technique is suitable for this kind of problem provided that a fairly good knowledge of the e ects mentioned above is available. The order of the designed controller is reduced but robust performance is lost which shows the need for xed order design techniques. 1