Showing papers by "Zexiang Li published in 1992"

Nonholonomic Motion Planning

Abstract: Nonholonomic kinematics and the role of elliptic functions in constructive controllability, R.W. Brockett and L. Dai steering nonholonomic control systems using sinusoids, R.M. Murray and S. Shakar Sastry smooth time-periodic feedback solutions for nonholonomic motion planning, L. Gurvits and Zexiang Li lie bracket extensions and averaging - the single-bracket case, H.J. Sussmann and Wensheng Liu singularities and topological aspects in nonholonomic motion planning, J.-P. Laumond motion planning for nonholonomic dynamic systems, M. Reyhanoglu et al a differential geometric approach to motion planning, G. Lafferriere and H.J. Sussmann planning smooth paths for mobile robots, P. Jacobs and J. Canny nonholonomic control and gauge theory, R. Montgomery optimal nonholonomic motion planning for a falling cat, C. Fernandes et al nonholonomic behaviour in free-floating space manipulators and its utilization, E.G. Papadopoulos.

Stable Controllers for Instantaneous Optimal Control

Abstract: Recently, instantaneous optimal control algorithms were proposed and developed for applications to control of seismically excited linear, nonlinear, and hysteretic structural systems. In particular, these control algorithms are suitable for aseismic hybrid control systems, for which the linear quadratic optimal control theory is not applicable. Within the framework of instantaneous optimal control, the weighting matrix Q should be assigned to guarantee the stability of the controlled structure. A systematic way of assigning the weighting matrix by use of the Lyapunov direct method is investigated. Based on the Lyapunov method, several possible choices for the weighting matrix are presented, and their control performances are examined and compared for active and hybrid control systems under seismic loads. It is shown that the performance of the stable controllers presented herein are remarkable.

Aseismic hybrid control of nonlinear and hysteretic structures. II

Abstract: Instantaneous optimal control for nonlinear and inelastic systems is formulated incorporating the specific hysteretic model of the system. The resulting optimal control vector is obtained as a function of the total deformation, velocity, and the hysteretic component of the structural response. The hysteretic component of the response can be estimated from the measured structural response and the hysteretic model used. It is shown that the optimal control vector satisfies not only the necessary conditions, but also the sufficient condition of optimality. Specific applications of the optimal algorithm to two types of hybrid control systems are demonstrated. These include: (1) Active control of base-isolated buildings using frictional-type sliding base isolators; and (2) active control of base-isolated buildings using lead-core rubber bearings. Numerical examples are worked out to demonstrate the applications of the proposed control algorithm. It is shown that the performance of such an optimal algorithm is an improvement over that of the algorithm that does not consider the hysteretic components in the determination of the control vector.

Attitude control of space platform/manipulator system using internal motion

Abstract: The authors formulate the dynamic equations of a system consisting of a 3-degree-of-freedom Puma-like manipulator attached to a space platform (e.g. a space station or a satellite) as an NMP (nonholonomic motion planning) problem and discuss controllability of the system. They describe the application of a simple algorithm for obtaining approximate optimal solutions. They conclude with results of a simulation experiment. >

Control of hysteretic system using velocity and acceleration feedbacks

Abstract: Optimal control algorithms usually involve a state feedback including displacements and velocities. For control of building structures subjected to strong earthquake ground motions, it is much easier to measure the acceleration response than the displacement response. In this paper, a version of the instantaneous optimal algorithm, using velocity and acceleration feedbacks, for nonlinear or hysteretic structural systems is presented. Stable controllers are obtained using the Lyapunov direct method. The Lyapunov function for the controlled nonlinear structure is obtained through an appropriate transformation. The optimal algorithm is applied to control of a hysteretic building structure equipped with an aseismic hybrid control system. It is demonstrated numerically that for the particular hybrid control system considered, the performance of the present control algorithm is as good as the previous algorithm, which uses the displacement response of the structure for the determination of the control vector.