A tracking error–based fully probabilistic control for stochastic discrete-time systems with multiplicative noise

This article proposes the exploitation of the Kullback–Leibler divergence to characterise the uncertainty of the tracking error for general stochastic systems without constraints of certain distributions. The general solution to the fully probabilistic design of the tracking error control problem is first stated. Further development then focuses on the derivation of a randomised controller for a class of linear stochastic Gaussian systems that are affected by multiplicative noise. The derived control solution takes the multiplicative noise of the controlled system into consideration in the derivation of the randomised controller. The proposed fully probabilistic design of the tracking error of the system dynamics is a more legitimate approach than the conventional fully probabilistic design method. It directly characterises the main objective of system control. The efficiency of the proposed method is then demonstrated on a flexible beam example where the vibration quenching in flexible beams is shown to be effectively suppressed.

MASALAH GALAT PENJEJAKAN MINIMUM PADA SISTEM PENDULUM TERBALIK

This paper studies the optimal tracking error control problem on an inverted pendulum model. We characterize the optimal tracking error in term of pendulum’s parameters. Particularly, we derive the closed form expression for the pendulum length which gives minimum error. It is shown that the minimum error can always be accomplished as long as the ratio between the mass of the pendulum and that of the cart satisfies a certain constancy, regardless the type of material we use for the pendulum.

Minimum Tracking Error Control of Flexible Ball Screw Drives Using a Discrete-Time Sliding Mode Controller

This paper presents modeling, identification, and discrete-time sliding mode control of ball screw drives with structural flexibility. The mechanical system of the drive is modeled by a two degree-of-freedom system dominated by the coupled longitudinal and torsional dynamics of the drive assembly whose parameters are identified. A mode-compensating disturbance adaptive discrete-time sliding mode controller is then designed to actively suppress the vibrations of the drive. However, it is shown theoretically that, without using minimum tracking error filters, the tracking errors of the drive do not go to zero when sliding mode is reached. Therefore, a method for designing stable and robust minimum tracking error filters, irrespective of the identified open-loop behavior of the drive is proposed. The identification and control of flexible ball screw drives are experimentally tested, and the tracking accuracy of the drives is shown to improve considerably as a result of the designed minimum tracking error filters.

Model-Based Nonlinear Control of Ionic Polymer-Metal Composite Actuators

Ionic polymer-metal composites (IPMCs) are soft materials that can generate large deformation under a low voltage. IPMCs have many potential applications in biomedical, robotic and micro/nano manipulation systems. In this paper, we first present a distributed, nonlinear circuit model for IPMC, which incorporates the nonlinear capacitance, the nonlinear DC resistance, and the effect of surface resistance. The bending displacement is proportional to the total stored charge in IPMC. After discretizing the model in the length direction, we obtain a multiple-segment model which can be represented in the state space for nonlinear control design. The model is validated using experimental data, and we show that a one-segment model can predict the current and displacement response reasonably well. A model-based nonlinear controller is proposed for IPMC actuators, where feedback linearization is applied. Simulation results show that model-based nonlinear controller delivers better performance than a traditional PI controller in terms of the tracking error, control effort, and robustness to sensing noises.

A fast tracking error control method for an autonomous mobile robot

SUMMARYThis paper proposes a fast tracking error control method for a mobile robot with two differentially driven wheels. The tracking error between reference state and current state is transformed to the required displacement changes of each drive wheel by a wheel Jacobian. The major objective of this paper is to propose a control method for eliminating the tracking error quickly by controlling two independent driving wheels at the same time. To avoid long computational requirements of a Cartesian-based control, a kinematic model of the vehicle and co-ordinate system are introduced. Several simulation results are presented using this method. The fast tracking error control method proposed is mainly hardware-independent and Hence can be applied to various kinds of mobile robots which have two differentially driven wheels. The method was implemented on an experimental vehicle, WCVS, The experimentation shows a performance suitable for practical applications.