Yoshiharu Nishida

Robust Implementations Of Impedance Control Using Impedance Error Feedback

Robust implementations of impedance control against modelling errors and disturbances are proposed. Deviation between desired impedance and actual impedance in Cartesian space is defined and modelled as impedance error. Two type robust controllers are designed based on either a high gain feedback eliminating the impedance error or a compensator of the impedance error estimated by disturbance observer. The effectiveness of the proposed controllers is confirmed by numerical simulation and realized on a 2 degree-of-freedom planer direct drive manipulator. estimated by the disturbance observer. Proposed controllers deal with Cartesian space impedance error directly and compensate for this using the usual feedback control, less computational power is needed compared with that based on joint space or the complex control techniques. The effectiveness of the proposed controllers is confirmed by numerical simulation and realized on a 2 degree-of-freedom planer direct drive manipulator.

Stochastic moving horizon estimation for linear discrete-time systems with parameter variation

In this paper, we propose a novel state estimation algorithm for linear discrete time systems with modeling errors characterized by stochastic parameter variation. We extend the moving horizon estimation method to deal with a system with stochastic parameters and provide the optimal solution to a stochastic finite horizon state estimation problem. Furthermore, a numerical simulation shows the effectiveness of the proposed method.

On variational Bayes for identification of nonlinear state-space models with linearly dependent unknown parameters

In this paper, we propose a parameter estimation method for nonlinear state-space models based on the variational Bayes. We show that the variational posterior distribution of the hidden states corresponds to a posterior distribution of the states of an augmented nonlinear state-space model. From this, we can obtain the variational posterior distribution of the hidden states by implementing a variety of existing smoothing algorithms. Moreover, we assess with a simulation the predictive power of the proposed algorithm and the reliability of the estimated parameter.

Modelling of compressive hydraulic fluid in cylinders considering potential energy, state equation and energy loss

In this paper, we derive the potential energy and a state equation of compressible hydraulic fluid. In addition, we derive the energy being lost when hydraulic fluid moves between different pressures. Based on the derived equation, a hydraulic cylinder model assuming leakage at the piston is constructed. From the simulation results, we confirm that basic physical laws such as mass conservation law and energy conservation law are satisfied.

Level Control of a Continuous Casting Machine via H∞ Control Theory

In this paper, we apply H∞ control theory to the level-control of a continuous casting machine. The level-control has two major problems of parameter variations and disturbance-pattern variations. In order to cope with these problems, we make up a table which consists of multiple H∞ controllers. By switching one H∞ controller to another properly, adaptability as well as robustness is achieved. This method has been applied to an actual machine and the results show a 40% decrease in level error.