This paper describes a possibility to increase the operation range of railway's pure electric braking system at low speed range. Since low-resolution speed encoders are normally installed, precise speed information is unavailable at low speed. An estimation scheme called instantaneous speed observer is introduced to estimate the speed for precise torque and speed controls. The stability of the system is analyzed by multirate sampling theory and digital control theory. Several simulation results and experiments positively show the improvement of speed estimation and the possibility to extend the operation of the pure electric brake.
This paper considers the gauge and tension control problem in tandem cold rolling. An optimal multivariable solution is proposed via the extended ILQ (Inverse Linear Quadratic) design theory. Analytical investigation provides to simplify and to generalize controller structure. Stability analysis confirms its robust stability under certain perturbation. Actual data of Kudamatsu's No.2 Tandem Cold Mill show good performance of the new control system.
The purpose of this study is to apply the variable damping impedance control to semi-active system using the homogeneous ER (Electro-rheorogical) fluid. A homogeneous ER fluid is constituted by liquid crystal or polymer liquid crystal, and it can change the apparent viscosity under a Newtonian fluid by applying the electric field. Then, when the fluid is applied for device of the machine system, the system can be used as a variable viscous damper. However, these systems have a lot of parameter variations or nonlinear elements. Therefore, some feedback compensations are necessary for these systems to keep up more precisely viscosity. In this paper, we apply the force-based damping control to the homogeneous ER clutch in order to use the characteristics of the fluid enough. We apply the damping control based on the force control to keep up more precisely viscosity. The result of our experiment clearly has shown that the viscosity of the clutch is more certainly controlled by the force-based impedance control.
The load variation of the electro-hydraulic servosystem causes degradation of the control characteristic. This is because the flow characteristic of the flow control valve depends on the load condition. Here, we propose the flow calculation formula to have continues flow between turbulent and laminar flow so that compose the linear plant model with a scheduling parameter. Then, design gain scheduled controllers for the velocity and hydraulic force control.
The locus type forcefree control is proposed for position input type articulated robot arm. The tip of the robot arm moves according to an objective locus by an induced exerted force as if it is operated under a condition of no gravity and no friction. Contouring work of position input type articulated robot arm is, therefore, carried out by using forcefree control with flexibility. Effectiveness of the locus type forcefree control was guaranteed by simulation and experimental work on a two-degree-of-freedom articulated robot arm, and possible applications of locus type forcefree control were also discussed.
In order to evaluate magnetic saturation at sub-transient and transient states of a large-sized salient-pole synchronous machine, the currents and leakage inductances after sudden three-phase short circuits are ana-lyzed by a two-dimensional non-linear transient finite element method (FEM). The currents are calculated both by direct and indirect methods. The direct method uses the FEM and considers fluctuation of the magnetic saturation after the short circuit. The indirect method solves the Park's differential equations without the fluctuation. Results of the direct method agree well with measurements. When the pre-short voltage is large, fluctuation of the leakage inductances after the short is large and it greatly affects values of the short-circuit currents. As the pre-short voltage becomes large, the damper leakage inductances become saturated at first, then the field leakage inductances and finally the armature leakage inductances. Although the indirect method considers saturation at the pre-short condition, it gives inaccurate results and they are nearly the same as the results by the linear FEM. In general, it is thought that saturation of the leakage flux should be considered where sub-transient conditions with large disturbance are analyzed.
In this paper, linear inverted pendulum mode is applied for the trajectory planning of biped robot in order to plan a trajectory in real time. If large disturbance occurs to robot, the robot will not counter the disturbance but plan a new trajectory follows the dynamics of pendulum. The relationship between the stepping point and the trajectory will be figured out and the method which compensate disturbances by controlling the stepping point will be suggested. The stability of walking will be approved by setting a virtual potential energy and a kinematic energy. The stability domain will be shown and it will also be shown how far can the robot get disturbances in the locomotion. The validity of the suggested method will be shown by simulations.