Kenzo Wada

Application of time-delay-control in variable structure motion control systems

A new simple sliding mode controller for the motion control systems is proposed to avoid the problems related to chattering. The proposed control is based on the time delay estimation used in the time-delay-control (TDC) method. By introducing the concept of time delay estimation into the sliding mode control, the difficulty of the stability analysis of TDC may be resolved. It has been shown that the switching component of the proposed control is not determined by the magnitude of the systems uncertainty but by its change during specified time delay. That leads to much smaller magnitude of the switching component in comparison with other sliding mode controllers. For the proposed control scheme the sliding mode reaching and existence conditions for a class of systems like a robotic manipulator are presented. The experimental examples are shown to confirm the validity of the proposed controller.

Sliding mode control based on the time delay estimation

In this paper, a new adaptive type sliding mode controller is presented to avoid the problem of the chattering and the excessive switching gain. The proposed control is based on the time delay estimation used in the time delay control (TDC) presented by Youcef-Toumi (1990, 1992). The sufficient condition for satisfying the reaching condition is presented by the application of Lyapunov direct method. The proposed control can be realized with a sufficiently low switching gain. The numerical examples are shown to confirm the validity of the proposed controller.

Analysis on the manual control characteristics of the human pilot during the operation of the powered wheelchair

The electrically powered wheelchair (EPW) is now recognized to be an indispensable tool for people with motor disabilities. However, using EPW in daily life might be a cause of danger because of the poor maneuverability of some commercially available EPW products. In order to ease the manipulating sensitivity and produce a pleasant and secure EPW, a model representing the operators control ability while using the EPW is necessary when designing an embedded controller. This paper proposes a model which describes the control characteristics of the human operator while she/he is using an EPW. The proposed model is constructed based on, and coincides with, the pilot model which represents the control capability of the human operator while doing her/his accustomed tasks. The model should be called the error model of the EPW, control because it contains two errors to be stabilized for pleasant and secure operation of the EPW. In addition, the proposed model is an enhanced version of the pilot model in the sense that the effects of the environmental changes acting on the pilot are taken into account. Experimental results show the validity of the error model and indicate that an inappropriately designed EPW controller strictly deteriorates the manual control performance. The results obtained will serve as a good basis for the design of the EPW controller.

Application of the fuzzy control method for level control of a hopper

If a change of state in a process can be grasped visually using an image processing unit and the process can be controlled, it then becomes one of the advantages of the system. This is because the image processing unit can be used as a detecting element when a physical quantity in a process cannot be measured directly. However, generally, vagueness inevitably accompanies the data because the image is visual data. Thus, control methods that make the best use of the advantage of image processing have been investigated. First, the change of state in a process is detected from the image data. Fuzzy control is performed on the basis of the data to control the level of granules inside a hopper. Using the triangular type membership functions the effects of the shape of these functions, the magnitude of gains and the fuzzy reasoning methods related to the response of the process are examined. Good process responses were obtained by applying the fuzzy control method.

Sliding modes in electrical machines control systems

A sliding mode control (SMC) of DC and AC electrical machines is presented. The cascade structure of the controller is selected with sliding mode in the inner loop. The outer loop is aimed to derive a reference current such that the controlled machine exhibits the desired transients. Position and speed control are discussed. The estimation of the switching function from the position (or speed) and control input is presented. The results of the simulation and the tests are presented.<<ETX>>

Chattering free sliding modes in robotic manipulators control

Sliding mode control (SMC) of a system which is linear with respect to control and its application to robotic manipulator control system design is presented. The controller is designed to provide sliding mode motion on selected manifolds in the state space. These manifolds are selected as a linear combination of the state coordinates. This selection allows the formulation of the path tracking control, force control, and impedance control problems to be very similar. The control is selected to satisfy selected Lyapunov function and stability criteria.

Sliding mode control with estimated equivalent control for MIMO affine nonlinear systems

A new adaptive type sliding mode controller is presented to avoid the problem of the chattering and the excessive switching gain proportional to the upper bounds of system uncertainty in the application of sliding mode control. The proposed control is composed of linear feedback control and feedforward control which is constructed from an estimated equivalent control. The estimated equivalent control is obtained from an estimation system which uses a neural networks most powerful ability, that is, function approximation. The reaching condition is assured by the application of Lyapunov design method. The numerical examples are shown to confirm the validity of the proposed controller.

Attempts on the Performance Improvement of the Manual Auditory Feedback Control Systems

It has been pointed out in several foregoing literatures that the well known properties of the human pilot observed in the manual visual feedback control system can also be observed in the manual auditory feedback control system. However, performance of the manual auditory feedback control usually tends to degrade as compared to the visual feedback case. In this paper, some experimental attempts to improve the maneuverability of the manual auditory feedback control system are presented. Several differently configured auditory displays and the use of phase lead compensator are proposed and evaluated using the artificial manual auditory feedback tracking control system. Experimental result indicates that performance improvement can be achieved to some extent; however, the effectiveness of the applied auditory devices and/or lead compensator largely depend on the plant characteristics

Optimal Control of Grinding System.

In this report, an optimal control of the closed circuit grinding system in a cement process is discussed. Generally, it is known that there is an optimum circulating load at which the efficiency of comminution is maximum. However, as control variables, the amount of electricity consumption of a bucket elevator is used instead of the circulating load for measuring reasons in this experiment. As the control system, a combination control system of fuzzy control and LQI control is constructed. The inside situation of a mill is inferred by fuzzy reasoning and the reference value of the sound level of the mill is determined on the basis of reasoning results. Then the supply of clinker to the mill is adjusted by LQI control such that the mill sound level follows to reference level. As a result, it is found that the proposed control system is very applicable and good control performance is obtained.

Control of AC Electrical Machines: A Sliding Mode Approach

Abstract The VSS approach to motion control system design gives an unified algorithm for AC machines (induction and synchronous) control systems. It will be shown that the same control algorithm can be applied for speed and position control. The sliding mode closed-loop PWM for supply converter control is applied. The chattering is eliminated due to the appropriate selection of the control. The sliding mode motion on the selected manifold in the state space is guarantied and all salient properties of the systems with sliding modes are preserved.