Sumiko Majima

Modeling of shape memory alloy actuator and tracking control system with the model

There has been great demand for shape memory alloy (SMA) actuators within the field of micro-machines. However, the thermomechanical behavior of SMA actuators is too complicated to accurately predict their response. Moreover the tracking control accuracy of SMA actuators is limited due to the inherent hysteresis nonlinearity. The paper presents a model of an SMA actuator for use in mechanical design and a control system for compensating the hysteresis. First, the model based on constitutive laws developed by Brinson et al. (1996) and our proposed hysteresis model is demonstrated. Next, we propose a control system composed of a proportional integral derivative (PID) feedback loop and a feedforward loop. In the feedforward loop, the desired control input corresponding to the desired displacement is obtained from a static SMA model derived by modifying the classic Preisach hysteresis model. We also propose a method for identifying parameters of the hysteresis model. This methods demands only measurement of the major loop. Application of the control system to our developed SMA actuator shows that the tracking control performance is improved.

A control system to compensate the hysteresis by Preisach model on SMA actuator

Hysteresis phenomena often degrade system performance such as giving rise to undesirable inaccuracy. Shape Memory Alloy (SMA) actuators are chosen as an example of a plant with hysteresis and a control system to compensate the hysteresis is proposed in this paper. Firstly, a model which represents the temperature hysteretic property of SMA and its inverse model are designed. Secondly, a controller is proposed to compensate the hysteretic property by using the inverse model. Lastly, this method is applied to control the electrical resistance of SMA, which reflects its state, and the usefulness of the controller is confirmed experimentally.

A Design of a Control Method for Changing Yaw Direction of an Underacuatted Unicycle Robot

We have developed a unicycle robot that consists of a body, a disk driven by a DC motor for rotation, and a wheel driven by another DC motor to move the body. Since there is no direct force for changing the yaw direction of the robot, conventional controllers cannot change the yaw direction. The present paper proposes a control method for changing the yaw direction by using the interaction between individual motions in the yaw, pitch, and roll directions. Simulation results show the performances of the proposed controller. 1) The proposed control method is useful for a regulator problem and can control the yaw direction of the unicycle robot toward zero from any initial value. 2) The controller can cancel a disturbance applied to the robot motion

Mapping schemes of the particle-in-cell method implemented on the PAX computer

Abstract The particle-in-cell (PIC) model refers to the motion of many particles driven by a force that results in part from the field that they themselves generate. An example of the PIC model, an electrostatic electron plasma model, was processed by the parallel computer PAX. The potential field was solved by applying a Fast Fourier Transform to the Poisson equation. The workload in particle pushing was allocated by the Eulerian method (or present-address method) and the Lagrangian method (or birthplace method). Two schemes for the space mapping—direct and modular mappings—were also tested. It was demonstrated that modular mapping can overcome the efficiency degradation, which was observed in the direct mapping of the nonuniform particle distribution. The performance scaling law, a general expression for the execution time, and efficiency are given. Based on the scaling law, the performance is extended to a larger machine.

Tracking control method for an underactuated unicycle robot using an equilibrium state

We have developed an underactuated unicycle robot consisting of a body, a disk rotated by a DC motor, and a wheel driven by another DC motor to move the body. There is no direct force for changing the yaw direction of the robot. In the present paper, we propose a tracking control method for the unicycle robot by analogy with a rolling coin. In the absence of an external force, a rolling coin follows a circular trajectory. Similarly, the unicycle robot has an equilibrium state. First, the equation of equilibrium state of the robot is derived. This equation reveals that the yaw rate depends on the roll angle and the wheel angular velocity. Simulation results reveal the validity of the derived equation. Next, the desired tangential velocity and the angular velocity of the robot for tracking a target trajectory are derived by Kanayamas method; and then the derived values are converted into the desired roll angle and the desired wheel velocity by using the derived equation of equilibrium state. Control inputs are set to control the roll angle and the wheel velocity to the converted desired values. Finally, the control method is applied to a control for tracking a circular orbit.

Real-time optimization control for parking a vehicle automatically

The automatic operation technology of vehicles is of considerable practical concern. In this paper, we apply a real-time optimization technique to a control system for parking a vehicle automatically. In the technique the efficiency of the control system depends on weight matrices of a cost function; we propose a method for changing the weight matrices in order to realize a switching operation. This switching operation is a kind of parking motion in which a vehicle goes forward to a target at first, and then turns to the right or the left; it then approaches the target again with backward motion. This operation is often necessary in a narrow space. Simulation results show that suitable selections of a cost function and its weight matrices accomplish the switching operation without determining the switching point beforehand.

Monte Carlo simulation of a spin model on the parallel computer “PAX”

Abstract A Monte Carlo simulation of the two-dimensional O (3) Heisenberg model with nearest neighbour interaction has been performed by the “PAX-128”, a parallel array type computer, with 128 processing units, which was constructed for a wide range of scientific calculations. The measured efficiency of parallel processing was 88%. A performance prediction has been made for a future PAX computer with a very large number of processors.

A RECEDING HORIZON CONTROL FOR LIFTING PING-PONG BALL

Abstract This paper proposes a control system for lifting a ping-pong ball without the use of a camera. The system measures the time of collision between a plate and a ball with a microphone. The control system must then be able to direct both the position and the velocity of a motor for each subsequent collision, even if the model contains uncertainty or modeling errors. To achieve this objective, an optimal control is modified using receding horizon control. The effectiveness of the proposed control method is verified by performing simulations on the lifting system.

Design method for a controller of a distance learning calligraphy system via public networks

By using a distance learning calligraphy system, a student can learn calligraphy skills as if in the presence of a teacher. In order to develop such a system, we adopt a master-slave system via public networks and propose a design method for its controller. This method satisfies the following two requirements: a) the stability of the system can be guaranteed for any transmission delay due to the public network, and b) the master controller can be designed independently of the slave controller. The validity of the proposed design method is confirmed by simulation results. Experimental results indicate the performance of the distance learning calligraphy system developed using the controllers designed via the proposed method.

Just-in-time control method for a free-joint manipulator

The present paper proposes a just-in-time (JIT) control method for a free-joint manipulator moving in a horizontal plane. The manipulator consists of two links, where only the first link at the base is driven and the second link has a passive joint. Although it is difficult to control the manipulator by conventional methods, a human can operate the manipulator at a certain level. The input of a human operator is observed and is regarded as a rectangular signal. The control input is then represented in terms of the parameters of the rectangular signal. The database for the proposed JIT control system is constructed using these input parameters. Experimental and simulation results reveal that, by using the proposed control method, both of these links successfully reach the target angles. However, the control method is only useful when the target angle for the free link is relatively small. The simulation results reveal that the performance of the control method depends on the target angle and on the parameters of the manipulator. The reason for this dependency is discussed based on the distribution of the database. The discussion suggests that the performance may be improved by modifying the database such that data will be distributed throughout the range of the target position.