Masaki Izutsu

Wide-bandwidth bilateral control using two stage actuator systems: Evaluation results of a prototype

This paper proposes a two stage actuator system that consists of a coarse actuator driven by a ball screw with an AC motor (the first stage) and a fine actuator driven by a voice coil motor (the second stage). The proposed actuators are applied to make a wide-bandwidth bilateral control system. The first stage has a wide moving range with a narrow control bandwidth, and the second stage has a narrow moving range with a wide control bandwidth. In the proposed method, by consolidate these two inexpensive actuators based on a control design to separate bandwidth, a wide bandwidth bilateral control system can be constructed. Simulation results show that a higher transparency, i.e., better force and position responses between a master and slave, is achieved by using the proposed system compared with a narrow-bandwidth case using a single ball screw system. Furthermore, a prototype of the two stage actuator has been developed and basic performance was evaluated by experiment. Experimental results showed that a light mechanical impedance with a mass of 10 g and damping of 1.6 N/(m/s) that is an important factor to establish good haptic devices was successfully implemented.

Swinging-up and stabilization control based on natural frequency for pendulum systems

This paper proposes a swinging-up and stabilization method for inverted pendulums based on a pendulum oscillation model. A normalized oscillation model is derived by using only one model parameter, i.e., the natural frequency of a pendulum. As a control strategy, energy-based control with a normalized energy model is utilized for the swinging-up from the pendant position. For the stabilization of the pendulum at the upright position, variable structure system (VSS) type adaptive control is designed through the linearized oscillation model. Validity of the proposed method has been confirmed by simulation of an inverted pendulum on a cart. Swinging-up and stabilization control was realized by using only the natural frequency of the pendulum, and the proposed method was also confirmed to be robust against parameter perturbation for the natural frequency. Stability of the designed controller was proven for a given condition that angular velocity of the pendulum has an upper bound.

Estimation Method of Clothes Size for Virtual Fitting Room with Kinect Sensor

We present a estimation method of the dress size for a virtual fitting room(VFR). The VFR is system which user try clothes on, in virtual space constructed computer graphics The conventional VFR displayed 2D model of a clothes as users body. The aim of research is to develop new VRF with Kinect sensors such that 3D model of a cloth track users body on a real time. In order to show a suitable clothes, the suitable size of user should be estimated from camera images. The proposed VFR system is used several Kinect sensors to realize high accuracy of estimation and tacking. This paper gives a estimation method of dress size using Kinect sensor. The proposed method is verified by comparison of single Kinect sensor case with two Kinect sensors. As a result, the estimation accuracy of two Kinect sensors case is higher than single case.

A yoyo trick realized by parallel-link manipulator

This study aims to realize a yo-yo trick by a robot. Yoyo tricks are highly-skilled human motions. In this paper, we tries to realize a yo-yo trick called “Long-Sleeper” by a manipulator. The manipulator has parallel link mechanism. To realize the long-sleeper, the yo-yo and the manipulator models are derived and a controller letting the manipulator track a desired trajectory. The effectiveness of the proposed model and the controller are verified through numerical simulations and experimentations. As a result, the long-Sleeper is realized by the manipulator.

Simultaneous swinging-up and stabilization of double furuta pendulums

Double Furuta pendulums, we named, has a structure that two rotational inverted pendulums are placed at both ends of a single driving arm. This paper presents a swinging-up and stabilization of double Furuta pendulums. As a control strategy, energy-based control design is utilized for swinging up from the pendant positions. Optimal control or nonlinear optimal control with SDRE (state-dependent Riccati equation) is used for stabilization of the pendulums at the upright positions. Simulation results show that the proposed design is successfully applied to the control of double Furuta pendulums.

Design of control method to rotate pendulum

In the control of a pendulum, the stabilization at the upright position has been aimed. This paper proposes an angle-based control method to rotate the pendulum and to stabilize the base link. The rotational control system is designed to let the pendulum track the rotation of a reference pendulum. And the stabilization of the base link is designed by the state-dependent Riccati equation (SDRE) based on zero-dynamics of the pendulum. The simulation result shows the effectiveness

Design of a model following stabilizer to an artificial gravity control model

This paper proposes a new control design named model-following (MF) stabilizer. We present its design through the control of Furuta pendulum. The design steps are : (1) the artificial gravity control is applied to stabilize the pendulum model: (2) by using this stabilized model as the reference model, the model-following servo control system is designed which pays the attention mainly to state-variables having actuation (base-link angle): (3) the non-actuated state variables (pendulum-link angle) are stabilized to follow the behaviors of the stabilized pendulum model. In simulation, the satisfactory performance can be obtained in the swinging-up and stabilization of Furuta pendulum.

Swing-up and stabilization control of twin furuta pendulums by energy control

This paper gives a realization of a swinging up and stabilizing control for a twin furuta pendulums. The twin furuta pendulums has two inverted pendulums which placed at direct drive motor. A control method is a switching of stabilization control and swing-up control. A LQ optimal control is used for stabilization of the pendulums in the neighborhood of upright positions. The effectiveness of the energy control was showed by experimental result. Then, we analyze that the two pendulums simultaneous go to the neighborhood of upright positions. Further, the mechanical structure is evaluated based on the natural angular frequency of each pendulum length and the condition number of controllability matrix of the linearized twin furuta pendulums.

Stabilization of Triple Furuta pendulum by sliding mode control

In this paper, author present a system which named Triple Furuta pendulum. This system has three pendulums which placed at direct drive motor. Author aim at a realizetion of a stabilization of a Triple Furuta pendulum. For the stabilizing control, author derived the equation of motion by the Eular-Lagrange method and a state equation. Author show structural evaluation based on the condition number of controllability matrix and design of present system. Since there are three pendulums, each link would be affected by disturbance. And therefore a simulation of stabilizing control by sliding mode control with high robustness.

Control system design for robot arms playing inside-loop yoyo trick

This study aims to realize a dexterous yoyo trick called “inside-loop” by a robot. In the inside-loop, a yoyo is thrown in an arc from the bottom to the front, passed between the arm and the body, accelerated by quick twisting of the wrist and thrown again to the front. Therefore, the yoyo loops around the hand. To realize this trick, the yoyo model including pulling the yoyo up by taking up the slack string, which is similar to the real behavior, is derived. A reference of a position of the hand is decided by simulations patterned on a human motion, and a controller solves discrete-time optimal control problems every control period. These are verified through numerical simulations. As a result, the inside-loop is realized by the robot.