Hidetaka Morimitsu

A method to control a peltier device based on heat disturbance observer

Peltier device is a thermoelectric element which can generate a heat transfer. The device is considered a suitable tool for transmission of thermal sensation recently, because it has a relatively fast response among thermal devices. To transmit the thermal sensation, temperature control of the device is thought to be important. However, several elements such as joule heat, parameter identification error, or heat flow from an outside object disturb the control. Moreover, it is also important for the transmission of the sensation to design a systems tracking performance, while ensuring its robustness. To tackle these problems, this research proposes a robust temperature control system based on a heat disturbance observer. The proposed observer uses the structure of a disturbance observer, which is mainly used in the field of motion control. By using the observer, disturbance of the thermal system is compensated. In addition, it is possible to design the tracking performance and the characteristic of disturbance suppression independently. The validity of the proposed method is confirmed by experimental results.

Frequency response analysis of observer-based thermal control system of peltier device

Peltier device is considered as a suitable instrument to produce heat transfer, and many methods which present thermal sensation have been proposed in the field of haptics. The bandwidth of thermal control may help a performance investigation of presenting thermal sensation. However, conventional research mainly conducts discrimination experiments of materials, and focuses relatively little on the characteristic analysis of the thermal system. In addition, when the device is driven, nonlinear terms of the device characteristic such as Joule heat is generated, and those make the bandwidth analysis difficult. On the other hand, the author has proposed observer-based temperature and heat inflow control system in the past, in which the nonlinear terms are compensated. This research uses the control systems and measures those frequency responses. The responses are compared with theoretical transfer functions which are derived by block diagrams of control systems. Experimental results show some correspondence with theoretical models, which are expected to be used for analysis of presenting thermal sensation in the future.

Sensorless Control of Heat Inflow to a Thermal Display Using a Heat Inflow Observer

The acquisition of information on heat inflow is essential to the control of thermal displays and the rendering of thermal sensations. This paper addresses a method of estimating the amount of heat inflow without using a heat flow sensor and demonstrates sensorless heat inflow control using a Peltier device, which is often employed as a thermal device in thermal displays. Moreover, this paper introduces a method of identifying the thermal contact resistance of the device needed for the proposed observer. The observer estimates heat inflow by using information on electrical currents and temperatures. By using the observer instead of a heat flow sensor, which generally has a larger thermal capacity than a temperature sensor, an improvement in the response of a thermal device is expected. The applicability of the proposal is tested by experiments.

Design of force compensator with variable gain for bilateral control system under time delay

This study deals with a bilateral control system under communication delay. Control structure is designed to be symmetric among master and slave devices in proposed system, in order to realize the same performance as much as possible even though master and slave side is replaced. Then, this research aims to improve the performance of position tracking in free motion and aims to ensure zero steady state errors of both position and force control in contact motion. The time delay is compensated at force controller section and its gain is varied according to the force responses of master and slave motors. By the proposed method, haptic communication with enhanced performance under communication delay is expected. The validity of proposal is shown by experimental results.

Thermal bilateral control for reproduction of thermal contact between remote places

Haptic sense has recently been getting attention as the third multimedia information in the communication engineering, and this research focuses on the transmission of thermal sensation which is one of the components of the tactile sensation. For the transmission of the sensation, this research utilizes Peltier device as a thermal actuator. Then, the temperature and heat flow of master and slave system are simultaneously controlled to reproduce the thermal admittance of objects on the systems mutually. In the control system, some observers are constructed for compensation of control system or information obtainment on heat flowing into the system. By using the constructed system, it becomes possible to realize the state that the objects on the systems exchange heat as if these were directly contacted. The validity of the proposed system is shown by experimental results.

Multilateral control-based motion copying system for haptic training

This paper proposes a new motion-loading method that utilizes a multilateral control-based scheme for the motion-copying system. The motion-copying system refers to human operators motion, tracks and preserves it only for being able to reproduce the same result of the motion. Conventionally, only slave system was used for motion-loading phase. The method proposed in this paper offers a way to enable more than one slave side actuator at the phase. With the proposed system, the operator at loading phase can grab the master system which the manipulator was holding at the saving phase. The performance analyses of proposed system are made with the bode plots, and the experiments are held with two degrees-of-freedom actuators. The newly proposed haptic informational reproduction technique can be applied in many areas, especially as the training purposes.

Thermal bilateral control with scaled thermal information using peltier device

This research focuses on a thermal bilateral control system with scaled thermal information. Considering that the phenomena of heat transfer that occur between contacted objects depend on thermal admittance of each object, this research mentions the effect of scaling on the admittance rendered at the operator side. By changing the structure of temperature and heat flow controller, it becomes possible to alter the sensitivity of remote thermal system against external environment. The thermal control itself is conducted by using two kinds of observers which compensate for the disturbance heat flows and estimate the amount of heat flowing into the system. Experimental results show the validity of proposed control system.

Circle theorem-based realization of nonlinear force control for teleoperation under time delay

The communication delay is one of the major problems existing in the bilateral teleoperation system since it largely degrades the performance. This study treats the acceleration-based bilateral control (ABC) as a basic controller. According to the analyses, it is shown that a trade-off between the operationality and the reproduction performance of the kinesthetic contact exists in designing the ABC under time delay. For addressing this, adjustment of the force control gain according to the situations of the bilateral control is proposed. For ensuring the stability of the system with the nonlinear controller, circle theorem is applied to the proposed system. Experimental results show that the proposed system can realize stable operation as well as the improved performance over the bilateral control system with constant gain.

Reproduction of 2-DOF motion adapting to environmental angle change

Recently, technology which deals with tactile sense has attracted attention in various fields. In particular, researches about storing and reproducing human motion are one of important fields for the haptic technology. A motion-copying system is known as one of efficient methods to achieve storing and reproducing human motion. However, it is known that environmental condition change is serious problem for the motion-copying system. To resolve this problem, many methods have been proposed. However, most of them are not sufficient because these methods deal with only 1-DOF motion and they are for adapting only environmental position change. In this paper, a reproduction method adapting environmental angle change is proposed using 2-DOF system. Validity of the proposed method is confirmed by experiment. By the proposed method, adaptivity of the motion-copying system is improved.

A design of four-channel bilateral control system under time delay based on hybrid parameters

This research proposes a stabilizing method of bilateral control system under communication delay. Hybrid parameters of bilateral control are focused in design, then position and force controller are modified to eliminate the time-delay element or at least to remove the adverse effect of the element in some parameters important for stability. The developed system keeps the symmetric property of control structure that realizes the performance of force rendering and stability which are independent of manipulating side. The validity of proposed system will be shown by experiments.