Kazuyuki Kamimura

Stability Analysis on Air Conditioning System

Room air temperature control of a single zone space is studied. In air conditioning systems, no matter what the forcing-a step or impulse in setpoint or slight disturbance-the loop can easily get into huntings. Variable air volume (VAV) control is very common for air distribution in air conditioning system today. The supply air flowrates to the room can be controlled by damper or by fan speed control. Such a VAV system is assumed to be essentially to the source of huntings. To explore the possible existence of huntings, a dynamical system model is formulated as a bilinear model with time-delayed feedback (by P or PI control actions), and a parametric analysis of the stability region is presented. Results are given showing the stability region affected by the selection of setpoint values and control parameters. This analysis is conducted to help us tune the PID controllers for achieving good control performance

Dynamical Characteristics of Gyroscopic Weight Measuring Device

This paper describes analytical and experimental studies about an entirely new system for measuring forces using a gyroscope (called Gyroscopic Weight Measuring Device, or simply GWMD throughout this paper) which provides precise direct digital output proportional to the single axis weight applied. In spite of the complexity of the servo-mechanism, the action of the GWMD is inherently linear, hysteresis, and drift free. Topics in this paper are summarized as follows: 1) The principal dynamical characteristics of the GWMD using a two-degree-of-freedom mathematical modelfor a gyroscope are an) alyzed theoretically. 2) The GWMD is designed with suitable parameters and constructed. Some systematic errors caused by various influences are examined. 3) Performance tests are promising for practical applications. The GWMD constructed in this study offers a repeatable accuracy up to 1/15,000 for weight in the range 0 to 150 N.

Stability analysis of interacting systems in air-conditioning system

Interacting systems between room air temperature of a single zone space and supply air temperature controls are considered. In air conditioning systems, the control loop can easily get into huntings. Variable air volume (VAV) control is very common for air distribution in air conditioning system today. Such interactions are assumed to be essentially to the source of huntings. To explore the possible existence of huntings, dynamical system models of the interacting systems are formulated as a bilinear model with time-delayed feedback, and a parametric analysis of the stability region is presented. Results are given showing the stability region affected by the selection of setpoint values and control parameters. This analysis is conducted to help us tune the PID controllers for achieving good control performance.

Air-Conditioning PID Control System with Adjustable Reset to Offset Thermal Loads Upsets

The heating, ventilating, and air-conditioning (HVAC) systems have huge different characteristics in control engineering from chemical and steel processes. One of the characteristics is that the equilibrium point (or the operating point) usually varies with disturbances such as outdoor temperature (or weather conditions) and thermal loads. The variations of the operating point intend to vary parameters of a plant model. Thus, the HVAC control systems are extremely difficult to obtain an exact mathematical model (Kasahara 2000). Proportional-plus-integral (PI) controllers have been by far the most common control strategy as the complexity of the control problem increased (Astrom 1995). Today, a variable air volume (VAV) system has been universally accepted as means of achieving energy efficient and comfortable building environment. While the VAV control strategies provide a high quality environment for building occupants, the VAV system analysis rarely receives the attention it deserves. As a result, basic control strategies for the VAV system have remained unchanged up to now (Hartman 2003). In addition, applying the model predictive control method to the HVAC systems, the control performance has been highly improved by pursuing the deviation from the operating point (Taira 2004). According to this report, recognizing the deviation from the operating point and calculating the optimal control inputs about the newly obtained operating point on next sampling time, the control system gives better responses than the traditional feedback control system. Motivated by these considerations in these reports, we consider the room temperature and humidity controls using the adjustable resets which compensate for thermal loads upsets. One of the primary objectives of the HVAC systems is to maintain the room air temperature and humidity at the setpoint values to a high quality environment for building occupants. The room temperature and humidity control systems may be represented in the same blockdiagram form as single-variable, single-loop feedback control systems because this interaction is weak relative to the desired control performance.

Analysis of a gyroscopic force measuring system in three-dimensional space

Abstract This paper concerns the development of an entirely new sensor for measuring forces using a gyroscope (called gyroscopic force measuring system, or simply GFMS) for measuring a force vectorially. In a previous paper [S. Kurosu, M. Adachi, K. Kamimura, Dynamical characteristics of gyroscopic weight measuring device, ASME J. Dynamic System Measurement, and Control 119 (1997) 346–350], the dynamics of the GFMS for measuring a vertical force were investigated and the principal characteristics were examined theoretically and experimentally. The results of this work are directly applicable to measurement of a vectorial force in three-dimensional space. The principle and the dynamical characteristics of the GFMS for measuring a force vector are analyzed theoretically. To measure a force vectorially, two auxiliary turntables (driven by servomechanisms) are installed around the gyroscope, in which turntable outputs are required to follow some angles of incidence of a force vector. Some unfavorable errors caused by various factors and disturbances are analyzed. Two types of compensation methods are proposed as a device both for accurate force measurement and disturbance suppression. The feasibility of the proposed GFMS is confirmed by numerical simulations.

Compensation of manual reset to offset thermal loads change for air-conditioning system

PI controllers have been commonly used in air-conditioning systems. Among PID controllers, the D action is frequently switched off for the simple reason that it is difficult to tune properly. In some situations, it is possible to estimate thermal loads (or disturbances) before they will enter the plant. It is then natural to offset the thermal loads before they affect the control output. A typical example is a certain system for air-conditioned space in which an outdoor thermometer detects sudden weather changes and the occupant roughly anticipates the thermal loads changes. Disturbances can be offset by the compensation of the manual reset. This control strategy can be called a variety of feed-forward. The objective of this paper is to introduce the compensation strategy of the manual reset for air-conditioning systems and to compare this strategy with a traditional PI control strategy. Simulation results obtained from representative thermal loads are presented to demonstrate that PD control based on the compensation method leads to more stable operation in comparison to the traditional PI control.

Force-measurement using gyroscopic force measuring system

This paper deals with the development of an entirely new force sensor, called the gyroscopic force measuring system (GFMS), for measuring a force vectorially. In this paper, the GFMS is constructed by a gyro-rotor using a miniature rate-gyro for aircraft instrument. The fundamental experiment suggests the possibility to measure a small force range less than 0-3N.

A tuning method for PID controller using optimization subject to constraints on derivatives of control input

This paper concerns a tuning method for PID controller using optimization subject to constraints on derivatives of control input. To evaluate the control performance, the responses to load disturbance and reference input changes are presented compared to those by the partial model matching method. Moreover, it is found that the PID controller tuned by this optimization technique is somewhat robust and effective enough for practical applications.

Application of H/sub /spl infin// compensator to a first-order lag plus deadtime system with parameter variations

This paper concerns a design method of an H/sub /spl infin// compensator which achieves robust stability as well as adequate disturbance rejection and reference tracking performance. A practical and systematic design method for the H/sub /spl infin// compensator is proposed. This paper demonstrates a practical applicability of the H/sub /spl infin// compensator to a typical plant in process industries compared with the control performance obtained by the robust PID controller.