Masashi Yamashita

Application of H ∞ control to active suspension systems

In this paper, an experimental vehicle with an active suspension system is regarded as a control object. First, a full-vehicle model representing this experimental vehicle was derived, then a control system was designed for this model using the H∞ control theory. The main purpose of this control system is to achieve robust performance. This control theory has been implemented in an experimental vehicle, and evaluated for robust performance in a four-wheel shaker and during actual driving. It has been confirmed that the desired robust performance is achieved in this closed-loop system.

Robust H/sup /spl infin//-output feedback control of decoupled automobile active suspension systems

H/sup /spl infin//-output feedback control is applied to the control of automobile active suspensions based on a dynamic model of the full vehicle. The output feedback control is desirable from the viewpoint of implementation in the sense that it reduces the number of measurements drastically compared with state feedback used currently in suspension control. In this paper, the authors show that a linearized model can be block-decoupled by a similarity transformation, which reduces the controller complexity significantly. The uncertainties of the vehicle model are properly taken into account in the derivation of the H/sup /spl infin// controller. The controller is actually implemented in a commercial car, and the performance is evaluated both by simulations and experiments. The performance obtained proves to be quite satisfactory.

H/sub infinity / control of an automotive active suspension

A quarter-car model of a hydraulic active suspension system is considered. This model has been constructed as an actual size test bed. A new controller design method based on H/sub infinity / control theory is proposed. Simulation and experimental results show that the controllers significantly attenuate the body acceleration gain of the closed-loop system in the range of human acceleration sensitivity. The controllers are also robust against changes of the body mass and system damping.<<ETX>>

Robust H/sup /spl infin// output feedback control of decoupled automobile active suspension systems

Robust H/sup /spl infin// output feedback control is applied to the control of automobile active suspensions based on a full dynamic model of the vehicle. The output feedback control is desirable from the viewpoint of implementation in the sense that it reduces the number of measurements drastically compared with state feedback used currently in suspension control. In this paper, the authors show that a linearized model is block-decoupled by a similarity transformation, which reduces the controller complexity significantly. The uncertainties of the vehicle model are properly taken into account in the derivation of the H/sup /spl infin// controller. The controller is actually implemented in a commercial car and the performance is verified both by simulations and experiments. The performance obtained proves to be quite satisfactory.<<ETX>>

Artificial balancer - Supporting device for postural reflex

The evolutionarily novel ability to keep ones body upright while standing or walking, the human balance, deteriorates in old age or can be compromised after accidents or brain surgeries. With the aged society, age related balance problems are on the rise. Persons with balance problems are more likely to fall during their everyday life routines. Especially in elderly, falls can lead to bone fractures making the patient bedridden, weakening the body and making it more prone to other diseases. Health care expenses for a fall patient are often very high. There is a great deal of research being done on exoskeletons and power assists. However, these technologies concentrate mainly on the amplifications of human muscle power while balance has to be provided by the human themself. Our research has been focused on supporting human balance in harmony with the humans own posture control mechanisms such as postural reflexes. This paper proposes an artificial balancer that supports human balance through acceleration of a flywheel attached to the body. Appropriate correcting torques are generated through our device based on the measurements of body deflections. We have carried out experiments with test persons standing on a platform subject to lateral perturbations and ambulatory experiments while walking on a balance beam. These experiments have demonstrated the effectiveness of our device in supporting balance and the possibility of enhancing balance-keeping capability in human beings through the application of external torque.

Application of H∞ Control to Active Suspension Systems

Abstract In this paper, an experimental vehicle with an active suspension system is regarded as a control object. First, the full-vehicle model representing this experimental vehicle was derived, and the control system was designed for this model using H ∞ control theory. The main purpose of this control is to achieve a robust performance. This control law has been implemented in an experimental vehicle, and evaluated for robust performance in running and shaking experiments. It has been confirmed that the desired robust performance as designed is achieved in this closed-loop system.

Continuing education for applying control theory to automobiles at Toyota

Abstract Since 1990, the Toyota Motor Corporation has been conducting internal education programs on control technology for its engineers, using the MATLAB and inverted pendulum experimental devices. With three years of experience, some major complaints were voiced concerning these programs, such as “not practical”, or “not helpful to understand the basic theory of control”. As countermeasures for these problems, SIMULINK has been introduced as a new tool for constructing models easily. “One-year Project” has also been started which enables the participants to solve the problems they face in their daily work with the help of university researchers and Toyotas experts.

A mathematical model of type 1 diabetes involving leptin effects on glucose metabolism

Leptin, a hormone released from fat cells in adipose tissues, was recently found to be capable of normalizing glucose metabolism in animals. Clinical data on patients with lipodystrophy indicates that leptin may have a positive effect on glucose metabolism in individuals with diabetes. There are growing expectations that leptin can improve the current insulin treatment for patients with type 1 diabetes. We investigated this possibility through in silico experiments based on a mathematical model of diabetes, which is currently the only mode of research that eliminates human risk. A model of the brain-centered glucoregulatory system, in which leptin plays a central role, was constructed and integrated within a conventional model of insulin/glucose dynamics. The model has been validated using experimental data from animal studies. The in silico combination experiments showed excellent therapeutic performance over insulin monotherapy.

APPLYING CONTROL THEORY TO CONTINUING EDUCATION FOR AUTOMOBILES AT TOYOTA

Since 1990, Toyota Motor Corporation has been conducting internal education programs of control technology for our engineers, using the MATLAB and inverted pendulum experimental devices. With our three years of experience, we have heard some major complaints concerning these programs, such as “not practical”, or “not helpful to understand the basic theory of control”. As countermeasures for these problems, we have introduced the SIMULINK as a new tool for constructing models easily, and also started “One-year Project” which enables the participants to solve the problems they face in their daily work with the help of university researchers and Toyotas experts.