An alternative method for the quantitative assessment of energy consumption during level walk and stair walk using body-mounted sensor is discussed since the calorie counters commercially available scarcely estimate the energy consumption during ascending.Energy consumption is calculated by the metabolic model developed using the oxygen consumption during various walk including stair walk. The metabolic model is formulated as the time lag element of first order and its input is the energy requirement defined as the polynomial of horizontal and ver-tical walking velocity (2D walking velocity). The 2D walking velocity is derived by the integration of horizontal and vertical accelerations measured by a 3D pedometer attached on subject's tiptoe. The 3D pedometer consists of three accelerometers and three ceramic gyroscopes and estimates three dimensional displacement of the tiptoe during walk. The relation between 2D walking velocity and oxygen uptake is investigated to develop the energy requirement model. The energy requirement model developed in this study agrees with the measured oxygen uptake during 2D walking with the correlation coefficient of 0.93. Moreover time constant of the metabolic model is determined from the time trajectory of the oxygen uptake during walking exercise with constant velocity. The experiments including level walk, ascending and descending are performed for ten subjects and show that the energy consumption during ascending estimated using the 3D pedometer increases exceedingly compared with that during the level walk. Furthermore the estimated energy consumption highly correlates with the oxygen uptake with the correlation coefficient of 0.91 on average. The quantitative assessment of energy consumption of 2D walk by proposed method is confirmed.
This paper proposes a new method of chain tension fault detection for escalators. This method can detect the loose tension in the chain automatically using an accelerometer attached to the handrail without overhauling the escalator, which is effective for maintenance. First, the transitional pattern of the handrail vibration when starting up the escalator in the reverse direction was studied. The first pattern involves the vibration generated by starting up the upper sprocket, and the second pattern involves the vibration generated by starting up the handrail. When tension of the chain is loose, the time delay between the first pattern and the second pattern, called the “start up delay time”, is increased. Therefore, the loose tension of the chain can be detected by the start up delay time. Based on these characteristics, this paper proposes a method of detecting the start up delay time automatically using signal processing techniques. A chain fault detection system was produced, and system tests were conducted to evaluate the performance for several loose tension conditions using real escalators. The test results showed that the start up delay time increased in proportion to the looseness of the chain tension. Therefore, it is possible to detect chain tension faults using the proposed method.
Non-destructive inspection of buried pipes is usually made with an electromagnetic wave (radar). But, the concrete inspection is usually made by human eyes, that is, made based on the B-mode image of the reflected wave signals. Consequently, the inspection has been of very low reliablity and accuracy. The present paper proposes a novel inspection system of high accuracy and reliability which measures the cover (i.e., depth) and diameter of buried pipes. The system makes use of the signal propagation model, which one of the authors developed previously. The proposed system is shown to be applicable to both the metal and non-metal pipes in any medium. Lastly, the effectiveness of the inspection system is demonstrated by experiments.
In this paper, a data-driven model-free design method of PID controller is proposed for a SISO linear timeinvariant plant. A problem setting for loop shaping is given where the integral gain of the PID controller is maximized under the maximum sensitivity constraint. This optimization problem is reduced to a linear programming problem whose constraint can be calculated from the input-output response data of the plant based on unfalsified control concept without assuming any mathematical model. In order to avoid many experiments to obtain many response data, a method of generating fictitious data by applying the wavelet transform to a single response data is given. Our design method does not require complicated iterations for plant identification, performance index refinement, and controller design.
In this paper, we show the effectiveness of our proposed adaptive H∞ contro l method for the positioning mechanism which is widely used in the manufacturing field. In general, positioning mechanism is composed by a servo motor, coupling, ball-screw, and table. But unfortunately, we can not identify the characteristics of coupling and ball-screw, in precisely. It is very serious problem for the precision positioning control of table. If we assume that the unknown characteristics of coupling and ball-screw are input uncertainty for the table, then our proposed adaptive controller is effective to compensate for such an uncertainty. Experimental results are given to show the usefulness of our proposed method in the sense of practical applications.
The controllability and the observability of linear uncertain systems are investigated here. The systems under consideration contain time-invariant uncertain parameters, which may take arbitrarily large values. In this case, the locations of uncertain elements in the system matrices play an important role. It is shown that a linear uncertain system is controllability and observability invariant if and only if the system has a particular geometric configuration called a complete generalized antisymmetric stepwise configuration (CGASC), which includes GASC defined by Wei1.
This paper deals with consensus problem for multi-agent systems and its application to vehicle formation control. Consensus means to reach an agreement regarding a certain quantity of interest that depends on the states of all agents, We consider that stability condition of consensus for MIMO linear systems. The stability condition is derived via Lyapunov stability theorem. Then, an observer-based output consensus strategy is proposed to reduce communication exchange and an output consensus strategy with an integrator is also derived. Finally, one of these consensus strategies is applied to vehicle formation problem. Experimental results of vehicle formation are shown and the effectiveness of the proposed approaches is evaluated.
This paper introduces stochastic port-Hamiltonian systems and clarifies some of their properties. Stochastic port-Hamiltonian systems are extension of port-Hamiltonian systems which are used to express various deterministic passive systems. Some properties such as passivity of port-Hamiltonian systems do not generally hold for the stochastic port-Hamiltonian systems. Firstly, we show the necessary and sufficient condition to preserve the stochastic Hamiltonian structure of the original system under time-invariant coordinate transformations. Secondly, we derive the condition to maintain stochastic passivity of the system. Finally, we introduce stochastic generalized canonical transformations and propose a stabilization method based on stochastic passivity.
Balance between human body compositions, e.g. bones, muscles, and fat, is one of the major and basic indicators related to personal health. Body composition analysis using ultrasound imaging has been developed rapidly. However, interpretation of ultrasound images is conducted manually, and accuracy and confidence in interpretation requires experience. This paper proposes an automated approach to determine boundaries between tissues, with which thickness of subcutaneous fat and muscles can be obtained. A portable B-mode ultrasound echographic device was used in this study. The proposed automated discrimination method utilizes statistical characteristics of anatomy, intensity and shape information about fat and muscle tissues and bone to determine boundaries. Furthermore, the proposed method was developed considering real-time and high-speed implementation and reduction of computational cost. Validity of the proposed method was evaluated in nine subjects (one woman, eight men; ages 22-59 yr) at three anatomical sites. Experimental results show that the proposed method can discriminate the thickness with high accuracy. Finally, a sensitivity analysis of discrimination error to changes in parameters of the proposed method was carried out.
Recently, maritime works, such as ocean observation or cable laying works, become efficient with the dynamic positioning control of the vessels. The conventional PID control is still useful but the performance is not enough for precise positioning or multiple waypoints tracking. In this paper, we present the application of real-time nonlinear Receding Horizon control for route tracking problem and control allocation problem for vessels equipped with azimuth thrusters. The performance and usefulness of the proposed method is verified with the actual cable laying works.
Although it was shown in our previous paper that canonical periodic decomposition with the same period of a given linear periodic continuous-time system is invalid in general, it is shown here that decomposition with the double period is valid without any exception.
Control performance of vibration suppression system using the internal model principle deteriorates when control inputs are saturated. This paper describes a method that accurately estimates periodic disturbances when the inputs are saturated under the condition that the control object is known.