In this paper, we propose a wearable sensor system that measures an angle of elbow and tapped position by using bone-conducted sound. A novelty of this paper is to use active sensing for measuring the angle of an elbow. Active sensing means to emit sounds to a bone, and a microphone receives the sounds reflected at the elbow. Our system consists of two microphones and a speaker, and they are attached on forearm. The reflection of sound depends on the angle of elbow. Frequencies of bone-conducted sound by tapping and from the speaker are different. Consequently these measurements can be used simultaneously, even though two sounds share the same bone to transmit. Additionally, we implemented two prototype systems such as master-slave interface and menu-based interface as wearable robot interfaces. We confirmed that the robot could be controlled using proposed system through experiments.
Variety of Wearable Walking Assistant Robots (W2ARs) are appearing on the market. Their safety attracts the interest of manufacturers as well as the users. In this paper, we address risk assessments and clarify the typical risks of W2ARs. We also discuss practical safety measures for the risks. The strength testing machines are proposed and produced to verify the inherent safety measures: the mechanical angle stoppers and appropriate assembling. This paper will aid the industrialization of W2ARs.
This paper proposes an active air mattress to improve affinity of an upper limb support system. The affinity is developed by several items. An easiness of an attaching and releasing process of the support system contributes to a short-term affinity. Comfortableness and sense of belonging during wear belongs to a long-term affinity. Both are very important in addition to support functions of the system. The active air mattress installed in a forearm part of the support system actively holds a human forearm quickly and firmly, and then changes the contacting areas with a human skin in order to maintain adequate blood circulation around the contacting area. Exhaust air from air chambers is reused to ventilate around a forearm skin. It is evaluated through some experiments from viewpoint of pressure distribution, blood flow, wearing time, releasing time, body-holding rigidity, temperature and humidity of a human skin.
This study aims to develop a man-machine interface which realizes the perfect tracking to human motions. With such an interface, a user may operate machines with improved maneuvering feel. The perfect tracking can be realized by utilizing Zero Phase Error Tracking Control (ZPETC) to eliminate or reduce phase lags including mechanical and communication delays in systems. In general, ZPETC however requires future information as reference signals. We propose to utilize a time difference from arising electromyogram (EMG) signals in muscles until appearing the corresponding actual human motion. The time difference is called Electro Mechanical Delay (EMD). Hence, if human motions can be estimated from electromyogram signals, we can obtain the future information on the human motions by EMD. Our system focuses on wrist motion as commands toward a system. Utilizing EMD, the wrist angle is estimated from EMG signals by a nonlinear delayed ARX (NDARX) model. A discrete-time Model Following (MF) controller is used for letting the system track the wrist motion. Consequently, this demonstrates the possibility that the controlled system can move tracking the wrist motion with no or less lag with respect to the practical human motion. Friction compensation plays an important role from the implementation point of view, because ZPETC is a feedforward controller for discrete-time linear systems but the real system is affected by friction. The effectiveness is verified through numerical simulations and experiments comparing tracking performance using only a PID controller with the proposed control system in terms of cross-correlation analysis.
Home oxygen therapy (HOT) is a medical treatment for patients suffering from severe lung diseases. Although a walk in an outdoor environment is recommended for the patients to keep physical strength, patients always have to carry a portable oxygen supplier which is not sufficiently light weight for the patients. Our ultimate goal is to develop a mobile robot carrying an oxygen tank and follows a foregoing patient in an urban outdoor environment. We have proposed a mobile robot with a tether interface to detect the relative position of the foregoing patient. In this paper, we improve mobile platform mechanisms and active wheels to maximize the negotiating step height, and to allocate sufficient luggage area in the main body carrying an actual oxygen tank. The following control algorithm is also improved and demonstrate its effectiveness in an outdoor following experiment.
In this paper, we focus on a control technique which has been proposed in the field of intelligent transportation systems, ITS, for vehicle platooning. This control technique, termed adaptive cruise control (ACC), is basically used for coordination of multiple mobile robots. In order for robots to move more efficiently in congested systems with bottlenecks, a robot behavior control and environmental rule proposed by the authors are appended to ACC and applied to robots. However, a robot is required to acquire position and velocity information of all the robots in the moving direction. In terms of communication, therefore we propose a simple method for organizing clusters among the preceding and following robots. Unlike the two approaches above, this method requires position and velocity information of only adjacent robots. In the simulation experiment, a limitation of ACC in congested systems with bottlenecks is shown by comparing to a result of ACC with the behavior control and environmental rule. Moreover, these results are compared to results of ACC with the clustering method. As a result, the effectiveness of the behavior control and environmental rule in conjunction with ACC is shown. And finally, the superiority of the ACC and clustering method compared to the behavior control and environmental rule for the efficient coordination is shown.
A new technique to make a precise position control of air-cylinder using an electric motor to rotate a piston is proposed. By rotating a piston, the friction of cylinder and piston becomes significantly small, which is about 40% in starting and 60% in continuous moving of those without a rotation. The control method is basically a PD high-gain feedback, but with dead-zone near zero to make a standstill positioning stably quiet. A motor is controlled to produce a minimum but enough rotation according to an axial trip of piston, where the rotation is activated a bit earlier than a valve opening. With these proposed techniques, an experimental device achieves 0.2[mm] deviation in ramp motion, series of 0.02[mm] step motion. The device is stable under a load of 25% of theoretical maximum output force. The hardness of position control is 50 times larger than a simple valve closed stopping. In these experiments, a power consumption of the motor is relatively small, which is about 2% of cylinder output.
Fault detection functions of a robotic manipulator are very useful for factory automation. All production has the possibility to fail due to unexpected accidents. To reduce the fatigue of human workers, small errors automatically should be corrected by a robot system. In this paper, an external thread fastening task by a robotic manipulator is investigated. To discriminate the four states of a task, linear support vector machine methods with two feature parameters are introduced. One is the estimated insertion length, and the other is the maximum reaction force. The effectiveness of the proposed algorithm is confirmed through an experiment and recognition examination.
A modeling method to represent bending/torsional deformation of an electric wire is proposed based on the differential geometry. A twisted wire called a robot cable is used in a prismatic/rotational joint of an industrial robot to transmit signals or electric power. It is composed of a twisted bunch of several strands of many copper wires. The copper wire may be cracked by repeated bending/torsional deformation associated with the movement of a joint and such crack leads to wiring disconnection. To predict the life-cycle of the wires and to prevent such wiring disconnection, it is required to estimate deformation of not only the strands but also the copper wires when the wire is bent/twisted. In this paper, the deformed shape of a wire, which corresponds to a twisted bunch of n strands, is described by 3+2n independent variables and can be derived by minimizing the potential energy of each strand under various constraints. As the relationship between copper wires and their strand is similar with that between strands and their twisted bunch, the deformed shape of each copper wire can be also derived with the same method.