This paper investigates a method through which a human-size humanoid robot can fall over backwards safely. Squatting-extending motion of legs reduce impact of falling and shock-absorbing parts of the robot keep the force at a permissible range. The robot could stand up itself again after falling.
Recently, Passive-Dynamic-Walking (PDW) has attracted much attention in the research of biped walking robots. In this paper, we provide a new control method of Quasi-PDW. Quasi-PDW means that a robot usually does PDW without any input torques, and the actuators of the robot are used just only when the walking begins or disturbances come in. The first feature of the control method is that (k-1) -th trajectory of the walking robot is used as a reference trajectory of the k-th step. The second feature is that a kind of gain scheduled PD control is adopted and its gains are regulated depending on the state of the contact phase of swing leg. As a result, it is expected that the robot will continue walking and the gait of the robot will shift from an active walking to PDW. The effectiveness of the control method is shown through several simulations and experiments with real walking robot“Quartet-Ill”.
In this paper, we focused on the degrees-of-freedom for robot foot mechanisms. To realize the functions of humanlike locomotion on biped robots, we should know the fundamental aspects of human foot mechanisms through intensive observations of human locomotion. We proposed a novel mechanical shoe with a 2-DOF toe part. Two toe-plates of the toe part move independently and they are able to constrain human foot in various ways. Wearing the mechanical shoes, three subjects were asked to walk in straight, zigzag and slalom courses. We measured their walking speed, toe joint angles and center-of-pressure on their feet. Through these observations, we show that a biped robot with our proposed toe mechanism could potentially walk faster than the conventional ones.
This paper presents a multi-fingered haptic interface opposed to human hand, which consists of 6 DOF interface arm and three-haptic fingers with 3 DOF. The haptic interface is demanded to be safe, to work in wide operation space, and to present not only force at contact points but also weight feeling of virtual objects, to have no oppressive feeling when it is attached to humans, and to have no weight feeling of itself. The haptic interface was designed to be completely safe and to be similar to the human upper limb in shape and motion ability. The interface is placed opposed to the human hand, which brings safety and no oppressive feeling, but causes difficulty in controlling the haptic interface because it should follow the hand poses of the operator. Two control methods of the haptic fingers are tested and two approaches to oppose the interface hand to the human hand are studied. A computer graphics simulation and experiments are also presented.
This paper presents a method of momentum compensation around the perpendicular axis of the stance foot during the fast dynamic walk of humanoid robots. In order to perform a task using the arms during a walk, it is desirable that the upper body part, i.e., the arms and the trunk, should not be used for the momentum compensation and should be dedicated to achieving a task. Moreover, a particular walk called a trunk-twistless walk is investigated by experientially observing the pelvic rotation of contact sport athletes. From these observations, an antiphase rotation of the pelvis against the swing leg is observed when compared to the normal walk of a human. This antiphase characteristic of the pelvic rotation is implemented to a humanoid. A method of determining the rotation of the humanoid's waist is proposed in conjunction with the pitch angle of the swing legs. The proposed walk achieves a whole walking motion including momentum compensation only by the lower body. The stance foot torque around the perpendicular axis is reduced in the proposed walk compared to a standard humanoid walk without twisting the trunk or swinging the arms. Improvements to the straightness of the walking trajectory and the stability of the upper body during a fast dynamic walk are also confirmed.
Though Monte Carlo localization is a popular method for mobile robot localization, it requires a method for recovery of large estimation error in itself. In this paper, a recovery method, which is named an expansion resetting method, is newly proposed. The combination of the expansion resetting method and the sensor resetting method, which is a typical resetting method, is also proposed. We then compared our methods and others in a simulated RoboCup environment. Typical accidents for mobile robots were produced in the simulator during trials. We could verify that the expansion resetting method was effective for recovery from small irregular changes of a robot's pose, and that the combination method could deal with both large and small irregular changes.
In this paper we propose a new compact 6-DOF haptic interface. It contains a five-bar spatial parallel mechanism for orientation, placed on a modified Delta parallel-link mechanism. This serial connection of the two parallel mechanisms yields a wide workspace. In addition, the structure also ensures fast motion, high-power motion and compactness. Furthermore, the mechanisms are free of singularities, which also contributes to the wide workspace. The haptic interface includes a small 6-axis force/torque sensor and high-reduction geared motors to realize good sensitivity and compactness. In addition, the stiffness of the modified Delta mechanism is also discussed.
The manipulation ability of robotic fingers is too less than the human's ability. One of the reasons is that the sensing ability of the robotic finger is too poor. Tactile sensing is useful for obtaining the information about the object and contact conditions. To improve the manipulation ability of robotic fingers, this paper proposes a design of an anthropomorphic soft fingertip with distributed tactile receptors. The fingertip consists of two silicon rubber layers of different hardness containing two kinds of receptors, strain gauges and PVDF (polyvinylidene fluoride) films. The structure of the fingertip is similar to that of a human's; it consists of a bone, an inner, an outer layer, and randomly distributed receptors inside. Experimental results demonstrate the sensing ability of the fingertip: it can discriminate five different materials by pushing and rubbing the objects.
Force information in virtual space is important and often required for tele-operation, training, amusement, design supporting and other virtual reality systems. While conventional force displays are active systems with actuators and as such may become inherently dangerous, passive force displays which use only passive elements are effective methods for assuring safety. However, passive type systems have some directions and link postures which are hard to present force. To this problem, a method for improvement of controllability using redundant couple of brakes was suggested. It can be considered this method makes possible to display various force directions and various postures of virtual objects. The purpose of this study is, for further improvement of controllability of systems with redundant couple of brakes, design and development of more generalized redundant mechanism by adding another element of design freedom. Moreover, improvement of force display-ability by reducing equivalent inertia is also aimed. In this paper, the developed system is outlined and basic experiments with it discussed.
This paper describes a distance measurement device for 3-dimensional indoor positioning system under the daily-life environment. By considering penetration for objects and tolerance for noises, we adopted to measure time-of-flight of spread spectrum (SS) radio at 2.4 [GHz] frequency. Since the velocity of the radio wave is about 3×108 [m/s], we utilized a high precision time measurement LSI for measuring the round-trip time of the radio wave between the measurement point and the reference point. The experimental results showed that the proportionality relation between the round-trip time and the distance was observed. By setting up three reference points in the room, 3-dimensional position measurement experiment was performed. The error of 3-dimensional position which was calculated by using the measured three distances was about 0.36 [m] . It was also confirmed that the distances could be measured if obstacles like woods or acrylic boards existed between the measured point and the reference point.