Humanoid robots that mimic human movement have garnered significant attention in recent years. This study focuses on mimicking the efficient pitching motion of humans by incorporating two main approaches into a humanoid robot: (1) the use of elastic elements to assist joint torque, and (2) the optimization of motor torque to minimize energy consumption. This robot is intended to emulate human physical characteristics, such as mass, link length, and center of gravity, with a particular focus on utilizing the elastic energy generated during shoulder internal and external rotation. A leaf spring is attached in parallel with the motor at the shoulder pitch joint to release the elastic energy stored during shoulder external rotation, thereby assisting internal rotation in a manner similar to human biomechanics. Additionally, motor torque optimization is addressed by formulating the torque minimization problem as a combinatorial optimization challenge and solving it using Fujitsu's quantum-inspired Digital Annealer. Experiments conducted through simulations and with an actual pitching robot assessed the effectiveness of these technologies in mimicking human-like pitching motion. The results suggest that combining elastic elements with motion optimization techniques enable robots to achieve more efficient human-like movements.

Teleoperating bipedal humanoid robots presents unique challenges, including decreased stability and reduced operator presence. This paper addresses these challenges by proposing a method that leverages the operator’s inherent sense of stability by feedback from a sole haptics display to operate a bipedal humanoid robot. We developed a bilateral control system that integrates a device replicating sole haptics feedback and provides the operator with feedback on changes in the robot’s center of gravity. We conducted operating experiments in the forward-backward direction to evaluate its effectiveness and investigate the effectiveness of sole haptics on robot operation. The results demonstrate that operating with both vision and sole haptics feedback significantly reduces the robot’s fall rate by over 56% when disturbances are applied, compared to using only vision feedback. Moreover, operators reported a 21% higher sense of presence with both vision and sole haptics feedback compared to using only vision feedback.

Compared to traditional agricultural environments, the high density and diversity of vegetation layouts in Synecoculture farms present significant challenges in locating and harvesting occluded fruits and pedicels (cutting points). To address this challenge, this study proposes a Mask R-CNN-based method for locating fruits (tomatoes, yellow bell peppers, etc.) and estimating the pedicels from RGBD images acquired by a camera moved along fixed paths. After obtaining masks of all fruits and pedicels, this method judges the matching relationship between the located fruit and pedicel according to the 3D distance between the fruit and pedicel. Subsequently, this research determines the least occluded best viewpoint for harvesting based on the visible real areas of located fruits in images acquired under the fixed paths, and harvesting is then completed from this best viewpoint following a straight path. Experimental results show this method effectively identifies occluded targets and their cutting positions in both Gazebo simulation environments and real-world farms. This method can select the least occluded viewpoint for a high harvesting success rate.

In recent years, awareness of improving the quality of medical care has increased. We focused on neonatal resuscitation, which is difficult to train clinically, and our long-term goal is a neonatal resuscitation training system that can simulate cases and can feedback interactively based on quantitative evaluation of the procedures. In this study, we developed the neonatal simulator that has a respiratory movement simulating mechanism and a chest compression measurement mechanism. Through an interview with neonatologists, the fidelity of respiratory movements and the possibility of evaluating chest compression with the developed simulator were assessed.

Biped robots require massive power on each leg while walking, hopping, and running. We have developed a flow-based control system-called hydraulic direct drive system- that can achieve high output while avoiding spatial limitations. To implement the proposed system with simple equipment configuration, a pump and single-rod cylinder are connected in a closed loop. However, because compensation for flow rate is impossible in a completely closed loop, owing to the difference in the pressure receiving area caused by the rod, a passive flow compensation valve is employed. This valve has a simple structure and is easy to implement. Further, an additional sensor is required to detect the open/close state because the valve state will cause an error in flow control. Therefore, we implemented a model in the controller to predict the state of the flow compensation valve and formulated a method of switching from flow control to pressure control according to the predicted state. Experimental results indicate that the error of the joint angle is reduced to less than 1.6 degrees for walking patterns, and stable walking is realized when the system is installed in biped humanoid robots.

Human jumping involves not only lower limbs but also whole-body coordination. During jumping, the effect of sinking the center of mass for recoil and arm swing are significant, and they can cause changes in the jump height. However, upper body movements during jumping movements of humanoid robots have not been studied adequately. When jumping involves only the lower limbs, the burden on the lower limbs increases and it is difficult to jump as high as humans do. Also, if the sole is in contact with the ground during jumping movements, we cannot make good use of the ankle joint. Humans raise their heels during jumping movements, but there are few cases where humanoid robots achieve these movements. Therefore, we thought that jumping with recoil motion by the sinking, arm swing, and changing in foot contact status could result in a higher jump height higher than that possible with only lower limb movements. Hence, in this study, we generated jumping motion using sinking, arm swing and changing foot posture. First, a center of mass trajectory was generated by planning the entire jumping motion, and at the same time, the angular momentum was determined for stability. Next, the joint trajectory was calculated using these two parameters. At that time, arm trajectory and foot posture were specified in the null space. This generated a jumping motion considering arm swing. During simulations, this method provided a jump height almost four times the jump height that obtained without arm swing.

Biped robots require substantial amounts of power alternately on each leg while walking, hopping, and running. However, it is difficult to mount high-power large electrical motors in conventional mechanical transmission systems owing to spatial limitations. A hydraulic direct-drive system is proposed in which the size of the motor in each leg can be reduced by sharing the motor outputs between the legs. In this paper, the hydraulic direct-drive system is evaluated in an actual hydraulic system. Velocity followability, excellent energy saving, and virtually perfect position tracking are achieved with the proposed system. The results of performance comparison with a valve-based control system show that energy consumption is controlled and good position-following capability is achieved using the proposed system.

Biped robots require substantial amounts of power on each leg alternately while walking, hopping, and running. However, it is difficult to adopt large high-power electrical motors in conventional mechanical transmission systems owing to spatial limitations. To address this problem, a hydraulic interlocking drive system that incorporates two hydraulic direct-drive systems is proposed for biped humanoid robots. The hydraulic interlocking drive system connects the two hydraulic direct-drive systems and concentrates the pump output on one side cylinder. The other side cylinder meter-in flow rate is controlled by the meter-out flow rate from the cylinder on which the pump is concentrated. Good position tracking and excellent energy saving are achieved with the proposed system. A performance comparison with a single hydraulic direct-drive system shows that the motor power of the hip pitch joint is reduced by 27.3% for walking patterns. This result shows that the rated output of the motor can be reduced, and smaller and lighter motors can be installed in biped robots.

To improve the movement ability of humanoid robots, instead of traditional methods dependent on only power of actuators, there is possibility that utilizing elasticity inspired from collaboration of muscle and tendon of human is effective to achieve high-power movement. In this study, we aimed to realize a jumping motion that accumulates energy more appropriately in spring by combining active joint driving with spring behavior like human tendons and muscles. We proposed a countermovement jump method using the resonance with the leg's active pushing-off movement and leg stiffness. To achieve active pushing-off and joint stiffness, we developed a new joint mechanism using leaf springs and an actuator unit with a worm gear. We then performed experiments to evaluate the effectiveness of the proposed mechanism and methods. Finally, the robot achieved a countermovement jump using active kicking and leg's elasticity.

Humans utilize their torsos and arms while running to compensate for the angular momentum generated by the lower-body movement during the flight phase. To enable this capability in a humanoid robot, the robot should have human-like mass, a center of mass position, and inertial moment of each link. To mimic this characteristic, we developed an angular momentum control method using a humanoid upper body based on human motion. In this method, the angular momentum generated by the movement of the humanoid lower body is calculated, and the torso and arm motions are calculated to compensate for the angular momentum of the lower body. We additionally developed the humanoid upper-body mechanism that mimics the human link length and mass property by using carbon fiber reinforced plastic and a symmetric structure. As a result, the developed humanoid robot could generate almost the same angular momentum as that of human through human-like running motion. Furthermore, when suspended in midair, the humanoid robot produced the angular momentum compensation in the yaw direction.

Analysis of human running has revealed that the motion of the human leg can be modeled by a compression spring because the leg's joints behave like a torsion spring in the stance phase. Moreover, the knee bends rapidly to avoid contact of the foot with the ground in the swing phase. In this paper, we describe the development of a knee joint mechanism that mimics the elastic characteristics of the stance leg and rapid bending knee of the idling leg of a running human. The knee was equipped with a mechanism comprising two leaf springs and a worm gear for adjusting the joint stiffness and high-speed bending knee. Using this mechanism, we were able to achieve joint stiffness within the range of human knee joints that could be adjusted by varying the effective length of one of the leaf springs. In addition, the mechanism was able to bend rapidly by changing the angle between the two leaf springs. The equation proposed for calculating the joint stiffness considers the difference between the position of the fixed point of the leaf spring and the position of the rotational center of the joint. We evaluated the performance of the adjustable joint stiffness and the effectiveness of the proposed equation for joint stiffness and high-speed knee bending. We were able to make a bipedal robot hop using pelvic oscillation for storing energy produced by the resonance to leg elasticity and confirmed the mechanism could produce large torque 210 Nm.

Human running motion can be modeled using a spring-loaded inverted pendulum (SLIP), where the linear-spring-like motion of the standing leg is produced by the joint stiffness of the knee and ankle. To use running speed control in the SLIP model, we should only decide the landing placement of the leg. However, for using running speed control with a multi-joint leg, we should also decide the joint angle and joint stiffness of the standing leg because these affect the direction of the ground reaction force. In this study, we develop a running control method for a human-like multi-joint leg. To achieve a running motion, we developed a running control method including pelvis oscillation control for attaining jumping power with the joint stiffness of the leg and running speed control by changing the landing placement of the leg. For using running speed control, we estimated the ground reaction force using the equation of motion and detected the joint angles of the leg for directing the ground reaction force toward the center of mass. To evaluate the proposed control methods, we compared the estimated ground reaction force with the force measured by the real robot. Moreover, we performed a running experiment with the developed running robot. By using ground reaction force estimation, this robot could accomplish the running motion with pelvic oscillation for attaining jumping power and running speed control.

This paper describes the bipedal humanoid robot that makes human laugh with its whole body expression and affect human's psychological state. In order to realize "Social interaction" between human and robot, the robot has to affect human's psychological state actively. We focused on "laugh" because it can be thought as a typical example for researching "Social interaction". Looking through a Japanese comedy style called "manzai" or the art of conversation, we picked out several methods for making human laugh. Then we made several skits with the advice of comedians, and made the whole body humanoid robot perform them. Results of experimental evaluation with these skits shows that the robot's behavior made subjects laugh and change their psychological state seen as a decrease of "Depression" and "Anger".

Human running motion can be modeled by a spring loaded inverted pendulum (SLIP). However, this model, despite being widely used in robotics, does not include human-like pelvic motion. In this study, we show that the pelvis actually contributes to the increase in jumping force and absorption of landing impact, both of which findings can be used to improve running robots. On the basis of the analysis of human running motion, we propose a new model named SLIP2(spring loaded inverted pendulum using pelvis). This model is composed of a body mass, a pelvis, and leg springs; the model can control its springs during running by use of pelvic movement in the frontal plane. To achieve hopping and running motions, we developed pelvis oscillation control, running velocity control, and stabilization control using an upper body, as control methods. We also developed a new hopping robot using the SLIP2model. To evaluate the proposed model and control methods, we performed hopping and running simulations. The simulation results showed that the SLIP2model successfully achieves hopping and running motions. The hopping robot was also able to accomplish hopping motion. The simulation results also showed that the difference between the pelvic rotational phase and the phase of oscillation of the mass vertical displacement affects the jumping force. In particular, the results revealed that the human-like pelvic rotation contributes to the absorption of landing impact and to the increase in takeoff forces, which validates our observations in human motion analysis.

This paper describes the implementation in a walking humanoid robot of a mental model, allowing the dynamical change of the emotional state of the robot based on external stimuli; the emotional state affects the robot decisions and behavior, and it is expressed with both facial and whole-body patterns. The mental model is applied to KOBIAN-R, a 65-DoFs whole body humanoid robot designed for human-robot interaction and emotion expression. To evaluate the importance of the proposed system in the framework of human-robot interaction and communication, we conducted a survey by showing videos of the robot behaviors to a group of 30 subjects. The results show that the integration of dynamical emotion expression and locomotion makes the humanoid robot more appealing to humans, as it is perceived as more “favorable” and “useful”, and less “robot-like".

This paper describes the development of a new shank mechanism and mimicking the human-like walking in the horizontal and frontal plane. One of human walking characteristics is that the COM (Center Of Mass) motion in the lateral direction is as small as 30 mm. We assume that it is thanks to the human walking characteristics in the horizontal plane that the step width is as narrow as 90 mm and the foot rotation angle is 12 deg. To mimic these characteristics, we developed a new shank and implemented it in a humanoid robot WABIAN-2RIII. It has a parallel mechanism which mimics the shank's size of human. Thanks to its size almost the same as human's the robot is capable of realizing gait with the narrow step width of 90 mm and the foot rotation angle of 12 deg. We evaluated the performance of the shank using WABIAN-2RIII. The robot could realize stepping in place with lateral displacement of CoM within 34 mm, which is almost as small as that of human.

This paper describes a walking stabilization control based on gait analysis for a biped humanoid robot. We have developed a human-like foot mechanism mimicking the medial longitudinal arch to clarify the function of the foot arch structure. To evaluate the arch function through walking experiments using a robot, a walking stabilization control should also be designed based on gait analysis. Physiologists suggest the ankle, hip and stepping strategies, but these strategies are proposed by measuring human beings who are not “walking” but “standing” against force disturbances. Therefore, first we conducted gait analysis in this study, and we modeled human walking strategy enough to be implemented on humanoid robots. We obtained following two findings from gait analysis: i) a foot-landing point exists on the line joining the stance leg and the projected point of CoM on the ground, and ii) the distance between steps is modified to keep mechanical energy at the landing within a certain value. A walking stabilization control is designed based on the gait analysis. Verification of the proposed control is conducted through experiments with a human-sized humanoid robot WABIAN-2R. The experimental videos are supplemented.

This paper describes the development of a new expressive robotic head for the bipedal humanoid robot. Facial expressions of our old robotic head have low facial expression recognition rate and in order to improve it we asked amateur cartoonists to create computer graphics (CG) images. To realize such expressions found in the CGs, the new head was provided with 24-DoFs and facial color. We designed compact mechanisms that fit into the head, which dimensions are based on average adult Japanese female size. We conducted a survey with pictures and videos to evaluate the expression ability. Results showed that facial expression recognition rates for the 6 basic emotions are increased compared to the old KOBIAN's head.

In the multipath mobile channel, the received signal is affected by both flat fading and selective fading. Using an adaptive array is an effective method to compensate for selective fading, whereas a diversity antenna is good at compensating for flat fading. In this paper, a switching adaptive/diversity antenna is presented and examined with computer simulation. For evaluating the signal whose quality falls repeatedly within a short duration, the probability of DUR (desired to undesired signal ratio) below a given value is adopted. The computer simulation results show that the proposed switching adaptive/diversity antenna can compensate for both flat fading and selective fading.