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.

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.

In this paper, a sensitive glove type wearable robot is designed, and its remote-control system is developed for operating a robot hand remotely. By sensing the motions of human fingers through pressure sensors in the glove and sending the information to the robot hand, the robot hand can accurately repeat the motions of users.

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.

This paper describes the easily visible position for deciding action of unknown object grasping without all of predefined knowledge in a real situation. We have proposed a perception system which is composed of an online processable object detection method based on plane detection, and an invariant perceptual information for a grasping action. The object detection method can detect the point data on the object without the predefined knowledge. The invariant detection method for a grasping action is explained by inertia tensor and fuzzy inference. As an experiment, we compare the object extraction result and the invariant perceptual information value through experimentation of the various sensing position and the object pose. We discuss the relationship between the sensing position and the object detection result. Furthermore, we discuss the invariant perceptual information value which can be estimated the easily visible position of the object.

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 discusses the direct perception for grasping and the action for perception using depth sensor. The previous method should recognize the accurate physical parameters to grasp an unknown object. Hence, we propose a sensation based perception which perceives exclusively the relevant information to the behavior of the robot. To perceive an unknown object, we have proposed the plane detection based approach of the SPD-SE. The SPD-SE may have applicability to robot perception at real time, and has advantages that the point group and properties of an unknown object can be extracted at the same time. The sensation of grasping is explained by inertia tensor and fuzzy inference. The sensation of grasping affords the possibility of action to a robot directly without inference from physical information such as size, posture and shape. As experimental results, we show that the robot can detect a relevant information of a grasping behavior directly. And, the sensation of grasping presents own state and environmental state together by one parameter.

We propose an object recognition method for service robots under the constraint of uncertain object teaching by humans. In previous object recognition methods, the training phase required a large number of prepared images and also required the training data to not have a complex background. However, for robots to perform daily tasks, they should be able to recognize objects despite unclear object teaching by humans. In order to mitigate the effect of features in the background on object recognition, our proposed method classifies local features based on saliency from video images. In this paper, we demonstrate the efficacy of the proposed method in recognizing target objects despite unclear teaching by the user.

This paper discusses robot partner interaction based on Frankl's psychology to encourage a person act voluntarily. Recently, elderly people who live alone in a room is increased. But, it is hoped that the elderly people keep good health. To keep good health for elderly people, a person should act voluntarily and get involved in community events. In Frankl's psychology insists that the meaning of life is required from external stimuli. Frankl's psychology is defined 3 fields of value which are provided from external stimuli. A person can be found the meaning of life according to the values getting. Therefore, it is expected that a person would act voluntarily if a person find the meaning and value of life from external stimuli through interacting with a robot partner. In this research, we propose the robot interaction method based on Frankl's psychology. And we propose an external value estimation method based on the fields of value which estimates an external value from environmental change. Through human-robot interaction experiment based on Frankl's psychology, we verify that a human acts voluntarily by finding the external value.

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 discusses a robot partner system for natural communication using emotional models. In our daily life, robot partners should have an emotional model in order to co-exist and to realize natural communication with people. In this paper, we propose several emotional models for human-robot interaction based on computational intelligence. First we discuss the importance of emotion and its functions in the social interaction. Next, we propose an emotional model based on emotion, feeling, and mood. Furthermore, we use the emotional model as a method for communication system, and also, we discuss Frankl's psychology as the basis of communication. Finally, we show several experimental results of the proposed method, and discuss the utterance systems for a robot partner.

In this study we describe a shoes-wearable foot mechanism which mimics human's foot arch structure and the characteristics of the foot skin to examine the effect of the human foot on biped walking. We approximate the arch structure by a rotational spring and model the human's foot skin with compression springs. The mimesis of the foot arch elasticity is realized by using compression springs. Regarding the characteristics of human's foot skin, first we develop a measuring equipment to measure the human's plantar transverse elasticity. We set the target value of the modulus of transverse elasticity of the foot skin to 11.2 N/mm, and we set the modulus of compression elasticity to 0.136 MPa, referring to a relevant study. The characteristics of human's foot skin are mimicked by using a super-soft urethane resin called Hitohada-gel with 8 mm thick. Through evaluation tests we confirmed that the shoes-wearable foot mechanism could mimic well the characteristics of human's foot arch and skin.

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 presents a robot manipulator with collision force suppression mechanism that can passively suppress collision force. The collision suppression mechanism consists of a release air pad, a transmission rack, a clutch gear and a compression spring. An air cushion bag is attached to the exterior of the robot manipulator. If a robot manipulator collides with an object or human when a task is performed, the collision force suppression mechanism disjoints the specific joint corresponding to the direction of the collision force to reduce the collision force. The robot manipulator will then return to the former task when the colliding object is eliminated. Through collision experiments, the effectiveness of the collision force suppression mechanism is verified.

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.

Recently, an intelligent robot is expected to operate our living area. To realize, a robot should make a decision for action from a simple order by human. For decision making of a robot, it is important that a perception of environmental situation and adaptation to the preference of a person. We have proposed the learning method based on bottom-up process using SOM and top-down process using Fuzzy Inference. Through experiments by simulation, we verified that the proposed method can consider the changing of attribution by time variation. And, we discuss about features of the different proposed method through comparing.

This paper describes a walking stabilization control on a soft ground based on gait analysis for a humanoid robot. There are many researches on gait analysis on a hard ground, but few scientists analyze the walking ability of human beings on a soft ground. Therefore, we conducted anthropometric measurement using a motion capture system on a soft ground. By analyzing experimental data, we obtained two findings. The first finding is that although there are no significant differences in step width and step length, step height tends to increase to avoid the collision between the feet and a soft ground. The second finding is that there are no significant differences in the lateral CoM trajectories but the vertical CoM amplitude increases when walking on a soft ground. Based on these findings, we developed a walking stabilization control to stabilize the CoM motion in the lateral direction on a soft ground. Verification of the proposed control is conducted through experiments with a human-sized humanoid robot WABIAN-2R. The experimental videos are supplemented.

The results of the neuroscientific research show that humans tend to stabilize the head orientation during locomotion. In this paper we describe the implementation of inverse kinematics based head stabilization controller on the humanoid platform. The controller uses the IMU feedback and controls neck joints in order to align the head orientation with the global orientation reference. Thanks to the method, we can decouple the orientational motion of the head from the rest of the body. This way stabilized head becomes better platform for proprioceptive sensory apparatus, such as cameras or IMU. In the paper we present three experiments which prove that the method has good performance in damping both, high and low frequency motion of the head. We also prove that the proposed controller improves the stability of the tracked goal point on the image of in-built camera.

This paper describes a fast turning method for a humanoid robot by using slipping motion with both feet. The humanoid robot, WABIAN-2R, has achieved human-like walking with heel contact and toe off motions by using a human-like foot mechanism with a passive toe joint. The human-like foot enables a robot to turn by using slipping motion between the feet and the ground because it can switch ground contact conditions such as heel contact, sole contact and toe contact. To realize a slipping turn, we develop an attitude control. Verification of the proposed method is conducted through experiments with a biped humanoid robot WABIAN-2R. WABIAN-2R realized a quick turn by using slipping motion with both feet. We also confirmed that the energy consumption of a slipping turn is less than that of a stepping turn.

A four degrees of freedom (DoF) waist and trunk mechanism, as well as human-like foot, enable the humanoid robot WABIAN-2R to perform human-like walk with stretched knees, and heel-contact and toe-off gait phases. The inverse kinematics (IK) method, used in the present system, requires specification of not only task space reference trajectories, but also reference trajectories for all redundant DoFs. In this paper, we propose a novel, unified inverse kinematics method significantly simplifying the pattern generation. The method enables generation of the above described gait by specifying only the task space trajectories. We divide the forward locomotion task into subtasks with different priorities and combine them in the single IK equation. We also perform experiments in simulation environment as well as on WABIAN-2R, which prove that the method can be used to calculate IK for human-like gait. The equation evaluated in this paper is applied to the forward locomotion task, however it can be easily modified to perform other tasks on humanoid robots with different kinematic structures.

This paper describes an avoidance behavior from unknown external forces for a biped walking vehicle. To distinguish between external forces from passenger and those from environments, we use the data of a force sensor mounted on foot, and external forces are estimated from ZMP errors. To guarantee a walking stability, the waist position is adjusted to match the measured ZMP to the reference ZMP, and the position of landing foot is adjusted so that the waist trajectory does not diverge. By implementing the developed method on the human-carrying biped robot, the robot realized a stable walk under unknown external forces from environments. When pushing the robot stepping, the robot moved backward and moved away from the generation source of external forces about 400 mm. When pushing the robot walking forward, the robot stopped going forward and prevented from coming closer to the generation source of external forces. We confirmed the effectiveness of the proposed control through these experiments.

We have developed a new biped foot mechanism capable of detecting ground surface to realize stable walking on uneven terrain. The size of the foot mechanism is 160 mm × 277 mm and its weight is 1.5 kg. The foot system consists of four spikes each of which has an optical sensor to detect ground height. The foot makes a support polygon on uneven terrain by using three or four spikes. We have conducted several experiments on the outdoor ground surface that has a slope of 7.0 degrees and a maximum height of 15 mm bumps, and the effectiveness of the foot mechanism is confirmed.

The humanoid robot, WABIAN-2R, has achieved human-like walking with knee-stretched, heel contact and toe off motions by using a foot mechanism with a passive toe joint. However, the foot structure is different from a human's. In this paper, we describe a new foot mechanism capable of mimicking the human's foot arch structure to figure out the function of the arch structure. Especially, the developed foot mimics the elastic properties of the arch of the human's foot and the change of the arch height during walking. The foot mechanism consists of a passive joint in the internal toe, a passive joint in the external toe, and a joint in the foot arch. We conducted several walking experiments by using WABIAN-2R, and the function of the arch structure is clarified quantitatively. As a result, we confirmed that the arch elasticity could absorb a foot-landing force at the plantar contact phase and the change of the arch height contributed to a strong thrust at the push-off phase.

Many researchers have studied on walking stability controls for biped robots. Most of them are highly accurate acceleration controls based on the mechanics model of the robot. However, the control algorithms are difficult to be applied to human-carrying biped robots due to modeling errors. In the previous report, we proposed the landing pattern modification method, but it had a problem that a foot landing impact increased when a walking speed became fast. So, we propose a new terrain-adaptive control that can reduce a landing- impact force. To increase a concave terrain adaptation, we set a target landing position beneath a reference level. To reduce the landing-impact force, we change the position gain control value to a small value at a swing phase. Moreover, we set landing-foot speed at zero after detecting a foot-landing by the force sensor mounted on a foot. To follow uneven terrain, a virtual spring is installed to the vertical direction after detecting a foot-landing on a ground, and a virtual compliance control is applied to the roll and pitch axes. In a stable walk while carrying a 65 kg human on uneven terrain, the new control method decreased the landing-impact force than the previous terrain-adaptive control.

Many control methods have been studied on the assumption that the feet of biped robots contact the ground with four points. However, it is difficult for almost all of such biped robots to maintain four-point contact on uneven terrains because they have rigid and flat soles. In order to solve the problem, foot mechanisms should be studied. In 2003, we developed WS-1R (Waseda Shoes - No.1 Refined) which is able to maintain four-point contact. However, it is difficult to deal with the concave or convex ground because of the problems of the contact detection and sideways slip. So, WS-5 (Waseda Shoes - No.5) has been developed. To avoid the slip of the foot, a cam-slider locking system consisting of a solenoid and a cam is constructed and installed at the foot. Also, linear encoders are employed to measure the position of the foot sliders. Through walking experiments on uneven terrains, the effectiveness of WS-5 is confirmed.

Previously, the realization of ascending and descending stairs and landing pattern modification control by WL-16RII were reported. However, it is difficult to use the landing pattern modification control when ascending stairs, because of the insufficient stroke of linear actuators. In this report, the design of a double stage linear actuator with a larger expansion and contraction ratio is described. The new linear actuators developed have been installed in WL-16RII, and several experiments were conducted. Through experiments involving walking with a wide step length and ascending a stair with landing pattern modification control, the effectiveness of the actuator developed is confirmed.

This paper describes how to compensate unknown external forces caused by a rider's motion of a biped walking vehicle. When external forces act on a robot's waist, the waist is accelerated so that a measured ZMP may be equal to a reference ZMP. To inhibit the divergence of the waist motion, the reference ZMP is varied inside a support polygon. However, if a large external force acts on a robot, the waist trajectory does not converge by only controlling a reference ZMP. So, ZMP trajectory is varied by changing a foot-landing point. Using the proposed control method, WL-16RIV (Waseda Leg-No. 16 Refined IV) achieved a stable human-carrying walking under unknown external forces which exert forward and sideways on the robot's waist. Through various walking experiments, the effectiveness of the proposed method was confirmed.

Many researchers have been studied on acceleration control algorithms for biped robots to deal with uneven terrain. However, the control algorithms are difficult to be used for human-carrying biped walking robots because of modeling errors. In this paper, a landing pattern modification method is proposed which based on nonlinear compliance control. Theoretical compliance displacements calculated from a walking pattern are compared with the actual compliance displacements, while a robot's foot touches slightly uneven terrain. In result, the height of landing terrain is detected, and the preset walking pattern is modified. Using this method, a human-carrying biped robot would be able to walk stably on uneven terrain. This pattern modification method does not need any special sensors except force sensors. Through various walking experiments, the effectiveness of the method is confirmed

This paper describes one method to stop suddenly and safely avoid falling using only hardware and without a computer system. This method consists of attaching a braking function to leg actuators and the development of a fall avoidance mechanism, attached to the robot's foot. Using the human-carrying biped locomotor WL-16RII developed by Sugahara et al., the effectiveness of the method proposed in this paper was confirmed through an emergency stopping experiment during walking, while carrying a heavy load

A new humanoid robot-WABIAN-2- that can be used as a human motion simulator is proposed in this paper. Its trunk is designed in order to permit rotation, and forward, backward, and sideway movement. Further, its arms are designed to support its complete weight when pushing a walk-assist machine. Moreover, it can lean on a walk-assist machine by forearm control using trunk motion. Basic walking experiments with WABIAN-2 are conducted with and without a walk-assist machine, thereby confirming its effectiveness

Many researchers have been studying on walking control methods for biped robots. However, the effectiveness of these control methods was not verified in outdoor environments such as pedestrian roads and gravel roads. In this paper, a landing pattern modification method adaptable to uneven terrain in a real environment is proposed which is based on a predictive attitude compensation control and a nonlinear compliance control. This method does not require any other sensors except force sensors. Also, a new biped foot system is described which can form larger support polygons on uneven terrain than conventional biped foot systems. Using the modification method and the foot system, WL-16RII (Waseda Leg-No.16 Refined II) achieved a stable walk on bumpy terrain with 20 mm height and 10 degrees inclination. Furthermore, a stable dynamic walk was realized on a paved road, when a human rode it. Through various walking experiments, the effectiveness of the method was confirmed

A humanoid robot, WABIAN-2R, capable of human-like walk with stretched knees and heel-contact and toe-off motions is proposed in this paper. WABIAN-2R has two 1-DOF passive joints in its feet to enable it to bend its toes in steady walking. Further, it has two 6-DOF legs, a 2-DOF pelvis, a 2-DOF trunk, two 7-DOF arms with 3-DOF hands, and a 3-DOF neck. In addition, a new algorithm for generating walking patterns with stretched knees and heel-contact and toe-off motions based on the ZMP criterion is described. In this pattern generation, some parameters of the foot trajectories of a biped robot are optimized by using a genetic algorithm in order to generate a continuous and smooth leg motion. Software simulations and walking experiments are conducted, and the effectiveness of the pattern generation and mechanism of WABIAN-2R, which have the ability to realize more human-like walking styles in a humanoid robot, are confirmed

This paper describes a passive dynamic model of passenger for a biped walking vehicle. The walking pattern generation that enables stable walking even if passenger sits naturally is also described. The model consists of lower-limbs part assumed to be fixed to the robot, and the upper body assumed to be 1 particle with 2 DOF mounted on the seat via 2 springs and dampers. The parameters are identified through waist shaking experiments by using a force-torque sensor under the seat. The walking pattern generation method involves the proposed model being built onto a strict model of the robot, and through iteration computation, a stable walking pattern is generated. The effectiveness of the proposed method is confirmed through experiments

Biped walking is easily adaptable to rough terrain such as stairs and stony paths, but the walk speed and energy efficiency on the flat ground is not so effective compared with wheeled locomotion. In this paper, we propose a biped robot to be able to walk or wheel according to the ground conditions. For wheeled locomotion, WS-2 (Waseda Shoes -No. 2) is developed which is composed of a DC motor, a spherical caster and two rubber pads on each foot. WS-2 is attached to the feet of WL-16 (Waseda Leg -No. 16) that is the world's first biped-walking robot capable of carrying a human. Also, a path planning for wheeled locomotion is presented. Through hardware experiments, the effectiveness of this foot module is confirmed.

This paper describes a walking control method on inclined planes for a biped locomotor. The walking control consists of a position control, virtual compliance control and posture control. Parameters of the compliance control are changed continuously in support and swing phases. The orientation of robot’s waist is kept level by posture control. Several walking experiments on inclined planes are conducted using WL-16R (Waseda Leg - No. 16 Refined). WL-16R has achieved stable walking on unknown inclined planes using the walking control method, and the effectiveness of the walking control is confirmed.

This paper describes the evaluation of three different walking patterns of a biped humanoid robot. Stretch-walking patterns with straight legs for a biped robot are compared with conventional walking patterns with bent legs in terms of energy consumption. This paper discusses walking pattern generation for various walks. To confirm the walking pattern evaluation, we have developed a biped robot, WABIAN-2/LL, whose leg mechanism differs from the conventional leg mechanism that has 3 DOF (degrees of freedom) in each ankle, 1 DOF in each knee, 3 DOF in each hip, and 2 DOF in the waist. Walking experiments are conducted with WABIAN-2/LL, and the results demonstrate that stretch walking patterns are effective in terms of energy consumption.

To date, many control methods have been studied, assuming that the soles of a biped walking robot contact the ground as four points. It is difficult for a biped robot with rigid and flat soles to maintain four-point contact on uneven terrain. It means that the biped robot can lose its balance. To solve this kind of problem, we should study not only stability control methods but also foot mechanisms. In this paper, a new foot system, WS-1 (Waseda shoes $no.1), is proposed to maintain four-point contact. This foot system consists of cam-type locking mechanism. WS-1 is attached to the feet of WL-16 (Waseda leg - no.16) that is the world's first biped-walking robot capable of carrying a human. Through hardware experiments, the effectiveness of the foot system is confirmed.

This paper describes the means of tuning-up method of the walking parameters to go up and down stairs for a biped robot with leg mechanisms using Stewart platforms. It has been confirmed that the stroke range of use could be reduced by tuning up the waist yaw trajectory and preset ZMP trajectories for motion pattern generation. By using the developed method, a walking experiment involving movement up and down a stair with the rise of 250 mm and certain walking experiments ascending and descending stairs carrying a human were successfully completed. Through these experiments, the effectiveness of the proposed method was confirmed.

Almost all conventional biped humanoid robots have difficulties in realizing various walking motions such as knee stretch walking like a human because of an insufficiency of DOF. Therefore, we have developed a 16-DOF biped humanoid robot without a trunk: 3-DOF in each ankle, 1-DOF in each knee, 3-DOF in each hip and 2-DOF in the waist. Using the biped robot, basic experiments are conducted and the effectiveness of the leg mechanism is confirmed.

This paper describes the mechanism of biped locomotor, WL-16 (Waseda Leg No. 16), its compliance control method and experiments carrying a human. This robot is developed based on WL-15's basic design using new gimbals' mechanisms with small backlash and new linear actuators dealing with a heavy payload and a wide movable range. Walking experiments carrying a human are successfully completed and the effectiveness of WL-16's mechanism and control method are confirmed.

This paper describes a method of motion pattern generation for biped humanoid robot to walk like humans or walk with various kind of motions. To realize biped walking avoiding singularity at stretching leg, pattern generation uses predetermined knee joint trajectories. Reduction of DOF by predetermination is complemented by waist motion. The effectiveness of generated dynamic walking patterns is confirmed by using a 16-DOF biped robot WABIAN-2/LL.

This paper describes the development of the support torque reduction mechanism for a biped locomotor with leg mechanisms using Stewart platforms, designed for heavy payload and low power consumption during walking. The basic design of this mechanism was decided through preliminary experiments. Each leg of the robot is equipped with this mechanism consisting of 2 gas springs with different reaction forces, which are switched according to the swing/support phase. The experiment measuring motor current during walking with payload and the walking experiment with maximum payload confirmed the effectiveness of this mechanism.

In this paper a humanoid robot named as WABIAN-RIV (WAseda BIpedal humANoid Refined IV) is analyzed in terms of stiffness characteristics. This paper proposes basic models and a formulation in order to deduce the stiffness matrix as a function of the most important stiffness parameters of the WABIAN architecture. The proposed formulation is useful for numerical estimation of stiffness performances.

This paper describes a control and a structure of a battery driven bipedal robot, WL-15(Waseda Leg-15), which has a 6-DOF parallel mechanism. WL-15 has been designed as a multi-purpose locomotion of robotic systems. This robot is controlled by the QNX real-time operating system. Using Math Works' SIMULINK and OPAL-RT's RT-LAB executed on Windows NT and QNX target systems, control software and pattern generator are developed. A walking control capable of dealing with various dynamic walking is proposed and tested indoors and outdoors using the WL-15. Dynamic biped walking is realized with the maximum step length of 200 mm, the maximum walking speed of 0.8 s/step and the minimum speed of 1.92 s/step. Also, the WL-15 is confirmed to be able to turn 90 deg in two steps and carry a load of 18 kg.

This paper describes the knee stretch walking of the biped robot that has three degrees of freedom (DOF) in the ankle, one DOF in the knee and three DOF in the hip. To create the stable stretch walking pattern, a walking pattern generation method capable of specifying arbitrarily the knee joint angle is introduced. The motion of the waist avoids the singularity of the swing leg that can exist in single support phase. A compensatory motion algorithm to cancel the moments generated by the motion of the lower-limbs calculates the waist motion. Through stretch walking simulations, the effectiveness of the pattern generation method is confirmed.

This paper describes a control method for a stable biped walking on uneven terrain. The walking control consists of a position control and a compliance control. In order to realize dynamic walking on a human living environment, a biped locomotor is controlled by the position control based on a compensatory motion. Also, in this research, to reduce the magnitude of impact forces and to guarantee a stable landing on the ground, the position-based virtual compliance control is introduced. Several walking experiments on uneven terrain are conducted using WL-15 (Waseda Leg-15) and the effectiveness of the control method is confirmed.

This paper describes an online method generating walking patterns for biped humanoid robots having a trunk. Depending on the walking command, the motion patterns of the lower-limbs are created and connected to the prewalking patterns smoothly in online. For the stability of the biped robots, the trunk and the waist motion is generated by a walking stabilization control that is based on the ZMP trajectory and the motion of the lower-limbs. Experimental tests of versatile biped walking on a plane surface are conducted using an auditory interface, and the validity of the online pattern generation method is verified.

This paper describes the design of a battery driven bipedal robot, which uses 6-DOF parallel mechanisms for its each leg. We have designed this considering a bipedal robot as the leg module that is sufficient for practical use as a multi-purpose locomotor of the robot system. This robot is applicable to various fields, such as medical, welfare and entertainment. In the design of the robot, we have reduced the weight to the maximum extent, taking advantage of the features of the parallel mechanism where the mechanism rigidity is high. Using the developed bipedal locomotor, dynamic walking with the step time of 0.96 sec/step and the step length of 0.2 m/step was conducted, and the effectiveness of its mechanism was confirmed.

Describes a locomotion control for biped humanoid robots based on balance and and impedance control. The balance control is employed during a whole walking cycle, which can compensate for the moments generated by the biped walking. In the control, the compensatory motion of the trunk and waist is calculated from the trajectories of the lower-limbs, arms, head and ZMP. The parameters of the impedance control are adjusted in real-time according to the gait phase. The large damping coefficient of the impedance is applied to the landing leg to absorb the impact/contact force during the contact phase, while the large stiffness is given to increase the momentum reduced by the viscosity of the landing leg during the first half single support phase. By dynamic walking experiments using a human-like robot WABIAN-RIII, the validity of the proposed control methods is verified.

This study is aimed at the realization of a continuous walking-pattern generated by combining some different patterns such as turning, forward, backward and side step patterns. A biped-walking robot is required to have the function of followability and stability to achieve continuous follow walking in a humans living environment. Unit patterns for a biped locomotion are continuously generated by a walking pattern generator, and the complete walking pattern for followability is determined by synthesizing the unit patterns. The compensatory motion of the trunk and waist that is calculated by a stabilization control method ensures the stability of combined walking patterns. To explore human-like walking, we have constructed a two-legged robot, WABIAN-RII (WAseda Bipedal humANoid robot-Revised II). Through hardware experiments, the continuous biped walking is realized.

This paper describes three emotions such as happiness, sadness and anger. The emotions are realized by the walking patterns of a biped personal robot that are defined by the parameterization of its whole body motion. The combined motion of the waist and trunk calculated by the compensatory control algorithm that has been proposed already is used to cancel the moments generated by the motions of the head, the lower-limbs and the upper-limbs. To experiment emotion expression, we have constructed a human-like personal robot WABIAB-RII (WAseda BIpedal humANoid robot-Revised II) that has forty-three mechanical degrees of freedom and four passive degrees of freedom. Simulation and experimental results of emotional walking are also presented.

We would like to give biped humanoid robots a following motion as one of the functions capable of supporting humans. Unfortunately, not much attention has been paid to research on human-following motions to date. In this paper, a follow-walking control method is described to realize such motions, which consists of a pattern synthesis part and a balance motion control part. First, we generate switchable unit patterns of a biped humanoid robot, based on human-robot interaction. Second, the unit patterns are synthesized according to the sense of the resultant contact forces. Finally, the compensatory motion of the trunk and waist is calculated by a cooperative motion control algorithm for the balance of the biped robot.

The paper describes the balance control of biped locomotion systems. A biped humanoid robot is modeled and studied focusing on the realization of human-like walking. Firstly, the smooth motion of its lower limbs is characterized in terms of a set of walking variables. Secondly, to cancel moments produced by the motion of the lower limbs, the motion of its trunk and waist is derived by an iteration method. Finally, program control using a preset walking motion is applied to the biped robot. To confirm human-like walking, we have constructed a human-like biped robot called WABIAN-RII (WAseda BIped HumANoid robot-Revised II) that has a total of forty-three mechanical degrees of freedom (DOF). Experiments of a human-follow walking are conducted using the WABIAN-RII.

Presents the human safety mechanisms of a human friendly robot (HFR) capable of coexisting with human beings. In order to realize human safety, the HFR is required to be composed of an elastic material-covered manipulator and a passive viscoelastic trunk mounted on a passively movable base like a human's structure. During an expected or unexpected collision/contact between the HFR and its environment, the produced collision/contact forces are extremely attenuated by the combination motion of the passive viscoelastic trunk and passively movable base. The collision-tolerant control algorithm has been developed for the end-effector of the HFR to maintain its desired task during the expected or unexpected collision. Results of collision experiments show that the compliant trunk and movable base are effective mechanisms of suppressing collision forces, and the control algorithm is an effective method of positioning the end-effector.

We have proposed the collision-tolerant mobile manipulator equipped with a passive trunk (i.e., supporting part). In collision experiments with unknown environments, results show that this mechanism is suitable for the suppression of contact forces which is an important issue for human-robot collaborations. The trunk with mechanical elements such as springs and dampers is passively deformed to deal with physical contacts, while the mobile platform moves around on the horizontal plane in response to friction between the platform and the ground. The end-effector of the manipulator, however, is difficult to track a desired task due to the deformation of the compliant trunk and the mobility of the platform. In order to solve the problem, the desired joint configurations of the manipulator are directly calculated according to the movement of the trunk and the platform, and a feedback control scheme is employed.