This paper focuses on a stabilization control for multi-contact motion which enables a humanoid robot to locomote by realizing dynamic contact transitions on non-flat environment. In the stabilization process of the multi-contact motion, the desired Zero-Moment Point (ZMP) is modified by the position of the Divergent Component of Motion (DCM) error with respect to the 3D Center of Mass (CoM) motion generated from the force distribution ratio. The contact wrench of each end-effector is determined by quadratic optimization considering the centroidal dynamics and contact friction constraints so as to satisfy the modified ZMP. Each end-effector is controlled by optimized force reference through a projection of null space by force distribution ratio. We propose a multi-contact stabilization framework which can be designed not only to generate 3D CoM motion but also the CoM position estimation and the optimal force distribution around the reference ZMP in a unified manner from a balance controller, by using the force distribution ratio. The effectiveness of proposed method is validated by a quadruped locomotion leaning against a vertical wall using the joint position controlled humanoid HRP-5P in a dynamic simulator.

In order to accurately reach a target position while executing a task which imposes occlusion or constraints of the posture, a humanoid robot requires an adaptive locomotion system, which can comprehensively integrate localization, environmental mapping, global locomotion planning and local error correction. In this paper, we propose a method of constructing a perception based locomotion system for a humanoid robot. The major contribution of this paper is solving a problem of the locomotion error caused by the task constraints, by locally compensating footsteps and assessing the need for global footstep re-planning online based on environmental measurements. The proposed system provides an accurate and dense ground point cloud, called HeightField, using plane estimation and space interpolation, and obstacle point cloud for frequent collision avoidance by accumulating laser scans. This environmental perception enables a humanoid robot to plan footsteps globally even in the situation where the sight of the robot is limited and compensate footsteps while estimating landing state during locomotion online with the localization result. We evaluated the practicality of the proposed system by applying it to our humanoid robot carrying a heavy object in a construction site and confirmed that the proposed system contributed to improved locomotion abilities of a humanoid robot engaging in heavy-duty or dangerous tasks.

For mobile robots, 3D acquisition is required to model the environment. Particularly for humanoid robots, a modeled environment is necessary to plan the walking control. This environment can include both static objects, such as a ground surface with obstacles, and dynamic objects, such as a person moving around the robot. This paper proposes a system for a robot to obtain a sufficiently accurate shape of the environment for walking on a ground surface with obstacles and a method to detect dynamic objects in the modeled environment, which is necessary for the robot to react to sudden changes in the scene. The 3D acquisition is achieved by a projector-camera system mounted on the robot head that uses a structured-light method to reconstruct the shapes of moving objects from a single frame. The acquired shapes are aligned and merged into a common coordinate system using the simultaneous localization and mapping method. Dynamic objects are detected as shapes that are inconsistent with the previous frames. Experiments were performed to evaluate the accuracy of the 3D acquisition and the robustness with regard to detecting dynamic objects when serving as the vision system of a humanoid robot.

Our work builds largely on Nagasaka's stabilizer in multi-contact motion [1]. Using a sequence of contact stances from an offline multi-contact planner, we use first a Model Predictive Controller to generate a dynamic trajectory of the center of mass, then a whole-body closed-loop model-based controller to track it at best. Relatively to Nagasaka's work, we allow frame changes of the preferred force, provide a heuristic to compute the timing of the transition from purely geometrical features and investigate the synchronization problem between the reduced-model preview control and the whole-body controller. Using our framework, we generate a wide range of 3D motions, while accounting for predictable external forces, which includes transporting objects. Simulation scenarios are presented and obtained results are analyzed and discussed.

A controller design to suppress vertical vibration of a position controlled biped walking robot is presented. The system model of structural vibration is estimated from a measurement of frequency response. By using the model, an optimal feedback controller with full state observer is designed. With a consideration of leg support phase, the vibration controller is combined into our walking controller. The effectiveness of our controller is experimentally demonstrated.

This paper presents a method for generating a turning motion in a humanoid robot by allowing the feet of the robot to slip on the ground. As humans, we exploit the fact that our feet can slip on the ground, and allowing humanoid robots to realize this same motion is a worthwhile study. In this paper, we propose the hypothesis that a turning motion is caused by the effect of minimizing the power generated by floor friction. A model of rotation from this friction is then described based on our hypothesis. The proposed model suggests that only the trajectory and shape of the robot's feet determine the amount of rotation from a slip, and that the friction coefficient between the floor and the soles of the robot, as well as the velocity of the feet, do not affect the resultant angle. Verification is conducted through an experiment with a humanoid robot known as HRP-2. Next, to obtain the foot motion necessary to realize the desired rotational angle, the inverse problem is solved by confining the trajectory of the center of the foot to an arc shape. This solution is verified through an experiment with another humanoid robot, HRP-4C.

We present the realization of quick turning motion of a humanoid robot on its toes via slipping between its feet and the floor. A rotation model is described on the basis of our hypothesis that turning via slip occurs as a result of minimizing the power caused by floor friction. Using the model, the trajectory of the center of the foot can be generated to realize the desired rotational angle. Toe joints are used to realize quicker turning motion, while avoiding excessive motor load due to frictional torque. Quick slip-turn motion with toe support is successfully demonstrated using a humanoid robot HRP-4C.

This paper presents the development of humanoid robotics platform - 4 (or HRP-4 for short). The high-density implementation used for HRP-4C, the cybernetic human developed by AIST, is also applied to HRP-4. HRP-4 has a total of 34 degrees of freedom, including 7 degrees of freedom for each arm to facilitate object handling and has a slim, lightweight body with a height of 151 [cm] and weight 39 [kg]. The software platform OpenRTM-aist and a Linux kernel with the RT-Preempt patch are used in the HRP-4 software system. Design concepts and mechanisms are presented with its basic specification in this paper.

Hardware improvement of cybernetic human HRP-4C for entertainment is presented in this paper. We coined the word ¿Cybernetic Human¿ to explain a humanoid robot with a realistic head and a realistic figure of a human being. HRP-4C stands for Humanoid Robotics Platform-4 (Cybernetic human). Its joints and dimensions conform to average values of young Japanese females and HRP-4C looks very human-like. We have made HRP-4C present in several events to search for a possibility of use in the entertainment industry. Based on feedback from our experience, we improved its hardware. The new hand, the new foot with active toe joint, and the new eye with camera are introduced.

This paper presents the development of humanoid robotics platform - 4 (or HRP-4 for short). The high-density implementation used for HRP-4C, the cybernetic human developed by AIST, is also applied to HRP-4. HRP-4 has a total of 34 degrees of freedom, including 7 degrees of freedom for each arm to facilitate object handling and has a slim, lightweight body with a height of 151 [cm] and weight 39 [kg]. The software platform OpenRTM-aist and a Linux kernel with the RT-Preempt patch are used in the HRP-4 software system. Design concepts and mechanisms are presented with its basic specification in this paper.

A novel framework of biped walking stabilization control is introduced. The target robot is a 42 DOF humanoid robot HRP-4C which has a body dimensions close to the average Japanese female. We develop a body posture controller and foot force controllers on the joint position servo of the robot. By applying this posture/force control, we can regard the robot system as a simple linear inverted pendulum with ZMP delay. After a preliminary experiment to confirm the linear dynamics, we design a tracking controller for walking stabilization. It is evaluated in the experiments of HRP-4C walking and turning on a lab floor. The robot can also perform an outdoor walk on an uneven pavement.

This paper proposes a reactive leg motion generation method which integrates geometric constraints into its generation process. In order to react given instructions instantaneously or to keep balance against external disturbances, feasible steps must be generated automatically in real-time for safety. In many cases this feasibility has been realized by using predefined steps or admissible stepping regions. However, these predefinitions are often too conservative or valid only in limited situations. The proposed method considers geometric constraints in addition to joint limits during its generation process and it can utilize the ability of the robot to a maximum extent. It can generate feasible walking pattern in real-time by modifying the swing leg motion and the next landing position at each control cycle. The proposed method is validated by experiments using a humanoid robot HRP-2.

This paper proposes a new framework to recover balance against external forces by combining disturbance suppression and reactive stepping. In the view point of the feedback control, a reactive step can help to diminish the disturbance caused by an external force that should be compensated to maintain balance. In other words, if the adequate step is performed, the feedback controller does not have to compensate all of the external force by itself. Under this concept, we propose an original solution to distribute the compensation between a feedback controller and a reactive step, according to the period of support phase and a disturbance characteristic. We first clearly distinguish between the role of the disturbance suppression and the reactive stepping. Then, based on this distinction, the small disturbance of external force or happening late during the single-support phase, is mainly suppressed by state feedback. The large disturbance which is out of capability by feedback controller and at the beginning of the single-support phase, is absorbed by modifying reactively the next steps. The proposed method is validated through experimental results with the HRP-2 humanoid robot.

In this paper, we generate the biped gait of a humanoid robot that looks like a human's one. To generate the human like motion, we first capture walking motion of a human. Then, we analyze the captured data and obtain several information such as the relationship between the step length and waist height etc. We consider applying these informations to the real humanoid robot. Also, when the human walks, the sway of the waist is smaller than most of the humanoid robot's one. By compensating the angular momentum of the robot and by modifying the ZMP trajectory, we show that sway of the robot's waist can be smaller. We show the effectiveness of the proposed method through simulation and experimental results.

This paper presents an easy and fast method of testing force closure when a multi-fingered hand grasps an object. Different from previous methods, we consider approximating the friction cone by using a few ellipsoids. By using this method, the total force/moment set applied to the grasped object can be obtained by a common set of multiple ellipsoids. This method is effective since we can test the force closure by simply calculating the inequalities of quadratic form. Moreover, by using the ellipsoidal approximation, we propose an easy method of evaluating the grasp stability. We show that the grasp stability can be calculated by using simple equations. The effectiveness of the proposed method is verified by several numerical examples where we show that the proposed method is fairly accurate and can evaluate the grasp stability faster than conventional methods.

This paper discusses the grasp planning of a multifingered hand attached at the tip of a robotic arm. By using the convex models and the new approximation method of the friction cone, our proposed algorithm can calculate the grasping motion within the reasonable time. For each grasping style used in this research, we define the grasping rectangular convex (GRC). We also define the object convex polygon (OCP) for the grasped object. By considering the geometrical relashionship among these convex models, we determine several parameters needed to define the final grasping configuration. To determine the contact point position satisfying the force closure, we use two approximation models of the friction cone. To save the calculation time, the rough approximation by using the ellipsoid is mainly used to check the force closure. Additionally, approximation by using the convex polyhedral cone is used at the final stage of the planning. The effectiveness of the proposed method is confirmed by some numerical examples.

This paper proposes the kinodynamic gait planning for humanoid robots where both kinematics and dynamics of the system are considered. We can simultaneously plan both the foot-place and the whole-body motion taking the dynamical balance of the robot into consideration. As a dynamic constraint, we consider the differential equation of the robotpsilas CoG. To solve this constraint, we assume two walking pattern generators; the offline and the online ones. We randomly sample the configuration space to search for the path connecting the start and the goal configurations. When sampling the configuration space, three milestones are sequentially connected to the parent milestone. To show the effectiveness of the proposed methods, we show simulation and experimental results where the humanoid robot HRP-2 walks on several environments.

In this paper, the development of humanoid robot HRP-3 is presented. HRP-3, which stands for Humanoid Robotics Platform-3, is a human-size humanoid robot developed as the succeeding model of HRP-2. One of features of HRP-3 is that its main mechanical and structural components are designed to prevent the penetration of dust or spray. Another is that its wrist and hand are newly designed to improve manipulation. Software for a humanoid robot in a real environment is also improved. We also include information on mechanical features of HRP-3 and together with the newly developed hand. Also included are the technologies implemented in HRP-3 prototype. Electrical features and some experimental results using HRP-3 are also presented.

This paper presents a motion pattern generator of humanoid robots that walks on a flat plane, steps and a rough terrain. It is guaranteed rigorously that the desired contact between a humanoid robot and terrain should be maintained by keeping the contact wrench sum between them inside the contact wrench cone under the sufficient friction assumption. A walking pattern is generated by solving the contact wrench equations and by applying the resolved momentum control.

We discuss a ZMP-based running pattern generation for a biped robot equipped with toe springs. Our biped robot HRP-2LT has twelve active DoFs for its legs and two passive DoFs for its toes. The trajectory of the center of mass is designed to realize the specified running motion and the foot trajectories are determined to get proper spring action at lift off phases. They are interpreted into joint angles by using the resolved momentum control. By the simulation and the preliminary experiment, it is shown that the toe springs are effectively used for running and hopping.

This paper presents a development of multi-fingered hand, which is modularized and can be attached to life-size humanoid robots. The developed hand has four fingers with 17 joints, which consist of 13 active joints and 4 linked joints. A miniaturized 6-axes force sensor is newly developed and is mounted on each fingertip for improving the manipulability. A main node controller with I/O, motor drivers, and amplifiers for 6-axes force sensors are also newly developed. These components are equipped in the hand for modularization. The developed hand is designed so as to realize about 8 [N] forces on the pad point of stretched finger, supposing transmission efficiency of drive system is 55 [%]. In this paper, the mechanisms of hand module, its specifications, and electrical system are also introduced.

This paper proposes a method of a real-time gait planning for humanoid robots which can change stride immediately at every step. Based on an analytical solution of an inverted pendulum model, the trajectories of the COG (center of gravity) and the ZMP (zero-moment point) are parameterized by polynomials. Since their coefficients can be efficiently computed with given boundary conditions, this framework can provide a real-time walking pattern generator for humanoid robots. To handle the unexpected result caused by immediate changes of foot placement, we made single support periods as an additional trajectory parameter and the ZMP fluctuation was suppressed by mixing the opposite phase of the ZMP error. The effectiveness of our method is shown by experiments of the humanoid robot HRP-2.

This paper studies an optimal planning of falling motions of a human-sized humanoid robot to reduce the damage of the robot. We developed a human-sized robot HRP-2FX which has a simplified humanoid robot shape with seven d.o.f. and can emulate motions in the sagittal plane of a humanoid robot. An optimal control is applied to generate the falling motion of HRP-2FX to minimize a performance index, and the optimality has been verified by the experiments on HRP-2FX.

This paper proposes a universal stability criterion of the foot contact of legged robots. The proposed method checks if the sum of the gravity and the inertia wrench applied to the COG of the robot, which is proposed to be the stability criterion, is inside the polyhedral convex cone of the contact wrench between the feet of a robot and its environment. The criterion can be used to determine the strong stability of the foot contact when a robot walks on an arbitrary terrain and/or when the hands of the robot are in contact with it under the sufficient friction assumption. The determination is equivalent to check if the ZMP is inside the support polygon of the feet when the robot walks on a horizontal plane with sufficient friction. The criterion can also be used to determine if the foot contact is sufficiently weakly stable when the friction follows a physical law. Therefore, the proposed criterion can be used to judge what the ZMP can, and it can be used in more universal cases

A biped walking pattern generator which allows an additional ZMP control (auxiliary ZMP) is presented. An auxiliary ZMP is realized by an inverse system added to a pattern generator based on the ZMP preview control. To compensate the effect of the auxiliary ZMP, we apply virtual time shifting of the reference ZMP. As an application of the proposed method, a walking control on uneven terrain is simulated. The simulated robot can walk successfully by changing its walking speed as the side effect of the auxiliary ZMP control

In this paper we realize a real-time communication on Ethernet and develop an onbody distributed control system for a humanoid robot, HRP-3P. Real-time communication on Ethernet is realized by (1) a communication method using the data link layer directly and (2) timing control using a real-time operating system ARTLinux. This enables us to reduce the cost of embedded systems and improve developmental efficiency. A CORBA implementation which works on this communication layer is also developed to increase compatibility with existing software. Finally a small-size distributed robot controller is developed for the onbody network of HRP-3P and a distributed I/O system is developed on top of this

This paper presents a motion suspension system to suspend humanoid motion in case of emergency. Once humanoids start their motions in human daily environments, there is a possibility that humanoids will meet with several emergencies such as hurting humans and injuring themselves. Even so, humanoids should be controlled so that they avert such emergencies in real-time. To realize this demand, we propose a method of real-time judgment of emergency prediction by humanoids. We also propose a simple and effective method of real-time pattern generation to force humanoids to stop immediately by one step without falling. To verify the validity of the proposed method, we finally present experimental results using a humanoid robot HRP-2, which include experiments at 2.8 [km/h] walks

A motion planner of emergency stop must make an operating humanoid robot to a stationary state under the emergency signal. It plays an important role in prevention of falling over because humanoid robots fall over easily. Immediately after the emergency signal, it must generate the emergency stop motion in real-time. We modeled a humanoid robot as a simple dynamic system consists of ZMP (zero-moment point) and COG (center of gravity) as its states. The emergency stop motion is generated by a state feedback. We determined optimal feedback gains in terms of the initial conditions and the pole assignment. The proposed method realized a reliable emergency stop with low computational cost. Furthermore, it can easily predict the possibility of the successful emergency stop at any time. The validity of the proposed method is confirmed by an experiment using humanoid robot HRP-2

In this paper, we analyze the balance of a humanoid robot during manipulation tasks. By defining the generalized zero-moment point (GZMP), we obtain the region of it for keeping the balance of the robot during manipulation. During manipulation, the convex hull of the supporting points forms the 3-D convex polyhedron. The region of the GZMP is obtained by considering the infinitesimal displacement and the moment about the edges of the convex hull. We show that we can determine whether or not the robot may keep balance for several styles of manipulation tasks, such as pushing and pulling an object. The effectiveness of our proposed method is demonstrated by simulation.

This paper studies the balance of a humanoid robot carrying a heavy object. Without knowing the mass and the position of the center of gravity of the object, the humanoid robot carries a heavy object stably by using the force sensor information attached at the wrists and the ankles. We first show how to generate the motion of a humamoid robot by taking the force sensor information into consideration. We also show the method for generating the gait pattern by taking the dynamics of the carried object. The effectiveness of the proposed method is shown by experiments.

This article explains a control system, which stabilizes running biped robot HRP-2LR. The robot uses prescribed running pattern calculated by resolved momentum control, and a running controller stabilizes the system against disturbances. The running controller consists of posture stabilization, inverted pendulum stabilization, contact torque control, impact absorbing control, foot vertical force control and torque distribution control. Applying the proposed controller, HRP-2LR could successfully run with average speed of 0.16(m/s) repeating flight phase of 0.06 (s) and support phase of 0.3 (s).

This paper proposes a method for a humanoid robot to generate 3D model of the environment using a stereo vision, find a movable space using it and plan feasible locomotion online. The model is generated by an accumulation of 3D grid maps which are made from the range data of the field of view obtained by a correlation based stereo vision. The locomotion is planned by an online whole body pattern generator which can modify robot’s waist height, an upper body posture and so on according to the size of the movable space.

This paper describes a generation method for spatially natural biped walking. By limiting the COG (Center of Gravity) motion space to a sculptured surface, the degree of freedom of the COG matches to the number of the ZMP (Zero Moment Point) equations. The COG motion can be uniquely generated along a specified surface satisfying the ZMP constraint with low calculation cost. Spatial and time parts are separable by representing motion surface of the COG as parametric variables. The motion surface defines the relative height of the COG from the landing foot position. Thus, the proposed method reflects geometric information directly to the motion planning without considering walk stability. In this paper, we show two actual examples, walking pattern including mostly stretched knee and going up stairs. The validity of the proposed method is confirmed by simulation. Walking with mostly stretched knee is also shown in experiment using HRP-2.

This paper presents a slip observer towards stabilizing biped walks on a low friction floor. Although biped humanoid robots are expected to easily adapt to environments designed for human, in fact they tend to tip over easily on real environments. For a practical use, it is one of important issues to stabilize a biped walking on an unexpected slippery floor with a low friction. In this paper, we propose the slip observer detecting skids that would occur at walking on unexpected slippery floor. We also propose a basic study of slip stabilizer towards reducing posture rolling caused by skids. Finally, we present experimental results using a humanoid robot HRP-2 to verify the validity of the proposed control scheme.

This paper presents an emergency stop algorithm of a walking humanoid robot. There are many cases which force a walking robot to stop quickly without falling. Since an emergency occurs at unpredictable timing and at any state of robot, the stopping motion must be generated in real-time. To overcome these problems, our emergency stop motion is divided into four phases according to the role of the zero-moment point (ZMP). In each phase, approximate analytical solutions of the center of gravity (COG) dynamics is used to generate the motion. During the single support phase, a landing time and position are determined by evaluating the average velocity of the swing leg and the horizontal position of the COG. During the double support phase, the travel distance of the COG and the ZMP are evaluated. The validity of the proposed method is confirmed by simulation and experiment using a humanoid robot HRP-2.

The goal of this study is developing a biped humanoid robot that can observe a human dance performance and imitate it. To achieve this goal, we propose a task model of lower body motion, which consists of task primitives (what to do) and skill parameters (how to do it). Based on this model, a sequence of task primitives and their skill parameters are detected from human motion, and robot motion is regenerated from the detected result under constraints of a robot. This model can generate human-like lower body motion including various waist motions as well as various stepping motions of the legs. Generated motions can be performed stably on an actual robot supported by its own legs. We used improved robot hardware HRP-2, which has superior features in body weight, actuators, and DOF of the waist. By using the proposed method and HRP-2, we have realized a dance performance of Japanese folk dance by the robot, which is synchronized with a performance of a human grand master on the same stage.

This work proposes a new style of manipulation by a humanoid robot. Focusing on the task of pushing an object, the foot placement of it is planed in real-time according to the result of manipulation of an object. By controlling the arms using the impedance control, a humanoid robot can push an object stably regardless of the mass of an object. If an object is heavy, a humanoid robot pushes an object with walking slowly, and vice versa. Also, for planning the gait in real-time, we newly propose an analytical method where the newly calculated trajectory of the robot motion is smoothly connected to the current one. The effectiveness of the proposed method is confirmed by simulation and experiment.

Aiming for a humanoid robot of the next generation, we have been developing a biped which can jump and run. This paper introduces biped robot HRP-2LR and its hopping with both legs as our first attempt towards running. Using a dynamic model of HRP-2LR, hopping patterns are pre-calculated so that it follows the desired profiles of the total linear and angular momentum. For this purpose we used resolved momentum control. Adding small modifications to negotiate the difference between the model and the real hardware, we successfully realized a steady hopping motion of 0.06 [s] flight phase and 0.5 [s] support phase. A hopping with forward velocity of 15 [mm/s] was also realized. Finally, a running pattern of 0.06 [s] flight and 03 [s] support phase was tested. HRP-2LR could successfully run with average speed of 0.16 [m/s].

This work studies locomotion planning of humanoid robots to pass through narrow spaces. Humanoid robots can alter the style of the locomotion while wheeled robots can not. The proposed method generates a 3D local map from visual information and plans the appropriate locomotion based on the map from biped walking with the variable height and the width and from crawling.

A development of humanoid robot HRP-2 is presented in this paper. HRP-2 is a humanoid robotics platform, which we developed in phase two of HRP. HRP was a humanoid robotics project, which had run by the Ministry of Economy, Trade and Industry (METI) of Japan from 1998FY to 2002FY for five years. The ability of the biped locomotion of HRP-2 is improved so that HRP-2 can cope with uneven surface, can walk at two third level of human speed, and can walk on a narrow path. The ability of whole body motion of HRP-2 is also improved so that HRP-2 can get up by a humanoid robot's own self if HRP-2 tips over safely. In this paper, the appearance design, the mechanisms, the electrical systems, specifications, and features upgraded from its prototype are also introduced.

This paper shows some preliminary results on the dynamical balance of a humanoid robot grasping an environment. By grasping an environment, it becomes easier for the robot to keep balance. By using the linear programming, a necessary condition for keeping balance of the robot is formulated taking the grasping force into consideration. We show that the occasion exists where the stronger the hand of a humanoid robot grasps the handrail, the larger the region of ZMP for keeping balance becomes. We further show an experimental result of a humanoid robot climbing up a big gap increasing the stability by grasping a handrail.

Biped walking on a low friction floor is analyzed in this paper. For a given walking pattern, we can calculate a necessary friction coefficient which allows the robot to perform the expected motion. To reduce the maximum necessary friction coefficient, a pattern generation based on preview control theory is explained. We also describe a calculation of slip concerned ZMP, which provides a good prediction of falling caused by slips. Finally, we test a walk of 135 [km/h] on low friction environment using a humanoid robot HRP-2. The robot could successfully walk over the slippery area whose friction coefficient is 0.14.

Aiming for a humanoid robot of the next generation, we have been developing a biped which can jump and run. This paper introduces a method of running pattern generation and running experiment of biped robot HRP-2LR. Based on the physical parameters of HRP-2LR, running patterns are pre-calculated so that it follows the desired profiles of the total linear and angular momentum. For this purpose we used resolved momentum control. The vertical momentum is calculated considering the compliant elements in order to realize accurate flight duration. The horizontal momentum is calculated to satisfy the ZMP patterns given in advance. Using our pattern, HRP-2LR could successfully run with average speed of 0.16[m/s] with repeat flight phase 0.06 [s] and support phase 0.3 [s].

This paper discusses the pushing manipulation of an object by a humanoid robot. For such a pushing task, we show that there are two kinds of ZMPs, i.e., the conventional "Zero Moment Point (ZMP)" considering all sources of the force/moment acting in the foot supporting area, and the "Generalized Zero Moment Point (GZMP)" which is an generalization of ZMP for a humanoid robot whose hands do not contact with an object. We first obtain the stable region of the GZMP on the floor. Moreover, since the difference between these two ZMPs corresponds to the magnitude of contact force applied by the hands, we propose the pushing manipulation by a humanoid robot by modifying the desired ZMP trajectory for a humanoid. The effectiveness of the proposed method is confirmed by simulation results.

We have developed a software platform, called OpenHRP, for humanoid robotics which consists of a dynamic simulator and motion control library for humanoid robots. This paper attempts to answer a frequently asked question "do the dynamic simulations and the experiments of biped walking of humanoid robots correspond?". Using OpenHRP and humanoid robots HRP-1S and HRP-2P, the comparisons between the simulations and experiments are shown at various aspects.

We introduce a new method of a biped walking pattern generation by using a preview control of the zero-moment point (ZMP). First, the dynamics of a biped robot is modeled as a running cart on a table which gives a convenient representation to treat ZMP. After reviewing conventional methods of ZMP based pattern generation, we formalize the problem as the design of a ZMP tracking servo controller. It is shown that we can realize such controller by adopting the preview control theory that uses the future reference. It is also shown that a preview controller can be used to compensate the ZMP error caused by the difference between a simple model and the precise multibody model. The effectiveness of the proposed method is demonstrated by a simulation of walking on spiral stairs.

This paper presents a humanoid robot that has the same size as a human and that can lie down to the floor and get up from the floor with the robot face upward and downward. We believe that the robot is the first life-size humanoid robot with the capability. The motions are realized by the combination of novel hardware and software. The features of the hardware are a human-like proportion and joints with wide movable ranges including two waist joints. The software segments the motion into the sequence of the contact states between the robot and the floor and assigns an appropriate controller to each transition between the consecutive states. The experimental results are presented.

This paper describes a possibility of a running humanoid robot based on the physical properties of an existing humanoid robot HRP-2L. To generate running motion, we develop a general method to control the total linear/angular momentum of a multi-link system. By this method, we can generate a reliable running pattern. Conducting simulations which take into account physical restrictions, we show that our humanoid robot can run at least at 0.5 m/s.

We have developed a humanoid robot HRP-2P with a biped locomotion controller, stereo vision software and aural human interface to realize cooperative works by a human and a humanoid robot. The robot can find a target object by the vision, and carry it cooperatively with a human by biped locomotion according to the voice commands by the human. A cooperative control is applied to the arms of the robot while it carries the object, and the walking direction of the robot is controlled by the interactive force and torque through the force/torque sensor on the wrists. The experimental results are presented in the paper.

This paper investigates a method through which 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.

This paper newly considers the ZMP (zero moment point) of a humanoid robot under arm/leg coordination. By considering the infinitesimal displacement and the moment acting on the convex hull of the supporting points, we show that our method for determining the region of ZMP can be applicable to several cases of the arm/leg coordination tasks. We first express two kinds of ZMPs for such coordination tasks, i.e., the conventional ZMP, and the "generalized zero moment point (GZMP)" which is a generalization of the ZMP to the arm/leg coordination tasks. By projecting the edges of the convex hull of the supporting points onto the floor, we show that the position and the region of the GZMP for keeping the dynamical balance can be uniquely obtained. The effectiveness of the proposed method is shown by simulation results.

We introduce a method to generate whole body motion of a humanoid robot such that the resulted total linear/angular momenta become specified values. First, we derive a linear equation, which gives to total momentum of a robot from its physical parameters, the base link speed and the joint speeds. Constraints between the legs and the environment are also considered. The whole body motion is calculated from a given momentum reference by using a pseudo-inverse of the inertia matrix. As examples, we generated the kicking and walking motions and tested on the actual humanoid robot HRP-2. This method, the resolved momentum control, gives us a unified framework to generate various maneuvers of humanoid robots.

For real-time walking control of a biped robot, we analyze the dynamics of a three-dimensional inverted pendulum whose motions are constrained onto an arbitrarily defined plane. This analysis leads us a simple linear dynamics, the Three-Dimensional Linear Inverted Pendulum Mode (3D-LIPM). Geometric nature of trajectories under the 3D-LIPM is discussed, and an algorithm for walking pattern generation is presented. Experimental results of real-time walking control of a 12-DOF biped robot HRP-2L using an input device such as a game pad are also shown.

A method of running pattern generation for a humanoid robot using the dynamics of a simple inverted pendulum is proposed. The dynamic simulation using a model of an actual humanoid robot shows that the robot can run by applying a generated pattern with slight modifications. The simulation is used to evaluate the required performance of the actuators for an actual running robot.

This paper introduces an open architecture humanoid robotics platform (OpenHRP) on which various building blocks of humanoid robotics can be investigated. OpenHRP is a virtual humanoid robot platform with a compatible humanoid robot, and consists of a simulator of humanoid robots and motion control library for them which can also be applied to a compatible humanoid robot as it is. OpenHRP is expected to initiate the exploration of humanoid robotics on an open architecture software and hardware, due to the unification of the controllers and the examined consistency between the simulator and a real humanoid robot.

This paper presents an advanced leg module developed for HRP-2. HRP-2 is a new humanoid robotics platform,. which we have been developing in phase two of HRP. HRP is a humanoid robotics project, which has been launched by Ministry of Economy, Trade and Industry (METI) of Japan from 1998FY to 2002FY for five years. The ability of the biped locomotion of HRP-2 is improved so that HRP-2 can cope with rough terrain in the open air and can prevent the possible damages to a humanoid robot's own self in the event of tipping over. In this paper the mechanisms and specifications of leg module, electrical system, simulation results utilized for deciding specifications, and experimental results are also introduced.

This paper investigates a method to minimize damage to a humanoid robot when it falls over to the ground. The strategy involves controlling the attitude of the robot while it is falling over so that it lands on the ground at one of shock-absorbing parts of the robot. A simulation study has confirmed that the proposed algorithm can make the robot land at specified shock-absorbing parts.

This paper presents an advanced leg module developed for HRP-2, a new humanoid robotics platform, which has been developed in phase two of the Humanoid Robotics Project (HRP), a five year program sponsored by the Ministry of Economy, Trade and Industry of Japan (METI) from 1998FY to 2002FY. The biped locomotion ability of HRP-1, the humanoid robotics platform developed in phase I is to be improved so that HRP-2 can cope with rough terrain and can prevent possible damage to the robot body caused by tipping over. In this paper, the mechanisms and specifications of the leg module, the electrical system, the simulation results utilized for deciding specifications, and some experimental results are presented.

This paper presents a prototype humanoid robotics platform developed for HRP-2. HRP-2 is a new humanoid robotics platform, which we have been developing in phase two of HRP HRP is a humanoid robotics project, which has been launched by Ministry of Economy, Trade and Industry (METI) of Japan from 1998FY to 2002FY for five years. The ability of the biped locomotion of HRP-2 is improved so that HRP-2 can cope with rough terrain in the open air and can prevent the possible damages to a humanoid robot's own self in the event of tipping over. The ability of whole body motion of HRP-2 is also improved so that HRP-2 can get up by a humanoid robot's own self even tough HRP-2 tips over. In this paper, the mechanisms and specifications of developed prototype humanoid robotics platform, and its electrical system are introduced.

For 3D walking control of a biped robot we analyze the dynamics of a 3D inverted pendulum in which motion is constrained to move along an arbitrarily defined plane. This analysis yields a simple linear dynamics, the 3D linear inverted pendulum mode (3D-LIPM). Geometric nature of trajectories under the 3D-LIPM and a method for walking pattern generation are discussed. A simulation result of a walking control using a 12-DOF biped robot model is also shown.

Biped robots have better mobility than conventional wheeled robots, but they tend to tip over easily. To be able to walk stably in various environments, such as on rough terrain, up and down slopes, or in regions containing obstacles, it is necessary for the robot to adapt to the ground conditions with a foot motion, and maintain its stability with a torso motion. When the ground conditions and stability constraint are satisfied, it is desirable to select a walking pattern that requires small torque and velocity of the joint actuators. We first formulate the constraints of the foot motion parameters. By varying the values of the constraint parameters, we can produce different types of foot motion to adapt to ground conditions. We then propose a method for formulating the problem of the smooth hip motion with the largest stability margin using only two parameters, and derive the hip trajectory by iterative computation. Finally, the correlation between the actuator specifications and the walking patterns is described through simulation studies, and the effectiveness of the proposed methods is confirmed by simulation examples and experimental results.

Since a biped robot tends to tip over easily, stable and reliable biped walking is a very important achievement. In this paper, we propose a balance control method based on an off-line planned walking pattern with real-time modification. First, a method of generating a highly stable, smooth walking pattern is presented. Then, a method of real-time modification consisting of body posture control, actual zero moment point control and landing time control based sensor information is proposed. By combining the proposed off-line walking pattern with real-time modification, the biped robot can walk smoothly and adapt to unknown environments. The effectiveness of the proposed method is confirmed by dynamic simulator such as walking on unexpected irregular rough terrain, soft ground and in environments in the presence of disturbances.

We propose and develop a novel type of manipulator for the minute work. It can not only independently control the position and orientation of the end-effector, but also control the translational motion along with the axis of end-effector by only one actuator in any orientation. By this mechanism, it is able to achieve a larger workspace with high precision comparing with the traditional proposed manipulator for minute work. From the result of measurement of accuracy for our prototype manipulator, it is shown that the error of the end-effector tip is within 50.0 /spl mu/m and repeated positioning error is within 2.0 /spl mu/m in the changing orientation process.

Biped robots have better mobility than conventional wheeled robots, but they tip over easily. In order to walk stably in various environments such as rough terrain, up and down slopes, or regions containing obstacles, it is desirable to adapt to such ground conditions with a suitable foot motion, and maintain the stability of the robot by a smooth hip motion. We propose a method to plan a walking pattern consisting of a foot trajectory and a hip trajectory. First, we formulate the constraints of a foot trajectory, and generate the foot trajectory by 3rd order spline interpolation. By setting the values of constraint parameters, it is easy to produce different types of foot motion. Then, we formulate a hip trajectory using a 3rd order periodic spline function, and derive the hip trajectory with high stability. Finally, the effectiveness of the proposed method is illustrated by simulation examples.

Since most conventional robots cannot easily be adapted to environments designed for humans, a human-size biped robot is expected to be able to play an important role in assisting human activities. The selection of suitable joint actuators is an important point when developing a human-size biped robot. In order to select suitable actuators and effectively utilize the selected actuators, it is necessary to clarify the relationship between walking patterns and the specifications of each joint actuator, and this is the issue tackled in the paper. First, a method of generating a high stability, smooth walking pattern is presented, and it is shown how various walking patterns can be produced by setting a series of defined walking parameters. Then, the dynamics of the robot, including the reaction force between the feet and the ground, are formulated. Finally, by simulation studies, the correlation found between actuator specifications and walking patterns is described, and the effectiveness of the proposed method is suggested.

A bilateral control system for scaled teleoperation provides the human operator with a feel of the task as well as the teleoperation between same-scale worlds. A maneuverability of the teleoperation system depends on the bilateral control scheme. This paper, first, reviews several bilateral control schemes for the scaled teleoperation, which have already been developed, and points out its dexterity issue of teleoperation. From these reviews with considering physical meaning of bilateral controllers, secondly, this paper proposes a novel bilateral control scheme that realizes macro-micro teleoperation with natural force feedback sensation. An idea of control scheme is come by taking notice that the system parameter values of master site and those of slave site are different. This control scheme is based on operational force feedforward type bilateral control with scaling gains. We also study the operational feeling of the proposed control scheme and compare with several bilateral control schemes in theory. Finally, we present experimental results that verify the validity of the proposed control scheme.

In the teleoperation between different-scale worlds, it is important to consider the scaling effect problem. An impedance shaping bilateral teleoperation that considers this problem is needed to provide the human operator with natural sensation while tele-manipulating objects in the micro world whose main physical characteristics are different from those in the macro world. In this paper, we propose a bilateral control scheme which provides the operator with an impedance shaped out of the real one. This control scheme is based on force feedback bilateral control with scaling transfer function gains. By choosing not only the geometrical scaling gains but also the dynamic scaling ones as the scaling transfer function gains, the impedance that is presented to the operator can be shaped out of the real one. Finally, we present experimental results that verify the validity of the proposed control scheme.

This paper presents repetitive and adaptive motion control schemes for rigid-link robot manipulators, when the manipulator's joint velocities cannot be measured by the control system. The control objective consists in tracking a prescribed desired trajectory. In the case of repetitive control, the desired trajectory is periodic and it is required that the robot achieve the control objective through repeated learning trials. We assume that the robot inverse dynamics are totally unknown, except that they can be represented by an integral of the product of known differentiable kernel and an unknown influence function. In the case of adaptive control, it is assumed that only the manipulator inertia parameters are unknown and that the desired trajectory jerks are available to the control system. In both control schemes, a velocity observer, which is formulated based on the desired input/output relation of the manipulator, is used to estimate the manipulator joint velocities. A stability analysis of the repetitive and adaptive control schemes with velocity estimation is presented. Simulation and experimental results show that the proposed repetitive control algorithm is successful in achieving the control objective without direct measurement of the joint velocities.

Identifying and implementing high fidelity scaling laws in scaled teleoperated systems is still a challenge. We propose the use of additional information (e.g., auditory and tactile) to complement and supplement the normal visual and force channels and thereby provide sensory enhancement when performing delicate tasks. We support our proposal by presenting experimental results from tests performed by humans on a hybrid hardware-software telemanipulation system. Our results show that integrating auditory and tactile feedback improved the performance of the operator.

Requirements for fast and accurate motion in industrial robot manipulators demand more advanced control techniques. Past techniques, such as the resolved acceleration method and nonlinear feedback control, etc. require detailed information on mechanical parameters. In these methods, the modelling errors adversely effect manipulator motion. To overcome this problem, this paper proposes a method for constructing nominal dynamic modelling for a robotic arm in the operational space. When the proposed method realizes a disturbance observer in the operational space, individual coordinate motions can be decoupled and independently controlled. Further, individual motion in the operational space coordinate is driven as if only nominally fixed mechanical dynamics in the operational space existed. As a result, the method enables one to construct the control law without any calibration for the mechanical parameters. Finally, the authors present experimental results from an implementation of the proposed method.>

Recent requirements for fast and accurate motion in industrial robot manipulators demand more advanced control techniques. For these requirements, many manipulator control methods have been developed. One of them is a manipulator control based on the disturbance observer. The disturbance observer estimates the disturbance torque (force) using a nominal model and compensates for the parameter variations between the real manipulator and the nominal model. Because of the high performance and simple algorithm, its usefulness for real time control the disturbance observer has recently been employed for manipulator control. This paper analyzes a manipulator control based on the disturbance observer. From this analysis, we also propose a design method of the manipulator control based on the disturbance observer. Finally, we present experimental results from an implementation of the proposed method.>