Kunikatsu Takase

2008 Special Issue: Towards a general neural controller for quadrupedal locomotion

Our study aims at the design and implementation of a general controller for quadruped locomotion, allowing the robot to use the whole range of quadrupedal gaits. The controller design phase is carried out using simulation. This paper reports the simulation of steady walking at 0.6 m/s of both the forelegs only and the hind legs only (with a supporting structure at the back and at the front respectively), achieved using our quadrupedal model.

Assembly motion teaching system using position/force simulator - extracting a sequence of contact state transition

Since general automatic assembly motion planning using a geometric CAD model is computationally difficult, automation of a general assembly task is not feasible. However, if a human operator roughly specifies an assembly motion, the remainder of the process except for planning can be automated. We construct a teaching system for assembly tasks according to the above concept. This paper describes our teaching system for assembly tasks by using a position/force simulator. We show how to construct the position/force simulator and analyse the hybrid position/force control which is needed when dealing with general rotational motion. We show the example of extracting a sequence of contact state transitions from the motion which the operator performs in the position simulator of our system. The sequence of contact states automatically extracted from the motion shown by the operator makes it feasible to achieve an error-tolerant automated assembly motion. If a sequence of contact states is obtained, studies of the automatic assembly task system can progress based upon this information.

Assembly motion teaching system using position/force simulator-generating control program

We have developed a teaching system based on the assumption that the assembly task is a series of operations for achieving a target contact state among objects through changing their contact states. The features of our system are as follows: 1) teaching data for fine motion is extracted from a demonstration by an operator in a virtual world, 2) the operator can edit intermediate expressions on a display, 3) intermediate expressions can be used by any robot system with a skill library which has the ability to achieve the corresponding contact states. This paper describes the configuration of the system, program generation using intermediate expressions and a skill library to achieve each contact state.

Multioperator teleoperation of multirobot systems with time delay: part I--aids for collision-free control

In this paper, various coordinated control schemes are explored in Multioperatormultirobot (MOMR) teleoperation through a communication network with time delay. Over the past decades, problems and several notable results have been reported mainly in the Single-OperatorSingle-Robot (SOSR) teleoperation system. Recently, the need for cooperation has rapidly emerged in many possible applications such as plant maintenance, construction, and surgery, because multirobot cooperation would have a significant advantage over a single robot in such cases. Thus, there is a growing interest in the control of multirobot systems in remote teleoperation, too. However, the time delay over the network would pose a more difficult problem to MOMR teleoperation systems and seriously affect their performance. In this work, our recent efforts devoted to the coordinated control of the MOMR teleoperation is described. First, we build a virtual experimental test bed to investigate the cooperation between two telerobots in remote environments. Then, different coordinated control aids are proposed to cope with collisions arising from delayed visual feedback from the remote location. To verify the validity of the proposed schemes, we perform extensive simulations of various planar rearrangement tasks employing local and remote graphics simulators over an ethernet LAN subject to a simulated communication delay.

Internet-Based Robotic System Using CORBA as Communication Architecture

In this paper, we propose the Internet-based robotic system that uses Common Object Request Broker Architecture (CORBA) to implement networking connections between a client and a remote robotic system. The client can transparently invoke a method on a server across the network without any need to know where the application servers are located, or what programming language and operating system are used. This lets the system overcome the shortcomings of the other typical Internet robotic system. To cope with time delays on the communication path, we have implemented the robot control server, which allows the user to control the telerobotic system at a task-level. We have also implemented the live image feedback server, which provides live image feedback for a remote user. The proposed system gives the users the ability to operate the remote robotic system to retrieve and manipulate the desired tableware or other things to support the aged and disabled over the Internet by using the intuitive user interface.

Adaptive dynamic walking of a quadruped robot 'Tekken' on irregular terrain using a neural system model

We have induced a quadruped robot to walk with medium walking speed on irregular terrain based on biological concepts. The PD-controller at joints constructs the virtual spring-damper system as the visco-elasticity model of a muscle. The neural system model consists of a CPG (central pattern generator) and reflexes. A CPG receives sensory input and changes the period of its own active phase. The desired angle and P-gain of each joint in the virtual spring-damper system is switched based on the phase signal of the CPG. CPGs, the motion of the virtual spring-damper system of each leg and the rolling motion of the body are mutually entrained through the rolling motion feedback to CPGs, and can generate adaptive walking. We report our experimental results of dynamic walking on terrains of medium degrees of irregularity in order to verify the effectiveness of the designed neuro-mechanical system.

A rehabilitation walker with standing and walking assistance

This paper proposes a robotic walker system with standing and walking assistance function. Our system focuses on domestic use for aged person who needs nursing in their daily life. Our key ideas are two topics. The first topic is combination of standing assistance function and walking assistance function. In previous works, many assistance devices are specialized in only ldquostanding-up operationrdquo or ldquowalking operationrdquo. However, in their daily life, elderly person needs standing, walking and seating assistance continuously by a same device. Our developing assistance system can support both operations by a small sized mechanism with low cost for domestic use. The second topic is steady standing assistance operation using an assistance manipulator and an active walker. In order to use the remaining physical strength of the patient, it is required to maintain the patientpsilas body posture which enables him to use own strength easily. According to the patientpsilas posture during standing up, our proposed system selects more appropriate device and controller, and realizes the standing assistance with steady posture of the patient based on the nursing specialists. The performance of our proposed system is verified by experiments using our prototype.

Three-dimensional adaptive dynamic walking of a quadruped - rolling motion feedback to CPGs controlling pitching motion

We attempt to induce a quadruped robot to walk dynamically on irregular terrain by using a neural system model consisting of a central pattern generator (CPG) and reflexes. In this paper, we report on a newly developed quadruped robot, which contains a mechanism designed to make adaptive 3D space walking (pitch, roll and yaw planes) on irregular terrain be performed more simply. In 3D walking, a rolling motion is naturally generated in most gaits. By having the rolling motion be the standard oscillation and making the CPGs of the legs be entrained with a rolling motion, we realized the stabilization of the gait at a constant walking speed, in spite of an unbalanced gravity load between the fore and hind legs. We also realized an autonomous gait transition in changing walking speeds, by utilizing such rolling motion feedback to CPGs, in order to reduce energy consumption. Rolling motion feedback to CPGs contributes to gait stabilization in walking on an irregular terrain as a tonic labyrinthine reflex for rolling. At present stage, the robot succeeded in walking over several 2D irregular terrains by using CPGs, a flexor reflex and tonic labyrinthine reflexes for pitching and rolling.

Towards 3D adaptive dynamic walking of a quadruped robot on irregular terrain by using neural system model

We are trying to induce a quadruped robot to walk dynamically on irregular terrain by using a neural system model. In our previous study, we integrated several reflexes into a CPG (central pattern generator) and realized adaptive 2D walking on terrain of medium degree of irregularity. In this paper, in order to make the role of a CPG be clear, we investigate the relation between parameters of a CPG and the mechanical system by simulations and experiments. In addition, we show a newly developed quadruped robot, of which mechanism is designed to make adaptive 3D walking on irregular terrain be realized more simply. At this moment, 3D walking on flat terrain is realized by using a neural system model consisting of CPG and reflexes.

Remote collaboration through time delay in multiple teleoperation

In this paper, remote robot collaboration using a network with communication time delay is discussed in multi-operator-multi-robot (MOMR) teleoperation. Recently, collaboration tasks have rapidly emerged in many possible applications such as plant maintenance, construction, and surgery, because multi-robot collaboration would have a significant advantage over a single robot in such cases. Problems and several noticeable results have been reported in a single-operator-single-robot (SOSR) teleoperation system. However, the effect of time-delay would pose a more difficult problem to the MOMR teleoperation systems and seriously affect their performance. In this work, first, some of the constraints on performance in MOMR teleoperation applications are examined. Then, the time-delay effects on tele-collaboration are investigated through several experimental studies. Finally, a method to cope with the time-delay in MOMR teleoperation systems is proposed exploiting the virtual thickness modification scheme.