Hisashi Osumi

Development of a manipulator suspended by parallel wire structure

A control method of positioning a serial link manipulator suspended by a crane type robot with multiple wires is proposed. The manipulator is fixed on a base plate suspended by three wires. Since the manipulator is suspended by wires, the position and orientation of the base may change according to external forces applied to the manipulator or the change of the manipulator pose. Thus, the inverse kinematics becomes very complicated, and moreover, the mechanism does not seem to be suitable for tasks requiring manipulator tip forces. In this paper, it is shown that the inverse kinematics becomes very simple by using a redundant DOF manipulator, and a method of exploiting the manipulator for tasks requiring forces is described.

Cooperative control between two position-controlled manipulators

This paper proposes a simple method for handling a single object by cooperation of two manipulators controlled by PID position controllers. Flexibility is essential to avoid excessive inner forces caused by the mutual positioning error between two manipulators. First, the way to design these flexible mechanisms is shown. Second, the closed loop structure consisting of two manipulators and the installed flexible mechanisms is kinematically analyzed. As an example, a cooperative system between a 6-DOF robot and a conventional crane is designed and an inverse kinematics algorithm is proposed. The method proposed here is also very effective for cooperation in distributed autonomous robotic systems.<<ETX>>

Development of Autonomous System for Loading Operation by Wheel Loader

An outline of the developed system for autonomous loading operation by wheel loader will be described. The system consists of three sub-systems: (1) Environment measuring and modeling, (2) Planning and (3) Motion control. The environment measuring sub-system measures 3D shape of the environment by stereo-vision system. The shape of the pile is converted into the environment models. The planning sub-system determines the position and direction of scooping on the pile based on the environment models. It generates the V shape path between the scooping point and the loading point as well. The motion control sub-system controls actuators on the loader based on the reference values from the planning sub-system in traveling on the V shape. However the motion of the bucket at scooping is controlled based on the resistance force applied on the bucket during scooping motion. The developed system is installed on an experimental small size scale model in lab and on a real wheel loader in the experimental field.

Cooperative control of multiple mobile manipulators on uneven ground

We have proposed a simple method for carrying a large object by cooperation of multiple mobile manipulators with position controllers. Manipulators on mobile platforms are used as free joint mechanisms by locking some joints and making the rest joints free. These free joints play the role of mechanical compliance in order to avoid excessive inner forces due to the mutual positioning errors. We discuss how to determine feedback control laws for cooperation of mobile platforms on uneven ground. First, compliance needed for cooperation among position-controlled robots, the statics and error characteristics of cooperative systems including compliant mechanisms are reviewed. Second, three feedback control laws for platforms moving on uneven ground are proposed and their control performance is investigated. After additional improved control laws are proposed, the proposed control laws are used for a prototype cooperative system consisting of three moving tables driven by ball screws and the effectiveness of the proposed law is verified.

Trajectory arrangement based on resistance force and shape of pile at scooping motion

As a part of research on autonomous loading system by wheel loader, a method for appropriate arrangement of bucket trajectory for scooping motion will be proposed. In this paper, relation between resistance force and advancing direction of the bucket is analyzed theoretically. Advancing direction is dominant factor for resistance force on the bucket during scooping. Based on this analysis, simple rules for bucket trajectory arrangement are proposed. In scooping procedure, scooped volume is estimated using 3D model obtained with stereo-vision system. The shape of the pile is measured and converted into pile model prior to scooping. The developed method and system are installed on experimental scale model of wheel loader. The results show good performance for different condition of pile.

Development of an orthosis for walking assistance using pneumatic artificial muscle: A quantitative assessment of the effect of assistance

In recent years, there is an increase in the number of people that require support during walking as a result of a decrease in the leg muscle strength accompanying aging. An important index for evaluating walking ability is step length. A key cause for a decrease in step length is the loss of muscle strength in the legs. Many researchers have designed and developed orthoses for walking assistance. In this study, we advanced the design of an orthosis for walking assistance that assists the forward swing of the leg to increase step length. We employed a pneumatic artificial muscle as the actuator so that flexible assistance with low rigidity can be achieved. To evaluate the performance of the system, we measured the effect of assistance quantitatively. In this study, we constructed a prototype of the orthosis and measure EMG and step length on fitting it to a healthy subject so as to determine the effect of assistance, noting the increase in the obtained step length. Although there was an increase in EMG stemming from the need to maintain body balance during the stance phase, we observed that the EMG of the sartorius muscle, which helps swing the leg forward, decreased, and the strength of the semitendinosus muscle, which restrains the leg against over-assistance, did not increase but decreased. Our experiments showed that the assistance force provided by the developed orthosis is not adequate for the intended task, and the development of a mechanism that provides appropriate assistance is required in the future.

Cooperative strategy for multiple mobile manipulators

This paper proposes a simple method for carrying a large object by cooperation of multiple mobile manipulators with position controllers. It is necessary for each robot to have compliance in order to avoid excessive inner forces due to the mutual positioning errors. Thus manipulators on mobile platforms are used as free joint mechanisms by locking some joints and making the rest joints free. These free joints play the role of mechanical compliance. First, compliance needed for cooperation among position-controlled robots is shown. Second, the statics and error characteristics of cooperative systems including compliant mechanisms are analyzed. Some feedback control laws for platforms moving on rough ground are proposed and discussed.

Positioning of wire suspension system using CCD cameras

A sensor system for measuring tilting angles of a wire which suspends a swinging mass is developed. Two CCD cameras are placed toward the wire on a horizontal plane, and obtain the images of the moving wire respectively. Through the simultaneously obtained two wire images, the angles between the wire and a vertical line are calculated. By feedback control using wire angles measured by the developed sensor, a mass suspended by a two dimensional crane on a horizontal plane is positioned without residual vibration at a target point. Since the developed sensor system is placed near the upper end of the wire regardless of wire length, it is easy to install the developed system in conventional cranes. By using this sensor system, it is expected to automate heavy object positioning, handling and so on.

Time optimal control for quadruped walking robots

Time optimal control method for quadruped walking robots are developed and installed into a practical robot system. Each leg is modeled as a two link manipulator whose time optimal control theory has already been established by Bobrow. However, in legged robot systems, each leg supports their body weight, and the reaction forces from its ground must be inside of their friction corn. Moreover, the ZMP (zero moment point) of the robot is constrained for stable walk. Therefore, time optimal control inputs must be designed considering these constraints. SONY ERS-7 is used as a quadruped walking robot and a fundamental experiment is done. From the experimental results, the effectiveness of the developed control algorithm is verified

Cooperative system for multiple position-controlled robots with free joint mechanisms

This paper proposes a simple method for handling objects by cooperation of multiple position-controlled robots. In order to use position controllers for cooperation of multiple robots, it is necessary to install mechanical compliance in each robot to avoid excessive inner forces due to the mutual positioning errors. First, the compliance needed for the cooperation of position-controlled robots is reviewed. Using compliant mechanisms with free joints, cooperative control system between two industrial robots are developed. As the cooperative system with mechanical compliance has kinematic redundancy, a way to use the redundancy is proposed. Some fundamental experiments verify the effectiveness of the proposed strategy.