Tomohito Takubo

Developmental Process of a Chopstick-Like Hybrid-Structure Two-Fingered Micromanipulator Hand for 3-D Manipulation of Microscopic Objects

The development of a chopstick-like two-fingered micromanipulator based on a hybrid mechanism is presented. The microhand consists of two 3-prismatic-revolute-spherical (PRS) parallel modules connected serially in a mirror image style. Each module has a long glass pipette as an end effector. The development process consists of three phases. In the first phase, analysis and mathematical modeling, a novel solution of the inverse kinematics problem (IKP) of a 3-revolute-prismatic-spherical (RPS) parallel module, is derived and applied with proper modification to the case of 3-PRS of the proposed mechanism. The solution is extended to the two-fingered hybrid mechanism of the microhand. In the optimization and design phase, the optimization of the chosen design parameters of a theoretical 3-PRS parallel module is carried out using two approaches: discretization method and genetic algorithms. Based on the optimal design parameters, a CAD model of the 3-PRS finger module is built, and a complementary optimization step using the ANSYS Workbench program is carried out to determine suitable characteristics of the pin flexure hinge. Finally, the total CAD model of the two-fingered hand is built. In the realization and implementation phase, the description of the hardware system of the two-fingered microhand prototype is presented. The program description, calibration method, practical Jacobian matrices, practical workspace, and error analysis of the prototype are discussed.

Pushing an Object Considering the Hand Reflect Forces by Humanoid Robot in Dynamic Walking

This paper discusses pushing a heavy object by a humanoid robot. We modify the whole body motion considering the hand reflecting forces for the walking pattern of a humanoid robot. By assuming that linear and angular momentum of a humanoid robot are calculated, we define the projection of the Center of the Mass(CoM) as” Dynamically Complemental Zero Moment Point(DCZMP)”, when external forces act to the end-effectors. We propose a new method using the DCZMP for the modification control of CoM position with balancing control. The robot can keep the dynamical balance considering the DCZMP and the walking velocity in both single and double support phase. In addition, for controlling pushing force, we implement an impedance controller with the manipulation and walking velocity controller. The effectiveness of the proposed method is confirmed by simulations and experiments.

Assist system for carrying a long object with a human-analysis of a human cooperative behavior in the vertical direction

Deals with an assist system for carrying a long object with a human operator. When we carry such an object, we often grasp both ends and move it cooperatively. Our purpose is to establish how to design the assist system which can achieve such a task. It is difficult to apply conventional control laws. On the other hand, humans can achieve such a task. Therefore, we measure the human cooperative behaviors and analyze them to find the cooperative rules. Based on the rules, we propose a control law of the assist system. Furthermore, we construct a prototype system and verify the validity of the control law.

Omni-directional Gait of Limb Mechanism Robot Hanging from Grid-like Structure

A method for limb mechanism robots of omni-directional gait hanging from grid-like structure is proposed. Grid-like structure consists of many bars assembled in a matrix in a horizontal plane; its grid spacing is not always constant and unknown. A robot has six legs, and each foot has a hemispherical shape for hooking on the bar. The robot moves in any direction as commanded by tripod gait; it hangs from the grid-like structure using two sets of three legs alternately. The leg gropes for the bar so as to take as long stroke as possible. By increasing joint compliance, the foot contacts the bar softly and detects the contact. Then, using a foot force sensor, the robot ascertains that the foot hooks on the bar. The developed robot ASTERISK can perform omni-directional gait hanging from experimental grid-like structure by the proposed method

Rough terrain walking for bipedal robot by using ZMP criteria map

A new method for bipedal walking on rough terrain by using ZMP criteria map is proposed. The rough terrain walking is classified to “step up” and “step down” by landing timing of a swing leg. The walking pattern is modified in real-time according to the difference between the ideal timing and the measured timing by a force sensor on the foot. In the case of “step up”, the landing timing is faster than the ideal, and the swing leg trajectory should be change to follow the step so that the ZMP based balance of the sudden caused double support phase is kept. In the case of “step down”, the landing timing is later than the ideal, and the swing leg trajectory should be change to seek the ground so that the balance of the unknown future double support phase is kept. The modified walking pattern is decided based on the ZMP criteria map. The ZMP criteria map can indicate a safe landing timing and landing position of a swing leg. By referring the ZMP criteria map, the robust walking pattern can be planned. The proposed method is implemented to HRP-2, and the effectiveness is confirmed through experiments.

HUMAN–ROBOT COLLISION AVOIDANCE USING A MODIFIED SOCIAL FORCE MODEL WITH BODY POSE AND FACE ORIENTATION

The ability of robots to understand human characteristics and make themselves socially accepted by humans are important issues if smooth collision avoidance between humans and robots is to be achieved. When discussing smooth collision avoidance, robot should understand not only physical components such as human position, but also social components such as body pose, face orientation and proxemics (personal space during motion). We integrated these components in a modified social force model (MSFM) which allows robots to predict human motion and perform smooth collision avoidance. In the modified model, short-term intended direction is described by body pose, and a supplementary force related face orientation is added for intention estimation. Face orientation is also the best indication of the direction of personal space during motion, which was verified in preliminary experiments. Our approach was implemented and tested on a real humanoid robot in a situation in which a human is confronted with the robot in an indoor environment. Experimental results showed that better human motion tracking was achieved with body pose and face orientation tracking. Being provided with the face orientation as an indication of the intended direction, and observing the laws of proxemics in a human-like manner, the robot was able to perform avoidance motions that were more human-like when compared to the original social force model (SFM) in a face-to-face confrontation.

New Architecture of a Hybrid Two-Fingered Micro–Nano Manipulator Hand: Optimization and Design

This paper presents the synthesis and design optimization of a compact and yet economical hybrid two-fingered micro–nano manipulator hand. The proposed manipulator hand consists of two series modules, i.e., an upper and lower modules. Each of them consists of a parallel kinematics chain with a glass pipette (1 mm diameter and 3–10 cm length) tapered to a very sharp end as an end-effector. It is driven by three piezo-electric actuated prismatic joints in each of the three legs of the parallel kinematics chain. Each leg of the kinematics chain has the prismatic–revolute–spherical joint structure. As the length of the glass pipette end-effector is decreased, the resolution and accuracy of the micro–nano manipulator hand is increased. For long lengths of the glass pipette end-effector, this manipulator works as a micro manipulator and for short lengths it works as a nano manipulator. A novel closed-form solution for the problem of inverse kinematics is obtained. Based on this solution, a simulation program has been developed to optimally choose the design parameters of each module so that the manipulator will have a maximum workspace volume. A computer-aided design model based on optimal parameters is built and investigated to check its workspace volume. Experimental work has been carried out for the purpose of calibration. Also, the system hardware setup of the hybrid two-fingered micro–nano manipulator hand and its practical Jacobian inverse matrices are presented.

Stair recognition with laser range scanning by limb mechanism robot “ASTERISK“

A stair recognition with laser range scanning for continuous stair climbing by limb mechanism “ASTERISK” is proposed. In this research, laser range scanning is divided into rough scan for fast scanning, and precise scan for range scanning. We use 2D laser range finder attached with motor for 3D laser range scanning. As a result of the experiment, the robot could recognize a stair position and posture even it is located at the physical limitation of laser range finder which is 4 m and detect the actual stair up to 6 out of 10 steps which the height is about 5 times of “ASTERISK” normal posture standing height.

Emergent walking stop using 3-D ZMP modification criteria map for humanoid robot

Real-time emergent stop walking motion is necessary for humanoid robots. We propose a new emergent stop method using modification criteria map. The stable gait change is generated by adjusting the amount of the ZMP modification according to the timing of stop command. The modified ZMP trajectory is given so that the humanoid robot can change the current motion without falling down. The modification criteria are defined from the relation between the predicted ZMP trajectory using a preview controller and the support polygon. The preview controller employs table-cart model and it derives center of mass (CoM) trajectory from ZMP reference in real-time. We make the map of relation among the ZMP modification length, the modification timing and the timing of the stop command for stable gait modification. The robot can execute the best motion referring to the predefined map. In this method, the humanoid robot can stop immediately within one step or zero step to avoid a collision, if humans or objects appeared unexpectedly in front of the walking humanoid robot. The stop motion is typically divided two phase: single leg support phase and double leg support phase. In the single leg support phase, the next landing position and timing are decided according to command time of the stop signal. In the double leg support phase, the humanoid robot can stop anytime without changing standing position. The validity of the proposed method is confirmed by experiment using a humanoid robot HRP-2.

Vision-Based Automated Single-Cell Loading and Supply System

Automated continuous individual cell transfer is a critical step in single-cell applications using microfluidic devices. Cells must be aspirated gently from a buffer before transferring to operation zone so as not to artificially perturb their biostructures. Vision-based manipulation is a key technique for allowing nondestructive cell transportation. In this paper, we presented a design for an automated single-cell loading and supply system that can be integrated with complex microfluidic applications for examining or processing one cell at a time such as the current nuclear transplantation method. The aim of the system is to automatically transfer mammalian donor (~ 15 ¿m) or oocyte (~ 100 ¿ m) cells one by one from a container to a polydimethylsiloxane (PDMS) microchannel and then transport them to other modules. The system consists of two main parts: a single-cell suction module, and a PDMS-based microfluidic chip controlled by an external pump. The desired number of vacuumed cells can be directed into the microfluidic chip and stored in a docking area. From the batch, they can be moved to next module by activating pneumatic pressure valves located on two sides of the chip. The entire mechanism is combined with monitoring systems that perform detection/tracking and control.