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In this paper, a new inverse kinematics strategy is proposed for avoiding deadlock caused by joint limits. The proposed method is a combination of the conventional numerical method for inverse kine...

In this paper, a new numerical method for inverse kinematics with prioritized multiple targets is proposed. The proposed method is constructed based on the virtual spring model and joint-based damp...

Cells sense the direction of mechanical stimuli including substrate stretching and show morphological and functional responses. The nuclear deformation with respect to the direction of mechanical stimuli is thought of as a vital factor in mechanosensitive intracellular signaling and gene transcription, but the detailed relationship between the direction of stimuli and nuclear deformation behavior is not fully solved yet. Here, we assessed the role of actin cytoskeletons in nuclear deformation caused by cell substrate stretching with different directions. Cells on a PDMS stretching chamber were subjected to a step-strain and changes of long- and short-axes of nucleus before and after stretching were evaluated in terms of nuclear orientation against the direction of stretching. Nuclei oriented parallel to the stretching direction showed elongation and shrinkage in the long and short axes, respectively, and vice versa. However, calculation of the aspect ratio (ratio of long- and short-axes) changes revealed orientation-depend nuclear deformation: The nucleus oriented parallel to the stretching direction showed a greater aspect ratio change than it aligned in the perpendicular direction of the stretching. A decrease in actin cytoskeletal tension significantly changed the nuclear deformation only in the short axis direction, thereby abolishing the orientation-depend deformation of the nucleus. These results suggest that lateral compressive forces exerted by the actin cytoskeleton is a key factor of orientation-depend deformation in short axis of the nucleus under the cell-substrate stretching condition, and may be crucial for mechano-sensing and responses to the cell-substrate stretching direction.

In this paper, a swimming robot capable of rapid turns not only horizontally but also vertically in an underwater environment is proposed. The robot utilizes a wire-driven continuum water jet nozzle, which can be oriented in an arbitrary direction and allows the robot to turn in a small radius. In this study, the deformation characteristics of the nozzle were first experimentally investigated, and the nozzle was then implemented in the robot. The performance of the robot was experimentally investigated in an underwater environment. The results indicated that it was capable of a high angular velocity, and could accomplish 180 degree turns within a tactical diameter that was smaller than its body length.

This paper describes the development of a three-degrees-of-freedom flapping-wing robot with a variable-amplitude link mechanism for controlling the lift and thrust forces acting on it. The variable-amplitude link mechanism comprises a lever-crank mechanism driven by a brushless DC motor and a linear actuator to control the amplitude of the flapping angle. The robot also comprises two DC motors with reduction gears for feathering and lead-lag motion. In our experiments, the measurement of force-torque revealed the effects of the motion of each wing. We found that the flapping-amplitude difference between the left and right wings causes a roll and yaw moment.

The human brain has excellent plasticity in terms of recovery from a stroke. It is expected that neurorehabilitation using an apparatus that applies robotic and virtual reality technology has rehabilitation training effects on stroke patients. Rehabilitation of the upper limbs consists of rehabilitation for shoulders and elbows, and rehabilitation of the fingers and wrists. Both rehabilitations are necessary to improve activities of daily living. Many rehabilitation systems for shoulders and elbows have been effective thus far. In this review, we introduce rehabilitation systems for the shoulders, elbows, and wrists of the upper limbs “PLEMO” series using force presentation technology with brakes. Rehabilitation systems using brakes are essentially safe unlike rehabilitation systems using actuators.

There are currently many quadruped robots suited to a wide range of applications, but traversing some terrains, such as vertical ladders, remains an open challenge. There is still a need to develop adaptive robots that can walk and climb efficiently. This paper presents an adaptive quadruped robot that, by mimicking feline structure, supports several novel capabilities. We design a novel paw structure and several point-cloud-based sensory structures incorporating a quad-composite time-of-flight sensor and a dual-laser range finder. The proposed robot is equipped with physical and cognitive capabilities which include: 1) a dynamic-density topological map building with attention model, 2) affordance perception using the topological map, and 3) a neural-based locomotion model. The novel capabilities show strong integration between locomotion and internal–external sensory information, enabling short-term adaptations in response to environmental changes. The robot performed well in several situations: walking on natural terrain, walking with a leg malfunction, avoiding a sudden obstacle, climbing a vertical ladder. Further, we consider current problems and future development.

Nuclear deformation caused by mechanical stimuli has been suggested to significantly impact various cellular activities, such as gene expression, protein synthesis and mechanotransduction. To understand how nuclear deformation regulates cellular behaviors, the details of intranuclear strain distribution caused by mechanical stimuli as well as intranuclear mechanical properties are required. Here, we examine local mechanical strains within the nucleus in a living cell subjected to substrate stretching and estimate the local nuclear mechanical properties. A HeLa cell in a PDMS chamber was subjected to a 10% step-strain by using a custom-made uni-axial stretching device. Local displacements and the distribution of the equivalent strain within the nucleus were obtained from fluorescence images of the nucleus before and after the application of stretching. The intranuclear strain showed heterogeneous distribution, and higher strain regions were observed not only at the center, but also periphery of the nucleus. We examined the role of the chromatin condensation level and actin cytoskeleton by treating cells with Trichostatin A and Cytochalasin D, respectively. Interestingly, these treatments did not cause significant changes in the intranuclear strain distribution. Referring to the experimental results, we reproduced the nuclear strain distribution in a finite element model to estimate relative distribution of Young's modulus within the nucleus, and observed substantially lower Young's modulus levels in the peripheral regions of the nucleus relative to those found in the central regions of the nucleus. We reveal heterogeneous strain distribution within the nucleus in a living cell subjected to substrate stretching, and the results provide insights into the importance of heterogeneity of intranuclear mechanical properties.

Robotic rehabilitation systems for upper limbs have been developed as two system types: active or passive. Active-type systems use actuators to provide users with varying degrees of force; in contrast, the force available from passive-type systems is limited, although these systems are safer to use. In this paper, a passive-type force display with redundant brakes is proposed to extend the displayable force region of the system. The kinematics and statics are derived, and the reaction force generated by brake torques is clarified. The displayable force region is analyzed in the simulation, and then the experiments are examined to verify the proposed analytical model.

In recent years, force display systems that supports rehabilitation of paralyzed patients have been developed and the effectiveness has been clarified. Force displays are classified into passive type and active type. A passive-type system using brakes has less risk of harming a user compared with an active-type system using motors. Therefore, passivetype system is safe and low cost, and can be used at home. In this paper, we develop a planar 2-DOF passive-type force display system with redundant powder brakes whose characteristics are experimentally obtained. Four configurations of brakes are illustrated. The tracing experiments are conducted to clarify the difference of haptic performance of them.

In recent years, it becomes popular to use robots that clean houses. In the future, it is expected that various robots having arm are used at home. But the robot arms used in factories are large and heavy, so it is difficult to use them at home. In this study, an expansion and contraction mechanism, which has a capability of portability and easiness of put-away, have been proposed and the robot arm have been developed using it. The previous robot arm was manually expanded and contracted. In this paper, we improved the robot arm so that can automatically expand and contract and have a wide movable range.

Recently, research on flapping robots inspired by the behavior of insects and birds has become a focus of attention in the fields of robotics and biomimetics. However, most flapping robots require an operator or an assistance device to take off. The goal of this study was to develop a flapping robot that can achieve self-takeoff without running and can be used like a drone. This paper describes the development and evaluation of the flapping robot developed with this aim. The developed robot can generate a thrust that exceeds its own weight with a simple flapping mechanism and a lightweight design. The airspeed was simulated using the thrust measured with a force sensor and the resistance coefficient estimated in a gliding experiment, and it was found to exceed the minimum airspeed required to achieve takeoff 0.3 s from the onset of flapping. The result of the takeoff experiment demonstrated that takeoff was possible if the initial pitch angle was high. However, the pitch angle decreased immediately after takeoff due to the pitching moment generated by the flapping motion. The moment on the tail wing was not enough for the robot to maintain a horizontal posture at low airspeeds during takeoff. It was concluded that the robot requires a control mechanism for the pitching moment generated by the flapping motion and/or accelerators that function without flapping during takeoff, such as hind limbs. Therefore, the parameters required for the design of actuated hind limbs were estimated.

This paper presents the novel capabilities of a quadruped robot by performing horizontal-vertical-horizontal movement transition through vertical ladder without handrailing supporter. To overcome the proposed problem, we propose a multi-behavior generation model using independent stepping and pose control in the quadruped robot. The model is able to generate appropriate behavior depending on external (3D point clouds) and internal sensors (ground touch sensor, and Inertial Measurement Unit). Posture condition, safe movement area, possible touchpoint, grasping possibility, and target movement are the information that is analyzed from the sensors. There are four options developed in behavior generation, which are, Approaching, Body Placing, Stepping, and Grasping behavior. In order to prove the effectiveness of the proposed algorithm, the model was implemented on the computer simulation and the real application. Before being applied in the real robot, the proposed model is optimized in the computer simulation. Then, the optimized parameter is used for applying in the real robot. As a result, the robot succeeded to move through the ladder without handrail from lower stair to upper stair. From the analysis, the body placing behavior is the most important strategy in the proposed case.

This paper presents a method with dynamic density topological structure generation for low-cost real-time vertical ladder detection from 3D point cloud data. Dynamic Density Growing Neural Gas (DD-GNG) is proposed to generate a dynamic density of the topological structure. The density of the structure and the number of nodes will be increased in the targeted object area. Feature extraction model is required to classify suspected objects for being processed in the next time process. After that, rungs of the vertical ladder is processed using an inlier-outlier method. Thus, the ladder detection model represents the ladder with a set of nodes and edges. Next, affordance detection is processed for detecting the feasible grasped location. To validate the effectiveness of the proposed method, a series of experiments are conducted on a 4-legged robot with a non-GPU board for real-time vertical ladder detection and climbing to validate the effectiveness of the proposed method. Results show that our proposed method able to detect and track the ladder structure in real-time with a much lower computational cost. The affordance of the ladder provides safety information for robot grasping.

[abstFig src='/00280001/01.jpg' width=""260"" text='PLEMO-P3 Developed by Furusho Lab at Osaka Univ.' ]We conducted many research and development activities on functional fluid mechatronics, rehabilitation systems, and servo drive systems. In this review, studies on the development of magnetorheological fluid devices, electrorheological effects of liquid crystalline polymers on one-sided pattern electrodes, and vibration control using control theory and liquid crystalline polymer are introduced. In addition, applications of rehabilitation systems for upper and lower extremities employing functional fluids for individuals suffering from stroke, cerebellar ataxia, and Guillain-Barre syndrome are also introduced.