다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The backdrivability of joints is a critical requirement for the robots that perform tasks in uncertain environments. While series elastic actuators are intrinsically backdrivable, their control bandwidth is limited by the low resonant frequency of the elastic component. To simultaneously realize both of the backdrivability and high control bandwidth, Electro-Hydrostatic Actuator (EHA) is a solution. Based on this idea, we developed the fully electro-hydrostatically driven humanoid robot Hydra, while its evaluation was limited to the joint level one. In this paper, we present evaluations of its whole-body control performance, including locomotion. This is the first time to report a bipedal locomotion by an EHA driven humanoid. We first confirm that Hydra can realize a position feedback control with enough stiffness to realize a position control based locomotion. Secondly, we show that the joint backdrivability can suppress the effect of a disturbance applied to the distal part of the robot on the whole-body motion. As the result, we realized a torque control based locomotion with both a proper COM stabilization and nulls pace compliance.

Compliant Biped Locomotion of Hydra, an Electro-Hydrostatically Driven Humanoid

In this paper, we developed a compact pump reinforced by ceramics structure. In order to reduce the internal leakage, we developed a ceramics reinforcer for the pump-casing to suppress the deformation of the casing under high pressure, and devised the structure using bearing balls which can adjust the gap between the gear and the casing precisely. To evaluate the internal leakage, we used the internal leakage resistance which indicate the difficulty of internal leakage. Internal leakage resistance of developed pump is 3.39 × 1013Pa·s/m3 which means that the internal leakage loss of developed pump is 1/2.8 times that of previously developed pump.

Design and Development of Compact Ceramics Reinforced Pump with Low Internal Leakage for Electro-Hydrostatic Actuated Robots

Electro-hydrostatic actuator (EHA) has backdrivability and is suitable for a robot system that cooperates with human However, its design methodology to miniaturize and to generate high pressure ha

Development of 3-DOF wrist mechanism for electro-hydrostatically driven robot arm

Actuation systems for robots and other machines used in critical applications is an area that requires further research. In such applications, a machine works in a human environment and physically interacts with humans. Reliability and backdrivability are still insufficient in current systems. An electro-hydrostatic actuator has the potential advantage of high reliability by nature and high backdrivability in mechanical simplexity when it is designed to be small and light. This study provides a theoretical investigation of the methods for evaluating internal leaks and other mechanical losses, such as Coulomb and viscous friction, and experimentally evaluates two types (trochoid and involute gear) of prototyped hydraulic pumps.

Experimental Study on Critical Design of Electro-Hydrostatic Actuators Small in Size and Light in Weight

In this research, we suggest a method to reduce the loss of the pump aiming to develop small and high-pressure pump for EHA. To reduce the loss of the pump, we focused on the internal leakage loss and the viscous friction loss. We formulated each loss and found that it is effective for loss reduction to make gaps inside the pump narrower and increase the discharge amount per 1 rad making the radius of the gear small. Based on the above, we developed the improved involute external gear pump. Compared with conventional trochoid pump, the internal leakage loss of developed pump is reduced by 22.4% at 10MPa and the viscous friction loss is reduced by 85.6% at 10MPa. Also, there is a problem that internal leakage increases when the internal pressure becomes high. This problem is caused by the deformation of the pump-casing under high pressure. We developed highly rigid ceramics-casing to reduce the increase of the internal leakage. Compared with the pump using aluminum-casing, the pump using ceramics-casing reduced 56.2% in internal leakage loss when the internal pressure increased from 3MPa to 6MPa.

Mituso Komagata

Papers

Small Size Hydraulic Pumps with Low Heat Generation for Electro Hydrostatic Actuation of Humanoid Robots