Waist Mechanism Research Articles

Research on the design and control of an anthropomorphic waist structure for life support robots

AbstractIn the humanoid robots, waist mechanism is an important structure to realize the whole body coordinated movement. This paper proposes a series–parallel mechanism of waist structure, and its kinematics and dynamics characteristics are studied. Based on the dynamic model, a backstepping sliding mode controller is designed to simulate control performance. Under the continuous disturbance force, the stability and accuracy of the mechanism are verified. Compared with the experiment, the results prove that the waist mechanism has the biomimetic spine movements and desired control performance, which can be applied to life support robots in the future.

Design and optimization of a lightweight and compact waist mechanism for a robotic rat

A multi-degree-of-freedom (multi-DOF) waist mechanism is required for robotic rats to perform species-typical behaviors, but the existing waist mechanisms are heavy and cumbersome. To solve this problem, we propose a linkage-based slider-coupled symmetric swing (S3) mechanism, which features a single-input multiple-output structure, allowing it to couple multiple DOFs. The linkage mechanism has a variety of forms and linkage curves, making the S3 mechanism suitable for multiple-constraint optimization. Based on kinematic and dynamic analyses, we constrain the S3 mechanism in terms of bending angle, transmission angle, symmetry, and its existence, and then we optimize its dimensions using an interior-point method to make it compact. Compared with an existing waist mechanism, the proposed waist mechanism has only 47.8% of the weight and smaller dimensions, making it more lightweight and compact. Experiments on a robotic rat show that the proposed waist mechanism enables a robotic rat to perform rat-like upright rearing in 0.5s and tail grooming behavior in 0.4s, indicating its good biomimetic and dynamic performances. Comparisons between two generation robotic rats also reveal that the robot with new waist mechanism has similar (sometimes superior) pitching and bending abilities with the former one.

人間共存型ロボットの腰部と衝撃緩和機構の開発

Many conventional robots consisting of rigid frames and active joints have been controlled based on the information regarding collision avoidance in human environments. When these robots collide with a human, he/she can be seriously injured if their sensor systems have a defect or the power supplies are shut down. So, we have developed a human friendly robot that consists of two arms, a body, and a mobile base. It is covered by an air cushion bag which simulates the skin of a human. In this paper, its waist is described, which consists of pitch, roll, and yaw axes. Also, a passive collision force suppression mechanism that is installed in each joints of the human friendly robot is proposed. The passive collision force suppression mechanism consists of two fixed and linear guides, two compression springs, a release system, and a disk damper. When a collision between the robot and the environment occurs, collision/constant forces are first suppressed by the air cushion bag. If a larger collision force is exerted on the robot, the suppression mechanisms will become passively activated and the joints of the waist will disconnect. The robot, moreover, is capable of returning to a desired task by using the suppression mechanisms if the environment is cleared. Through collision experiments, the effectiveness of the waist mechanism and the suppression mechanism is verified.

슬라이딩 메커니즘을 이용한 서비스 로봇의 밸런싱 자세의 안정화에 대한 실험연구

This paper presents the analysis and control of the position of the COG (Center of Gravity) for a two-wheel balancing robot. The two-wheel balancing robot is required to maintain balance by driving two wheels only. Since the robot is not exactly symmetrical and its dynamics is changing with respect to moving parts, robust balancing control is difficult. Balancing performance becomes difficult when two arms hold a heavy object since the center of gravity is shifted out of the wheel axis. Novel design of a sliding waist mechanism allows the robot to react against the shift of the COG by moving the whole upper body to compensate for the imbalance of the mass as a counter balancer. To relocate the COG position accurately, the COG is analyzed by force data measured from two force sensors. Then the sliding COG mechanism is utilized to control the sliding waist position. Experimental studies are conducted to confirm the proposed design and method.

Robotic Waist Mechanism Driven by Dielectric Elastomer Actuators

This paper presented a waist mechanism driven by dielectric elastomer actuators (DEA), suitable for a small light robot. Unlike traditionally continuous range-of-motion actuators, DEA have only two discrete states, both of which are stable. As a result, waist mechanism has a finite number of states, but works like human waist and just need 36 switching values to control. Major benefits of the waist mechanism are that extensive feedback control is not required, task repeatability can be very high, and DEA are very inexpensive, thus resulting in low cost robots. The waist mechanism is attractive but needs further investigation before successful application.

2P1-F24 腰部関節を有するヤモリ型ロボットの強化学習に基づく歩行獲得

2P1-F24 腰部関節を有するヤモリ型ロボットの強化学習に基づく歩行獲得