Passive Linkage Mechanism Research Articles

Vibration isolation with passive linkage mechanisms

This study is to present a novel way to achieve superior passive vibration isolation by employing a specially designed and compact linkage mechanism. The proposed anti-vibration system has beneficial nonlinear inertia, inspired by swinging motion of human arms, and is constructed with an adjustable nonlinear stiffness system inspired by animal or human leg skeleton. It is shown with comprehensive theoretical analysis and consequently validated by a series of well-designed experiments that the nonlinear stiffness, nonlinear damping and nonlinear inertia of the proposed system are very helpful for significantly reducing resonant frequency and enhancing damping effect in a beneficial nonlinear way. This results in excellent vibration isolation performance with lower resonant frequency and resonant peak of faster decay rate. This study provides an innovative solution to a cost-efficient vibration control demanded in various engineering systems.

Terrain-surface Estimation from Body Configurations of Passive Linkages

A passive linkage mechanism is used for increasing the mobile performance of a wheeled vehicle on uneven ground. The mechanism changes its shape according to the terrain and enables all the wheels to remain grounded while the vehicle operates over rough terrain. This means that the shape of the passive linkage mechanism must correspond to that of the terrain surface, so that the vehicle can estimate the shape of the surface while passing over it. This paper proposes a new terrain-surface estimation scheme that uses a passive linkage mechanism. Our key concept is to enable changes in the vehicle body's configuration to correspond to those in the terrain's shape. Using this concept, our mobile platform estimates the shape of terrain surfaces without using external sensors; the estimated surface shapes are used to adjust the reference velocities of individual wheels, thereby improving the mobile performance of the vehicle. We test our proposed scheme by experiments using a prototype vehicle.

Zebedee: Design of a Spring-Mounted 3-D Range Sensor with Application to Mobile Mapping

Three-dimensional perception is a key technology for many robotics applications, including obstacle detection, mapping, and localization. There exist a number of sensors and techniques for acquiring 3-D data, many of which have particular utility for various robotic tasks. We introduce a new design for a 3-D sensor system, constructed from a 2-D range scanner coupled with a passive linkage mechanism, such as a spring. By mounting the other end of the passive linkage mechanism to a moving body, disturbances resulting from accelerations and vibrations of the body propel the 2-D scanner in an irregular fashion, thereby extending the device's field of view outside of its standard scanning plane. The proposed 3-D sensor system is advantageous due to its mechanical simplicity, mobility, low weight, and relatively low cost. We analyze a particular implementation of the proposed device, which we call Zebedee, consisting of a 2-D time-of-flight laser range scanner rigidly coupled to an inertial measurement unit and mounted on a spring. The unique configuration of the sensor system motivates unconventional and specialized algorithms to be developed for data processing. As an example application, we describe a novel 3-D simultaneous localization and mapping solution in which Zebedee is mounted on a moving platform. Using a motion capture system, we have verified the positional accuracy of the sensor trajectory. The results demonstrate that the six-degree-of-freedom trajectory of a passive spring-mounted range sensor can be accurately estimated from laser range data and industrial-grade inertial measurements in real time and that a quality 3-D point cloud map can be generated concurrently using the same data.

Simultaneous Optimization of Robot Structure and Control System Using Evolutionary Algorithm

The simultaneous optimization of a robot structure and control system to realize effective mobility in an outdoor environment is investigated. Recently, various wheeled mechanisms with passive and/or active linkages for outdoor environments have been developed and evaluated. We developed a mobile robot having six active wheels and passive linkage mechanisms, and experimentally verified its maneuverability in an indoor environment. However, there are various obstacles in outdoor environment and the travel ability of a robot thus depends on its mechanical structure and control system. We proposed a method of simultaneously optimizing mobile robot structure and control system using an evolutionary algorithm. Here, a gene expresses the parameters of the structure and control system. A simulated mobile robot and controller are based on these parameters and the behavior of the mobile robot is evaluated for three typical obstacles. From the evaluation results, new genes are created and evaluated repeatedly. The evaluation items are travel distance, travel time, energy consumption, control accuracy, and attitude of the robot. Effective outdoor travel is achieved around the 80th generation, after which, other parameters are optimized until the 300th generation. The optimized gene is able to pass through the three obstacles with low energy consumption, accurate control, and stable attitude.

2A2-E14 車輪型移動ロボットのための環境認識システム : 第4報:自己組織化テンプレート作成手法の導入

Recently, various mechanism have been developed combining linkage mechanisms and wheels, especially, the combination of passive linkage mechanisms and small wheels is one of main research trends, because, standard wheeled mobile mechanisms have difficulties on rough terrain movements. In our research, a 6-wheeled mobile robot employing a passive linkage mechanism has been developed to enhance maneuverability and achieved climbing capability over a 0.20[m] height of bump. In this paper, we propose environment recognition system for wheeled mobile robot which consists of multiple classification analyses like self-organizing map, and image processing for self-localization.

Omni‐directional vehicle control based on body configuration

PurposeThe purpose of this paper is to develop a new wheel control scheme for wheeled vehicle with passive linkage mechanism which realizes high step‐overcoming performance.Design/methodology/approachDeveloping wheeled vehicle realizes omni‐directional motion on flat floor using special wheels and passes over non‐flat ground using the passive suspension mechanism. The vehicle changes its body shape and wheel control references according to ground condition when it runs over the rough terrain.FindingsUtilizing the proposed wheel control scheme, the slip ratio and the disturbance ratio of the wheel reduce when the vehicle passes over the step and its step‐overcoming performance is improved.Originality/valueThe paper's key idea is modification of its kinematic model referring to the body configuration dynamically and using this model for wheel control of the vehicle. The controller adjusts the wheel control references when the vehicle passes over the rough terrain changing the body shape and reduces the slippage and the rotation error of wheels.

2A2-E11 動力学シミュレーションと進化型アルゴリズムを用いた不整地移動ロボットの構造最適化

A wheeled mobile mechanism with a passive and/or active linkage mechanism for travel in rough terrain is developed and evaluated. In our previous research, we developed a wheeled mobile robot which has six wheels and a passive linkage mechanism, and its maneuverability was experimentally verified. The ability to climb over a 0.20 m high bump, which is twice the height of the wheel diameter of 0.10 m, was achieved; and the mobile robot can climb up 0.15 m high continuous steps. In this research, we optimized the mobile robot linkage mechanisms and controller parameters by evolutionary algorithm and Open Dynamics Engine in numerical simulations. In simulations, though the default parameter mobile robot could climb up the 0.20 m high bump, it could not achieve climbing up the two kinds of stairs. On the other hand, the best parameter mobile robot could climb up the three kinds of typical environments.

Environment Recognition System Based on Multiple Classification Analyses for Mobile Robots

Various mechanisms have recently been developed that combine linkage mechanisms and wheels. In particular, the combination of passive linkage mechanisms and small wheels is a main research trend because standard wheeled mobile mechanisms find it difficult to move on rough terrain. In our previous research, a six-wheel mobile robot employing a passive linkage mechanism has been developed to enhance maneuverability and was able to climb over a 0.20 m bump and stairs. We designed a hybrid velocity and torque controller using a neural network since simple velocity controllers fail to climb up. In this paper, we propose an environment recognition system for a wheeled mobile robot that consists of multiple classification analyses to make the robot more adaptive to various environments by selecting a suitable system such as decision making, navigation and controller using the result of the environment recognition system. We evaluate the recognition performance in operation environments; slopes, bumps and stairs by comparing principle component, k-means and self-organizing map analyses.

A Controller Design Method Based on a Neural Network for an Outdoor Mobile Robot

A wheeled mobile mechanism with a passive and/or active linkage mechanism for travel in rough terrain is developed and evaluated. In our previous research, we developed a switching controller system for wheeled mobile robots in rough terrain. This system consists of two sub-systems: an environment recognition system using a self-organizing map and an adjusted control system using a neural network. In this paper, we propose a new controller design method based on a neural network. The proposed method involves three kinds of controllers: an elementary controller, adjusted controllers, and simplified controllers. In the experiments, our proposed method results in less oscillatory motion in rough terrain and performs better than a well tuned PID controller does.

2P2-D15 車輪型移動ロボットのための環境認識システム : 第2報 : 環境に応じた制御器の選択と未学習環境に対する環境認識性能(車輪移動ロボット)

Recently, various mechanisms have been developed combining linkage mechanisms and wheels. Especially passive linkage mechanisms and small wheel type robots are proposed, because a wheel type mobile mechanism has difficulty on the rough terrain movement. In our research, a 6-wheeled mobile robot employing the linkage mechanism has been developed to enhance maneuverability, and achieved climbing over a 0.20[m] height of bump. We designed controller using neural network for high energy efficiency. This controller has same performance with PID. In this paper, we propose environment recognition system for wheel type mobile robot on rough terrain environment. This system consists of multiple classification analyses. We compared with some methods.